ABC/079
Government of Islamic Republic of Afghanistan
Afghanistan National Standard Authority
Afghan Structural Code
ASC
A
BC
All rights reserved
AFGHANISTAN BUILDING CODE
2012
0 / 496
AFGHAN STRUCTURAL CODE
(ASC)
2012
KABUL / AFGHANISTAN
AFGHAN NATIONAL STANDARDS AUTHORITY
All rights reserved
1 / 496
TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION
SECTION 101 GENERAL
SECTION 102 CONSTRUCTION DOCUMENTS
SECTION 103 DRAWINGS, SPECIFICATIONS AND INSPECTION
CHAPTER 2 DEFINITIONS
SECTION 201 –ASECTION 202 –BSECTION 203 –CSECTION 204 –DSECTION 205 –ESECTION 206 –FSECTION 207 –GSECTION 208 –HSECTION 209 –ISECTION 210 –JSECTION 211 –LSECTION 212 –MSECTION 213 –NSECTION 214 –OSECTION 215 –PSECTION 216 –RSECTION 217 –SSECTION 218 –TSECTION 219 –VSECTION 220 –WSECTION 221 –YCHAPTER 3 STRUCTURAL DESIGN
SECTION 301 INTRODUCTION
SECTION 302 LOAD COMBINATIONS
SECTION 303 BLANK
SECTION 304 STRUCTURAL INTEGRITY
SECTION 305 CLASSIFICATION OF BUILDINGS AND OTHER STRUCTURES
SECTION 306 DEAD LOADS
SECTION 307 LIVE LOADS
SECTION 308 SNOW LOADS
SECTION 309 WIND LOADS
SECTION 310 RAIN LOADS
SECTION 311 EARTHQUAKE LOADS
SECTION 312. SOIL LATERAL LOADS
CHAPTER 4 SOILS AND FOUNDATIONS
SECTION 401 GENERAL
SECTION 402 GEOTECHNICAL INVESTIGATIONS
SECTION 403 EXCAVATION, GRADING AND FILL
SECTION 404 DAMPPROOFING AND WATERPROOFING
SECTION 405 PRESUMPTIVE LOAD-BEARING VALUES OF SOILS
SECTION 406 FOUNDATION WALLS, RETAINING WALLS AND EMBEDDED POSTS AND POLES
SECTION 407 FOUNDATIONS
SECTION 408 SHALLOW FOUNDATIONS
All rights reserved
2 / 496
SECTION 409 DEEP FOUNDATIONS
CHAPTER 5 CONCRETE
SECTION 501 GENERAL
SECTION 502 SPECIFICATIONS FOR TESTS AND MATERIALS
SECTION 503 DURABILITY REQUIREMENTS
SECTION 504 CONCRETE QUALITY, MIXING AND PLACING
SECTION 505 FORMWORK, EMBEDDED PIPES AND CONSTRUCTION JOINTS
SECTION 506 DETAILS OF REINFORCEMENT
SECTION 507 STRUCTURAL PLAIN CONCRETE
SECTION 508 MINIMUM SLAB PROVISIONS
SECTION 509 ANCHORAGE TO CONCRETE-ALLOWABLE STRESS DESIGN
SECTION 510 ANCHORAGE TO CONCRETE-STRENGTH DESIGN
SECTION 511 MATERIALS
SECTION 512 ANALYSIS AND DESIGN – GENERAL CONSIDERATIONS
SECTION 513 STRENGTH AND SERVICEABILITY
SECTION 514 FLEXURE AND AXIAL LOADS
SECTION 515 SHEAR AND TORSION
SECTION 516 DEVELOPMENT AND SPLICES OF REINFORCEMENT
SECTION 517 TWO-WAY SLAB SYSTEMS
SECTION 518 WALLS
SECTION 519 FOOTINGS
SECTION 520 PRECAST CONCRETE
SECTION 521 EARTHQUAKE RESISTANT STRUCTURES
SECTION 522 DIRECT DESIGN METHOD
SECTION 523 EQUIVALENT FRAME METHOD
SECTION 524 COMPOSITE CONCRETE FLEXURAL MEMBERS
CHAPTER 6 STEEL
SECTION 601 GENERAL
SECTION 602 IDENTIFICATION AND PROTECTION OF STEEL FOR STRUCTURAL PURPOSES
SECTION 603 CONNECTIONS
SECTION 604 STRUCTURAL STEEL
SECTION 605 STEEL JOISTS
SECTION 606 STEEL CABLE STRUCTURES
SECTION 607 COLD-FORMED STEEL LIGHT-FRAME CONSTRUCTION
CHAPTER 7 MASONRY
SECTION 701 GENERAL
SECTION 702 NOTATIONS
SECTION 703 MASONRY CONSTRUCTION MATERIALS
SECTION 704 CONSTRUCTION
SECTION 705 QUALITY ASSURANCE
SECTION 706 SEISMIC DESIGN
SECTION 707 ALLOWABLE STRESS DESIGN
SECTION 708 STRENGTH DESIGN OF MASONRY
SECTION 709 EMPIRICAL DESIGN OF MASONRY
SECTION 710 MASONRY CHIMNEYS
CHAPTER 8 WOOD
SECTION 801 GENERAL
SECTION 802 MINIMUM STANDARD AND QUANTITY
SECTION 803 GENERAL CONSTRUCTION REQUIREMENTS
All rights reserved
3 / 496
SECTION 804 GENERAL DESIGN REQUIREMENTS FOR LATERA-FORCE-RESISTING SYSTEMS
SECTION 805 ALLOWABLE STRESS DESIGN
SECTION 806 LOAD RESISTANCE FACTOR DESIGN
CHAPTER 9 STRUCTURAL TESTS & EVALUATION OF EXISTING STRUCTURES
SECTION 901 GENERAL
SECTION 902 APPROVALS
SECTION 903 SPECIAL INSPECTIONS
SECTION 904 STATEMENT OF SPECIAL INSPECTIONS
SECTION 905 SPECIAL INSPECTIONS FOR WIND REQUIREMENTS
SECTION 906 SPECIAL INSPECTIONS FOR SEISMIC RESISTANCE
SECTION 907 STRUCTURAL TESTING FOR SEISMIC RESISTANCE
SECTION 908 CONTRACTOR RESPONSIBILITY
SECTION 909 STRUCTURAL OBSERVATIONS
SECTION 910 DESIGN STRENGTH OF MATERIALS
SECTION 911 ALTERNATIVE TEST PROCEDURE
SECTION 912 TEST SAFE LOAD
SECTION 913 IN-SITU LOAD TESTS
SECTION 914 EXISTING BUILDING PROVISIONS
SECTION 915 STRENGTH EVALUATION OF EXISTING STRUCTURES
APPENDIX A GRADING
SECTION A101 GENERAL
SECTION A102 PERMITS REQUIRED
SECTION A103 PERMIT APPLICATION AND SUBMITTALS
SECTION A104 INSPECTIONS
SECTION A105 EXCAVATIONS
SECTION A106 FILLS
SECTION A107 SETBACKS
SECTION A108 DRAINAGE AND TERRACING
SECTION A109 EROSION CONTROL
APPENDIX B ANCHORING TO CONCRETE
SECTION B101 SCOPE
SECTION B102 GENERAL REQUIREMENTS
SECTION B103 GENERAL REQUIREMENTS FOR STRENGTH OF ANCHORS
SECTION B104 DESIGN REQUIREMENTS FOR TENSILE LOADING
SECTION B105 DESIGN REQUIREMENTS FOR SHEAR LOADING
SECTION B106 INTERACTION OF TENSILE AND SHEAR FORCES
SECTION B107 REQUIRED EDGE DISTANCES, SPACINGS, AND THICKNESS TO PRECLUDE
SECTION B108 INSTALLATION OF ANCHORS
All rights reserved
4 / 496
CHAPTER 1
INTRODUCTION
SECTION 101 GENERAL
101.1 SCOPE
The provisions of this Code provide minimum requirements for design and construction of structural
concrete, steel, masonary and wood members of any structure including the foundations. Loads and
appropriate load combinations, which have been developed to be used together for concrete, steel,
masonry, wood structures are set forth for strength design and allowable stress design. For design
strengths and allowable stress limits, design specifications for conventional structural materials used in
buildings and modifications contained in this Code shall be followed.
101.2 ASC (Afghan Structural Code) shall govern in all matters pertaining to design, construction, and
material properties wherever it is in conflict with requirements contained in other standards
referenced herein.
101.3 The design and construction of cast-in-place footings, foundation walls, and slabs-on-ground in
accordance with ASC (Afghan Structural Code) shall be permitted.
101.4 For unusual structures, such as arches, bins and silos, blast-resistant structures, and chimneys,
provisions of ASC (Afghan Structural Code) shall govern where applicable.
101.5 ASC (Afghan Structural Code) does not govern design and installation of portions of concrete
piles, drilled piers, and caissons embedded in ground except for structures assigned to Seismic Design
Categories D, E, and F. See 521.12.4 for requirements for concrete piles, drilled piers, and caissons in
structures assigned to Seismic Design Categories D, E, and F.
101.6 Provisions for earthquake resistance
101.6.1 The seismic design category of a structure shall be determined in accordance with this
standard, or determined by other authority having jurisdiction in areas without a legally adopted
building code.
101.6.2 All structures shall satisfy the applicable provisions of Section 521 except those assigned
to Seismic Design Category A and those otherwise exempted by the legally adopted general
building code. See Section 521.1.1.
SECTION 102 CONSTRUCTION DOCUMENTS
Refer to the Administrative Document for this article.
102.1 Floor live load. The uniformly distributed, concentrated and impact floor live load used in the
design shall be indicated for floor areas. Use of live load reduction in accordance with Section 307.9
shall be indicated for each type of live load used in the design.
102.2 Roof live load. The roof live load used in the design shall be indicated for roof areas Section
307.11.
102.3 Roof snow load. The ground snow load, Pg, shall be indicated. In areas where the ground snow
load, Pg, exceeds 0.50 kN/m2, the following additional information shall also be provided,
regardless of whether snow loads govern the design of the roof:
1. Flat-roof snow load, Pf.
All rights reserved
5 / 496
2. Snow exposure factor, Ce.
3. Snow load importance factor, I.
4. Thermal factor, Ct.
102.4 Wind design data. The following information related to wind loads shall be shown, regardless of
whether wind loads govern the design of the lateral-force-resisting system of the building:
1. Basic wind speed (3-second gust), kilometers per hour (km/hr).
2. Wind importance factor, I, and occupancy category.
3. Wind exposure. Where more than one wind exposure is utilized, the wind exposure and
applicable wind direction shall be indicated.
4. The applicable internal pressure coefficient.
5. Components and cladding. The design wind pressures in terms of (kN/m2) to be used for the
design of exterior component and cladding materials not specifically designed by the
registered design professional.
102.5 Earthquake design data. The following information related to seismic loads shall be shown,
regardless of whether seismic loads govern the design of the lateral-force-resisting system of the
building:
1. Seismic importance factor, I, and occupancy category.
2. Mapped spectral response accelerations, SS and S1.
3. Site class.
4. Spectral response coefficients, SDS and SD1.
5. Seismic design category.
6. Basic seismic-force-resisting system(s).
7. Design base shear.
8. Seismic response coefficient(s), CS.
9. Response modification factor(s), R.
10. Analysis procedure used.
102.6 Geotechnical information. The design loadbearing values of soils shall be shown on the
construction documents.
102.7 Special loads. Special loads that are applicable to the design of the building, structure or
portions thereof shall be indicated along with the specified section of this code that addresses the
special loading condition.
102.8 Systems and components requiring special inspections for seismic resistance. Construction
documents or specifications shall be prepared for those systems and components requiring special
inspection for seismic resistance as specified in Section 906.1 by the registered design professional
responsible for their design and shall be submitted for approval in accordance with Section 906.1
Reference to seismic standards in lieu of detailed drawings is acceptable.
SECTION 103 DRAWINGS, SPECIFICATIONS AND INSPECTION
103.1 DRAWINGS AND SPECIFICATIONS
103.1.1. Copies of design drawings, typical details, and specifications for all structural concrete
construction shall bear the seal of a licensed design professional. These drawings, details, and
specifications shall show:
(a) Name and date of issue of code and supplement to which design conforms,
(b) Live load and other loads used in design,
(c) Specified compressive strength of concrete at stated ages or stages of construction for
which each
All rights reserved
6 / 496
part of structure is designed,
(d) Specified strength or grade of reinforcement,
(e) Size and location of all structural elements, reinforcement, and anchors,
(f) Provision for dimensional changes resulting from creep, shrinkage, and temperature,
(g) Magnitude and location of prestressing forces,
(h) Anchorage length of reinforcement and location and length of lap splices,
(i) Type and location of mechanical and welded splices of reinforcement,
(j) Details and location of all contraction or isolation joints specified for structural plain
concrete in Section 507,
(k) Minimum concrete compressive strength at time of post-tensioning,
(l) Stressing sequence for post-tensioning tendons,
(m) Statement if slab-on-ground is designed as a structural diaphragm, see Section
521.12.3.4.
103.1.2. Calculations pertinent to design shall be filed with the drawings when required by the
building official. Analysis and designs using computer programs shall be permitted provided
design assumptions, user input, and computer-generated output are submitted. Model analysis
shall be permitted to supplement calculations.
103.2. INSPECTION
103.2.1. Concrete construction shall be inspected as required by the general building codes. In
the absence of such inspection requirements, construction shall be inspected throughout the
various Work stages by or under the supervision of a licensed design professional or by a
qualified inspector.
103.2.2. Refer to the Administrative Document for this article.
103.2.3. When the ambient temperature falls below 4 °C or rises above 35 °C a record shall be
kept of concrete temperatures and of protection given to concrete during placement and curing.
103.2.4. Records of inspection required in this code shall be preserved by the inspecting
engineer or architect for 2 years after completion of the project.
103.2.5. For special moment frames designed in accordance with Section 521, continuous
inspection of the placement of the reinforcement and concrete shall be made by a qualified
inspector. The inspector shall be under the supervision of the licensed design professional
responsible for the structural design or under the supervision of a licensed design professional
with demonstrated capability for supervising inspection of construction of special moment
frames.
103.2.6. Approval of special systems of design or construction
Refer to the Administrative Document for this article.
All rights reserved
7 / 496
CHAPTER 2
DEFINITIONS
The following words and terms shall have the meanings shown herein.
SECTION 201 -AAAC MASONRY: Masonry made of autoclaved aerated concrete (AAC) units, manufactured without
internal reinforcement and bonded together using thin- or thick-bed mortar.
ACCREDITATION BODY: Refer to the Administrative Document for this article.
ACTIVE FAULT: A fault determined to be active by the authority having jurisdiction from properly
substantiated data.
ADDITION: An increase in building area, aggregate floor area, height, or number of stories of a
structure.
ADMIXTURE: Material other than water, aggregate, or hydraulic cement, used as an ingredient of
concrete and added to concrete before or during its mixing to modify its properties.
ADOBE CONSTRUCTION: Construction in which the exterior load-bearing and nonload-bearing walls
and partitions are of unfired clay masonry units, and floors, roofs and interior framing are wholly or
partly of wood or other approved materials.
Adobe, stabilized: Unfired clay masonry units to which admixtures, such as emulsified asphalt, are
added during the manufacturing process to limit the units’ water absorption so as to increase their
durability.
Adobe, unstabilized: Unfired clay masonry units that do not meet the definition of “Adobe, stabilized.”
AGGREGATE: Granular material, such as sand, gravel, crushed stone, and iron blast-furnace slag, used
with a cementing medium to form a hydraulic cement concrete or mortar.
AGGREGATE, LEIGHTWEIGHT: Aggregate meeting the requirements of ASTM C330 and having a loose
bulk density of 1120 kg/m3 or less, determined in accordance with ASTM C 29.
ALLOWABLE STRESS DESIGN: A method of proportioning structural members such that elastically
computed stresses produced in the members by nominal loads do not exceed specified allowable
stresses (also called “working stress design”).
ALTERATION: Any construction or renovation to an existing structure other than an addition.
ANCHOR: Metal rod, wire or strap that secures masonry to its structural support.
APPENDAGE: An architectural component such as a canopy, marquee, ornamental balcony, or
statuary.
APPROVED: Acceptable to the authority having jurisdiction.
APPROVED AGENCY: Refer to the Administrative Document for this article.
APPROVED FABRICATOR: Refer to the Administrative Document for this article.
All rights reserved
8 / 496
APPROVAL: Refer to the Administrative Document for this article.
AREA:
Bedded: The area of the surface of a unit that is in contact with mortar in the plane of the joint.
Gross cross-sectional: The area delineated by the out-to- out specified dimensions of a unit in the
plane under consideration.
Net cross-sectional: The area of units, grout and mortar crossed by the plane under consideration
based on out-to-out specified dimensions.
ATTACHMENTS: Means by which nonstructural components or supports of nonstructural components
are secured or connected to the seismic force-resisting system of the structure. Such attachments
include anchor bolts, welded connections, and mechanical fasteners.
AUTHORITY HAVING JURISDICTION: Refer to the Administrative Document for this article.
AUTOCLAVED AERATED CONCRETE (AAC): Low-density cementitious product of calcium silicate
hydrates, whose material specifications are defined in ASTM C 1386.
SECTION 202 -BBASE: The level at which the horizontal seismic ground motions are considered to be imparted to the
structure.
BASE SHEAR: Total design lateral force or shear at the base.
BASE OF STRUCTURE: Level at which the horizontal earthquake ground motions are assumed to be
imparted to a building. This level does not necessarily coincide with the ground level. See Section 521.
BASIC WIND SPEED, V: Three-second gust speed at 10 m above the ground in Exposure C (See Section
309.6) as determined in accordance with Section 309.3.
BED JOINT: The horizontal layer of mortar on which a unit is laid.
BOND BEAM: A horizontal grouted element within masonry in which reinforcement is embedded.
BOUNDARY ELEMENTS: Diaphragm and shear wall boundary members to which the diaphragm
transfers forces. Boundary members include chords and drag struts at diaphragm and shear wall
perimeters, interior openings, discontinuities, and reentrant corners.
BOUNDARY MEMBERS: Portions along wall and diaphragm edges strengthened by longitudinal and
transverse reinforcement. Boundary members include chords and drag struts at diaphragm and shear
wall perimeters, interior openings, discontinuities, and reentrant corners.
BRACED WALL LINE: A series of braced wall panels in a single story.
BRACED WALL PANEL: A section of wall braced.
BRICK:
Calcium silicate (sand lime brick): A masonry unit made of sand and lime.
Clay or shale: A masonry unit made of clay or shale, usually formed into a rectangular prism while in
the plastic state and burned or fired in a kiln.
Concrete: A masonry unit having the approximate shape of a rectangular prism and composed of inert
aggregate particles embedded in a hardened cementitious matrix.
All rights reserved
9 / 496
BUILDINGS: Structures, usually enclosed by walls and a roof, constructed to provide support or shelter
for an intended occupancy.
BUILDING AND OTHER STRUCTURE, FLEXIBLE: Slender buildings and other structures that have a
fundamental natural frequency less than 1 Hz.
BUILDING, ENCLOSED: A building that does not comply with the requirements for open or partially
enclosed buildings.
BUILDING ENVELOPE: Cladding, roofing, exterior walls, glazing, door assemblies, window assemblies,
skylight assemblies, and other components enclosing the building.
BUILDING, LOW-RISE: Enclosed or partially enclosed buildings that comply with the following
conditions:
1. Mean roof height h less than or equal to 18 m.
2. Mean roof height h does not exceed least horizontal dimension.
BUILDING OFFICIAL: Refer to the Administrative Document for this article.
BUILDING, OPEN: A building having each wall at least 80 percent open. This condition is expressed for
each wall by the equation Ao ≥ 0.8 Ag
where
Ao = total area of openings in a wall that receives positive external pressure, in m2
Ag = the gross area of that wall in which Ao is identified, in m2
BUILDING, PARTIALLY ENCLOSED: A building that complies with both of the following conditions:
1. The total area of openings in a wall that receives positive external pressure exceeds the sum
of the areas of openings in the balance of the building envelope (walls and roof) by more than
10 percent.
2. The total area of openings in a wall that receives positive external pressure exceeds 0.37 m2 or
1 percent of the area of that wall, whichever is smaller, and the percentage of openings in the
balance of the building envelope does not exceed 20 percent. These conditions are expressed
by the following equations:
1. Ao > 1.10Aoi
2. Ao > 0.37 m2 or > 0.01Ag, whichever is smaller, and Aoi/Agi ≤ 0.20
where
Ao, Ag are as defined for Open Building
Aoi = the sum of the areas of openings in the building envelope (walls and roof) not including Ao, in m2
Agi = the sum of the gross surface areas of the building envelope(walls and roof) not including Ag, in m2
BUILDING OR OTHER STRUCTURE, REGULAR-SHAPED: A building or other structure having no unusual
geometrical irregularity in spatial form.
BUILDING OR OTHER STRUCTURES, RIGID: A building or other structure whose fundamental
frequency is greater than or equal to 1 Hz.
BUILDING, SIMPLE DIAPHRAGM: A building in which both windward and leeward wind loads are
transmitted by roof and vertically spanning wall assemblies, through continuous floor and roof
diaphragms, to the MWFRS (Main Wind-Force Resisting System).
All rights reserved
10 / 496
BUILDING, TORSIONALLY REGULAR UNDER WIND LOAD: A building with the MWFRS about each
principal axis proportioned so that the maximum displacement at each story under Case 2, the
torsional wind load case, of Fig. 309.15.3.7-6, does not exceed the maximum displacement at the same
location under Case 1 of Fig. 309.15.3.7-6, the basic wind load case.
SECTION 203 -CCANTILEVERED COLUMN SYSTEM: A seismic force-resisting system in which lateral forces are resisted
entirely by columns acting as cantilevers from the base.
CAST STONE: A building stone manufactured from portland cement concrete precast and used as a
trim, veneer or facing on or in buildings or structures.
CELL: A void space having a gross cross-sectional area greater than 1000 mm2.
CEMENTITIOUS MATERIALS: Materials as specified in Section 511, which have cementing value when
used in concrete either by themselves, such as portland cement, blended hydraulic cements, and
expansive cement, or such materials in combination with fly ash, other raw or calcined natural
pozzolans, silica fume, and/or ground granulated blast-furnace slag.
CERTIFICATE OF COMPLIANCE: A certificate stating that materials and products meet specified
standards or that workwas done in compliance with approved construction documents.
CHARACTERISTIC EARTHQUAKE: An earthquake assessed for an active fault having a magnitude equal
to the best estimate of the maximum magnitude capable of occurring on the fault, but not less than
the largest magnitude that has occurred historically on the fault.
CHIMNEY: A primarily vertical enclosure containing one or more passageways for conveying flue gases
to the outside atmosphere.
CHIMNEY TYPES:
High-heat appliance type: An approved chimney for removing the products of combustion from fuelburning, high-heat appliances producing combustion gases in excess of 1000°C measured at the
appliance flue outlet (See Section 710.12.3).
Low-heat appliance type: An approved chimney for removing the products of combustion from fuelburning, low-heat appliances producing combustion gases not in excess of 540°C under normal
operating conditions, but capable of producing combustion gases of 760°C during intermittent forces
firing for periods up to 1 hour. Temperatures shall be measured at the appliance flue outlet.
Masonry type: A field-constructed chimney of solid masonry units or stones.
Medium-heat appliance type: An approved chimney for removing the products of combustion from
fuel-burning, medium-heat appliances producing combustion gases not exceeding 1000°C measured at
the appliance flue outlet (See Section 710.12.2).
CLEANOUT: An opening to the bottom of a grout space of sufficient size and spacing to allow the
removal of debris.
COLLAR JOINT: Vertical longitudinal joint between wythes of masonry or between masonry and
backup construction that is permitted to be filled with mortar or grout.
COLLECTOR: A horizontal diaphragm element parallel and in line with the applied force that collects
and transfers diaphragm shear forces to the vertical elements of the lateral- force-resisting system
and/or distributes forces within the diaphragm.
All rights reserved
11 / 496
COLLECTOR ELEMENT: Element that acts in axial tension or compression to transmit earthquake
induced forces between a structural diaphragm and a vertical element of the seismic-force-resisting
system. See Section 521.
COLUMN: Member with a ratio of height-to-least lateral dimension exceeding 3 used primarily to
support axial compressive load. For a tapered member, the least lateral dimension is the average of
the top and bottom dimensions of the smaller side.
COMPONENTS AND CLADDING (C&C): Elements of the building envelope that do not qualify
as part of the MWFRS.
COMPONENT: A part of an architectural, electrical, or mechanical system.
Component, Nonstructural: A part of an architectural, mechanical, or electrical system within or
without a building or nonbuilding structure.
Component, Flexible: Nonstructural component having a fundamental period greater than 0.06 s.
Component, Rigid: Nonstructural component having a fundamental period less than or equal to 0.06 s.
COMPOSITE CONCRETE FLEXURAL MEMBERS: Concrete flexural members of precast or cast-in-place
concrete elements, or both, constructed in separate placements but so interconnected that all
elements respond to loads as a unit.
COMPRESSION-CONTROLLED SECTION: A cross section in which the net tensile strain in the extreme
tension steel at nominal strength is less than or equal to the compression-controlled strain limit.
COMPRESSION-CONTROLLED STRAIN LIMIT: The net tensile strain at balanced strain conditions. See
Section 514.3.3.
COMPRESSIVE STRENGTH OF MASONRY: Maximum compressive force resisted per unit of net crosssectional area of masonry, determined by the testing of masonry prisms or a function of individual
masonry units, mortar and grout.
CONCRETE, PLAIN: Concrete that is either unreinforced or contains less reinforcement than the
minimum amount specified in this code for reinforced concrete.
CONCRETE, REINFORCED: Concrete reinforced with no less reinforcement than the minimum amount
required by this code prestressed or nonprestressed, and designed on the assumption that the two
materials act together in resisting forces.
CONCRETE: Mixture of portland cement or any other hydraulic cement, fine aggregate, coarse
aggregate, and water, with or without admixtures.
CONCRETE, SPECIFIED COMPRESSIVE STRENGTH OF (f´c): Compressive strength of concrete used in
design and evaluated in accordance with provisions of Section 504, expressed in megapascals (MPa).
Whenever the quantity f´c is under a radical sign, square root of numerical value only is intended, and
result has units of megapascals (MPa).
CONNECTION: A region that joins two or more members. In Section 521, a connection also refers to a
region that joins members of which one or more is precast, for which the following more specific
definitions apply:
CONNECTOR: A mechanical device for securing two or more pieces, parts or members together,
including anchors, wall ties and fasteners.
All rights reserved
12 / 496
CONSTRUCTION DOCUMENTS: The written, graphic, electronic, and pictorial documents describing
the design, locations, and physical characteristics of the project required to verify compliance with this
standard.
CONTRACT DOCUMENTS: Documents, including the project drawings and project specifications,
covering the required Work.
CONTRACTION JOINT: Formed, sawed, or tooled groove in a concrete structure to create a weakened
plane and regulate the location of cracking resulting from the dimensional change of different parts of
the structure.
CONVENTIONAL LIGHT-FRAME CONSTRUCTION: A type of construction whose primary structural
elements areformed by a system of repetitive wood-framing members.
COUPLING BEAM: A beam that is used to connect adjacent concrete wall elements to make them act
together as a unit to resist lateral loads.
COVER: Distance between surface of reinforcing bar and edge of member.
COVER, SPECIFIED CONCRETE: The distance between the outermost surface of embedded
reinforcement and the closest outer surface of the concrete indicated on design drawings or in project
specifications.
CRIPPLEWALL: A framed stud wall extending from the top of the foundation to the underside of floor
framing for the lowest occupied floor level.
CROSSTIE: A continuous reinforcing bar having a seismic hook at one end and a hook not less than
90 degrees with at least a six-diameter extension at the other end. The hooks shall engage peripheral
longitudinal bars. The 90-degree hooks of two successive crossties engaging the same longitudinal bars
shall be alternated end for end. See Sections 506 and 521.
CURVE FRICTION: Friction resulting from bends or curves in the specified prestressing tendon profile.
SECTION 204 -DDEAD LOADS: The weight of materials of construction incorporated into the building, including but not
limited to walls, floors, roofs, ceilings, stairways, built-in partitions, finishes, cladding and other
similarly incorporated architectural and structural items, and the weight of fixed service equipment,
such as cranes, plumbing stacks and risers, electrical feeders, heating, ventilating and air-conditioning
systems and automatic sprinkler systems.
DEEP FOUNDATION: A deep foundation is a foundation element that does not satisfy the definition of
a shallowfoundation.
DEFORMABILITY: The ratio of the ultimate deformation to the limit deformation.
High-Deformability Element: An element whose deformability is not less than 3.5 where subjected to
four fully reversed cycles at the limit deformation.
Limited-Deformability Element: An element that is neither a low-deformability nor a highdeformability element.
Low-Deformability Element: An element whose deformability is 1.5 or less.
All rights reserved
13 / 496
DEFORMATION:
Limit Deformation: Two times the initial deformation that occurs at a load equal to 40 percent of the
maximum strength.
Ultimate Deformation: The deformation at which failure occurs and that shall be deemed to occur if
the sustainable load reduces to 80 percent or less of the maximum strength.
DEFORMED REINFORCEMENT: Deformed reinforcing bars, bar mats, deformed wire, and welded wire
reinforcement conforming to Section 511.5.3.
DESIGNATED SEISMIC SYSTEMS: Those nonstructural components that require design and for which
the component importance factor, Ip, is greater than 1.0.
DESIGN DISPLACEMENT: Total lateral displacement expected for the design-basis earthquake, as
required by the governing code for earthquake-resistant design. See Section 521.
DESIGN EARTHQUAKE: The earthquake effects that are two-thirds of the corresponding Maximum
Considered Earthquake (MCER) effects.
DESIGN EARTHQUAKE GROUND MOTION: The earthquake ground motions that are two-thirds of the
corresponding MCER ground motions.
DESIGN FORCE, F: Equivalent static force to be used in the determination of wind loads for other
structures.
DESIGN LOAD COMBINATION: Combination of factored loads and forces in Section 513.2.
DESIGN PRESSURE, p: Equivalent static pressure to be used in the determination of wind loads for
buildings.
DESIGN STRENGTH: The product of the nominal strength and a resistance factor.
DESIGN STORY DRIFT RATIO: Relative difference of design displacement between the top and bottom
of a story, divided by the story height. See Section 521.
DEVELOPMENT LENGTH: Length of embedded reinforcement, including pretensioned strand, required
to develop the design strength of reinforcement at a critical section. See Section 513.3.3.
DIAPHRAGM, UNBLOCKED: A diaphragm that has edge nailing at supporting members only. Blocking
between supporting structural members at panel edges is not included. Diaphragm panels are field
nailed to supporting members.
DIAPHRAGM: Roof, floor, or other membrane or bracing system acting to transfer the lateral forces
to the vertical resisting elements.
DIAPHRAGM BOUNDARY: A location where shear is transferred into or out of the diaphragm element.
Transfer is either to a boundary element or to another force-resisting element.
DIAPHRAGM CHORD: A diaphragm boundary element perpendicular to the applied load that is
assumed to take axial stresses due to the diaphragm moment.
DIMENSIONS:
Actual: The measured dimension of a unit or element.
All rights reserved
14 / 496
Nominal: The specified dimension plus an allowance for the joints with which the units are to be laid.
Thickness is given first, followed by height and then length.
Specified: The dimensions specified for the manufacture or construction of units, joints or any other
component of a structure.
DRILLED SHAFT: A drilled shaft is a cast-in-place deep foundation element constructed by drilling a
hole (with or without permanent casing) into soil or rock and filling it with fluid concrete.
DRILLED SHAFT, SOCKETED: A socketed drilled shaft is a drilled shaft with a permanent pipe or tube
casing that extends down to bedrock and an uncased socket drilled into the bedrock.
DIRECTIONAL PROCEDURE: A procedure for determining wind loads on buildings and other structures
for specific wind directions, in which the external pressure coefficients utilized are based on past wind
tunnel testing of prototypical building models for the corresponding direction of wind.
DRAG STRUT (COLLECTOR, TIE, DIAPHRAGM STRUT): A diaphragm or shear wall boundary element
parallel to the applied load that collects and transfers diaphragm shear forces to the vertical forceresisting elements or distributes forces within the diaphragm or shear wall.
DROP PANEL: A projection below the slab used to reduce the amount of negative reinforcement over
a column or the minimum required slab thickness, and to increase the slab shear strength. See Section
517.2.5 and 517.3.7.
DUCT: A conduit (plain or corrugated) to accommodate prestressing steel for post-tensioned
installation.
DUCTILE CONNECTION: Connection that experiences yielding as a result of the earthquake design
displacements.
DURATION OF LOAD: The period of continuous application of a given load, or the aggregate of periods
of intermittent applications of the same load.
SECTION 205 -EEAVE HEIGHT, he: The distance from the ground surface adjacent to the building to the roof eave line
at a particular wall. If the height of the eave varies along the wall, the average height shall be used.
EFFECTIVE DEPTH OF SECTION: Distance measured from extreme compression fiber to centroid of
longitudinal tension reinforcement.
EFFECTIVE PRESTRESS: Stress remaining in prestressing steel after all losses have occurred.
EFFECTIVE WIND AREA, A: The area used to determine (GCp). For component and cladding elements,
the effective wind area is the span length multiplied by an effective width that need not be less than
one-third the span length. For cladding fasteners, the effective wind area shall not be greater than the
area that is tributary to an individual fastener.
EMBEDMENT LENGTH: Length of embedded reinforcement provided beyond a critical section.
ENCLOSURE: An interior space surrounded by walls.
ENVELOPE PROCEDURE: A procedure for determining wind load cases on buildings, in which pseudoexternal pressure coefficients are derived from past wind tunnel testing of prototypical building
All rights reserved
15 / 496
models successively rotated through 360 degrees, such that the pseudo-pressure cases produce key
structural actions (uplift, horizontal shear, bending moments, etc.) that envelop their maximum values
among all possible wind directions.
EQUIPMENT SUPPORT: Those structural members or assemblies of members or manufactured
elements, including braces, frames, legs, lugs, snuggers, hangers, or saddles that transmit gravity loads
and operating loads between the equipment and the structure.
ESSENTIAL FACILITIES: Buildings and other structures that are intended to remain operational in the
event of extreme environmental loading from fl ood, wind, snow, or earthquakes.
ESCARPMENT: Also known as scarp, with respect to topographic effects in Section 309.11, a cliff or
steep slope generally separating two levels or gently sloping areas (See Figure 309.11.1-1)
EXTREME TENSION STEEL: The reinforcement (prestressed or nonprestressed) that is the farthest from
the extreme compression fiber.
SECTION 206 -FFABRICATED ITEM: Structural, load-bearing or lateral load-resisting assemblies consisting of materials
assembled prior to installation in a building or structure, or subjected to operations such as heat
treatment, thermal cutting, cold working or reforming after manufacture and prior to installation in a
building or structure. Materials produced in accordance with standard specifications referenced by
this code, such as rolled structural steel shapes, steel-reinforcing bars, masonry units, and wood
structural panels or in accordance with a standard, listed in AAC (Afghan Architectural Code), which
provides requirements for quality control done under the supervision of a third-party quality control
agency shall not be considered “fabricated items.”
FABRIC PARTITION: A partition consisting of a finished surface made of fabric, without a continuous
rigid backing, that is directly attached to a framing system in which the vertical framing members are
spaced greater than 1200 mm on center.
FACTORED LOAD: The product of the nominal load and a load factor.
FIBERBOARD: A fibrous, homogeneous panel made from lignocellulosic fibers (usually wood or cane)
and having a density of less than 500 kg/m3 but more than 160 kg/m3.
FIREPLACE: A hearth and fire chamber or similar prepared place in which a fire may be made and
which is built in conjunction with a chimney.
FIREPLACE THROAT: The opening between the top of the firebox and the smoke chamber.
FIXED LADDER: A ladder that is permanently attached to a structure, building, or equipment.
FLEXIBLE CONNECTIONS: Those connections between equipment components that permit rotational
and/or translational movement without degradation of performance. Examples include universal
joints, bellows expansion joints, and flexible metal hose.
FOUNDATION PIER: An isolated vertical foundation member whose horizontal dimension measured at
right angles to its thickness does not exceed three times its thickness and whose height is equal to or
less than four times its thickness.
All rights reserved
16 / 496
FRAME:
Braced Frame: An essentially vertical truss, or its equivalent, of the concentric or eccentric type that is
provided in a building frame system or dual system to resist seismic forces.
Concentrically Braced Frame (CBF): A braced frame in which the members are subjected primarily to
axial forces. CBFs are categorized as ordinary concentrically braced frames (OCBFs) or special
concentrically braced frames (SCBFs).
Eccentrically Braced Frame (EBF): A diagonally braced frame in which at least one end of each brace
frames into a beam a short distance from a beam-column or from another diagonal brace.
Moment Frame: A frame in which members and joints resist lateral forces by flexure as well as along
the axis of the members. Moment frames are categorized as intermediate moment frames (IMF),
ordinary moment frames (OMF), and special moment frames (SMF).
Structural System:
Building Frame System: A structural system with an essentially complete space frame providing
support for vertical loads. Seismic force resistance is provided by shear walls or braced frames.
Dual System: A structural system with an essentially complete space frame providing support for
vertical loads. Seismic force resistance is provided by moment-resisting frames and shear walls or
braced frames as prescribed in Section 311.6.2.5.1.
Shear Wall-Frame Interactive System: A structural system that uses combinations of ordinary
reinforced concrete shear walls and ordinary reinforced concrete moment frames designed to resist
lateral forces in proportion to their rigidities considering interaction between shear walls and frames
on all levels.
Space Frame System: A 3-D structural system composed of interconnected members, other than
bearing walls, that is capable of supporting vertical loads and, where designed for such an application,
is capable of providing resistance to seismic forces.
FREE ROOF: Roof with a configuration generally conforming to those shown in Figures 309.15.3.7-2
through 309.15.3.7-4 (monoslope, pitched, or troughed) in an open building with no enclosing walls
underneath the roof surface.
FRICTION CLIP: A device that relies on friction to resist applied loads in one or more directions to
anchor a nonstructural component. Friction is provided mechanically and is not due to gravity loads.
SECTION 207 -GGLAZED CURTAIN WALL: A nonbearing wall that extends beyond the edges of building floor slabs, and
includes a glazing material installed in the curtain wall framing.
GLAZED STOREFRONT: A nonbearing wall that is installed between floor slabs, typically including
entrances, and includes a glazing material installed in the storefront framing.
GLAZING: Glass or transparent or translucent plastic sheet used in windows, doors, skylights, or
curtain walls.
GLAZING, IMPACT RESISTANT: Glazing that has been shown by testing to withstand the impact of test
missiles.
All rights reserved
17 / 496
GLUED BUILT-UP MEMBER: A structural element, the section of which is composed of built-up lumber,
wood structural panels orwood structural panels in combination with lumber, all parts bonded
together with structural adhesives.
GRAB BAR SYSTEM: A bar and associated anchorages and attachments to the structural system, for
the support of body weight in locations such as toilets, showers, and tub enclosures.
GRADE (LUMBER): The classification of lumber in regard to strength and utility in accordance with
American Softwood Lumber Standard DOC PS 20 and the grading rules of an approved lumber ruleswriting agency.
GRADE PLANE: A horizontal reference plane representing the average of finished ground level
adjoining the structure at all exterior walls. Where the finished ground level slopes away from the
exterior walls, the grade plane is established by the lowest points within the area between the
structure and the property line or, where the property line is more than 1,800 mm from the structure,
between the structure and points 1,800 mm from the structure.
GROUTED MASONRY:
Grouted hollow-unit masonry. That form of grouted masonry construction in which certain
designated cells of hollow units are continuously filled with grout.
Grouted multiwythe masonry. That form of grouted masonry construction in which the space
between the wythes is solidly or periodically filled with grout.
GUARDRAIL SYSTEM: A system of components, including anchorages and attachments to the
structural system, near open sides of an elevated surface for the purpose of minimizing the possibility
of a fall from the elevated surface by people, equipment, or material.
SECTION 208 -HHANDRAIL SYSTEM: A rail grasped by hand for guidance and support, and associated anchorages and
attachments to the structural system.
HARDBOARD: A fibrous-felted, homogeneous panel made from lignocellulosic fibers consolidated
under heat and pressure in a hot press to a density not less than 500 kg/m3.
HIGHLY TOXIC SUBSTANCE: As defined in 29 CFR 1910.1200 Appendix A with Amendments as of
February 1, 2000.
HEAD JOINT: Vertical mortar joint placed between masonry units within the wythe at the time the
masonry units are laid.
HEADED DEFORMED BARS: Deformed reinforcing bars with heads attached at one or both ends.
Heads are attached to the bar end by means such as welding or forging onto the bar, internal threads
on the head mating to threads on the bar end, or a separate threaded nut to secure the head of the
bar. The net bearing area of headed deformed bar equals the gross area of the head minus the larger
of the area of the bar and the area of any obstruction.
HEADED SHEAR STUD REINFORCEMENT: Reinforcement consisting of individual headed studs, or
groups of studs, with anchorage provided by a head at each end or by a common base rail consisting of
a steel plate or shape.
All rights reserved
18 / 496
HELICAL PILE: Manufactured steel deep foundation element consisting of a central shaft and one or
more helical bearing plates. A helical pile is installed by rotating it into the ground. Each helical bearing
plate is formed into a screwthread with a uniform defined pitch.
HELIPAD: A structural surface that is used for landing, taking off, taxiing, and parking of helicopters.
HEIGHT,WALLS: The vertical distance from the foundation wall or other immediate support of such
wall to the top of the wall.
HILL: With respect to topographic effects in Section 309.11, a land surface characterized by strong
relief in any horizontal direction (See Figure 309.11.1-1).
HOOP: A closed tie or continuously wound tie. A closed tie can be made up of several reinforcement
elements each having seismic hooks at both ends. A continuously wound tie shall have a seismic hook
at both ends. See Section 521.
SECTION 209 -IIMPACT LOAD: The load resulting from moving machinery, elevators, craneways, vehicles and other
similar forces and kinetic loads, pressure and possible surcharge from fixed or moving loads.
IMPACT PROTECTIVE SYSTEM: Construction that has been shown by testing to withstand the impact
of test missiles and that is applied, attached, or locked over exterior glazing.
IMPORTANCE FACTOR: A factor that accounts for the degree of risk to human life, health, and welfare
associated with damage to property or loss of use or functionality.
INSPECTION CERTIFICATE: Refer to the Administrative Document for this article.
INSPECTION, SPECIAL: The observation of the work by a special inspector to determine compliance
with the approved construction documents and these standards in accordance with the quality
assurance plan.
Continuous Special Inspection: The full-time observation of the work by a special inspector who is
present in the area where work is being performed.
Periodic Special Inspection: The part-time or intermittent observation of the work by a special
inspector who is present in the area where work has been or is being performed.
INSPECTOR, SPECIAL (who shall be identified as the owner’s inspector): A person approved by the
authority having jurisdiction to perform special inspection.
INTERMEDIATE MOMENT FRAME A cast-in-place frame complying with the requirements of Section
521.3 in addition to the requirements for ordinary moment frames.
INTERMEDIATE PRECAST STRUCTURAL WALL: A wall complying with all applicable requirements of
this code.
INTUMESCENT FIRE-RESISTANT COATINGS: Thin film liquid mixture applied to substrates by brush,
roller, spray or trowel which expands into a protective foamed layer to provide fire-resistant
protection of the substrates when exposed to flame or intense heat.
INVERTED PENDULUM-TYPE STRUCTURES: Structures in which more than 50 percent of the
structure’s mass is concentrated at the top of a slender, cantilevered structure and in which stability of
the mass at the top of the structure relies on rotational restraint to the top of the cantilevered
element.
All rights reserved
19 / 496
ISOLATION JOINT: A separation between adjoining parts of a concrete structure, usually a vertical
plane, at a designed location such as to interfere least with performance of the structure, yet such as
to allow relative movement in three directions and avoid formation of cracks elsewhere in the
concrete and through which all or part of the bonded reinforcement is interrupted.
SECTION 210 -JJOINT: The geometric volume common to intersecting members.
SECTION 211. -LLICENSED DESIGN PROFESSIONAL: Refer to the Administrative Document for this article.
LIGHT-FRAME CONSTRUCTION: A method of construction where the structural assemblies (e.g., walls,
floors, ceilings, and roofs) are primarily formed by a system of repetitive wood or cold-formed steel
framing members or subassemblies of these members (e.g., trusses).
LIMIT STATE: A condition beyond which a structure or member becomes unfit for service and is judged
either to be no longer useful for its intended function (serviceability limit state) or to be unsafe
(strength limit state).
LIVE LOADS: Those loads produced by the use and occupancy of the building or other structure and do
not include construction or environmental loads such as wind load, snow load, rain load, earthquake
load, flood load or dead load.
LIVE LOADS (ROOF): Those loads produced (1) during maintenance by workers, equipment and
materials; and (2) during the life of the structure by movable objects such as planters and by people.
LOAD AND RESISTANCE FACTOR DESIGN (LRFD): A method of proportioning structural members and
their connections using load and resistance factors such that no applicable limit state is reached when
the structure is subjected to appropriate load combinations. The term “LRFD” is used in the design of
steel and wood structures.
LOAD, DEAD: Dead weight supported by a member, as defined by general building code of which this
Code forms a part (without load factors).
LOAD EFFECTS: Forces and deformations produced in structural members by the applied loads.
LOAD FACTOR: A factor that accounts for deviations of the actual load from the nominal load, for
uncertainties in the analysis that transforms the load into a load effect, and for the probability that
more than one extreme load will occur simultaneously.
LOADS: Forces or other actions that result from the weight of all building materials, occupants and
their possessions, environmental effects, differential movement, and restrained dimensional changes.
Permanent loads are those loads in which variations over time are rare or of small magnitude. All
other loads are variable loads (see also “nominal loads”).
LONGITUDINAL REINFORCEMENT RATIO: Area of longitudinal reinforcement divided by the crosssectional area of the concrete.
All rights reserved
20 / 496
SECTION 212 -MMAIN WIND-FORCE RESISTING SYSTEM (MWFRS): An assemblage of structural elements assigned to
provide support and stability for the overall structure. The system generally receives wind loading
from more than one surface.
MASONRY: A built-up construction or combination of building units or materials of clay, shale,
concrete, glass, gypsum, stone or other approved units bonded together with or without mortar or
grout or other accepted methods of joining.
Ashlar masonry: Masonry composed of various-sized rectangular units having sawed, dressed or
squared bed surfaces, properly bonded and laid in mortar.
Coursed ashlar: Ashlar masonry laid in courses of stone of equal height for each course, although
different courses shall be permitted to be of varying height.
Glass unit masonry: Masonry composed of glass units bonded by mortar.
Plain masonry: Masonry in which the tensile resistance of the masonry is taken into consideration and
the effects of stresses in reinforcement are neglected.
Random ashlar: Ashlar masonry laid in courses of stone set without continuous joints and laid up
without drawn patterns. When composed of material cut into modular heights, discontinuous but
aligned horizontal joints are discernible.
Reinforced masonry: Masonry construction in which reinforcement acting in conjunction with the
masonry is used to resist forces.
Solid masonry: Masonry consisting of solid masonry units laid contiguously with the joints between
the units filled with mortar.
Unreinforced (plain) masonry: Masonry in which the tensile resistance of masonry is taken into
consideration and the resistance of the reinforcing steel, if present, is neglected.
MASONRY UNIT: Brick, tile, stone, glass block or concrete block conforming to the requirements
specified in Section 703.
Clay: A building unit larger in size than a brick, composed of burned clay, shale, fired clay or mixtures
thereof.
Concrete Block: A building unit or block larger in size than 300 mm by 100 mm by 100 mm made of
cement and suitable aggregates.
Hollow Block: A masonry unit whose net cross-sectional area in any plane parallel to the load-bearing
surface is less than 75 percent of its gross cross-sectional area measured in the same plane.
Solid: A masonry unit whose net cross-sectional area in every plane parallel to the load-bearing
surface is 75 percent or more of its gross cross-sectional area measured in the same plane.
MASTIC FIRE-RESISTANT COATINGS: Liquid mixture applied to a substrate by brush, roller, spray or
trowel that provides fire-resistant protection of a substrate when exposed to flame or intense heat.
MAXIMUM CONSIDERED EARTHQUAKE (MCE) GROUND MOTION: The most severe earthquake
effects considered by this standard more specifi cally defi ned in the following two terms.
MAXIMUM CONSIDERED EARTHQUAKE GEOMETRIC MEAN (MCEG) PEAK GROUND ACCELERATION:
The most severe earthquake effects considered by this standard determined for geometric mean peak
ground acceleration and without adjustment for targeted risk. The MCEG peak ground acceleration
adjusted for site effects (PGAM) is used in this standard for evaluation of liquefaction, lateral
spreading, seismic settlements, and other soil related issues. In this code, general procedures for
determining PGAM are provided in Section 311.5.3.
All rights reserved
21 / 496
MEAN ROOF HEIGHT, h: The average of the roof eave height and the height to the highest point on
the roof surface, except that, for roof angles of less than or equal to 10°, the mean roof height is
permitted to be taken as the roof eave height.
MECHANICALLY ANCHORED TANKS OR VESSELS: Tanks or vessels provided with mechanical
anchors to resist overturning moments.
MICROPILE: A micropile is a bored, grouted-in-place deep foundation element that develops its loadcarrying capacity by means of a bond zone in soil, bedrock or a combination of soil and bedrock.
MODULUS OF ELASTICITY: Ratio of normal stress to corresponding strain for tensile or compressive
stresses below proportional limit of material. See Section 512.5.
MOMENT FRAME: Frame in which members and joints resist forces through flexure, shear, and axial
force. Moment frames designated as part of the seismicforce- resisting system shall be categorized as
follows:
MORTAR: A plastic mixture of approved cementitious materials, fine aggregates and water used to
bond masonry or other structural units.
MORTAR, SURFACE-BONDING: A mixture to bond concrete masonry units that contains hydraulic
cement, glass fiber reinforcement with or without inorganic fillers or organic modifiers and water.
SECTION 213 -NNAILING, EDGE (BOUNDARY): A special nailing pattern required by design at the edges of each panel
within the assembly of a diaphragm or shear wall.
NAILING, FIELD: Nailing required between the sheathing panels and framing members at locations
other than boundary nailing and edge nailing.
NET TENSILE STRAIN: The tensile strain at nominal strength exclusive of strains due to effective
prestress, creep, shrinkage, and temperature.
NOMINAL LOADS: The magnitudes of the loads specifi ed in this standard for dead, live, soil, wind,
snow, rain, fl ood, and earthquake.
NOMINAL SIZE (LUMBER): The commercial size designation of width and depth, in standard sawn
lumber and glued-laminated lumber grades; somewhat larger than the standard net size of dressed
lumber, in accordance with DOCPS 20 for sawn lumber and with the AF&PA NDS for glued-laminated
lumber.
NOMINAL STRENGTH: The capacity of a structure or member to resist the effects of loads, as
determined by computations using specified material strengths and dimensions and formulas derived
from accepted principles of structural mechanics or by field tests or laboratory tests of scaled models,
allowing for modeling effects and differences between laboratory and fi eld conditions.
NONBUILDING STRUCTURE: A structure, other than a building, constructed of a type included in
Section 519 within the limits of 519.1.1.
NONBUILDING STRUCTURE SIMILAR TO A BUILDING: A nonbuilding structure that is designed and
constructed in a manner similar to buildings, will respond to strong ground motion in a fashion similar
All rights reserved
22 / 496
to buildings, and has a basic lateral and vertical seismic force-resisting system conforming to one of
the types indicated in Table 311.6.2.3.2-1.
SECTION 214 -OOCCUPANCY: The purpose for which a building or other structure, or part thereof, is used or intended
to be used.
OCCUPANCY CATEGORY: A category used to determine structural requirements based on occupancy.
OTHER STRUCTURES: Structures, other than buildings, for which loads are specified in this chapter.
ORDINARY MOMENT FRAME: A cast-in-place or precast concrete frame, and, in the case of ordinary
moment frames assigned to Seismic Design Category B, also complying with Section 521.2.
ORDINARY STRUCTURAL PLAIN CONCRETE WALL: A wall complying with the requirements of Section
507.
ORDINARY REINFORCED CONCRETE STRUCTURAL WALL: A wall complying with the requirements of
this code.
OTHER STRUCTURES: Structures, other than buildings, for which loads are specified in this standard.
ORTHOGONAL: To be in two horizontal directions, at 90° to each other.
OWNER: Any person, agent, firm, or corporation having a legal or equitable interest in the property.
OPENINGS: Apertures or holes in the building envelope that allow air to flow through the building
envelope and that are designed as “open” during design winds as defined by these provisions.
SECTION 215 -PP-DELTA EFFECT: The second order effect on shears and moments of frame members induced by axial
loads on a laterally displaced building frame.
PANEL (PARTOF A STRUCTURE): The section of a floor, wall or roof comprised between the supporting
frame of two adjacent rows of columns and girders or column bands of floor or roof construction.
PARTICLEBOARD: A generic term for a panel primarily composed of cellulosic materials (usually wood),
generally in the form of discrete pieces or particles, as distinguished from fibers. The cellulosic
material is combined with synthetic resin or other suitable bonding system by a process in which the
interparticle bond is created by the bonding system under heat and pressure.
PARTITION: A nonstructural interior wall that spans horizontally or vertically from support to support.
The supports may be the basic building frame, subsidiary structural members, or other portions of the
partition system.
PEDESTAL: Member with a ratio of height-to-least lateral dimension less than or equal to 3 used
primarily to support axial compressive load. For a tapered member, the least lateral dimension is the
average of the top and bottom dimensions of the smaller side.
PILE: Deep foundation element, which includes piers, caissons, and piles.
All rights reserved
23 / 496
PILE CAP: Foundation elements to which piles are connected including grade beams and mats.
PLAIN CONCRETE: Structural concrete with no reinforcement or with less reinforcement than the
minimum amount specified for reinforced concrete.
PLAIN REINFORCEMENT: Reinforcement that does not conform to definition of deformed
reinforcement. See Section 511.5.4.
Plastic hinge region: Length of frame element over which flexural yielding is intended to occur due to
earthquake design displacements, extending not less than a distance h from the critical section where
flexural yielding initiates. See Section 521.
PRECAST CONCRETE: Structural concrete element cast elsewhere than its final position in the
structure.
PREFABRICATED WOOD I-JOIST: Structural member manufactured using sawn or structural composite
lumber flanges and wood structural panel webs bonded together with exterior exposure adhesives,
which forms an “I” cross-sectional shape.
PRESTRESSED MASONRY: Masonry in which internal stresses have been introduced to counteract
potential tensile stresses in masonry resulting from applied loads.
PRINCIPAL ORTHOGONAL HORIZONTAL DIRECTIONS: The orthogonal directions that overlay the
majority of lateral force-resisting elements.
PRISM: An assemblage of masonry units and mortar with or without grout used as a test specimen for
determining properties of the masonry.
SECTION 216 -RRECOGNIZED LITERATURE: Published research findings and technical papers that are approved.
RIDGE: With respect to topographic effects in Section 309.11 an elongated crest of a hill characterized
by strong relief in two directions (see Figure 309.11.1-1).
REGISTERED DESIGN PROFESSIONAL: Refer to the Administrative Document for this article.
REINFORCEMENT: Material that conforms to Section 511.5, excluding prestressing steel unless
specifically included.
REINFORCED CONCRETE: Structural concrete reinforced with no less than the minimum amounts of
prestressing steel or nonprestressed reinforcement specified in this code.
RESISTANCE FACTOR: A factor that accounts for deviations of the actual strength from the nominal
strength and the manner and consequences of failure (also called “strength reduction factor”).
RESHORES: Shores placed snugly under a concrete slab or other structural member after the original
forms and shores have been removed from a larger area, thus requiring the new slab or structural
member to deflect and support its own weight and existing construction loads applied prior to the
installation of the reshores.
All rights reserved
24 / 496
RISK CATEGORY: A categorization of buildings and other structures for determination of flood, wind,
snow, ice and earthquake loads based on the risk associated with unacceptable performance. See
Table 305.1-1.
RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE
ACCELERATION: The most severe earthquake effects considered by this standard determined for the
orientation that results in the largest maximum response to horizontal ground motions and with
adjustment for targeted risk. In this standard, general procedures for determining the MCER Ground
Motion values are provided in Section 311.4.3.
RUBBLE MASONRY: Masonry composed of roughly shaped stones.
Coursed rubble: Masonry composed of roughly shaped stones fitting approximately on level beds and
well bonded.
Random rubble: Masonry composed of roughly shaped stones laid without regularity of coursing but
well bonded and fitted together to form well-divided joints.
Rough or ordinary rubble: Masonry composed of unsquared field stones laid without regularity of
coursing but well bonded.
RUNNING BOND: The placement of masonry units such that head joints in successive courses are
horizontally offset at least one-quarter the unit length.
ROOF LIVE LOAD: A load on a roof produced (1) during maintenance by workers, equipment, and
materials and (2) during the life of the structure by movable objects, such as planters or other similar
small decorative appurtenances that are not occupancy related.
SECTION 217 -SSCREEN ENCLOSURE: A building or part thereof, in whole or in part self-supporting, having walls and a
roof of insect or sun screening using fi berglass, aluminum, plastic, or similar lightweight netting
material, which enclose an occupancy or use such as outdoor swimming pools, patios or decks, and
horticultural and agricultural production facilities.
SEISMIC DESIGN CATEGORY: A classification assigned to a structure based on its occupancy category
and the severity of the design earthquake ground motion at the site, as defined by the legally adopted
general building code.
SEISMIC FORCES: The assumed forces prescribed herein, related to the response of the structure to
earthquake motions, to be used in the design of the structure and its components.
SEISMIC-FORCE-RESISTING SYSTEM: Portion of the structure designed to resist earthquake design
forces required by the legally adopted general building code using the applicable provisions and load
combinations.
SEISMIC HOOK: A hook on a stirrup, or crosstie having a bend not less than 135 degrees, except
that circular hoops shall have a bend not less than 90 degrees. Hooks shall have a 6db (but not less
than 75 mm) extension that engages the longitudinal reinforcement and projects into the interior of
the stirrup or hoop. See Sections 506.1.4 and 521.
SELF-ANCHORED TANKS OR VESSELS: Tanks or vessels that are stable under design overturning
moment without the need for mechanical anchors to resist uplift.
All rights reserved
25 / 496
SELF-STRAINING LOADS: Those loads produced by the internally exerted forces due to temperature
changes, shrinkage, creep, prestressing, lack of fit, relaxation, moisture change, differential settlement
and so on. Self-straining force can be applied to frame members or embedded bar elements.
SHALLOW FOUNDATION: A shallow foundation is an individual or strip footing, a mat foundation, a
slab-on-grade foundation or a similar foundation element.
SHEAR CAP: A projection below the slab used to increase the slab shear strength. See Section 517.2.6.
SHEAR WALL:
Detailed plain masonry shear wall: A masonry shear wall designed to resist lateral forces neglecting
stresses in reinforcement, and designed in accordance with Section 706.1.
Intermediate prestressed masonry shear wall: A prestressed masonry shear wall designed to resist
lateral forces considering stresses in reinforcement, and designed in accordance with Section 2106.1.
Intermediate reinforced masonry shear wall: A masonry shear wall designed to resist lateral forces
considering stresses in reinforcement, and designed in accordance with Section 706.1.
Ordinary plain masonry shear wall: A masonry shear wall designed to resist lateral forces neglecting
stresses in reinforcement, and designed in accordance with Section 706.1.
Ordinary plain prestressed masonry shear wall: A prestressed masonry shear wall designed to resist
lateral forces considering stresses in reinforcement, and designed in accordance with Section 706.1.
Ordinary reinforced masonry shear wall: A masonry shear wall designed to resist lateral forces
considering stresses in reinforcement, and designed in accordance with Section 706.1.
Special prestressed masonry shear wall: A prestressed masonry shear wall designed to resist lateral
forces considering stresses in reinforcement and designed in accordance with Section 706.1 except
that only grouted, laterally restrained tendons are used.
Special reinforced masonry shear wall: A masonry shear wall designed to resist lateral forces
considering stresses in reinforcement, and designed in accordance with Section 706.1.
SHEAR PANEL: A floor, roof, or wall element sheathed to act as a shear wall or diaphragm.
SHELL: The outer portion of a hollow masonry unit as placed in masonry.
SHORES: Vertical or inclined support members designed to carry the weight of the formwork,
concrete, and construction loads above.
SITE CLASS: A classifi cation assigned to a site based on the types of soils present and their engineering
properties as defined in Chapter 2.
SPECIAL ANCHORAGE DEVICE: Anchorage device that standardized acceptance tests of AASHTO
“Standard Specifications for Highway Bridges,” Division II, Article 10.3.2.3.
2
SPECIAL BOUNDARY ELEMENT: Boundary element required by Section 521.9.6.2 or 521.9.6.3.
SPECIAL INSPECTION: Inspection as herein required of the materials, installation, fabrication, erection
or placement of components and connections requiring special expertise to ensure compliance with
approved construction documents and referenced standards (See Section 903).
SPECIAL INSPECTION, CONTINUOUS: The full-time observation of work requiring special inspection by
an approved special inspector who is present in the area where the work is being performed.
SPECIAL INSPECTION, PERIODIC: The part-time or intermittent observation of work requiring special
inspection by an approved special inspector who is present in the area where the work has been or is
being performed and at the completion of the work.
All rights reserved
26 / 496
SPECIAL MOMENT FRAME: A cast-in-place frame complying with the requirements of Section 521.1.3
through 521.1.7, 521.5 through 521.7, or a precast frame complying with the requirements of 521.1.3
through 521.1.7 and 521.5 through 521.8. In addition, the requirements for ordinary moment frames
shall be satisfied.
SPECIAL STRUCTURAL WALL: A cast-in-place or precast wall complying with the requirements of
Section 521.1.3 through 521.1.7, 521.9, and 521.10, as applicable, in addition to the requirements for
ordinary reinforced concrete structural walls.
SPECIFIED COMPRESSIVE STRENGTH OF MASONRY, f ‘m: Minimum compressive strength, expressed
as force per unit of net cross-sectional area, required of the masonry used in construction by the
construction documents, and upon which the project design is based. Whenever the quantity f’m is
under the radical sign, the square root of numerical value only is intended and the result has units of
kilograms per square meter.
SPIRAL REINFORCEMENT: Continuously wound reinforcement in the form of a cylindrical helix.
SPLITTING TENSILE STRENGTH (fct): Tensile strength of concrete determined in accordance with ASTM
C 496M as described in ASTM C 330. See Section 504.1.4.
SPRAYED FIRE-RESISTANT MATERIALS: Cementitious or fibrous materials that are sprayed to provide
fire-resistant protection of the substrates.
STACK BOND: The placement of masonry units in a bond pattern is such that head joints in successive
courses are vertically aligned. For the purpose of this code, requirements for stack bond shall apply to
masonry laid in other than running bond.
STEEL CONSTRUCTION, COLD-FORMED: That type of construction made up entirely or in part of steel
structural members cold formed to shape from sheet or strip steel such as roof deck, floor and wall
panels, studs, floor joists, roof joists and other structural elements.
STEEL FIBER-REINFORCED CONCRETE: Concrete containing dispersed randomly oriented steel fibers.
STEEL JOIST: Any steel structural member of a building or structure made of hot-rolled or cold-formed
solid or open-web sections, or riveted or welded bars, strip or sheet steel members, or slotted and
expanded, or otherwise deformed rolled sections.
STEEL MEMBER, STRUCTURAL: Any steel structural member of a building or structure consisting of a
rolled steel structural shape other than cold-formed steel, or steel joist members.
STIRRUP: Reinforcement used to resist shear and torsion stresses in a structural member; typically
bars, wires, or welded wire reinforcement either single leg or bent into L, U, or rectangular shapes and
located perpendicular to or at an angle to longitudinal reinforcement. (The term “stirrups” is usually
applied to lateral reinforcement in flexural members and the term “ties” to those in compression
members.) See also Tie.
STONEMASONRY: Masonry composed of field, quarried or cast stone units bonded by mortar.
Ashlar stone masonry: Stone masonry composed of rectangular units having sawed, dressed or
squared bed surfaces and bonded by mortar.
Rubble stone masonry: Stone masonry composed of irregular-shaped units bonded by mortar.
STORAGE RACKS: Include industrial pallet racks, moveable shelf racks, and stacker racks made of coldformed or hot-rolled structural members. Does not include other types of racks such as drive-in and
drive-through racks, cantilever racks, portable racks, or racks made of materials other than steel.
All rights reserved
27 / 496
STORY: The portion of a structure between the tops of two successive floor surfaces and, for the
topmost story, from the top of the fl oor surface to the top of the roof surface.
STORY ABOVE GRADE PLANE: A story in which the floor or roof surface at the top of the story is more
than 1,800 mm above grade plane or is more than 3,600 mm above the finished ground level at any
point on the perimeter of the structure.
STORY DRIFT: The horizontal deflection at the top of the story relative to the bottom of the story as
determined in Section 311.6.8.6.
STORY DRIFT RATIO: The story drift, as determined in Section 311.6.8.6, divided by the story height,
hsx.
STORY SHEAR: The summation of design lateral seismic forces at levels above the story under
consideration.
STRENGTH:
Design strength: Nominal strength multiplied by a strength reduction factor.
Nominal strength: Strength of a member or cross section calculated in accordance with these
provisions before application of any strength-reduction factors.
Required strength: Strength of a member or cross section required to resist factored loads.
STRESS: Intensity of force per unit area.
STRONG CONNECTION: Connection that remains elastic while adjoining members experience yielding
as a result of the earthquake design displacements.
STRUCTURE: That which is built or constructed and limited to buildings and nonbuilding structures as
defined herein.
STRUCTURAL COMPOSITE LUMBER: Structural member manufactured using wood elements bonded
together with exterior adhesives. Examples of structural composite lumber are:
Laminated veneer lumber (LVL): A composite of wood veneer sheet elements with wood fibers
primarily oriented along the length of the member.
Parallel strand lumber (PSL): A composite of wood strand elements with wood fibers primarily
oriented along the length of the member.
STRUCTURAL CONCRETE: All concrete used for structural purposes including plain and reinforced
concrete.
STRUCTURAL DIAPHRAGM: Structural member, such as a floor or roof slab, that transmits forces
acting in the plane of the member to the vertical elements of the seismic-force-resisting system. See
Section 521 for requirements in the earthquake-resisting structures.
STRUCTURAL GLUED-LAMINATED TIMBER: An engineered, stress-rated product of a timber laminating
plant, comprised of assemblies of specially selected and prepared wood laminations in which the grain
of all laminations is approximately parallel longitudinally and the laminations are bonded with
adhesives.
STRUCTURAL HEIGHT: The vertical distance from the base to the highest level of the seismic forceresisting system of the structure. For pitched or sloped roofs, the structural height is from the base to
the average height of the roof.
All rights reserved
28 / 496
STRUCTURAL OBSERVATION: The visual observation of the structural system by a registered design
professional for general conformance to the approved construction documents. Structural observation
does not include or waive the responsibility for the inspection required Section 903 or other sections
of this code.
STRUCTURAL TRUSS: Assemblage of reinforced concrete members subjected primarily to axial forces.
STRUCTURAL WALL: Wall proportioned to resist combinations of shears, moments, and axial forces. A
shear wall is a structural wall. A structural wall designated as part of the seismic-force-resisting system
shall be categorized as follows:
SUBDIAPHRAGM: A portion of a diaphragm used to transfer wall anchorage forces to diaphragm cross
ties.
SUPPORTS: Those members, assemblies of members, or manufactured elements, including braces,
frames, legs, lugs, snubbers, hangers, saddles, or struts, and associated fasteners that transmit loads
between nonstructural components and their attachments to the structure.
SECTION 218 -TTEMPORARY FACILITIES: Buildings or other structures that are to be in service for a limited time and
have a limited exposure period for environmental loadings.
TENSION-CONTROLLED-SELECTION: A cross section in which the net tensile strain in the extreme
tension steel at nominal strength is greater than or equal to 0.005.
TESTING AGENCY: A company or corporation that provides testing and/or inspection services.
THIN-BED MORTAR: Mortar for use in construction of AAC unit masonry with joints 1.5 mm or less.
TIE: Loop of reinforcing bar or wire enclosing longitudinal reinforcement. A continuously wound bar or
wire in the form of a circle, rectangle, or other polygon shape without re-entrant corners is acceptable.
See also Stirrup.
TIE-DOWN (HOLD-DOWN): A device used to resist uplift of the chords of shear walls.
TIE, LATERAL: Loop of reinforcing bar or wire enclosing longitudinal reinforcement.
TIE, WALL: A connector that connects wythes of masonry walls together.
TILE: Aceramic surface unit, usually relatively thin in relation to facial area, made from clay or a
mixture of clay or other ceramic materials, called the body of the tile, having either a “glazed” or
“unglazed” face and fired above red heat in the course of manufacture to a temperature sufficiently
high enough to produce specific physical properties and characteristics.
TILE, STRUCTURAL CLAY: A hollow masonry unit composed of burned clay, shale, fire clay or mixture
thereof, and having parallel cells.
TOXIC SUBSTANCE: As defined in 29 CFR 1910.1200 Appendix A with Amendments as of February 1,
2000.
TREATEDWOOD: Wood andwood-based materials that use vacuum-pressure impregnation processes
to enhance fire retardant or preservative properties.
All rights reserved
29 / 496
Fire-retardant-treated wood: Pressure-treated lumber and plywood that exhibit reduced surfaceburning characteristics and resist propagation of fire.
Preservative-treated wood: Pressure-treated wood products that exhibit reduced susceptibility to
damage by fungi, insects or marine borers.
SECTION 219 -VVEHICLE BARRIER SYSTEM: A system of components, including anchorages and attachments to the
structural system near open sides or walls of garage floors or ramps, that acts as a restraint for
vehicles.
VENEERS: Facings or ornamentation of brick, concrete, stone, tile, or similar materials attached to a
backing.
SECTION 220 -WWALL: A vertical element with a horizontal length-to-thickness ratio greater than three, used to
enclose space.
Cavity wall: Awall built of masonry units or of concrete, or a combination of these materials, arranged
to provide an airspace within the wall, and in which the inner and outer parts of the wall are tied
together with metal ties.
Composite wall: A wall built of a combination of two or more masonry units bonded together, one
forming the backup and the other forming the facing elements.
Dry-stacked, surface-bonded wall: A wall built of concrete masonry units where the units are stacked
dry, without mortar on the bed or head joints, and where both sides of the wall are coated with a
surface-bonding mortar.
Masonry-bonded hollow wall: A wall built of masonry units so arranged as to provide an airspace
within the wall, and in which the facing and backing of the wall are bonded together with masonry
units.
Parapet wall: The part of any wall entirely above the roof line.
WALL SYSTEM, BEARING: A structural system with bearing walls providing support for all or major
portions of the vertical loads. Shear walls or braced frames provide seismic force resistance.
WEB: An interior solid portion of a hollow masonry unit as placed in masonry.
WELDED WIRE REINFORCEMENT: Reinforcing elements consisting of carbon-steel plain or deformed
wires, conforming to ASTM A 82 or A 496, respectively, fabricated into sheets or rolls in accordance
with ASTM A 185 or A 497M, respectively; or reinforcing elements consisting of stainless-steel plain or
deformed wires fabricated into sheets or rolls conforming to ASTM A 1022.
WIND-BORNE DEBRIS REGIONS: Areas within hurricane prone regions where impact protection is
required for glazed openings.
WOOD SHEAR PANEL: A wood floor, roof or wall component sheathed to act as a shear wall or
diaphragm.
All rights reserved
30 / 496
WOOD STRUCTURAL PANEL: A panel manufactured from veneers, wood strands or wafers or a
combination ofveneer andwood strands orwafers bonded together with waterproof synthetic resins or
other suitable bonding systems. Examples of wood structural panels are:
Composite panels: A wood structural panel that is comprised of wood veneer and reconstituted woodbased material and bonded together with waterproof adhesive;
Oriented strand board (OSB): A mat-formed wood structural panel comprised of thin rectangular
wood strands arranged in cross-aligned layers with surface layers normally arranged in the long panel
direction and bonded with waterproof adhesive; or
Plywood: A wood structural panel comprised of plies of wood veneer arranged in cross-aligned layers.
The plies are bonded with waterproof adhesive that cures on application of heat and pressure.
WORK: The entire construction or separately identifiable parts thereof that are required to be
furnished under the contract documents.
WYTHE: Each continuous, vertical section of a wall, one masonry unit in thickness.
SECTION 221 -YYIELD STRENGTH: Specified minimum yield strength or yield point of reinforcement. Yield strength or
yield point shall be determined in tension according to applicable ASTM standards.
All rights reserved
31 / 496
CHAPTER 3
STRUCTURAL DESIGN
SECTION 301 INTRODUCTION
301.1 NOTATIONS
Ak = load or load effect arising from extra ordinary event A
D = dead load
Di = weight of ice
E = earthquake load
F = load due to fluids with well-defined pressures and maximum heights
Fa = flood load
H = load due to lateral earth pressure, ground water pressure, or pressure of bulk materials
L = live load
Lr = roof live load
R = rain load
S = snow load
T = self-straining load
W = wind load
Wi = wind-on-ice
301.2 GENERAL
Building, structures and parts thereof shall be designed and constructed in accordance with strength
design, load and resistance factor design, allowable stress design, empirical design or conventional
construction methods, as permitted by the applicable material chapters.
301.3 STRENGTH AND STIFFNESS
Buildings and other structures, and all parts thereof, shall be designed and constructed with adequate
strength and stiffness to provide structural stability, protect nonstructural components and systems
from unacceptable damage, and meet the serviceability requirements of Section 301.4.
Acceptable strength shall be demonstrated using one or more of the following procedures:
a. the Strength Procedures of Section 301.3.1,
b. the Allowable Stress Procedures of Section 301.3.2, or
c. subject to the approval of the authority having jurisdiction for individual projects, the PerformanceBased Procedures of Section 301.3.3.
301.3.1 STRENGTH PROCEDURES
Structural and nonstructural components and their connections shall have adequate strength to
resist the applicable load combinations of Section 302.3 of this code without exceeding the
applicable strength limit states for the materials of construction.
301.3.2 ALLOWABLE STRESS PROCEDURES
Structural and nonstructural components and their connections shall have adequate strength to
resist the applicable load combinations of Section 302.4 of this code without exceeding the
applicable allowable stresses for the materials of construction.
301.3.3 PERFORMANCE-BASED PROCEDURES
Structural and nonstructural components and their connections shall be demonstrated by
analysis or by a combination of analysis and testing to provide a reliability not less than that
expected for similar components designed in accordance with the Strength Procedures Section
301.3.1 when subject to the influence of dead, live, environmental, and other loads.
Consideration shall be given to uncertainties in loading and resistance.
All rights reserved
32 / 496
301.4 SERVICEABILITY
Structural systems and members thereof shall be designed to have adequate stiffness to limit
deflections and lateral drift. See Section 311.6.12.1 for drift limits applicable to earthquake loading.
301.4.1 DEFLECTIONS
The deflections of structural members shall not exceed the more restrictive of the limitations of
Sections 301.4.1.1 through 301.4.1.3 or that permitted by Table 301.4.1-1.
TABLE 301.4.1-1 DEFLECTION LIMITS a, b, c, h,i
CONSTRUCTION
Roof members d:
Supporting plaster ceiling
Supporting nonplaster ceiling
Not supporting ceiling
Floor members
Exterior walls and interior partitions:
With brittle finishes
With flexible finishes
Farm buildings
Greenhouses
L
S or We
D + Lc,f
l/360
l/240
l/180
l/360
l/360
l/240
l/180
—
l/240
l/180
l/120
l/240
—
—
—
—
l/240
l/120
—
—
—
—
l/180
l/120
a. For structural roofing and siding made of formed metal sheets, the total load deflection shall not
exceed l/60. For secondary roof structural members supporting formed metal roofing, the live load
deflection shall not exceed l/150. For secondary wall members supporting formed metal siding, the
design wind load deflection shall not exceed l/90. For roofs, this exception only applies when the
metal sheets have no roof covering.
b. Interior partitions not exceeding 1800 mm. in height and flexible, folding and portable partitions are
not governed by the provisions of this section. The deflection criterion for interior partitions is
based on the horizontal load defined in Section 307.13.
c. For wood structural members having a moisture content of less than 16 percent at time of
installation and used under dry conditions, the deflection resulting from L + 0.5D is permitted to be
substituted for the deflection resulting from L + D.
d. The above deflections do not ensure against ponding. Roofs that do not have sufficient slope or
camber to assure adequate drainage shall be investigated for ponding. See Section 310 for rain and
ponding requirements and AAC (Afghan Architectural Code) for roof drainage requirements.
e. The wind load is permitted to be taken as 0.7 times the “component and cladding” loads for the
purpose of determining deflection limits herein.
f. For steel structural members, the dead load shall be taken as zero.
g. For cantilever members, l shall be taken as twice the length of the cantilever.
301.4.1.1 REINFORCED CONCRETE
The deflection of reinforced concrete structural members shall not exceed that permitted by
this code.
301.4.1.2 STEEL
The deflection of steel structural members shall not exceed that permitted by AISC 360, AISI
S100, ASCE 3, ASCE 8, SJI CJ-1.0, SJI JG-1.1, SJI K-1.1 or SJI LH/DLH-1.1, as applicable.
301.4.1.3 MASONRY
The deflection of masonry structural members shall not exceed that permitted by TMS
402/ACI 530/ASCE 5.
301.4.2 LIMITS
Deflection of structural members over span, l, shall not exceed that permitted by Table 301.3.11.
All rights reserved
33 / 496
301.5 ANALYSIS
Load effects on structural members and their connections shall be determined by methods of
structural analysis that take into account equilibrium, general stability, geometric compatibility and
both short- and long-term material properties.
Members that tend to accumulate residual deformations under repeated service loads shall have
included in their analysis the added eccentricities expected to occur during their service life.
Any system or method of construction to be used shall be based on a rational analysis in accordance
with well-established principles of mechanics. Such analysis shall result in a system that provides a
complete load path capable of transferring loads from their point of origin to the load-resisting
elements.
The total lateral force shall be distributed to the various vertical elements of the lateral-force-resisting
system in proportion to their rigidities, considering the rigidity of the horizontal bracing system or
diaphragm. Rigid elements assumed not to be a part of the lateral-force-resisting system are permitted
to be incorporated into buildings provided their effect on the action of the system is considered and
provided for in the design. Except where diaphragms are flexible, or are permitted to be analyzed as
flexible, provisions shall be made for the increased forces induced on resisting elements of the
structural system resulting from torsion due to eccentricity between the center of application of the
lateral forces and the center of rigidity of the lateral-force-resisting system.
Every structure shall be designed to resist the overturning effects caused by the lateral forces specified
in this chapter. See Section 309 for wind loads, Section 312 for lateral soil loads and Section 311 for
earthquake loads.
301.6 OCCUPANCY CATEGORY
Each building and structure shall be assigned an occupancy category in accordance with Table 301.61.
TABLE 301.6-1 OCCUPANCY CATEGORY OF BUILDINGS AND OTHER STRUCTURES
OCCUPANCY
CATEGORY
I
II
III
IV
All rights reserved
NATURE OF OCCUPANCY
Buildings and other structures that represent a low hazard to human life in the event of failure, including but not limited to:
• Agricultural facilities.
• Certain temporary facilities.
• Minor storage facilities.
Buildings and other structures except those listed in Occupancy Categories I, III and IV
Buildings and other structures that represent a substantial hazard to human life in the event of failure, including but
not limited to:
• Buildings and other structures whose primary occupancy is public assembly with an occupant load greater than 300.
• Buildings and other structures containing elementary school, secondary school or day care facilities with an occupant
load greater than 250.
• Buildings and other structures containing adult education facilities, such as colleges and universities with an occupant
load greater than 500.
• Group I-2 occupancies with an occupant load of 50 or more resident patients but not having surgery or emergency
treatment facilities.
• Group I-3 occupancies.
• Any other occupancy with an occupant load greater than 5,000a.
• Power-generating stations, water treatment facilities for potable water, waste water treatment facilities and other
public utility facilities not included in Occupancy Category IV.
• Buildings and other structures not included in Occupancy Category IV containing sufficient quantities of toxic or explosive substances to be dangerous to the public if released.
Buildings and other structures designated as essential facilities, including but not limited to:
• Group I-2 occupancies having surgery or emergency treatment facilities.
• Fire, rescue, ambulance and police stations and emergency vehicle garages.
• Designated earthquake, hurricane or other emergency shelters.
• Designated emergency preparedness, communications and operations centers and other facilities required for
emergency response.
• Power-generating stations and other public utility facilities required as emergency backup facilities for Occupancy
Category IV structures.
• Structures containing highly toxic materials as defined by AAC where the quantity of the material exceeds the maximum
allowable quantities.
• Aviation control towers, air traffic control centers and emergency aircraft hangars.
• Buildings and other structures having critical national defense functions.
• Water storage facilities and pump structures required to maintain water pressure for fire suppression.
34 / 496
a. For purposes of occupant load calculation, occupancies required by AAC (Afghan Architectural
Code) to use gross floor area calculations shall be permitted to use net floor areas to determine
the total occupant load.
301.6.1 MULTIPLE OCCUPANCIES
Where a building or structure is occupied by two or more occupancies not included in the same
occupancy category, it shall be assigned the classification of the highest occupancy category
corresponding to the various occupancies. Where buildings or structures have two or more
portions that are structurally separated, each portion shall be separately classified. Where a
separated portion of a building or structure provides required access to, required egress from or
shares life safety components with another portion having a higher occupancy category, both
portions shall be assigned to the higher occupancy cat egory.
301.7 IN-SITU LOAD TESTS
The building official is authorized to require an engineering analysis or a load test, or both, of any
construction whenever there is reason to question the safety of the construction for the intended
occupancy. Engineering analysis and load tests shall be conducted in accordance with Section 913.
301.8 PRECONSTRUCTION LOAD TESTS
Materials and methods of construction that are not capable of being designed by approved
engineering analysis or alternative test procedures in accordance with Section 911, shall be load
tested.
301.9 ANCHORAGE
301.9.1 GENERAL
Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be
provided to resist the uplift and sliding forces that result from the application of the prescribed
loads.
301.9.2 WALLS
Walls shall be anchored to floors, roofs and other structural elements that provide lateral
support for the wall. Such anchorage shall provide a positive direct connection capable of
resisting the horizontal forces specified in this chapter but not less than the minimum strength
design horizontal force, substituted for “E” in the load combinations of Section 302.3. or 302.4.
Concrete and masonry walls shall be designed to resist bending between anchors where the
anchor spacing exceeds 1220 mm. Required anchors in masonry walls of hollow units or cavity
walls shall be embedded in a reinforced grouted structural element of the wall. See Section 309
for wind design requirements and Section 311 for earthquake design requirements.
301.9.3 DECKS
Where supported by attachment to an exterior wall, decks shall be positively anchored to the
primary structure and designed for both vertical and lateral loads as applicable. Such attachment
shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive
connection to the primary building structure cannot be verified during inspection, decks shall be
self-supporting.
Connections of decks with cantilevered framing members to exterior walls or other framing
members shall be designed for both of the following:
1. The reactions resulting from the dead load and live load specified in Table 307.5-1, or the
snow load specified in Section 308, in accordance with Section 302, acting on all portions of
the deck.
All rights reserved
35 / 496
2. The reactions resulting from the dead load and live load specified in Table 307.5-1, or the
snow load specified in Section 308, in accordance with Section 302, acting on the cantilevered
portion of the deck, and no live load or snow load on the remaining portion of the deck.
301.10 COUNTERACTING STRUCTURAL ACTIONS
Structural members, systems, components and cladding shall be designed to resist forces due to
earthquake and wind, with consideration of overturning, sliding and uplift. Continuous load paths shall
be provided for transmitting these forces to the foundation. Where sliding is used to isolate the
elements, the effects of friction between sliding elements shall be included as a force.
301.11 WIND AND SEISMIC DETAILING
Lateral-force-resisting systems shall meet seismic detailing requirements and limitations, even when
wind load effects are greater than seismic load effects.
SECTION 302 LOAD COMBINATIONS
302.1 GENERAL
Buildings and other structures and portions thereof shall be designed to resist:
1. The load combinations specified in Section 302.3, 302.4.1, 302.4.2.
2. The load combinations specified in code.
3. The load combinations with overstrength factor specified in Section 311.6.4.3.2 where required by
Section 311.6.2.5.2, 311.6.3.3.3 or 311.6.10.2.1. With the simplified procedure of Section 311.6.14,
the load combinations with overstrength factor of Section 311.6.14.3.2 shall be used.
Applicable loads shall be considered, including both earthquake and wind, in accordance with the
specified load combinations. Each load combination shall also be investigated with one or more of the
variable loads set to zero.
Where the load combinations with overstrength factor in Section 311.6.4.3.2 apply, they shall be used
as follows:
1. The basic combinations for strength design with overstrength factor in lieu of Equation 302.3.1-5,
Equation 302.3.1-7 in Section 302.3.1.
2. The basic combinations for allowable stress design with overstrength factor in lieu of Equation
302.4.1-5, Equation 302.4.1-8 in Section 302.4.1.
3. The basic combinations for allowable stress design with overstrength factor in lieu of Equation
302.4.3-5, Equation 302.4.3-6 in Section 302.4.3.
302.2 STABILITY
Regardless of which load combinations are used to design for strength, where overall structure stability
(such as stability against overturning, sliding, or buoyancy) is being verified, use of the load
combinations specified in Section 302.3. or 302.4 shall be permitted. Where the load combinations
specified in Section 302.3 are used, strength reduction factors applicable to soil resistance shall be
provided by a registered design professional.
302.3 LOAD COMBINATIONS USING STRENGTH DESIGN OR LOAD RESISTANCE FACTOR DESIGN
302.3.1 BASIC LOAD COMBINATIONS
Where strength design or load and resistance factor design is used, structures and portions
thereof shall resist the most critical effects from the following combinations of factored loads:
1.4(D + F)
EQUATION 302.3.1-1
1.2(D + F + T) + 1.6(L + H) + 0.5(Lr or S or R)
EQUATION 302.3.1-2
1.2D + 1.6(Lr or S or R) + (f1L or 0.8W)
EQUATION 302.3.1-3
All rights reserved
36 / 496
1.2D + 1.6W + f1L + 0.5(Lr or S or R)
EQUATION 302.3.1-4
1.2D + 1.0E + f1L + f2S
EQUATION 302.3.1-5
0.9D + 1.6W + 1.6H
EQUATION 302.3.1-6
0.9D + 1.0E + 1.6H
EQUATION 302.3.1-7
where:
f1
= 1.0 for floors in places of public assembly, for live loads in excess of 4.80 kN/m2, and for
parking garage live load, and
= 0.5 for other live loads.
f2 = 0.7 for roof configurations (such as saw tooth) that do not shed snow off the structure,
and
= 0.2 for other roof configurations.
Exception: Where other factored load combinations are specifically required by the provisions
of this code, such combinations shall take precedence.
302.3.2 LOAD COMBINATIONS INCLUDING SELF-STRAINING LOADS
Where applicable, the structural effects of load T shall be considered in combination with other
loads. The load factor on load T shall be established considering the uncertainty associated with
the likely magnitude of the load, the probability that the maximum effect of T will occur
simultaneously with other applied loadings, and the potential adverse consequences if the effect
of T is greater than assumed. The load factor on T shall not have a value less than 1.0.
302.3.3 LOAD COMBINATIONS FOR NONSPECIFIED LOADS
Where approved by the Authority Having Jurisdiction, the Responsible Design Professional is
permitted to determine the combined load effect for strength design using a method that is
consistent with the method on which the load combination requirements in Section 302.3.1 are
based. Such a method must be probability-based and must be accompanied by documentation
regarding the analysis and collection of supporting data that is acceptable to the Authority
Having Jurisdiction.
Loads and forces for occupancies or uses not covered in this chapter shall be subject to the
approval of the building official.
302.4 LOAD COMBINATIONS USING ALLOWABLE STRESS DESIGN
302.4.1 BASIC LOAD COMBINATIONS
Where allowable stress design (working stress design), as permitted by this code, is used,
structures and portions thereof shall resist the most critical effects resulting from the following
combinations of loads:
D+F
EQUATION 302.4.1-1
D+H+F+L+T
EQUATION 302.4.1-2
D + H + F + (Lr or S or R)
EQUATION 302.4.1-3
D + H + F + 0.75(L + T) + 0.75(Lr or S or R)
EQUATION 302.4.1-4
D + H + F + (W or 0.7E)
EQUATION 302.4.1-5
All rights reserved
37 / 496
D + H + F + 0.75(W or 0.7E) + 0.75L + 0.75(Lr or S or R)
EQUATION 302.4.1-6
0.6D + W + H
EQUATION 302.4.1-7
0.6D + 0.7E + H
EQUATION 302.4.1-8
Exceptions:
1. Crane hook loads need not be combined with roof live load or with more than three-fourths
of the snow load or one-half of the wind load.
2. Flat roof snow loads of 1.40 kN/m2 or less and roof live loads of 1.40 kN/m2 or less need not
be combined with seismic loads. Where flat roof snow loads exceed 1.40 kN/m2, 20 percent shall
be combined with seismic loads.
302.4.2 STRESS INCREASES
Increases in allowable stresses specified in the appropriate material chapter or the referenced
standards shall not be used with the load combinations of Section 302.4.1, except that increases
shall be permitted in accordance with Chapter 8.
302.4.3 ALTERNATIVE BASIC LOAD COMBINATIONS
In lieu of the basic load combinations specified in Section 302.3.1, structures and portions
thereof shall be permitted to be designed for the most critical effects resulting from the following
combinations. When using these alternative basic load combinations that include wind or
seismic loads, allowable stresses are permitted to be increased or load combinations reduced
where permitted by the material chapter of this code or the referenced standards. For load
combinations that include the counteracting effects of dead and wind loads, only two-thirds of
the minimum dead load likely to be in place during a design wind event shall be used. Where wind
loads are calculated in accordance with Section 309, the coefficient in the following equations
shall be taken as 1.3. For other wind loads, shall be taken as 1. When using these alternative load
combinations to evaluate sliding, overturning and soil bearing at the soil-structure interface, the
reduction of foundation overturning from Section 311.6.13.4 shall not be used. When using these
alternative basic load combinations for proportioning foundations for loadings, which include
seismic loads, the vertical seismic load effect, Ev, in Equation 311.6.4.2.2-1 is permitted to be
taken equal to zero.
D + L + (Lr or S or R)
EQUATION 302.4.3-1
D + L + (ω W)
EQUATION 302.4.3-2
D + L + ω W + S/2
EQUATION 302.4.3-3
D + L + S + ω W/2
EQUATION 302.4.3-4
D + L + S + E/1.4
EQUATION 302.4.3-5
0.9D + E/1.4
EQUATION 302.4.3-6
Exceptions:
1. Crane hook loads need not be combined with roof live loads or with more than three-fourths
of the snow load or one-half of the wind load.
2. Flat roof snow loads of 1.40 kN/m2 or less and roof live loads of 1.40 kN/m2 or less need not
be combined with seismic loads. Where flat roof snow loads exceed 1.40 kN/m2, 20 percent
shall be combined with seismic loads.
All rights reserved
38 / 496
302.4.4 OTHER LOADS
Where F, H or T are to be considered in the design, each applicable load shall be added to the
combinations specified in Section 302.4.2.
302.4.4.1 Heliports and helistops.
Heliport and helistop landing areas shall be designed for the following loads, combined in
accordance with Section 302:
1. Dead load, D, plus the gross weight of the helicopter, Dh, plus snow load, S.
2. Dead load, D, plus two single concentrated impact loads, L, approximately 2400 mm apart
applied anywhere on the touchdown pad (representing each of the helicopter’s two main
landing gear, whether skid type or wheeled type), having a magnitude of 0.75 times the
gross weight of the helicopter. Both loads acting together total 1.5 times the gross weight
of the helicopter.
3. Dead load, D, plus a uniform live load, L, of 4.80 kN/m2.
Exception: Landing areas designed for helicopters with gross weights not exceeding 13.00
kN in accordance with Items 1 and 2 shall be permitted to be designed using a 2.00 kN/m2
uniform live load in Item 3, provided the landing area is identified with a 13.00 kN weight
limitation. This 2.00 kN/m2 uniform live load shall not be reduced. The landing area weight
limitation shall be indicated by the numeral “3” (tons) located in the bottom right corner of
the landing area as viewed from the primary approach path. The indication for the landing
area weight limitation shall be a minimum 1500 mm in height.
302.4.5 LOAD COMBINATIONS INCLUDING SELF-STRAINING LOADS
Where applicable, the structural effects of load T shall be considered in combination with other
loads. Where the maximum effect of load T is unlikely to occur simultaneously with the
maximum effects of other variable loads, it shall be permitted to reduce the magnitude of T
considered in combination with these other loads. The fraction of T considered in combination
with other loads shall not be less than 0.75.
302.5 LOAD COMBINATIONS FOR EXTRAORDINARY EVENTS
302.5.1 APPLICABILITY
Where required by the owner or applicable code, strength and stability shall be checked to
ensure that structures are capable of withstanding the effects of extraordinary (i.e., lowprobability) events, such as fires, explosions, and vehicular impact without disproportionate
collapse.
302.5.2 LOAD COMBINATIONS
302.5.2.1 CAPACITY
For checking the capacity of a structure or structural element to withstand the effect of an
extraordinary event, the following gravity load combination shall be considered:
(0.9 or 1.2)D + Ak + 0.5L + 0.2S
EQUATION 302.5.2.1-1
in which Ak = the load or load effect resulting from extraordinary event A.
302.5.2.2 RESIDUAL CAPACITY
For checking the residual load-carrying capacity of a structure or structural element following
the occurrence of a damaging event, selected load-bearing elements identified by the
Responsible Design Professional shall be notionally removed, and the capacity of the damaged
structure shall be evaluated using the following gravity load combination:
All rights reserved
39 / 496
(0.9 or 1.2)D + 0.5L + 0.2(Lr or S or R)
EQUATION 302.5.2.2-1
302.6 STABILITY REQIREMENTS
Stability shall be provided for the structure as a whole and for each of its elements. Any method that
considers the influence of second-order effects is permitted.
SECTION 303 BLANK
SECTION 304 STRUCTURAL INTEGRITY
304.1 GENERAL
All structures shall be provided with a continuous load path in accordance with the requirements of
Section 304.4. and shall have a complete lateral force-resisting system with adequate strength to resist
the forces indicated in Section 304.5. All members of the structural system shall be connected to their
supporting members in accordance with Section 304.6. The effects on the structure and its
components due to the forces stipulated in this section shall be taken as the notional load, N, and
combined with the effects of other loads in accordance with the load combinations of Section of
Section 304.4. Where material resistance is dependent on load duration, notional loads are permitted
to be taken as having a duration of 10 minutes. Structures designed in conformance with the
requirements of this Standard for Seismic Design Categories B, C, D, E, or F shall be deemed to comply
with the requirements of Sections 304.4, 304.5, 304.6.
304.2 FRAME STRUCTURES
Frame structures shall comply with the requirements of this section.
304.2.1 CONCRETE FRAME STRUCTURES
Frame structures constructed primarily of reinforced or prestressed concrete, either cast-inplace or precast, or a combination of these, shall conform to the requirements of Sections 506.13,
517.3.8.5, 517.3.8.6, 520.5 as applicable. Where this code requires that nonprestressed
reinforcing or prestressing steel pass through the region bounded by the longitudinal column
reinforcement, that reinforcing or prestressing steel shall have a minimum nominal tensile
strength equal to two-thirds of the required one-way vertical strength of the connection of
the floor or roof system to the column in each direction of beam or slab reinforcement passing
through the column.
Exception: Where concrete slabs with continuous reinforcing having an area not less than 0.0015
times the concrete area in each of two orthogonal directions are present and are either
monolithic with or equivalently bonded to beams, girders or columns, the longitudinal
reinforcing or prestressing steel passing through the column reinforcement shall have a nominal
tensile strength of one-third of the required one-way vertical strength of the connection of the
floor or roof system to the column in each direction of beam or slab reinforcement passing
through the column.
304.2.2 STRUCTURAL STEEL, OPEN WEB STEEL JOIST OR JOIST GIRDER, OR COMPOSITE STEEL AND
CONCRETE FRAME
Frame structures constructed with a structural steel frame or a frame composed of open web steel
joists, joist girders with or without other structural steel elements or a frame composed of composite
steel or composite steel joists and reinforced concrete elements shall conform to the requirements of
this section.
304.2.2.1 Columns. Each column splice shall have the minimum design strength in tension to
transfer the design dead and live load tributary to the column between the splice and the splice
or base immediately below.
All rights reserved
40 / 496
304.2.2.2. Beams. End connections of all beams and girders shall have a minimum nominal axial
tensile strength equal to the required vertical shear strength for allowable stress design (ASD) or
two-thirds of the required shear strength for load and resistance factordesign (LRFD) but not less
than 45 kN. For the purpose of this section, the shear force and the axial tensile force need not
be considered to act simultaneously.
Exception: Where beams, girders, open web joist and joist girders support a concrete slab or
concrete slab on metal deck that is attached to the beam or girder with not less than 10.00 mm
diameter headed shear studs, at a spacing of not more than 300 mm on center, averaged over
the length of the member, or other attachment having equivalent shear strength, and the slab
contains continuous distributed reinforcement in each of two orthogonal directions with an area
not less than 0.0015 times the concrete area, the nominal axial tension strength of the end
connection shall be permitted to be taken as half the required vertical shear strength for ASD or
one-third of the required shear strength for LRFD, but not less than 45 kN.
304.3 BEARING WALL STRUCTURES
Bearing wall structures shall have vertical ties in all load-bearing walls and longitudinal ties, transverse
ties and perimeter ties at each floor level in accordance with this section.
304.3.1 CONCRETE WALL STRUCTURES
Precast bearing wall structures constructed solely of reinforced or prestressed concrete, or
combinations of these shall conform to the requirements of Sections 506.13, 517.3.8.5 and
520.5.
304.3.2 OTHER BEARING WALL STRUCTURES
Ties in bearing wall structures other than those covered in Section 304.3.1 shall conform to this
section.
304.3.2.1 LONGITUDINAL TIES
Longitudinal ties shall consist of continuous reinforcement in slabs; continuous or spliced
decks or sheathing; continuous or spliced members framing to, within or across walls; or
connections of continuous framing members to walls. Longitudinal ties shall extend across
interior load-bearing walls and shall connect to exterior load-bearing walls and shall be
spaced at not greater than 3000 mm on center. Ties shall have a minimum nominal tensile
strength, TT, given by Equation 304.3.2.1-1. For ASD the minimum nominal tensile strength
shall be permitted to be taken as 1.5 times the allowable tensile stress times the area of the
tie.
TT = wLS ≤ aTS
EQUATION 304.3.2.1-1
where:
L = The span of the horizontal element in the direction of the tie, between bearing walls, m.
w = The weight per unit area of the floor or roof in the span being tied to or across the wall,
N/m2.
S = The spacing between ties, m.
aT = A coefficient with a value of 2.25 kN/m for masonry bearing wall structures and a value
of 0.6 kN/m for structures with bearing walls of cold-formed steel light-frame
construction.
304.3.2.2 TRANSVERSE TIES
Transverse ties shall consist of continuous reinforcement in slabs; continuous or spliced
decks or sheathing; continuous or spliced members framing to, within or across walls; or
connections of continuous framing members to walls. Transverse ties shall be placed no
farther apart than the spacing of loadbearingwalls. Transverse ties shall have minimum
nominal tensile strength TT, given by Equation 304.3.2.1-1. For ASD the minimum nominal
All rights reserved
41 / 496
tensile strength shall be permitted to be taken as 1.5 times the allowable tensile stress times
the area of the tie.
304.3.2.3 PERIMETER TIES
Perimeter ties shall consist of continuous reinforcement in slabs; continuous or spliced decks
or sheathing; continuous or spliced members framing to, within or acrosswalls; or
connections of continuous framing members to walls. Ties around the perimeter of each
floor and roof shall be located within 1200 mm of the edge and shall provide a nominal
strength in tension not less than Tp, given by Equation 304.3.2.3-1. For ASD the minimum
nominal tensile strength shall be permitted to be taken as 1.5 times the allowable tensile
stress times the area of the tie.
Tp = 90.7w ≤ βT
EQUATION 304.3.2.3-1
where:
w = As defined in Section 304.3.2.1.
βT = A coefficient with a value of 7200 kN for structures with masonry bearing walls and a
value of 1300 kN for structures with bearing walls of cold-formed steel light-frame
construction.
304.3.2.4 VERTICAL TIES
Vertical ties shall consist of continuous or spliced reinforcing, continuous or spliced
members, wall sheathing or other engineered systems. Vertical tension ties shall be
provided in bearing walls and shall be continuous over the height of the building. The
minimum nominal tensile strength for vertical ties within a bearing wall shall be equal to the
weight of the wall within that story plus the weight of diaphragm tributary to the wall in the
story below. No fewer than two ties shall be provided for each wall. The strength of each tie
need not exceed 450 kN/m of wall tributary to the tie forwalls of masonry construction or
140 kN/m of wall tributary to the tie for walls of cold-formed steel light-frame construction.
304.4 LOAD COMBINATIONS OF INTEGRITY
The notional loads, N, specifi ed in Section 304.5 through Section 304.6 shall be combined with dead
and live loads in accordance with Section 304.4.1 for strength design and Section 304.4.2 for allowable
stress design.
304.4.1 STRENGTH DESIGN NOTIONAL LOAD COMBINATION
a. 1.2D + 1.0N + L + 0.2S
b. 0.9D + 1.0N
304.4.2 ALLOWABLE STRESS DESIGN NOTIONAL LOAD COMBINATIONS
a. D 0.7N
b. D + 0.75(0.7N) + 0.75L+ 0.75(Lr or S or R)
c. 0.6D + 0.7N
304.5 LOAD PATH CONNECTIONS
All parts of the structure between separation joints shall be interconnected to form a continuous path
to the lateral force-resisting system, and the connections shall be capable of transmitting the lateral
forces induced by the parts being connected. Any smaller portion of the structure shall be tied to the
remainder of the structure with elements having strength to resist a force of not less than 5% of the
portion’s weight.
All rights reserved
42 / 496
304.6 LATERAL FORCES
Each structure shall be analyzed for the effects of static lateral forces applied independently in each of
two orthogonal directions. In each direction, the static lateral forces at all levels shall be applied
simultaneously. For purposes of analysis, the force at each level shall be determined using Equatİon
304.6-1 as follows:
Fx = 0.01 Wx
EQUATION 304.6-1
where
Fx = the design lateral force applied at story x and
Wx = the portion of the total dead load of the structure,
D, located or assigned to level x.
Structures explicitly designed for stability, including second-order effects, shall be deemed to comply
with the requirements of this section.
SECTION 305 CLASSIFICATION OF BUILDINGS AND OTHER STRUCTURES
305.1 RISK CATEGORIZATION
Buildings and other structures shall be classified, based on the risk to human life, health, and welfare
associated with their damage or failure by nature of their occupancy or use, according to Table 305.1-1
for the purposes of applying flood, wind, snow, earthquake, and ice provisions. Each building or other
structure shall be assigned to the highest applicable risk category or categories. Minimum design loads
for structures shall incorporate the applicable importance factors given in Table 305.3-1, as required
by other sections of this Standard. Assignment of a building or other structure to multiple risk
categories based on the type of load condition being evaluated (e.g., snow or seismic) shall be
permitted. When the building code or other referenced standard specifies an Occupancy Category, the
Risk Category shall not be taken as lower than the Occupancy Category specified therein.
TABLE 305.1-1 Risk Category of Buildings and Other Structures for Flood, Wind, Snow, Earthquake,
and Ice Loads
User or Occupancy of Buildings and Structures
Risk Category
I
II
Buildings and other structures that represent a low risk to human life in the event of failure
All buildings and other structures except those listed in Risk Categories I, III, and IV
Buildings and other structures, the failure of which could pose a substantial risk to human life.
Buildings and other structures, not included in Risk Category IV, with potential to cause a substantial
economic impact and/or mass disruption of day-to-day civilian life in the event of failure.
III
Buildings and other structures not included in Risk Category IV (including, but not limited to, facilities
that manufacture, process, handle, store, use, or dispose of such substances as hazardous fuels,
hazardous chemicals, hazardous waste, or explosives) containing toxic or explosive substances where
their quantity exceeds a threshold quantity established by the authority having jurisdiction and is
sufficient to pose a threat to the public if released.
Buildings and other structures designated as essential facilities.
Buildings and other structures, the failure of which could pose a substantial hazard to the community.
Buildings and other structures (including, but not limited to, facilities that manufacture, process,
handle, store, use, or dispose of such substances as hazardous fuels, hazardous chemicals, or hazardous
waste) containing suffi cient quantities of highly toxic substances where the quantity exceeds a
threshold quantity established by the authority having jurisdiction to be dangerous to the public if
released and is suffi cient to pose a threat to the public if released
IV
Buildings and other structures required to maintain the functionality of other Risk Category IV
structures.
All rights reserved
43 / 496
305.2 MULTIPLE RISK CATEGORIES
Where buildings or other structures are divided into portions with independent structural systems, the
classification for each portion shall be permitted to be determined independently. Where building
systems, such as required egress, HVAC, or electrical power, for a portion with a higher risk category
pass through or depend on other portions of the building or other structure having a lower risk
category, those portions shall be assigned to the higher risk category.
305.3 TOXIC, HIGHLY TOXIC AND EXPLOSIVE SUBSTANCES
Buildings and other structures containing toxic, highly toxic, or explosive substances are permitted to
be classified as Risk Category II structures if it can be demonstrated to the satisfaction of the authority
having jurisdiction by a hazard assessment as part of an overall risk management plan (RMP) that a
release of the toxic, highly toxic, or explosive substances is not suffi cient to pose a threat to the
public. To qualify for this reduced classification, the owner or operator of the buildings or other
structures containing the toxic, highly toxic, or explosive substances shall have an RMP that
incorporates three elements as a minimum: a hazard assessment, a prevention program, and an
emergency response plan. As a minimum, the hazard assessment shall include the preparation and
reporting of worst-case release scenarios for each structure under consideration, showing the
potential effect on the public for each. As a minimum, the worst-case event shall include the complete
failure (instantaneous release of entire contents) of a vessel, piping system, or other storage structure.
A worst-case event includes (but is not limited to) a release during the design wind or design seismic
event. In this assessment, the evaluation of the effectiveness of subsequent measures for accident
mitigation shall be based on the assumption that the complete failure of the primary storage structure
has occurred. The offsite impact shall be defined in terms of population within the potentially affected
area. To qualify for the reduced classification, the hazard assessment shall demonstrate that a release
of the toxic, highly toxic, or explosive substances from a worst-case event does not pose a threat to
the public outside the property boundary of the facility. As a minimum, the prevention program shall
consist of the comprehensive elements of process safety management, which is based upon accident
prevention through the application of management controls in the key areas of design, construction,
operation, and maintenance. Secondary containment of the toxic, highly toxic, or explosive substances
(including, but not limited to, double wall tank, dike of suffi cient size to contain a spill, or other means
to contain a release of the toxic, highly toxic, or explosive substances within the property boundary of
the facility and prevent release of harmful quantities of contaminants to the air, soil, ground water, or
surface water) are permitted to be used to mitigate the risk of release. Where secondary containment
is provided, it shall be designed for all environmental loads and is not eligible for this reduced
classification.
TABLE 305.3-1 Importance Factors by Risk Category of Buildings and Other Structures for Snow, Ice,
and Earthquake Loads
Risk Category
from
Table 3.5.1-1
I
II
III
IV
Snow Importance
Factor,
Is
0.80
1.00
1.10
1.20
Ice Importance
Factor—Thickness,
Ii
0.80
1.00
1.25
1.25
Ice Importance
Factor—Wind,
Iw
1.00
1.00
1.00
1.00
Seismic Importance
Factor,
Ie
1.00
1.00
1.25
1.50
SECTION 306 DEAD LOADS
306.1 DEFINITION
Dead loads consist of the weight of all materials of construction incorporated into the building
including, but not limited to, walls, floors, roofs, ceilings, stairways, built-in partitions, finishes,
cladding, and other similarly incorporated architectural and structural items, and fixed service
equipment including the weight of cranes. Dead loads shall be considered permanent loads.
All rights reserved
44 / 496
306.2 WEIGHTS OF MATERIALS OF CONSTRUCTION
For purposes of design, the actual weights of materials of construction and fixed service equipment
shall be used. In the absence of definite information, values used shall be subject to the approval of
the building official.
306.3 WEIGHT OF FIXED SERVICE EQUIPMENT
In determining dead loads for purposes of design, the weight of fixed service equipment, such as
plumbing stacks and risers, electrical feeders, and heating, ventilating, and air conditioning systems
shall be included.
SECTION 307 LIVE LOADS
307.1 GENERAL
Those loads produced by the use and occupancy of the building or other structure and do not include
construction or environmental loads such as wind load, snow load, rain load, earthquake load, flood
load or dead load.
307.2 LOADS NOT SPECIFIED
For occupancies or uses not designated in Table 307.5-1, the live load shall be determined in
accordance with a method approved by the building official.
307.3 UNIFORM LIVE LOADS
The live loads used in the design of buildings and other structures shall be the maximum loads
expected by the intended use or occupancy but shall in no case be less than the minimum uniformly
distributed unit loads required by Table 307.5-1.
307.4 CONCENTRATED LOADS
Floors and other similar surfaces shall be designed to support the uniformly distributed live loads
prescribed in Section 307.3 or the concentrated load, in kilonewtons, given in Table 307.5-1, whichever
produces the greater load effects. Unless otherwise specified, the indicated concentration shall be
assumed to be uniformly distributed over an area 0.75 m. by 0.75 m. (0.56 m2) and shall be located so
as to produce the maximum load effects in the structural members.
307.5 PARTITION LOADS
In office buildings and in other buildings where partition locations are subject to change, provisions
for partition weight shall be made, whether or not partitions are shown on the construction
documents, unless the specified live load exceeds 3.80 kN/m2. The partition load shall not be less
than a uniformly distributed live load of 0.75 kN/m2.
TABLE 307.5-1
g
MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS, Lo, AND MINIMUM CONCENTRATED LIVE LOADS
OCCUPANCY OR USE
1. Apartments (see residential)
2. Access floor systems
Office use
Computer use
3. Armories and drill rooms
4. Assembly areas and theaters
Fixed seats (fastened to floor)
Follow spot, projections and control rooms
Lobbies Movable seats
Stages and platforms
Other assembly areas
5. Balconies (exterior) and decksh
6. Bowling alleys
All rights reserved
2
UNIFORM (N/m )
—
CONCENTRATED (N)
—
2400
4800
7200
9000
9000
—
2900
2400
4800
6000
4800
Same as occupancy
served
3600
—
—
—
45 / 496
7. Catwalks
8. Cornices
9. Corridors, except as otherwise indicated
10. Dance halls and ballrooms
11. Dining rooms and restaurants
12. Dwellings (see residential)
2000
3000
5000
5000
5000
—
1500
—
—
—
—
—
13. Elevator machine room grating
(on area of 25 cm2)
—
1500
14. Finish light floor plate construction
(on area of 6 cm2)
—
1000
15. Fire escapes
On single-family dwellings only
5000
2000
—
16. Garages (passenger vehicles only) Trucks and buses
17. Grandstands
(see stadium and arena bleachers)
18. Gymnasiums, main floors and balconies
19. Handrails, guards and grab bars
20. Hospitals
Corridors above first floor
Operating rooms, laboratories
Patient rooms
21. Hotels (see residential)
22. Libraries
Corridors above first floor
Reading rooms
Stack rooms
2000
See Section 1606.6
—
5000
See Section 1606.7
—
—
4000
3000
2000
—
5000
5000
5000
—
4000
3000
5000
5000
5000
7500b
Note a
TABLE 307.5-1 continued
g
MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS, Lo, AND MINIMUM CONCENTRATED LIVE LOADS
OCCUPANCY OR USE
23. Manufacturing
Heavy
Light
24. Marquees
25.
Office buildings
Corridors above first floor
File and computer rooms shall be designed for heavier loads based on anticipated
occupancy
Lobbies and first-floor corridors
Offices
26. Penal institutions Cell blocks
Corridors
27. Residential
One- and two-family dwellings
Uninhabitable attics without storagei
Uninhabitable attics with limited storagei, j, k
Habitable attics and sleeping areas
All other areas
Hotels and multifamily dwellings
Private rooms and corridors serving them
Public rooms and corridors serving them
28. Reviewing stands, grandstands and bleachers
29. Roofs
All roof surfaces subject to maintenance workers
Awnings and canopies
Fabric construction supported by a lightweight rigid skeleton structure
All other construction
Ordinary flat, pitched, and curved roofs
Primary roof members, exposed to a work floor
Single panel point of lower chord of roof trusses or any point along primary structural
members supporting roofs:
Over manufacturing, storage warehouses, and repair garages
All rights reserved
UNIFORM (kN/m2)
CONCENTRATED (N.)
12000
6000
30000
15000
3600
—
4000
9000
—
—
4800
2400
9000
9000
2000
5000
—
500
1000
1500
2000
—
2000
5000
Note c
1500
2400
nonreducible
1000
1000
9000
46 / 496
All other occupancies
Roofs used for other special purposes
Roofs used for promenade purposes
Roofs used for roof gardens or assembly purposes
1500
Note 1
Note 1
3000
5000
30. Schools
Classrooms
Corridors above first floor
First-floor corridors
31. Scuttles, skylight ribs and accessible ceilings
32. Sidewalks, vehicular driveways and yards, subject to trucking
33. Skating rinks
2000
4000
5000
—
5000
5000
5000
1000
E
—
5000
TABLE 307.5-1 continued
g
MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS, Lo, AND MINIMUM CONCENTRATED LIVE LOADS
OCCUPANCY OR USE
UNIFORM (kN/m2)
CONCENTRATED (N)
34. Stadiums and arenas
Bleachers
Fixed seats (fastened to floor)
5000c
3000c
—
35. Stairs and exits
One- and two-family dwellings
All other
2000
5000
Note f
36. Storage warehouses
(shall be designed for heavier loads if required for anticipated storage)
Heavy
Light
37. Stores
Retail
First floor
Upper floors
Wholesale, all floors
38. Vehicle barrier systems
39. Walkways and elevated platforms
(other than exitways)
40. Yards and terraces, pedestrians
12000
6000
5000
3600
6000
See Section 307.7.3
5000
5000
5000
3000
5000
—
—
a. Floors in garages or portions of buildings used for the storage of motor vehicles shall be designed for
the uniformly distributed live loads of Table 307.5-1 or the following concentrated loads: (1) for
garages restricted to passenger vehicles accommodating not more than nine passengers, 15 kN
acting on an area of 100 mm by 100 mm; (2) for mechanical parking structures without slab or deck
which are used for storing passenger vehicles only, 1.0 tons per wheel.
b. The loading applies to stack room floors that support nonmobile, double-faced library book stacks,
subject to the following limitations:
1. The nominal book stack unit height shall not exceed 2300 mm;
2. The nominal shelf depth shall not exceed 300 mm for each face; and
3. Parallel rows of double-faced book stacks shall be separated by aisles not less than 900 mm
wide.
c. Design in accordance with the ICC 300.
d. Other uniform loads in accordance with an approved method which contains provisions for truck
loadings shall also be considered where appropriate.
e. The concentrated wheel load shall be applied on an area of 100 mm by 100 mm.
f. M i n i m u m concentrated load on stair treads on area of 25 square cm. is 1500 N.
g. Where snow loads occur that are in excess of the design conditions, the structure shall be designed
to support the loads due to the increased loads caused by drift buildup or a greater snow design
determined by the building official see Section 307.
h. See Section 301.9.3 for decks attached to exterior walls.
i. Attics without storage are those where the maximum clear height between the joist and rafter is less
than 1000 mm, or where there are not two or more adjacent trusses with the same web
configuration capable of containing a rectangle 1000 mm high by 600 mm wide, or greater, located
All rights reserved
47 / 496
within the plane of the truss. For attics without storage, this live load need not be assumed to act
concurrently with any other live load requirements.
j. For attics with limited storage and constructed with trusses, this live load need only be applied to
those portions of the bottom chord where there are two or more adjacent trusses with the same
web configuration capable of containing a rectangle 1000 mm high by 600 mm wide or greater,
located within the plane of the truss. The rectangle shall fit between the top of the bottom chord
and the bottom of any other truss member, provided that each of the following criteria is met:
1. The attic area is accessible by a pull-down stairway or framed opening in accordance with AAC
(Afghan Architectural Code), and
2. The truss shall have a bottom chord pitch less than 2:12.
3. Bottom chords of trusses shall be designed for the greater of actual imposed dead load or
480 Pa, uniformly distributed over the entire span.
k. Attic spaces served by a fixed stair shall be designed to support the minimum live load specified for
habitable attics and sleeping rooms.
l. Roofs used for other special purposes shall be designed for appropriate loads as approved by the
building official.
307.6 TRUCK AND BUS GARAGES
Minimum live loads for garages having trucks or buses shall be as specified in Table 307.6.1-1, but
shall not be less than 2.40 kN/m2, unless other loads are specifically justified and approved by the
building official. Actual loads shall be used where they are greater than the loads specified in the table.
307.6.1 TRUCK AND BUS GARAGE LIVE LOAD APPLICATION
The concentrated load and uniform load shall be uniformly distributed over a 3000 mm width on
a line normal to the centerline of the lane placed within a 3700 mm lane. The loads shall be
placed within their individual lanes so as to produce the maximum stress in each structural
member. Single spans shall be designed for the uniform load in Table 307.6.1-1 and one
simultaneous concentrated load positioned to produce the maximum effect. Multiple spans shall
be designed for the uniform load in Table 307.6.1-1 on the spans and two simultaneous
concentrated loads in two spans positioned to produce the maximum negative moment effect.
Multiple span design loads, for other effects, shall be the same as for single spans.
TABLE 307.6.1-1 UNIFORM AND CONCENTRATED LOADS
LOADING CLASSa
UNIFORM LOAD (Newton/linear mm. of lane)
H20-44 and HS20-44
H15-44 and HS15-44
9.3
7.0
CONCENTRATED LOAD (kN)
For moment design
For shear design
80
120
60
90
a. An H loading class designates a two-axle truck with a semitrailer. An HS loading class designates a
tractor truck with a semitrailer. The numbers following the letter classification indicate the gross
weight in tons of the standard truck and the year the loadings were instituted.
307.7 LOADS ON HANDRAILS, GUARDS, GRAB BARS, SEATS AND VEHICLE BARRIER SYSTEMS
Handrails, guards, grab bars, accessible seats, accessible benches and vehicle barrier systems shall be
designed and constructed to the structural loading conditions set forth in this section. Also refer to
relevant chapter of AAC (Afghan Architectural Code).
307.7.1 HANDRAILS AND GUARDS
Handrails and guards shall be designed to resist a load of 0.80 kN/m, applied in any direction at
the top, and to transfer this load through the supports to the structure. Glass handrail assemblies
and guards shall also comply with AAC (Afghan Architectural Code)
Exceptions:
1. For one- and two-family dwellings, only the single concentrated load required by Section
307.7.1.1 shall be applied.
All rights reserved
48 / 496
2. In Group I-3, F, H and S occupancies, for areas that are not accessible to the general public and
that have an occupant load less than 0.22 kN, the minimum load shall be 0.30 kN/m.
307.7.1.1 CONCENTRATED LOAD
Handrails and guards shall be able to resist a single concentrated load of 0.90 kN, applied in
any direction at any point along the top, and to transfer this load through the supports to
the structure. This load need not be assumed to act concurrently with the loads specified
in Section 307.7.1.
307.7.1.2 COMPONENTS
Intermediate rails (all those except the handrail), balusters and panel fillers shall be designed
2
to withstand a horizontally applied normal load of 0.22 kN on an area equal to 0.10 m ,
including openings and space between rails. Reactions due to this loading are not required
to be superimposed with those of Section 307.7.1 or 307.7.1.1.
307.7.2 GRAB BARS, SHOWER SEATS AND DRESSING ROOM BENCH SEATS
Grab bars, shower seats and dressing room bench seat systems shall be designed to resist a
single concentrated load of 1.10 kN applied in any direction at any point.
307.7.3 VEHICLE BARRIER SYSTEMS
Vehicle barrier systems for passenger vehicles shall be designed to resist a single load of 30.00 kN
applied horizontally in any direction to the barrier system and shall have anchorage or
attachment capable of transmitting this load to the structure.
For design of the system, two loading conditions shall be analyzed. The first condition shall apply
the load at a height of 450 mm above the floor or ramp surface. The second loading condition shall
apply the load 700 mm above the floor or ramp surface. The more severe load condition shall
govern the design of the barrier restraint system. The load shall be assumed to act on an area not
to exceed 0.10 m2, and is not required to be assumed to act concurrently with any handrail or
guard loadings specified in Section 307.7.1.
307.8 IMPACT LOADS
The live loads specified in Section 307.3 include allowance for impact conditions. Provisions shall be
made in the structural design for uses and loads that involve unusual vibration and impact forces.
307.8.1 ELEVATORS
Elevator loads shall be increased by 100 percent for impact and the structural supports shall be
designed within the limits of deflection prescribed by ASME A17.1.
307.8.2 MACHINERY
For the purpose of design, the weight of machinery and moving loads shall be increased as
follows to allow for impact:
(1) elevator machinery, 100 percent;
(2) light machinery, shaft- or motor-driven, 20 percent;
(3) reciprocating machinery or power-driven units, 50 percent;
(4) hangers for floors or balconies, 33 percent. Percentages shall be increased where specified by
the manufacturer.
307.9 REDUCTION IN LIVE LOADS
Except for uniform live loads at roofs, all other minimum uniformly distributed live loads, Lo, in Table
307.5-1 are permitted to be reduced in accordance with Section 307.8.1 or 307.8.2. Roof uniform live
loads, other than special purpose roofs of Section 307.11.2.2, are permitted to be reduced in
accordance with Section 307.11.2.
All rights reserved
49 / 496
307.9.1 GENERAL
Subject to the limitations of Section 307.9.1.1 through 307.9.1.4, members for which a value of
KLLAT is 40.00 m2 or more are permitted to be designed for a reduced live load in accordance
with the following equation:
) )]
L = L0 [0.25 + (4,57/√(
EQUATION 307.9.1-1
where:
L =
Reduced design live load per square meter of area supported by the member.
Lo =
Unreduced design live load per square meter of area supported by the member
See Table 307.5-1.
KLL=
Live load element factor See Table 307.9.1-1.
AT = Tributary area, in square meters.
L shall not be less than 0.50Lo for members supporting one floor and L shall not be less than
0.40Lo for members supporting two or more floors.
TABLE 307.9.1-1 LIVE LOAD ELEMENT FACTOR, KLL
ELEMENT
Interior columns
Exterior columns without cantilever slabs
Edge columns with cantilever slabs
Corner columns with cantilever slabs Edge beams without cantilever slabs Interior beams
All other members not identified above including: Edge beams with cantilever slabs
Cantilever beams One-way slabs Two-way slabs
Members without provisions for continuous shear transfer normal to their span
KLL
4
4
3
2
2
2
1
307.9.1.1 ONE-WAY SLABS
The tributary area, AT, for use in Equation 307.9.1-1 for one-way slabs shall not exceed an
area defined by the slab span times a width normal to the span of 1.5 times the slab span.
307.9.1.2 HEAVY LIVE LOADS
Live loads that exceed 4.70 kN/m2 shall not be reduced.
Exceptions:
1. The live loads for members supporting two or more floors are permitted to be reduced by
a maximum of 20 percent, but the live load shall not be less than L as calculated in
Section 307.9.1.
307.9.1.3 PASSENGER VEHICLE GARAGES
The live loads shall not be reduced in passenger vehicle garages.
Exceptions: The live loads for members supporting two or more floors are permitted to be
reduced by a maximum of 20 percent, but the live load shall not be less than L as calculated
in Section 307.9.1.
307.9.1.4 GROUP A OCCUPANCIES
Live loads of 4.70 kN/m2 and at areas where fixed seats are located shall not be reduced in
Group A occupancies.
307.9.1.5 ROOF MEMBERS
Live loads of 4.70 kN/m2 or less shall not be reduced for roof members except as specified in
Section 307.11.2.
All rights reserved
50 / 496
307.9.2 ALTERNATE FLOOR LOVE LOAD REDUCTION
As an alternative to Section 307.9.1, floor live loads are permitted to be reduced in accordance
with the following provisions. Such reductions shall apply to slab systems, beams, girders,
columns, piers, walls and foundations.
1. A reduction shall not be permitted in Group A occupancies.
2. A reduction shall not be permitted where the live load exceeds 4.70 kN/m2 except that the
design live load for members supporting two or more floors is permitted to be reduced by 20
percent.
Exception: For uses other than storage, where approved, additional live load reductions shall
be permitted where shown by the registered design professional that a rational approach has
been used and that such reductions are warranted.
3. A reduction shall not be permitted in passenger vehicle parking garages except that the live
loads for members supporting two or more floors are permitted to be reduced by a maximum
of 20 percent.
4. For live loads not exceeding 4.70 kN/m2, the design live load for any structural member
supporting 14.00 m2 or more is permitted to be reduced in accordance with Equation 16-23.
5. For one-way slabs, the area A, for use in Equation 16-23 shall not exceed the product of the
slab span and a width normal to the span of 0.5 times the slab span.
R = 0.861(A - 13.94)
EQUATION 307.9.2-1
Such reduction shall not exceed the smallest of:
1. 40 percent for horizontal members;
2. 60 percent for vertical members; or
3. R as determined by the following equation.
R = 23.1(1 + D/Lo) EQUATION 307.9.2-2
where:
A = Area of floor supported by the member, square m2.
D = Dead load per square m2 of area supported.
Lo = Unreduced live load per square m2 of area supported.
R = Reduction in percent.
307.10 DISTRIBUTION OF FLOOR LOADS
Where uniform floor live loads are involved in the design of structural members arranged so as to create
continuity, the minimum applied loads shall be the full dead loads on all spans in combination with the
floor live loads on spans selected to produce the greatest effect at each location under consideration.
It shall be permitted to reduce floor live loads in accordance with Section 307.9.
307.11 ROOF LOADS
The structural supports of roofs and marquees shall be designed to resist wind and, where applicable,
snow and earthquake loads, in addition to the dead load of construction and the appropriate live loads
as prescribed in this section, or as set forth in Table 307.5-1. The live loads acting on a sloping surface
shall be assumed to act vertically on the horizontal projection of that surface.
307.11.1 DISTRIBUTION OF LOADS
Where uniform roof live loads are reduced to less than 1.00 kN/m2 in accordance with Section
307.11.2.1 and are applied to the design of structural members arranged so as to create
continuity, the reduced roof live load shall be applied to adjacent spans or to alternate spans,
whichever produces the most unfavorable load effect.
307.11.2 REDUCTION ON ROOF LIVE LOADS
The minimum uniformly distributed live loads of roofs and marquees, Lo, in Table 307.5-1 are
permitted to be reduced in accordance with Section 307.11.2.1 or 307.11.2.2.
All rights reserved
51 / 496
307.11.2.1 FLAT, PITCHED AND CURVED ROOFS
Ordinary flat, pitched and curved roofs, and awnings and canopies other than of fabric
construction supported by lightweight rigid skeleton structures, are permitted to be
designed for a reduced roof live load as specified in the following equations or other
controlling combinations of loads in Section 504, whichever produces the greater load. In
structures such as greenhouses, where special scaffolding is used as a work surface for
workers and materials during maintenance and repair operations, a lower roof load than
specified in the following equations shall not be used unless approved by the building
official. Such structures shall be designed for a minimum roof live load of 0.60 kN/m2.
Lr=LoR1R2
EQUATION 307.11.2.1-1
where: 0,58 ≤ Lr ≤0,96
Lr = Reduced live load per square m of horizontal projection in kN/m2.
The reduction factors R1 and R2 shall be determined as follows:
R1 = 1 for At ≤ 19.00 m2
EQUATION 307.11.2.1-2
R1 = 1.2 – 0.001At for 19.00 m2 < At < 55,00 m2
EQUATION 307.11.2.1-3
R1 = 0.6 for At ≥ 55.00 m2
EQUATION 307.11.2.1-4
where:
2
At = Tributary area (span length multiplied by effective width) in m supported by any
structural member, and
R2 = 1 for F ≤ 4
EQUATION 307.11.2.1-5
R2 = 1.2 – 0.05 F for 4 < F < 12
EQUATION 307.11.2.1-5
R2 = 0.6 for F ≥ 12
EQUATION 307.11.2.1-5
where:
F = For a sloped roof, (0.12 x slope, with slope expressed as a percentage), or for an arch or
dome, the rise-to-span ratio multiplied by 32.
307.11.2.2 SPECIAL-PURPOSE ROOFS
Roofs used for promenade purposes, roof gardens, assembly purposes or other special
purposes, and marquees, shall be designed for a minimum live load, Lo, as specified in Table
307.5-1. Such live loads are permitted to be reduced in accordance with Section 307.9. Live
loads of 4.80 kN/m2 or more at areas of roofs classified as Group A occupancies shall not be
reduced.
307.11.3 LANDSCAPED ROOFS
Where roofs are to be landscaped, the uniform design live load in the landscaped area shall be
1.00 kN/m2. The weight of the landscaping materials shall be considered as dead load and shall
be computed on the basis of saturation of the soil.
307.11.4 AWNINGS AND CANOPIES
Awnings and canopies shall be designed for uniform live loads as required in Table 307.5-1 as
well as for snowloads and wind loads as specified in Sections 308 and 309.
All rights reserved
52 / 496
307.12 CRANE LOADS
The crane live load shall be the rated capacity of the crane. Design loads for the runway beams,
including connections and support brackets, of moving bridge cranes and monorail cranes shall include
the maximum wheel loads of the crane and the vertical impact, lateral and longitudinal forces induced
by the moving crane.
307.12.1 MAXIMUM WHEEL LOAD
The maximum wheel loads shall be the wheel loads produced by the weight of the bridge, as
applicable, plus the sum of the rated capacity and the weight of the trolley with the trolley
positioned on its runway at the location where the resulting load effect is maximum.
307.12.2 VERTICAL IMPACT FORCE
The maximum wheel loads of the crane shall be increased by the percentages shown below to
determine the induced vertical impact or vibration force:
Monorail cranes (powered) ………………………………………………………………………………………… 25 percent
Cab-operated or remotely operated bridge cranes (powered) ……………….……………..…. 25 percent
Pendant-operated bridge cranes (powered) …………………………………………….………..…….. 10 percent
Bridge cranes or monorail cranes with hand-geared bridge, trolley and hoist …….……… 0 percent
307.12.3 LATERAL FORCE
The lateral force on crane runway beams with electrically powered trolleys shall be calculated as
20 percent of the sum of the rated capacity of the crane and the weight of the hoist and trolley.
The lateral force shall be assumed to act horizontally at the traction surface of a runway beam, in
either direction perpendicular to the beam, and shall be distributed according to the lateral
stiffness of the runway beam and supporting structure.
307.12.4 LONGITUDINAL FORCE
The longitudinal force on crane runway beams, except for bridge cranes with hand-geared
bridges, shall be calculated as 10 percent of the maximum wheel loads of the crane. The
longitudinal force shall be assumed to act horizontally at the traction surface of a runway beam, in
either direction parallel to the beam.
307.13 INTERIOR WALLS AND PARTITIONS
Interior walls and partitions that exceed 1800 mm in height, including their finish materials, shall have
adequate strength to resist the loads to which they are subjected but not less than a horizontal load of
2
0.240 kN/m .
Exception: Fabric partitions complying with Section 307.13.1 shall not be required to resist the
minimum horizontal load of 0.24 kN/m2.
307.13.1 FABRIC PARTITIONS
Fabric partitions that exceed 1800 mm in height, including their finish materials, shall have
adequate strength to resist the following load conditions:
1. A horizontal distributed load of 0.24 kN/m2 applied to the partition framing. The total area
used to determine the distributed load shall be the area of the fabric face between the
framing members to which the fabric is attached. The total distributed load shall be uniformly
applied to such framing members in proportion to the length of each member.
2. A concentrated load of 0.200 kN applied to a diameter of 200 mm (area 33.00 mm 2) of the
fabric face at a height of 1400 mm above the floor.
All rights reserved
53 / 496
SECTION 308 SNOW LOADS
308.1 GENERAL
Design snow loads shall be determined in accordance with this section, but the design roof load shall
not be less than that determined by Section 306.
308.2 NOTATIONS
Ce = exposure factor as determined from Table 308.5.4-1.
Cs = slope factor as determined from Figure 308-1.
Ct = thermal factor as determined from Table 308.5.4-2.
h = vertical separation distance in m between the edge of a higher roof including any parapet and the
edge of a lower adjacent roof excluding any parapet
hb = height of balanced snow load determined by dividing ps by , in m
hc = clear height from top of balanced snow load to (1) closest point on adjacent upper roof, (2) top of
parapet, or (3) top of a projection on the roof, in m
hd = height of snow drift, in m
ho = height of obstruction above the surface of the roof, in m
Is = importance factor as prescribed in Section 308.5.3.
lu = length of the roof upwind of the drift, in m
pd = maximum intensity of drift surcharge load, in kN/m2
pf = snow load on flat roofs (“flat” = roof slope ≤ 5°), in kN/m2
pg = ground snow load as determined from Table 308.3-1;or a site-specific analysis, in kN/m2
pm = minimum snow load for low-slope roofs, in kN/m2
ps = sloped roof (balanced) snow load, in kN/m2
s = horizontal separation distance in m between the edges of two adjacent buildings
S = roof slope run for a rise of one
θ = roof slope on the leeward side, in degrees
w = width of snow drift, in m
W = horizontal distance from eave to ridge, in m
 = snow density, in kN/m3 as determined from Equation 308.9.1-1.
308.3 GROUND SNOW LOADS, pg
Ground snow loads, pg, to be used in the determination of design snow loads for roofs shall be as set
forth in Table 308.3-1.
Table 308.3-1 GROUND SNOW LOADS, pg, for AFGHANISTAN
Location
Baghlan
Chackaharam
Chardara
Darulaman
Darwaz
Deshu
Eshkashem
Faizabad
Farah
Gardez
All rights reserved
2
pg (kN/ m )
0,75
0,75
0,95
0,75
0,75
0,75
0,75
0,75
0,75
1,25
Location
Kunduz
Laghman
Lal
Lashkargah
Logar
Maimana
Mazarisherif
Mokar
M. B. Cot
Nawer
2
pg (kN/m )
0,75
0,75
0,95
0,75
0,75
0,75
0,75
0,75
0,75
1,85
54 / 496
Ghazni
Ghelmin
Gazeabad
Herat
Jabulsaraj
Jalalabad
Khwajaghar
Kabul
Kalat
Kandahar
Karizimir
Khost
Khahn
1,25
0,75
0,75
0,75
0,75
0,75
1,25
1,25
0,75
0,75
0,95
0,75
0,75
Salang
Orgon
Paghman
Panjab
Qalainow
Qadis
Sheghnan
Shahrark
Sheberghan
Sarabi
Talikan
Tirinkot
Zaranj
2,80
0,95
0,95
1,25
0,75
0,95
1,85
1,25
0,75
0,75
1,25
0,75
0,75
308.5 FLAT ROOF SNOW LOADS, pf
The flat roof snow load, pf, shall be calculated in kN/m2 using the following formula:
pf = 0.7CeCt Ispg
EQUATION 308.5-1
308.5.1 EXPOSURE FACTOR, Ce
The value for Ce shall be determined from Table 308.5.4-1.
308.5.2 THERMAL FACTOR, Ct
The value for Ct shall be determined from Table 308.5.4-2.
308.5.3 IMPORTANCE FACTOR, Is
The value for Is shall be determined from Table 305.3-1. based on the Risk Category from Table
305.1-1.
308.5.4 MINIMUM SNOW LOAD FOR LOW-SLOPE ROOFS, pm
A minimum roof snow load, pm, shall only apply to monoslope, hip and gable roofs with slopes
less than 15°, and to curved roofs where the vertical angle from the eaves to the crown is less
than 10°. The minimum roof snow load for low-slope roofs shall be obtained using the following
formula:
Where pg is 1.00 kN/m2 or less:
pm = Ispg (Importance factor times pg)
Where pg exceeds 1.00 kN/m2:
pm = 1,00 (Is ) (1.00 kN/m times Importance Factor)
This minimum roof snow load is a separate uniform load case. It need not be used in
determining or in combination with drift, sliding, unbalanced, or partial loads.
TABLE 308.5.4-1 EXPOSURE FACTOR, Ce
Terrain Category
B see section 309.4
C see section 309.4
D see section 309.4
Above the treeline in windswept mountainous areas.
All rights reserved
Fully exposed
0.9
0.9
0.8
0.7
Exposure of roof
Partially exposed
1.0
1.0
0.9
0.8
Sheltered
1.2
1.1
1.0
N/A
55 / 496
TABLE 308.5.4-2 THERMAL FACTOR, Ct
Thermal Condition
All structures except as indicated below
Structures kept just above freezing and others with cold, ventilated roofs in which the thermal resistance (Rvalue) between the ventilated space and the heated space exceeds 4.4 K × m2/W.
Unheated and open air structures
Structures intentionally kept below freezing
Continuously heated greenhousesb with a roof having a thermal resistance (R-value) less than 0.4 K × m2/W
Ct
1.0
1.1
1.2
1.3
0.85
308.6 SLOPPED ROOF SNOW LOADS, ps
Snow loads acting on a sloping surface shall be assumed to act on the horizontal projection of that
surface. The sloped roof (balanced) snow load, ps, shall be obtained by multiplying the flat roof snow
load, pf, by the roof slope factor, Cs:
ps = Cspf
EQUATION 308.6-1
Values of Cs for warm roofs, cold roofs, curved roofs, and multiple roofs are determined from Sections
308.6.1 through 308.6.4. The thermal factor, Ct, from Table 308.5.4-2 determines if a roof is “cold” or
“warm.” “Slippery surface” values shall be used only where the roof’s surface is unobstructed and suffi
cient space is available below the eaves to accept all the sliding snow. A roof shall be considered
unobstructed if no objects exist on it that prevent snow on it from sliding. Slippery surfaces shall
include metal, slate, glass, and bituminous, rubber, and plastic membranes with a smooth surface.
Membranes with an imbedded aggregate or mineral granule surface shall not be considered smooth.
Asphalt shingles, wood shingles, and shakes shall not be considered slippery.
308.6.1 WARM ROOF SLOPE FACTOR, Cs
For warm roofs (Ct ≤ 1.0 as determined from Table 308.5.4-2 with an unobstructed slippery
surface that will allow snow to slide off the eaves, the roof slope factor Cs shall be determined
using the dashed line in Figure 308-1a, provided that for nonventilated warm roofs, their
thermal resistance (R-value) equals or exceeds 5.3 °C m2/W and for warm ventilated roofs, their
R-value equals or exceeds 3.5 °C m2/W. Exterior air shall be able to circulate freely under a
ventilated roof from its eaves to its ridge. For warm roofs that do not meet the aforementioned
conditions, the solid line in Figure 308-1 shall be used to determine the roof slope factor Cs.
308.6.2 COLD ROOF SLOPE FACTOR, Cs
Cold roofs are those with a Ct > 1.0 as determined from Table 308.5.4-2. For cold roofs with Ct =
1.1 and an unobstructed slippery surface that will allow snow to slide off the eaves, the roof
slope factor Cs shall be determined using the dashed line in Figure 308-1b. For all other cold
roofs with Ct = 1.1, the solid line in Figure 308-1b shall be used to determine the roof slope
factor Cs. For cold roofs with Ct = 1.2 and an unobstructed slippery surface that will allow snow
to slide off the eaves, the roof slope factor Cs shall be determined using the dashed line on
Figure 308-1c. For all other cold roofs with Ct = 1.2, the solid line in Figure 308-1c shall be used
to determine the roof slope factor Cs.
308.6.3 ROOF SLOPE FACTOR CURVED ROOFS
Portions of curved roofs having a slope exceeding 70° shall be considered free of snow load (i.e.,
Cs = 0). Balanced loads shall be determined from the balanced load diagrams in Figure 308-2
with Cs determined from the appropriate curve in in Figure 308-1.
All rights reserved
56 / 496
308.6.4 ROOF SLOPE FACTOR FOR MULTIPLE FOLDED PLATE, SAWTOOTH, AND BARREL VAULT
ROOFS
Multiple folded plate, sawtooth, or barrel vault roofs shall have a Cs = 1.0, with no reduction in
snow load because of slope (i.e., ps = pf).
308.6.5 ICE DAMS AND ICECLES ALONG EAVES
Two types of warm roofs that drain water over their eaves shall be capable of sustaining a
uniformly distributed load of 2pf on all overhanging portions: those that are unventilated and
have an R-value less than 5.3 °C m2/W and those that are ventilated and have an R-value less
than 3.5 °C m2/W. The load on the overhang shall be based upon the flat roof snow load for the
heated portion of the roof up-slope of the exterior wall. No other loads except dead loads shall
be present on the roof when this uniformly distributed load is applied.
308.7 PARTIAL LOADING
The effect of having selected spans loaded with the balanced snow load and remaining spans loaded
with half the balanced snow load shall be investigated as follows:
308.7.1 CONTINUOUS BEAM SYSTEMS
Continuous beam systems shall be investigated for the effects of the three loadings shown in
Figure 308-3:
Case 1: Full balanced snow load on either exterior span and half the balanced snow load on
all other spans.
Case 2: Half the balanced snow load on either exterior span and full balanced snow load on
all other spans.
Case 3: All possible combinations of full balanced snow load on any two adjacent spans and
half the balanced snow load on all other spans. For this case there will be (n –1) possible
combinations where n equals the number of spans in the continuous beam system.
If a cantilever is present in any of the above cases, it shall be considered to be a span.
Partial load provisions need not be applied to structural members that span perpendicular to
the ridgeline in gable roofs with slopes of 2.38˚ (½ on 12) and greater.
308.7.2 OTHER STRUCTURAL SYSTEMS
Areas sustaining only half the balanced snow load shall be chosen so as to produce the greatest
effects on members being analyzed.
308.8 UNBALANCED ROOF SNOW LOADS
Balanced and unbalanced loads shall be analyzed separately. Winds from all directions shall be
accounted for when establishing unbalanced loads.
308.8.1 UNBALANCED SNOW LOADS FOR HIP AND GABLE ROOFS
For hip and gable roofs with a slope exceeding 7 on 12 (30.2°) or with a slope less than 2.38° (½
on 12) unbalanced snow loads are not required to be applied. Roofs with an eave to ridge
distance, W, 6.0 m or less, having simply supported prismatic members spanning from ridge to
eave shall be designed to resist an unbalanced uniform snow load on the leeward side equal to
Ipg. For these roofs the windward side shall be unloaded. For all other gable roofs, the
unbalanced load shall consist of 0.3ps on the windward side, ps on the leeward side plus a
rectangular surcharge with magnitude hd / √ and horizontal extent from the ridge 8 √
/3
where hd is the drift height from Figure 308-8 with lu equal to the eave to ridge distance for the
windward portion of the roof, W. For W less than 6.0 m, use W = lu = 6.0 m in Figure 308-8.
Balanced and unbalanced loading diagrams are presented in Figure 308-4.
All rights reserved
57 / 496
308.8.2 UNBALANCED SNOW LOADS FOR CURVED ROOFS
Portions of curved roofs having a slope exceeding 70° shall be considered free of snow load. If
the slope of a straight line from the eaves (or the 70° point, if present) to the crown is less than
10° or greater than 60°, unbalanced snow loads shall not be taken into account.
Unbalanced loads shall be determined according to the loading diagrams in Figure 308-2. In all
cases the windward side shall be considered free of snow. If the ground or another roof abuts a
Case II or Case III (see Figure 308-2) curved roof at or within 0.91 m of its eaves, the snow load
shall not be decreased between the 30° point and the eaves, but shall remain constant at the
30° point value. This distribution is shown as a dashed line in Figure 308-2.
308.8.3 UNBALANCED SNOW LOADS FOR MULTIPLE FLODED PLATE, SAWTOOTH, AND BARREL
VAULT ROOFS
Unbalanced loads shall be applied to folded plate, sawtooth, and barrel-vaulted multiple roofs
with a slope exceeding 1.79°. According to Section 308.6.4, Cs = 1.0 for such roofs, and the
balanced snow load equals pf. The unbalanced snow load shall increase from one-half the
balanced load at the ridge or crown (i.e., 0.5pf) to two times the balanced load given in Section
308.6.4 divided by Ce at the valley (i.e., 2pf/Ce). Balanced and unbalanced loading diagrams for a
sawtooth roof are presented in Figure 308-5. However, the snow surface above the valley shall
not be at an elevation higher than the snow above the ridge. Snow depths shall be determined
by dividing the snow load by the density of that snow from Equation 308.9.1-1, which is in
Section 308.9.1.
308.8.4 UNBALANCED SNOW LOADS FOR DOME ROOFS
Unbalanced snow loads shall be applied to domes and similar rounded structures. Snow loads,
determined in the same manner as for curved roofs in Section 308.8.2, shall be applied to the
downwind 90° sector in plan view. At both edges of this sector, the load shall decrease linearly
to zero over sectors of 22.5° each. There shall be no snow load on the remaining 225° upwind
sector.
308.9 DRIFTS ON LOWER ROOFS (AERODYNAMIC SHADE)
Roofs shall be designed to sustain localized loads from snowdrifts that form in the wind shadow of (1)
higher portions of the same structure and (2) adjacent structures and terrain features.
308.9.1 LOWER ROOF OF A STRUCTURE
Snow that forms drifts comes from a higher roof or, with the wind from the opposite direction,
from the roof on which the drift is located. These two kinds of drifts (“leeward” and “windward”
respectively) are shown in Figure 308-6. The geometry of the surcharge load due to snow drifting
shall be approximated by a triangle as shown in Figure 308-7. Drift loads shall be superimposed
on the balanced snow load. If hc/hb is less than 0.2, drift loads are not required to be applied.
For leeward drifts, the drift height hd shall be determined directly from Figure 308-8 using the
length of the upper roof. For windward drifts, the drift height shall be determined by substituting
the length of the lower roof for lu in Figure 308-8 and using three-quarters of hd as determined
from Figure 308-8 as the drift height. The larger of these two heights shall be used in design. If
this height is equal to or less than hc, the drift width, w, shall equal 4hd and the drift height shall
equal hd. If this height exceeds hc, the drift width, w, shall equal 4hd2/hc and the drift height shall
equal hc. However, the drift width, w, shall not be greater than 8hc. If the drift width, w, exceeds
the width of the lower roof, the drift shall be truncated at the far edge of the roof, not reduced to
zero there. The maximum intensity of the drift surcharge load, pd, equals hd where snow
density, , is defined in Equation 308.9.1-1:
 = 0.426pg + 2.2 but not more than 4.7 kN/m3
EQUATION 308.9.1-1
All rights reserved
58 / 496
This density shall also be used to determine hb by dividing ps by  (also multiply by 102 to get the
depth in m).
308.9.2 ADJACENT STRUCTURES
If the horizontal separation distance between adjacent structures, s, is less than 6.0 m and less
than six times the vertical separation distance (s < 6h), then the requirements for the leeward
drift of Section 308.9.1 shall be used to determine the drift load on the lower structure. The
height of the snow drift shall be the smaller of hd, based upon the length of the adjacent higher
structure, and (6h – s)/6. The horizontal extent of the drift shall be the smaller of 6hd or (6h – s).
For windward drifts, the requirements of Section 308.9.1 shall be used. The resulting drift is
permitted to be truncated.
308.10 ROOF PROJECTIONS AND PARAPETS
The method in Section 308.9.1 shall be used to calculate drift loads on all sides of roof projections and
at parapet walls. The height of such drifts shall be taken as three-quarters the drift height from Figure
308-8 (i.e., 0.75hd). For parapet walls, lu shall be taken equal to the length of the roof upwind of the
wall. For roof projections, lu shall be taken equal to the greater of the length of the roof upwind or
downwind of the projection. If the side of a roof projection is less than 4.6 m long, a drift load is not
required to be applied to that side.
308.11 SLIDING SNOW
The load caused by snow sliding off a sloped roof onto a lower roof shall be determined for slippery
upper roofs with slopes greater than 6.25 on 300, and for other (i.e., nonslippery) upper roofs with
slopes greater than 2 on 12. The total sliding load per unit length of eave shall be 0.4pfW, where W is
the horizontal distance from the eave to ridge for the sloped upper roof. The sliding load shall be
distributed uniformly on the lower roof over a distance of 4.6 m from the upper roof eave. If the width
of the lower roof is less than 4.6 m, the sliding load shall be reduced proportionally. The sliding snow
load shall not be further reduced unless a portion of the snow on the upper roof is blocked from
sliding onto the lower roof by snow already on the lower roof. For separated structures, sliding loads
shall be considered when h/s > 1 and s < 4.6 m. The horizontal extent of the sliding load on the lower
roof shall be 4.6 – s with s in meters, and the load per unit length shall be 0.4pfW (4.6 – s)/4.6 with s in
meters. Sliding loads shall be superimposed on the balanced snow load and need not be used in
combination with drift, unbalanced, partial, or rain-on-snow loads.
308.12 RAIN-ON-SNOW SURCHARGE LOAD
For locations where pg is 1.00 kN/m2 or less, but not zero, all roofs with slopes (in degrees) less than
W/50 with W/15.2 with W in m shall include a 0.24 kN/m2 rain-on-snow surcharge load. This additional
load applies only to the sloped roof (balanced) load case and need not be used in combination with
drift, sliding, unbalanced, minimum, or partial loads.
308.13 PONDING INSTABILITY
Roofs shall be designed to preclude ponding instability. For roofs with a slope less than (1.19˚) and
roofs where water can be impounded, roof deflections caused by full snow loads shall be evaluated
when determining the likelihood of ponding instability (see Section 310.2).
308.14 EXISTING ROOFS
Existing roofs shall be evaluated for increased snow loads caused by additions or alterations. Owners
or agents for owners of an existing lower roof shall be advised of the potential for increased snow
loads where a higher roof is constructed within 6.0 m. See footnote to Table 308.5.4-1 and Section
308.9.2.
All rights reserved
59 / 496
FIGURE 308-1 GRAPHS FOR DETERMINING ROOF SLOPE FACTOR Cs, FOR WARM AND COLD ROOFS
SEE TABLE 308.5.4-2
FIGURE 308-1a
FIGURE 308-1b
All rights reserved
60 / 496
FIGURE 308-1c
All rights reserved
61 / 496
FIGURE 308-2 BALANCED AND UNBALANCED LOADS FOR CURVED ROOFS
All rights reserved
62 / 496
FIGURE 308-3 PARTIAL LOADING DIAGRAMS FOR CONTINUOUS BEAMS
All rights reserved
63 / 496
FIGURE 308-4 BALANCED AND UNBALANCED SNOW LOADS FOR HIP AND GABLE ROOFS
FIGURE 308-5 BALANCED AND UNBALANCED SNOW LOADS FOR A SAWTOOTH ROOF
All rights reserved
64 / 496
FIGURE 308-6 DRIFTS FORMED AT WINDWARD AND LEEWARD STEPS
FIGURE 308-7 CONFIGURATION OF SNOW DRIFTS ON LOWER ROOFS
FIGRUE 308-8 GRAPH AND EQUATION FOR DETERMINING DRIFT HEIGHT, hd
All rights reserved
65 / 496
SECTION 309 WIND LOADS
309.1 SCOPE
Buildings, structures, including the Main Wind-Force Resisting System (MWFRS) and all components
and cladding (C&C) thereof shall be designed to withstand the minimum wind loads prescribed
herein. Decreases in wind loads shall not be made for the effect of shielding by other structures.
309.1.1 DETERMINATION OF WIND LOADS
Wind loads on every building or structure shall be determined in accordance with provisions of
the alternate all-heights method in Section 309.10. The type of opening protection required, the
basic wind speed and the exposure category for a site is permitted to be determined in
accordance with Section 309. Wind shall be assumed to come from any horizontal direction and
wind pressures shall be assumed to act normal to the surface considered.
309.1.2 PERMITTED PROCEDURES
The design wind loads for buildings and other structures, including the MWFRS and component
and cladding elements thereof, shall be determined using one of the procedures as specified in
this section.
309.2 NOTATIONS
Coefficients and variables used in the alternative all-heights method equations are as follows:
A = effective wind area, in m2
Af = area of open buildings and other structures either normal to the wind direction or projected on a
plane normal to the wind direction, in m2
Ag = the gross area of that wall in which Ao is identified, in m2
Agi = the sum of the gross surface areas of the building envelope (walls and roof)not including Ag,m
2
2
Ao = total area of openings in a wall that receives positive external pressure, in m
Aoi = the sum of the areas of openings in the building envelope(walls and roof)not including Ao, m
Aog = total area of openings in the building envelope in m
2
2
2
As = gross area of the solid freestanding wall or solid sign, in m
a = width of pressure coefficient zone, in m
B = horizontal dimension of building measured normal to wind direction, in m
= mean hourly wind speed factor in Equation 309.12.5-8 from Table 309.12.7-1.
ˆ = 3-s gust speed factor from Table 309.12.7-1.
Cf = force coefficient to be used in determination of wind loads for other structures
CN = net pressure coefficient to be used in determination of wind loads for open buildings
Cp = external pressure coefficient to be used in determination of wind loads for buildings
c = turbulence intensity factor in Equation 309.12.4-2 from Table 309.12.7-1.
D = diameter of a circular structure or member, in m
D´ = depth of protruding elements such as ribs and spoilers, in m
F = design wind force for other structures, in N
G = gust-effect factor
Gf = gust-effect factor for MWFRS of flexible buildings and other structures
(GCpn) = combined net pressure coefficient for a parapet
(GCp) = product of external pressure coefficient and gust-effect factor to be used in determination of
wind loads for buildings
(GCpf) = product of the equivalent external pressure coefficient and gust-effect factor to be used in
determination of wind loads for MWFRS of low-rise buildings
All rights reserved
66 / 496
(GCpi) = product of internal pressure coefficient and gust-effect factor to be used in determination of
wind loads for buildings
(GCr) = product of external pressure coefficient and gust-effect factor to be used in determination of
wind loads for rooftop structures
gQ = peak factor for background response in Equations 309.12.4-1 and 309.12.5-1
gR = peak factor for resonant response in Equation 309.12.5-1.
gv = peak factor for wind response in Equations 309.12.4-1 and 309.12.5-1.
H = height of hill or escarpment in Figure 309.11.1-1, in m
h = mean roof height of a building or height of other structure, except that eave height shall be used
for roof angle θ less than or equal to 10°, in m
he = roof eave height at a particular wall, or the average height if the eave varies along the wall
hp = height to top of parapet
I = intensity of turbulence from Equation 309.12.4-2
K1, K2, K3 = multipliers in Figure 309.11.1-1 to obtain Kzt
Kd = wind directionality factor in Table 309.4-1
Kh = velocity pressure exposure coefficient evaluated at height z = h
Kz = velocity pressure exposure coefficient evaluated at height z
Kzt = topographic factor as defined in Section 309.11
L = horizontal dimension of a building measured parallel to the wind direction, in m
Lh = distance upwind of crest of hill or escarpment in Figure 309.11.1-1 to where the difference in
ground elevation is half the height of the hill or escarpment, in m
Lz = integral length scale of turbulence, in m
Lr = horizontal dimension of return corner for a solid freestanding wall from, in m
l = integral length scale factor from Table 309.12.7-1, m
N1 = reduced frequency from Equation 309.12.5-5
na = approximate lower bound natural frequency (Hz) from Section 309.12.2
n1 = fundamental natural frequency, Hz
p = design pressure to be used in determination of wind loads for buildings, in N/m2
PL = wind pressure acting on leeward face in Figure 309.15.3.7-6, in N/m2
pnet = net design wind pressure from, in N/m2
pnet30 = net design wind pressure for Exposure B at h = 9 m and I = 1.0 from, in N/m2
pp = combined net pressure on a parapet from Equation 309.15.3.6-1, in N/m2
ps = net design wind pressure from Equation 309.17.6.3-1, in N/m
2
ps30 = simplified design wind pressure for Exposure B at h = 90 m and I = 1.0 from Figure 309.17.6.4-1,
N/m2
2
PW = wind pressure acting on windward face in Figure 309.15.3.7-6, in N/m
Q = background response factor from Equation 309.12.4-3
2
q = velocity pressure, in N/m
qh = velocity pressure evaluated at height
z = h, in N/m
2
qi = velocity pressure for internal pressure determination, in N/m
qp = velocity pressure at top of parapet, in N/m
2
2
qz = velocity pressure evaluated at height z above ground, in N/m
R = resonant response factor from Equation 309.12.5-3
All rights reserved
2
67 / 496
RB, Rh, RL = values from Equations 309.12.5-6 and 309.12.5-7
Ri = reduction factor from Equation 309.14.1.1-1
s = vertical dimension of the solid freestanding wall or solid sign, in m
r = rise-to-span ratio for arched roofs
V = basic wind speed, in m/s. The basic wind speed corresponds to a 3-sec gust speed at 10 m above
the ground in Exposure Category C
3
Vi = unpartitioned internal volume, m
= mean hourly wind speed at height z m/s
W = width of building in and width of span, in m
x = distance upwind or downwind of crest in Figure 309.11.1-1, in m
z = height above ground level, in m
= equivalent height of structure, in m
zg = nominal height of the atmospheric boundary layer used in this standard. Values appear in Table
309.12.7-1
zmin = exposure constant from Table 309.12.7-1
a = 3-sec gust-speed power law exponent from Table 309.12.7-1
aˆ = reciprocal of a from Table 309.12.7-1
= mean hourly wind-speed power law exponent in Equation 309.12.5-8 from Table 309.12.7-1
β = damping ratio, percent critical for buildings or other structures
= ratio of solid area to gross area for solid freestanding wall, solid sign, open sign, face of a trussed
tower, or lattice structure
 = adjustment factor for building height and exposure from Figure 309.17.6.4-1
= integral length scale power law exponent in Equation 309.12.4-4 from Table 309.12.7-1
 = value used in Equations 309.12.5-6 and 309.12.5-7
θ = angle of plane of roof from horizontal, in degrees
v = height-to-width ratio for solid sign
309.3 BASIC WIND SPEED
The basic wind speed, in m/s, for the determination of the wind loads shall be determined by Tables
309.3-1, 309.1-2 and 309.1-3. Basic wind speed for the special wind regions indicated, near
mountainous terrain and near gorges shall be in accordance with local jurisdiction requirements. Basic
wind speeds determined by the local jurisdiction shall be in accordance with Section 309.3.
TABLE 309.3-1 BASIC WIND SPEED FOR OCCUPANCY CATEGORY II BUILDINGS AND OTHER
STRUCTURES
LOCATION
Baghlan
Bamyan
Chackaharam
Chardara
Darulaman
Darwaz
Deshu
Eshkashem
Faizabad
Farah
Gardez
Ghazni
Ghelmin
Gazeabad
All rights reserved
WIND SPEED (m/s)
30
40
20
30
30
30
40
30
40
50
40
30
30
30
LOCATION
Kunduz
Laghman
Lal
Lashkargah
Logar
Maimana
Mazarisherif
Mokar
M. B. Cot
Nawer
North Salang
Orgon
Paghman
Panjab
WIND SPEED (m/s)
40
40
30
40
40
30
40
30
30
20
40
30
30
20
68 / 496
Herat
Jabulsaraj
Jalalabad
Khwajaghar
Kabul
Kalat
Kandahar
Karizimir
Khost
Khahn
40
30
40
40
50
30
40
30
30
20
Salang
Qadis
Sheghnan
Shahrark
Sheberghan
Sarabi
Talikan
Tirinkot
Zaranj
40
30
40
40
50
30
40
20
30
TABLE 309.3-2 BASIC WIND SPEED FOR OCCUPANCY CATEGORY III & IV BUILDINGS AND OTHER
STRUCTURES
LOCATION
Baghlan
Bamyan
Chackaharam
Chardara
Darulaman
Darwaz
Deshu
Eshkashem
Faizabad
Farah
Gardez
Ghazni
Ghelmin
Gazeabad
Herat
Jabulsaraj
Jalalabad
Khwajaghar
Kabul
Kalat
Kandahar
Karizimir
Khost
Khahn
WIND SPEED (m/s)
33
43
23
33
33
33
43
33
43
53
43
33
33
33
43
33
43
43
53
33
43
33
33
23
LOCATION
Kunduz
Laghman
Lal
Lashkargah
Logar
Maimana
Mazarisherif
Mokar
M. B. Cot
Nawer
North Salang
Orgon
Paghman
Panjab
Salang
Qadis
Sheghnan
Shahrark
Sheberghan
Sarabi
Talikan
Tirinkot
Zaranj
WIND SPEED (m/s)
43
43
33
43
43
33
43
33
33
23
43
33
33
23
43
33
43
43
53
33
43
23
33
TABLE 309.3-3 BASIC WIND SPEED FOR OCCUPANCY CATEGORY I BUILDINGS AND OTHER
STRUCTURES
LOCATION
Baghlan
Bamyan
Chackaharam
Chardara
Darulaman
Darwaz
Deshu
Eshkashem
All rights reserved
WIND SPEED (m/s)
36
46
26
36
36
36
46
36
LOCATION
Kunduz
Laghman
Lal
Lashkargah
Logar
Maimana
Mazarisherif
Mokar
WIND SPEED (m/s)
46
46
36
46
46
36
46
36
69 / 496
Faizabad
Farah
Gardez
Ghazni
Ghelmin
Gazeabad
Herat
Jabulsaraj
Jalalabad
Khwajaghar
Kabul
Kalat
Kandahar
Karizimir
Khost
Khahn
43
56
46
36
36
36
46
36
46
46
56
36
46
36
36
26
M. B. Cot
Nawer
North Salang
Orgon
Paghman
Panjab
Salang
Qadis
Sheghnan
Shahrark
Sheberghan
Sarabi
Talikan
Tirinkot
Zaranj
36
26
46
36
36
26
46
36
46
46
56
36
46
26
36
309.4. WIND DIRECTIONS AND SECTORS
For each selected wind direction at which the wind loads are to be evaluated, the exposure of the
building or structure shall be determined for the two upwind sectors extending 45 degrees either side of
the selected wind direction. The exposures in these two sectors shall be determined in accordance with
Sections 309.5 and 309.6 and the exposure resulting in the highest wind loads shall be used to
represent winds from that direction.
The wind directionality factor, Kd, shall be determined from Table 309.4-1. This directionality factor
shall only be included in determining wind loads when the load combinations specified in Section 302.3
and 302.4 are used for the design.The effect of wind directionality in determining wind loads shall be
based on an analysis for wind speeds.
TABLE 309.4-1 Wind Directionality Factor, K d
Structure Type
Directionality Factor Kd*
Buildings
Main Wind Force Resisting System
Components and Cladding
0.85
0.85
Arched Roofs
0.85
Chimneys, Tanks, and Similar Structures
Square
Hexagonal
Round
0.90
0.95
0.95
Solid Freestanding Walls and Solid
Freestanding and Attached Signs
0.85
Open Signs and Lattice Framework
0.85
Trussed Towers
Triangular, square, rectangular
0.85
All other cross sections
0.95
*Directionality Factor Kd has been calibrated with combinations of loads specified in this chapter. This
factor shall only be applied when used in conjunction with load combinations specified in Sections 302.3
and 302.4.
All rights reserved
70 / 496
309.5 SURFACE ROUGHNESS CATEGORIES
A ground surface roughness within each 45-degree sector shall be determined for a distance upwind
of the site as defined in Section 309.6 from the categories defined below, for the purpose of assigning
an exposure category as defined in Section 309.6.
Surface Roughness B. Urban and suburban areas, wooded areas or other terrain with
numerous closely spaced obstructions having the size of single-family dwellings or larger.
Surface Roughness C. Open terrain with scattered obstructions having heights generally less
than 9000 mm. This category includes flat open country, grasslands.
Surface Roughness D. Flat, unobstructed areas and water surfaces. This category includes
smooth mud flats, salt flats and unbroken ice.
309.6 EXPOSURE CATEGORIES
An exposure category shall be determined in accordance with the following:
Exposure B. Exposure B shall apply where the ground surface roughness condition, as defined
by Surface Roughness B, prevails in the upwind direction for a distance of at least 800 m or 20
times the height of the building, whichever is greater.
Exception: For buildings whose mean roof height is less than or equal to 9000 mm, the
upwind distance is permitted to be reduced to 450 m.
Exposure C. Exposure C shall apply for all cases where Exposures B or D does not apply.
Exposure D. Exposure D shall apply where the ground surface roughness, as defined by Surface
Roughness D, prevails in the upwind direction for a distance of at least 1500 m or 20 times the
height of the building, whichever is greater.
309.7 EXPOSURE REQUIREMENTS
309.7.1 DIRECTIONAL PROCEDURE
For each wind direction considered, wind loads for the design of the MWFRS of enclosed and
partially enclosed buildings using the Directional Procedure of Section 309 shall be based on the
exposures as defined in Section 309.6. Wind loads for the design of open buildings with
monoslope, pitched, or troughed free roofs shall be based on the exposures, as defined in
Section 309.6, resulting in the highest wind loads for any wind direction at the site.
309.7.2 ENVELOPE PROCEDURE
Wind loads for the design of the MWFRS for all low-rise buildings designed using the Envelope
Procedure of Section 309.17 shall be based on the exposure category resulting in the highest
wind loads for any wind direction at the site.
309.7.3 DIRECTIONAL PROCEDURE FOR BUILDING APPURTENANCES AND OTHER STRUCTURES
Wind loads for the design of building appurtenances (such as rooftop structures and equipment)
and other structures (such as solid freestanding walls and freestanding signs, chimneys, tanks,
open signs, lattice frameworks, and trussed towers) shall be based on the appropriate exposure
for each wind direction considered.
309.8 COMPONENTS AND CLADDING
Design wind pressures for components and cladding shall be based on the exposure category resulting
in the highest wind loads for any wind direction at the site.
309.9 ROOF SYSTEMS
309.9.1 ROOF DECK
The roof deck shall be designed to withstand the wind pressures determined in accordance with
Section 309.
All rights reserved
71 / 496
309.9.2 ROOF COVERINGS
Roof coverings shall comply with Section 309.9.1.
309.10 ALTERNATE ALL-HEIGHTS METHOD
309.10.1 SCOPE
The following provisions are permitted to be used to determine the wind effects on regularly
shaped buildings, or other structures that are regularly shaped, which meet all of the following
conditions:
1. The building or other structure is less than or equal to 22.000 mm in height with a heightto-least- width ratio of 4 or less, or the building or other structure has a fundamental
frequency greater than or equal to 1 hertz.
2. The building or other structure is not sensitive to dynamic effects.
3. The building or other structure is not located on a site for which channeling effects or
buffeting in the wake of upwind obstructions warrant special consideration.
4. The building shall meet the requirements of a simple diaphragm building where wind
loads are only transmitted to the main wind-force-resisting system (MWFRS) at the
diaphragms.
5. For open buildings, multispan gable roofs, stepped roofs, sawtooth roofs, domed roofs,
roofs with slopes greater than 45 degrees (0.79 rad), solid free-standing walls and solid
signs, and rooftop equipment, apply the provisions of Section 309.
309.10.2 DESIGN EQUATIONS
When using the alternative all-heights method, the MWFRS, and components and cladding of
every structure shall be designed to resist the effects of wind pressures on the building envelope
in accordance with Equation 309.10.2-1.
Pnet = qs Kz Cnet [IKzt]
EQUATION 309.10.2-1
Design wind forces for the MWFRS shall not be less than 0.48 kN/m2 multiplied by the area of the
structure projected on a plane normal to the assumed wind direction. Design net wind pressure
for components and cladding shall not be less than 0.48 kN/m2 acting in either direction normal
to the surface.
309.10.3 DESIGN PROCEDURE
The MWFRS and the components and cladding of every building or other structure shall be
designed for the pressures calculated using Equation 309.10.2-1.
309.10.3.1 MAIN WIND-FORCE-RESISTING SYSTEMS
The MWFRS shall be investigated for the torsional effects identified in Figure 309.15.3.7-6.
309.10.3.2 DETERMINATION OF KZ AND KZT
Velocity pressure exposure coefficient, Kz, shall be determined in accordance with Section
309.15.2.1 and the topographic factor, Kzt, shall be determined in accordance with Section
309.11.
1. For the windward side of a structure, Kzt and Kz shall be based on height z.
2. For leeward and sidewalls, and for windward and leeward roofs, Kzt and Kz shall be
based on mean roof height h.
All rights reserved
72 / 496
TABLE 309.10.3.2-1 WIND VELOCITY PRESSURE (qs) AT STANDARD HEIGHT OF 10 m
BASIC WIND SPEED (m/s)
PRESSURE, qs (kPa)
38
0.89
40
1.00
44
1.23
46
1.35
48
1.48
TABLE 309.10.3.2-2 NET PRESSURE COEFFICIENTS, , Cnet
STRUCTURE OR PART
THEREOF
DESCRIPTION
Walls:
Windward wall
Leeward wall
Sidewall
1. Main wind- forceresisting frames and
systems
53
1.77
57
2.07
62
2.40
66
2.75
70
3.15
75
3.55
a, b
Cnet FACTOR
Enclosed
Partially enclosed
+Internal pressure -Internal pressure +Internal pressure -Internal pressure
0.43
0.73
0.11
1.05
-0.51
-0.21
-0.83
0.11
-0.66
-0.35
-0.97
-0.04
1.28
1.28
-0.85
-0.85
Enclosed
Partially enclosed
+Internal pressure -Internal pressure +Internal pressure -Internal pressure
-0.66
-0.35
-0.97
-0.04
Windward
Parapet wall
Leeward
Roofs:
Wind perpendicular to ridge
Leeward roof or flat roof
Windward roof slopes:
Condition 1
-1.09
-0.79
-1.41
Slope < 2:12 (10°)
Condition 2
-0.28
0.02
-0.60
Condition 1
-0.73
-0.42
-1.04
Slope = 4:12 (18°)
Condition 2
-0.05
0.25
-0.37
Condition 1
-0.58
-0.28
-0.90
Slope = 5:12 (23°)
Condition 2
0.03
0.34
-0.29
Condition 1
-0.47
-0.16
-0.78
Slope = 6:12 (27°)
Condition 2
0.06
0.37
-0.25
Condition 1
-0.37
-0.06
-0.68
Slope = 7:12 (30°)
Condition 2
0.07
0.37
-0.25
Condition 1
-0.27
0.04
-0.58
Slope 9:12 (37°)
Condition 2
0.14
0.44
-0.18
Slope 12:12 (45°)
0.14
0.44
-0.18
Wind parallel to ridge and flat roofs
-1.09
-0.79
-1.41
Nonbuilding Structures: Chimneys, Tanks and Similar Structures:
h/D
1
7
Square (Wind normal to face)
0.99
1.07
Square (Wind on diagonal)
0.77
0.84
Hexagonal or Octagonal
0.81
0.97
Round
0.65
0.81
Open signs and lattice frameworks
Ratio of solid to gross area
< 0.1
0.1 to 0.29
Flat
1.45
1.30
Round
0.87
0.94
TABLE 309.10.3.2-2 NET PRESSURE COEFFICIENTS, , Cnet
a, b
-0.47
0.34
-0.11
0.57
0.04
0.65
0.15
0.68
0.25
0.69
0.35
0.76
0.76
-0.47
25
1.53
1.15
1.13
0.97
0.3 to 0.7
1.16
1.08
continued
STRUCTURE OR PART
DESCRIPTION
THEREOF
Roof elements and slopes
Gable of hipped configurations (Zone 1)
Flat < Slope < 6:12 (27°)
1 square meter or less
Positive
10 square meter or more
1 square meter or less
Negative
10 square meter or more
2. Components and
cladding not in areas Overhang: Flat < Slope < 6:12 (27°)
of discontinuity—roofs
1 square meter or less
and overhangs
Negative
10 square meter or more
45 square meter or more
6:12 (27°) < Slope < 12:12 (45°)
1 square meter or less
Positive
10 square meter or more
1 square meter or less
Negative
10 square meter or more
All rights reserved
55
1.92
a
Cnet FACTOR
Enclosed
Partially enclosed
0.58
0.41
-1.00
-0.92
0.89
0.72
-1.32
-1.23
-1.45
-1.36
-0.94
0.92
0.83
-1.00
-0.83
1.23
1.15
-1.32
-1.15
73 / 496
Monosloped configurations (Zone 1)
Flat < Slope < 7:12 (30°)
1 square meter or less
10 square meter or more
1 square meter or less
10 square meter or more
Positive
Negative
Tall flat-topped roofs h 60
Flat < Slope < 2:12 (10°) (Zone 1)
Partially enclosed
0.49
0.41
-1.26
-1.09
Enclosed
0.81
0.72
-1.57
-1.40
Partially enclosed
1 square meter or less
-1.34
45 square meter or more -0.92
Negative
TABLE 309.10.3.2-2 NET PRESSURE COEFFICIENTS, , Cnet
STRUCTURE OR PART
THEREOF
Enclosed
a, b
-1.66
-1.23
continued
Cnet FACTOR
DESCRIPTION
Roof elements and slopes
Enclosed
Gable or hipped configurations at ridges, eaves and rakes (Zone 2)
Flat < Slope < 6:12 (27°)
1 square meter or less
0.58
Positive
10 square meter or more 0.41
1 square meter or less
-1.68
Negative
10 square meter or more -1.17
Overhang for Slope Flat < Slope < 6:12 (27°)
1 square meter or less
-1.87
Negative
10 square meter or more -1.87
6:12 (27°) < Slope < 12:12 (45°) Figure 6-11D
Enclosed
1 square meter or less
0.92
Positive
10 square meter or more 0.83
10 square feet or less
-1.17
Negative
10 square meter or more -1.00
3. Components and clad- Overhang for 6:12 (27°) < Slope < 12:12 (45°)
1 square meter or less
-1.70
ding in areas of
Negative
discontinuities—roofs
45 square meter or more -1.53
and overhangs
Monosloped configurations at ridges, eaves and rakes (Zone 2)
Flat < Slope < 7:12 (30°)
1 square meter or less
0.49
Positive
10 square meter or more 0.41
1 square meter or less
-1.51
Negative
10 square meter or more -1.43
Tall flat topped roofs h > 60
Enclosed
Flat < Slope < 2:12 (10°) (Zone 2)
1 square meter or less
-2.11
Negative
45 square meter or more -1.51
Gable or hipped configurations at corners (Zone 3)
Flat < Slope < 6:12 (27°)
Enclosed
1 square meter or less
0.58
Positive
10 square meter or more 0.41
1 square meter or less
-2.53
Negative
10 square meter or more -1.85
TABLE 309.10.3.2-2 NET PRESSURE COEFFICIENTS, , Cnet
STRUCTURE OR PART THEREOF
3. Components and cladding in
areas of discontinuity—roofs and
overhangs
(continued)
All rights reserved
a, b
Partially enclosed
0.89
10.72
-2.00
-1.49
Partially enclosed
1.23
1.15
-1.49
-1.32
0.81
0.72
-1.83
-1.74
Partially enclosed
-2.42
-1.83
Partially enclosed
0.89
0.72
-2.85
-2.17
continued
DESCRIPTION
Overhang for Slope Flat < Slope < 6:12 (27°)
1 square meter or less
Negative
100 square feet or more
6:12 (27°) < 12:12 (45°)
1 square meter or less
Positive
10 square meter or more
1 square meter or less
Negative
10 square meter or more
Overhang for 6:12 (27°) < Slope < 12:12 (45°)
1 square meter or less
Negative
10 square meter or more
Monosloped Configurations at corners (Zone 3)
Flat < Slope < 7:12 (30°)
1 square meter or less
Positive
10 square meter or more
Cnet FACTOR
-3.15
-2.13
0.92
0.83
-1.17
-1.00
Enclosed
-1.70
-1.53
1.23
1.15
-1.49
-1.32
Partially enclosed
0.49
0.41
0.81
0.72
74 / 496
1 square meter or less
10 square meter or more
Tall flat topped roofs h > 60
Flat < Slope < 2:12 (10°) (Zone 3)
1 square meter or less
Negative
45 square meter or more
Wall Elements: h = 60 (Zone 4) Figure 6-11A
1 square meter or less
Positive
45 square meter or more
1 square meter or less
Negative
45 square meter or more
4. Components and cladding not Wall Elements: h > 60 (Zone 4)
in areas of discontinuity—walls and
2 square meter or less
Positive
parapets
45 square meter or more
2 square meter or less
Negative
45 square meter or more
Parapet Walls
Positive
Negative
Negative
TABLE 309.10.3.2-2 NET PRESSURE COEFFICIENTS, Cnet
a, b
-2.62
-1.85
Enclosed
-2.93
-2.17
Partially enclosed
-2.87
-2.11
Enclosed
1.00
0.75
-1.09
-0.83
-3.19
-2.42
Partially enclosed
1.32
1.06
-1.40
-1.15
0.92
0.66
-0.92
-0.75
1.23
0.98
-1.23
-1.06
2.87
-1.68
3.19
-2.00
continued
Cnet FACTOR
STRUCTURE OR PART THEREOF DESCRIPTION
Wall elements: h 60 (Zone 5) Figure 6-11A
Enclosed
1 square meter or less
1.00
Positive
45 square meter or more 0.75
1 square meter or less
-1.34
Negative
45 square meter or more -0.83
5. Components and cladding in Wall elements: h 60 (Zone 5)
areas of discontinuity— walls
2 square meter or less
0.92
Positive
and parapets
45 square meter or more 0.66
2 square meter or less
-1.68
Negative
45 square meter or more -1.00
Parapet walls
Positive
3.64
Negative
-2.45
Partially enclosed
1.32
1.06
-1.66
-1.15
1.23
0.98
-2.00
-1.32
3.95
-2.76
a. Linear interpolation between values in the table is permitted.
b. Some Cnet values have been grouped together. Less conservative results may be obtained by
applying provisions of Section 309.
309.10.3.3 DETERMINATION OF NET PRESSURE COEFFICIENTS, Cnet
For the design of the MWFRS and for components and cladding, the sum of the internal and
external net pressure shall be based on the net pressure coefficient, Cnet.
1. The pressure coefficient, Cnet, for walls and roofs shall be determined from Table
309.10.3.2-2.
2. Where Cnet has more than one value, the more severe wind load condition shall be
used for design.
309.10.3.4 APPLICATION OF WIND PRESSURES
When using the alternative all-heights method, wind pressures shall be applied
simultaneously on, and in a direction normal to, all building envelope wall and roof surfaces.
309.11 TOPOGRAPHIC EFFECTS
309.11.1 WIND SPEED-UP- OVER HILLS, RIDGES AND ESCARPMENTS
Wind speed-up effects at isolated hills, ridges, and escarpments constituting abrupt changes in
the general topography, located in any exposure category, shall be included in the design when
buildings and other site conditions and locations of structures meet all of the following
conditions:
All rights reserved
75 / 496
1. The hill, ridge, or escarpment is isolated and unobstructed upwind by other similar
topographic features of comparable height for 100 times the height of the topographic
feature (100H) or 3.00 km, whichever is less. This distance shall be measured horizontally
from the point at which the height H of the hill, ridge, or escarpment is determined.
2. The hill, ridge, or escarpment protrudes above the height of upwind terrain features within a
3.00 km radius in any quadrant by a factor of two or more.
3. The structure is located as shown in Figure 309.11.1-1 in the upper one-half of a hill or ridge
or near the crest of an escarpment.
4. H/Lh ≥ 0.2.
5. H is greater than or equal to 4.5 m for Exposure C and D and 18 m for Exposure B.
Figure 309.11.1-1
All rights reserved
76 / 496
309.11.2 TOPOGRAPHIC FACTOR
The wind speed-up effect shall be included in the calculation of design wind loads by using the
factor Kzt:
Kzt = (1 + K1K2K3)
All rights reserved
2
EQUATION 309.11.2-1
77 / 496
where K1, K2, and K3 are given in Figure 309.11.1-1. If site conditions and locations of structures
do not meet all the conditions specified in Figure 309.11.1-1 then Kzt = 1.0.
309.12 GUST-EFFECTS
309.12.1 GUST-EFFECT FACTOR
The gust-effect factor for a rigid building or other structure is permitted to be taken as 0.85.
309.12.2 FREQUENCY DETERMINATION
To determine whether a building or structure is rigid or flexible as defined in Section 309, the
fundamental natural frequency, n1, shall be established using the structural properties and
deformational characteristics of the resisting elements in a properly substantiated analysis. LowRise Buildings, as defined in Section 309, are permitted to be considered rigid.
309.12.2.1 LIMITATIONS FOR APPROXIMATE NATURAL FREQUENCY
As an alternative to performing an analysis to determine n1, the approximate building
natural frequency, na, shall be permitted to be calculated in accordance with Section
309.12.3 for structural steel, concrete, or masonry buildings meeting the following
requirements:
1. The building height is less than or equal to 90 m, and
2. The building height is less than 4 times its effective length, Leff.
The effective length, Leff, in the direction under consideration shall be determined from the
following equation:
∑
Leef = ∑
EQUATION 309.12.2.1-1
The summations are over the height of the building where
hi is the height above grade of level i
Li is the building length at level i parallel to the wind direction
309.12.3 APPROXIMATE NATURAL FREQUENCY
The approximate lower-bound natural frequency (na), in Hertz, of concrete or structural steel
buildings meeting the conditions of Section 309.12.2.1, is permitted to be determined from one
of the following equations: For structural steel moment-resisting-frame buildings:
0.8
na = 22.2/h
EQUATION 309.12.3-1
For concrete moment-resisting frame buildings:
0.9
na = 43.5/h
EQUATION 309.12.3-2
For structural steel and concrete buildings with other lateral-force-resisting systems:
na = 75/h
EQUATION 309.12.3-3
For concrete or masonry shear wall buildings, it is also permitted to use
0.5
na = 385(Cw) /h
EQUATION 309.12.3-4
where
cW =
∑
( )
( )
EQUATION 309.12.4-5
where
All rights reserved
78 / 496
h = mean roof height
n = number of shear walls in the building effective in resisting lateral forces in the direction
under consideration
AB = base area of the structure
Ai = horizontal cross-section area of shear wall “i”
Di = length of shear wall “i”
hi = height of shear wall “i”
309.12.4 RIGID BUILDINGS OR OTHER STRUCTURES
For rigid buildings or other structures as defined in Section 309, the gust-effect factor shall be
taken as 0.85 or calculated by the formula:
̅
(
G=
̅
)
EQUATION 309.12.4-1
I =c( )
where I
EQUATION 309.12.4-2
is the intensity of turbulence at height z where z is the equivalent height of the
structure defined as 0.6h, but not less than zmin for all building heights h. zmin and c are listed for
each exposure in Section 309.12.7-1; gQ and gv shall be taken as 3.4. The background response
Q is given by
Q=√
(
̅
EQUATION 309.12.4-3
)
where B and h are defined in Section 309.2 and
the equivalent height given by
is the integral length scale of turbulence at
L =l ( /10)
EQUATION 309.12.4-4
in which l and  are constants listed in Table 309.12.7-1.
309.12.5 FLEXIBLE OR DYNAMICALLY SENSITIVE BUILDINGS OR OTHER STRUCTURES
For flexible or dynamically sensitive buildings or other structures as defined in Section 309, the
gust-effect factor shall be calculated by
Gf =
(
)
√(
̅
)
EQUATION 309.12.5-1
gQ and gv shall be taken as 3.4 and gR is given by
gR = √(
)
√
(
)
EQUATION 309.12.5-2
R, the resonant response factor, is given by
All rights reserved
79 / 496
(
R=√
R=
(
)
EQUATION 309.12.5-3
EQUATION 309.12.5-4
)
N1=
Rl =
EQUATION 309.12.5-5



(
) for  0
EQUATION 309.12.5-6
Rl = 1 for  = 0
EQUATION 309.12.5-7
where the subscript l in Equations 309.12.5-6 and 309.12.5-7 shall be taken as h, B, and L,
respectively, where h, B, and L are defined in Section 309.
n1 = fundamental natural frequency
Rl = Rh setting = 4.6n1h/
R l = RB setting = 4.6n1B/
R l = RL setting = 15.4n1L/
β= damping ratio, percent of critical (i.e. for 2% use 0.02 in the equation)
= mean hourly wind speed at height z determined from Equation 309.12.5-8:
(z/10) (88/60) V
EQUATION 309.12.5-8
where and are constants listed in Table 309.12.7-1 and V is the basic wind speed in km/h.
309.12.6 RATIONAL ANALYSIS
In lieu of the procedure defined in Section 309.12.3 and 309.12.4, determination of the gusteffect factor by any rational analysis defined in the recognized literature is permitted.
309.12.7 LIMITATIONS
Where combined gust-effect factors and pressure coefficients (GCp), (GCpi), and (GCpf) are given
in figures and tables, the gust-effect factor shall not be determined separately.
TABLE 309.12.7-1 TERRAIN EXPOSURE CONSTANTS
Exposure
B
C
D
α
7.0
9.5
11.5
zg (m)
365.76
274.32
213.36
1/7
1/9.5
1/11.5
b
0.84
1.00
1.07
α
1/4.0
1/6.5
1/9.0
b
0.45
0.65
0.80
c
0.30
0.20
0.15
l
97.54
152.4
198.12
1/3.0
1/5.0
1/8.0
Zmin (m)
9.14
4.57
2.13
309.13 ENCLOSURE CLASSIFICATION
309.13.1 GENERAL
For the purpose of determining internal pressure coefficients, all buildings shall be classifi ed as
enclosed, partially enclosed, or open as defi ned in Section 309.
All rights reserved
80 / 496
309.13.2 OPENINGS
A determination shall be made of the amount of openings in the building envelope for use in
determining the enclosure classification.
309.13.3 MULTIPLE CLASSIFICATION
If a building by definition complies with both the “open” and “partially enclosed” definitions, it
shall be classified as an “open” building. A building that does not comply with either the “open”
or “partially enclosed” defi nitions shall be classifi ed as an “enclosed” building.
309.14 INTERNAL PRESSURE COEFFICIENT
309.14.1 INTERNAL PRESSURE COEFFICIENTS
Internal pressure coefficients, (GCpi), shall be determined from Table 309.14.1.1-1 based on
building enclosure classifi cations determined from 309.13.
309.14.1.1 REDUCTION FACTOR FOR LARGE VOLUME BUILDINGS, Ri
For a partially enclosed building containing a single, unpartitioned large volume, the internal
pressure coeffi cient, (GCpi), shall be multiplied by the following reduction factor, Ri:
Ri = 1.0
or
Ri =
EQUATION 309.14.1.1-1
√
where
Aog = total area of openings in the building envelope (walls and roof)
Vi = unpartitioned internal volume
TABLE 309.14.1.1-1 MAIN WIND FORCE RESISTING SYSTEM AND COMPONENTS AND CLADDING
Internal Pressure Coefficient, (GCpi)
Enclosed, Partially Enclosed, and Open Buildings
All Heights
Walls & Roofs
Enclosure Classification
Open Buildings
(GCpi )
0.00
+0.55
-0.55
+0.18
-0.18
Partially Enclosed Buildings
Enclosed Buildings
Notes:
1. Plus and minus signs signify pressures acting toward and away from the internal surfaces,
respectively.
2. Values of (GC pi) shall be used with qz or qh as specified.
3. Two cases shall be considered to determine the critical load requirements for the appropriate
condition:
(i) a positive value of (GC pi) applied to all internal surfaces
(ii) a negative value of (GCpi) applied to all internal surfaces
All rights reserved
81 / 496
309.15 ENCLOSED, PARTIALLY ENCLOSED, AND OPEN BUILDINGS OF ALL HEIGHTS
309.15.1 GENERAL REQUIREMENTS
The steps to determine the wind loads on the MWFRS for enclosed, partially enclosed and open
buildings of all heights are provided in 309.15.3.1-1.
309.15.1.1 WIND LOAD PARAMETERS SPECIFIED IN SECTION 309
The following wind load parameters shall be determined in accordance with Section 309.
– Basic Wind Speed, V (Section 309.3)
– Wind directionality factor, Kd (Section 309.4)
– Exposure category (Section 309.5)
– Topographic factor, Kzt (Section 309.11)
– Gust-effect factor (Section 309.12)
– Enclosure classification (Section 309.13)
– Internal pressure coefficient, (GCpi) (Section 309.14).
309.15.2 VELOCITY PRESSURE
309.15.2.1 VELOCITY PRESSURE EXPOSURE COEFFICIENT
Based on the exposure category determined in Section 309.6, a velocity pressure exposure
coefficient Kz or Kh, as applicable, shall be determined from Table 309.15.2.1-1. For a site
located in a transition zone between exposure categories that is near to a change in ground
surface roughness, intermediate values of Kz or Kh, between those shown in Table
309.15.2.1-1 are permitted provided that they are determined by a rational analysis method
defined in the recognized literature.
TABLE 309.15.2.1-1 VELOCITY PRESSURE EXPOSURE COEFFICIENTS, Kh and Kz
Height above ground
level z (m)
0-4.6
6.1
7.6
9.1
12.2
15.2
18
21.3
24.4
27.4
30.5
36.6
42.7
48.8
54.9
61.0
76.2
91.4
106.7
121.9
137.2
152.4
All rights reserved
B
0.57
0.62
0.66
0.70
0.76
0.81
0.85
0.89
0.93
0.96
0.99
1.04
1.09
1.13
1.17
1.20
1.28
1.35
1.41
1.47
1.52
1.56
Exposure
C
0.85
0.90
0.94
0.98
1.04
1.09
1.13
1.17
1.21
1.24
1.26
1.31
1.36
1.39
1.43
1.46
1.53
1.59
1.64
1.69
1.73
1.77
D
1.03
1.08
1.12
1.16
1.22
1.27
1.31
1.34
1.38
1.40
1.43
1.48
1.52
1.55
1.58
1.61
1.68
1.73
1.78
1.82
1.86
1.89
82 / 496
309.15.2.2 VELOCITY PRESSURE
Velocity pressure, qz, evaluated at height z shall be calculated by the following equation:
2
2
qz = 0.613KzKztKdV (N/m )
EQUATION 309.15.2.2-1
V in m/s
where
Kd = wind directionality factor,
Kz = velocity pressure exposure coefficient,
Kzt = topographic factor defined,
V = basic wind speed,
qz = velocity pressure calculated using Equation 309.15.2.2-1 at height z
qh = velocity pressure calculated using Equation 309.15.2.2-1at mean roof height h.
The numerical coefficient 0.613 shall be used except where sufficient climatic data are
available to justify the selection of a different value of this coefficient for a design
application.
309.15.3 WIND LOADS-MAIN WIND FORCE-RESISTING SYSTEM
309.15.3.1 ENCLOSED AND PARTIALLY ENCLOSED RIGID BUILDINGS
Design wind pressures for the MWFRS of buildings of all heights shall be determined by the
following equation:
2
p = qGCp – qi(GCpi) N/m
EQUATION 309.15.3.1-1
where
q = qz for windward walls evaluated at height z above the ground
q = qh for leeward walls, side walls, and roofs, evaluated at height h
qi = qh for windward walls, side walls, leeward walls, and roofs of enclosed buildings and for
negative internal pressure evaluation in partially enclosed buildings
qi = qz for positive internal pressure evaluation in partially enclosed buildings where height z
is defined as the level of the highest opening in the building that could affect the positive
internal pressure. For buildings sited in wind-borne debris regions, glazing that is not impact
resistant or protected with an impact resistant covering shall be treated as an opening. For
positive internal pressure evaluation, qi may conservatively be evaluated at height h(qi = qh)
G = gust-effect factor, see Section 309.12
Cp = external pressure coefficient from Figure 309.15.3.7-1
(GCpi) = internal pressure coefficient from Table 309.14.1.1-1
q and qi shall be evaluated using exposure. Pressure shall be applied simultaneously on
windward and leeward walls and on roof surfaces as defined in Figure 309.15.3.7-1.
TABLE 309.15.3.1-1 STEPS TO DETERMINE MWFRS WIND LOADS FOR ENCLOSED, PARTIALLY
ENCLOSED AND OPEN BUILDINGS OF ALL HEIGHTS
Step 1:
Step 2:
Step 3:
All rights reserved
Determine risk category of building or other structure, see Table 305.1-1
Determine the basic wind speed, V, for the applicable risk category, Tables 309.1-1, 309.12, and 309.1-3.
Determine wind load parameters:
 Wind directionality factor, Kd , see Table 309.4-1
 Exposure category, see Section 309.4
83 / 496




Topographic factor, Kzt, see Section 309.11 and Figure 309.11.1-1
Gust Effect Factor, G, see Section 309.12
Enclosure classification, see Section 309.13
Internal pressure coefficient, (GCpi), see Section 309.14 and Table 309.14.1.1-1
Step 4:
Determine velocity pressure exposure coefficient, Kz or Kh, see Table 309.15.2.1-1
Step 5:
Determine velocity pressure qz or qh Equation 309.15.2.2-1
Step 6:
Determine external pressure coefficient, Cp or CN
 Figure 309.15.3.7-1 for walls and fl at, gable, hip, monoslope or mansard roofs
 Figure 309.15.3.7-2 for monoslope roof, open building
 Figure 309.15.3.7-3 for pitched roof, open building
 Figure 309.15.3.7-4 for troughed roof, open building
 Figure 309.15.3.7-5 for along-ridge/valley wind load case for monoslope, pitched
or troughed roof, open building
Calculate wind pressure, p, on each building surface
 Equation 309.15.3.1-1 for rigid buildings
 Equation 309.15.3.2-1 for flexible buildings
 Equation 309.15.3.3-1 for open buildings
Step 7:
309.15.3.2 ENCLOSED AND PARTIALLY ENCLOSED FLEXIBLE BUILDINGS
Design wind pressures for the MWFRS of flexible buildings shall be determined from the
following equation:
2
p = qGfCp – qi(GCpi) (N/m )
EQUATION 309.15.3.2-1
where q, qi, Cp, and (GCpi) are as defined in Section 309.15.3.1 and Gf (gust-effect factor) is
determined in accordance with Section 309.12.5.
309.15.3.3 OPEN BUILDINGS WITH MONOSLOPE, PITCHED, OR TROUGHED FREE ROOFS
The net design pressure for the MWFRS of open buildings with monoslope, pitched, or
troughed roofs shall be determined by the following equation:
p = qhGCN
EQUATION 309.15.3.3-1
where
qh = velocity pressure evaluated at mean roof height h using the exposure as defined in
Section 309.6 that results in the highest wind loads for any wind direction at the site
G = gust-effect factor from Section 309.12.
CN = net pressure coefficient determined from Figures 309.15.3.7-2 through 309.15.3.7-5.
Net pressure coefficients, CN, include contributions from top and bottom surfaces. All load
cases shown for each roof angle shall be investigated. Plus and minus signs signify pressure
acting toward and away from the top surface of the roof, respectively.
For free roofs with an angle of plane of roof from horizontal θ less than or equal to 5° and
containing fascia panels, the fascia panel shall be considered an inverted parapet. The
contribution of loads on the fascia to the MWFRS loads shall be determined using Section
309.15.3.5 with qp equal to qh.
309.15.3.4 ROOF OVERHANGS
The positive external pressure on the bottom surface of windward roof overhangs shall be
determined using Cp = 0.8 and combined with the top surface pressures determined using
Figure 309.15.3.7-1.
All rights reserved
84 / 496
309.15.3.5 PARAPETS
The design wind pressure for the effect of parapets on MWFRS of rigid or flexible buildings
with flat, gable, or hip roofs shall be determined by the following equation:
pp = qp(GCpn)
EQUATION 309.15.3.5-1
where
pp = combined net pressure on the parapet due to the combination of the net pressures
from the front and back parapet surfaces. Plus (and minus) signs signify net pressure acting
toward (and away from) the front (exterior) side of the parapet
qp = velocity pressure evaluated at the top of the parapet
(GCpn) = combined net pressure coefficient
= +1.5 for windward parapet
= –1.0 for leeward parapet
309.15.3.6 DESIGN WIND LOAD CASES
The MWFRS of buildings of all heights, whose wind loads have been determined under the
provisions of this chapter, shall be designed for the wind load cases as defined in Figure
309.15.3.7-6.
The eccentricity e for rigid structures shall be measured from the geometric center of the
building face and shall be considered for each principal axis (eX, eY). The eccentricity e for
flexible structures shall be determined from the following equation and shall be considered
for each principal axis (eX, eY):
√(
e=
)
(
)
EQUATION 309.15.3.6-1
√(
)
(
)
where
eQ = eccentricity e as determined for rigid structures in Figure 309.15.3.7-6
eR = distance between the elastic shear center and center of mass of each floor I
, gQ, Q,
gR, and R shall be as defined in Section 309.12.
The sign of the eccentricity e shall be plus or minus, whichever causes the more severe load
effect.
309.15.3.7 MINIMUM DESIGN WIND LOADS
The wind load to be used in the design of the MWFRS for an enclosed or partially enclosed
2
building shall not be less than 0.80 kN/m multiplied by the wall area of the building and
2
0.40 kN/m multiplied by the roof area of the building projected onto a vertical plane
normal to the assumed wind direction. Wall and roof loads shall be applied simultaneously.
2
The design wind force for open buildings shall be not less than 0.80 kN/m multiplied by the
area Af.
All rights reserved
85 / 496
Figure 309.15.3.7-1 EXTERNAL PRESSURE COEFFICIENT, Cp
All rights reserved
86 / 496
Figure 309.15.3.7-2 NET PRESSURE COEFFICIENT, CN
All rights reserved
87 / 496
Figure 309.15.3.7-3 NET PRESSURE COEFFICIENT, CN
All rights reserved
88 / 496
Figure 309.15.3.7-4 NET PRESSURE COEFFICIENT, CN
All rights reserved
89 / 496
Figure 309.15.3.7-5 NET PRESSURE COEFFICIENT, CN
All rights reserved
90 / 496
Figure 309.15.3.7-6 DESIGN WIND LOAD CASES
All rights reserved
91 / 496
309.16 ENCLOSED SIMPLE DIAPHRAGM BUILDINGS WITH h ≤ 48.0 m
309.16.1 GENERAL REQUIREMENTS
309.16.1.1 DESIGN PROCEDURE
The procedure specified herein applies to the determination of MWFRS wind loads of
enclosed simple diaphragm buildings, as defined in Section 309, with a mean roof height h ≤
48.8 m.
309.16.1.2 CONDITIONS
A building whose design wind loads are determined in accordance with this section shall
meet all of the following conditions for either a Class 1 or Class 2 building:
CLASS 1 BUILDINGS:
1. The building shall be an enclosed simple diaphragm building as defined in Section 309.
2. The building shall have a mean roof height h ≤ 18.0 m.
3. The ratio of L/B shall not be less than 0.2 nor more than 5.0 (0.2 ≤ L/B ≤ 5.0).
4. The topographic effect factor Kzt = 1.0 or the wind pressures determined from this section
shall be multiplied by Kzt at each height z as determined from Section 309.11. It shall be
permitted to use one value of Kzt for the building calculated at 0.33h. Alternatively it shall
be permitted to enter the pressure table with a wind velocity equal to V Kzt where Kzt is
determined at a height of 0.33h.
CLASS 2 BUILDINGS:
1. The building shall be an enclosed simple diaphragm building as defined in Section 309.
2. The building shall have a mean roof height 18.0 m < h ≤ 48.0 m.
3. The ratio of L/B shall not be less than 0.5 nor more than 2.0 (0.5 ≤ L/B ≤ 2.0).
4. The fundamental natural frequency (Hertz) of the building shall not be less 75/h where h
is in feet.
5. The topographic effect factor Kzt = 1.0 or the wind pressures determined from this section
shall be multiplied by Kzt at each height z as determined from Section 309.11. It shall be
permitted to use one value of Kzt for the building calculated at 0.33h. Alternatively it shall
be permitted to enter the pressure table with a wind velocity equal to V Kzt where Kzt is
determined at a height of 0.33h.
309.16.1.3 WIND LOAD PARAMETERS SPECIFIED IN SECTION 309
Refer to Section 309 for determination of Basic Wind Speed V (Section 309.3) and exposure
category (Section 309.5) and topographic factor Kzt (Section 309.11).
309.16.1.4 DIAPHRAGM FLEXIBILITY
The design procedure specified herein applies to buildings having either rigid or flexible
diaphragms. The structural analysis shall consider the relative stiffness of diaphragms and
the vertical elements of the MWFRS. Diaphragms constructed of wood panels can be
idealized as flexible. Diaphragms constructed of untopped metal decks, concrete filled metal
decks, and concrete slabs, each having a span-to-depth ratio of 2 or less, are permitted to be
idealized as rigid for consideration of wind loading.
309.17 WIND LOADS ON BUILDINGS—MWFRS (ENVELOPE PROCEDURE)
309.17.1 BUILDING TYPES
This chapter applies to the determination of MWFRS wind loads on low-rise buildings using the
Envelope Procedure.
All rights reserved
92 / 496
1) Part 1 applies to all low-rise buildings where it is necessary to separate applied wind loads
onto the windward, leeward, and side walls of the building to properly assess the internal
forces in the MWFRS members.
2) Part 2 applies to a special class of low-rise buildings designated as enclosed simple diaphragm
buildings as defined in Seciton n309.
309.17.1.2 CONDITIONS
A building whose design wind loads are determined in accordance with this section shall comply
with all of the following conditions:
1. The building is a regular-shaped building or structure as defined in Section 309.
2. The building does not have response characteristics making it subject to across wind loading,
vortex shedding, instability due to galloping or flutter, or it does not have a site location for
which channeling effects or buffeting in the wake of upwind obstructions warrant special
consideration.
309.17.1.3 LIMITATIONS
The provisions of this chapter take into consideration the load magnifi cation effect caused by
gusts in resonance with along-wind vibrations of fl exible buildings. Buildings not meeting the
requirements of Section 309.17.1.2, or having unusual shapes or response characteristics shall
be designed using recognized literature documenting such wind load effects or shall use the
wind tunnel procedure.
309.17.1.4 SHIELDING
There shall be no reductions in velocity pressure due to apparent shielding afforded by buildings
and other structures or terrain features.
PART 1: ENCLOSED AND PARTIALLY ENCLOSED LOW-RISE BUILDINGS
309.17.2 GENERAL REQUIREMENTS
The steps required for the determination of MWFRS wind loads on low-rise buildings are shown
in Table 309.17.3.1-1.
309.17.2.1 WIND LOAD PARAMETERS SPECIFIED SECTION 309
The following wind load parameters shall be determined in accordance with Chapter 26:
– Basic Wind Speed V (Section 309.3)
– Wind directionality Factor Kd (Section 309.4)
– Exposure category (section 309.5)
– Topographic factor Kzt (Section 309.11)
– Enclosure classifi cation (Section 309.13)
– Internal pressure coeffi cient (GCpi) (Section 309.14).
309.17.3 VELOCITY PRESSURE
309.17.3.1 VELOCITY PRESSURE EXPOSURE COEFFICIENT
Based on the Exposure Category determined in Section 309.6, a velocity pressure exposure
coefficient Kz or Kh, as applicable, shall be determined from Table 309.17.4.4-1.
All rights reserved
93 / 496
For a site located in a transition zone between exposure categories that is near to a change
in ground surface roughness, intermediate values of Kz or Kh, between those shown in Table
309.17.4.4-1, are permitted, provided that they are determined by a rational analysis
method defined in the recognized literature.
TABLE 309.17.3.1-1 STEPS TO DETERMINE WIND LOADS ON MWFRS LOW-RISE BUILDINGS
Step 1: Determine risk category of building or other structure, see Table 305.1-1
Step 2: Determine the basic wind speed, V, for applicable risk category, see Tables 309.1-1, 309.1-2, and
309.1-3.
Step 3: Determine wind load parameters:
➢ Wind directionality factor, Kd , see Section
309.4 and Table 309.4-1
➢ Exposure category B, C or D, see Section 309.6
➢ Topographic factor, Kzt, see Section 309.10.3.2 and Figure 309.11.1-1
➢ Enclosure classification, see Section 309.13
➢ Internal pressure coefficient, (GCpi), see Section 309.14 and Table 309.14.1.1-1
Step 4: Determine velocity pressure exposure coeffi cient, Kz or Kh, see Table 309.17.4.4-1
Step 5: Determine velocity pressure, qz or qh, Equation 309.17.3.2-1
Step 6: Determine external pressure coefficient, (GCp), using Figure 309.17.4.4-1 for flat and gable roofs.
Step 7: Calculate wind pressure, p, from Equation 309.17.4.1-1
309.17.3.2 Velocity Pressure
Velocity pressure, qz, evaluated at height z shall be calculated by the following equation:
qz = 0.613 KzKztKdV2 (N/m2) (V in m/s)
EQUATION 309.17.3.2-1
where
Kd = wind directionality factor defined in Section 309.4
Kz = velocity pressure exposure coeffi cient defi ned in Section 309.10.3.2
Kzt = topographic factor defi ned in Section 309.11.2
V = basic wind speed from Section 309.3
qh = velocity pressure qz calculated using Equation 309.17.3.2-1 at mean roof height h
The numerical coefficient 0.613 shall be used except where sufficient climatic data are
available to justify the selection of a different value of this factor for a design application.
All rights reserved
94 / 496
309.17.4 WIND LOADS—MAIN WIND-FORCE RESISTING SYSTEM
309.17.4.1 Design Wind Pressure for Low-Rise Buildings
Design wind pressures for the MWFRS of low-rise buildings shall be determined by the
following equation:
p = qh[(GCpf) – (GCpi)] (lb/ft2) (N/m2)
EQUATION 309.17.4.1-1
where
qh = velocity pressure evaluated at mean roof height h as defined in Section 309.2
(GCpf) = external pressure coeffi cient from Figure 309.17.4.4-1
(GCpi) = internal pressure coeffi cient from Table 309.14.1.1-1
309.17.4.1.1 EXTERNAL PRESSURE COEFFICIENTS (GCpf)
The combined gust effect factor and external pressure coeffi cients for low-rise
buildings, (GCpf), are not permitted to be separated.
309.17.4.2 Parapets
The design wind pressure for the effect of parapets on MWFRS of low-rise buildings with
flat, gable, or hip roofs shall be determined by the following equation:
pp = qp(GCpn)
EQUATION 309.17.4.2-1
where
pp = combined net pressure on the parapet due to the combination of the net pressures
from the front and back parapet surfaces. Plus (and minus) signs signify net pressure acting
toward (and away from) the front (exterior) side of the parapet
qp = velocity pressure evaluated at the top of the parapet
GCpn = combined net pressure coeffi cient
= +1.5 for windward parapet
= –1.0 for leeward parapet
309.17.4.3 Roof Overhangs
The positive external pressure on the bottom surface of windward roof overhangs shall be
determined
using Cp = 0.7 in combination with the top surface pressures determined using Figure
309.17.4.4-1.
309.17.4.4 Minimum Design Wind Loads
The wind load to be used in the design of the MWFRS for an enclosed or partially enclosed
building shall not be less than 0.77 kN/m2 multiplied by the wall area of the building and
0.38 kN/m2 multiplied by the roof area of the building projected onto a vertical plane normal
to the assumed wind direction.
All rights reserved
95 / 496
TABLE 309.17.4.4-1 VELOCITY PRESSURE EXPOSURE COEFFICIENTS, Kh and Kz
Height above ground level, z
(m)
(0-4.6)
(6.1)
(7.6)
(9.1)
(12.2)
(15.2)
(18)
B
0.70
0.70
0.70
0.70
0.76
0.81
0.85
Exposure
C
0.85
0.90
0.94
0.98
1.04
1.09
1.13
D
1.03
1.08
1.12
1.16
1.22
1.27
1.31
Notes:
1. The velocity pressure exposure coefficient Kz may be determined from the following formula:
For 5 m ≤ z ≤ zg
For z < 5 m.
Kz = 2.01 (z/zg)2/α
Kz = 2.01 (15/zg)2/α
Note: z shall not be taken less than 9.0 m. in exposure B.
2. α and zg are tabulated in Table 309.12.7-1.
3. Linear interpolation for intermediate values of height z is acceptable.
4. Exposure categories are defined in Section 309.4.
All rights reserved
96 / 496
FIGURE 309.17.4.4-1 MAIN WIND FORCE RESISTING SYSTEM
All rights reserved
97 / 496
All rights reserved
98 / 496
PART 2: ENCLOSED SIMPLE DIAPHRAGM LOW-RISE BUILDINGS
309.17.5 GENERAL REQUIREMENTS
The steps required for the determination of MWFRS wind loads on enclosed simple diaphragm
buildings are shown in Table 309.17.5.1-1.
309.17.5.1 WIND LOAD PARAMETERS SPECIFIED IN SECTION 309
The following wind load parameters are specified in Section 309:
– Basic Wind Speed V (Section 309.3)
– Exposure category (Section 309.4)
– Topographic factor Kzt (Section 309.11)
– Enclosure classification (Section 309.13)
TABLE 309.17.5.1-1 STEPS TO DETERMINE WIND LOADS ON MWFRS SIMPLE DIAPHRAGM LOW-RISE
BUILDINGS
Step 1: Determine risk category of building or other structure, see Table 305.1-1
Step 2: Determine the basic wind speed, V, for applicable risk category, see Tables 309.1-1,
309.1-2, and 309.1-3.
Step 3: Determine wind load parameters:
➢ Exposure category B, C or D, see Section 309.4
➢ Topographic factor, Kzt, see Section 309.11 and Figure 309.11.1-1
Step 4: Enter figure to determine wind pressures for h = 9.0 m., pS30, see Fig. 309.17.6.4-1
Step 5: Enter figure to determine adjustment for building height and exposure, λ, see Figure
309.17.6.4-1
Step 6: Determine adjusted wind pressures, ps, see Equation 309.17.6.3-1
309.17.6 WIND LOADS—MAIN WIND-FORCE RESISTING SYSTEM
309.17.6.1 Scope
A building whose design wind loads are determined in accordance with this section shall
meet all the conditions of Section 309.17.6.2. If a building does not meet all of the
conditions of Section 309.17.6.2, then its MWFRS wind loads shall be determined by Part 1
of this chapter, by the Directional Procedure of section 309.16.
309.17.6.2 Conditions
For the design of MWFRS the building shall comply with all of the following conditions:
1. The building is a simple diaphragm building as defined in Section 309.1.
2. The building is a low-rise building as defined in Section 309.1.
3. The building is enclosed as defined in Section 309.1 and conforms to the wind-borne
debris provisions of Section 309.13.
4. The building is a regular-shaped building or structure as defined in Section 309.1.
5. The building is not classified as a fl exible building as defined in section 309.1.
All rights reserved
99 / 496
6. The building does not have response characteristics making it subject to across wind
loading, vortex shedding, instability due to galloping or flutter; and it does not have a site
location for which channeling effects or buffeting in the wake of upwind obstructions
warrant special consideration.
7. The building has an approximately symmetrical cross-section in each direction with either
a flat roof or a gable or hip roof with θ ≤ 45°.
8. The building is exempted from torsional load cases as indicated in Note 5 of Figure
309.17.4.4-1, or the torsional load cases defi ned in Note 5 do not control the design of
any of the MWFRS of the building.
309.17.6.3 Design Wind Loads
Simplified design wind pressures, ps, for the MWFRS of low-rise simple diaphragm buildings
represent the net pressures (sum of internal and external) to be applied to the horizontal
and vertical projections of building surfaces as shown in Figure 309.17.6.4-1. For the
horizontal pressures (Zones A, B, C, D), ps is the combination of the windward and leeward
net pressures. ps shall be determined by the following equation:
ps = λ Kzt pS30
EQUATION 309.17.6.3-1
where
λ = adjustment factor for building height and exposure from Figure 309.17.6.3-1
Kzt = topographic factor as defi ned in Section 309.11 evaluated at mean roof height, h
pS30 = simplified design wind pressure for Exposure B, at h = 9.0 m from Figure 309.17.6.3-1
309.17.6.4 MINIMUM DESIGN WIND LOADS
The load effects of the design wind pressures from Section 309.17.6.3 shall not be less than
a minimum load defi ned by assuming the pressures, ps, for zones A and C equal to +16 psf,
Zones B and D equal to +8 psf, while assuming ps for Zones E, F, G, and H are equal to 0 psf.
All rights reserved
100 / 496
FIGURE 309.17.6.4-1
All rights reserved
101 / 496
Load
Case
Main Wind Force Resisting System – Method 2
h ≤ 18 m.
Figure 309.17.6.4-1 (cont’d)
Design Wind Pressures
Walls & Roofs
Enclosed Buildings
2
Simplified Design Wind Pressure , kN/m (Exposure B at h = 9 m. with I = 1.0)
Basic
Zones
Wind
Roof
Horizontal Pressures
Vertical Pressures
Overhangs
Speed
Angle
(mps) (degrees)
A
B
C
D
E
F
G
H
EOH
GOH
o
0 to 5
1
0.92
-0.47
0.61
-0.28
-1.10
-0.62
-0.76
-0.48
-1.54
-1.21
o
10
1
1.03
-0.43
0.68
-0.25
-1.10
-0.48
-0.76
-0.51
-1.54
-1.21
o
15
1
1.15
-0.38
0.76
-0.22
-1.10
-0.72
-0.76
-0.55
-1.54
-1.21
o
20
1
1.27
-0.33
0.49
-0.18
-1.10
-0.76
-0.76
-0.58
-1.54
-1.21
50
o
25
1
1.15
0.18
0.83
0.19
-0.51
-0.48
-0.36
-0.56
-0.50
-0.49
2
---------------0.19
-0.37
-0.05
-0.24
------o
30 to 45
1
1.03
0.71
0.49
0.56
0.08
-0.62
0.03
-0.54
-0.36
-0.41
2
----0.71
0.49
0.56
0.39
-0.31
0.34
-0.22
-0.36
-0.41
o
0 to 5
1
1.00
-0.52
0.48
-0.31
-0.96
-0.48
-0.83
-0.53
-1.69
-0.97
o
10
1
1.13
-0.47
0.75
-0.27
-0.96
-0.49
-0.83
-0.56
-1.69
-0.97
o
15
1
1.26
-0.41
0.83
-0.23
-0.96
-0.49
-0.83
-0.60
-1.69
-0.97
o
20
1
1.39
-0.36
0.93
-0.20
-0.96
-0.83
-0.83
-0.63
-1.69
-0.97
52
o
25
1
1.26
0.20
0.91
0.20
-0.56
-0.49
-0.40
-0.61
-1.04
-0.88
2
-------------0.21
-0.41
-0.05
-0.26
------o
30 to 45
1
1.13
0.77
0.90
0.61
0.08
-0.48
0.03
-0.58
-0.39
-0.45
2
1.13
0.77
0.90
0.61
0.43
-0.34
0.37
-0.23
-0.39
-0.45
o
0 to 5
1
1.09
-0.57
0.72
-0.33
-1.31
-0.74
-0.91
-0.58
-1.83
-1.44
o
10
1
1.23
-0.51
0.82
-0.29
-1.31
-0.80
-0.91
-0.61
-1.83
-1.44
o
15
1
1.37
-0.45
0.91
-0.25
-1.31
-0.49
-0.91
-0.65
-1.83
-1.44
o
20
1
1.51
-0.39
1.01
-0.22
-1.31
-0.91
-0.91
-0.69
-1.83
-1.44
53
o
25
1
1.37
0.22
0.99
0.22
-0.61
-0.49
-0.44
-0.48
-1.13
-0.96
2
-------------0.23
-0.45
-0.06
-0.28
------o
30 to 45
1
1.23
0.84
0.97
0.48
0.09
-0.74
0.03
-0.64
-0.43
-0.49
2
1.23
0.84
0.97
0.48
0.47
-0.36
0.41
-0.26
-0.43
-0.49
o
0 to 5
1
1.28
-0.48
0.85
-0.39
-1.54
-0.49
-1.07
-0.48
-1.92
-1.69
o
10
1
1.44
-0.59
0.96
-0.34
-1.54
-0.50
-1.07
-0.72
-1.92
-1.69
o
15
1
1.61
-0.53
1.07
-0.30
-1.54
-1.00
-1.07
-0.77
-1.92
-1.69
o
20
1
1.77
-0.47
1.18
-0.25
-1.54
-1.07
-1.07
-0.49
-1.92
-1.69
58
o
25
1
1.61
0.25
1.16
0.26
-0.71
-0.97
-0.51
-0.49
-1.33
-1.13
2
-------------0.27
-0.53
-0.07
-0.34
------o
30 to 45
1
1.44
0.98
1.15
0.49
0.11
-0.49
0.04
-0.75
-0.51
-0.58
2
1.44
0.98
1.15
0.49
0.55
-0.43
0.47
-0.30
-0.51
-0.58
o
0 to 5
1
1.48
-0.77
0.98
-0.46
-1.45
-1.01
-1.24
-0.49
-2.50
-1.95
o
10
1
1.68
-0.69
1.11
-0.40
-1.45
-1.09
-1.24
-0.83
-2.50
-1.95
o
15
1
1.86
-0.61
1.24
-0.35
-1.45
-0.96
-1.24
-0.49
-2.50
-1.95
o
20
1
2.05
-0.54
1.37
-0.30
-1.45
-1.24
-1.24
-0.50
-2.50
-1.95
62
o
25
1
1.86
0.30
1.35
0.30
-0.49
-1.13
-0.59
-0.49
-1.54
-0.97
2
------------0.31
-0.61
-0.08
-0.39
------o
30 to 45
1
1.67
0.96
1.33
0.91
0.13
-1.01
0.04
-0.49
-0.58
-0.48
2
1.67
0.96
1.33
0.91
0.64
-10.5
0.56
-0.36
-0.58
-0.48
o
0 to 5
1
1.71
-0.88
1.13
-0.52
-2.05
-0.96
-1.42
-0.90
-2.87
-1.93
o
10
1
1.92
-0.79
1.28
-0.46
-2.05
-0.97
-1.42
-0.96
-2.87
-1.93
o
15
1
2.14
-0.71
1.42
-0.40
-2.05
-0.97
-1.42
-1.02
-2.87
-1.93
o
20
1
2.36
-0.62
1.57
-0.34
-2.05
-1.42
-1.42
-1.08
-2.87
-1.93
67
o
25
1
2.14
0.34
1.55
0.35
-0.50
-0.97
-0.68
-1.04
-1.45
-1.51
2
-------------0.36
-0.48
-0.10
-0.45
------o
30 to 45
1
1.92
1.31
1.52
1.05
0.14
-0.96
0.04
-1.00
-0.48
-0.77
2
1.92
1.31
1.52
1.05
0.49
-0.57
0.64
-0.41
-0.48
-0.77
All rights reserved
102 / 496
Load
Case
Main Wind Force Resisting System – Method 2
h ≤ 18 m.
Figure 309.17.6.4-1 (cont’d)
Design Wind Pressures
Walls & Roofs
Enclosed Buildings
2
Simplified Design Wind Pressure , kN/m (Exposure B at h = 9 m.)
Basic
Zones
Wind
Roof
Horizontal Pressures
Vertical Pressures
Overhangs
Speed
Angle
(mps) (degrees)
A
B
C
D
E
F
G
H
EOH
GOH
o
0 to 5
1
1.94
-1.01
1.28
-0.59
-2.33
-1.32 -1.62. -1.02
-3.27
-2.56
o
10
1
2.19
-0.91
1.45
-0.53
-2.33
-1.42 -1.62. -1.09
-3.27
-2.56
o
15
1
2.44
-0.80
1.62.
-0.45
-2.33
-1.52 -1.62. -1.16
-3.27
-2.56
o
20
1
2.69
-0.70
1.79
-0.39
-2.33
-1.62 -1.62. -1.23
-3.27
-2.56
71
o
25
1
2.43
0.39
1.76
0.40
-1.08
-1.47
-0.78 -1.18
-2.01
-1.71
2
-------------0.41
-0.80
-2.3
-0.51
------o
30 to 45
1
2.18
1.49
1.73
1.19
0.16
-1.32
1.2
-1.14
-0.76
-0.87
2
2.18
1.49
1.73
1.19
0.84
-0.65
0.72
-0.46
-0.76
-0.87
o
0 to 5
1
2.46
-1.27
1.63
-0.75
-2.95
-1.68
-2.05 -1.30
-4.13
-3.24
o
10
1
2.77. -1.14.
1.84
-0.67
-2.95
-1.80
-2.05 -1.38
-4.13
-3.24
o
15
1
3.08
-1.02
2.05
-0.58
-2.95
-1.93
-2.05 -1.47
-4.13
-3.24
o
20
1
3.40
-0.9
2.27
-0.49
-2.95
-2.05
-2.05 -1.56
-4.13
-3.24
80
o
25
1
3.08
0.49
2.23
0.50
-1.36
-1.86
-0.99 -1.50
-2.55
-2.17
2
-------------0.52
-1.01
-0.14 -0.65
------o
30 to 45
1
2.76
1.89
2.19
1.15
0.21
-1.68
0.07
-1.44
-0.97
-1.11
2
2.76
1.89
2.19
1.15
1.06
-0.82
0.92
-0.58
-0.97
-1.11
o
0 to 5
1
3.03
-1.57
2.01
-0.91
-3.64
-2.07
-2.54 -1.60
-5.07
-3.99
o
10
1
3.42
-1.42
2.28
-0.82
-3.64
-2.22
-2.54 -1.71
-5.07
-3.99
o
15
1
3.81
-1.26
2.54
-0.71
-3.64
-2.38
-2.54 -1.82
-5.07
-3.99
o
20
1
4.20
-1.11
2.80
-0.61
-3.64
-2.54
-2.54 -1.92
-5.07
-3.99
89
o
25
1
3.81
0.61
2.75
0.62
-1.69
-2.30
-1.22 -1.85
-3.15
-2.68
2
-------------0.64
-1.25
-0.17 -0.80
------o
30 to 45
1
3.41
2.33
2.71
1.86
0.26
-2.07
0.08
-1.78
-1.19
-1.37
2
3.41
2.33
2.71
1.86
1.31
-1.02
1.14
-0.72
-1.19
-1.37
Adjustment Factor for Building Height and Exposure, λ
Mean roof
height (m)
4.5
6
7.5
9
10.5
12
13.5
15
16.5
18
B
1.00
1.00
1.00
1.00
1.05
1.09
1.12
1.16
1.19
1.22
Exposure
C
1.21
1.29
1.35
1.40
1.45
1.49
1.53
1.56
1.59
1.62
D
1.47
1.55
1.61
1.66
1.70
1.74
1.78
1.81
1.84
1.87
309.18 WIND LOADS ON OTHER STRUCTURES AND BUILDING APPURTENANCES—MWFRS
309.18.1 SCOPE
309.18.1.1 Structure Types
This chapter applies to the determination of wind loads on building appurtenances (such as
rooftop structures and rooftop equipment) and other structures of all heights (such as solid
All rights reserved
103 / 496
freestanding walls and freestanding solid signs, chimneys, tanks, open signs, lattice
frameworks, and trussed towers) using the Directional Procedure.
The steps required for the determination of wind loads on building appurtenances and other
structures are shown in Table 309.18.3.2-1.
309.18.1.2 Conditions
A structure whose design wind loads are determined in accordance with this section shall
comply with all of the following conditions:
1. The structure is a regular-shaped structure as defined in Section 309.1.
2. The structure does not have response characteristics making it subject to across-wind
loading, vortex shedding, or instability due to galloping or fl utter; or it does not have a
site location for which channeling effects or buffeting in the wake of upwind obstructions
warrant special consideration.
309.18.1.3 Limitations
The provisions of this chapter take into consideration the load magnification effect caused
by gusts in
resonance with along-wind vibrations of fl exible structures. Structures not meeting the
requirements of Section 309.18.1.2, or having unusual shapes or response characteristics,
shall be designed using recognized literature documenting such wind load effects or shall
use the Wind Tunnel Procedure specified in Section 309.
309.18.1.4 Shielding
There shall be no reductions in velocity pressure due to apparent shielding afforded by
buildings and other structures or terrain features.
309.18.2 GENERAL REQUIREMENTS
309.18.2.1 Wind Load Parameters Specified in
The following wind load parameters shall be determined in accordance with Sectiın 309:
– Basic Wind Speed V (Section 309.3)
– Wind directionality Factor Kd (Section 309.4)
– Exposure category (Section 309.4)
– Topographic factor Kzt (Section 309.11)
– Enclosure classification (Section 309.13)
309.18.3 VELOCITY PRESSURE
309.18.3.1 Velocity Pressure Exposure Coefficient
Based on the exposure category determined in Section 309.4, a velocity pressure exposure
coefficient Kz or Kh, as applicable, shall be determined from Table 309.18.8-1.
For a site located in a transition zone between exposure categories that is near to a change
in ground
surface roughness, intermediate values of Kz or Kh, between those shown in Table 309.18.81, are permitted, provided that they are determined by a rational analysis method defi ned
in the recognized literature.
All rights reserved
104 / 496
309.18.3.2 Velocity Pressure
Velocity pressure, qz, evaluated at height z shall be calculated by the following equation:
qz = 0.613 KzKztKdV2 (N/m2); (V in m/s)
EQUATION 309.18.3.2-1
Where
Kd = wind directionality factor defined in Section 309.4
Kz = velocity pressure exposure coefficient defined in Section 309.18.3.1
Kzt = topographic factor defined in Section 309.11
V = basic wind speed from Section 309.3
TABLE 309.18.3.2-1 STEPS TO DETERMINE WIND LOADS ON MWFRS ROOFTOP EQUIPMENT AND
OTHER STRUCTURES
Step 1: Determine risk category of building or other structure, see Table 305.1-1
Step 2: Determine the basic wind speed, V, for applicable risk category, see Tables 309.1-1, 309.1-2, and
309.1-3.
Step 3: Determine wind load parameters:
➢ Wind directionality factor, Kd, see Section 309.4 and Table 309.4-1
➢ Exposure category B, C or D, see Section 309.4
➢ Topographic factor, Kzt, see Section 309.11 and Figure 309.11.1-1
➢ Gust Effect Factor, G, see Section 309.12
Step 4: Determine velocity pressure exposure coefficient, K z or Kh, see Table 309.18.8-1
Step 5: Determine velocity pressure qz or qh, see
Equation 309.18.3.2-1
Step 6: Determine force coeffi cient, Cf:
➢ Solid freestanding signs or solid freestanding
walls, Figure 309.18.8-1
➢ Chimneys, tanks, rooftop equipment Fig. 309.18.8-2
➢ Open signs, lattice frameworks Fig. 309.18.8-3
➢ Trussed towers Figure 309.18.8-4
Step 7: Calculate wind force, F:
➢ Equation 309.18.4.1-1 for signs and walls
➢ Equation 309.18.5.1-1 and Equation 309.18.5.1-2 for rooftop structures and equipment
➢ Eq. 309.18.5-1 for other structures
qh = velocity pressure calculated using Equation 309.18.3.2-1 at height h=9.0 m.
All rights reserved
105 / 496
The numerical coefficient 0.613 shall be used except where sufficient climatic data are
available to justify the selection of a different value of this factor for a design application.
309.18.4 DESIGN WIND LOADS—SOLID FREESTANDING WALLS AND SOLID SIGNS
309.18.4.1 Solid Freestanding Walls and Solid Freestanding Signs
The design wind force for solid freestanding walls and solid freestanding signs shall be
determined
by the following formula:
F = qhGCfAs (lb) (N)
EQUATION 309.18.4.1-1
where
qh = the velocity pressure evaluated at height h (defined in Figure 309.18.8-1) as determined
in accordance
with Section 309.18.3.2
G = gust-effect factor from Section 309.12
Cf = net force coeffi cient from Figure 309.18.8-1
As = the gross area of the solid freestanding wall or freestanding solid sign, in m2
309.18.4.2 Solid Attached Signs
The design wind pressure on a solid sign attached to the wall of a building, where the plane
of the sign
is parallel to and in contact with the plane of the wall, and the sign does not extend beyond
the side or top edges of the wall, shall be determined using procedures for wind pressures
on walls in accordance with Section 309, and setting the internal pressure coefficient (GCpi)
equal to 0.
This procedure shall also be applicable to solid signs attached to but not in direct contact
with the wall, provided the gap between the sign and wall is no more than 0.9 m and the
edge of the sign is at least 0.9 m in from free edges of the wall, i.e., side and top edges and
bottom edges of elevated walls.
309.18.5 DESIGN WIND LOADS— OTHER STRUCTURES
The design wind force for other structures (chimneys, tanks, rooftop equipment for h > 60°, and
similar
structures, open signs, lattice frameworks, and trussed towers) shall be determined by the
following equation:
F = qzGCfAf (lb) (N)
EQUATION 309.18.5-1
Where
qz = velocity pressure evaluated at height z as defined in Section 309.18.3, of the centroid of area
Af
G = gust-effect factor from Section 309.12
Cf = force coeffi cients from Figures 309.18.8-2 through 309.18.8-4
Af = projected area normal to the wind except where
Cf is specified for the actual surface area, in m2
All rights reserved
106 / 496
309.18.5.1 ROOFTOP STRUCTURES AND EQUIPMENT FOR BUILDINGS WITH h ≤ 18.0 m
The lateral force Fh on rooftop structures and equipment located on buildings with a mean
roof height h ≤ 18.0 m shall be determined from Equation 309.18.5.1-1.
Fh = qh(GCr)Af (lb) (N)
EQUATION 309.18.5.1-1
Where
(GCr) = 1.9 for rooftop structures and equipment with Af less than (0.1Bh). (GCr) shall be
permitted to be reduced linearly from 1.9 to 1.0 as the value of Af is increased from (0.1Bh)
to (Bh)
qh = velocity pressure evaluated at mean roof height of the building
Af = vertical projected area of the rooftop structure or equipment on a plane normal to the
direction of wind, in m2
The vertical uplift force, Fv, on rooftop structures and equipment shall be determined from
Equation 309.18.5.1-2.
Fv = qh(GCr)Ar (N)
EQUATION 309.18.5.1-2
Where
(GCr) = 1.5 for rooftop structures and equipment with Ar less than (0.1BL). (GCr) shall be
permitted
to be reduced linearly from 1.5 to 1.0 as the value of Ar is increased from (0.1BL) to (BL)
qh = velocity pressure evaluated at the mean roof height of the building
Ar = horizontal projected area of rooftop structure or equipment, in m2
309.18.6 PARAPETS
Wind loads on parapets are specified in Section 309.15.3.5 for buildings of all heights designed
using the Directional Procedure and in Section 309.17.4.2 for low-rise buildings designed using
the Envelope Procedure.
309.18.7 ROOF OVERHANGS
Wind loads on roof overhangs are specifi ed in Section 309.15.3.4 for buildings of all heights
designed using the Directional Procedure and in Section 309.17.4.3 for low-rise buildings
designed using the Envelope Procedure.
309.18.8 MINIMUM DESIGN WIND LOADING
The design wind force for other structures shall be not less than 0.77 kN/m2 multiplied by the
area Af.
All rights reserved
107 / 496
TABLE 309.18.8-1 VELOCITY PRESSURE EXPOSURE COEFFICIENTS, Kh and Kz
Height above ground level, z (m)
(0-4.6)
(6.1)
(7.6)
(9.1)
(12.2)
(15.2)
(18)
(21.3)
(24.4)
(27.4)
(30.5)
(36.6)
(42.7)
(48.8)
(54.9)
(61.0)
(76.2)
(91.4)
(106.7)
(121.9)
(137.2)
(152.4)
B
0.57
0.62
0.66
0.70
0.76
0.81
0.85
0.89
0.93
0.96
0.99
1.04
1.09
1.13
1.17
1.20
1.28
1.35
1.41
1.47
1.52
1.56
Exposure
C
0.85
0.90
0.94
0.98
1.04
1.09
1.13
1.17
1.21
1.24
1.26
1.31
1.36
1.39
1.43
1.46
1.53
1.59
1.64
1.69
1.73
1.77
D
1.03
1.08
1.12
1.16
1.22
1.27
1.31
1.34
1.38
1.40
1.43
1.48
1.52
1.55
1.58
1.61
1.68
1.73
1.78
1.82
1.86
1.89
Notes:
1. The velocity pressure exposure coefficient Kz may be determined from the following formula:
For 5.0 m. ≤ z ≤ zg
For z < 5.0 m.
Kz = 2.01 (z/zg)2/α
Kz = 2.01 (15/zg)2/α
2. α and zg are tabulated in Table 309.12.7-1.
3. Linear interpolation for intermediate values of height z is acceptable.
4. Exposure categories are defined in Section 309.4.
All rights reserved
108 / 496
FIGURE 309.18.8-1 SOLID FREESTANDING WALLS & SOLID FREESTANDING SIGNS
All rights reserved
109 / 496
FIGURE 309.18.8-2 CHIMNEYS, TANKS, ROOFTOP EQUIPMENT & SIMILAR STRUCTURES
Other Structures
Force Coefficients, Cf
Cross-Section
All Heights
Chimneys, Tanks, Rooftop Equipment, & Similar Structures
All
All
All
Moderately smooth
Rough (D'/D = 0.02)
Very rough (D'/D = 0.08)
1
1.3
1.0
1.0
0.5
0.7
0.8
h/D
7
1.4
1.1
1.2
0.6
0.8
1.0
25
2.0
1.5
1.4
0.7
0.9
1.2
All
0.7
0.8
1.2
Type of Surface
Square (wind normal to face)
Square (wind along diagonal)
Hexagonal or octagonal
Round ( √ > 2.5) ( √
2
D in m, in qz in N/m )
> 5.3,
Round ( √
2.5) ( √
2
, D in m, in qz in N/m )
5.3
Notes:
1. The design wind force shall be calculated based on the area of the structure projected on a plane
normal to the wind direction. The force shall be assumed to act parallel to the wind direction.
2. Linear interpolation is permitted for h/D values other than shown.
3. Notation:
4. For rooftop equipment on buildings with a mean roof height of h ≤ 18.00 m., use Section 309.18.5.1.
D: diameter of circular cross-section and least horizontal dimension of square, hexagonal or
octagonal cross-sections at elevation under consideration, in meters;
D': depth of protruding elements such as ribs and spoilers, in meters; and
h: height of structure, in meters ; and
qz: velocity pressure evaluated at height z above ground, in /m2.
FIGURE 309.18.8-3 OPEN SIGN & LATTICE FRAMEWORKS
Other Structures
All Heights
Open Signs & Lattice Frameworks
Force Coefficients, Cf
Rounded Members

Flat-Sided
Members
< 0.1
0.1 to 0.29
0.3 to 0.7
2.0
1.8
1.6
√
√
√
√
1.2
1.3
1.5
0.8
0.9
1.1
Notes:
1. Signs with openings comprising 30% or more of the gross area are classified as open signs.
2. The calculation of the design wind forces shall be based on the area of all exposed members and elements projected on a plane normal to
the wind direction. Forces shall be assumed to act parallel to the wind direction.
3. The area Af consistent with these force coefficients is the solid area projected normal to the wind direction.
4. Notation:
: ratio of solid area to gross area;
D: diameter of a typical round member, in meters;
qz: velocity pressure evaluated at height z above ground in N/m2.
All rights reserved
110 / 496
FIGURE 309.18.8-4 TRUSSED TOWERS
Other Structures
All Heights
Force Coefficients, Cf
Trussed Towers
Open Structures
Tower Cross Section
Tower Cross Section Cf Square
Triangle
Cf




Notes:
1. For all wind directions considered, the area Af consistent with the specified force coefficients shall be the solid area of a tower face
projected on the plane of that face for the tower segment under consideration.
2. The specified force coefficients are for towers with structural angles or similar flatsided members.
3. For towers containing rounded members, it is acceptable to multiply the specified force coefficients by the following factor when
determining wind forces on such members:
0.51 2 + 0.57, but not > 1.0
4. Wind forces shall be applied in the directions resulting in maximum member forces and reactions. For towers with square cross-sections,
wind forces shall be multiplied by the following factor when the wind is directed along a tower diagonal:
1 + 0.75 , but not > 1.2
5. Wind forces on tower appurtenances such as ladders, conduits, lights, elevators, etc., shall be calculated using appropriate force
coefficients for these elements.
6. Notation:
: ratio of solid area to gross area of one tower face for the segment under consideration.
SECTION 310 RAIN LOADS
310.1 DESIGN RAIN LOADS
Each portion of a roof shall be designed to sustain the load of rainwater that will accumulate on it if
the primary drainage system for that portion is blocked plus the uniform load caused by water that rises
above the inlet of the secondary drainage system at its design flow.
R = 0.0098 (ds + dh)
where:
EQUATION 310.1-1
dh
= Additional depth of water on the undeflected roof above the inlet of secondary drainage
system at its design flow (i.e., the hydraulic head), in mm.
ds
= Depth of water on the undeflected roof up to the inlet of secondary drainage system when the
primary drainage system is blocked (i.e., the static head), in mm.
R
= Rain load on the undeflected roof, in kN/m2.
When the phrase “undeflected roof” is used, deflections from loads (including dead loads) shall not
be considered when determining the amount of rain on the roof.
310.2 PONDING INSTABILITY
For roofs with a slope less than 1.19 degrees (0.0208 rad), the design calculations shall include
verification of adequate stiffness to preclude progressive deflection in accordance with the provisions of
the Section 310.2.
All rights reserved
111 / 496
310.3 NOTATIONS
R = rain load on the undeflected roof, in kN/m2. When the phrase “undeflected roof” is used,
deflections from loads (including dead loads) shall not be considered when determining the amount of
rain on the roof.
ds = depth of water on the undefl ected roof up to the inlet of the secondary drainage system when
the primary drainage system is blocked (i.e., the static head), in mm.
dh = additional depth of water on the undefl ected roof above the inlet of the secondary drainage
system at its design fl ow (i.e., the hydraulic head), in mm.
310.4 ROOF DRAINAGE
Roof drainage systems shall be designed in accordance with the provisions of the code having
jurisdiction. The flow capacity of secondary (overflow) drains or scuppers shall not be less than that of
the primary drains or scuppers.
310.5 CONTROLLED DRAINAGE
Roofs equipped with hardware to control the rate of drainage shall be equipped with a secondary
drainage system at a higher elevation that limits accumulation of water on the roof above that
elevation. Such roofs shall be designed to sustain the load of all rainwater that will accumulate on
them to the elevation of the secondary drainage system plus the uniform load caused by water that
rises above the inlet of the secondary drainage system at its design flow (determined from Section
310.1. Such roofs shall also be checked for ponding instability determined from Section 310.2.
SECTION 311 EARTHQUAKE LOADS
311.1 SCOPE
Every structure, and portion thereof, including nonstructural components that are permanently
attached to structures and their supports and attachments, shall be designed and constructed to
resist the effects of earthquake motions in accordance with this section. The seismic design category
for a structure is permitted to be determined in accordance with Section 311.
Exceptions:
1. Detached one- and two-family dwellings, assigned to Seismic Design Category A, B or C, or
located where the mapped short-period spectral response acceleration, SS, is less than 0.4 g.
2. The seismic-force-resisting system of wood-frame buildings are not required to be analyzed as
specified in this section.
3. Agricultural storage structures intended only for incidental human occupancy.
4. Structures that require special consideration of their response characteristics and
environment that are not addressed by this code such as vehicular bridges, electrical
transmission towers, hydraulic structures, buried utility lines and their appurtenances and
nuclear reactors.
311.2 NOTATIONS
The unit dimensions used with the items covered by the symbols shall be consistent throughout
except where specifically noted. Symbols presented in this section apply only to the seismic
requirements in this standard as indicated.
2
Ach = cross-sectional area (mm ) of a structural member measured out-to-out of transverse
reinforcement
2
A0 = area of the load-carrying foundation (m )
2
Ash = total cross-sectional area of hoop reinforcement (mm ), including supplementary cross-ties,
having a spacing of sh and crossing a section with a core dimension of hc
2
Avd = required area of leg (mm ) of diagonal reinforcement
Ax = torsional amplification factor (Section 311.6.8.4.3)
All rights reserved
112 / 496
ai = the acceleration at level i obtained from a modal analysis
ap = the amplification factor related to the response of a system or component as affected by the type
of seismic attachment
bp = the width of the rectangular glass panel
Cd = deflection amplification factor as given in Table 311.6.2.3.2-1
CR = site-specific risk coefficient at any period
CRS = mapped value of the risk coefficient at short periods as given by Afghanistan Earthquake Risk
Coefficient Map 0.2 Sec
CR1 = mapped value of the risk coefficient at a period of 1 s as given by Afghanistan Earthquake Risk
Coefficient Map 1.0 Sec
Cs = seismic response coefficient determined in Section 311.6.8.1.1 and 311.8.3.1 (dimensionless)
CT = building period coefficient in Section 311.6.8.2.1
Cvx = vertical distribution factor as determined in Section 311.6.8.3
c = distance from the neutral axis of a flexural member to the fiber of maximum compressive strain
(mm)
D = the effect of dead load
Dclear = relative horizontal (drift) displacement, measured over the height of the glass panel under
consideration, which causes initial glass-to-frame contact.
DpI = seismic relative displacement
Ds = the total depth of stratum in Equation 311.8.2.1.2-4 (m)
dC = The total thickness of cohesive soil layers in the top 30 m; see Section 311.9.4.3 (m)
di = The thickness of any soil or rock layer i between 0 and 30 m; see Section 311.9.4.1 (m)
dS = The total thickness of cohesionless soil layers in the top 30 m; see Section 311.9.4.2 (m)
E = effect of horizontal and vertical earthquake- induced forces (Section 311.6.4)
Fa = short-period site coefficient (at 0.2 s-period); see Section 311.4.3
Fi, Fn, Fx = portion of the seismic base shear, V, induced at Level i, n, or x, respectively, as determined
in Section 311.6.8.3
Fp = the seismic force acting on a component of a structure as determined in Sections 311.6.11.1
FPGA = site coefficient for PGA; see Section 311.5.3
Fv = long-period site coefficient (at 1.0 s-period); see Section 311.4.3
fc'= specifi ed compressive strength of concrete used in design
fs'= ultimate tensile strength (MPa) of the bolt, stud, or insert leg wires. For ASTM A307 bolts or A108
studs, it is permitted to be assumed to be 60,000 psi (MPa)
fy = specified yield strength of reinforcement (MPa)
fyh = specified yield strength of the special lateral reinforcement (kPa)
2
G = v s /g = the average shear modulus for the soils beneath the foundation at large strain levels (Pa)
2
G0 = v s0 /g = the average shear modulus for the soils beneath the foundation at small strain levels
(Pa)
g = acceleration due to gravity
H = thickness of soil
h = height of a shear wall measured as the maximum clear height from top of foundation to bottom of
diaphragmframing above, or the maximum clear height from top of diaphragm to bottom of
diaphragm framing above
h = average roof height of structure with respect to the base
= effective height of the building as determined in Section 311.8.2.1.1 or 311.8.3.1 (m)
All rights reserved
113 / 496
hc = core dimension of a component measured to the outside of the special lateral reinforcement
(mm)
hi, hx = the height above the base to Level i or x, respectively
hn = structural height
hp = the height of the rectangular glass panel
hsx = the story height below Level
x = (hx – hx–1)
Ie = the importance factor
I0 = the static moment of inertia of the load-carrying foundation
Ip = the component importance factor
i = the building level referred to by the subscript i; i = 1 designates the first level above the base
Kp = the stiffness of the component or attachment
Ky = the lateral stiffness of the foundation
Kθ = the rocking stiffness of the foundation
KL/r = the lateral slenderness ratio of a compression member measured in terms of its effective length,
KL, and the least radius of gyration of the member cross section, r
k = distribution exponent
= stiffness of the building
ka = coefficient defined
L = overall length of the building (m) at the base in the direction being analyzed
L0 = overall length of the side of the foundation in the direction being analyzed
M0, M01 = the overturning moment at the foundation– soil interface
Mt = torsional moment resulting from eccentricity between the locations of center of mass and the
center of rigidity
Mta = accidental torsional moment
m = a subscript denoting the mode of vibration under consideration; that is, m = 1 for the fundamental
mode
N = standard penetration resistance, ASTM D-1586
N = number of stories above the base (Section 311.6.8.2.1)
= average field standard penetration resistance for the top 30 m
ch = average standard penetration resistance for cohesionless soil layers for the top 30 m
Ni = standard penetration resistance of any soil or rock layer i (between 0 and 30 m)
n = designation for the level that is uppermost in the main portion of the building
PGA = mapped MCEG peak ground acceleration
PGAM = MCEG peak ground acceleration adjusted for Site Class effects
Px = total unfactored vertical design load at and above level x
PI = plasticity index, ASTM D4318
QE = effect of horizontal seismic (earthquake induced) forces
R = response modification coefficient
Rp = component response modification factor
r = a characteristic length of the foundation
ra = characteristic foundation length (m)
rm = characteristic foundation length (m)
SS = mapped MCER, 5 percent damped, spectral response acceleration parameter at short periods
S1 = mapped MCER, 5 percent damped, spectral response acceleration parameter at a period of 1 s
SaM = the site-specific MCER spectral response acceleration parameter at any period
All rights reserved
114 / 496
SDS = design, 5 percent damped, spectral response acceleration parameter at short periods
SD1 = design, 5 percent damped, spectral response acceleration parameter at a period of 1 s as
SMS = the MCER, 5 percent damped, spectral response acceleration parameter at short periods
adjusted for site class effects
SM1 = the MCER, 5 percent damped, spectral response acceleration parameter at a period of 1 s
adjusted for site class effects
su = undrained shear strength
u = average undrained shear strength in top 30 m; see Sections 20.3.3 and 20.4.3, ASTM D2166 or
ASTM D2850
sui = undrained shear strength of any cohesive soil layer i (between 0 and 30 m)
sh = spacing of special lateral reinforcement (mm)
T = the fundamental period of the building
T˜, T˜ 1 = the effective fundamental period(s) of the building
Ta = approximate fundamental period of the building
TL = long-period transition period
Tp = fundamental period of the component and its attachment
T0 = 0.2SD1/SDS
TS = SD1/SDS
T4 = net tension in steel cable due to dead load, prestress, live load, and seismic load
V = total design lateral force or shear at the base
Vt = design value of the seismic base shear
Vx = seismic design shear in story x
˜ = reduced base shear accounting for the effects of soil structure interaction
˜1 = portion of the reduced base shear, ˜, contributed by the fundamental mode
Δ = reduction in V (kN)
ΔV1 = reduction in V1 (kN)
vs = shear wave velocity at small shear strains (greater than 10–3 percent strain) (m/s)
s = average shear wave velocity at small shear strains in top 30 m
vsi = the shear wave velocity of any soil or rock layer i (between 0 and 30 m)
vso = average shear wave velocity for the soils beneath the foundation at small strain levels, (m/s)
W = effective seismic weight of the building. For calculation of seismic-isolated building period, W is
the total effective seismic weight of the building (kN)
W= effective seismic weight of the building (kN)
Wc = gravity load of a component of the building
Wp = component operating weight (N)
w = moisture content (in percent), ASTM D2216
wi, wn, wx = portion of W that is located at or assigned to Level i, n, or x, respectively
x = level under consideration, 1 designates the first level above the base
z = height in structure of point of attachment of component with respect to the base
β = ratio of shear demand to shear capacity for the story between Level x and x – 1
β= fraction of critical damping for the coupled structure-foundation system
β0 = foundation damping factor
= average unit weight of soil (N/m3)
Δ= design story drift
Δfallout = the relative seismic displacement (drift) at which glass fallout from the curtain wall,
storefront, or partition occurs
All rights reserved
115 / 496
Δa = allowable story drift
δmax = maximum displacement at Level x, considering torsion
δM = maximum inelastic response displacement, considering torsion
δMT = total separation distance between adjacent structures on the same property
δavg = the average of the displacements at the extreme points of the structure at Level x
δx = deflection of Level x at the center of the mass at and above Level x
δxe = deflection of Level x at the center of the mass at and above Level x determined by an elastic
analysis
δxm = modal deflection of Level x at the center of the mass at and above Level x
δx , δx1 = deflection of Level x at the center of the mass at and above Level x (mm)
θ= stability coeffi cient for P-delta effects
= a redundancy factor based on the extent of structural redundancy present in a building
s = spiral reinforcement ratio for precast, prestressed piles
= time effect factor
Ω0 = overstrength factor
311.2 EXISTING BUILDINGS
Additions, alterations, repairs or change of occupancy of existing buildings shall be in accordance with
AAC (Afghan Architectural Code).
311.3 SPECIAL INSPECTIONS
Where required by Sections 904.3 through 904.3.5, the statement of special inspections shall
include the special inspections required by Section 904.3.6.
311.4 SEISMIC GROUND MOTION VALUES
Seismic ground motion values shall be determined in accordance with this section.
311.4.1 MAPPED ACCELERATION PARAMETERS
The parameters S1 and Ss shall be determined from the 0.2 and 1-second spectral response
accelerations shown on Figures 311.4.1-1 and 311.4.1-2. Where S1 is less than or equal to 0.04
and Ss is less than or equal to 0.15, the structure is permitted to be assigned to Seismic Design
Category A.
All rights reserved
116 / 496
FIGURE 311.4.1-1 HORISONTAL SPECTRAL RESPONSE ACCELERATION FOR 0.2 SECOND PERIOD (5
PERCENT OF CRITICAL DAMPING) WITH 2 PERCENT PROBABILITY OF EXCEEDANCE IN 50 YEARS
FIGURE 311.4.1-2 HORISONTAL SPECTRAL RESPONSE ACCELERATION FOR 1.0 SECOND PERIOD (5
PERCENT OF CRITICAL DAMPING) WITH 2 PERCENT PROBABILITY OF EXCEEDANCE IN 50 YEARS
All rights reserved
117 / 496
311.4.2 SITE CLASS DEFINITIONS
Based on the site soil properties, the site shall be classified as either Site Class A, B, C, D, E or F in
accordance with Table 311.4.3-1. When the soil properties are not known in sufficient detail to
determine the site class, Site Class D shall be used unless the building official or geotechnical
data determines that Site Class E or F soil is likely to be present at the site.
311.4.3 SITE COEFFICIENTS AND ADJUSTED MAXIMUM CONSIDERED EARTHQUAKE SPECTRAL
RESPONSE ACCELERATION PARAMETERS
The maximum considered earthquake spectral response acceleration for short periods, SMS, and
at 1-second period, SM1, adjusted for site class effects shall be determined by Equations 16-36
and 16-37, respectively:
SMS = FaSs
EQUATION 311.4.3-1
SM1 = Fv S1
EQUATION 311.4.3-2
where:
Fa = Site coefficient defined in Table 311.4.3-1.
Fv = Site coefficient defined in Table 311.4.3-2.
SS = The mapped spectral accelerations for short periods as determined in Section 311.4.1.
S1 = The mapped spectral accelerations for a 1-second period as determined in Section
311.4.1.
TABLE 311.4.3-1 SITE CLASS DEFINITIONS
AVERAGE PROPERTIES IN TOP 30 m., SEE SECTION 311.4.5
SITE
SOIL PROFILE NAME
CLASS
A
Hard rock
B
C
D
E
Rock
Very dense soil and soft rock
Stiff soil profile
Soft soil profile
E
—
F
Soil shear wave velocity, vS ,
Standard penetration
resistance, N
(m/s)
v s > 1500
760 < v s ≤ 1 500
365 < v s ≤ 760
180 ≤ v s ≤ 365
N/A
Soil undrained shear strength, s u ,
(kPa)
N/A
N/A
N/A
s u ≥ 95
N > 50
48 ≤ s u ≤ 95
15 ≤ N ≤ 50
v s < 180
s u < 48
N < 15
Any profile with more than 10 feet of soil having the following characteristics:
1. Plasticity index PI > 20,
2. Moisture content w ≥ 40%, and
3. Undrained shear strength s u < 24 kPa
Any profile containing soils having one or more of the following characteristics:
1. Soils vulnerable to potential failure or collapse under seismic loading such as liquefiable soils, quick
and highly sensitive clays, collapsible weakly cemented soils.
2. Peats and/or highly organic clays (H > 3 m. of peat and/or highly organic clay where
H = thickness of soil)
3. Very high plasticity clays (H > 10 m. with plasticity index PI >75)
4. Very thick soft/medium stiff clays (H > 40 m)
—
N/A = Not applicable
a
TABLE 311.4.3-2 VALUES OF SITE COEFFICIENT Fa
SITE CLASS
A
B
C
D
E
F
All rights reserved
MAPPED SPECTRAL RESPONSE ACCELERATION AT SHORT PERIOD
Ss ≤ 0.25
Ss = 0.50
Ss = 0.75
0.8
0.8
0.8
1.0
1.0
1.0
1.2
1.2
1.1
1.6
1.4
1.2
2.5
1.7
1.2
Note b
Note b
Note b
Ss = 1.00
0.8
1.0
1.0
1.1
0.9
Note b
Ss ≥ 1.25
0.8
1.0
1.0
1.0
0.9
Note b
118 / 496
a. Use straight-line interpolation for intermediate values of mapped spectral response acceleration at
short period, Ss.
b. Values shall be determined in accordance with Section 311.
TABLE 311.4.3-3 VALUES OF SITE COEFFICIENT FV a
SITE CLASS
A
B
C
D
E
F
MAPPED SPECTRAL RESPONSE ACCELERATION AT 1-SECOND PERIOD
S1 0.1
S1 = 0.2
S1 = 0.3
S1 = 0.4
0.8
0.8
0.8
0.8
1.0
1.0
1.0
1.0
1.7
1.6
1.5
1.4
2.4
2.0
1.8
1.6
3.5
3.2
2.8
2.4
Note b
Note b
Note b
Note b
S1 0.5
0.8
1.0
1.3
1.5
2.4
Note b
a. Use straight-line interpolation for intermediate values of mapped spectral response acceleration at
1-second period, S1. b. Values shall be determined in accordance with Section 311.
311.4.4 DESIGN SPECTRAL RESPONSE ACCELERATION PARAMETERS
Five-percent damped design spectral response acceleration at short periods, SDS, and at 1second period, SD1, shall be determined from Equations 311.4.4-1 and 311.4.4-2, respectively:
SDS =2/3SMS
EQUATION 311.4.4-1
SD1 =2/3SM1
EQUATION 311.4.4-2
SMS = The maximum considered earthquake spectral response accelerations for short
period as determined in Section 311.4.3.
SM1 = The maximum considered earthquake spectral response accelerations for 1-second
period as determined in Section 311.4.3.
311.4.5 SITE CLASSIFICATION FOR SEISMIC DESIGN
Site classification for Site Class C, D or E shall be determined from Table 311.4.58-1.
The notations presented below apply to the upper 30 000 mm of the site profile. Profiles
containing distinctly different soil and/or rock layers shall be subdivided into those layers
designated by a number that ranges from 1 to n at the bottom where there is a total of n distinct
layers in the upper
30 m. The symbol i then refers to any one of the layers between 1 and n.
where:
vsi = The shear wave velocity in m/s.
d = The thickness of any layer between 0 and 30 000 mm.
i
where:
vs = ( ∑
)/(∑
)
EQUATION 311.4.5-1
∑
= 30 000 mm
Ni is the Standard Penetration Resistance (ASTM D 1586) not to exceed 300 blows/m as directly
measured in the field without corrections. When refusal is met for a rock layer, Ni shall be taken
as300 blows/m.
N=(∑
)/(∑
)
EQUATION 311.4.5-2
where Ni and di in Equation 16-41 are for cohesionless soil, cohesive soil and rock layers.
All rights reserved
119 / 496
Nch = ( ∑
)/(∑
)
EQUATION 311.4.5-3
where;
∑
= ds
Use di and Ni for cohesionless soil layers only in Equation 16-42.
ds = The total thickness of cohesionless soil layers in the top 30 000 mm.
m = The number of cohesionless soil layers in the top 30 000 mm.
sui = The undrained shear strength in kPa, not to exceed 240 kPa,
Su = dc / ( ∑
)
EQUATION 311.4.5-4
where:
∑
= ds
dc = The total thickness of cohesive soil layers in the top 30 000 mm.
k = The number of cohesive soil layers in the top 30 000 mm.
PI = The plasticity index,
TABLE 311.4.5-1 SITE CLASSIFICATION a
SITE CLASS
v s
N or Nch
su
E
D
C
< 180 m/s
180 to 365 m/s
365 to 760 m/s
< 15
15 to 50
>50
< 48 kPa
48 kPa to 95 kPa
>95 kPa
a: If the su method is and the ch and su criteria differ, select the category with the soils (for example,
use Site Class E instead of D)
w = The moisture content in percent,
Where a site does not qualify under the criteria for Site Class F and there is a total thickness of soft clay
greater than 3000 mm where a soft clay layer is defined by: s u <24 kPa, w ≥ 40 percent, and PI > 20, it
shall be classified as Site Class E.
The shear wave velocity for rock, Site Class B, shall be either measured on site or estimated by a
geotechnical engineer or engineering geologist/seismologist for competent rock with moderate
fracturing and weathering. Softer and more highly fractured and weathered rock shall either be
measured on site for shear wave velocity or classified as Site Class C.
The hard rock category, Site Class A, shall be supported by shear wave velocity measurements either
on site or on profiles of the same rock type in the same formation with an equal or greater degree of
weathering and fracturing. Where hard rock conditions are known to be continuous to a depth of
30 000 mm, surficial shear wave velocity measurements are permitted to be extrapolated to assess v s.
The rock categories, Site Classes A and B, shall not be used if there is more than 3000 mm of soil
between the rock surface and the bottom of the spread footing or mat foundation.
311.4.5.1 STEPS FOR CLASSIFYING A SITE
1. Check for the four categories of Site Class F requiring site-specific evaluation. If the site
corresponds to any of these categories, classify the site as Site Class F and conduct a sitespecific evaluation.
2. Check for the existence of a total thickness of soft clay > 3000 mm where a soft clay layer
is defined by: u< 24 kPa, w ≥ 40 percent and PI > 20. If these criteria are satisfied,
classify the site as Site Class E.
3. ategorize the site using one of the following three methods with vs , N , and su and
computed in all cases as specified.
3.1. vs for the top 30 000 mm (vs method).
3.2. N for the top 30 000 mm (N method).
All rights reserved
120 / 496
3.3. Nch for cohesionless soil layers ( I < 20) in the top 30 000 mm and average, su or
cohesive soil layers ( I 20) in the top 30 000 mm ( su method).
311.4.6 DETERMINATION OF SEISMIC DESIGN CATEGORY
Structures classified as Occupancy Category I, II or III that are located where the mapped spectral
response acceleration parameter at 1-second period, S1, is greater than or equal to 0.75 shall
be assigned to Seismic Design Category E. Structures classified as Occupancy Category IV that are
located where the mapped spectral response acceleration parameter at 1-second period, S1, is
greater than or equal to 0.75 shall be assigned to Seismic Design Category F. All other structures
shall be assigned to a seismic design category based on their occupancy category and the design
spectral response acceleration coefficients, SDS and SD1, determined in accordance with
Section 311.4.4 or the site- specific procedures of this section. Each building and structure shall
be assigned to the more severe seismic design category in accordance with Table 311.4.6-1 or
311.4.6-2, irrespective of the fundamental period of vibration of the structure, T.
TABLE 311.4.6-1 SEISMIC DESIGN CATEGORY BASED ON SHORT-PERIOD RESPONSE ACCELERATIONS
VALUE OF S
SDS < 0.167g
0.167g ≤ SDS < 0.33g
0.33g ≤ SDS < 0.50g
0.50g ≤ SDS
I or II
A
OCCUPANCY CATEGORY
III
A
IV
A
B
C
D
B
C
D
C
D
D
TABLE 311.4.6-2 SEISMIC DESIGN CATEGORY BASED ON 1-SECOND PERIOD RESPONSE ACCELERATION
VALUE OF SD1
SD1 < 0.067g
0.067g ≤ S < 0.133g
I or II
A
OCCUPANCY CATEGORY
III
A
IV
A
B
B
C
0.133g ≤ SD1 < 0.20g
C
C
D
0.20g ≤ SD1
D
D
D
311.4.6.1 ALTERNATIVE SEISMIC DESIGN CATEGORY DETERMINATION
Where S1 is less than 0,75 seismic design category is permitted to be determined from
Table 311.4.6-1 alone when all of the following apply:
1. In each of the two orthogonal directions, the approximate fundamental period of the
structure, Ta, in each of the two orthogonal directions determined in accordance with
Section 311.6.8.2.1, is less than 0.8 Ts determined in accordance with Section 311.4.5.
2. In each of the two orthogonal directions, the fundamental period of the structure used to
calculate the story drift is less than Ts.
3. Equation 311.6.8.1.1-1 is used to determine the seismic response coefficient, Cs.
4. The diaphragms are rigid as defined in Section 311.6.3.1 or, for diaphragms that are
flexible, the distances between vertical elements of the seismic-force-resisting system do
not exceed 12.000 mm.
311.4.6.2 SIMPLIFIED DESIGN PROCEDURE
Where the alternate simplified design procedure of this code is used, the seismic design
category shall be determined accordingly.
311.5 GEOLOGICAL HAZARDS AND GEOTECHNICAL INVESTIGATION
311.5.1 SITE LIMITATION FOR SEISMIC DESIGN CATEGORIES E AND F
A structure assigned to Seismic Design Category E or F shall not be located where there is a
known potential for an active fault to cause rupture of the ground surface at the structure.
All rights reserved
121 / 496
311.5.2 GEOTECHNICAL INVESTIGATION REPORT REQUIREMENTS FOR SEISMIC DESIGN
CATEGORIES C THROUGH F
A geotechnical investigation report shall be provided for a structure assigned to Seismic Design
Category C, D, E, or F in accordance with this section. An investigation shall be conducted and a
report shall be submitted that includes an evaluation of the following potential geologic and
seismic hazards:
a. Slope instability,
b. Liquefaction,
c. Total and differential settlement, and
d. Surface displacement due to faulting or seismically induced lateral spreading or lateral flow.
The report shall contain recommendations for foundation designs or other measures to mitigate
the effects of the previously mentioned hazards.
EXCEPTION: Where approved by the authority having jurisdiction, a site-specifi c geotechnical
report is not required where prior evaluations of nearby sites with similar soil conditions provide
direction relative to the proposed construction.
311.5.3 ADDITIONAL GEOTECHNICAL INVESTIGATION REPORT REQUIREMENTS FOR SEISMIC
DESIGN CATEGORIES D THROUGH F
The geotechnical investigation report for a structure assigned to Seismic Design Category D, E, or
F shall include all of the following, as applicable:
1. The determination of dynamic seismic lateral earth pressures on basement and retaining walls
due to design earthquake ground motions.
2. The potential for liquefaction and soil strength loss evaluated for site peak ground
acceleration, earthquake magnitude, and source characteristics consistent with the MCEG
peak ground acceleration. Peak ground acceleration shall be determined based on either (1) a
site-specifi c study taking into account soil amplifi cation effects as specified in
TABLE 311.5.3-1 SITE COEFFICIENT FPGA
Mapped Maximum Considered Geometric Mean (MCEG) Peak Ground Acceleration, PGA
Site Class
PGA ≤ 0.1
PGA = 0.2
PGA = 0.3
PGA = 0.4
PGA ≥ 0.5
A
0.8
0.8
0.8
0.8
0.8
B
1.0
1.0
1.0
1.0
1.0
C
1.2
1.2
1.1
1.0
1.0
D
1.6
1.4
1.2
1.1
1.0
E
2.5
1.7
1.2
0.9
0.9
the peak ground acceleration PGAM, from Equation 311.5.3-1.
PGAM = FPGA PGA
EQUATION 311.5.3-1
where
PGAM = MCEG peak ground acceleration adjusted for Site Class effects.
PGA = Mapped MCEG peak ground acceleration shown in Afghanistan Earthquake Maps
Maximum Considered Earthquake Mean.
FPGA = Site coefficient from Table 311.5.3-1.
3. Assessment of potential consequences of liquefaction and soil strength loss, including, but not
limited to, estimation of total and differential settlement, lateral soil movement, lateral soil
loads on foundations, reduction in foundation soil-bearing capacity and lateral soil reaction,
soil downdrag and reduction in axial and lateral soil reaction for pile foundations, increases in
soil lateral pressures on retaining walls, and flotation of buried structures.
4. Discussion of mitigation measures such as, but not limited to, selection of appropriate
foundation type and depths, selection of appropriate structural systems to accommodate
anticipated displacements and forces, ground stabilization, or any combination of these
measures and how they shall be considered in the design of the structure.
All rights reserved
122 / 496
311.6 SEISMIC DESIGN REQUIREMENTS FOR BUILDING STRUCTURES
311.6.1 STRUCTURAL DESIGN BASIS
311.6.1.1 BASIC REQUIREMENTS
The seismic analysis and design procedures to be used in the design of building structures
and their members shall be as prescribed in this section. The building structure shall include
complete lateral and vertical force-resisting systems capable of providing adequate strength,
stiffness, and energy dissipation capacity to withstand the design ground motions within the
prescribed limits of deformation and strength demand. The design ground motions shall be
assumed to occur along any horizontal direction of a building structure. The adequacy of the
structural systems shall be demonstrated through the construction of a mathematical model
and evaluation of this model for the effects of design ground motions. The design seismic
forces, and their distribution over the height of the building structure, shall be established in
accordance with one of the applicable procedures indicated in Section 311.6.6 and the
corresponding internal forces and deformations in the members of the structure shall be
determined. An approved alternative procedure shall not be used to establish the seismic
forces and their distribution unless the corresponding internal forces and deformations in
the members are determined using a model consistent with the procedure adopted.
EXCEPTION: As an alternative, the simplified design procedures of Section 12.14 is permitted
to be used in lieu of the requirements of Sections 311.6.1 through 311.6.12, subject to all of
the limitations contained in Section 311.6.14.
311.6.1.2 MEMBER DESIGN, CONNECTION DESIGN, AND DEFORMATION LIMIT
Individual members, including those not part of the seismic force–resisting system, shall be
provided with adequate strength to resist the shears, axial forces, and moments determined
in accordance with this standard, and connections shall develop the strength of the
connected members or the forces indicated in Section 311.6.1.1. The deformation of the
structure shall not exceed the prescribed limits where the structure is subjected to the
design seismic forces.
311.6.1.3 CONTINUOUS LOAD PATH INTERCONNECTION
A continuous load path, or paths, with adequate strength and stiffness shall be provided to
transfer all forces from the point of application to the final point of resistance. All parts of
the structure between separation joints shall be interconnected to form a continuous path
to the seismic force-resisting system, and the connections shall be capable of transmitting
the seismic force (Fp) induced by the parts being connected. Any smaller portion of the
structure shall be tied to the remainder of the structure with elements having a design
strength capable of transmitting a seismic force of 0.133 times the short period design
spectral response acceleration parameter, SDS, times the weight of the smaller portion or 5
percent of the portion’s weight, whichever is greater. This connection force does not apply
to the overall design of the seismic force-resisting system. Connection design forces need
not exceed the maximum forces that the structural system can deliver to the connection.
311.6.1.4 CONNECTION TO SUPPORTS
A positive connection for resisting a horizontal force acting parallel to the member shall be
provided for each beam, girder, or truss either directly to its supporting elements, or to slabs
designed to act as diaphragms. Where the connection is through a diaphragm, then the
member’s supporting element must also be connected to the diaphragm. The connection
shall have a minimum design strength of 5 percent of the dead plus live load reaction.
All rights reserved
123 / 496
311.6.1.5 FOUNDATION DESIGN
The foundation shall be designed to resist the forces developed and accommodate the
movements imparted to the structure by the design ground motions. The dynamic nature of
the forces, the expected ground motion, the design basis for strength and energy dissipation
capacity of the structure, and the dynamic properties of the soil shall be included in the
determination of the foundation design criteria. The design and construction of foundations
shall comply with Section 311.6.13.
311.6.2 STRUCTURAL SYSTEM SELECTION
311.6.2.1. SELECTION AND LIMITATIONS
The basic lateral and vertical seismic force-resisting system shall conform to one of the types
indicated in Table 311.6.2.3.2-1 or a combination of systems as permitted in Sections
311.6.2.3 and 311.6.2.4. Each type is subdivided by the types of vertical elements used to
resist lateral seismic forces. The structural system used shall be in accordance with the
structural system limitations and the limits on structural height, hn, contained in Table
311.6.2.3.2-1. The appropriate response modification coefficient, R, overstrength factor, Ω0,
and the deflection amplification factor, Cd.
311.6.2.2 COMBINATIONS OF FRAMING SYSTEMS IN DIFFERENT DIRECTIONS
Different seismic force-resisting systems are permitted to be used to resist seismic forces
along each of the two orthogonal axes of the structure. Where different systems are used,
the respective R, Cd, and Ω0 coefficients shall apply to each system, including the structural
system limitations contained in Table 311.6.2.3.2-1.
311.6.2.3 COMBINATIONS OF FRAMING SYSTEMS IN THE SAME DIRECTION
Where different seismic force-resisting systems are used in combination to resist seismic
forces in the same direction, other than those combinations considered as dual systems, the
most stringent applicable structural system limitations contained in Table 311.6.2.3.2-1 shall
apply and the design shall comply with the requirements of this section.
311.6.2.3.1 R, Cd, and Ω0 Values for Vertical Combinations
Where a structure has a vertical combination in the same direction, the following
requirements shall apply:
1. Where the lower system has a lower Response Modification Coefficient, R, the design
coefficients (R, Ω0, and Cd) for the upper system are permitted to be used to calculate
the forces and drifts of the upper system. For the design of the lower system, the
design coefficients (R, Ω0, and Cd) for the lower system shall be used. Forces
transferred from the upper system to the lower system shall be increased by
multiplying by the ratio of the higher response modification coefficient to the lower
response modification coefficient.
2. Where the upper system has a lower Response Modification Coefficient, the Design
Coefficients (R,Ω0, and Cd) for the upper system shall be used for both systems.
EXCEPTIONS:
1. Rooftop structures not exceeding two stories in height and 10 percent of the total
structure weight.
2. Other supported structural systems with a weight equal to or less than 10 percent of
the weight of the structure.
3. Detached one- and two-family dwellings of light-frame construction.
All rights reserved
124 / 496
311.6.2.3.2 TWO STAGE ANALYSIS PROCEDURE
A two-stage equivalent lateral force procedure is permitted to be used for structures
having a flexible upper portion above a rigid lower portion, provided the design of the
structure complies with all of the following:
a. The stiffness of the lower portion shall be at least 10 times the stiffness of the upper
portion.
b. The period of the entire structure shall not be greater than 1.1 times the period of the
upper portion considered as a separate structure supported at the transition from
the upper to the lower portion.
c. The upper portion shall be designed as a separate structure using the appropriate
values of R and .
d. The lower portion shall be designed as a separate structure using the appropriate
values of R and . The reactions from the upper portion shall be those determined
from the analysis of the upper portion amplified by the ratio of the R/ of the upper
portion over R/ of the lower portion. This ratio shall not be less than 1.0.
e. The upper portion is analyzed with the equivalent lateral force or modal response
spectrum procedure, and the lower portion is analyzed with the equivalent lateral
force procedure.
Table 311.6.2.3.2-1 Design Coefficients and Factors for Seismic Force-Resisting Systems
Response
Modification
Coefficient,
a
R
Seismic Force-Resisting
System
A. BEARING WALL
SYSTEMS
1. Special reinforced
concrete shear
wallsl, m
2. Ordinary reinforced
concrete shear
wallsl
3. Detailed plain
concrete shear wallsl
4. Ordinary plain
concrete shear wallsl
5. Intermediate precast
shear walls l
6. Ordinary precast
shear wallsl
7. Special reinforced
masonry shear walls
8. Intermediate
reinforced masonry
shear
walls
9. Ordinary reinforced
masonry shear
walls
10. Detailed plain
masonry shear walls
11. Ordinary plain
masonry shear walls
12. Prestressed
masonry shear walls
13. Ordinary reinforced
AAC masonry
shear walls
14. Ordinary plain AAC
All rights reserved
Deflection
Amplification
b
Factor, Cd
Overstrength
g
Factor, Ω0
Structural System Limitations Including
c
Structural Height, hn (m), Limits
Seismic Design Category
d
d
e
B
C
D
E
F
5
2½
5
NL
NL
49
49
31
4
2½
4
NL
NL
NP
NP
NP
2
2½
2
NL
NP
NP
NP
NP
1½
2½
1½
NL
NP
NP
NP
NP
4
2½
4
NL
NL
12
k
12
k
12
3
2½
3
NL
NP
NP
NP
NP
5
2½
3½
NL
NL
49
49
49
3½
2½
2¼
NL
NL
NP
NP
NP
2
2½
1¾
NL
49
NP
NP
NP
2
2½
1¾
NL
NP
NP
NP
NP
1½
2½
1¼
NL
NP
NP
NP
NP
1½
2½
1¾
NL
NP
NP
NP
NP
2
2½
2
NL
11
NP
NP
NP
1½
2½
1½
NL
NP
NP
NP
NP
125 / 496
k
masonry shear
walls
15. Light-frame (wood)
walls sheathed
with wood structural
panels rated for
shear resistance or steel
sheets
16. Light-frame (coldformed steel) walls
sheathed with wood
structural panels
rated for shear
resistance or steel
sheets
17. Light-frame walls
with shear panels of
all other materials
18. Light-frame (coldformed steel) wall
systems using fl at strap
bracing
B. BUILDING FRAME
SYSTEMS
1. Steel eccentrically
braced frames
2. Steel special
concentrically braced
frames
3. Steel ordinary
concentrically braced
frames
4. Special reinforced
concrete shear
wallsl,m
5. Ordinary reinforced
concrete shear wallsl
6. Detailed plain
concrete shear wallsl
7. Ordinary plain
concrete shear wallsl
8. Intermediate precast
shear wallsl
9. Ordinary precast
shear wallsl
10. Steel and concrete
composite
eccentrically braced
frames
11. Steel and concrete
composite special
concentrically braced
frames
12. Steel and concrete
composite ordinary
braced frames
13. Steel and concrete
composite plate
shear walls
14. Steel and concrete
composite special
shear walls
15. Steel and concrete
composite ordinary
All rights reserved
6½
3
4
NL
NL
20
20
20
6½
3
4
NL
NL
20
20
20
2
2½
2
NL
NL
11
NP
NP
4
2
3½
NL
NL
20
20
20
8
2
4
NL
NL
49
49
49
6
2
5
NL
NL
49
49
49
3¼
2
3¼
NL
NL
11
6
2½
5
NL
NL
5
2½
4½
NL
2
2½
2
1½
2½
5
4
j
j
NP
49
49
31
NL
NP
NP
NP
NL
NP
NP
NP
NP
1½
NL
NP
NP
NP
NP
2½
4½
NL
NL
12
k
12
k
12
2½
4
NL
NP
NP
NP
NP
11
k
49
8
2½
4
NL
NL
49
49
5
2
4½
NL
NL
49
49
31
3
2
3
NL
NL
NP
NP
NP
6½
2½
5½
NL
NL
49
49
31
6
2½
5
NL
NL
49
49
31
5
2½
4½
NL
NL
NP
NP
NP
126 / 496
j
shear walls
16. Special reinforced
masonry shear walls
17. Intermediate
reinforced masonry
shear
walls
18. Ordinary reinforced
masonry shear
walls
19. Detailed plain
masonry shear walls
20. Ordinary plain
masonry shear walls
21. Prestressed
masonry shear walls
22. Light-frame (wood)
walls sheathed
with wood structural
panels rated for
shear resistance
23. Light-frame (coldformed steel) walls
sheathed with wood
structural panels
rated for shear
resistance or steel
sheets
24. Light-frame walls
with shear panels of
all other materials
25. Steel bucklingrestrained braced
frames
26. Steel special plate
shear walls
C. MOMENT-RESISTING
FRAME
SYSTEMS
1. Steel special moment
frames
2. Steel special truss
moment frames
3. Steel intermediate
moment frames
4. Steel ordinary
moment frames
5. Special reinforced
concrete moment
framesn
6. Intermediate
reinforced concrete
moment frames
7. Ordinary reinforced
concrete moment
frames
8. Steel and concrete
composite special
moment frames
9. Steel and concrete
composite
intermediate moment
frames
10. Steel and concrete
All rights reserved
5½
2½
4
NL
NL
49
49
31
4
2½
4
NL
NL
NP
NP
NP
2
2½
2
NL
49
NP
NP
NP
2
2½
2
NL
NP
NP
NP
NP
1½
2½
1¼
NL
NP
NP
NP
NP
1½
2½
1¾
NL
NP
NP
NP
NP
7
2½
4½
NL
NL
20
20
20
7
2½
4½
NL
NL
20
20
20
2½
2½
2½
NL
NL
11
NP
NP
8
2½
5
NL
NL
49
49
31
7
2
6
NL
NL
49
49
31
8
3
5½
NL
NL
NL
NL
NL
7
3
5½
NL
NL
49
31
NP
4½
3
4
NL
NL
11
h
NP
h
NP
h
3½
3
3
NL
NL
NP
i
NP
i
NP
i
8
3
5½
NL
NL
NL
NL
NL
5
3
4½
NL
NL
NP
NP
NP
3
3
2½
NL
NP
NP
NP
NP
8
3
5½
NL
NL
NL
NL
NL
5
3
4½
NL
NL
NP
NP
NP
6
3
5½
49
49
31
NP
NP
127 / 496
composite partially
restrained moment
frames
11. Steel and concrete
composite ordinary
moment frames
12. Cold-formed steel—
special bolted
moment framep
D. DUAL SYSTEMS
WITH SPECIAL
MOMENT FRAMES
CAPABLE OF
RESISTING AT LEAST
25% OF
PRESCRIBED SEISMIC
FORCES
1. Steel eccentrically
braced frames
2. Steel special
concentrically braced
frames
3. Special reinforced
concrete shear wallsl
4. Ordinary reinforced
concrete shear
wallsl
5. Steel and concrete
composite
eccentrically braced
frames
6. Steel and concrete
composite special
concentrically braced
frames
7. Steel and concrete
composite plate
shear walls
8. Steel and concrete
composite special
shear walls
9. Steel and concrete
composite ordinary
shear walls
10. Special reinforced
masonry shear walls
11. Intermediate
reinforced masonry
shear
walls
12. Steel bucklingrestrained braced
frames
13. Steel special plate
shear walls
E. DUAL SYSTEMS WITH
INTERMEDIATE
MOMENT
FRAMES CAPABLE OF
RESISTING AT LEAST
25% OF
PRESCRIBED SEISMIC
FORCES
1. Steel special
All rights reserved
3
3
2½
NL
NP
NP
NP
NP
3½
3
o
3½
11
11
11
11
11
8
2½
4
NL
NL
NL
NL
NL
7
2½
5½
NL
NL
NL
NL
NL
7
2½
5½
NL
NL
NL
NL
NL
6
2½
5
NL
NL
NP
NP
NP
8
2½
4
NL
NL
NL
NL
NL
6
2½
5
NL
NL
NL
NL
NL
7½
2½
6
NL
NL
NL
NL
NL
7
2½
6
NL
NL
NL
NL
NL
6
2½
5
NL
NL
NP
NP
NP
5½
3
5
NL
NL
NL
NL
NL
4
3
3½
NL
NL
NP
NP
NP
8
2½
5
NL
NL
NL
NL
NL
8
2½
6½
NL
NL
NL
NL
NL
6
2½
5
NL
NL
11
NP
NP
128 / 496
concentrically braced
framesf
2. Special reinforced
concrete shear wallsl
3. Ordinary reinforced
masonry shear
walls
4. Intermediate
reinforced masonry
shear
walls
5. Steel and concrete
composite special
concentrically braced
frames
6. Steel and concrete
composite ordinary
braced frames
7. Steel and concrete
composite ordinary
shear walls
8. Ordinary reinforced
concrete shear
wallsl
F. SHEAR WALL-FRAME
INTERACTIVE SYSTEM
WITH
ORDINARY
REINFORCED
CONCRETE MOMENT
FRAMES
AND ORDINARY
REINFORCED
CONCRETE SHEAR
WALLSl
G. CANTILEVERED
COLUMN
SYSTEMS DETAILED TO
CONFORM TO THE
REQUIREMENTS FOR:
1. Steel special
cantilever column
systems
2. Steel ordinary
cantilever column
systems
3. Special reinforced
concrete moment
framesn
4. Intermediate
reinforced concrete
moment frames
5. Ordinary reinforced
concrete moment
frames
6. Timber frames
H. STEEL SYSTEMS NOT
SPECIFICALLY DETAILED
FOR
SEISMIC RESISTANCE,
EXCLUDING
CANTILEVER
COLUMN SYSTEMS
All rights reserved
6½
2½
5
NL
NL
49
31
31
3
3
2½
NL
49
NP
NP
NP
3½
3
3
NL
NL
NP
NP
NP
5½
2½
4½
NL
NL
49
31
NP
3½
2½
3
NL
NL
NP
NP
NP
5
3
4½
NL
NL
NP
NP
NP
5½
2½
4½
NL
NL
NP
NP
NP
4½
2½
4
NL
NP
NP
NP
NP
2½
1¼
2½
11
11
11
11
11
1¼
1¼
1¼
11
11
NP
2½
1¼
2½
11
11
11
11
11
1½
1¼
1½
11
11
NP
NP
NP
1
1¼
1
11
NP
NP
NP
NP
1½
1½
1½
11
11
11
NP
NP
3
3
3
NL
NL
NP
NP
NP
i
NP
i
129 / 496
NP
i
a- Response modification coefficient, R, for use throughout the standard. Note R reduces forces to a
strength level, not an allowable stress level.
b- Deflection amplification factor, Cd, for use in Sections 311.6.8.6, 311.6.8.7, and 311.6.9.2.
c- NL = Not Limited and NP = Not Permitted.
d- See Section 311.6.2.5.4 for a description of seismic force-resisting systems limited to buildings with
a structural height, hn, of 70.0 m or less.
e- See Section 311.6.2.5.4 for seismic force-resisting systems limited to buildings with a structural
height, hn, of 48.0 m or less.
f- Ordinary moment frame is permitted to be used in lieu of intermediate moment frame for Seismic
Design Categories B or C.
g-Where the tabulated value of the overstrength factor, Ω0, is greater than or equal to 2½, Ωo is
permitted to be reduced by subtracting the value of ½ for structures with flexible diaphragms.
h- See Section 311.6.2.5.7 for limitations in structures assigned to Seismic Design Categories D, E, or F.
i - See Section 311.6.2.5.6 for limitations in structures assigned to Seismic Design Categories D, E, or F.
j-Steel ordinary concentrically braced frames are permitted in single-story buildings up to a structural
height, hn, of 18.0 m where the dead load of the roof does not exceed 1.00 kN/m2 and in penthouse
structures.
k-An increase in structural height, hn, to 13.0 m is permitted for single story storage warehouse
facilities.
l- A shear wall is defined as a structural wall.
m- The definition of “special structural wall” includes precast and cast-in-pl ace construction.
n- The definition of “special moment frame” includes precast and cast-in-place construction.
o- Alternately, the seismic load effect with overstrength, Emh, is permitted to be based on the
expected strength determined in accordance with AISI S110.
p-Cold-formed steel – special bolted moment frames shall be limited to one-story in height in
accordance with AISI S110.
311.6.2.3.2 R, Cd, AND Ω0 VALUES OF HORIZONTAL COMBINATIONS
The value of the response modification coefficient, R, used for design in the direction
under consideration shall not be greater than the least value of R for any of the systems
utilized in that direction. The deflection amplification factor, Cd, and the overstrength
factor, θ0, shall be consistent with R required in that direction.
EXCEPTION: Resisting elements are permitted to be designed using the least value of R
for the different structural systems found in each independent line of resistance if the
following three conditions are met: (1) Risk Category I or II building, (2) two stories or
less above grade plane, and (3) use of light-frame construction or flexible diaphragms.
The value of R used for design of diaphragms in such structures shall not be greater than
the least value of R for any of the systems utilized in that same direction.
311.6.2.4 COMBINATION FRAMING DETAILING REQUIREMENTS
Structural members common to different framing systems used to resist seismic forces in
any direction shall be designed using the detailing requirements of Section 311.6 required by
the highest response modification coefficient, R, of the connected framing systems.
311.6.2.5 SYSTEM SPECIFIC REQUIREMENTS
The structural framing system shall also comply with the following system specific
requirements of this section.
311.6.2.5.1 DUAL SYSTEM
For a dual system, the moment frames shall be capable of resisting at least 25 percent of
the design seismic forces. The total seismic force resistance is to be provided by the
All rights reserved
130 / 496
combination of the moment frames and the shear walls or braced frames in proportion
to their rigidities.
311.6.2.5.2 CANTILEVER COLUMN SYSTEMS
Cantilever column systems are permitted as indicated in Table 311.6.2.3.2-1 and as
follows. The required axial strength of individual cantilever column elements,
considering only the load combinations that include seismic load effects, shall not
exceed 15 percent of the available axial strength, including slenderness effects.
Foundation and other elements used to provide overturning resistance at the base of
cantilever column elements shall be designed to resist the seismic load effects including
overstrength factor of Section 311.6.4.3.
311.6.2.5.3 INVERTED PENDULUM-TYPE STRUCTURES
Regardless of the structural system selected, inverted pendulums, shall comply with this
section. Supporting columns or piers of inverted pendulum-type structures shall be
designed for the bending moment calculated at the base determined using the
procedures given in Section 311.6.8 and varying uniformly to a moment at the top equal
to one-half the calculated bending moment at the base.
311.6.2.5.4 INCREASED STRUCTURAL HEIGHT LIMIT FOR STEEL ECCENTRICALLY BRACED
FRAMES, STEEL SPECIAL CONCENTRICALLY BRACED FRAMES, STEEL BUCKLINGRESTRAINED BRACED FRAMES, STEEL SPECIAL PLATE SHEAR WALLS AND SPECIAL
REINFORCED SHEAR WALLS
The limits on structural height, hn, in Table 311.6.2.3.2-1 are permitted to be increased
from 50 m to 75 m for structures assigned to Seismic Design Categories D or E and from
30 m to 50 m for structures assigned to Seismic Design Category F provided the seismic
force resisting systems are limited to steel eccentrically braced frames, steel special
concentrically braced frames, steel buckling-restrained braced frames, steel special plate
shear walls, or special reinforced concrete cast-in-place shear walls and both of the
following requirements are met:
1. The structure shall not have an extreme torsional irregularity as defined in Table
311.6.2.3.2-1 (horizontal structural irregularity Type 1b).
2. The steel eccentrically braced frames, steel special concentrically braced frames, steel
buckling restrained braced frames, steel special plate shear walls or special
reinforced cast-in-place concrete shear walls in any one plane shall resist no more
than 60 percent of the total seismic forces in each direction, neglecting accidental
torsional effects.
311.6.2.5.5 SPECIAL MOMENT FRAMES IN STRUCTURES ASSIGNED TO SEISMIC DESIGN
CATEGORIES D THROUGH F
For structures assigned to Seismic Design Categories D, E, or F, a special moment frame
that is used but not required by Table 311.6.2.3.2-1 shall not be discontinued and
supported by a more rigid system with a lower response modification coefficient, R,
unless the requirements of Sections 311.6.3.3.2 and 311.6.3.3.4 are met. Where a
special moment frame is required by Table 12.2-1, the frame shall be continuous to the
base.
311.6.2.5.6 STEEL ORDINARY MOMENT FRAMES
311.6.2.5.6.1 SEISMIC DESIGN CATEGORY D OR E
a. Single-story steel ordinary moment frames in structures assigned to Seismic
Design Category D or E are permitted up to a structural height, hn, of 20 m where
the dead load supported by and tributary to the roof does not exceed 1.00
All rights reserved
131 / 496
kN/m2. In addition, the dead load of the exterior walls more than 10.0 m above
the base tributary to the moment frames shall not exceed 1.00 kN/m2.
EXCEPTION: Single-story structures with steel ordinary moment frames whose
purpose is to enclose equipment or machinery and whose occupants are engaged
in maintenance or monitoring of that equipment, machinery, or their associated
processes shall be permitted to be of unlimited height where the sum of the dead
and equipment loads supported by and tributary to the roof does not exceed
1.00 kN/m2. In addition, the dead load of the exterior wall system including
exterior columns more than 10.0 m above the base shall not exceed 1.00 kN/m2.
For determining compliance with the exterior wall or roof load limits, the weight
of equipment or machinery, including cranes, not self-supporting for all loads
shall be assumed fully tributary to the area of the adjacent exterior wall or roof
not to exceed 55.0 m2 regardless of their height above the base of the structure.
b. Steel ordinary moment frames in structures assigned to Seismic Design Category
D or E not meeting the limitations set forth in Section 311.6.2.5.6.1.a are
permitted within light-frame construction up to a structural height, hn, of 10.0 m
where neither the roof dead load nor the dead load of any floor above the base
supported by and tributary to the moment frames exceeds 1.70 kN/m2. In
addition, the dead load of the exterior walls tributary to the moment frames shall
not exceed 1.00 kN/m2. 311.6.2.5.6.1.a are permitted within light-frame
construction up to a structural height, hn, of 10.0 m where neither the roof dead
load nor the dead load of any floor above the base supported by and tributary to
the moment frames exceeds 1.70 kN/m2. In addition, the dead load of the
exterior walls tributary to the moment frames shall not exceed 1.00 kN/m2.
311.6.2.5.6.2 SEISMIC DESIGN CATEGORY F
Single-story steel ordinary moment frames in structures assigned to Seismic Design
Category F are permitted up to a structural height, hn, of 20 m where the dead load
supported by and tributary to the roof does not exceed 1.00 kN/m2.. In addition, the
dead load of the exterior walls tributary to the moment frames shall not exceed 1.00
kN/m2.
311.6.2.5.7 STEEL INTERMEDIATE MOMENT FRAMES
311.6.2.5.7.1 SEISMIC DESIGN CATEGORY D
a. Single-story steel intermediate moment frames in structures assigned to Seismic
Design Category D are permitted up to a structural height, hn, of 20 m where the
dead load supported by and tributary to the roof does not exceed 1.00 kN/m2. In
addition, the dead load of the exterior walls more than 10.0 m above the base
tributary to the moment frames shall not exceed 1.00 kN/m2.
EXCEPTION: Single-story structures with steel intermediate moment frames
whose purpose is to enclose equipment or machinery and whose occupants are
engaged in maintenance or monitoring of that equipment, machinery, or their
associated processes shall be permitted to be of unlimited height where the sum
of the ead and equipment loads supported by and tributary to the roof does not
exceed 1.00 kN/m2. In addition, the dead load of the exterior wall system
including exterior columns more than 10.0 m above the base shall not exceed
1.00 kN/m2. For determining compliance with the exterior wall or roof load limits,
the weight of equipment or machinery, including cranes, not self-supporting for
all loads shall be assumed fully tributary to the area of the adjacent exterior wall
or roof not to exceed 55.0 m2 regardless of their height above the base of the
structure.
All rights reserved
132 / 496
b. Steel intermediate moment frames in structures assigned to Seismic Design
Category D not meeting the limitations set forth in Section 311.6.2.5.7.1.a are
permitted up to a structural height, hn, of 10.0 m.
311.6.2.5.7.2 SEISMIC DESIGN CATEGORY E
a. Single-story steel intermediate moment frames in structures assigned to Seismic
Design Category E are permitted up to a structural height, hn, of 20 m where the
dead load supported by and tributary to the roof does not exceed 1.00 kN/m2. In
addition, the dead load of the exterior walls more than 10.0 m above the base
tributary to the moment frames shall not exceed 1.00 kN/m2.
EXCEPTION: Single-story structures with steel intermediate moment frames
whose purpose is to enclose equipment or machinery and whose occupants are
engaged in maintenance or monitoring of that equipment, machinery, or their
associated processes shall be permitted to be of unlimited height where the sum
of the dead and equipment loads supported by and tributary to the roof does not
exceed 1.00 kN/m2. In addition, the dead load of the exterior wall system
including exterior columns more than 10.0 m above the base shall not exceed
1.00 kN/m2. For determining compliance with the exterior wall or roof load limits,
the weight of equipment or machinery, including cranes, not self-supporting for
all loads shall be assumed fully tributary to the area of the adjacent exterior wall
or roof not to exceed 55.0 m2 regardless of their height above the base of the
structure.
b. Steel intermediate moment frames in structures assigned to Seismic Design
Category E not meeting the limitations set forth in Section 311.6.2.5.7.2.a are
permitted up to a structural height, hn, of 10.0 m where neither the roof dead
load nor the dead load of any floor above the base supported by and tributary to
the moment frames exceeds 1.70 kN/m2. In addition, the dead load of the
exterior walls tributary to the moment frames shall not exceed 1.00 kN/m2.
311.6.2.5.7.3 SEISMIC DESIGN CATEGORY F
a. Single-story steel intermediate moment frames in structures assigned to Seismic
Design Category F are permitted up to a structural height, hn, of 20 m where the
dead load supported by and tributary to the roof does not exceed 1.00 kN/m2. In
addition, the dead load of the exterior walls tributary to the moment frames shall
not exceed 1.00 kN/m2.
b. Steel intermediate moment frames in structures assigned to Seismic Design
Category F not meeting the limitations set forth in Section 311.6.2.5.7.3.a are
permitted within light-frame construction up to a structural height, hn, of 10.0 m
where neither the roof dead load nor the dead load of any floor above the base
supported by and tributary to the moment frames exceeds 1.70 kN/m2. In
addition, the dead load of the exterior walls tributary to the moment frames shall
not exceed 1.00 kN/m2.
311.6.2.5.7.3. a are permitted within light-frame construction up to a structural
height, hn, of 10.0 m where neither the roof dead load nor the dead load of any
floor above the base supported by and tributary to the moment frames exceeds
1.70 kN/m2. In addition, the dead load of the exterior walls tributary to the
moment frames shall not exceed 1.00 kN/m2.
311.6.2.5.8 SHEAR WALL-FRAME INTERACTIVE SYSTEMS
The shear strength of the shear walls of the shear wall-frame interactive system shall be
at least 75 percent of the design story shear at each story. The frames of the shear wall-
All rights reserved
133 / 496
frame interactive system shall be capable of resisting at least 25 percent of the design
story shear in every story.
311.6.3 DIAPHRAGM FLEXIBILITY, CONFIGURATION IRREGULARITIES, AND REDUNDANCY
311.6.3.1 DIAPGRAGM FLEXIBILITY
The structural analysis shall consider the relative stiffnesses of diaphragms and the vertical
elements of the seismic force-resisting system. Unless a diaphragm can be idealized as either
flexible or rigid in accordance with Sections 311.6.3.1.1, 311.6.3.1.2, or 311.6.3.1.3, the
structural analysis shall explicitly include consideration of the stiffness of the diaphragm (i.e.,
semirigid modeling assumption).
311.6.3.1.1 FLEXIBLE DIAPHRAGM CONDITION
Diaphragms constructed of untopped steel decking or wood structural panels are
permitted to be idealized as flexible if any of the following conditions exist:
a. In structures where the vertical elements are steel braced frames, steel and concrete
composite braced frames or concrete, masonry, steel, or steel and concrete
composite shear walls.
b. In one- and two-family dwellings.
c. In structures of light-frame construction where all of the following conditions are met:
1. Topping of concrete or similar materials is not placed over wood structural panel
diaphragms except for nonstructural topping no greater than 38 mm thick.
2. Each line of vertical elements of the seismic force-resisting system complies with
the allowable story drift of Table 311.6.12.3-1.
311.6.3.1.2 RIGID DIAPHRAGM CONDITION
Diaphragms of concrete slabs or concrete filled metal deck with span-to-depth ratios of
3 or less in structures that have no horizontal irregularities are permitted to be idealized
as rigid.
311.6.3.1.3 CALCULATED FLEXIBLE DIAPHRAGM CONDITION
Diaphragms not satisfying the conditions of Sections 311.6.3.1.1 or 311.6.3.1.2 are
permitted to be idealized as flexible where the computed maximum in-plane deflection
of the diaphragm under lateral load is more than two times the average story drift of
adjoining vertical elements of the seismic force resisting system of the associated story
under equivalent tributary lateral load as shown in Fig. 311.6.3.3.2-1.The loadings used
for this calculation shall be those prescribed by Section 311.6.8.
311.6.3.2 IRREGULAR AND REGULAR CLASSIFICATION
Structures shall be classified as having a structural irregularity based upon the criteria in this
section. Such classification shall be based on their structural configurations.
311.6.3.2.1 HORIZONTAL IRREGULARITY
Structures having one or more of the irregularity types listed in Table 311.6.3.3.2-1 shall
be designated as having a horizontal structural irregularity. Such structures assigned to
the seismic design categories listed in Table 311.6.3.3.2-1 shall comply with the
requirements in the sections referenced in that table.
311.6.3.2.2 VERTICAL IRREGULARITY
Structures having one or more of the irregularity types listed in Table 311.6.3.4.1-1 shall
be designated as having a vertical structural irregularity. Such structures assigned to the
seismic design categories listed in Table 311.6.3.4.1-1 shall comply with the
requirements in the sections referenced in that table.
All rights reserved
134 / 496
EXCEPTIONS:
1. Vertical structural irregularities of Types 1a, 1b, and 2 in Table 311.6.3.4.1-1 do not
apply where no story drift ratio under design lateral seismic force is greater than 130
percent of the story drift ratio of the next story above. Torsional effects need not be
considered in the calculation of story drifts. The story drift ratio relationship for the
top two stories of the structure are not required to be evaluated.
2. Vertical structural irregularities of Types 1a, 1b, and 2 in Table 311.6.3.4.1-1 are not
required to be considered for one-story buildings in any seismic design category or
for two-story buildings assigned to Seismic Design Categories B, C, or D.
311.6.3.3 LIMITATIONS AND ADDITIONAL REQUIREMENTS FOR SYSTEMS WITH
STRUCTURAL IRREGULARITIES
311.6.3.3.1 PROHIBITED HORIZONTAL AND VERTICAL IRREGULARITIES FOR SEISMIC
DESIGN CATEGORIES D THROUGH F
Structures assigned to Seismic Design Category E or F having horizontal irregularity Type
1b of Table 311.6.3.3.2-1 or vertical irregularities Type 1b, 5a, or 5b of Table 12.3-2 shall
not be permitted. Structures assigned to Seismic Design Category D having vertical
irregularity Type 5b of Table 12.3-2 shall not be permitted.
311.6.3.3.2 EXTREME WEAK STORIES
Structures with a vertical irregularity Type 5b as defined in Table 311.6.3.3.2-1, shall not
be over two stories or 9 m in structural height, hn.
FIGURE 31.6.3.3.2-1 Flexible Diaphragm
Table 311.6.3.3.2-1 Horizontal Structural Irregularities
Type
Description
Reference Section
1a.
Torsional Irregularity: Torsional irregularity is defi ned to exist
where the maximum story drift, computed including accidental
torsion with Ax = 1.0, at one end of the structure transverse to an
axis is more than 1.2 times the average of the story drifts at the
two ends of the structure. Torsional irregularity requirements in
the reference sections apply only to structures in which the
diaphragms are rigid or semirigid.
Extreme Torsional Irregularity: Extreme torsional irregularity is
defined to exist where the maximum story drift, computed
including accidental torsion with Ax = 1.0, at one end of the
structure transverse to an axis is more than 1.4 times the average
311.6.3.3.4
311.6.7.3
311.6.8.4.3
311.6.12.1
Table 311.6.6-1
Seismic Design
Category Application
D, E, and F
B, C, D, E, and F
C, D, E, and F
C, D, E, and F
D, E, and F
311.6.3.3.1
311.6.3.3.4
311.6.7.3
311.6.8.4.3
E and F
D
B, C, and D
C and D
1b.
All rights reserved
135 / 496
2.
3.
4.
5.
of the story drifts at the two ends of the structure. Extreme
torsional irregularity requirements in the reference sections apply
only to structures in which the diaphragms are rigid or semirigid.
Reentrant Corner Irregularity: Reentrant corner irregularity is
defined to exist where both plan projections of the structure
beyond a reentrant corner are greater than 15% of the plan
dimension of the structure in the given direction.
Diaphragm Discontinuity Irregularity: Diaphragm discontinuity
irregularity is defi ned to exist where there is a diaphragm with an
abrupt discontinuity or variation in stiffness, including one having a
cutout or open area greater than 50% of the gross enclosed
diaphragm area, or a change in effective diaphragm stiffness of
more than 50% from one story to the next.
Out-of-Plane Offset Irregularity: Out-of-plane offset irregularity is
defi ned to exist where there is a discontinuity in a lateral forceresistance path, such as an out-of-plane offset of at least one of the
vertical elements.
Nonparallel System Irregularity: Nonparallel system irregularity is
defi ned to exist where vertical lateral force-resisting elements are
not parallel to the major orthogonal axes of the seismic forceresisting system.
311.6.12.1
Table 311.6.6-1
C and D
D
311.6.3.3.4
Table 311.6.6-1
D, E, and F
D, E, and F
311.6.3.3.4
Table 311.6.6-1
D, E, and F
D, E, and F
311.6.3.3.3
311.6.3.3.4
311.6.7.3
Table 311.6.6-1
311.6.5.3
311.6.7.3
Table 311.6.6-1
B, C, D, E, and F
D, E, and F
B, C, D, E, and F
D, E, and F
C, D, E, and F
B, C, D, E, and F
D, E, and F
EXCEPTION: The limit does not apply where the “weak” story is capable of resisting a total seismic
force equal to Ω0 times the design force prescribed in Section 311.6.8.
311.6.3.3.3 ELEMENTS SUPPORTING DISCONTINUOUS WALLS OR FRAMES
Columns, beams, trusses, or slabs supporting discontinuous walls or frames of structures
having horizontal irregularity Type 4 of Table 311.6.3.3.2-1 or vertical irregularity Type 4
of Table 311.6.3.4.1-1 shall be designed to resist the seismic load effects including
overstrength factor of Section 311.6.4.3. The connections of such discontinuous
elements to the supporting members shall be adequate to transmit the forces for which
the discontinuous elements were required to be designed.
311.6.3.3.4 INCREASE IN FORCES DUE TO IRREGULARITIES FOR SEISMIC DESIGN
CATEGORIES D THROUGH F
For structures assigned to Seismic Design Category D, E, or F and having a horizontal
structural irregularity of Type 1a, 1b, 2, 3, or 4 in Table 311.6.3.3.2-1 or a vertical
structural irregularity of Type 4 in Table 311.6.3.4.1-1, the design forces determined
from Section 311.6.10.1.1 shall be increased 25 percent for the following elements of
the seismic force-resisting system:
1. Connections of diaphragms to vertical elements and to collectors.
2. Collectors and their connections, including connections to vertical elements, of the
seismic force-resisting system.
EXCEPTION:
Forces calculated using the seismic load effects including overstrength factor of Section
311.6.4.3 need not be increased.
311.6.3.4 REDUNDANCY
A redundancy factor, , shall be assigned to the seismic force-resisting system in each of two
orthogonal directions for all structures in accordance with this section.
311.6.3.4.1 CONDITIONS WHERE VALUE OF ρ IS 1.0
The value of is permitted to equal 1.0 for the following:
1. Structures assigned to Seismic Design Category B or C.
2. Drift calculation and P-delta effects.
3. Design of nonstructural components.
4. Design of nonbuilding structures that are not similar to buildings.
All rights reserved
136 / 496
5. Design of collector elements, splices, and their connections for which the seismic load
effects including overstrength factor of Section 311.6.4.3 are used.
6. Design of members or connections where the seismic load effects including
overstrength factor of Section 311.6.4.3 are required for design.
7. Diaphragm loads determined using Eq. 311.6.10.1.1-1.
8.Design of structural walls for out-of-plane forces, including their anchorage.
Table 311.6.3.4.1-1 VERTICAL STRUCTURAL IRREGULARITIES
Type
Description
Reference Section
1a.
Stiffness-Soft Story Irregularity: Stiffness-soft story irregularity is
defi ned to exist where there is a story in which the lateral stiffness
is less than 70% of that in the story above or less than 80% of the
average stiffness of the three stories above.
Stiffness-Extreme Soft Story Irregularity: Stiffness-extreme soft
story irregularity is defi ned to exist where there is a story in which
the lateral stiffness is less than 60% of that in the story above or
less than 70% of the average stiffness of the three stories above.
Weight (Mass) Irregularity: Weight (mass) irregularity is defi ned to
exist where the effective mass of any story is more than 150% of
the effective mass of an adjacent story. A roof that is lighter than
the fl oor below need not be considered.
Vertical Geometric Irregularity: Vertical geometric irregularity is
defi ned to exist where the horizontal dimension of the seismic
force-resisting system in any story is more than 130% of that in an
adjacent story.
In-Plane Discontinuity in Vertical Lateral Force-Resisting Element
Irregularity: In-plane discontinuity in vertical lateral force-resisting
elements irregularity is defi ned to exist where there is an in-plane
offset of a vertical seismic force-resisting element resulting in
overturning demands on a supporting beam, column, truss, or slab.
Discontinuity in Lateral Strength–Weak Story Irregularity:
Discontinuity in lateral strength–weak story irregularity is defi ned
to exist where the story lateral strength is less than 80% of that in
the story above. The story lateral strength is the total lateral
strength of all seismic-resisting elements sharing the story shear for
the direction under consideration.
Discontinuity in Lateral Strength–Extreme Weak Story Irregularity:
Discontinuity in lateral strength–extreme weak story irregularity is
defined to exist where the story lateral strength is less than 65% of
that in the story above. The story strength is the total strength of
all seismic-resisting elements sharing the story shear for the
direction under consideration.
Table 311.6.6-1
Seismic Design
Category Application
D, E, and F
311.6.3.3.1
Table 311.6.6-1
E and F
D, E, and F
Table 311.6.6-1
D, E, and F
Table 311.6.6-1
D, E, and F
311.6.3.3.3
311.6.3.3.4
Table 311.6.6-1
B, C, D, E, and F
D, E, and F
D, E, and F
311.6.3.3.1
Table 311.6.6-1
E and F
D, E, and F
311.6.3.3.1
311.6.3.3.2
Table 311.6.6-1
D, E, and F
B and C
D, E, and F
1b.
2.
3.
4.
5a.
5b.
311.6.3.4.2 REDUNDANCY FACTOR, ρ, FOR SEISMIC DESIGN CATEGORIS D THROUGH F
or structures assigned to Seismic Design Category D, E, or F,  shall equal 1.3 unless one
of the following two conditions is met, whereby  is permitted to be taken as 1.0:
a. Each story resisting more than 35 percent of the base shear in the direction of interest
shall comply with Table 311.6.4.2.1-1.
b. Structures that are regular in plan at all levels provided that the seismic force-resisting
systems consist of at least two bays of seismic force-resisting perimeter framing on
each side of the structure in each orthogonal direction at each story resisting more
than 35 percent of the base shear. The number of bays for a shear wall shall be
calculated as the length of shear wall divided by the story height or two times the
length of shear wall divided by the story height, hsx, for light-frame construction.
All rights reserved
137 / 496
311.6.4 SEISMIC LOAD EFFECTS AND COMBINATIONS
311.6.4.1 APPLICABILITY
All members of the structure, including those not part of the seismic force-resisting system,
shall be designed using the seismic load effects of Section 311.6.4 unless otherwise
exempted by this standard. Seismic load effects are the axial, shear, and flexural member
forces resulting from application of horizontal and vertical seismic forces as set forth in
Section 311.6.4.2. Where specifically required, seismic load effects shall be modified to
account for overstrength, as set forth in Section 311.6.4.3.
311.6.4.2 SEISMIC LOAD EFFECT
The seismic load effect, E, shall be determined in accordance with the following:
1. E shall be determined in accordance with Equation 311.6.4.2-1 as follows:
E = Eh + Ev
EQUATION 311.6.4.2-1
2. E shall be determined in accordance with Equation 311.6.4.2-2 as follows:
E = Eh – Ev
EQUATION 311.6.4.2-2
where
E = seismic load effect
Eh = effect of horizontal seismic forces as defined in Section 311.6.4.2.1
Ev = effect of vertical seismic forces as defined in Section 311.6.4.2.2
311.6.4.2.1 HORIZONTAL SEISMIC LOAD EFFECT
The horizontal seismic load effect, Eh, shall be determined in accordance with Eq. 12.4-3
as follows:
Eh = QE
EQUATION 311.6.4.2.1-1
Table 311.6.4.2.1-1 REQUIREMENTS FOR EACH STORY RESISTING MORE THAN 35% OF BASE SHEAR
Lateral Force-Resisting Element
Braced frames
Moment frames
Shear walls or wall piers with
a height-to-length ratio greater
than 1.0
Cantilever columns
Other
All rights reserved
Requirement
Removal of an individual brace, or connection thereto, would not result in more than a
33% reduction in story strength, nor does the resulting system have an extreme
torsional irregularity (horizontal structural irregularity Type 1b).
Loss of moment resistance at the beam-to-column connections at both ends of a single
beam would not result in more than a 33% reduction in story strength, nor does the
resulting system have an extreme torsional irregularity (horizontal structural irregularity
Type 1b).
Removal of a shear wall or wall pier with a height-to-length ratio greater than 1.0 within
any story, or collector connections thereto, would not result in more than a 33%
reduction in story strength, nor does the resulting system have an extreme torsional
irregularity (horizontal structural irregularity Type 1b). The shear wall and wall pier
height-to-length ratios are determined as shown in Figure 311.6.4.2.1-1.
Loss of moment resistance at the base connections of any single cantilever column
would not result in more than a 33% reduction in story strength, nor does the resulting
system have an extreme torsional irregularity (horizontal structural irregularity Type 1b).
No requirements
138 / 496
FIGURE 311.6.4.2.1-1 Shear Wall and Wall Pier Height-To-Length Ratio Determination
Where
QE = effects of horizontal seismic forces from V or Fp.
Where required by Section311.6.5.3 or 311.6.5.4, such effects shall result from application of
horizontal forces simultaneously in two directions at right angles to each other  = redundancy factor,
as defined in Section 311.6.3.4
311.6.4.2.2 VERTICAL SEISMIC LOAD EFFECT
The vertical seismic load effect, Ev, shall be determined in accordance with Equation
311.6.4.2.2-1 as follows:
All rights reserved
139 / 496
Ev = 0.2SDSD
EQUATION 311.6.4.2.2-1
where
SDS = design spectral response acceleration parameter at short periods obtained from
Section 311.4.4
D = effect of dead load
EXCEPTIONS: The vertical seismic load effect, Ev, is permitted to be taken as zero for
either of the following conditions:
1. In Equations 311.6.4.2-1, 311.6.4.2-2, 311.6.4.3-1, and 311.6.4.3-2 where SDS is equal
to or less than 0.125.
2. In Equation 311.6.4.2-2 where determining demands on the soil–structure interface of
foundations.
311.6.4.2.3 SEISMIC LOAD COMBINATIONS
Where the prescribed seismic load effect, E, defined in Section 311.6.4.2 is combined
with the effects of other loads as set forth in Section 302, the following seismic load
combinations for structures not subject to flood or atmospheric ice loads shall be used
in lieu of the seismic load combinations in either Section 302.3.1 or 3022.4:
Basic Combinations for Strength Design
5. (1.2 + 0.2SDS)D + QE + L + 0.2S
6. (0.9 – 0.2SDS)D + QE + 1.6H
NOTES:
1. The load factor on L in combination 5 is permitted to equal 0.5 for all occupancies in
which Lo is less than or equal to 4.80 kN/m2, with the exception of garages or areas
occupied as places of public assembly.
2. The load factor on H shall be set equal to zero in combination 7 if the structural action
due to H counteracts that due to E. Where lateral earth pressure provides resistance
to structural actions from other forces, it shall not be included in H but shall be
included in the design resistance.
Basic Combinations for Allowable Stress Design
5. (1.0 + 0.14SDS)D + H + F + 0.7 QE
6. (1.0 + 0.10SDS)D + H + F + 0.525 QE + 0.75L + 0.75(Lr or S or R)
8. (0.6 – 0.14SDS)D + 0.7QE + H
311.6.4.3 SEISMIC LOAD EFFECT INCLUDING OVERSTRENGTH FACTOR
Where specifically required, conditions requiring overstrength factor applications shall be
determined in accordance with the following:
1. For use in load combination 5 in Section 302.3.1 or load combinations 5 and 6 in Section
302.4, E shall be taken equal to Em as determined in accordance with Equation 311.6.4.3-1
as follows:
Em = Emh + Ev
EQUATION 311.6.4.3-1
2. For use in load combination 7 in Section 302.3.1 or load combination 8 in Section 302.4, E
shall be taken equal to Em as determined in accordance with Equation 311.6.4.3-2 as
follows:
All rights reserved
140 / 496
Em = Emh – Ev
EQUATION 311.6.4.3-2
where
Em = seismic load effect including overstrength factor
Emh = effect of horizontal seismic forces including overstrength factor as defined in Section
311.6.4.3.1
Ev = vertical seismic load effect as defined in Section 311.6.4.2.2
311.6.4.3.1 HORIZONTAL SEISMIC LOAD EFFECT WITH OVERSTRENGTH FACTOR
The horizontal seismic load effect with overstrength factor, Emh, shall be determined in
accordance with Equation 311.6.4.3.1-1 as follows:
Emh = ΩoQE
EQUATION 311.6.4.3.1-1
where
QE = effects of horizontal seismic forces from V, Fpx, or Fp as specified in Sections
311.6.8.1 or 311.6.10. Where required by Section 311.6.5.3 or 311.6.5.4, such effects
shall result from application of horizontal forces simultaneously in two directions at right
angles to each other.
Ωo = overstrength factor
EXCEPTION: The value of Emh need not exceed the maximum force that can develop in
the element as determined by a rational, plastic mechanism analysis or nonlinear
response analysis utilizing realistic expected values of material strengths.
311.6.4.3.2 LOAD COMBINATIONS WITH OVERSTRENGTH FACTOR
Where the seismic load effect with overstrength factor, Em, defined in Section 311.6.4.3,
is combined with the effects of other loads as set forth in Section 302, the following
seismic load combination for structures not subject to flood or atmospheric ice loads
shall be used in lieu of the seismic load combinations in either Section 302.3.1 or
302.2.4:
Basic Combinations for Strength Design with Overstrength Factor.
5. (1.2 + 0.2SDS)D + ΩoQE + L + 0.2S
7. (0.9 – 0.2SDS)D + ΩoQE + 1.6H
NOTES:
1. The load factor on L in combination 5 is permitted to equal 0.5 for all occupancies in
which Lo is less than or equal to 4.80 kN/m2, with the exception of garages or areas
occupied as places of public assembly.
2. The load factor on H shall be set equal to zero in combination 7 if the structural action
due to H counteracts that due to E. Where lateral earth pressure provides resistance
to structural actions from other forces, it shall not be included in H but shall be
included in the design resistance.
Basic Combinations for Allowable Stress Design with Overstrength Factor
5. (1.0 + 0.14SDS)D + H + F + 0.7ΩoQE
6. (1.0 + 0.105SDS)D + H + F + 0.525ΩoQE + 0.75L + 0.75(Lr or S or R)
8. (0.6 – 0.14SDS)D + 0.7ΩoQE + H
All rights reserved
141 / 496
311.6.4.3.3 ALLOWABLE STRESS INCREASE FOR LOAD COMBINATIONS WITH
OVERSTRENGTH
Where allowable stress design methodologies are used with the seismic load effect
defined in Section 311.6.4.3 applied in load combinations 5, 6, or 8 of Section 302.4,
allowable stresses are permitted to be determined using an allowable stress increase of
1.2. This increase shall not be combined with increases in allowable stresses or load
combination reductions otherwise permitted by this standard or the material reference
document except for increases due to adjustment factors in accordance with AF&PA
NDS.
311.6.4.4 MINIMUM UPWARD FORCE FOR HORIZONTAL CANTILEVERS FOR SEISMIC
DESIGN CATEGORIES D THROUGH F
In structures assigned to Seismic Design Category D, E, or F, horizontal cantilever structural
members shall be designed for a minimum net upward force of 0.2 times the dead load in
addition to the applicable load combinations of Section 311.6.4.
311.6.5 DIRECTION OF LOADING
311.6.5.1 DIRECTION OF LOADING CRITERIA
The directions of application of seismic forces used in the design shall be those which will
produce the most critical load effects. It is permitted to satisfy this requirement using the
procedures of Section 311.6.5.2 for Seismic Design Category B, Section 311.6.5.3 for Seismic
Design Category C, and Section 311.6.5.4 for Seismic Design Categories D, E, and F.
311.6.5.2 SEISMIC DESIGN CATEGORY B
For structures assigned to Seismic Design Category B, the design seismic forces are
permitted to be applied independently in each of two orthogonal directions and orthogonal
interaction effects are permitted to be neglected.
311.6.5.3 SEISMIC DESIGN CATEGORY C
Loading applied to structures assigned to Seismic Design Category C shall, as a minimum,
conform to the requirements of Section 311.6.5.2 for Seismic Design Category B and the
requirements of this section. Structures that have horizontal structural irregularity Type 5 in
Table 311.6.3.3.2-1 shall use one of the following procedures:
a. Orthogonal Combination Procedure. The structure shall be analyzed using the equivalent
lateral force analysis procedure of Section 311.6.8, the modal response spectrum analysis
procedure of Section 311.6.9, as permitted under Section 311.6.6, with the loading
applied independently in any two orthogonal directions. The requirement of Section
311.6.5.1 is deemed satisfied if members and their foundations are designed for 100
percent of the forces for one direction plus 30 percent of the forces for the perpendicular
direction. The combination requiring the maximum component strength shall be used.
b. Simultaneous Application of Orthogonal Ground Motion. The structure shall be analyzed
using the linear response history procedure or the nonlinear response history procedure ,
as permitted by Section 311.6.6, with orthogonal pairs of ground motion acceleration
histories applied simultaneously.
311.6.5.4 SEISMIC DESIGN CATEGORIES D THROUGH F
Structures assigned to Seismic Design Category D, E, or F shall, as a minimum, conform to
the requirements of Section 311.6.5.3. In addition, any column or wall that forms part of two
or more intersecting seismic force-resisting systems and is subjected to axial load due to
seismic forces acting along either principal plan axis equaling or exceeding 20 percent of the
axial design strength of the column or wall shall be designed for the most critical load effect
due to application of seismic forces in any direction. Either of the procedures of Section
All rights reserved
142 / 496
311.6.5.3 a or b are permitted to be used to satisfy this requirement. Except as required by
Section 311.6.7.3, 2-D analyses are permitted for structures with flexible diaphragms.
311.6.6 ANALYSIS PROCEDURE SELECTION
The structural analysis shall consist of one of the types permitted in Table 311.6.6-1, based on
the structure’s seismic design category, structural system, dynamic properties, and regularity, or
with the approval of the authority having jurisdiction, an alternative generally accepted
procedure is permitted to be used. The analysis procedure selected shall be completed in
accordance with the requirements of the corresponding section referenced in Table 311.6.6-1.
Table 311.6.6-1 Permitted Analytical Procedures
Seismic Design
Category
Structural Characteristics
B, C
D, E, F
All structures
Risk Category I or II buildings not
exceeding 2 stories above the base
Structures
of
light
frame
construction
Structures with no structural
irregularities and not exceeding 49
m in structural height
Structures exceeding 49 m in
structural height with no structural
irregularities and with T < 3.5Ts
Structures not exceeding 49 m in
structural height and having only
horizontal irregularities of
Type 2, 3, 4, or 5 in Table
311.6.3.3.2-1 or vertical
irregularities of Type 4, 5a, or 5b in
Table 311.6.3.4.1-1
All other structures
Equivalent Lateral
Force Analysis,
a
Section 311.6.8
P
P
Modal Response
Spectrum Analysis,
a
Section 311.6.9
P
P
Seismic Response
History Procedures
P
P
P
P
P
P
P
P
P
P
P
P
NP
P
P
P
P
311.6.7 MODELING CRITERIA
311.6.7.1 FOUNDATION MODELING
For purposes of determining seismic loads, it is permitted to consider the structure to be
fixed at the base. Alternatively, where foundation flexibility is considered, it shall be in
accordance with Section 311.6.13.3.
311.6.7.2 EFFECTIVE SEISMIC WEIGHT
The effective seismic weight, W, of a structure shall include the dead load, as defined in
Section 306.1, above the base and other loads above the base as listed below:
1. In areas used for storage, a minimum of 25 percent of the floor live load shall be included.
EXCEPTIONS:
a. Where the inclusion of storage loads adds no more than 5% to the effective seismic
weight at that level, it need not be included in the effective seismic weight.
b. Floor live load in public garages and open parking structures need not be included.
2. Where provision for partitions is in the floor load design, the actual partition weight or a
minimum weight of 0.50 kN/m2 of floor area, whichever is greater.
3. Total operating weight of permanent equipment.
4. Where the flat roof snow load, Pf, exceeds 1.40 kN/m2, 20 percent of the uniform design
snow load, regardless of actual roof slope.
5. Weight of landscaping and other materials at roof gardens and similar areas.
All rights reserved
143 / 496
311.6.7.3 STRUCTURAL MODELING
A mathematical model of the structure shall be constructed for the purpose of determining
member forces and structure displacements resulting from applied loads and any imposed
displacements or P-delta effects. The model shall include the stiffness and strength of
elements that are significant to the distribution of forces and deformations in the structure
and represent the spatial distribution of mass and stiffness throughout the structure. In
addition, the model shall comply with the following:
a. Stiffness properties of concrete and masonry elements shall consider the effects of
cracked sections.
b. For steel moment frame systems, the contribution of panel zone deformations to overall
story drift shall be included. Structures that have horizontal structural irregularity Type
1a, 1b, 4, or 5 of Table 311.6.3.3.2-1 shall be analyzed using a 3-D representation. Where
a 3-D model is used, a minimum of three dynamic degrees of freedom consisting of
translation in two orthogonal plan directions and rotation about the vertical axis shall be
included at each level of the structure. Where the diaphragms have not been classified as
rigid or flexible in accordance with Section 311.6.3.1, the model shall include
representation of the diaphragm’s stiffness characteristics and such additional dynamic
degrees of freedom as are required to account for the participation of the diaphragm in
the structure’s dynamic response.
EXCEPTION: Analysis using a 3-D representation is not required for structures with
flexible diaphragms that have Type 4 horizontal structural irregularities.
311.6.7.4 INTERACTION EFFECTS
Moment-resisting frames that are enclosed or adjoined by elements that are more rigid and
not considered to be part of the seismic force-resisting system shall be designed so that the
action or failure of those elements will not impair the vertical load and seismic forceresisting capability of the frame. The design shall provide for the effect of these rigid
elements on the structural system at structural deformations corresponding to the design
story drift (Δ) as determined in Section 311.6.8.6. In addition, the effects of these elements
shall be considered where determining whether a structure has one or more of the
irregularities defined in Section 311.6.3.2.
311.6.8 EQUIVALENT LATERAL FORCE PROCEDURE
311.6.8.1 SEISMIC BASE SHEAR
The seismic base shear, V, in a given direction shall be determined in accordance with the
following
equation:
V = CsW
EQUATION 311.6.8.1-1
where
Cs = the seismic response coefficient determined in accordance with Section 311.6.8.1.1
W = the effective seismic weight per Section 311.6.7.2
311.6.8.1.1 CALCULATION OF SEISMIC RESPONSE COEFFICIENT
The seismic response coefficient, Cs, shall be determined in accordance with Equation
311.6.8.1.1-1.
C s=S DS/(R/Ie)
EQUATION 311.6.8.1.1-1
where
All rights reserved
144 / 496
SDS = the design spectral response acceleration parameter in the short period range as
determined from Section 311.4.4
R = the response modification factor in Table 311.6.2.3.2-1
Ie = the importance factor determined
The value of Cs computed in accordance with Equation 311.6.8.1.1-1 need not exceed
the following:
C s=S D1/T(R/I e) for T ≤TL
EQUATION 311.6.8.1.1-2
C s=(S D1 TL)/T2(R/I e) for T >TL
EQUATION 311.6.8.1.1-3
Cs shall not be less than
Cs = 0.044SDSIe ≥ 0.01
EQUATION 311.6.8.1.1-4
In addition, for structures located where S1 is equal to or greater than 0.6g, Cs shall not
be less than
Cs = 0.5S1/(R/Ie)
EQUATION 311.6.8.1.1-5
where
Ie and R are as defined in Section 311.6.8.1.1 and SD1 = the design spectral response
acceleration parameter at a period of 1.0 s, as determined from Section 311.4.4
T = the fundamental period of the structure(s) determined in Section 311.6.8.2
TL = long-period transition period(s) determined in Section 311.4.5
S1 = the mapped maximum considered earthquake spectral response acceleration
parameter determined in accordance with Section 311.4.1.
311.6.8.1.2 SOIL STRUCTURE INTERACTION REDUCTION
A soil structure interaction reduction is permitted where determined using Section 311.8
or other generally accepted procedures approved by the authority having jurisdiction.
311.6.8.1.3 MAXIMUM Ss VALUE IN DETERMINATION OF Cs
For regular structures five stories or less above the base and with a period, T, of 0.5 s or
less, Cs is permitted to be calculated using a value of 1.5 for SS.
311.6.8.2 PERIOD DETERMINATION
The fundamental period of the structure, T, in the direction under consideration shall be
established using the structural properties and deformational characteristics of the resisting
elements in a properly substantiated analysis. The fundamental period, T, shall not exceed
the product of the coefficient for upper limit on calculated period (Cu) from Table
311.6.8.2.1-1 and the approximate fundamental period, Ta, determined in accordance with
Section 311.6.8.2.1. As an alternative to performing an analysis to determine the
fundamental period, T, it is permitted to use the approximate building period, Ta, calculated
in accordance with Section 311.6.8.2.1, directly.
311.6.8.2.1 APPROXIMATE FUNDAMENTAL PERIOD
The approximate fundamental period (Ta), in s, shall be determined from the following
equation:
All rights reserved
145 / 496
Ta = Cthn
x
EQUATION 311.6.8.2.1-1
where
hn is the structural height and the coefficients Ct and x are determined from Table
311.6.8.2.1-2. Alternatively, it is permitted to determine the approximate fundamental
period (Ta), in s, from the following equation for structures not exceeding 12 stories
above the base where the seismic force-resisting system consists entirely of concrete or
steel moment resisting frames and the average story height is at least 3 m:
Ta = 0.1N
EQUATION 311.6.8.2.1-2
where N = number of stories above the base.
The approximate fundamental period, Ta, in s for masonry or concrete shear wall
structures is permitted to be determined from Equation 311.6.8.2.1-3 as follows:
Ta=
EQUATION 311.6.8.2.1-3
√
where Cw is calculated from Equation 311.6.8.2.1-4 as follows:
Cw =
∑
( )
( )
EQUATION 311.6.8.2.1-4
where
AB = area of base of structure
Ai = web area of shear wall i
Di = length of shear wall i
hi = height of shear wall i
x = number of shear walls in the building effective in resisting lateral forces in the
direction under consideration
Table 311.6.8.2.1-1 Coefficient for Upper Limit on Calculated Period
Design Spectral Response Acceleration Parameter at 1 s, SD1
≥ 0.4
0.3
0.2
0.15
≤ 0.1
Coefficient Cu
1.4
1.4
1.5
1.6
1.7
Table 311.6.8.2.1-2 Values of Approximate Period Parameters Ct and x
Structure Type
Moment-resisting frame systems in which the frames resist 100% of the required seismic force
and are not enclosed or adjoined by components that are more rigid and will prevent the frames
from deflecting where subjected to seismic forces:
Steel moment-resisting frames
Concrete moment-resisting frames
Steel eccentrically braced frames in accordance with Table 12.2-1 lines B1 or D1
Steel buckling-restrained braced frames
All other structural systems
All rights reserved
Ct
x
0.0724
0.0466
0.0731
0.0731
0.0488
0.8
0.9
0.75
0.75
0.75
146 / 496
311.6.8.3 VERTICAL DISTRIBUTION OF SEISMIC FORCES
The lateral seismic force (Fx) (kN) induced at any level shall be determined from the
following
equations:
Fx = CvxV
EQUATION 311.6.8.3-1
and
Cvx = ∑
EQUATION 311.6.8.3-2
where
Cvx = vertical distribution factor
V = total design lateral force or shear at the base of the structure (kN) wi and
wi and wx = the portion of the total effective seismic weight of the structure (W) located or
assigned to Level i or x
hi and hx = the height (m) from the base to Level i or x
k = an exponent related to the structure period as follows:
for structures having a period of 0.5 s or less, k = 1
for structures having a period of 2.5 s or more, k = 2
for structures having a period between 0.5 and 2.5 s, k shall be 2 or shall be
determined by linear interpolation between 1 and 2
311.6.8.4 HORIZONTAL DISTRIBUTION OF FORCES
The seismic design story shear in any story (Vx) (kN) shall be determined from the following
equation:
Vx = ∑
EQUATION 311.6.8.4-1
where Fi = the portion of the seismic base shear (V) (kN) induced at Level i.
The seismic design story shear (Vx) (kN) shall be distributed to the various vertical elements
of the seismic force-resisting system in the story under consideration based on the relative
lateral stiffness of the vertical resisting elements and the diaphragm.
311.6.8.4.1 INHERENT TORSION
For diaphragms that are not flexible, the distribution of lateral forces at each level shall
consider the effect of the inherent torsional moment, Mt, resulting from eccentricity
between the locations of the center of mass and the center of rigidity. For flexible
diaphragms, the distribution of forces to the vertical elements shall account for the
position and distribution of the masses supported.
311.6.8.4.2 ACCIDENTAL TORSION
Where diaphragms are not flexible, the design shall include the inherent torsional
moment (Mt) resulting from the location of the structure masses plus the accidental
torsional moments (Mta) caused by assumed displacement of the center of mass each
way from its actual location by a distance equal to 5 percent of the dimension of the
structure perpendicular to the direction of the applied forces. Where earthquake forces
are applied concurrently in two orthogonal directions, the required 5 percent
displacement of the center of mass need not be applied in both of the orthogonal
All rights reserved
147 / 496
directions at the same time, but shall be applied in the direction that produces the
greater effect.
311.6.8.4.3 AMPLIFICATION OF ACCIDENTAL TORSIONAL MOMENT
Structures assigned to Seismic Design Category C, D, E, or F, where Type 1a or 1b
torsional irregularity exists as defined in Table 311.6.3.3.2-1 shall have the effects
accounted for by multiplying Mta at each level by a torsional amplification factor (Ax) as
illustrated in Figure 311.6.8.6.1-1 and determined from the following equation:
Ax= (
)
EQUATION 311.6.8.4.3-1
where
δmax = the maximum displacement at Level x computed assuming Ax = 1 (mm)
δavg = the average of the displacements at the extreme points of the structure at Level x
computed assuming Ax = 1 (mm)
The torsional amplification factor (Ax) shall not be less than 1 and is not required to
exceed 3.0. The more severe loading for each element shall be considered for design.
311.6.8.5 OVERTURNING
The structure shall be designed to resist overturning effects caused by the seismic forces
determined in Section 311.6.8.3.
311.6.8.6 STORY DRIFT DETERMINATION
The design story drift (Δ) shall be computed as the difference of the deflections at the
centers of mass at the top and bottom of the story under consideration. See Figure
311.6.8.6.1-2. Where centers of mass do not align vertically, it is permitted to compute the
deflection at the bottom of the story based on the vertical projection of the center of mass
at the top of the story. Where allowable stress design is used, Δ shall be computed using the
strength level seismic forces specified in Section 311.6.8 without reduction for allowable
stress design. For structures assigned to Seismic Design Category C, D, E, or F having
horizontal irregularity Type 1a or 1b of Table 311.6.3.3.2-1, the design story drift, Δ, shall be
computed as the largest difference of the deflections of vertically aligned points at the top
and bottom of the story under consideration along any of the edges of the structure.
The deflection at Level x (δx) (mm) used to compute the design story drift, Δ, shall be
determined in accordance with the following equation:
δ=
EQUATION 311.6.8.6-1
where
Cd = the deflection amplification factor in Table 311.6.12.3-1
δxe = the deflection at the location required by this section determined by an elastic analysis
Ie = the importance factor
311.6.8.6.1 MINIMUM BASE SHEAR FOR COMPUTING DRIFT
The elastic analysis of the seismic force-resisting system for computing drift shall be
made using the prescribed seismic design forces of Section 311.6.8.
EXCEPTION: Eq. 12.8-5 need not be considered for computing drift.
All rights reserved
148 / 496
δavg =
Ax =
FIGURE 311.6.8.6.1-1 Torsional Amplification Factor, Ax
FIGURE 311.6.8.6.1-2 Story Drift Determination
All rights reserved
149 / 496
Story Level 2
F2
= strength-level design earthquake force
δe2
forces
δ2
= elastic displacement computed under strength-level design earthquake
Δ2
= (δe2 – δe1) Cd/IE ≤ Δa (Table 311.6.2.3.2-1)
= Cd δe2/IE = amplified distance
Story Level 1
F1
= strength-level design earthquake force
δe1
forces
δ1
= elastic displacement computed under strength-level design earthquake
Δ1
= δ1 ≤ Δa (Table 311.6.2.3.2-1)
Δi
= Story Drift
Δi/Li
=Story Drift Ratio
δ2
= Total displacement
= Cd δe1/IE = amplified distance
311.6.8.6.2 PERIOD FOR COMPUTING DRIFT
For determining compliance with the story drift limits of Section 311.6.12.1, it is
permitted to determine the elastic drifts, (δxe), using seismic design forces based on the
computed fundamental period of the structure without the upper limit (CuTa) specified
in Section 311.6.8.2.
311.6.8.7 P-DELTA EFFECTS
P-delta effects on story shears and moments, the resulting member forces and moments,
and the story drifts induced by these effects are not required to be considered where the
stability coefficient (θ) as determined by the following equation is equal to or less than 0.10:
θ=
EQUATION 311.6.8.7-1
where
Px = the total vertical design load at and above Level x (kN); where computing Px, no
individual load factor need exceed 1.0
Δ = the design story drift as defined in Section 311.6.8.6 occurring simultaneously with Vx
(mm)
Ie = the importance factor
Vx = the seismic shear force acting between Levels x and x – 1 (kN)
hsx = the story height below Level x (mm)
Cd = the deflection amplification factor in Table 311.6.2.3.2-1
The stability coefficient (θ) shall not exceed θmax determined as follows:
θmax =
EQUATION 311.6.8.7-2
where
All rights reserved
150 / 496
β is the ratio of shear demand to shear capacity for the story between Levels x and x – 1.
This ratio is permitted to be conservatively taken as 1.0. Where the stability coefficient (θ) is
greater than 0.10 but less than or equal to θmax, the incremental factor related to P-delta
effects on displacements and member forces shall be determined by rational analysis.
Alternatively, it is permitted to multiply displacements and member forces by 1.0/(1 – θ).
Where θ is greater than θmax, the structure is potentially unstable and shall be redesigned.
Where the P-delta effect is included in an automated analysis, Equation 311.6.8.7-2 shall still
be satisfied, however, the value of θ computed from Equation 311.6.8.7-1 using the results
of the P-delta analysis is permitted to be divided by (1 + θ) before checking Equation
311.6.8.7-2.
311.6.9 MODAL RESPONSE SPECTRUM ANALYSIS
311.6.9.1 NUMBER OF MODES
An analysis shall be conducted to determine the natural modes of vibration for the
structure. The analysis shall include a sufficient number of modes to obtain a combined
modal mass participation of at least 90 percent of the actual mass in each of the orthogonal
horizontal directions of response considered by the model.
311.6.9.2 MODAL RESPONSE PARAMETERS
The value for each force-related design parameter of interest, including story drifts, support
forces, and individual member forces for each mode of response shall be computed using
the properties of each mode and the response spectra defined in either Section 311.4.5
divided by the quantity R/Ie. The value for displacement and drift quantities shall be
multiplied by the quantity Cd/Ie.
311.6.9.3 COMBINED RESPONSE PARAMETERS
The value for each parameter of interest calculated for the various modes shall be combined
using the square root of the sum of the squares (SRSS) method, the complete quadratic
combination (CQC) method, the complete quadratic combination method as modified by
ASCE 4 (CQC-4), or an approved equivalent approach. The CQC or the CQC-4 method shall be
used for each of the modal values where closely spaced modes have significant
crosscorrelation of translational and torsional response.
311.6.9.4 SCALING DESIGN VALUES OF COMBINED RESPONSE
A base shear (V) shall be calculated in each of the two orthogonal horizontal directions using
the calculated fundamental period of the structure T in each direction and the procedures of
Section 311.6.8.
311.6.9.4.1 SCALING OF FORCES
Where the calculated fundamental period exceeds CuTa in a given direction, CuTa shall
be used in lieu of T in that direction. Where the combined response for the modal base
shear (Vt) is less than 85 percent of the calculated base shear (V) using the equivalent
lateral force procedure, the forces shall be multiplied by 0.85−V Vt :
where
V = the equivalent lateral force procedure base shear, calculated in accordance with this
section and Section 311.6.8
Vt = the base shear from the required modal combination
All rights reserved
151 / 496
311.6.9.4.2 SCALING OF DRIFTS
Where the combined response for the modal base shear (Vt) is less than 0.85CsW, and
where Cs is determined in accordance with Equation 311.6.8.1.1-5, drifts shall be
multiplied by 0.85/( Cs W/ V t)
311.6.9.5 HORIZONTAL SHEAR DISTRIBUTION
The distribution of horizontal shear shall be in accordance with Section 311.6.8.4 except that
amplification of torsion in accordance with Section 311.6.8.4.3 is not required where
accidental torsion effects are included in the dynamic analysis model.
311.6.9.6 P-DELTA EFFECTS
The P-delta effects shall be determined in accordance with Section 311.6.8.7. The base shear
used to determine the story shears and the story drifts shall be determined in accordance
with Section 311.6.8.6.
311.6.9.7 SOIL STRUCTURE INTERACTION REDUCTION
A soil structure interaction reduction is permitted where determined using Section 311.8 or
other generally accepted procedures approved by the authority having jurisdiction.
311.6.10 DIAPHRAGMS, CHORDS, AND COLLECTORS
311.6.10.1 DIAPHRAGM DESIGN
Diaphragms shall be designed for both the shear and bending stresses resulting from design
forces. At diaphragm discontinuities, such as openings and reentrant corners, the design
shall assure that the dissipation or transfer of edge (chord) forces combined with other
forces in the diaphragm is within shear and tension capacity of the diaphragm.
311.6.10.1.1 DIAPHRAGM DESIGN FORCES
Floor and roof diaphragms shall be designed to resist design seismic forces from the
structural analysis, but shall not be less than that determined in accordance with
Equation 311.6.10.1.1-1 as follows:
∑
Fpx = ∑
EQUATION 311.6.10.1.1-1
where
Fpx = the diaphragm design force
Fi = the design force applied to Level i
wi = the weight tributary to Level i
wpx = the weight tributary to the diaphragm at Level x The force determined from
Equation 311.6.10.1.1-1 shall not be less than
Fpx = 0.2SDSIewpx
EQUATION 311.6.10.1.1-2
The force determined from Equation 311.6.10.1.1-1 need not exceed
Fpx = 0.4SDSIewpx
EQUATION 311.6.10.1.1-3
Where the diaphragm is required to transfer design seismic force from the vertical
resisting elements above the diaphragm to other vertical resisting elements below the
diaphragm due to offsets in the placement of the elements or to changes in relative
All rights reserved
152 / 496
lateral stiffness in the vertical elements, these forces shall be added to those
determined from Equation 311.6.10.1.1-1. The redundancy factor, , applies to the
design of diaphragms in structures assigned to Seismic Design Category D, E, or F. For
inertial forces calculated in accordance with Equation 311.6.10.1.1-1, the redundancy
factor shall equal 1.0. For transfer forces, the redundancy factor, , shall be the same as
that used for the structure. For structures having horizontal or vertical structural
irregularities of the types indicated in Section 311.6.3.3.4, the requirements of that
section shall also apply.
311.6.10.2 COLLECTOR ELEMENTS
Collector elements shall be provided that are capable of transferring the seismic forces
originating in other portions of the structure to the element providing the resistance to
those forces.
311.6.10.2.1 COLLECTOR ELEMENTS REQUIRING LOAD COMBINATIONS WITH
OVERSTREGTH FACTOR FOR SEISMIC DESIGN CATEGORIES C THROUGH F
In structures assigned to Seismic Design Category C, D, E, or F, collector elements
(see Figure 311.6.10.2.1-1) and their connections including connections to vertical
elements shall be designed to resist the maximum of the following:
1. Forces calculated using the seismic load effects including overstrength factor of
Section 311.6.4.3 with seismic forces determined by the Equivalent Lateral Force
procedure of Section 311.6.8 or the Modal Response Spectrum Analysis
procedure of Section 311.6.9.
2. Forces calculated using the seismic load effects including overstrength factor of
Section 311.6.4.3 with seismic forces determined by Equation 311.6.10.1.1-1.
3. Forces calculated using the load combinations of Section 311.6.4.2.3 with seismic
forces determined by Equation 311.6.10.1.1-2. Transfer forces as described in
Section 311.6.10.1.1 shall be considered.
EXCEPTIONS:
1. The forces calculated above need not exceed those calculated using the load
combinations of Section 311.6.4.2.3 with seismic forces determined by Equation
311.6.10.1.1-3.
FIGURE 311.6.10.2.1-1 Collectors
All rights reserved
153 / 496
311.6.11 STRUCTURAL WALLS AND THEIR ACNHORAGE
311.6.11.1 DESIGN FOR OUT-OF-PLANE FORCES
Structural walls and their anchorage shall be designed for a force normal to the surface
equal to Fp = 0.4SDSIe times the weight of the structural wall with a minimum force of 10
percent of the weight of the structural wall. Interconnection of structural wall elements and
connections to supporting framing systems shall have sufficient ductility, rotational capacity,
or sufficient strength to resist shrinkage, thermal changes, and differential foundation
settlement when combined with seismic forces.
311.6.11.2 ANCHORAGE OF STRUCTURAL WALLS AND TRANSFER OF DESIGN FORCES INTO
DIAPHRAGMS
311.6.11.2.1 WALL ANCHORAGE FORCES
The anchorage of structural walls to supporting construction shall provide a direct
connection capable of resisting the following:
Fp = 0.4SDSkaIeWp
EQUATION 311.6.11.2.1-1
Fp shall not be taken less than 0.2 kaIeWp.
k a=1.0 + (L f /100)
EQUATION 311.6.11.2.1-1
ka need not be taken larger than 2.0.
where
Fp = the design force in the individual anchors
SDS = the design spectral response acceleration parameter at short periods per Section
311.4.4
Ie = the importance factor
ka = amplification factor for diaphragm flexibility
Lf = the span, in feet, of a flexible diaphragm that provides the lateral support for the
wall; the span is measured between vertical elements that provide lateral support to the
diaphragm in the direction considered; use zero for rigid diaphragms
Wp = the weight of the wall tributary to the anchor Where the anchorage is not located
at the roof and all diaphragms are not flexible, the value from Equation 311.6.11.2.1-1 is
permitted to be multiplied by the factor (1 + 2z/h)/3, where z is the height of the anchor
above the base of the structure and h is the height of the roof above the base.
Structural walls shall be designed to resist bending between anchors where the anchor
spacing exceeds 1,200 mm.
311.6.11.2.2 ADDITIONAL REQUIREMENTS FOR DIAPHRAGMS IN STRUCTURES
ASSIGNED TO SEISMIC DESIGN CATEGORIES C THROUGH F
311.6.11.2.2.1
Transfer of Anchorage Forces into Diaphragm Diaphragms shall be provided with
continuous ties or struts between diaphragm chords to distribute these anchorage
forces into the diaphragms. Diaphragm connections shall be positive, mechanical, or
welded. Added chords are permitted to be used to form subdiaphragms to transmit
the anchorage forces to the main continuous cross-ties. The maximum length-towidth ratio of the structural subdiaphragm shall be 2.5 to 1. Connections and
All rights reserved
154 / 496
anchorages capable of resisting the prescribed forces shall be provided between the
diaphragm and the attached components. Connections shall extend into the
diaphragm a sufficient distance to develop the force transferred into the diaphragm.
311.6.12 DRIFT AND DEFORMATION
311.6.12.1 STORY DRIFT LIMIT
The design story drift (Δ) as determined in Sections 311.6.8.6 and 311.6.9.2, shall not exceed
the allowable story drift (Δa) as obtained from Table 311.6.12.3-1 for any story.
311.6.12.1.1 MOMENT FRAMES IN STRUCTURES ASSIGNED TO SEISMIC DESIGN
CATEGORIES D THROUGH F
For seismic force-resisting systems comprised solely of moment frames in structures
assigned to Seismic Design ategories D, E, or F, the design story drift (Δ) shall not
exceed Δa/ for any story.  shall be determined in accordance with Section 311.6.3.4.2.
311.6.12.2 DIAPHRAGM DEFLECTION
The deflection in the plane of the diaphragm, as determined by engineering analysis, shall
not exceed the permissible deflection of the attached elements. Permissible deflection shall
be that deflection that will permit the attached element to maintain its structural integrity
under the individual loading and continue to support the prescribed loads.
311.6.12.3 STRUCTURAL SEPARATION
All portions of the structure shall be designed and constructed to act as an integral unit in
resisting seismic forces unless separated structurally by a distance sufficient to avoid
damaging contact as set forth in this section.
Separations shall allow for the maximum inelastic response displacement (δM). δM shall be
determined at critical locations with consideration for translational and torsional
displacements of the structure including torsional amplifications, where applicable, using
the following equation:
δM =( C dδ max)/I e
EQUATION 311.6.12.3-1
Where δmax = maximum elastic displacement at the critical location.
Adjacent structures on the same property shall be separated by at least δMT, determined as
follows:
δMT = √(
) (
)
EQUATION 311.6.12.3-2
where δM1 and δM2 are the maximum inelastic response displacements of the adjacent
structures at their adjacent edges.
Where a structure adjoins a property line not common to a public way, the structure shall be
set back from the property line by at least the displacement δM of that structure.
EXCEPTION: Smaller separations or property line setbacks are permitted where justified by
rational analysis based on inelastic response to design ground motions.
All rights reserved
155 / 496
Table 311.6.12.3-1 Allowable Story Drift, Δa
a,b
Structure
Structures, other than masonry shear wall structures, 4 stories or less
above the base, with interior walls, partitions, ceilings, and exterior wall
systems that have been designed to accommodate the story drifts.
Masonry cantilever shear wall structures
Other masonry shear wall structures
All other structures
I or II
0.025hsx
Risk Category
III
0.020hsx
IV
0.015hsx
0.010hsx
0.007hsx
0.020hsx
0.010hsx
0.007hsx
0.015hsx
0.010hsx
0.007hsx
0.010hsx
311.6.13 FOUNDATION DESIGN
311.6.13.1 DESIGN BASIS
The design basis for foundations shall be as set forth in Section 311.6.1.5.
311.6.13.2 MATERIALS OF CONSTURCTION
Materials used for the design and construction of foundations shall comply with the
requirements of Section 311.7.
311.6.13.3 FOUNDATION LOAD-DEFORMATION CHARACTERISTICS
Where foundation flexibility is included for the linear analysis procedures in Section 311.6,
the load-deformation characteristics of the foundation–soil system (foundation stiffness)
shall be modeled in accordance with the requirements of this section. The linear loaddeformation behavior of foundations shall be represented by an equivalent linear stiffness
using soil properties that are compatible with the soil strain levels associated with the design
earthquake motion. The strain-compatible shear modulus, G, and the associated straincompatible shear wave velocity, vS, needed for the evaluation of equivalent linear stiffness
shall be determined using the criteria in Section 311.8.2.1.1 or based on a site-specific study.
A 50 percent increase and decrease in stiffness shall be incorporated in dynamic analyses
unless smaller variations can be justified based on field measurements of dynamic soil
properties or direct measurements of dynamic foundation stiffness. The largest values of
response shall be used in design.
311.6.13.4 REDUCTION OF FOUNDATION OVERTURNING
Overturning effects at the soil–foundation interface are permitted to be reduced by 25
percent for foundations of structures that satisfy both of the following conditions:
a. The structure is designed in accordance with the Equivalent Lateral Force Analysis as set
forth in Section 12.8.
b. The structure is not an inverted pendulum or cantilevered column type structure.
Overturning effects at the soil–foundation interface are permitted to be reduced by 10
percent for foundations of structures designed in accordance with the modal analysis
requirements of Section 311.6.9.
311.6.13.5 REQUIREMENTS FOR STRUCTURES ASSIGNED TO SEISMIC DESIGN CATEGORY C
In addition to the requirements of Section 311.5.2, the following foundation design
requirements shall apply to structures assigned to Seismic Design Category C.
311.6.13.5.1 FOUNDATION TIES
Individual pile caps, drilled piers, or caissons shall be interconnected by ties. All ties shall
have a design strength in tension or compression at least equal to a force equal to 10
percent of SDS times the larger pile cap or column factored dead plus factored live load
unless it is demonstrated that equivalent restraint will be provided by reinforced
concrete beams within slabs on grade or reinforced concrete slabs on grade or
All rights reserved
156 / 496
confinement by competent rock, hard cohesive soils, very dense granular soils, or other
approved means.
311.6.13.5.2 PILE ANCHORAGE REQUIREMENTS
Anchorage of piles shall comply with this section. Where required for resistance to uplift
forces, anchorage of steel pipe (round HSS sections), concrete-filled steel pipe or H piles
to the pile cap shall be made by means other than concrete bond to the bare steel
section.
EXCEPTION: Anchorage of concrete-filled steel pipe piles is permitted to be
accomplished using deformed bars developed into the concrete portion of the pile.
311.6.13.6 REQUIREMENTS FOR STRUCTURES ASSIGNED TO SEISMIC DESIGN CATEGORIES
D THROUGH F
In addition to the requirements of Sections 311.5.2 and 311.5.3, the following foundation
design requirements shall apply to structures assigned to Seismic Design Category D, E, or F.
Design and construction of concrete foundation elements shall conform to the requirements
of Section 521.8, except as modified by the requirements of this section.
EXCEPTION: Detached one- and two-family dwellings of light-frame construction not
exceeding two stories above grade plane need only comply with the requirements for
Sections 311.5.2, 311.5.3 (Items 2 through 4), 311.6.13.2, and 311.6.13.5.
311.6.13.6.1 FOUNDATION TIES
Individual pile caps, drilled piers, or caissons shall be interconnected by ties. In addition,
individual spread footings founded on soil defined in Section 311.9 as Site Class E or F
shall be interconnected by ties. All ties shall have a design strength in tension or
compression at least equal to a force equal to 10 percent of SDS times the larger pile cap
or column factored dead plus factored live load unless it is demonstrated that equivalent
restraint will be provided by reinforced concrete beams within slabs on grade or
reinforced concrete slabs on grade or confinement by competent rock, hard cohesive
soils, very dense granular soils, or other approved means.
311.6.13.6.2 GENERAL PILE DESIGN REQUIREMENT
Piling shall be designed and constructed to withstand deformations from earthquake
ground motions and structure response. Deformations shall include both free-field soil
strains (without the structure) and deformations induced by lateral pile resistance to
structure seismic forces, all as modified by soil–pile interaction.
311.6.13.6.3 BATTER PILES
Batter piles and their connections shall be capable of resisting forces and moments from
the load combinations with overstrength factor of Section 311.6.4.3.2 or 311.6.14.3.2.2.
Where vertical and batter piles act jointly to resist foundation forces as a group, these
forces shall be distributed to the individual piles in accordance with their relative
horizontal and vertical rigidities and the geometric distribution of the piles within the
group.
311.6.13.6.4 PILE ANCHORAGE REQUIREMENTS
In addition to the requirements of Section 311.6.13.5.3, anchorage of piles shall comply
with this section. Design of anchorage of piles into the pile cap shall consider the
combined effect of axial forces due to uplift and bending moments due to fixity to the
pile cap. For piles required to resist uplift forces or provide rotational restraint,
anchorage into the pile cap shall comply with the following:
1. In the case of uplift, the anchorage shall be capable of developing the least of the
nominal tensile strength of the longitudinal reinforcement in a concrete pile, the
All rights reserved
157 / 496
nominal tensile strength of a steel pile, and 1.3 times the pile pullout resistance, or
shall be designed to resist the axial tension force resulting from the seismic load
effects including overstrength factor of Section 311.6.4.3 or 311.6.14.3.2. The pile
pullout resistance shall be taken as the ultimate frictional or adhesive force that can
be developed between the soil and the pile plus the pile and pile cap weight.
2. In the case of rotational restraint, the anchorage shall be designed to resist the axial
and shear forces and moments resulting from the seismic load effects including
overstrength factor of Section 311.6.4.3 or 311.6.14.3.2 or shall be capable of
developing the full axial, bending, and shear nominal strength of the pile.
311.6.13.6.5 PILE SOIL INTERACTION
Pile moments, shears, and lateral deflections used for design shall be established
considering the interaction of the shaft and soil. Where the ratio of the depth of
embedment of the pile to the pile diameter or width is less than or equal to 6, the pile is
permitted to be assumed to be flexurally rigid with respect to the soil.
311.6.13.6.6 PILE GROUP EFFECTS
Pile group effects from soil on lateral pile nominal strength shall be included where pile
centerto-center spacing in the direction of lateral force is less than eight pile diameters
or widths. Pile group effects on vertical nominal strength shall be included where pile
center-to-center spacing is less than three pile diameters or widths.
311.6.14 SIMPLIFIED ALTERNATIVE STRUCTURAL DESIGN CRITERIA FOR SIMPLE BEARING WALL
OR BUILDING FRAME SYSTEMS
311.6.14.1 GENERAL
311.6.14.1.1 SIMPLIFIED DESIGN PROCEDURE
The procedures of this section are permitted to be used in lieu of other analytical
procedures for the analysis and design of simple buildings with bearing wall or building
frame systems, subject to all of the limitations listed in this section. Where these
procedures are used, the seismic design category shall be determined from Table
311.4.6-1 using the value of SDS from Section 311.6.14.8.1. The simplified design
procedure is permitted to be used if the following limitations are met:
1. The structure shall qualify for Risk Category I or II in accordance with Table 305.1-1.
2. The site class, defined in Section 311.9, shall not be class E or F.
3. The structure shall not exceed three stories above grade plane.
4. The seismic force-resisting system shall be either a bearing wall system or building
frame system, as indicated in Table 311.6.14-1.
5. The structure shall have at least two lines of lateral resistance in each of two major
axis directions.
6. At least one line of resistance shall be provided on each side of the center of mass in
each direction.
7. For structures with flexible diaphragms, overhangs beyond the outside line of shear
walls or braced frames shall satisfy the following:
a ≤ d/5
EQUATION 311.6.14.1.1-1
where
a = the distance perpendicular to the forces being considered from the extreme edge of
the diaphragm to the line of vertical resistance closest to that edge
d = the depth of the diaphragm parallel to the forces being considered at the line of
vertical resistance closest to the edge
All rights reserved
158 / 496
8. For buildings with a diaphragm that is not flexible, the distance between the center of
rigidity and the center of mass parallel to each major axis shall not exceed 15 percent of
the greatest width of the diaphragm parallel to that axis. In addition, the following two
equations shall be satisfied:
∑
∑
(
)
∑
EQUATION
∑
(
)
∑
EQUATION
311.6.14.1.1-2
∑
311.6.14.1.1-3
where (see Figure 311.6.14.1.1-1)
k1i = the lateral load stiffness of wall i or braced frame i parallel to major axis 1
k2j = the lateral load stiffness of wall j or braced frame j parallel to major axis 2
d1i = the distance from the wall i or braced frame i to the center of rigidity,
perpendicular to major axis 1
d2j = the distance from the wall j or braced frame j to the center of rigidity,
perpendicular to major axis 2
e1 = the distance perpendicular to major axis 1 between the center of rigidity and the
center of mass
b1 = the width of the diaphragm perpendicular to major axis 1
e2 = the distance perpendicular to major axis 2 between the center of rigidity and the
center of mass
b2 = the width of the diaphragm perpendicular to major axis 2
m = the number of walls and braced frames resisting lateral force in direction 1
n = the number of walls and braced frames resisting lateral force in direction 2
Equation 311.6.14.1.1-2 and 311.6.14.1.1-3 need not be checked where a structure
fulfills all the following limitations:
1. The arrangement of walls or braced frames is symmetric about each major axis
direction.
2. The distance between the two most separated lines of walls or braced frames is at
least 90 percent of the dimension of the structure perpendicular to that axis
direction.
3. The stiffness along each of the lines considered for item 2 above is at least 33 percent
of the total stiffness in that axis direction.
4. Lines of resistance of the seismic force-resisting system shall be oriented at angles of
no more than 15° from alignment with the major orthogonal horizontal axes of the
building.
5. The simplified design procedure shall be used for each major orthogonal horizontal
axis direction of the building.
6. System irregularities caused by in-plane or out-of-plane offsets of lateral forceresisting elements shall not be permitted.
EXCEPTION: Out-of-plane and in-plane offsets of shear walls are permitted in two-story
buildings of light-frame construction provided that the framing supporting the upper
wall is designed for seismic force effects from overturning of the wall amplified by a
factor of 2.5.
7. The lateral load resistance of any story shall not be less than 80 percent of the story
above.
All rights reserved
159 / 496
Table 311.6.14.1.1-1 Design Coefficients and Factors for Seismic Force-Resisting Systems for
Simplified Design Procedure
Seismic Force-Resisting System
A. BEARING WALL SYSTEMS
1. Special reinforced concrete shear walls
2. Ordinary reinforced concrete shear walls
3. Detailed plain concrete shear walls
4. Ordinary plain concrete shear walls
5. Intermediate precast shear walls
6. Ordinary precast shear walls
7. Special reinforced masonry shear walls
8. Intermediate reinforced masonry shear walls
9. Ordinary reinforced masonry shear walls
10. Detailed plain masonry shear walls
11. Ordinary plain masonry shear walls
12. Prestressed masonry shear walls
13. Light-frame (wood) walls sheathed with wood structural panels
rated for shear resistance
14. Light-frame (cold-formed steel) walls sheathed with wood structural
panels rated for shear resistance or steel sheets
15. Light-frame walls with shear panels of all other materials
16. Light-frame (cold-formed steel) wall systems using fl at strap bracing
B. BUILDING FRAME SYSTEMS
1. Steel eccentrically braced frames
2. Steel special concentrically braced frames
3. Steel ordinary concentrically braced frames
4. Special reinforced concrete shear walls
5. Ordinary reinforced concrete shear walls
6. Detailed plain concrete shear walls
7. Ordinary plain concrete shear walls
8. Intermediate precast shear walls
9. Ordinary precast shear walls
10. Steel and concrete composite eccentrically braced frames
11. Steel and concrete composite special concentrically braced frames
12. Steel and concrete composite ordinary braced frames
13. Steel and concrete composite plate shear walls
14. Steel and concrete composite special shear walls
15. Steel and concrete composite ordinary shear walls
16. Special reinforced masonry shear walls
17. Intermediate reinforced masonry shear walls
18. Ordinary reinforced masonry shear walls
19. Detailed plain masonry shear walls
20. Ordinary plain masonry shear walls
21. Prestressed masonry shear walls
22. Light-frame (wood) walls sheathed with wood structural panels
rated for shear resistance or steel sheets
23. Light-frame (cold-formed steel) walls sheathed with wood structural
panels rated for shear resistance or steel sheets
24. Light-frame walls with shear panels of all other materials
25. Steel buckling-restrained braced frames
26. Steel special plate shear walls
b
Response
Modification
a
Coefficient, R
Limitations
Seismic Design Category
B
C
D, E
5
4
2
1½
4
3
5
3½
2
2
1½
1½
6½
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
NP
NP
P
NP
P
P
NP
NP
NP
NP
P
P
NP
NP
NP
c
40
NP
P
NP
NP
NP
NP
NP
P
6½
P
P
P
2
4
P
P
P
P
NP
P
8
6
3¼
6
5
2
1½
5
4
8
5
3
6½
6
5
5½
4
2
2
1½
1½
7
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
NP
NP
P
NP
P
P
P
P
P
P
P
P
NP
NP
NP
NP
P
P
P
P
P
NP
NP
NP
c
40
NP
P
P
NP
P
P
NP
P
NP
NP
NP
NP
NP
P
7
P
P
P
2½
8
7
P
P
P
P
P
P
NP
P
P
d
d
a: Response modification coefficient, R, for use throughout the standard.
b: P = permitted; NP = not permitted.
c: Light-frame walls with shear panels of all other materials are not permitted in Seismic Design
Category E.
d: Light-frame walls with shear panels of all other materials are permitted up to 10.6 m in structural
height, hn, in Seismic Design Category D and are not permitted in Seismic Design Category E.
All rights reserved
160 / 496
FIGURE 311.6.14.1.1-1 Notation Used in Torsion Check for Nonflexible Diaphragms
311.6.14.1.2 NOTATIONS
D = The effect of dead load
E = The effect of horizontal and vertical earthquake-induced forces
Fa = Acceleration-based site coefficient, see Section 311.6.14.8.1
Fi = The portion of the seismic base shear, V, induced at Level i
Fp = The seismic design force applicable to a particular structural component
Fx = See Section 311.6.14.8.2
hi = The height above the base to Level i
hx = The height above the base to Level x
Level i = The building level referred to by the subscript i; i = 1 designates the first level
above the base
Level n = The level that is uppermost in the main portion of the building
Level x = See “Level i”
QE = The effect of horizontal seismic forces
R = The response modifi cation coefficient as given in Table 311.6.14.1.1-1
SDS = See Section 311.6.14.8.1
SS = See Section 311.4.1
All rights reserved
161 / 496
V = The total design shear at the base of the structure in the direction of interest, as
determined using the procedure of 311.6.14.8.1
Vx = The seismic design shear in Story x. See Section 311.6.14.8.3
W = See Section 311.6.14.8.1
Wc = Weight of wall
Wp = Weight of structural component
wi = The portion of the effective seismic weight, W, located at or assigned to Level i
wx = See Section 311.6.14.8.2
311.6.14.2 DESIGN BASIS
The structure shall include complete lateral and vertical force-resisting systems with
adequate strength to resist the design seismic forces, specified in this section, in
combination with other loads. Design seismic forces shall be distributed to the various
elements of the structure and their connections using a linear elastic analysis in accordance
with the procedures of Section 311.6.14.8. The members of the seismic force-resisting
system and their connections shall be detailed to conform with the applicable requirements
for the selected structural system as indicated in Section 311.6.14.4.1. A continuous load
path, or paths, with adequate strength and stiffness shall be provided to transfer all forces
from the point of application to the final point of resistance. The foundation shall be
designed to accommodate the forces developed.
311.6.14.3 SEISMIC LOAD EFFECTS AND COMBINATIONS
All members of the structure, including those not part of the seismic force-resisting system,
shall be designed using the seismic load effects of Section 311.6.14.3 unless otherwise
exempted by this standard. Seismic load effects are the axial, shear, and flexural member
forces resulting from application of horizontal and vertical seismic forces as set forth in
Section 311.6.14.3.1. Where specifically required, seismic load effects shall be modified to
account for overstrength, as set forth in Section 311.6.14.3.2.
311.6.14.3.1 SEISMIC LOAD EFFECT
The seismic load effect, E, shall be determined in accordance with the following:
1. For use in load combination 5 in Section 302.3.1 or load combinations 5 and 6 in
Section 302.4.1, E shall be determined in accordance with Equation 311.6.14.3.1-1 as
follows:
E = Eh + Ev
EQUATION 311.6.14.3.1-1
2. For use in load combination 7 in Section 302.3.1 or load combination 8 in Section
3022.4.1, E shall be determined in accordance with Equation 311.6.14.3.1-2 as
follows:
E = Eh – Ev
EQUATION 311.6.14.3.1-2 (12.14-4)
Where
E = seismic load effect
Eh = effect of horizontal seismic forces as defined in Section 311.6.14.3.1.1
Ev = effect of vertical seismic forces as defined in Section 311.6.14.3.1.2
311.6.14.3.1.1
Horizontal Seismic Load Effect The horizontal seismic load effect, Eh, shall be
determined in accordance with Eq. 12.14-5 as follows:
All rights reserved
162 / 496
Eh = QE
EQUATION 311.6.14.3.1.1-1
where
QE = effects of horizontal seismic forces from V or Fp as specified in Sections
311.6.14.7.5 and 311.6.14.8.1
311.6.14.3.1.2
Vertical Seismic Load Effect The vertical seismic load effect, Ev, shall be determined
in accordance with Eq. 12.14-6 as follows:
Ev = 0.2SDSD
EQUATION 311.6.14.3.1.2-1
where
SDS = design spectral response acceleration parameter at short periods obtained
from Section 311.4.4
D = effect of dead load
EXCEPTION: The vertical seismic load effect, Ev, is permitted to be taken as zero for
either of the following conditions:
1. In Equations 311.6.4.2.1-1, 311.6.4.2.2-1, 311.6.4.3.1-1, and 311.6.8.1-1 where SDS
is equal to or less than 0.125.
2. In Equation 311.6.4.2.2-1 where determining demands on the soil–structure
interface of foundations.
311.6.14.3.1.3 SEISMIC LOAD COMBINATIONS
Where the prescribed seismic load effect, E, defined in Section 311.6.14.3.1 is
combined with the effects of other loads, the following seismic load combinations
for structures not subject to fl ood or atmospheric ice loads shall be used in lieu of
the seismic load combinations in Sections 302.3.1 or 302.4:
Basic Combinations for Strength Design
5. (1.2 + 0.2SDS)D + QE + L + 0.2S
7. (0.9 – 0.2SDS)D + QE + 1.6H
NOTES:
1. The load factor on L in combination 5 is permitted to equal 0.5 for all occupancies
2
in which Lo is less than or equal to 4.80 kN/m , with the exception of garages or
areas occupied as places of public assembly.
2. The load factor on H shall be set equal to zero in combination 7 if the structural
action due to H counteracts that due to E. Where lateral earth pressure provides
resistance to structural actions from other forces, it shall not be included in H but
shall be included in the design resistance.
Basic Combinations for Allowable Stress Design
5. (1.0 + 0.14SDS)D + H + F + 0.7QE
6. (1.0 + 0.105SDS)D + H + F + 0.525QE + 0.75L +0.75(Lr or S or R)
8. (0.6 – 0.14SDS)D + 0.7QE + H
311.6.14.3.2 SEISMIC LOAD EFFECT INCLUDING A 2.5 OVERSTRENGTH FACTOR
Where specifically required, conditions requiring overstrength factor applications shall
be determined in accordance with the following:
All rights reserved
163 / 496
1. For use in load combination 5 in Section 302.3.1 or load combinations 5 and 6 in
Section 302.4.1, E shall be taken equal to Em as determined in accordance with Equation
311.6.14.3.2-1 as follows:
Em = Emh + Ev
EQUATION 311.6.14.3.2-1
2. For use in load combination 7 in Section 302.3.1 or load combination 8 in Section
302.4.1, E shall be taken equal to Em as determined in accordance with Equation
311.6.14.3.2-2 as follows:
Em = Emh – Ev
EQUATION 311.6.14.3.2-2
where
Em = seismic load effect including overstrength factor
Emh = effect of horizontal seismic forces including overstrength factor as defined in
Section 311.6.14.3.2.1
Ev = vertical seismic load effect as defined in Section 311.6.14.3.1.2
311.6.14.3.2.1 Horizontal Seismic Load Effect with a 2.5 Overstrength Factor The
horizontal seismic load effect with overstrength factor, Emh, shall be determined in
accordance with Equation 311.6.14.3.2-3 as follows:
Emh = 2.5QE
EQUATION 311.6.14.3.2-3
where
QE = effects of horizontal seismic forces from V or Fp as specified in Sections
311.6.14.7.5 and 311.6.14.8.1
EXCEPTION: The value of Emh need not exceed the maximum force that can develop
in the element as determined by a rational, plastic mechanism analysis or nonlinear
response analysis utilizing realistic expected values of material strengths.
311.6.14.3.2.2 LOAD COMBINATIONS WITH OVERSTRENGTH FACTOR
Where the seismic load effect with overstrength factor, Em, defined in Section
311.6.14.3.2, is combined with the effects of other loads, the following seismic load
combinations for structures not subject to flood or atmospheric ice loads shall be
used in lieu of the seismic load combinations in Section 302.3.1 or 302.4.1:
Basic Combinations for Strength Design with Overstrength Factor
5. (1.2 + 0.2SDS)D + 2.5QE + L + 0.2S
7. (0.9 – 0.2SDS)D + 2.5QE + 1.6H
NOTES:
1. The load factor on L in combination 5 is permitted to equal 0.5 for all occupancies
2
in which Lo is less than or equal to 4.79 kN/m , with the exception of garages or
areas occupied as places of public assembly.
2. The load factor on H shall be set equal to zero in combination 7 if the structural
action due to H counteracts that due to E. Where lateral earth pressure provides
resistance to structural actions from other forces, it shall not be included in H,
but shall be included in the design resistance.
All rights reserved
164 / 496
Basic Combinations for Allowable Stress Design with Overstrength Factor
5. (1.0 + 0.14SDS)D + H + F + 1.75QE
6. (1.0 + 0.105SDS)D + H + F + 1.313QE + 0.75L + 0.75(Lr or S or R)
8. (0.6 – 0.14SDS)D + 1.75QE + H
311.6.14.3.2.3 ALLOWABLE STRESS INCREASE FOR LOAD COMBINATIONS WITH
OVERSTRENGTH
Where allowable stress design methodologies are used with the seismic load effect
defined in Section 311.6.14.3.2 applied in load combinations 5, 6, or 8 of Section
302.4.1, allowable stresses are permitted to be determined using an allowable stress
increase of 1.2. This increase shall not be combined with increases in allowable
stresses or load combination reductions otherwise permitted by this standard or the
material reference document except that combination with the duration of load
increases permitted in AF&PA NDS is permitted.
311.6.14.4 SEISMIC FORCE-RESISTING SYSTEMS
311.6.14.4.1 SELECTION AND LIMITATIONS
The basic lateral and vertical seismic force-resisting system shall conform to one of the
types indicated in Table 311.6.14.1.1-1 and shall conform to all of the detailing
requirements referenced in the table. The appropriate response modification
coefficient, R, indicated in Table 311.6.14.1.1-1 shall be used in determining the base
shear and element design forces as set forth in the seismic requirements of this
standard. Special framing and detailing requirements are indicated in Section 311.6.14.7
for structures assigned to the various seismic design categories.
311.6.14.4.2 COMBINATIONS OF FRAMING SYSTEMS
311.6.14.4.2.1 HORIZONTAL COMBINATIONS
Different seismic force-resisting systems are permitted to be used in each of the two
principal orthogonal building directions. Where a combination of different structural
systems is utilized to resist lateral forces in the same direction, the value of R used
for design in that direction shall not be greater than the least value of R for any of
the systems utilized in that direction.
EXCEPTION: For buildings of light-frame construction or having flexible diaphragms
and that are two stories or less above grade plane, resisting elements are permitted
to be designed using the least value of R of the different seismic force-resisting
systems found in each independent line of framing. The value of R used for design of
diaphragms in such structures shall not be greater than the least value for any of the
systems utilized in that same direction.
311.6.14.4.2.2 VERTICAL COMBINATIONS
Different seismic force-resisting systems are permitted to be used in different
stories. The value of R used in a given direction shall not be greater than the least
value of any of the systems used in that direction.
311.6.14.2.3 COMBINATION FRAMING DETAILING REQUIREMENTS
The detailing requirements of Section 311.6.14.7 required by the higher response
modification coefficient, R, shall be used for structural members common to
systems having different response modification coefficients.
All rights reserved
165 / 496
311.6.14.5 DIAPHRAGM FLEXIBILITY
Diaphragms constructed of steel decking (untopped), wood structural panels, or similar
panelized construction are permitted to be considered flexible.
311.6.14.6 APPLICATION OF LOADING
The effects of the combination of loads shall be considered as prescribed in Section
311.6.14.3. The design seismic forces are permitted to be applied separately in each
orthogonal direction and the combination of effects from the two directions need not be
considered. Reversal of load shall be considered.
311.6.14.7 DESIGN AND DETAILING REQUIREMENTS
The design and detailing of the members of the seismic force-resisting system shall comply
with the requirements of this section. The foundation shall be designed to resist the forces
developed and accommodate the movements imparted to the structure by the design
ground motions. The dynamic nature of the forces, the expected ground motion, the design
basis for strength and energy dissipation capacity of the structure, and the dynamic
properties of the soil shall be included in the determination of the foundation design
criteria. The design and construction of foundations shall comply with Section 311.6.13.
311.6.14.7.1 CONNECTIONS
All parts of the structure between separation joints shall be interconnected, and the
connection shall be capable of transmitting the seismic force, Fp, induced by the parts
being connected. Any smaller portion of the structure shall be tied to the remainder of
the structure with elements having a strength of 0.20 times the short period design
spectral response acceleration coefficient, SDS, times the weight of the smaller portion
or 5 percent of the portion’s weight, whichever is greater. A positive connection for
resisting a horizontal force acting parallel to the member shall be provided for each
beam, girder, or truss either directly to its supporting elements, or to slabs designed to
act as diaphragms. Where the connection is through a diaphragm, then the member’s
supporting element must also be connected to the diaphragm. The connection shall
have minimum design strength of 5 percent of the dead plus live load reaction.
311.6.14.7.2 OPENINGS OR REENTRANT BUILDING CORNERS
Except where as otherwise specifically provided for in this standard, openings in shear
walls, diaphragms, or other plate-type elements, shall be provided with reinforcement
at the edges of the openings or reentrant corners designed to transfer the stresses into
the structure. The edge reinforcement shall extend into the body of the wall or
diaphragm a distance sufficient to develop the force in the reinforcement.
EXCEPTION: Shear walls of wood structural panels are permitted where designed in
accordance with AF&PA SDPWS for perforated shear walls or AISI S213 for Type II shear
walls.
311.6.14.7.3 COLLECTOR ELEMENTS
Collector elements shall be provided with adequate strength to transfer the seismic
forces originating in other portions of the structure to the element providing the
resistance to those forces (see Figure 311.6.10.2.1-1). Collector elements, splices, and
their connections to resisting elements shall be designed to resist the forces defined in
Section 311.6.14.3.2.
EXCEPTION: In structures, or portions thereof, braced entirely by light-frame shear
walls, collector elements, splices, and connections to resisting elements are permitted to
be designed to resist forces in accordance with Section 311.6.14.7.4.
All rights reserved
166 / 496
311.6.14.7.4 DIAPHRAGMS
Floor and roof diaphragms shall be designed to resist the design seismic forces at each
level, Fx, calculated in accordance with Section 311.6.14.8.2. Where the diaphragm is
required to transfer design seismic forces from the vertical-resisting elements above the
diaphragm to other vertical-resisting elements below the diaphragm due to changes in
relative lateral stiffness in the vertical elements, the transferred portion of the seismic
shear force at that level, Vx, shall be added to the diaphragm design force. Diaphragms
shall provide for both the shear and bending stresses resulting from these forces.
Diaphragms shall have ties or struts to distribute the wall anchorage forces into the
diaphragm. Diaphragm connections shall be positive, mechanical, or welded type
connections.
311.6.14.7.5 ANCHORAGE OF STRUCTURAL WALLS
Structural walls shall be anchored to all fl oors, roofs, and members that provide out-ofplane lateral support for the wall or that are supported by the wall. The anchorage shall
provide a positive direct connection between the wall and fl oor, roof, or supporting
member with the strength to resist the out-of-plane force given by Equation
311.6.14.7.5-1:
Fp =0.4kaSDSWp
EQUATION 311.6.14.7.5-1
Fp shall not be taken less than 0.2ka Wp.
k a=1+( L f/100)
EQUATION 311.6.14.7.5-1
ka need not be taken larger than 2.0 where
Fp = the design force in the individual anchors
ka = amplification factor for diaphragm flexibility
Lf = the span, in feet, of a flexible diaphragm that provides the lateral support for the
wall; the span is measured between vertical elements that provide lateral support to the
diaphragm in the direction considered; use zero for rigid diaphragms
SDS = the design spectral response acceleration at short periods per Section 311.6.14.8.1
Wp = the weight of the wall tributary to the anchor
311.6.14.7.5.1
Transfer of Anchorage Forces into Diaphragms Diaphragms shall be provided with
continuous ties or struts between diaphragm chords to distribute these anchorage
forces into the diaphragms. Added chords are permitted to be used to form
subdiaphragms to transmit the anchorage forces to the main continuous cross-ties.
The maximum length-towidth ratio of the structural subdiaphragm shall be 2.5 to 1.
Connections and anchorages capable of resisting the prescribed forces shall be
provided between the diaphragm and the attached components. Connections shall
extend into the diaphragm a sufficient distance to develop the force transferred into
the diaphragm.
311.6.14.7.6 BEARING WALLS AND SHEAR WALLS
Exterior and interior bearing walls and shear walls and their anchorage shall be designed
for a force equal to 40 percent of the short period design spectral response acceleration
SDS times the weight of wall, Wc, normal to the surface, with a minimum force of 10
percent of the weight of the wall. Interconnection of wall elements and connections to
supporting framing systems shall have sufficient ductility, rotational capacity, or
All rights reserved
167 / 496
sufficient strength to resist shrinkage, thermal changes, and differential foundation
settlement where combined with seismic forces.
311.6.14.7.7 ANCHORAGE OF NONSTRUCTURAL SYSTEMS
All portions or components of the structure shall be anchored for the seismic force, Fp,
prescribed therein.
311.6.14.8 SIMPLIFIED LATERAL FORCE ANALYSIS PROCEDURE
An equivalent lateral force analysis shall consist of the application of equivalent static lateral
forces to a linear mathematical model of the structure. The lateral forces applied in each
direction shall sum to a total seismic base shear given by Section 311.6.14.8.1 and shall be
distributed vertically in accordance with Section 311.6.14.8.2. For purposes of analysis, the
structure shall be considered fixed at the base.
311.6.14.8.1 SEISMIC BASE SHEAR
The seismic base shear, V, in a given direction shall be determined in accordance with
Equation 311.6.14.8.1-1:
V=( FSDS/ R) W
EQUATION 311.6.14.8.1-1
where
SDS= 2/3FaSs
Where
Fa is permitted to be taken as 1.0 for rock sites, 1.4 for soil sites, or determined in
accordance with Section 311.4.3. For the purpose of this section, sites are permitted to
be considered to be rock if there is no more than 3 m of soil between the rock surface
and the bottom of spread footing or mat foundation. In calculating SDS, Ss shall be in
accordance with Section 311.4.1, but need not be taken larger than 1.5.
F = 1.0 for buildings that are one story above grade plane
F = 1.1 for buildings that are two stories above grade plane
F = 1.2 for buildings that are three stories above grade plane
R = the response modification factor from Table 311.6.14.1.1-1
W = effective seismic weight of the structure that includes the dead load, above grade
plane and other loads above grade plane as listed in the following text:
1. In areas used for storage, a minimum of 25 percent of the floor live load shall be
included.
EXCEPTIONS:
a. Where the inclusion of storage loads adds no more than 5% to the effective seismic
weight at that
level, it need not be included in the effective seismic weight.
b. Floor live load in public garages and open parking structures need not be included.
2. Where provision for partitions is required in the floor load design, the actual partition
2
weight, or a minimum weight of 0.48 kN/m of floor area, whichever is greater.
3. Total operating weight of permanent equipment.
2
4. Where the flat roof snow load, Pf, exceeds 1.40 kN/m , 20 percent of the uniform
design snow load, regardless of actual roof slope.
5. Weight of landscaping and other materials at roof gardens and similar areas.
311.6.14.8.2 VERTICAL DISTRIBUTION
The forces at each level shall be calculated using the following equation:
All rights reserved
168 / 496
F x =(wx / W) V
EQUATION 311.6.14.8.2-1
where
wx = the portion of the effective seismic weight of the structure, W, at level x.
311.6.14.8.3 HORIZONTAL SHEAR DISTRIBUTION
The seismic design story shear in any story, Vx (kN), shall be determined from the
following equation:
Vx = ∑
EQUATION 311.6.14.8.3-1
Where
Fi = the portion of the seismic base shear, V (kN) induced at Level i.
311.6.14.8.3.1 FLEXIBLE DIAPHRAGM STRUCTURES
The seismic design story shear in stories of structures with flexible diaphragms, as
defined in Section 311.6.14.5, shall be distributed to the vertical elements of the
seismic force-resisting system using tributary area rules. Two-dimensional analysis is
permitted where diaphragms are flexible.
311.6.14.8.3.2 STRUCTURES WITH DIAPHRAGMS THAT ARE NOT FLEXIBLE
For structures with diaphragms that are not flexible, as defined in Section
311.6.14.5, the seismic design story shear, Vx (kN), shall be distributed to the various
vertical elements of the seismic force-resisting system in the story under
consideration based on the relative lateral stiffnesses of the vertical elements and
the diaphragm.
311.6.14.8.3.2.1 TORSION
The design of structures with diaphragms that are not flexible shall include the
torsional moment, Mt (KN-m) resulting from eccentricity between the locations
of center of mass and the center of rigidity.
311.6.14.8.4 OVERTURNING
The structure shall be designed to resist overturning effects caused by the seismic forces
determined in Section 311.6.14.8.2. The foundations of structures shall be designed for
not less than 75 percent of the foundation overturning design moment, Mf (kN-m) at the
foundation–soil interface.
311.7 MATERIAL SPECIFIC SEISMIC DESIGN AND DETAILING REQUIREMENTS
311.7.1 SCOPE
Structural elements including foundation elements shall conform to the material design and
detailing requirements set forth in this chapter.
311.7.2 STEEL
Structures, including foundations, constructed of steel to resist seismic loads shall be designed
and detailed in accordance with this standard including the reference documents and additional
requirements provided in this section.
All rights reserved
169 / 496
311.7.2.1 SEISMIC REQUIREMENTS FOR STRUCTURAL STEEL STRUCTURES
The design of structural steel structures to resist seismic forces shall be in accordance with
the provisions of Section 311.7.2.1.1 or 311.7.2.1.1, as applicable.
311.7.2.1.1 SEISMIC DESIGN CATEGORIES B AND C
Structural steel structures assigned to Seismic Design Category B or C shall be of any
construction permitted by the applicable reference documents. Where a response
modification coefficient, R, in accordance with Table 311.6.2.3.2-1 is used for the design
of structural steel structures assigned to Seismic Design Category B or C, the structures
shall be designed and detailed in accordance with the requirements of AISC 341.
EXCEPTION: The response modification coefficient, R, designated for “Steel systems not
specifically detailed for seismic resistance, excluding cantilever column systems” in Table
311.6.2.3.2-1 shall be permitted for systems designed and detailed in accordance with
AISC 360 and need not be designed and detailed in accordance with AISC 341.
311.7.2.1.2 SEISMIC DESIGN CATEGORIES D THROUGH F
Structural steel structures assigned to Seismic Design Category D, E, or F shall be
designed and detailed in accordance with AISC 341.
311.8 SOIL STRUCTURE INTERACTION FOR SEISMIC DESIGN
311.8.1 GENERAL
If the option to incorporate the effects of soil–structure interaction is exercised, the
requirements of this section are permitted to be used in the determination of the design
earthquake forces and the corresponding displacements of the structure if the model used for
structural response analysis does not directly incorporate the effects of foundation flexibility
(i.e., the model corresponds to a fixed-based condition with no foundation springs). The
provisions in this section shall not be used if a flexible-base foundation is included in the
structural response model. The provisions for use with the equivalent lateral force procedure are
given in Section 311.8.2, and those for use with the modal analysis procedure are given in
Section 311.8.3.
311.8.2 EQUIVALENT LATERAL FORCE PROCEDURE
The following requirements are supplementary to those presented in Section 311.6.8.
311.8.2.1 BASE SHEAR
To account for the effects of soil–structure interaction, the base shear (V) determined from
Equation 311.6.8.1-1 shall be reduced to
= V – ΔV
EQUATION 311.8.2.1-1
The reduction (ΔV) shall be computed as follows and shall not exceed 0.3V:
Δ
- s (
)
≤ 0.3
EQUATION 311.8.2.1-2
where
Cs = the seismic design coefficient computed from Equations 311.6.8.1.1-1, 311.6.8.1.1-2,
and through 311.6.8.1.1-3 using the fundamental natural period of the fixed-base structure
(T or Ta) as specified in Section 311.6.8.2
= the value of Cs computed from Equations 311.6.8.1.1-1, 311.6.8.1.1-2, and through
311.6.8.1.1-3 using the fundamental natural period of the flexibly supported structure (T)
defined in Section 311.8.2.1.1
All rights reserved
170 / 496
β = the fraction of critical damping for the structure foundation system determined in
Section 311.8.2.1.2
= the effective seismic weight of the structure, which shall be taken as 0.7W, except for
structures where the effective seismic weight is concentrated at a single level, it shall be
taken as equal to W
311.8.2.1.1 EFFECTIVE BUILDING PERIOD
The effective period (T) shall be determined as follows:
̅
T=T√
(
̅
)
EQUATION 311.8.2.1.1-1
where
T = the fundamental period of the structure as determined in Section 311.6.8.2
= the stiffness of the structure where fixed at the base, defi ned by the following:
=
(
̅
)
EQUATION 311.8.2.1.1-2
where
= the effective height of the structure, which shall be taken as 0.7 times the structural
height (hn), except for structures where the gravity load is effectively concentrated at a
single level, the effective height of the structure shall be taken as the height to that level
Ky = the lateral stiffness of the foundation defined as the horizontal force at the level of
the foundation necessary to produce a unit deflection at that level, the force and the
deflection being measured in the direction in which the structure is analyzed
Kθ = the rocking stiffness of the foundation defined as the moment necessary to produce
a unit average rotation of the foundation, the moment and rotation being measured in
the direction in which the structure is analyzed
g = the acceleration of gravity
The foundation stiffnesses (Ky and Kθ) shall be computed by established principles of
foundation mechanics using soil properties that are compatible with the soil strain levels
associated with the design earthquake motion. The average shear modulus (G) for the
soils beneath the foundation at large strain levels and the associated shear wave velocity
(vs) needed in these computations shall be determined from Table 311.8.2.1.2-1 where
vso = the average shear wave velocity for the soils beneath the foundation at small strain
levels (10–3 percent or less)
Go = v2so/g = the average shear modulus for the soils beneath the foundation at small
strain levels
= the average unit weight of the soils
Alternatively, for structures supported on mat foundations that rest at or near the
ground surface or are embedded in such a way that the side wall contact with the soil is
not considered to remain effective during the design ground motion, the effective
period of the structure is permitted to be
determined from
All rights reserved
171 / 496
T=
√
̅
(
̅
)
EQUATION 311.8.2.1.1-3
where
= the relative weight density of the structure and the soil defined by
EQUATION 311.8.2.1.1-4
ra and rm = characteristic foundation lengths defined by
ra =√
EQUATION 311.8.2.1.1-5
and
rm = √
EQUATION 311.8.2.1.1-6
where
Ao = the area of the load-carrying foundation
Io = the static moment of inertia of the load-carrying foundation about a horizontal
centroidal axis normal to the direction in which the structure is analyzed
= dynamic foundation stiffness modifier for rocking as determined from Table
311.8.2.1.2-2
vs = shear wave velocity
T = fundamental period as determined in Section 311.6.8.2
311.8.2.1.2 EFFECTIVE DAMPING
The effective damping factor for the structure foundation system (β) shall be computed
as follows:
β=β o(0.05/( T/ T)3)
EQUATION 311.8.2.1.2-1
where
βo = the foundation damping factor as specified in Figure 311.8.2.1.2-1
For values of SDS/2.5 between 0.10 and 0.20 the values of βo shall be determined by
linear interpolation between the solid lines and the dashed lines of Figure 311.8.2.1.2-1
The quantity r in Figure 311.8.2.1.2-1is a characteristic foundation length that shall be
determined as follows:
For
/L0 ≤0.5, r = ra
EQUATION 311.8.2.1.2-2
For
/L0 ≥1, r = rm
where
EQUATION 311.8.2.1.2-3
Lo = the overall length of the side of the foundation in the direction being analyzed
All rights reserved
172 / 496
ra and rm = characteristic foundation lengths defined in Equations 311.8.2.1.1-5 and
311.8.2.1.1-6, respectively
For intermediate values of /L0, the value of r shall be determined by linear
interpolation.
EXCEPTION: For structures supported on point bearing piles and in all other cases where
the foundation soil consists of a soft stratum of reasonably uniform properties underlain
by a much stiffer, rock-like deposit with an abrupt increase in stiffness, the factor βo in
Equation 311.8.2.1.2-1 shall be replaced by β´o if (4Ds/vs T) < 1 where Ds is the total
depth of the stratum. βo shall be determined as follows:
β´o = (4Ds/vs T)2 βo
EQUATION 311.8.2.1.2-4
The value of β computed from Equation 311.8.2.1.2-1, both with or without the
adjustment represented by Equation 311.8.2.1.2-4, shall in no case be taken as less than
β = 0.05 or greater than β = 0.20.
Table 311.8.2.1.2-1 Values of G/Go and vs/vso
Site Class
A
B
C
D
E
F
Value of vs/vso
SDS/2.5
0.4
1.00
0.97
0.87
0.71
0.22
a
≤0.1
1.00
1.00
0.97
0.95
0.77
a
≥0.8
1.00
0.95
0.77
0.32
a
a
≤0.1
1.00
1.00
0.95
0.90
0.60
a
Value of G/Go
SDS/2.5
0.4
1.00
0.95
0.75
0.50
0.05
a
≥0.8
1.00
0.90
0.60
0.10
a
a
Note: Use straight-line interpolation for intermediate values of SDS/2.5.
a Should be evaluated from site specific analysis
Table 311.8.2.1.2-2 Values of αθ
All rights reserved
rm/vsT
aθ
< 0.05
0.15
0.35
0.5
1.0
0.85
0.7
0.6
173 / 496
FIGURE 311.8.2.1.2-1 Foundation Damping Factor
311.8.2.2 VERTICAL DISTRIBUTION OF SEISMIC FORCES
The distribution over the height of the structure of the reduced total seismic force ( ) shall
be considered to be the same as for the structure without interaction.
311.8.2.3 OTHER EFFECTS
The modified story shears, overturning moments, and torsional effects about a vertical axis
shall be determined as for structures without interaction using the reduced lateral forces.
The modified deflections (δ ) shall be determined as follows:
δx=
EQUATION 311.8.2.3-1
where
Mo = the overturning moment at the base using the unmodified seismic forces and not
including the reduction permitted in the design of the foundation
hx = the height above the base to the level under consideration
δx = the deflections of the fixed-base structure as determined in Section 311.6.8.6 using the
unmodified seismic forces The modified story drifts and P-delta effects shall be evaluated in
accordance with the provisions of Sections 311.6.8.6 and 311.6.8.7 using the modified story
shears and deflections determined in this section.
311.8.3 MODAL ANALYSIS PROCEDURE
The following provisions are supplementary to those presented in Section 311.6.9.
311.8.3.1 MODAL BASE SHEARS
To account for the effects of soil–structure interaction, the base shear corresponding to the
fundamental mode of vibration (V1) shall be reduced to
1 = V1 – ΔV1
All rights reserved
EQUATION 311.8.3.1-1
174 / 496
The reduction (ΔV1) shall be computed in accordance with Equation 311.8.2.1-2 with
taken as equal to the effective seismic weight of the fundamental period of vibration, ,
and Cs computed in accordance with Equation 311.6.8.1-1, except that SDS shall be replaced
by design spectral response acceleration of the design response spectra at the fundamental
period of the fixed-base structure (T1). The period T shall be determined from Equation
311.8.2.1.1-1 or from Equation 311.8.2.1.1-3 where applicable, taking T = T1, evaluating
from Equation 311.8.2.1.1-2 with
̅
=
1, and computing
∑
as follows:
EQUATION 311.8.3.1-2
∑
where
wi = the portion of the total gravity load of the structure at Level i
th
Φi1 = the displacement amplitude at the i
fundamental mode
hi = the height above the base to Level i
level of the structure when vibrating in its
The preceding designated values of , , T, and Talso shall be used to evaluate the factor a
from
Equation 311.8.2.1.1-4 and the factor βo from Figure 311.8.2.1.2-1. No reduction shall be
made in the shear components contributed by the higher modes of vibration. The reduced
base shear ( 1) shall in no case be taken less than 0.7V1.
311.8.3.2 OTHER MODAL EFFECTS
The modified modal seismic forces, story shears, and overturning moments shall be
determined as for structures without interaction using the modified base shear ( 1) instead
of V1. The modified modal deflections (δ xm) shall be determined as follows:
δ x1 =
EQUATION 311.8.3.2-1
and
δxm = δxm for m = 2, 3, ……….
EQUATION 311.8.3.2-2
where
Mo1 = the overturning base moment for the fundamental mode of the fixed-base structure
using the unmodified modal base shear V1
δxm = the modal deflections at Level x of the fixed base structure using the unmodified
modal shears, Vm
The modified modal drift in a story (Δ m) shall be computed as the difference of the
deflections (δxm) at the top and bottom of the story under consideration.
311.8.3.3 DESIGN VALUES
The design values of the modified shears, moments, deflections, and story drifts shall be
determined as for structures without interaction by taking the square root of the sum of the
squares (SRSS) of the respective modal contributions. In the design of the foundation, it is
permitted to reduce the overturning moment at the foundation–soil interface determined in
this manner by 10 percent as for structures without interaction. The effects of torsion about
All rights reserved
175 / 496
a vertical axis shall be evaluated in accordance with the provisions of Section 311.6.8.4, and
the P-delta effects shall be evaluated in accordance with the provisions of Section 311.6.8.7
using the story shears and drifts determined in Section 311.8.3.2.
311.9 SITE CLASSIFICATION PROCEDURE FOR SEISMIC DESIGN
311.9.1 SITE CLASSIFICATION
The site soil shall be classified in accordance with Table 311.9.4.3-1 and Section 311.9.3 based
on the upper 30 m of the site profile. Where site-specific data are not available to a depth of 30
m, appropriate soil properties are permitted to be estimated by the registered design
professional preparing the soil investigation report based on known geologic conditions. Where
the soil properties are not known in sufficient detail to determine the site class, Site Class D shall
be used unless the authority having jurisdiction or geotechnical data determine Site Class E or F
soils are present at the site. Site Classes A and B shall not be assigned to a site if there is more
than 10 m of soil between the rock surface and the bottom of the spread footing or mat
foundation.
311.9.2 SITE RESPONSE ANALYSIS FOR SITE CLASS SOIL
A site response analysis shall be provided for Site Class F soils, unless the exception to Section
311.9.3.1 is applicable.
311.9.3 SITE CLASS DEFINITION
Site class types shall be assigned in accordance with the definitions provided in Table 311.9.4.3-1
and this section.
311.9.3.1 SITE CLASS F
Where any of the following conditions is satisfied, the site shall be classified as Site Class F
and a site response analysis shall be performed.
1. Soils vulnerable to potential failure or collapse under seismic loading, such as liquefiable
soils, quick and highly sensitive clays, and collapsible weakly cemented soils.
EXCEPTION: For structures having fundamental periods of vibration equal to or less than
0.5 s, site response analysis is not required to determine spectral accelerations for
liquefiable soils. Rather, a site class is permitted to be determined in accordance with
Section 20.3 and the corresponding values of Fa and Fv determined from Tables 311.4.3-2
and 311.4.3-3.
2. Peats and/or highly organic clays [H > 3 m] of peat and/or highly organic clay where H =
thickness of soil.
3. Very high plasticity clays [H > 7.6 m with PI > 75].
4. Very thick soft/medium stiff clays [H > 37 m] with su < 50 kPa.
311.9.3.2 SOFT CLAY SITE CLASS E
Where a site does not qualify under the criteria for Site Class F and there is a total thickness
of soft clay greater than 3 m where a soft clay layer is defined by su < 25 kPa, w ≥ 40 percent,
and PI > 20, it shall be classified as Site Class E.
311.9.3.3 SITE CLASSES C, D, AND E
The existence of Site Class C, D, and E soils shall be classified by using one of the following
three methods with s, , and u computed in all cases as specified in Section 311.9.4:
1. s for the top 30 m ( s method).
2. for the top 30 m ( method).
3. ch for cohesionless soil layers (PI < 20) in the top 30 m and u for cohesive soil layers (PI >
20) in the top 30 m ( u method).
All rights reserved
176 / 496
Where the ch and u criteria differ, the site shall be assigned to the category with the softer
soil.
311.9.3.4 SHEAR WAVE VELOCITY SITE CLASS B
The shear wave velocity for rock, Site Class B, shall be either measured on site or estimated
by a geotechnical engineer, engineering geologist, or seismologist for competent rock with
moderate fracturing and weathering. Softer and more highly fractured and weathered rock
shall either be measured on site for shear wave velocity or classified as Site Class C.
311.9.3.5 SHEAR WAVE VELOCITY FOR SITE CLASS A
The hard rock, Site Class A, category shall be supported by shear wave velocity
measurement either on site or on profiles of the same rock type in the same formation with
an equal or greater degree of weathering and fracturing. Where hard rock conditions are
known to be continuous to a depth of 30 m, surficial shear wave velocity measurements are
permitted to be extrapolated to assess s.
311.9.4 DEFINITIONS OF SITE CLASS PARAMETERS
The definitions presented in this section shall apply to the upper 30 m of the site profile. Profiles
containing distinct soil and rock layers shall be subdivided into those layers designated by a
number that ranges from 1 to n at the bottom where there are a total of n distinct layers in the
upper 30 m. Where some of the n layers are cohesive and others are not, k is the number of
cohesive layers and m is the number of cohesionless layers. The symbol i refers to any one of the
layers between 1 and n.
311.9.4.1 s, AVERAGE SHEAR WAVE VELOCITY
s shall be determined in accordance with the following formula:
s=
∑
EQUATION 311.9.4.1-1
∑
where
di = the thickness of any layer between 0 and 30 m
vsi = the shear wave velocity in m/s
∑
( )
311.9.4.2 , AVERAGE FIELD STANDARD PENETRATION RESISTANCE AND
STANDARD PENETRATION RESISTANCE FOR COHESIONAL SOIL LAYERS
and ch shall be determined in accordance with the following formulas:
=
∑
ch, AVERAGE
EQUATION 311.9.4.2-1
∑
where Ni and di in Equation 311.9.4.2-1 are for cohesionless soil, cohesive soil, and rock
layers.
ch =
All rights reserved
∑
EQUATION 311.9.4.2-2
177 / 496
where Ni and di in Equation 311.9.4.2-2 are for cohesionless soil layers only and ∑
where ds is the total thickness of cohesionless soil layers in the top 30 m. Ni is the
standard penetration resistance (ASTM D1586) not to exceed 305 blows/m as directly
measured in the field without corrections. Where refusal is met for a rock layer, Ni shall be
taken as 305 blows/m.
311.9.4.3 u, AVERAGE UNDRAINED SHEAR STRENGTH
u shall be determined in accordance with the following formula:
u=
∑
EQUATION 311.9.4.3-1
where
∑
dc = the total thickness of cohesive soil layers in the top 30 m
PI = the plasticity index as determined in accordance with ASTM D4318
w = the moisture content in percent as determined in accordance with ASTM D2216
sui = the undrained shear strength in psf (kPa), not to exceed 240 kPa as determined in
accordance with ASTM D2166 or ASTM D2850
Table 311.9.4.3-1 Site Classification
Site Class
A. Hard rock
B. Rock
C. Very dense soil and soft rock
D. Stiff soil
E. Soft clay soil
F. Soils requiring site response analysis
or ch
s
u
>1,500 m/s
NA
NA
760 to 5,000 m/s
NA
NA
365 to 760 m/s
>50
> 100 kPa
180 to 365 m/s
15 to 50
50 to 100 kPa
<180 m/s
<15
<50 kPa
Any profile with more than 3 m of soil having the following characteristics:
—Plasticity index PI > 20,
—Moisture content w ≥ 40%,
—Undrained shear strength u < 25 kPa
See Section 311.9.3.1
312. SOIL LATERAL LOADS
312.1 GENERAL
Foundation walls and retaining walls shall be designed to resist lateral soil loads. Soil loads
specified in Table 312.1-1 shall be used as the minimum design lateral soil loads unless
determined otherwise by a geotechnical investigation in accordance with Section 1803.
Foundation walls and other walls in which horizontal movement is restricted at the top shall be
designed for at-rest pressure. Retaining walls free to move and rotate at the top shall be
permitted to be designed for active pressure. Design lateral pressure from surcharge loads shall be
added to the lateral earth pressure load. Design lateral pressure shall be increased if soils at the
site are expansive. Foundation walls shall be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed in accordance with
Sections 404.4.2 and 404.4.3.
Exception: Foundation walls extending not more than 2400 mm below grade and laterally
supported by the top by flexible diaphragms shall be permitted to be designed for active pressure.
All rights reserved
178 / 496
TABLE 312.1-1 LATERAL SOIL LOAD
a
c
DESCRIPTION OF BACKFILL MATERIAL
Well-graded, clean gravels; gravel-sand mixes
Poorly graded clean gravels; gravel-sand mixes
Silty gravels, poorly graded gravel-sand mixes
Clayey gravels, poorly graded gravel-and-clay mixes
Well-graded, clean sands; gravelly sand mixes
Poorly graded clean sands; sand-gravel mixes
Silty sands, poorly graded sand-silt mixes
Sand-silt clay mix with plastic fines
Clayey sands, poorly graded sand-clay mixes
Inorganic silts and clayey silts
Mixture of inorganic silt and clay
Inorganic clays of low to medium plasticity
Organic silts and silt clays, low plasticity
Inorganic clayey silts, elastic silts
Inorganic clays of high plasticity
Organic clays and silty clays
UNIFIED SOIL
CLASSIFICATION
GW
GP
GM
GC
SW
SP
SM
SM-SC
SC
ML
ML-CL
CL
OL
MH
CH
OH
DESIGN LATERAL SOIL LOAD
(kPa per meter of depth)
Active pressure At-rest pressure
4.70
9.40
4.70
9.40
6.30
9.40
7.00
9.40
4.70
9.40
4.70
9.40
7.00
9.40
7.00
15.70
9.40
15.70
7.00
15.70
9.40
15.70
9.40
15.70
Note b
Note b
Note b
Note b
Note b
Note b
Note b
Note b
a. Design lateral soil loads are given for moist conditions for the specified soils at their optimum
densities. Actual field conditions shall govern. Submerged or saturated soil pressures shall include
the weight of the buoyant soil plus the hydrostatic loads.
b. Unsuitable as backfill material.
c. The definition and classification of soil materials shall be in accordance with ASTM D 2487.
All rights reserved
179 / 496
CHAPTER 4
SOILS AND FOUNDATIONS
SECTION 401 GENERAL
GENERAL
401.1 SCOPE
The provisions of this chapter shall apply to building and foundation systems.
401.2 DESIGN BASIS
Allowable bearing pressures, allowable stresses and design formulas provided in this chapter shall be
used with the allowable stress design load combinations specified in Section 302.4. The quality and
design of materials used structurally in excavations and foundations shall comply with the
requirements specified in section 520 of this code.
SECTION 402 GEOTECHNICAL INVESTIGATIONS
402.1 GENERAL
Geotechnical investigations shall be conducted in accordance with Section 402.2 and reported in
accordance with Section 402.5 . Where required by the building official or where geotechnical
investigations involve in-situ testing, laboratory testing or engineering calculations, such investigations
shall be conducted by a registered design professional.
402.2 INVESTIGATIONS REQUIRED
Geotechnical investigations shall be conducted in accordance with Sections 402.3 through 402.4.
Exception: The building official shall be permitted to waive the requirement for a geotechnical
investigation where satisfactory data from adjacent areas is available that demonstrates an
investigation is not necessary for any of the conditions in Sections 402.4.1 through 402.4.6 and and
402.4.10.
402.3 BASIS OF INVESTIGATION
Soil classification shall be based on observation and any necessary tests of the materials disclosed by
borings, test pits or other subsurface exploration made in appropriate locations. Additional studies
shall be made as necessary to evaluate slope stability, soil strength, position and adequacy of loadbearing soils, the effect of moisture variation on soil-bearing capacity, compressibility, liquefaction and
expansiveness.
402.3.1 SCOPE OF INVESTIGATION
The scope of the geotechnical investigation including the number and types of borings or
soundings, the equipment used to drill or sample, the in-situ testing equipment and the
laboratory testing program shall be determined by a registered design professional.
402.4 INVESTIGATED CONDITIONS
Geotechnical investigations shall be conducted as indicated in Sections 402.5.1 through 402.5.12.
402.4.1 CLASSIFICATION
Soil materials shall be classified in accordance with ASTM D 2487.
402.4.2 QUESTIONABLE SOIL
Where the classification, strength or compressibility of the soil is in doubt or where a loadbearing value superior to that specified in this code is claimed, the building official shall be
permitted to require that a geotechnical investigation be conducted.
All rights reserved
180 / 496
402.4.3 EXPANSIVE SOIL
In areas likely to have expansive soil, the building official shall require soil tests to determine
where such soils do exist.
Soils meeting all four of the following provisions shall be considered expansive, except that tests to
show compliance with Items 1, 2 and 3 shall not be required if the test pre- scribed in Item 4 is
conducted:
1. Plasticity index (PI) of 15 or greater, determined in accordance with ASTM D 4318.
2. More than 10 percent of the soil particles pass a No. 200 sieve (75µm), determined in
accordance with ASTM D 422.
3. More than 10 percent of the soil particles are less than 5 micrometers in size, determined in
accordance with ASTM D 422.
4. Expansion index greater than 20, determined in accordance with ASTM D 4829.
402.4.4 GROUND-WATER TABLE
A subsurface soil investigation shall be performed to determine whether the existing groundwater table is above or within 1500 mm below the elevation of the lowest floor level where such
floor is located below the finished ground level adjacent to the foundation.
Exception: A subsurface soil investigation to determine the location of the ground-water table
shall not be required where waterproofing is provided in accordance with Section 404.
402.4.5 DEEP FOUNDATIONS
Where deep foundations will be used, a geotechnical investigation shall be conducted and shall
include all of the following, unless sufficient data upon which to base the design and installation is
otherwise available:
1. Recommended deep foundation types and installed capacities.
2. Recommended center-to-center spacing of deep foundation elements.
3. Driving criteria.
4. Installation procedures.
5. Field inspection and reporting procedures (to include procedures for verification of the
installed bearing capacity where required).
6. Load test requirements.
7. Suitability of deep foundation materials for the intended environment.
8. Designation of bearing stratum or strata.
9. Reductions for group action, where necessary.
402.4.6 ROCK STARTA
Where subsurface explorations at the project site indicate variations or doubtful characteristics in
the structure of the rock upon which foundations are to be constructed, a sufficient number of
borings shall be made to a depth of not less than 3000 mm below the level of the foundations to
provide assurance of the soundness of the foundation bed and its load-bearing capacity.
402.4.7 EXCAVATION NEAR FOUNDATIONS
Where excavation will remove lateral support from any foundation, an investigation shall be
conducted to assess the potential conse- quences and address mitigation measures.
402.4.8 COMPACTED FILL MATERIAL
Where shallow foundations will bear on compacted fill material more than 300 mm in depth, a
geotechnical investigation shall be conducted and shall include all of the following:
1. Specifications for the preparation of the site prior to placement of compacted fill material.
2. Specifications for material to be used as compacted fill.
3. Test methods to be used to determine the maximum dry density and optimum moisture
content of the material to be used as compacted fill.
4. Maximum allowable thickness of each lift of compacted fill material.
All rights reserved
181 / 496
5. Field test method for determining the in-place dry density of the compacted fill.
6. Minimum acceptable in-place dry density expressed as a percentage of the maximum dry
density determined in accordance with Item 3.
7. Number and frequency of field tests required to determine compliance with Item 6.
402.4.9 CONTROLLED LOW-STRENGTH MATERIAL (CLSM).
Where shallow foundations will bear on controlled
low-strength material (CLSM), a geotechnical investigation shall be conducted and shall include
all of the following:
1. Specifications for the preparation of the site prior to placement of the CLSM.
2. Specifications for the CLSM.
3. Laboratory or field test method(s) to be used to determine the compressive strength or
bearing capacity of the CLSM.
4. Test methods for determining the acceptance of the CLSM in the field.
5. Number and frequency of field tests required to determine compliance with Item 4.
402.4.10 SEISMIC DESIGN CATEGORIES C THROUGH F
For structures assigned to Seismic Design Category C, D, E or F in accordance with Section 311, a
geotechnical investiga- tion shall be conducted, and shall include an evaluation of all of the
following potential geologic and seismic hazards:
1. Slope instability.
2. Liquefaction.
3. Differential settlement.
4. Surface displacement due to faulting or lateral spreading.
402.4.11 SEISMIC DESIGN CATEGORIES D THROUGH F
For structures assigned to Seismic Design Category D, E or F in accordance with Section 310, the
geotechnical investigation shall also include:
1. The determination of lateral pressures on foundation walls and retaining walls due to
earthquake motions.
2. The potential for liquefaction and soil strength loss evaluated for site peak ground
accelerations, magnitudes and source characteristics consistent with the design earthquake
ground motions. Peak ground acceleration shall be permitted to be determined based on a
site-specific study taking into account soil amplification effects in the absence of such a study,
peak ground accelerations shall be assumed equal to SDS/2.5, where SDS is determined in
accordance with Section 311.4.4.
3. An assessment of potential consequences of liquefaction and soil strength loss, including
estimation of differential settlement, lateral movement, lateral loads on foundations,
reduction in foundation soil-bearing capacity, increases in lateral pressures on retaining walls
and flotation of buried structures.
4. Discussion of mitigation measures such as, but not limited to, ground stabilization, selection of
appropriate foundation type and depths, selection of appropriate structural systems to
accommodate anticipated displacements and forces, or any combination of these measures
and how they shall be considered in the design of the structure.
402.5 REPORTING
Where geotechnical investigations are required, a written report of the investigations shall be submitted to the building official by the owner or authorized agent at the time of permit application. This
geotechnical report shall include, but need not be limited to, the following information:
1. A plot showing the location of the soil investigations.
2. A complete record of the soil boring and penetration test logs and soil samples.
3. A record of the soil profile.
4. Elevation of the water table, if encountered.
All rights reserved
182 / 496
5. Recommendations for foundation type and design criteria, including but not limited to: bearing
capacity of natural or compacted soil; provisions to mitigate the effects of expansive soils;
mitigation of the effects of liquefaction, differential settlement and varying soil strength; and the
effects of adjacent loads.
6. Expected total and differential settlement.
7. Deep foundation information in accordance with Section 402.4.5.
8. Special design and construction provisions for foundations of structures founded on expansive soils,
as necessary.
9. Compacted fill material properties and testing in accordance with Section 402.4.8.
10. Controlled low-strength material properties and testing in accordance with Section 402.4.9.
SECTION 403 EXCAVATION, GRADING AND FILL
403.1 EXCAVATION NEAR FOUNDATIONS
Excavation for any purpose shall not remove lateral support from any foundation without first
underpinning or protecting the foundation against settlement or lateral translation.
403.2 PLACEMENT OF BACKFILL
The excavation outside the foundation shall be backfilled with soil that is free of organic material,
construction debris, cobbles and boulders or with a controlled low-strength material (CLSM). The
backfill shall be placed in lifts and compacted in a manner that does not damage the foundation or
thewaterproofing or dampproofing material.
Exception: CLSM need not be compacted.
403.3 SITE GRADING
The ground immediately adjacent to the foundation shall be sloped away from the building at a slope of
not less than one unit vertical in 20 units horizontal (5-percent slope) for a minimum distance of 3000
mm measured perpendicular to the face of the wall. If physical obstructions or lot lines prohibit 3000
mm of horizontal distance, a 5-percent slope shall be provided to an approved alternative method of
diverting water away from the foundation. Swales used for this purpose shall be sloped a minimum of
2 percent where located within 3000 mm) of the building foundation.
Impervious surfaces within 3000 mm of the building foundation shall be sloped a minimum of 2
percent away from the building.
Exception: Where climatic or soil conditions warrant, the slope of the ground away from the
building foundation shall be permitted to be reduced to not less than one unit vertical in 48 units
horizontal (2-percent slope). The procedure used to establish the final ground level adjacent to
the foundation shall account for additional settlement of the backfill.
403.4 COMPACTED FILL MATERIAL
Where shallow foundations will bear on compacted fill material, the compacted fill shall comply with
the provisions of an approved geotechnical report, as set forth in Section 402.
Exception: Compacted fill material 300 mm in depth or less need not comply with an approved
report, provided the in-place dry density is not less than 90 percent of the maximum dry density
at optimum moisture content determined in accordance with ASTM D 1557. The compaction
shall be verified by special inspection in accordance with Section 903.7.
403.5 CONTROLLED LOW-STRENGTH MATERIAL (CLSM).
Where shallowfoundations will bear on controlled low-strength material (CLSM), the CLSM shall
comply with the provisions of an approved geotechnical report, as set forth in Section 402.
All rights reserved
183 / 496
SECTION 404 DAMPPROOFING AND WATERPROOFING
404.1 GENERAL
Walls or portions thereof that retain earth and enclose interior spaces and floors below grade shall be
water-proofed and dampproofed in accordance with this section, with the exception of those spaces
containing groups other than residential and institutional where such omission is not detrimental to the
building or occupancy.
404.1.1 STORY ABOVE GRADE PLANE
Where a basement is considered a story above grade plane and the finished ground level
adjacent to the basement wall is below the basement floor elevation for 25 percent or more of
the perimeter, the floor and walls shall be dampproofed in accordance with Section 404.2 and a
foundation drain shall be installed in accordance with Section 404.4.2. The foundation drain shall
be installed around the portion of the perimeter where the basement floor is below ground level.
The provisions of Sections 402.4.4, 404.3 and 404.4.1 shall not apply in this case.
404.1.2. UNDER-FLOOR SPACE.
The finished ground level of an under-floor space such as a crawl space shall not be located
belowthe bottom of the footings. Where there is evidence that the ground-water table rises to
within 150 mm of the ground level at the outside building perimeter, or that the surface water
does not readily drain from the building site, the ground level of the under-floor space shall be
as high as the outside finished ground level, unless an approved drainage system is provided.
The provisions of Sections 402.4.4, 404.2, 404.3 and 404.4 shall not apply in this case.
404.1.3 GROUND-WATER CONTROL
Where the ground-water table is lowered and maintained at an elevation not less than 150mm
below the bottom of the lowest floor, the floor and walls shall be dampproofed in accordance
with Section 404.2. The design of the system to lower the ground-water table shall be based on
accepted principles of engineering that shall consider, but not necessarily be limited to,
permeability of the soil, rate at which water enters the drainage system, rated capacity of
pumps, head against which pumps are to operate and the rated capacity of the disposal area of
the system.
404.2 DAMPPROOFING
Where hydrostatic pressure will not occur as determined by Section 402.4.4, floors and walls for
systems shall be dampproofed in accordance with this section.
404.3 WATERPROOFING
Where the ground-water investigation required by Section 402.4.4 indicates that a hydrostatic pressure
condition exists, and the design does not include a ground-water control system as described in
Section 404.1.3, walls and floors shall be waterproofed in accordance with this section.
404.3.1 FLOORS
Floors required to be waterproofed shall be of concrete and designed and constructed to
withstand the hydrostatic pressures to which the floors will be subjected.
404.3.2 WALLS
Walls required to be waterproofed shall be of concrete or masonry and shall be designed and
constructed to withstand the hydrostatic pressures and other lat- eral loads to which the walls will
be subjected.
All rights reserved
184 / 496
404.3.2.1 SURFACE PREPARATION OF WALLS
Prior to the application of waterproofing materials on concrete or masonry walls, the walls
shall be prepared in accordance with Section 404.2.
404.4 SUBSOIL DRAINAGE SYSTEM
Where a hydrostatic pressure condition does not exist, dampproofing shall be provided and a base shall
be installed under the floor and a drain installed around the foundation perimeter.
404.4.1 FLOOR BASE COURSE
Floors of basements, except as provided for in Section 1805.1.1, shall be placed over a floor base
course not less than 100 mm in thickness that consists of gravel or crushed stone containing not
more than 10 percent of material that passes through a No 4 (4.75 mm) sieve.
Exception: Where a site is located in well-drained gravel or sand/gravel mixture soils, a floor base
course is not required.
404.4.2 FOUNDATION DRAIN
A drain shall be placed around the perimeter of a foundation that consists of gravel or crushed
stone containing not more than 10-percent material that passes through a No 4 (4.75 mm) sieve.
The drain shall extend a minimum of 300 mm beyond the outside edge of the footing. The
thickness shall be such that the bottom of the drain is not higher than the bottom of the base
under the floor, and that the top of the drain is not less than 150mm above the top of the footing.
The top of the drain shall be covered with an approved filter membrane material. Where a drain
tile or perforated pipe is used, the invert of the pipe or tile shall not be higher than the floor
elevation. The top of joints or the top of perforations shall be protected with an approved filter
membrane material. The pipe or tile shall be placed on not less than 50 mm of gravel or
crushed stone complying with Section 404.4.1, and shall be covered with not less than 150
mm of the same material.
404.4.3 DRAINAGE DISCHARGE
The floor base and foundation perimeter drain shall discharge by gravity or mechanical means
into an approved drainage system that complies with the International Plumbing Code.
Exception: Where a site is located in well-drained gravel or sand/gravel mixture soils, a dedicated
drainage system is not required.
SECTION 405 PRESUMPTIVE LOAD-BEARING VALUES OF SOILS
405.1 LOAD COMBINATIONS
The presumptive load-bearing values provided in Table 405.3.4-1 shall be used with the allowable
stress design load combinations. The values of vertical foundation pressure and lateral bearing
pressure given in Table 405.3.4-1 shall be permitted to be increased by one-third where used with the
alternative basic load combinations of Section 302.4.3 that include wind or earthquake loads.
405.2 PRESUMPTIVE LOAD-BEARING VALUES
The load-bearing values used in design for supporting soils near the surface shall not exceed the values
specified in Table 1804.2 unless data to substantiate the use of higher values are submitted and
approved.
405.3 LATERAL LOAD RESISTANCE
Where the presumptive values of Table 405.3.4-1 are used to determine resistance to lateral loads, the
calculations shall be in accordance with Sections 405.3.1 through 405.3.4.
All rights reserved
185 / 496
405.3.1 COMBINED RESISTANCE
The total resistance to lateral loads shall be permitted to be determined by combining the values
derived from the lateral bearing pressure and the lateral sliding resistance specified in Table
405.3.4-1.
405.3.2 LATERAL SLIDING RESISTANCE LIMIT
For clay, sandy clay, silty clay, clayey silt, silt and sandy silt, in no case shall the lateral sliding
resistance exceed one-half the dead load.
405.3.3 INCREASE FOR DEPTH
The lateral bearing pressures specified in Table 1805.2 shall be permitted to be increased by the
tabular value for each additional 300 mm of depth to a maximum of 15 times the tabular value.
405.3.4 INCREASE FOR POLES
Isolated poles for uses such as flagpoles or signs and poles used to support buildings that are not
adversely affected by a 12.0 mm motion at the ground surface due to short-term lateral loads
shall be permitted to be designed using lateral bearing pressures equal to two times the tabular
values.
TABLE 405.3.4-1 PRESUMPTIVE LOAD-BEARING VALUES
CLASS OF MATERIALS
1. Crystalline bedrock
2. Sedimentary and foliated rock
3. Sandy gravel and/or
gravel (GW and GP)
4. Sand, silty sand, clayey sand, silty
gravel and clayey gravel (SW, SP, SM,
SC, GM and GC)
5. Clay, sandy clay, silty clay, clayey
silt, silt and sandy silt (CL, ML, MH
and CH)
VERTICAL
FOUNDATION
PRESSURE
(kPa)
575
192
LATERAL BEARING
PRESSURE
(kPa/m below
natural grade)
189
63
LATERAL SLIDING RESISTANCE
0.70
0.35
-
144
32
0.35
-
96
24
0.25
-
72
16
-
6.22
Coefficient of
a
friction
Cohesion
b
(kPa)
a. Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 405.3.2.
SECTION 406 FOUNDATION WALLS, RETAINING WALLS AND EMBEDDED POSTS AND POLES
406.1 FOUNDATION WALLS
Foundation walls shall be designed and constructed in accordance with Sections 406.1.1 through
406.1.4. Foundation walls shall be supported by foundations designed in accordance with Section 407.
406.1.1 DESIGN LATERAL SOIL LOADS
1807.1.1 Design lateral soil loads. Foundation walls shall be designed for the lateral soil loads
set forth in Section 312.
406.1.2 UNBALANCED BACKFILL HEIGHT
Unbalanced backfill height is the difference in height between the exterior finish ground level and
the lower of the top of the concrete footing that supports the foundation wall or the interior
finish ground level. Where an interior concrete slab on grade is provided and is in contact with
All rights reserved
186 / 496
the interior surface of the foundation wall, the unbalanced backfill height shall be permitted to be
measured from the exterior finish ground level to the top of the interior concrete slab.
406.1.3 RUBBLE STONE FOUNDATION WALLS
Foundation walls of rough or random rubble stone shall not be less than 400mm thick. Rubble
stone shall not be used for foundation walls of structures assigned to Seismic Design Category C,
D, E or F.
406.1.4 PRESCRIPTIVE DESIGN OF CONCRETE AND MASONRY FOUNDATION WALSS
Concrete and masonry foundation walls that are laterally supported at the top and bottom shall
be permitted to be designed and constructed in accordance with this section.
406.1.4.1 FOUNDATION WALL THICKNESS
The thickness of prescriptively designed foundation walls shall not be less than the thickness
of the wall supported.
406.1.4.2 CONCRETE FOUNDATION WALLS
Concrete foundation walls shall comply with the following:
1. The thickness shall comply with the requirements of Table 406.2.3-1.
2. The size and spacing of vertical reinforcement shown in Table 406.2.3-1 is based on the
use of reinforcement with a minimum yield strength of 420 MPa. Vertical reinforcement
with a minimum yield strength of 275 MPa or 345 MPa shall be permitted, provided the
same size bar is used and the spacing shown in the table is reduced by multiplying the
spacing by 0.67 or 0.83, respectively.
3. Vertical reinforcement, when required, shall be placed nearest the inside face of the wall
a distance, d, from the outside face (soil face) of the wall. The distance, d, is equal to the
wall thickness, t, minus 30 mm plus one-half the bar diameter, db, [ d = t – (1.25 + db / 2) ].
The reinforcement shall be placed within a tolerance of ± 10 mm where d is less than or
equal to 200 mm or ± 12.0 mm where d is greater than 200 mm.
4. In lieu of the reinforcement shown in Table 406.2.3-1, smaller reinforcing bar sizes
with closer spacings that provide an equivalent cross-sectional area of reinforcement
per unit length shall be permitted.
5. Concrete cover for reinforcement measured from the inside face of the wall shall not be
less than 20 mm. Concrete cover for reinforcement measured from the outside face of
the wall shall not be less than 40 mm for No. 5 bars and smaller, and not less than 50 mm
for larger bars.
6. Concrete shall have a specified compressive strength, f’c, of not less than 18.0 MPa.
7. The unfactored axial load in tons per linear meter of wall shall not exceed 1.2 t f’c where
t is the specified wall thickness in meters.
406.1.4.2.1 SEISMIC REQUIREMENTS
Based on the seismic design category assigned to the structure in accordance with
Section 311, concrete foundation walls designed using Table 406.2.3-1 shall be subject
to the following limitations:
1. Seismic Design Categories A and B. No additional seismic requirements, except
provide reinforcement around openings in accordance with Section 507.6.7.
2. Seismic Design Categories C, D, E and F. Tables shall not be used except as
allowed for plain concrete members.
406.1.4.3 MASONRY FOUNDATION WALLS
Masonry foundation walls shall comply with the following:
1. The thickness shall comply with the requirements of Table 406.2.3-2 for plain masonry
walls or Table 406.2.3-3, 406.2.3-4 or 406.2.3-5 for masonry walls with reinforcement.
All rights reserved
187 / 496
2. Vertical reinforcement shall have a minimum yield strength of 420 MPa.
3. The specified location of the reinforcement shall equal or exceed the effective depth
distance, d, noted in Tables 406.2.3-3, 406.2.3-4 and 406.2.3-5 and shall be measured
from the face of the exterior (soil) side of the wall to the center of the vertical
reinforcement.
4. Grout shall comply with Section 703.9.1.
5. Concrete masonry units shall comply with ASTM C 90.
6. Clay masonry units shall comply with ASTM C 652 for hollow brick, except compliance
with ASTM C 62 or ASTM C216 shall be permitted where solid masonry units are installed
in accordance with Table 406.2.3-2 for plain masonry.
7. Masonry units shall be laid in running bond and installed with Type M or S mortar in
accordance with Section 703.8.
8. The unfactored axial load in tons per linear meter of wall shall not exceed 1.2 t f’m where
t is the specified wall thickness in meters and f’m is the specified compressive strength
of masonry in MPa.
9. At least 100 mm of solid masonry shall be provided at girder supports at the top of hollow
masonry unit foundation walls.
10. Corbeling of masonry shall be in accordance with Section 704.2. Where an 200 mm wall
is corbeled, the top corbel shall not extend higher than the bottom of the floor framing
and shall be a full course of headers at least 150 mm in length or the top course bed joint
shall be tied to the vertical wall projection. The tie shall be 4.8 mm and spaced at a
maximum horizontal distance of 900 mm. The hollow space behind the corbelled
masonry shall be filled with mortar or grout.
406.1.4.3.1 SEISMIC REQUIREMENTS
Based on the seismic design category assigned to the structure in accordance with
Section 311, masonry foundation walls designed using Tables 406.2.3-2 through
406.2.3-5 shall be subject to the following limitations:
1. Seismic Design Categories A and B. No additional seismic requirements.
2. Seismic Design Category C. A design using Tables 406.2.3-2 through 406.2.3-5 is
subject to the seismic requirements of Section 1.17.4.3 of TMS 402/ACI 530/ASCE 5.
3. Seismic Design Category D. A design using Tables 406.2.3-3 through 406.2.3-5 is
subject to the seismic requirements of Section 1.17.4.4 of TMS 402/ACI 530/ASCE 5.
4. Seismic Design Categories E and F. A design usi n g T abl e s 406.2.3-3 t h rough
406.2.3-5 is subject to the seismic requirements of Section 1.17.4.5 of TMS
402/ACI 530/ASCE 5.
406.2 RETAINING WALLS
Retaining walls shall be designed in accordance with Sections 406.2.1 through 406.2.3.
406.2.1 GENERAL
Retaining walls shall be designed to ensure stability against overturning, sliding, excessive
foundation pressure and water uplift. Where a keyway is extended below the wall base with the
intent to engage passive pressure and enhance sliding stability, lateral soil pressures on both sides
of the keyway shall be considered in the sliding analysis.
406.2.2 DESIGN LATERAL SOIL LOADS
Retaining walls shall be designed for the lateral soil loads set forth in Section 312.
406.2.3 SAFETY FACTOR
Retaining walls shall be designed to resist the lateral action of soil to produce sliding and
overturning with a minimum safety factor of 1.5 in each case. The load combinations of Section
302 shall not apply to this requirement. Instead, design shall be based on 0.7 times nominal
All rights reserved
188 / 496
earthquake loads, 1.0 times other nominal loads, and investigation with one or more of the
variable loads set to zero. The safety factor against lateral sliding shall be taken as the available
soil resistance at the base of the retaining wall foundation divided by the net lateral force applied
to the retaining wall.
Exception: Where earthquake loads are included, the minimum safety factor for retaining
wall sliding and overturning shall be 1.1.
TABLE 406.2.3-1 CONCRETE FOUNDATION WALLS
MAXIM
UM
WALL
HEIGHT
(m)
1.50
1.80
2.15
MAXIMUM
UNBALANC
ED
BACKFILL
HEIGHTe
(m)
1.22
1.52
1.22
1.52
1.83
1.22
1.52
1.83
2.13
b, c
MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (mm)
Design lateral soil loada (kPa/m)
4.70d
7.00d
9.40
Minimum wall thickness (mm)
190
240
290
190
240
290
190
240
290
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
ϕ 12 at
1200
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
ϕ12 at
1200
ϕ16 at
1200
PC
PC
ϕ12 at
1000
ϕ16 at
1000
ϕ16 at
800
PC
PC
ϕ12 at
990
ϕ16 at
950
ϕ18 at
990
ϕ18 at
750
PC
PC
ϕ12 at
950
ϕ16 at
900
ϕ18 at
900
ϕ16 at
550
ϕ16 at
550
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
ϕ16 at
1100
PC
PC
PC
PC
PC
PC
PC
PC
ϕ12 at
930
ϕ16 at
990
ϕ18 at
1040
PC
PC
PC
PC
ϕ10 at
1200
ϕ16 at
990
PC
PC
PC
ϕ16 at
1200
ϕ18 at
1200
ϕ18 at
930
ϕ18 at
761
PC
PC
PC
PC
ϕ16 at
1140
ϕ18 at
1191
ϕ18 at
960
2.40
1.22
1.52
1.83
2.13
2.43
PC
PC
PC
PC
ϕ12 at 1200
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
ϕ 12 at
1000
ϕ 16 at
1100
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
2.75
1.22
1.52
1.83
2.13
2.43
2.74d
PC
PC
PC
PC
ϕ 12 at 1000
ϕ 16 at 1200
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
ϕ 12 at
930
ϕ 16 at
1000
ϕ18 at
1050
PC
PC
PC
PC
ϕ 12 at
1000
ϕ 16 at
1050
PC
PC
PC
PC
PC
PC
3.05
1.22
1.52
1.83
2.13
2.43
2.74d
3.05d
PC
PC
PC
PC
ϕ12 at 900
ϕ16 at 1000
ϕ18 at 1150
PC
PC
PC
PC
PC
ϕ10 at 1200
ϕ16 at 1150
PC
PC
PC
PC
PC
PC
PC
PC
PC
PC
ϕ16 at
1200
ϕ18 at
1200
ϕ18 at
1000
ϕ18 at
750
PC
PC
PC
PC
ϕ16 at
1200
ϕ18 at
1200
ϕ18 at
1000
PC
PC
PC
PC
PC
ϕ10 at
1200
ϕ16 at
950
a. For design lateral soil loads, see Section 312.
b. Provisions for this table are based on design and construction requirements specified in Section
406.1.4.2.
c. “ ” means plain concrete.
d. Where unbalanced backfill height exceeds 2.43 m and design lateral soil loads from Table 312.1-1 are
used, the requirements for 4.71 and 7.06 kPa/m of depth are not applicable (see Section 312).
e. For height of unbalanced backfill, see Section 406.1.2.
All rights reserved
189 / 496
TABLE 406.2.3-2 PLAIN MASONRY FOUNDATION WALLS
MAXIMUM WALL
HEIGHT
(m)
MAXIMUM
UNBALANCED
BACKFILL
HEIGHTe(m)
MINIMUM NOMINAL WALL THICKNESS (mm)
f
4.70
2.10
2.40
2.70
1.20 (or less)
1.50
1.80
2.10
1.20 (or less)
1.50
1.80
2.10
2.40
1.20 (or less)
1.50
1.80
2.10
2.40
2.70
a, b, c
200
200
250
300
200
200
250
300
c
250 (solid )
200
200
300
c
300 (solid )
c
300 (solid )
Note d
Design lateral soil loada (kPa/m)
f
7.00
9.40
200
200
250
250
c
300
250 (solid )
c
c
250 (solid )
250 (solid )
200
200
250
300
c
300
300 (solid )
c
300 (solid )
Note d
c
300 (solid )
Note d
200
200
250
300
c
300
300 (solid )
c
300 (solid )
Note d
Note d
Note d
Note d
Note d
a. For design lateral soil loads, see Section 312.
b. Provisions for this table are based on design and construction requirements specified in Section
406.1.4.3.
c. Solid grouted hollow units or solid masonry units.
d. A design in compliance with reinforcement in accordance with Table 406.2.3-3 is required.
e. For height of unbalanced backfill, see Section 406.1.2.
f. Where unbalanced backfill height exceeds 2.40 m and design lateral soil loads from Table 312.1-1
are used, the requirements for 4.70 and 7.00 kPa/m of depth are not applicable (see Section 312).
TABLE 406.2.3-3 203 mm MASONRY FOUNDATION WALLS WITH REINFORCEMENT WHERE d ≥ 127
a, b, c
mm
MAXIMUM WALL
HEIGHT
(m-mm)
2.20
2.40
2.60
2.80
All rights reserved
MAXIMUM
UNBALANCED
BACKFILL HEIGHTd
(m-mm)
1.20
1.50
1.80
2.10
1.20 (or less)
1.50
1.80
2.10
2.40
1.20 (or less)
1.50
1.80
2.10
e
2.40
1.20 (or less)
MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (mm)
Design lateral soil
loada (kPa/m)
e
4.70
ϕ12 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ14 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ12 at 1200
Design lateral soil
loada (kPa/m)
e
7.00
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ16 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ18 at 1200
ϕ12 at 1200
Design lateral soil
loada (kPa/m)
9.40
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ18 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ18 at 1200
ϕ18 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ18 at 1200
ϕ20 at 1200
ϕ12 at 1200
190 / 496
3.00
1.50
1.80
2.10
2.40
e
2.70
1.20 (or less)
1.50
1.80
2.10
2.40
e
2.70
e
3.00
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ18 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ18 at 1200
ϕ18 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ18 at 1200
ϕ20 at 1200
ϕ12 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ18 at 1200
ϕ20 at 1200
ϕ22 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ18 at 1200
ϕ20 at 1200
ϕ22 at 1200
ϕ12 at 1200
ϕ14 at 1200
ϕ16 at 1200
ϕ18 at 1200
ϕ20 at 1200
ϕ22 at 1200
ϕ22 at 1200
a. For design lateral soil loads, see Section 312.
b. Provisions for this table are based on design and construction requirements specified in Section
406.1.4.3.
c. For alternative reinforcement, see Section 406.1.4.3.
d. For height of unbalanced backfill, see Section 406.1.2.
e. Where unbalanced backfill height exceeds 2.40 m and design lateral soil loads from Table 312.1-1
are used, the requirements for 4.70 and 7.00 kPa/m of depth are not applicable. See Section 312.
TABLE 406.2.3-4 254 mm MASONRY FOUNDATION WALLS WITH REINFORCEMENT WHERE d ≥ 170
a, b,
mm
MAXIMUM WALL
HEIGHT
(m-mm)
2.10
2.40
2.40
2.70
3.00
MAXIMUM
UNBALANCED
BACKFILL HEIGHTd
(m-mm)
1.20 (or less)
1.50
1.80
2.10
1.20 (or less)
1.50
1.80
2.10
2.40
1.20 (or less)
1.50
1.80
2.10
e
2.40
1.20 (or less)
1.50
1.80
2.10
2.40
e
2.70
1.20 (or less)
1.50
1.80
2.10
2.40
e
2.70
e
3.00
MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (mm)
Design lateral soil
loada (kPa/m)
e
4.70
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ18 at 1400
Design lateral soil
loada (kPa/m)
e
7.00
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ18 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ18 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ18 at 1400
ϕ18 at 1400
ϕ20 at 1400
Design lateral soil
loada (kPa/m)
9.40
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ18 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ20 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ16 at 1400
ϕ18 at 1400
ϕ18 at 1400
ϕ12 at 1400
ϕ12 at 1400
ϕ14 at 1400
ϕ18 at 1400
ϕ20 at 1400
ϕ22 at 1400
ϕ22 at 1400
a. For design lateral soil loads, see Section 312.
b. Provisions for this table are based on design and construction requirements specified in Section
406.1.4.3.
All rights reserved
191 / 496
c. For alternative reinforcement, see Section 406.1.4.3.
d. For height of unbalanced backfill, See Section 406.1.2.
e. Where unbalanced backfill height exceeds 2.40 m and design lateral soil loads from Table 312.1-1
are used, the requirements for 4.70 and 7.00 kPa/m of depth are not applicable. See Section 312.
TABLE 406.2.3-5 304 mm MASONRY FOUNDATION WALLS WITH REINFORCEMENT WHERE d ≥ 222
a, b, c
mm
MAXIMUM WALL
HEIGHT
(m-mm)
2.10
2.40
2.40
2.70
3.00
MAXIMUM
UNBALANCED
BACKFILL HEIGHTd
(m-mm)
1.20 (or less)
1.50
1.80
2.10
1.20 (or less)
1.50
1.80
2.10
2.40
1.20 (or less)
1.50
1.80
2.10
e
2.40
1.20 (or less)
1.50
1.80
2.10
2.40
e
2.70
1.20 (or less)
1.50
1.80
2.10
2.40
e
2.70
e
3.00
MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (mm)
Design lateral soil
loada (kPa/m)
e
4.70
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ18 at 1800
Design lateral soil
loada (kPa/m)
e
7.00
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ18 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ18 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ16 at 1800
ϕ18 at 1800
ϕ20 at 1800
Design lateral soil
loada (kPa/m)
9.40
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ20 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ20 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ18 at 1800
ϕ20 at 1800
ϕ12 at 1800
ϕ12 at 1800
ϕ14 at 1800
ϕ16 at 1800
ϕ18 at 1800
ϕ20 at 1800
ϕ22 at 1800
a. For design lateral soil loads, see Section 312.
b. Provisions for this table are based on design and construction requirements specified in Section
406.1.4.3.
c. For alternative reinforcement, see Section 406.1.4.3.
d. For height of unbalanced backfill, see Section 406.1.2.
e. Where unbalanced backfill height exceeds 2.40 m and design lateral soil loads from Table 312.1-1
are used, the requirements for 4.70 and 7.00 kPa/m of depth are not applicable. See Section 312.
SECTION 407 FOUNDATIONS
407.1 GENERAL
Foundations shall be designed and constructed in accordance with Sections 407.2 through 407.8.6.
407.2 DESIGN FOR CAPACITY AND SETTLEMENT
Foundations shall be so designed that the allowable bearing capacity of the soil is not exceeded, and
that differential settlement is minimized.
All rights reserved
192 / 496
407.3 DESIGN LOADS
Foundations shall be designed for the most unfavorable effects due to the combinations of loads
specified in Section 302.3 or 302.4. The dead load is permitted to include the weight of foundations and
overlying fill. Reduced live loads, as specified in Sections 307.9 and 307.11 shall be permitted to be used
in the design of foundations.
407.3.1 SEISMIC OVERTURNING
Where foundations are proportioned using the load combinations of Section 302.3 or 302.4.1,
and the computation of seismic overturning effects is by equivalent lateral force analysis or
modal analysis, the proportioning shall be in accordance with Section 311.6.13.4.
407.4 VIBRATORY LOADS
Where machinery operations or other vibrations are transmitted through the foundation,
consideration shall be given in the foundation design to prevent detrimental disturbances of the soil.
407.5 SHIFTING OR MOVING SOILS
Where it is known that the shallow subsoils are of a shifting or moving character, foundations shall be
carried to a sufficient depth to ensure stability.
407.6 DESIGN FOR EXPANSIVE SOILS
Foundations for buildings and structures founded on expansive soils shall be designed in accordance
with Section 407.6.1 or 407.6.2.
Exception: Foundation design need not comply with Section 407.6.1 or 407.6.2 where one of the
following conditions is satisfied:
1. The soil is removed in accordance with Section 407.6.3; or
2. The building official approves stabilization of the soil.
407.6.1 FOUNDATIONS
Foundations placed on or within the active zone of expansive soils shall be designed to resist
differential volume changes and to prevent structural damage to the supported structure.
Deflection and racking of the supported structure shall be limited to that which will not interfere
with the usability and serviceability of the structure.
Foundations placed below where volume change occurs or below expansive soil shall comply
with the following provisions:
1. Foundations extending into or penetrating expansive soils shall be designed to prevent uplift
of the supported structure.
2. Foundations penetrating expansive soils shall be designed to resist forces exerted on the
foundation due to soil volume changes or shall be isolated from the expansive soil.
407.6.2 SLAB-ON-GROUND FOUNDATIONS
Moments, shears and deflections for use in designing slab-on-ground, mat or raft foundations on
expansive soils shall be determined in accordance with WRI/CRSI Design of Slab-on-Ground
Foundations or PTI Standard Requirements for Analysis of Shallow Concrete Foundations on
Expansive Soils.
407.6.3 REMOVAL OF EXPANSIVE SOIL
Where expansive soil is removed in lieu of designing foundations in accordance with Section
407.6.1 or 407.6.2, the soil shall be removed to a depth sufficient to ensure a constant moisture
content in the remaining soil. Fill material shall not contain expansive soils and shall comply with
Section 403.5 or 403.6.
Exception: Expansive soil need not be removed to the depth of constant moisture, provided the
confining pressure in the expansive soil created by the fill and supported structure exceeds the
swell pressure.
All rights reserved
193 / 496
407.7 FOUNDATIONS ON OR ADJACENT SLOPES
The placement of buildings and structures on or adjacent to slopes steeper than one unit vertical in
three units horizontal (33.3-percent slope) shall comply with Sections 407.7.1 through 407.7.4.
407.7.1 BUILDING CLEARANCE FROM ASCENDING SLOPES
In general, buildings below slopes shall be set a sufficient distance from the slope to provide
protection from slope drainage, erosion and shallow failures. Except as provided in Section
407.7.4 and Figure 407.7.2-1, the following criteria will be assumed to provide this protection.
Where the existing slope is steeper than one unit vertical in one unit horizontal (100-percent
slope), the toe of the slope shall be assumed to be at the intersection of a horizontal plane drawn
from the top of the foundation and a plane drawn tangent to the slope at an angle of 45 degrees
(0.79 rad) to the horizontal. Where a retaining wall is constructed at the toe of the slope, the
height of the slope shall be measured from the top of the wall to the top of the slope.
407.7.2 FOUNDATION SETBACK FROM DESCENDING SLOPE SURFACE
Foundations on or adjacent to slope surfaces shall be founded in firm material with an
embedment and set back from the slope surface sufficient to provide vertical and lat- eral
support for the foundation without detrimental settle- ment. Except as provided for in Section
407.7.4 and Figure 407.7.2-1, the following setback is deemed adequate to meet the criteria.
Where the slope is steeper than 1 unit vertical in 1 unit horizontal (100-percent slope), the
required setback shall be measured from an imaginary plane 45 degree (0.79 rad) to the
horizontal, projected upward from the toe of the slope.
FIGURE 407.7.2-1FOUNDATION CLEARANCES FROM SLOPES
407.7.3 FOUNDATION ELEVATION
On graded sites, the top of any exterior foundation shall extend above the elevation of the street
gutter at point of discharge or the inlet of an approved drainage device a minimum of 300 mm
plus 2 percent.
407.7.4 ALTERNATE SETBACK AND CLEARANCE
Alternate setbacks and clearances are permitted, subject to the approval of the building official.
The building official shall be permitted to require a geotechnical investigation.
407.8 CONCRETE FOUNDATIONS
The design, materials and con- struction of concrete foundations shall comply with Sections 407.8.1
through 407.8.6 and the provisions of section 311.8.
407.8.1 CONCRETE OR GROUT STRENGTH AND MIX PROPORTIONIN
Concrete or grout in foundations shall have a specified compressive strength (f’ c) not less than
the largest applicable value indicated in Table 407.8.6-1.
All rights reserved
194 / 496
407.8.2 CONCRETE COVER
The concrete cover provided for prestressed and nonprestressed reinforcement in foundations
shall be no less than the largest applicable value specified in Table 407.8.6-2. Longitudinal bars
spaced less than 40 mm clear distance apart shall be considered bundled bars for which the
concrete cover provided shall also be no less than that required by Section 506.7.4. Concrete
cover shall be measured from the concrete surface to the outermost surface of the steel to
which the cover requirement applies.
407.8.3 PLACEMENT OF CONCRETE
Concrete shall be placed in such a manner as to ensure the exclusion of any foreign matter and
to secure a full-size foundation. Concrete shall not be placed through water unless a tremie or
other method approved by the building official is used. Where placed
under or in the presence of water, the concrete shall be deposited by approved means to ensure
minimum segregation of the mix and negligible turbulence of the water. Where depositing
concrete from the top of a deep foundation element, the concrete shall be chuted directly into
smooth-sided pipes or tubes or placed in a rapid and continuous operation through a funnel
hopper centered at the top of the element.
407.8.4 PROTECTION OF CONCRETE
Concrete foundations shall be protected from freezing during depositing and for a period of not
less than five days thereafter. Water shall not be allowed to flow through the deposited
concrete.
407.8.5 FORMING OF CONCRETE
Concrete foundations are permitted to be cast against the earth where, in the opinion of the
building official, soil conditions do not require formwork. Where formwork is required, it shall be
in accordance with Section 505.
407.8.6 SEISMIC REQUIREMENTS
For structures assigned to Seismic Design Category D, E or F, provisions of Sections 521.11.1
through 521.11.4, shall apply where not in conflict with the provisions of Sections 407 through 409.
Exceptions:
1. Detached one- and two-family dwellings of light-frame construction and two stories or less
above grade plane are not required to comply with the provisions of Sections 521.12.1
through 521.12.4.
2. Section 521.12.4.4(a) shall not apply.
TABLE 407.8.6-1 MINIMUM SPECIFIED COMPRESSIVE STRENGTH f΄C OF CONCRETE OR GROUT
FOUNDATION ELEMENT OR CONDITION
1. Foundations for structures assigned to Seismic Design Category A, B or C
2a. Foundations for Group R or U occupancies of light-frame construction, two
stories or less in height, assigned to Seismic Design Category D, E or F
2b.Foundations for other structures assigned to Seismic Design Category D, E or F
3. Precast nonprestressed drived piles
4. Socketed drilled shafts
5. Micropiles
6. Precast prestressed driven piles
All rights reserved
SPECIFIED COMPRESSIVE
STRENGTH, f΄C
17.00 MPa
17.00 MPa
21.00 MPa
28.00 MPa
28.00 MPa
28.00 MPa
35.00 MPa
195 / 496
TABLE 407.8.6-2 MINIMUM CONCRETE COVER
FOUNDATION ELEMENT OR CONDITION
1. Shallow foundations
2. Precast nonprestressed deep foundation elements Exposed to
seawater
Not manufactured under plant conditions
Manufactured under plant control conditions
3. Precast prestressed deep foundation elements Exposed to
seawater
Other
4. Cast-in-place deep foundation elements not enclosed by a steel
pipe, tube or permanent casing
5. Cast-in-place deep foundation elements enclosed by a steel
pipe, tube or permanent casing
6. Structural steel core within a steel pipe, tube or permanent
casing
7. Cast-in-place drilled shafts enclosed by a stable rock socket
MINIMUM COVER
In accordance with Section 506.7
75 mm
50 mm
In accordance with Section 506.7.4
65 mm
In accordance with Section 506.7.4
65 mm
25 mm
50 mm
40 mm
SECTION 408 SHALLOW FOUNDATIONS
408.1 GENERAL
Shallow foundations shall be designed and constructed in accordance with Sections 408.2
through 408.6.
408.2 SUPPORTING SOILS
Shallow foundations shall be built on undisturbed soil, compacted fill material or controlled lowstrength material (CLSM). Compacted fill material shall be placed in accordance with Section 403.5.
408.3 STEPPED FOOTINGS
The top surface of footings shall be level. The bottom surface of footings shall be permitted to have a
slope not exceeding one unit vertical in 10 units horizontal (10-percent slope). Footings shall be
stepped where it is necessary to change the elevation of the top surface of the footing or where the
surface of the ground slopes more than one unit verti- cal in 10 units horizontal (10-percent slope).
408.4 DEPTH AND WIDTH OF FOOTINGS
The minimum depth of footings below the undisturbed ground surface shall be 300 mm. Where
applicable, the requirements of Section 408.5 shall also be satisfied. The minimum width of footings
shall be 300 mm.
408.5 FROST PROTECTION
Except where otherwise protected from frost, foundations and other permanent supports of buildings
and structures shall be protected from frost by one or more of the following methods:
1. Extending below the frost line of the locality;
2. Erecting on solid rock.
Exception: Free-standing buildings meeting all of the following conditions shall not be required
to be protected:
1. Assigned to Occupancy Category I, in accordance with Section 301.6;
2. Area of 60 m2 or less for light-frame
408.6 LOCATION OF FOOTINGS
Footings on granular soil shall be so located that the line drawn between the lower edges of adjoining
footings shall not have a slope steeper than 30 degrees (0.52 rad) with the horizontal, unless the
All rights reserved
196 / 496
material sup- porting the higher footing is braced or retained or otherwise lat- erally supported in an
approved manner or a greater slope has been properly established by engineering analysis.
408.7 MASONRY-UNIT FOOTINGS
The design, materials and construction of masonry-unit footings shall comply with Sections 408.7.1
and 408.7.2, and the provisions of Section 701.
408.7.1 DIMENSIONS
Mansonry-unit footings shall be laid in Type M or S mortar complying with Section 703.6 and the
depth shall not be less than twice the projection beyond the wall, pier or column. The width
shall not be less than 200 mm wider than the wall supported thereon.
408.7.2 OFFSETS
The maximum offset of each course in brick foundation walls stepped up from the footings shall
be 38 mm where laid in single courses, and 75 mm where laid in double courses.
408.8 FOOTING SEISMIC TIES
Where a structure is assigned to Seismic Design Category D, E or F in accordance with Section 311,
individual spread footings founded on soil defined in Section 311.4.2 as Site Class E or F shall be
interconnected by ties. Unless it is demonstrated that equivalent restraint is provided
by reinforced concrete beams within slabs on grade or reinforced concrete slabs on grade, ties shall be
capable of carrying, in tension or compression, a force equal to the lesser of the product of the larger
footing design gravity load times the seismic coefficient, SDS, divided by 10 and 25 percent of the
smaller footing design gravity load.
SECTION 409 DEEP FOUNDATIONS
409.1 GENERAL
Deep foundations shall be analyzed, designed, detailed and installed in accordance with Sections
409.1 through 409.4.
409.1.1 GEOTECHNICAL INVESTIGATION
Deep foundations shall be designed and installed on the basis of a geotechnical investigation as set
forth in Section 402.
409.1.2 USE OF EXISTING DEEP FOUNDATION ELEMENTS
Deep foundation elements left in place where a structure has been demolished shall not be used
for the support of new construction unless satisfactory evidence is submitted to the building
official, which indicates that the elements are sound and meet the requirements of this code.
Such elements
shall be load tested or redriven to verify their capacities. The design load applied to such
elements shall be the lowest allowable load as determined by tests or redriving data.
409.1.3 DEEP FOUNDATION ELEMENTS CLASSIFIED AS COLUMNS
Deep foundation elements standing unbraced in air, water or fluid soils shall be classified as
columns and designed as such in accordance with the provisions of this code from their top down
to the point where adequate lateral support is provided in accordance with Section 409.2.1.
Exception: Where the unsupported height to least horizontal dimension of a cast-in-place deep
foundation element does not exceed three, it shall be permitted to design and construct such an
element as a pedestal.
All rights reserved
197 / 496
409.1.4 SPECIAL TYPES OF DEEP FOUNDATIONS
The use of types of deep foundation elements not specifically mentioned herein is permitted,
subject to the approval of the building official, upon the submission of acceptable test data,
calculations and other information relating to the structural properties and load capacity of such
elements. The allowable stresses for materials shall not in any case exceed the limitations
specified herein.
409.2 ANALYSIS
The analysis of deep foundations for design shall be in accordance with Sections 409.2.1
through 409.2.5.
409.2.1 LATERAL SUPPORT
Any soil other than fluid soil shall be deemed to afford sufficient lateral support to prevent
buckling of deep foundation elements and to permit the design of the elements in accordance
with accepted engi- neering practice and the applicable provisions of this code.
Where deep foundation elements stand unbraced in air, water or fluid soils, it shall be permitted
to consider them laterally supported at a point 1500 mm into stiff soil or 3000 mm into soft
soil unless otherwise approved by the building official on the basis of a geotechnical investigation
by a registered design professional.
409.2.2 STABILITY
Deep foundation elements shall be braced to provide lateral stability in all directions. Three or
more elements connected by a rigid cap shall be considered braced, provided that the elements
are located in radial directions from the centroid of the group not less than 60 degrees (1 rad)
apart. A two-element group in a rigid cap shall be considered to be braced along the axis
connecting the two elements. Methods used to brace deep foundation elements shall be subject
to the approval of the building official.
Deep foundation elements supporting walls shall be placed alternately in lines spaced at least
300 mm apart and located symmetrically under the center of gravity of the wall load carried,
unless effective measures are taken to provide for eccentricity and lateral forces, or the
foundation elements are adequately braced to provide for lateral stability.
Exceptions:
1. Isolated cast-in-place deep foundation elements without lateral bracing shall be
permitted where the least horizontal dimension is no less than 610 mm, adequate
lateral support in accordance with Section 409.2.1 is provided for the entire height and
the height does not exceed 12 times the least horizontal dimension.
2. A single row of deep foundation elements without lateral bracing is permitted for oneand two-family dwellings and lightweight construction not exceeding two stories above
grade plane or 10 600 mm in building height, provided the centers of the elements are
located within the width of the supported wall.
409.2.3 SETTLEMENT
The settlement of a single deep foundation element or group thereof shall be estimated based on
approved methods of analysis.
409.2.4 LATERAL LOADS
The moments, shears and lateral deflections used for design of deep foundation elements shall
be established considering the nonlinear interaction of the shaft and soil, as determined by a
registered design professional. Where the ratio of the depth of embedment of the element to its
least horizontal dimension is less than or equal to six, it shall be permitted to assume the element
is rigid.
All rights reserved
198 / 496
409.2.4.1 SEISMIC DESIGN CATEGORIES D THROUGH F
For structures assigned to Seismic Design Category D, E or F, deep foundation elements on Site
Class E or F sites, as determined in Section 311.4.2, shall be designed and constructed to
withstand maximum imposed curvatures from earthquake ground motions and structure
response.
409.2.5 GROUP EFFECTS
The analysis shall include group effects on lateral behavior where the center-to-center spacing of
deep foundation elements in the direction of lateral force is less than eight times the least
horizontal dimension of an element. The analysis shall include group effects on axial behavior
where the center-to-center spacing of deep foundation elements is less than three times the
least horizontal dimension of an element.
409.3 DESIGN AND DETAILING
Deep foundations shall be designed and detailed in accordance with Sections 409.3.1 through
409.3.12.
409.3.1 DESIGN CONDITIONS
Design of deep foundations shall include the design conditions specified in Sections 409.3.1.1
through 409.3.1.5, as applicable.
409.3.1.1 DESIGN METHODS FOR CONCRETE ELEMENTS
Where concrete deep foundations are laterally supported in accordance with Section 409.2.1
for the entire height and applied forces cause bending moments no greater than those
resulting from accidental eccentricities, struc- tural design of the element using the load
combinations of Section 302.4 and the allowable stresses specified in this chapter shall be
permitted. Otherwise, the structural design of concrete deep foundation elements shall use
the load combinations of Section 302.3 and approved strength design methods.
409.3.1.2 COMPOSITE ELEMENTS
Where a single deep foundation element comprises two or more sections of different
materials or different types spliced together, each section of the composite assembly shall
satisfy the applicable requirements of this code, and the maximum allowable load in each
section shall be limited by the structural capacity of that section.
409.3.1.3 MISLOCATION
The foundation or superstructure shall be designed to resist the effects of the mislocation
of any deep foundation element by no less than 75 mm. To resist the effects of
mislocation, compressive overload of deep foundation elements to 110 percent of the
allowable design load shall be permitted.
409.3.1.4 DRIVEN PILES
Driven piles shall be designed and manufactured in accordance with accepted engineering
practice to resist all stresses induced by handling, driving and service loads.
409.3.1.5 CASINGS
Temporary and permanent casings shall be of steel and shall be sufficiently strong to resist
collapse and sufficiently water tight to exclude any foreign materials during the placing of
concrete. Where a permanent casing is considered reinforcing steel, the steel shall be
protected. Horizontal joints in the casing shall be spliced in accordance with Section 409.3.7.
409.3.2 MATERIALS
The materials used in deep foundation elements shall satisfy the requirements of Sections
409.3.2.1 through 409.3.3.2 as applicable.
All rights reserved
199 / 496
409.3.2.1 CONCRETE
Where concrete is cast in a steel pipe or where an enlarged base is formed by compacting
concrete, the maximum size for coarse aggregate shall be 20.0 mm. Concrete to be compacted
shall have a zero slump.
409.3.2.1.1 SEISMIC HOOKS
For structures assigned to Seismic Design Category C, D, E or F in accordance with
Section 311, the ends of hoops, spirals and ties used in concrete deep foundation
elements shall be terminated with seismic hooks, and shall be turned into the confined
concrete core.
409.3.3 ALLOWABLE STRESSES
The allowable stresses for materials used in deep foundation elements shall not exceed those
specified in Table 409.3.3-1.
TABLE 409.3.3-1 ALLOWABLE STRESSES FOR MATERIALS USED IN DEEP FOUNDATION ELEMENTS
MATERIAL TYPE AND CONDITION
b
1. Concrete or grout in compression
Cast-in-place with a permanent casing in accordance with Section 409.3.3.1
Cast-in-place in a pipe, tube, other permanent casing or rock
Cast-in-place without a permanent casing
Precast nonprestressed
Precast prestressed
2. Nonprestressed reinforcement in compression
3. Structural steel in compression
Cores within concrete-filled pipes or tubes
Pipes, tubes or H-piles, where justified in accordance with Section 409.3.3.2
Pipes or tubes for micropiles
Other pipes, tubes or H-piles
Helical piles
4. Nonprestressed reinforcement in tension
Within micropiles
Other conditions
5. Structural steel in tension
Pipes, tubes or H-piles, where justified in accordance with Section 409.3.3.2
Other pipes, tubes or H-piles
Helical piles
MAXIMUM ALLOWABLE STRESS
a
0.4 f ΄c
0.33 f΄c
0.3 f΄c
0.33 f ΄c
0.33 f΄c - 0.27 fpc
0.4 fy ≤ 436 k a
0.5 fy ≤ 436 k a
0.5 fy ≤ 436 k a
0.4 fy ≤ 436 k a
0.35 fy ≤ 218 k a
0.6 Fy ≤ 0.5 Fu
0.6 fy
0.5 fy ≤ 150 k a
0.5 Fy ≤ 436 k a
0.35 Fy ≤ 218 k a
0.6 Fy ≤ 0.5Fu
a. f΄c is the specified compressive strength of the concrete or grout; fpc is the compressive stress on
the gross concrete section due to effective prestress forces only; fy is the specified yield strength of
reinforcement; Fy is the specified minimum yield stress of structural steel; Fu is the specified
minimum tensile stress of structural steel.
b. The stresses specified apply to the gross cross-sectional area within the concrete surface. Where a
temporary or permanent casing is used, the inside face of the casing shall be considered the
concrete surface.
409.3.3.1 INCREASED ALLOWABLE COMPRESSIVE STRESS FOR CASED CAST-IN-PLACE
ELEMENTS
The allowable compressive stress in the concrete shall be permitted to be increased as
specified in Table 409.3.3-1 for those portions of permanently cased cast-in-place elements
that satisfy all of the following conditions:
1. The design shall not use the casing to resist any portion of the axial load imposed.
2. The casing shall have a sealed tip and be mandrel driven.
3. The thickness of the casing shall not be less than manufacturer’s standard gage No. 14
(1.75 mm).
4. The casing shall be seamless or provided with seams of strength equal to the basic
material and be of a configuration that will provide confinement to the cast-in-place
concrete.
All rights reserved
200 / 496
5. The ratio of steel yield strength (Fy) to specified compressive strength (f΄c) shall not be
less than six.
6. The nominal diameter of the element shall not be greater than 400 mm.
409.3.3.2 JUSTIFICATION OF HIGHER ALLOWABLE STRESSES
Use of allowable stresses greater than those specified in Section 409.3.3 shall be permitted
where supporting data justifying such higher stresses is filed with the building official. Such
substantiating data shall include:
1. A geotechnical investigation in accordance with Section 402; and
2. Load tests in accordance with Section 409.3.4.1.2, regardless of the load supported by the
element. The design and installation of the deep foundation elements shall be under the
direct supervision of a registered design professional knowledgeable in the field of soil
mechanics and deep foundations who shall submit a report to the building official stating
that the elements as installed satisfy the design criteria.
409.3.4 DETERMINATION OF ALLOWABLE LOADS
The allowable axial and lateral loads on deep foundation elements shall be determined by an
approved formula, load tests or method of analysis.
409.3.4.1 ALLOWABLE AXIAL LOAD
The allowable axial load on a deep foundation element shall be determined in accordance
with Sections 409.3.4.1.1 through 409.3.4.1.7.
409.3.4.1.1 DRIVING CRITERIA
The allowable compressive load on any driven deep foundation element where
determined by the application of an approved driving formula shall not exceed 350 kN.
For allowable loads above 350 kN, the wave equation method of analysis shall be used to
estimate driveability for both driving stresses and net displacement per blow at the
ultimate load. Allowable loads shall be verified by load tests in accordance with Section
409.3.4.1.2.
409.3.4.1.2 LOAD TESTS
Where design compressive loads are greater than those determined using the allowable
stresses specified in Section 409.3.3, where the design load for any deep foundation
element is in doubt, or where cast-in-place deep foundation elements have an enlarged
base formed either by compacting concrete or by driving a precast base, control test
elements shall be tested in accordance with ASTM D 1143 or ASTM D 4945. At least one
element shall be load tested in each area of uniform subsoil conditions. Where required
by the building official, additional elements shall be load tested where necessary to
establish the safe design capacity. The resulting allowable loads shall not be more
than one-half of the ultimate axial load capacity of the test element as assessed by one of
the published methods listed in Section 409.3.4.1.3 with consideration for the test type,
duration and subsoil. The ultimate axial load capacity shall be determined by a registered
design professional with consideration given to tolerable total and differential settlements
at design load in accordance with Section 409.2.3. In subsequent installation of the
balance of deep foundation elements, all elements shall be deemed to have a supporting
capacity equal to that of the control element where such elements are of the same type,
size and relative length as the test element; are installed using the same or comparable
methods and equipment as the test element; are installed in similar subsoil conditions as
the test element; and, for driven elements, where the rate of penetration (e.g., net
displacement per blow) of such elements is equal to or less than that of the test element
driven with the same hammer through a comparable driving distance.
All rights reserved
201 / 496
409.3.4.1.3 LOAD TEST EVALUATION METHOD
It shall be permitted to evaluate load tests of deep foundation elements using any of the
following methods:
1. Davisson Offset Limit.
2. Brinch-Hansen 90% Criterion.
3. Butler-Hoy Criterion.
4. Other methods approved by the building official.
409.3.4.1.4 ALLOWABLE FRICTIONAL RESISTANCE
The assumed frictional resistance developed by any uncased cast-in-place deep
foundation element shall not exceed one-sixth of the bearing value of the soil material
at minimum depth as set forth in Table 405.3.4-1, up to a maximum of 24 kPa, unless
a greater value is allowed by the building official on the basis of a geotechnical
investigation as specified in Section 402 or a greater value is substantiated by a load test
in accordance with Section 409.3.4.1.2. Frictional resistance and bearing resistance shall
not be assumed to act simultaneously unless determined by a geotechnical investigation
in accordance with Section 402.
409.3.4.1.5 UPLIFT OF A SINGLE DEEP FOUNDATION ELEMENT
Where required by the design, the uplift capacity of a single deep foundation element
shall be determined by an approved method of analysis based on a minimum factor of
safety of three or by load tests conducted in accordance with ASTM D 3689. The
maximum allowable uplift load shall not exceed the ultimate load capacity as
determined in Section 409.3.4.1.2, using the results of load tests conducted in
accordance with ASTM D 3689, divided by a factor of safety of two.
Exception: Where uplift is due to wind or seismic loading, the minimum factor of safety
shall be two where capacity is determined by an analysis and one and one-half where
capacity is determined by load tests.
409.3.4.1.6 UPLIFT CAPACITY OF GROUPED DEEP FOUNDATION ELEMENTS
For grouped deep foundation elements subjected to uplift, the allowable working uplift
load for the group shall be calculated by an approved method of analysis where the
deep foundation elements in the group are placed at a center-to-center spacing of at
least 2.5 times the least horizontal dimension of the largest single element, the allowable
working uplift load for the group is permitted to be calculated as the lesser of:
1. The proposed individual uplift working load times the number of elements in the
group.
2. Two-thirds of the effective weight of the group and the soil contained within a block
defined by the perimeter of the group and the length of the element.
409.3.4.1.7 LOAD-BEARING CAPACITY
Deep foundation elements shall develop ultimate load capacities of at least twice the
design working loads in the designated load-bearing layers. Analysis shall show that no
soil layer underlying the designated load-bearing layers causes the load-bearing capacity
safety factor to be less than two.
409.3.4.2 ALLOWABLE LATERAL LOAD
Where required by the design, the lateral load capacity of a single deep foundation element or
a group thereof shall be determined by an approved method of analysis or by lateral load tests
to at least twice the proposed design working load. The resulting allowable load shall not be
more than one-half of the load that produces a gross lateral movement of 25 mm at the
lower of the top of foundation element and the ground surface, unless it can be shown that
All rights reserved
202 / 496
the predicted lateral movement shall cause neither harmful distortion of, nor instability in the
structure, nor cause any element to be loaded beyond its capacity.
409.3.5 SUBSIDING SOILS
Where deep foundation elements are installed through subsiding fills or other subsiding strata
and derive support from underlying firmer materials, consideration shall be given to the
downward frictional forces that may be imposed on the elements by the subsiding upper strata.
Where the influence of subsiding fills is considered as imposing loads on the element, the
allowable stresses specified in this chapter shall be permitted to be increased where satisfactory
substantiating data are submitted.
409.3.6 DIMENSIONS OF DEEP FOUNDATION ELEMENTS
The dimensions of deep foundation elements shall be in accordance with Sections 409.3.6.1
through 409.3.6.2.3, as applicable.
409.3.6.1 PRECAST
The minimum lateral dimension of precast concrete deep foundation elements shall be 200
mm. Corners of square elements shall be chamfered.
409.3.6.2 CAST-IN-PLACE OR GROUTED-IN-PLACE
Cast-in-place and grouted-in-place deep foundation elements shall satisfy the requirements
of this section.
409.3.6.2.1 CASED
Cast-in-place deep foundation elements with a permanent casing shall have a nominal
outside diameter of not less than 200 mm.
409.3.6.2.2 UNCASED
Cast-in-place deep foundation elements without a permanent casing shall have a
diameter of not less than 300 mm. The element length shall not exceed 30 times the
average diameter.
409.3.6.2.3 MICROPILES
Micropiles shall have an outside diameter of 300 mm or less. The minimum diameter
set forth elsewhere in Section 409.3.6 shall not apply to micropiles.
409.3.7 SPLICES
Splices shall be constructed so as to provide and maintain true alignment and position of the
component parts of the deep foundation element during installation and subsequent thereto and
shall be designed to resist the axial and shear forces and moments occurring at the loca- tion of
the splice during driving and for design load combi- nations. Where deep foundation elements of
the same type are being spliced, splices shall develop not less than 50 percent of the bending
strength of the weaker section. Where deep foundation elements of different materials or
different types are being spliced, splices shall develop the full compressive strength and not less
than 50 percent of the tension and bending strength of the weaker section. Where structural
steel cores are to be spliced, the ends shall be milled or ground to provide full contact and shall be
full-depth welded.
Splices occurring in the upper 3000 mm of the embedded portion of an element shall be
designed to resist at allowable stresses the moment and shear that would result from an assumed
eccentricity of the axial load of 75 mm, or the element shall be braced in accordance with
Section 1810.2.2 to other deep foundation elements that do not have splices in the upper 3000
mm of embedment.
All rights reserved
203 / 496
409.3.7.1 SEISMIC DESIGN CATEGORIES C THROUGH F
For structures assigned to Seismic Design Category C, D, E or F splices of deep foundation
elements shall develop the lesser of the following:
1. The full strength of the deep foundation element; and
2. The axial and shear forces and moments from the load combinations with overstrength
factor in Section 311.6.4.3.2.
409.3.8 TOP OF ELEMENT DETAILING AT CUTOFFS
Where a minimum length for reinforcement or the extent of closely spaced confinement
reinforcement is specified at the top of a deep foundation element, provisions shall be made so
that those specified lengths or extents are maintained after cut- off.
409.3.9 PRECAST CONCRETE PILES
Precast concrete piles shall be designed and detailed in accordance with Sections 409.3.9.1
through 409.3.9.3.
409.3.9.1 REINFORCEMENT
Longitudinal steel shall be arranged in a symmetrical pattern and be laterally tied with steel
ties or wire spiral spaced center to center as fol- lows:
1. At not more than 25 mm for the first five ties or spirals at each end; then
2. At not more than 100 mm, for the remainder of the first 600 mm from each end; and
then
3. At not more than 150 mm elsewhere. The size of ties and spirals shall be as follows:
- For piles having a least horizontal dimension of 400 mm or less, wire shall not be
smaller than 8 mm.
- For piles having a least horizontal dimension of more than 400 mm and less than
500 mm, wire shall not be smaller than 8 mm.
- For piles having a least horizontal dimension of 500 mm and larger, wire shall not
be smaller than 8 mm.
409.3.9.2 PRECAST NONPRESTRESSED PILES
Precast nonprestressed concrete piles shall comply with the requirements o f S ections
409.3.9.2.1 through 409.3.9.2.3.
409.3.9.2.1 MINIMUM REINFORCEMENT
Longitudinal reinforcement shall consist of at least four bars with a minimum
longitudinal reinforcement ratio of 0.008.
409.3.9.2.2 SEISMIC REINFORCEMENT ON SEISMIC DESIGN CATEGORIES C
THROUGH F
For structures assigned to Seismic Design Category C, D, E or F in accordance with
Section 311, precast nonpre- stressed piles shall be reinforced as specified in this
section. The minimum longitudinal reinforcement ratio shall be 0.01 throughout the
length. Transverse reinforcement shall consist of closed ties or spirals with a minimum
10 mm diameter. Spacing of transverse reinforcement shall not exceed the smaller of
eight times the diameter of the smallest longitudinal bar or 150 mm within a distance of
three times the least pile dimension from the bot- tom of the pile cap. Spacing of
transverse reinforcement shall not exceed 150 mm throughout the remainder of the
pile.
All rights reserved
204 / 496
409.3.9.2.3 ADDITIONAL SEISMIC REINFORCEMENT ON SEISMIC DESIGN CATEGORIES D
THROUGH F
For struc- tures assigned to Seismic Design Category D, E or F in accordance with Section
311, transverse rein- forcement shall be in accordance with Section 1810.3.9.4.2.
409.3.9.3 PRECAST PRESTRESSED PILES
Precast pre- stressed concrete piles shall comply with the requirements of this Chapter.
409.3.10 CAST-IN-PACE DEEP FOUNDATIONS
Cast-in-place deep foundation elements shall be designed and detailed in accordance with
Sections 409.3.10.1 through 409.3.10.4.
409.3.10.1 DESIGN CRACKNING MOMENT
The design cracking moment ( Mn) for a cast-in-place deep foundation element not
enclosed by a structural steel pipe or tube shall be determined using the following equation:
√
EQUATION 409.3.10.1-1
where:
f΄c = Specified compressive strength of concrete or grout, MPa
Sm = Elastic section modulus, neglecting reinforce- ment and casing, cubic mm3
409.3.10.2 REQUIRED REINFORCEMENT
Where subject to uplift or where the required moment strength determined using the load
combinations of Section 302.3 exceeds the design cracking moment determined in
accordance with Section 409.3.10.1, cast-in-place deep foundations not enclosed by a
structural steel pipe or tube shall be reinforced.
409.3.10.3 PLACEMENT OF REINFORCEMENT
Reinforcement where required shall be assembled and tied together and shall be placed in
the deep foundation ele- ment as a unit before the reinforced portion of the element is filled
with concrete.
Exceptions:
1. Steel dowels embedded 1500 mm or less shall be permitted to be placed after
concreting, while the concrete is still in a semifluid state.
2. For deep foundation elements installed with a hollow-stem auger, tied
reinforcement shall be placed after elements are concreted, while the concrete is
still in a semifluid state. Longitudi- nal reinforcement without lateral ties shall be
placed either through the hollow stem of the auger prior to concreting or after
concreting, while the concrete is still in a semifluid state.
3. For Group R-3 and U occupancies not exceeding two stories of light-frame
construction, reinforcement is permitted to be placed after concreting, while the
concrete is still in a semi- fluid state, and the concrete cover requirement is
permitted to be reduced to 50mm, provided the construction method can be
demonstrated to the satisfaction of the building official.
409.3.10.4 SEISMIC REINFORCEMENT
Where a structure is assigned to Seismic Design Category C, reinforcement shall b e
provided i n accordance with Section 1810.3.9.4.1. Where a structure is assigned to
Seismic Design Category D, E or F, reinforcement shall be provided in accordance with
Section 409.3.10.4.2.
All rights reserved
205 / 496
Exceptions:
1. Isolated deep foundation elements supporting posts of Group R-3 and U occupancies
not exceeding two stories of light-frame construction shall be permitted to be
reinforced as required by rational analysis but with not less than one ϕ 4 bar, without
ties or spirals, where detailed so the element is not subject to lateral loads and the
soil provides adequate lateral support in accordance with
2. Isolated deep foundation elements supporting posts and bracing from decks and
patios appurtenant to Group R-3 and U occupancies not exceeding two stories of
light-frame construction shall be permitted to be reinforced as required by rational
analysis but with not less than one No. 4 bar, without ties or spirals, where the lateral
load, E, to the top of the element does not exceed 890 N and the soil provides
adequate lateral support in accordance with Section 409.2.1.
3. Deep foundation elements supporting the concrete foundation wall of Group R-3 and
U occupancies not exceeding t wo stories o f light-frame construction shall be
permitted to be reinforced as required by rational analysis but with not less than two
No. 4 bars, without ties or spirals, where the design cracking moment determined in
accordance with Section 409.3.10.1 exceeds the required moment strength
determined using the load combinations with overstrength factor in Section
311.6.4.3.2 and the soil provides adequate lateral support in accordance with Section
409.2.1.
4. Closed ties or spirals where required by Section 409.3.10.4.2 shall be permitted to be
limited to the top 900 mm of deep foundation ele- ments 3000 mm or less in depth
supporting Group R-3 and U occupancies of Seismic Design Category D, not
exceeding two stories of light-frame construction.
409.3.10.4.1 SEISMIC REINFORCEMENT IN SEISMIC DESIGN CATEGORY C
For structures assigned to Seis- mic Design Category C in accordance with Section 311,
cast-in-place deep foundation elements shall be reinforced as specified in this section.
Reinforcement shall be provided where required by analysis.
A minimum of four longitudinal bars, with a minimum longitudinal reinforcement ratio of
0.0025, shall be provided for throughout the minimum reinforced length of the element
as defined below starting at the top of the element. The minimum reinforced length of the
element shall be taken as the greatest of the following:
1. One-third of the element length;
2. A distance of 3000 mm;
3. Three times the least element dimension; and
4. The distance from the top of the element to the point where the design cracking
moment determined in accordance with Section 409.3.10.1 exceeds the required
moment strength deter- mined using the load combinations of Section 302.3.
Transverse reinforcement shall consist of closed ties or spirals with a minimum 10 mm
diameter. Spacing of transverse reinforcement shall not exceed the smaller of 150 mm or
8-longitudinal-bar diameters, within a distance of three times the least element
dimension from the bottom of the pile cap. Spacing of transverse reinforcement shall
not exceed 16 longitudinal bar diameters throughout the remainder of the reinforced
length.
Exceptions:
1. The requirements of this section shall not apply to concrete cast in structural steel
pipes or tubes.
2. A spiral-welded metal casing of a thickness not less than manufacturer’s standard
gage No. 14 gage (0.17 mm) is permitted to provide concrete confinement in lieu of
the closed ties or spirals. Where used as such, the metal casing shall be protected
All rights reserved
206 / 496
against possible deleterious action due to soil constituents, changing water levels or
other factors indicated by boring records of site conditions.
409.3.10.4.2 SEISMIC REINFORCEMENT IN SEISMIC DESIGN CATEGORIES D
THROUGH F
For structures assigned to Seismic Design Category D, E or F in accordance with Section
311, cast-in-place deep foundation elements shall be reinforced as specified in this
section. Reinforcement shall be provided where required by analysis.
A minimum of four longitudinal bars, with a mini- mum longitudinal reinforcement ratio
of 0.005, shall be provided throughout the minimum reinforced length of the element
as defined below starting at the top of the element. The minimum reinforced length of the
element shall be taken as the greatest of the following:
1. One-half of the element length;
2. A distance of 3000 mm;
3. Three times the least element dimension; and
4. The distance from the top of the element to the point where the design cracking
moment determined in accordance with Section 409.3.10.1 exceeds the required
moment strength deter- mined using the load combinations of Section 302.3.
Transverse reinforcement shall consist of closed ties or spirals no smaller than No. 3 bars
for elements with a least dimension up to 500mm, and ϕ 4 bars for larger elements.
Throughout the remainder of the reinforced length outside the regions with transverse
confinement reinforcement, as specified in Section 409.3.10.4.2.1 or 409.3.10.4.2.2, the
spacing of transverse reinforcement shall not exceed the least of the following:
1. 12 longitudinal bar diameters;
2. One-half the least dimension of the element; and
3. 300 mm.
Exceptions:
1. The requirements of this section shall not apply to concrete cast in structural steel
pipes or tubes.
2. A spiral-welded metal casing of a thickness not less than manufacturer’s standard
gage No. 14 gage (1.700 mm) is permitted to provide concrete confinement in lieu
of the closed ties or spirals. Where used as such, the metal casing shall be protected
against possible deleterious action due to soil constituents, changing water levels or
other factors indicated by boring records of site conditions.
409.3.10.4.2.1 SITE CLASSES A THROUGH D
For Site Class A, B, C or D sites, transverse confinement reinforcement shall be
provided in the element in accordance with Sections 521.6.4.2 , 521.6.4.3 and
521.6.4.4 of within three times the least element dimension of the bottom of the
pile cap. A transverse spiral reinforcement ratio of not less th an one-hal f o f t
hat r equi red i n Sect i o n 521.6.4.4(a) shall be permitted.
409.3.10.4.2.2 SITE CLASSES E AND F
For Site Class E or F sites, transverse confinement rein- forcement shall be provided
in the element in accordance with Sections 521.6.4.2, 521.6.4.3 and 521.6.4.4
within seven times the least element dimension of the pile cap and within seven times
the least element dimension of the interfaces of strata that are hard or stiff and
strata that are liquefiable or are composed of soft- to medium- stiff clay.
409.3.10.5 BELLED DRILLED SHAFTS
Where drilled shafts are belled at the bottom, the edge thickness of the bell shall not be less
than that required for the edge of footings. Where the sides of the bell slope at an angle less
than 60 degrees (1 rad) from the horizontal, the effects of vertical shear shall be considered.
All rights reserved
207 / 496
409.3.10.6 SOCKETED DRILLED SHAFTS
Socketed drilled shafts shall have a permanent pipe or tube casing that extends down to
bedrock and an uncased socket drilled into the bedrock, both filled with concrete. Socketed
drilled shafts shall have reinforcement or a structural steel core for the length as indicated
by an approved method of analysis.
The depth of the rock socket shall be sufficient to develop the full load-bearing capacity of
the element with a minimum safety factor of two, but the depth shall not be less than the
outside diameter of the pipe or tube casing. The design of the rock socket is permitted to be
predicated on the sum of the allowable load-bearing pressure on the bottom of the
socket plus bond along the sides of the socket. Where a structural steel core is used, the
gross cross-sectional area of the core shall not exceed 25 percent of the gross area of the
drilled shaft.
409.3.11 PILE CAPS
Pile caps shall be of reinforced concrete, and shall include all elements to which vertical deep
foundation elements are connected, including grade beams and mats. The soil immediately
below the pile cap shall not be considered as carrying any vertical load. The tops of ver tical deep
foundation elements shall be embedded not less than 75 mm into pile caps and the caps shall
extend at least 100 mm beyond the edges of the elements. The tops of elements shall be cut or
chipped back to sound material before capping.
409.3.11.1 SEISMIC DESIGN CATEGORIES C THROUGH F
For structures assigned to Seismic Design Category C, D, E or F in accordance with Section 311,
concrete deep foundation elements shall be connected to the pile cap by embedding the
element reinforcement or field-placed dowels anchored in the element into the pile cap for a
distance equal to their development length in accordance with ACI. For deformed bars, the
development length is the full development length for compression, or tension in the case of
uplift, without reduction for excess reinforcement in accordance with Section 311.6.2.5.
Alternative measures for laterally confining concrete and maintaining toughness and ductilelike behavior at the top of the element shall be permitted pro- vided the design is such that
any hinging occurs in the confined region.
The minimum transverse steel ratio for confinement shall not be less than one-half of that
required for columns.
409.3.11.2 SEISMIC DESIGN CATEGORIES D THROUGH F
For structures assigned to Seismic Design Category D, E or F in accordance with Section 311,
deep foundation element resistance to uplift forces or rotational restraint shall be provided
by anchorage into the pile cap, designed considering the combined effect of axial forces due
to uplift and bending moments due to fixity to the pile cap. Anchorage shall develop a
minimum of 25 percent of the strength of the element in tension. Anchorage into the pile cap
shall be capable of developing the following:
1. In the case of uplift, the least of the following: nominal tensile strength of the longitudinal
reinforcement in a concrete element; the nominal ten- sile strength of a steel element;
the frictional force developed between the element and the soil multi- plied by 1.3; and
the axial tension force resulting from the load combinations with overstrength fac- tor in
Section 311.6.4.3.2.
2. In the case of rotational restraint, the lesser of the following: the axial force, shear forces
and bend- ing moments resulting from the load combinations with overstrength factor in
Section 311.612.4.3.2 or development of the full axial, bending and shear nominal strength of
the element.
All rights reserved
208 / 496
Where the vertical lateral-force-resisting elements are columns, the pile cap flexural
strengths shall exceed the column flexural strength. The connection between batter piles and
pile caps shall be designed to resist the nominal strength of the pile acting as a short column.
Batter piles and their connection shall be capable of resisting forces and moments from the
load combinations with overstrength factor in Section 311.6.4.3.2.
409.3.12 GRADE BEAMS
For structures assigned to Seismic Design Category D, E or F in accordance with Section 311, grade
beams shall comply with the provisions in Section 521.12.3 for grade beams, except where
they have the capacity to resist the forces from the load combinations with overstrength factor
in Section 311.6.4.3.2.
409.3.13 SEISMIC TIES
For structures assigned to Seismic Design Category C, D, E or F in accordance with Section 311,
individual deep foundations shall be interconnected by ties. Unless it can be demonstrated that
equivalent restraint is provided by reinforced concrete beams within slabs on grade or reinforced
concrete slabs on grade or confinement by competent rock, hard cohesive soils or very dense
granular soils, ties shall be capable of carrying, in ten- sion or compression, a force equal to the
lesser of the prod- uct of the larger pile cap or column design gravity load times the seismic
coefficient, SDS, divided by 10, and 25 percent of the smaller pile or column design gravity load.
Exception: In Group R-3 and U occupancies of light-frame construction, deep foundation
elements sup- porting foundation walls, isolated interior posts detailed so the element is not
subject to lateral loads or exterior decks and patios are not subject to interconnection where the
soils are of adequate stiffness, subject to the approval of the building official.
409.4 INSTALLATION
Deep foundations shall be installed in accordance with Section 409.4. Where a single deep foundation
element comprises two or more sections of different materials or different types spliced together, each
section shall satisfy the applicable conditions of installation.
409.4.1 STRUCTURAL INTEGRITY
Deep foundation elements shall be installed in such a manner and sequence as to prevent
distortion or damage that may adversely affect the structural integrity of adjacent structures or
of foundation elements being installed or already in place and as to avoid compacting the
surrounding soil to the extent that other foundation elements cannot be installed properly.
409.4.1.1 COMPRESSIVE STRENGTH OF PRECAST CONCRETE PILES
A precast concrete pile shall not be driven before the concrete has attained a compressive
strength of at least 75 percent of the specified compressive strength (f’c), but not less than the
strength sufficient to withstand handling and driving forces.
409.4.1.2 CASING
Where cast-in-place deep foundation elements are formed through unstable soils and
concrete is placed in an open-drilled hole, a casing shall be inserted in the hole prior to
placing the concrete. Where the casing is withdrawn during concreting, the level of concrete
shall be maintained above the bottom of the casing at a sufficient height to offset any
hydrostatic or lateral soil pressure. Driven casings shall be mandrel driven their full length in
contact with the surrounding soil.
409.4.1.3 DRIVING NEAR UNCASED CONCRETE
Deep foundation elements shall not be driven within six element diameters center to center
in granular soils or within one-half the element length in cohesive soils of an uncased
element filled with concrete less than 48 hours old unless approved by the building official. If
All rights reserved
209 / 496
the concrete surface in any completed element rises or drops, the element shall be replaced.
Driven uncased deep foundation elements shall not be installed in soils that could cause
heave.
409.4.1.4 DRIVING NEAR CASED CONCRETE
Deep foundation elements shall not be driven within four and one-half average diameters of a
cased element filled with concrete less than 24 hours old unless approved by the building
official. Concrete shall not be placed in casings within heave range of driving.
409.4.2 IDENTIFICATION
Deep foundation materials shall be identified for conformity to the specified grade with this
identity maintained continuously from the point of manu- facture to the point of installation or
shall be tested by an approved agency to determine conformity to the specified grade. The
approved agency shall furnish an affidavit of compliance to the building official.
409.4.3 LOCATION PLAN
A plan showing the location and designation of deep foundation elements by an identifica- tion
system shall be filed with the building official prior to installation of such elements. Detailed
records for elements shall bear an identification corresponding to that shown on the plan.
409.4.4 PREEXCAVATION
The use of jetting, augering or other methods of preexcavation shall be subject to the approval
of the building official. Where permitted, preexcavation shall be carried out in the same manner
as used for deep foundation elements subject to load tests and in such a manner that will not
impair the carrying capacity of the elements already in place or damage adjacent structures.
Element tips shall be driven below the preexcavated depth until the required resistance or
penetration is obtained.
409.4.5 SPECIAL INSPECTION
Special inspections in accordance with Sections 903.8 and 903.9 shall be provided for driven and
cast-in-place deep foundation elements, respectively. Special inspections in accordance with
Section 903.10 shall be provided for helical piles.
All rights reserved
210 / 496
CHAPTER 5
CONCRETE
SECTION 501 GENERAL
501.1 SCOPE
The provisions of this chapter shall govern the materials, quality control, design and construction of
concrete used in structures. This Chapter does not govern design and construction of tanks and
reservoirs.
501.2 PLAIN AND REINFORCED CONCRETE
Structural concrete shall be designed and constructed in accordance with the requirements of this
chapter.
501.3 CONSTRUCTION DOCUMENTS
Copies of design drawings, typical details, and specifications for all structural concrete construction
shall bear the seal of a licensed design professional. These drawings, details, and specifications shall
show:
1. Name and date of issue of code and supplement to which design conforms;
2. Live load and other loads used in design;
3. The specified compressive strength of concrete at the stated ages or stages of construction for
which each concrete element is designed.
4. The specified strength or grade of reinforcement.
5. The size and location of structural elements, reinforcement and anchors.
6. Provision for dimensional changes resulting from creep, shrinkage and temperature.
7. The magnitude and location of prestressing forces.
8. Anchorage length of reinforcement and location and length of lap splices.
9. Type and location of mechanical and welded splices of reinforcement.
10.Details and location of contraction or isolation joints specified for plain concrete.
11.Minimum concrete compressive strength at time of posttensioning.
12.Stressing sequence for posttensioning tendons.
13.For structures assigned to Seismic Design Category D, E or F, a statement if slab on grade is
designed as a structural diaphragm
14.Calculations pertinent to design shall be filed with the drawings when required by the building
official. Analyses and designs using computer programs shall be permitted provided design
assumptions, user input, and computer-generated output are submitted. Model analysis shall be
permitted to supplement calculations.
501.4 SPECIAL INSPECTION
The special inspection of concrete elements of buildings and structures and concreting operations shall
be as required by Chapter 9.
SECTION 502 SPECIFICATIONS FOR TESTS AND MATERIALS
502.1 GENERAL
Materials used to produce concrete, concrete itself and testing thereof shall comply with the applicable
sections in this chapter.
SECTION 503 DURABILITY REQUIREMENTS
All rights reserved
211 / 496
503.1 WATER-CEMENTITIOUS MATERIALS RATIO
The maximum water-cementitious materials ratios are specified in Section 503.
503.1.1
The value of f´c shall be the greatest of the values required by (a) this code, (b) for durability in
Section 503, and (c) for structural strength requirements and shall apply for mixture
proportioning in Section 504.3 and for evaluation and acceptance of concrete in Section 504.6.
Concrete mixtures shall be proportioned to comply with the maximum water-cementitious
material ratio (w/cm) and other requirements based on the exposure class assigned to the
concrete structural member. All cementitious materials specified in Section 511.2.1 and the
combinations of these materials shall be included in calculating the w/cm of the concrete
mixture.
503.2 EXPOSURE CATEGORIES AND CLASSES
Concrete shall be assigned to exposure classes in accordance with this section, based on:
1. Exposure to freezing and thawing in a moist condition or deicer chemicals;
2. Exposure to sulfates in water or soil;
3. Exposure to water where the concrete is intended to have low permeability; and
4. Exposure to chlorides from deicing chemicals, salt, saltwater, brackish water, seawater or spray
from these sources, where the concrete has steel reinforcement.
503.2.1
The licensed design professional shall assign exposure classes based on the severity of the
anticipated exposure of structural concrete members for each exposure category according to
Table 503.2.1-1.
TABLE 503.2.1-1 EXPOSURE CATEGORIES AND CLASSES
Category
F
Freezing
and thawing
S
Sulfate
P
Requiring low
permeability
C
Corrosion protection
of reinforcement
Condition
Severity
Not applicable
Class
Moderate
F1
Severe
F2
Very severe
F3
Not applicable
S0
SO4 < 0.10
Moderate
S1
0.10 ≤ SO4 < 0.20
Severe
Very severe
S2
0.20 ≤ SO4 ≤ 2.00
Not applicable
P0
Required
P1
Not applicable
C0
Moderate
C1
Severe
C2
F0
S3
Concrete not exposed to freezing- and-thawing cycles
Concrete exposed to freezing-and- thawing cycles and
occasional exposure to moisture
Concrete exposed to freezing-and- thawing cycles and in
continuous contact with moisture
Concrete exposed to freezing-and- thawing and in continuous
contact with moisture and exposed to deicing chemicals
Water-soluble sulfate (SO4) Dissolved sulfate (SO4) in
in soil, percent by weight
water, ppm
SO4 < 150
150 ≤ SO4 <1500
Seawater
1500 ≤ SO4 ≤ 10,000
SO4 > 2.00
SO4 > 10,000
In contact with water where low permeability is not
required
In contact with water where low permeability is required.
Concrete dry or protected from moisture
Concrete exposed to moisture but not to external sources of
chlorides
Concrete exposed to moisture and an external source of
chlorides from deicing chemicals, salt, brackish water,
seawater, or spray from these sources
503.3 CONCRETE PROPERTIES
All rights reserved
212 / 496
Concrete mixtures shall conform to the most restrictive maximum water-cementitious materials ratios
and minimum specified concrete compressive strength requirements of this section, based on the
exposure classes assigned in Section 503.2.
Exception: For occupancies and appurtenances thereto in Group R occupancies that are in
buildings less than four stories above grade plane, normal-weight aggregate concrete is
permitted to comply with the requirements of Table 503.3-1.
TABLE 503.3-1 MINIMUM SPECIFIED COMPRESSIVE STRENGTH (f΄c)
TYPE OR LOCATION OF CONCRETE CONSTRUCTION
c
Basement walls and foundations not exposed to the weather
Basement slabs and interior slabs on grade, except garage floor slabs
c
Basement walls , foundation walls, exterior walls and other vertical
concrete surfaces exposed to the weather
Driveways, curbs, walks, patios, porches, carport slabs, steps and
other flatwork exposed to the weather, and garage floor slabs
MINIMUM SPECIFIED COMPRESSIVE
STRENGTH ( f´c at 28 days, MPa)
Negligible
Moderate
Severe
exposure
exposure
exposure
a
17
17
17
a
17
17
17
b
b
17
20
20
b,d
17
20
b,d
24
a. Concrete in these locations that can be subjected to freezing and thawing during construction shall
be of air-entrained concrete in accordance with Section 503.2.1.
b. Concrete shall be air entrained in accordance with Section 503.4.1.
c. Structural plain concrete basement walls are exempt from the requirements for exposure conditions
of Section 503.3 (see Section 507.6.5).
d. For garage floor slabs where a steel trowel finish is used, the total air content required by Section
503.4.1 is permitted to be reduced to not less than 3 percent, provided the minimum specified
compressive strength of the concrete is increased to 275 KPa.
503.3.1
Based on the exposure classes assigned from Table 503.2.1-1, concrete mixtures shall comply
with the most restrictive requirements according to Table 503.3.1-1.
TABLE 503.3.1-1 REQUIREMENTS FOR CONCRETE BY EXPOSURE CLASS
Exposure Max.a Min.
w/cm f´c , MPa
Class
Additional minimum requirements
Limits on
cementitious
materials
N/A
N/A
N/A
Table 503.4.2.1-1
Air content
F0
F1
F2
N/A
0.45
0.45
17
31
31
F3
0.45
31
N/A
Table 503.4.1.1-1
Table 503.4.1.1-1
Table 503.4.1.1-1
b
Cementitious materials —types
ASTM C150
ASTM C595
S0
N/A
17
No Type restriction
No Type restriction
0.50
28
II
c
S1
S2
0.45
31
V
IP(MS), IS (<70)
(MS)
IP (HS) IS (<70)
(HS)
d
e
S3
All rights reserved
0.45
31
V + pozzolan or slag
IP (HS) + pozzolan or
e
slag or IS (<70)
(HS) + pozzolan
or
e
slag
ASTM
C1157
No Type
restriction
Calcium chloride
admixture
MS
No restriction
HS
Not permitted
HS +
pozzolan
or
e
slag
Not permitted
No restriction
213 / 496
P0
P1
C0
C1
C2
N/A
0.50
N/A
N/A
0.40
17
28
17
17
35
None
None
Maximum water-soluble
chloride ion (Cl–) content in
concrete, percent by
weight
f
of cement
Reinforced Prestressed
concrete
concrete
1.00
0.06
0.30
0.06
0.15
0.06
Related provisions
None
506.7.6
503.4 FREEZING AND THAWING EXPOSURE
Concrete that will be exposed to freezing and thawing, in the presence of moisture, with or without
deicing chemicals being present, shall comply with Sections 503.4.1 and 503.4.2.
503.4.1 AIR ENTRAINMENT
Concrete exposed to freezing and thawing while moist shall be air entrained in accordance Section
503.4.1.1.
503.4.1.1
Normalweight and lightweight concrete subject to Exposure Classes F1, F2, or F3 shall be airentrained with air content indicated in Table 503.4.1.1-1. Tolerance on air content as
delivered shall be ±1.5 percent. For f´c greater than 35 MPa, reduction of air content
indicated in Table 503.4.1.1-1 by 1.0 percent shall be permitted.
TABLE 503.4.1.1-1 TOTAL AIR CONTENT FOR CONCRETE EXPOSED TO CYCLES OF FREEZING AND
THAWING
Nominal maximuma aggregate size,
mm
9.5
12.5
19.0
25.0
37.5
b
50
b
75
Exposure Class F1
6
5.5
5
4.5
4.5
4
3.5
Air content, percent
Exposure Classes F2 and F3
7.5
7
6
6
5.5
5
4.5
a: See ASTM C33 for tolerance on oversize for various nominal maximum size designations.
b: Air contents apply to total mixture. When testing concretes, however, aggregate particles larger
than 40 mm are removed by sieving and air content is measured on the sieved fraction (tolerance
on air content as delivered applies to this value). Air content of total mixture is computed from
value measured on the sieved fraction passing the 40 mm sieve in accordance with ASTM C231.
503.4.2 DEICING CHEMICALS
For concrete exposed to freezing and thawing in the presence of moisture and deicing chemicals,
the maximum weight of fly ash, other pozzolans, silica fume or slag that is included in the
concrete shall not exceed the percentages of the total weight of cementitious materials
permitted by Section 503.4.2.1.
503.4.2.1
All rights reserved
214 / 496
The quantity of pozzolans, including fly ash and silica fume, and slag in concrete subject to
Exposure Class F3, shall not exceed the limits in Table 503.4.2.1-1.
TABLE 503.4.2.1-1 REQUIREMENTS FOR CONCRETE SUBJECT TO EXPOSURE CLASS F3
Cementitious materials
Fly ash or other pozzolans conforming to ASTM C618
Slag conforming to ASTM C989
Silica fume conforming to ASTM C1240
Total of fly ash or other pozzolans, slag, and silica fume
Total of fly ash or other pozzolans and silica fume
Maximum percent of total cementitious materials by
a
weight
25
50
10
b
50
b
35
a: The total cementitious material also includes ASTM C150, C595, C845, and C1157 cement.
b: Fly ash or other pozzolans and silica fume shall constitute no more than 25 and 10 percent,
respectively, of the total weight of the cementitious materials.
The maximum percentages above shall include:
(a) Fly ash or other pozzolans in Type IP, blended cement, ASTM C595, or ASTM C1157;
(b) Slag used in the manufacture of an IS blended cement, ASTM C595, or ASTM C1157;
(c) Silica fume, ASTM C1240, present in a blended cement.
503.5 ALTERNATIVE CEMENTITIOUS MATERIALS FOR SULFATE EXPOSURE
Alternative combinations of cementitious materials for use in sulfate-resistant concrete to those listed
in Table 503.3.1-1 shall be permitted in accordance with this section.
TABLE 503.5-1 REQUIREMENTS FOR ESTABLISHING SUITABILITY OF CEMENTITIOUS MATERIALS
COMBINATIONS EXPOSED TO WATER-SOLUBLE SULFATE
Exposure
Class
Maximum expansion when tested using ASTM C1012
At 6 months
S1
0.10 percent
S2
0.05 percent
S3
At 12 months
0.10 percent
At 18 months
a
0.10 percent
a: The 12-month expansion limit applies only when the measured expansion exceeds the 6-month
maximum expansion limit.
SECTION 504 CONCRETE QUALITY, MIXING AND PLACING
Concrete proportions shall be determined in accordance with the provisions of Section 504.2.
504.1 GENERAL
504.1.1
Concrete shall be proportioned to provide an average compressive strengthfć, as prescribed in
504.3.2 and shall satisfy the durability criteria of Section 503. Concrete shall be produced to
minimize the frequency of strength tests belowfć, as prescribed in 504.6.3.3. For concrete
designed and constructed in accordance with the Code, fć shall not be less than 17 MPa.
504.1.2
Requirements for f´c shall be based on tests of cylinders made and tested as prescribed in
504.6.3.
All rights reserved
215 / 496
504.1.3
Unless otherwise specified, f´c shall be based on 28-day tests. If other than 28 days, test age for
f´c shall be as indicated in design drawings or specifications.
504.1.4
Where design criteria in 512.6.1 and 516.2.4 provide for use of a splitting tensile strength value
of concrete, laboratory tests shall be made in accordance with ASTM C330 to establish a value of
f´ct corresponding to f´c.
504.1.5
Splitting tensile strength tests shall not be used as a basis for field acceptance of concrete.
504.2 SELECTION OF CONCRETE PROPORTIONS
504.2.1
Proportions of materials for concrete shall be established to:
(a) Provide workability and consistency to permit concrete to be worked readily into forms and
around reinforcement under conditions of placement to be employed, without segregation or
excessive bleeding;
(b) Meet requirements for applicable exposure categories of Section 503;
(c) Conform to strength test requirements of 504.6.
504.2.2
Where different materials are to be used for different portions of proposed Work, each
combination shall be evaluated.
504.2.3
Concrete proportions shall be established in accordance with 504.3 or, alternatively, 504.4, and
shall meet applicable requirements of Section 503.
504.3 PROPORTIONING ON THE BASIS OF FIELD EXPERIENCE AND / OR TRIAL MIXTURES
Concrete proportioning determined on the basis of field experience and/or trial mixtures shall be done
in accordance with this section.
504.3.1 SAMPLE STANDARD DEVIATION
504.3.1.1
Where a concrete production facility has strength test records not more than 12 months old,
a sample standard deviation, ss, shall be established. Test records from which ss is
calculated:
(a) Shall represent materials, quality control procedures, and conditions similar to those
expected and changes in materials and proportions within the test records shall not
have been more restricted than those for proposed Work;
(b) Shall represent concrete produced to meet a specified compressive strength or strengths
within 7 MPa of f´c ;
(c) Shall consist of at least 30 consecutive tests or two groups of consecutive tests totaling
at least 30 tests as defined in 504.6.2.4, except as provided in 504.3.1.2.
504.3.1.2
Where a concrete production facility does not have strength test records meeting
requirements of 504.3.1.1(c), but does have test records not more than 12 months old
based on 15 to 29 consecutive tests, a sample standard deviation ss shall be established as
the product of the calculated sample standard deviation and modification factor of Table
All rights reserved
216 / 496
504.3.1.2-1. To be acceptable, test records shall meet requirements (a) and (b) of 504.3.1.1,
and represent only a single record of consecutive tests that span a period of not less than 45
calendar days.
TABLE 504.3.1.2-1 MODIFICATION FACTOR FOR SAMPLE STANDARD DEVIATION WHEN LESS THAN 30
TESTS ARE AVAILABLE
a
No. of tests
Less than 15
15
20
25
30 or more
Modification factor for sample standard deviation
Use Table 504.3.2.2-1
1.16
1.08
1.03
1.00
b
a: Interpolate for intermediate numbers of tests.
b: Modified sample standard deviation, ss, to be used to determined required average strength, f´cr ,
from 504.3.2.1
504.3.2 REQUIRED AVERAGE STRENGTH
504.3.2.1
Required average compressive strength f´cr used as the basis for selection of concrete
proportions shall be determined from Table 504.3.2.1 using the sample standard deviation,
ss, calculated in accordance with 504.3.1.1 or 504.3.1.2.
TABLE 504.3.2.1-1 REQUIRED AVERAGE COMPRESSIVE STRENGTH WHEN DATA ARE AVAILABLE TO
ESTABLISH A SAMPLE STANDARD DEVIATION
Specified compressive strength, MPa
Required average compressive strength, MPa
f´c ≤ 35
Use the larger value computed from Eq. (5-1) and (5-2)
f´cr = f´c + 1.34ss (5-1)
f´cr = f´c + 2.33ss – 3.5 (5-2)
f´c > 35
Use the larger value computed from Eq. (5-1) and (5-3)
f´cr = f´c + 1.34ss (5-1)
f´cr = 0.90 f´c + 2.33ss (5-2)
504.3.2.2
When a concrete production facility does not have field strength test records for calculation
of ss meeting requirements of 504.3.1.1 or 504.3.1.2, f´cr shall be determined from Table
504.3.2.2 and documentation of average strength shall be in accordance with requirements
of 504.3.3.
TABLE 504.3.2.2-1 REQUIRED AVERAGE COMPRESSIVE STRENGTH WHEN DATA ARE NOT AVAILABLE
TO ESTABLISH A SAMPLE
Specified compressive strength, MPa
f´c < 21
3000 ≤ f´c ≤ 35
f´c > 35
Required average compressive strength, MPa
f´cr= f´c + 7.0
f´cr= f´c + 8.3
f´cr= 1.10 f´c + 5.0
504.3.3 DOCUMENTATION OF AVERAGE COMPRESSIVE STRENGTH
All rights reserved
217 / 496
Documentation that proposed concrete proportions will produce an average compressive
strength equal to or greater than required average compressive strength f´cr (see 504.3.2) shall
consist of a field strength test record, several strength test records, or trial mixtures.
504.3.3.1
When test records in accordance with 504.3.1.1 or 504.3.1.2 are used to demonstrate that
proposed concrete proportions will produce f´cr (see 504.3.2), such records shall represent
materials and conditions similar to those expected. Changes in materials, conditions, and
proportions within the test records shall not have been more restricted than those for
proposed Work. For the purpose of documenting average strength potential, test records
consisting of less than 30 but not less than 10 consecutive tests are acceptable provided test
records encompass a period of time not less than 45 days. Required concrete proportions
shall be permitted to be established by interpolation between the strengths and proportions
of two or more test records, each of which meets other requirements of this section.
504.3.3.2
When an acceptable record of field test results is not available, concrete proportions
established from trial mixtures meeting the following requirements shall be permitted:
(a) Materials shall be those for proposed Work;
(b) Trial mixtures with a range of proportions that will produce a range of compressive
strengths encompassing f´cr and meet the durability requirements of Section 503;
(c) Trial mixtures shall have slumps within the range specified for the proposed Work; for airentrained concrete, air content shall be within the tolerance specified for the proposed
Work;
(d) For each trial mixture, at least two 150 by 300 mm or three 100 by 200 mm cylinders
shall be made and cured in accordance with ASTM C192M. Cylinders shall be tested at
28 days or at test age designated for f´c ;
(e) The compressive strength results, at designated test age, from the trial mixtures shall be
used to establish the composition of the concrete mixture proposed for the Work. The
proposedconcrete mixture shall achieve an average compressive strength as required in
504.3.2 and satisfy the applicable durability criteria of Section 503.
504.4 PROPORTIONING WITHOUT FIELD EXPERIENCE OR TRIAL MIXTURES
Concrete proportioning determined without field experience or trial mixtures shall be done in
accordance with this section.
504.4.1
If data required by 504.3 are not available, concrete proportions shall be based upon other
experience or information, if approved by the licensed design professional.
The required average compressive strength f´cr of concrete produced with materials similar to
those
proposed for use shall be at least 8.3 MPa greater than f´c. This alternative shall not be used if f´c
is greater than 35 MPa.
504.4.2
Concrete proportioned by this section shall conform to the durability requirements of Section
503 and to compressive strength test criteria of 504.6.
504.5 AVERAGE STRENGTH REDUCTION
As data become available during construction, it shall be permitted to reduce the amount by which the
required average concrete strength, f´cr, must exceed f´c, provided:
All rights reserved
218 / 496
(a) Thirty or more test results are available and average of test results exceeds that required by
504.3.2.1, using a sample standard deviation calculated in accordance with 504.3.1.1; or
(b) Fifteen to 29 test results are available and average of test results exceeds that required by
504.3.2.1 using a sample standard deviation calculated in accordance with 504.3.1.2; and
(c) Requirements for exposure categories of Section 503 are met.
504.6 EVALUATION AND ACCEPTANCE OF CONCRETE
The criteria for evaluation and acceptance of concrete shall be as specified in Sections 504.6.2 through
504.6.5.
504.6.1 QUALIFIED TECHNICIANS
Concrete shall be tested in accordance with the requirements in Sections 504.6.2 through
504.6.5. Qualified field testing technicians shall perform tests on fresh concrete at the job site,
prepare specimens required for curing under field conditions, prepare specimens required for
testing in the laboratory and record the temperature of the fresh concrete when preparing
specimens for strength tests. Qualified laboratory technicians shall perform all required
laboratory tests.
504.6.2 FREQUENCY OF TESTING
The frequency of conducting strength tests of concrete and the minimum number of tests shall
be as specified in Section 504.6.2.
Exception: When the total volume of a given class of concrete is less than 40 m3, strength tests
are not required when evidence of satisfactory strength is submitted to and approved by the
building official.
504.6.2.1
Samples for strength tests of each class of concrete placed each day shall be taken not less
than once a day, nor less than once for each 110 m3 of concrete, nor less than once for each
460 m2 of surface area for slabs or walls.
504.6.2.2
On a given project, if total volume of concrete is such that frequency of testing required by
504.6.2.1 would provide less than five strength tests for a given class of concrete, tests shall
be made from at least five randomly selected batches or from each batch if fewer than five
batches are used.
504.6.2.3
When total quantity of a given class of concrete is less than 38 m3, strength tests are not
required when evidence of satisfactory strength is submitted to and approved by the
building official.
504.6.2.4
A strength test shall be the average of the strengths of at least two 150 by 300 mm cylinders
or at least three 100 by 200 mm cylinders made from the same sample of concrete and
tested at 28 days or at test age designated for determination of f´c.
504.6.3 STRENGTH TEST SPECIMENTS
Specimens prepared for acceptance testing of concrete in accordance with Section 504.6.2 and
strength test acceptance criteria shall comply with the provisions of Section 504.6.3.
504.6.3.1
Samples for strength tests shall be taken in accordance with ASTM C172.
All rights reserved
219 / 496
504.6.3.2
Cylinders for strength tests shall be molded and standard-cured in accordance with ASTM
C31M and tested in accordance with ASTM C39M. Cylinders shall be 100 by 200 mm or 150
by 300 mm.
504.6.3.3
Strength level of an individual class of concrete shall be considered satisfactory if both of the
following requirements are met:
(a) Every arithmetic average of any three consecutive strength tests (see 504.6.2.4) equals or
exceeds f´c ;
(b) No strength test (see 504.6.2.4) falls below f´c by more than 500 psi when f´c is 35 MPa or
less; or by more than 0.10 f´c when f´c is more than 35 MPa.
504.6.3.4
If either of the requirements of 504.6.3.3 is not met, steps shall be taken to increase the
average of subsequent strength test results. Requirements of 504.6.5 shall be observed if
requirement of 5.6.3.3(b) is not met.
504.6.4 FIELD-CURED SPECIMENS
Where required by the building official to determine adequacy of curing and protection of
concrete in the structure, specimens shall be prepared, cured, tested and test results evaluated
for acceptance in accordance with Section 504.6.4.
504.6.4.1
If required by the building official, results of strength tests of cylinders cured under field
conditions shall be provided.
504.6.4.2
Field-cured cylinders shall be cured under field conditions in accordance with ASTM C31M.
504.6.4.3
Field-cured test cylinders shall be molded at the same time and from the same samples as
laboratory-cured test cylinders.
504.6.4.4
Procedures for protecting and curing concrete shall be improved when strength of
fieldcured cylinders at test age designated for determination of f´c is less than 85 percent of
that of companion laboratory-cured cylinders. The 85 percent limitation shall not apply if
field-cured strength exceeds f´c by more than 3.5 MPa.
504.6.5 LOW-STRENGTH TEST RESULT
Where any strength test (see Section 504.6.2.4) falls below the specified value of , f´c the
provisions of Section 504.6.5, shall apply.
504.6.5.1
If any strength test (see 504.6.2.4) of laboratory-cured cylinders falls below f´c by more than
the values given in 504.6.3.3(b) or if tests of field-cured cylinders indicate deficiencies in
protection and curing (see 504.6.4.4), steps shall be taken to ensure that loadcarrying
capacity of the structure is not jeopardized.
504.6.5.2
All rights reserved
220 / 496
If the likelihood of low-strength concrete is confirmed and calculations indicate that loadcarrying capacity is significantly reduced, tests of cores drilled from the area in question in
accordance with ASTM C42M shall be permitted. In such cases, three cores shall be taken for
each strength test that falls below the values given in 504.6.3.3(b).
504.6.5.3
Cores shall be obtained, moisture conditioned by storage in watertight bags or containers,
transported to the laboratory, and tested in accordance with ASTM C42M. Cores shall be
tested no earlier than 48 hours and not later than 7 days after coring unless approved by the
licensed design professional. The specifier of tests referenced in ASTM C42M shall be the
licensed design professional.
504.6.5.4
Concrete in an area represented by core tests shall be considered structurally adequate if
the average of three cores is equal to at least 85 percent of f´cr and if no single core is less
than 75 percent of f´c. Additional testing of cores extracted from locations represented by
erratic core strength results shall be permitted.
504.6.5.5
If criteria of 504.6.5.4 are not met and if the structural adequacy remains in doubt, the
responsible authority shall be permitted to order a strength evaluation in accordance with
Section 915 for the questionable portion of the structure, or take other appropriate action.
504.7 PREPARATION OF EQUIPMENT AND PLACE OF DEPOSIT
Prior to concrete being placed, the space to receive the concrete and the equipment used to deposit it
shall comply with Section 504.7.
504.7.1
Preparation before concrete placement shall include the following:
(a) All equipment for mixing and transporting concrete shall be clean;
(b) All debris and ice shall be removed from spaces to be occupied by concrete;
(c) Forms shall be properly coated;
(d) Masonry filler units that will be in contact with concrete shall be well drenched;
(e) Reinforcement shall be thoroughly clean of ice or other deleterious coatings;
(f) Water shall be removed from place of deposit before concrete is placed unless a tremie is to
be used or unless otherwise permitted by the building official;
(g) All laitance and other unsound material shall be removed before additional concrete is placed
against hardened concrete.
504.8 MIXING
Mixing of concrete shall be performed in accordance with this section.
504.8.1
All concrete shall be mixed until there is a uniform distribution of materials and shall be
discharged completely before mixer is recharged.
504.8.2
Ready-mixed concrete shall be mixed and delivered in accordance with requirements of ASTM
C94M or C685M.
504.8.3
All rights reserved
221 / 496
Job-mixed concrete shall be mixed in accordance with (a) through (e):
(a) Mixing shall be done in a batch mixer of approved type;
(b) Mixer shall be rotated at a speed recommended by the manufacturer;
(c) Mixing shall be continued for at least 1-1/2 minutes after all materials are in the drum, unless
a shorter time is shown to be satisfactory by the mixing uniformity tests of ASTM C94M;
(d) Materials handling, batching, and mixing shall conform to applicable provisions of ASTM
C94M;
(e) A detailed record shall be kept to identify:
(1) number of batches produced;
(2) proportions of materials used;
(3) approximate location of final deposit in structure;
(4) time and date of mixing and placing.
504.9 CONVEYING
The method and equipment for conveying concrete to the place of deposit shall comply with Section
504.9.
504.9.1
Concrete shall be conveyed from mixer to place of final deposit by methods that will prevent
separation or loss of materials.
504.9.2
Conveying equipment shall be capable of providing a supply of concrete at site of placement
without separation of ingredients and without interruptions sufficient to permit loss of plasticity
between successive increments.
504.10 DEPOSITING
The depositing of concrete shall comply with the provisions of Section 504.10.
504.10.1
Concrete shall be deposited as nearly as practical in its final position to avoid segregation due to
rehandling or flowing.
504.10.2
Concreting shall be carried on at such a rate that concrete is at all times plastic and flows readily
into spaces between reinforcement.
504.10.3
Concrete that has partially hardened or been contaminated by foreign materials shall not be
deposited in the structure.
504.10.4
Retempered concrete or concrete that has been remixed after initial set shall not be used unless
approved by the licensed design professional.
504.10.5
After concreting is started, it shall be carried on as a continuous operation until placing of a
panel or section, as defined by its boundaries or predetermined joints, is completed except as
permitted or prohibited by 505.4.
504.10.6
Top surfaces of vertically formed lifts shall be generally level.
All rights reserved
222 / 496
504.10.7
When construction joints are required, joints shall be made in accordance with 505.4.
504.10.8
All concrete shall be thoroughly consolidated by suitable means during placement and shall be
thoroughly worked around reinforcement and embedded fixtures and into corners of forms.
504.11 CURING
The length of time, temperature and moisture conditions for curing of concrete shall be in accordance
with this section.
504.11.1
Concrete (other than high-early-strength) shall be maintained above 10 °C and in a moist
condition for at least the first 7 days after placement, except when cured in accordance with
504.11.3.
504.11.2
High-early-strength concrete shall be maintained above 10 °C and in a moist condition for at
least the first 3 days, except when cured in accordance with 504.11.3.
504.11.3 ACCELERATED CURING
504.11.3.1
Curing by high-pressure steam, steam at atmospheric pressure, heat and moisture, or other
accepted processes, shall be permitted to accelerate strength gain and reduce time of
curing.
504.11.3.2
Accelerated curing shall provide a compressive strength of the concrete at the load stage
considered at least equal to required design strength at that load stage.
504.11.3.3
Curing process shall be such as to produce concrete with a durability at least equivalent to
the curing method of 504.11.1 or 504.11.2.
504.11.4
When required by the licensed design professional, supplementary strength tests in accordance
with 504.6.4 shall be performed to assure that curing is satisfactory.
504.12 COLD WEATHER REQUIREMENTS
Concrete to be placed during freezing or near-freezing weather shall comply with the requirements of
this section.
504.12.1
Adequate equipment shall be provided for heating concrete materials and protecting concrete
during freezing or near-freezing weather.
504.12.2
All concrete materials and all reinforcement, forms, fillers, and ground with which concrete is to
come in contact shall be free from frost.
504.12.3
Frozen materials or materials containing ice shall not be used.
All rights reserved
223 / 496
504.13 HOT WEATHER REQUIREMENTS
During hot weather, proper attention shall be given to ingredients, production methods, handling,
placing, protection, and curing to prevent excessive concrete temperatures or water evaporation that
could impair required strength or serviceability of the member or structure.
SECTION 505 FORMWORK, EMBEDDED PIPES AND CONSTRUCTION JOINTS
505.1 FORMWORK
The design, fabrication and erection of forms shall comply with this section.
505.1.1
Forms shall result in a final structure that conforms to shapes, lines, and dimensions of the
members as required by the design drawings and specifications.
505.1.2
Forms shall be substantial and sufficiently tight to prevent leakage of mortar.
505.1.3
Forms shall be properly braced or tied together to maintain position and shape.
505.1.4
Forms and their supports shall be designed so as not to damage previously placed structure.
505.1.5
Design of formwork shall include consideration of the following factors:
(a) Rate and method of placing concrete;
(b) Construction loads, including vertical, horizontal, and impact loads;
(c) Special form requirements for construction of shells, folded plates, domes, architectural
concrete, or similar types of elements.
505.1.6
Forms for prestressed concrete members shall be designed and constructed to permit
movement of the member without damage during application of prestressing force.
505.2 REMOVAL OF FORMS, SHORES AND RESHORES
The removal of forms and shores, including from slabs and beams (except where cast on the ground),
and the installation of reshores shall comply with this section.
505.2.1 REMOVAL OF FORMS
Forms shall be removed in such a manner as not to impair safety and serviceability of the
structure.
Concrete exposed by form removal shall have sufficient strength not to be damaged by removal
operation.
505.2.2 REMOVAL OF SHORES AND RESHORING
The provisions of 505.2.2.1 through 505.2.2.3 shall apply to slabs and beams except where cast
on the ground.
505.2.2.1
All rights reserved
224 / 496
Before starting construction, the contractor shall develop a procedure and schedule for
removal of shores and installation of reshores and for calculating the loads transferred to
the structure during the process.
(a) The structural analysis and concrete strength data used in planning and implementing
form removal and shoring shall be furnished by the contractor to the building official
when so requested;
(b) No construction loads shall be supported on, nor any shoring removed from, any part of
the structure under construction except when that portion of the structure in
combination with remaining forming and shoring system has sufficient strength to
support safely its weight and loads placed thereon;
(c) Sufficient strength shall be demonstrated by structural analysis considering proposed
loads, strength of forming and shoring system, and concrete strength data. Concrete
strength data shall be based on tests of field-cured cylinders or, when approved by the
building official, on other procedures to evaluate concrete strength.
505.2.2.2
No construction loads exceeding the combination of superimposed dead load plus specified
live load shall be supported on any unshored portion of the structure under construction,
unless analysis indicates adequate strength to support such additional loads.
505.2.2.3
Form supports for prestressed concrete members shall not be removed until sufficient
prestressing has been applied to enable prestressed members to carry their dead load and
anticipated construction loads.
505.3 CONDUITS AND PIPES EMBEDDED IN CONCRETE
Conduits, pipes and sleeves of any material not harmful to concrete and within the limitations of this
section, are permitted to be embedded in concrete with approval of the registered design professional.
Any aluminum embedments in structural concrete shall be coated or covered to prevent aluminumconcrete reaction or electrolytic action between aluminum and steel.
505.3.1
Embedments of any material not harmful to concrete and within limitations of 505.3 shall be
permitted in concrete with approval of the licensed design professional, provided they are not
considered to replace structurally the displaced concrete, except as provided in 505.3.6.
505.3.2
Conduits, pipes, and sleeves passing through a slab, wall, or beam shall not impair significantly
the strength of the construction.
505.3.3
Conduits and pipes, with their fittings, embedded within a column shall not displace more than 4
percent of the area of cross section on which strength is calculated or which is required for fire
protection.
505.3.4
Except when drawings for conduits and pipes are approved by the licensed design professional,
conduits and pipes embedded within a slab, wall, or beam (other than those merely passing
through) shall satisfy 505.3.5.1 through 505.3.5.3.
505.3.4.1
They shall not be larger in outside dimension than 1/3 the overall thickness of slab, wall, or
beam in which they are embedded.
All rights reserved
225 / 496
505.3.4.2
They shall not be spaced closer than three diameters or widths on center.
505.3.4.3
They shall not impair significantly the strength of the construction.
505.3.5
Conduits, pipes, and sleeves shall be permitted to be considered as replacing structurally in
compression the displaced concrete provided in 505.3.6.1 through 505.3.6.3.
505.3.5.1
They are not exposed to rusting or other deterioration.
505.3.5.2
They are of uncoated or galvanized iron or steel not thinner than standard Schedule 40 steel
pipe.
505.3.5.3
They have a nominal inside diameter not over 50 mm and are spaced not less than three
diameters on centers.
505.3.6
Pipes and fittings shall be designed to resist effects of the material, pressure, and temperature
to which they will be subjected.
505.3.7
No liquid, gas, or vapor, except water not exceeding 32 °C nor 0.35 MPa pressure, shall be
placed in the pipes until the concrete has attained its design strength.
505.3.8
In solid slabs, piping, unless it is for radiant heating or snow melting, shall be placed between top
and bottom reinforcement.
505.3.9
Specified concrete cover for pipes, conduits, and fittings shall not be less than 40 mm for
concrete exposed to earth or weather, nor less than 20 mm for concrete not exposed to weather
or in contact with ground.
505.3.10
Reinforcement with an area not less than 0.002 times area of concrete section shall be provided
normal to piping.
505.3.11
Piping and conduit shall be so fabricated and installed that cutting, bending, or displacement of
reinforcement from its proper location will not be required.
505.4 CONSTRUCTION JOINTS
Construction joints, including their location, shall comply with the provisions of this section.
505.4.1
Surface of concrete construction joints shall be cleaned and laitance removed.
All rights reserved
226 / 496
505.4.2
Immediately before new concrete is placed, all construction joints shall be wetted and standing
water removed.
505.4.3
Construction joints shall be so made and located as not to impair the strength of the
structure.Provision shall be made for transfer of shear and other forces through construction
joints.
505.4.4
Construction joints in floors shall be located within the middle third of spans of slabs, beams,
and girders.
505.4.5
Construction joints in girders shall be offset a minimum distance of two times the width of
intersecting beams.
505.4.6
Beams, girders, or slabs supported by columns or walls shall not be cast or erected until concrete
in the vertical support members is no longer plastic.
505.4.7
Beams, girders, haunches, drop panels, shear caps, and capitals shall be placed monolithically as
part of a slab system, unless otherwise shown in design drawings or specifications.
SECTION 506 DETAILS OF REINFORCEMENT
506.1 HOOKS
Standard hooks on reinforcing bars used in concrete construction shall comply with this section.
506.1.1
180-degree bend plus 4db extension, but not less than 65 mm at free end of bar.
506.1.2
90-degree bend plus 12db extension at free end of bar.
506.1.3
For stirrup and tie hooks
(a) No. 16 bar and smaller, 90-degree bend plus 6db extension at free end of bar; or
(b) No. 19, No. 22, and No. 25 bar, 90-degree bend plus 12db extension at free end of bar; or
(c) No. 25 bar and smaller, 135-degree bend plus 6db extension at free end of bar.
506.1.4
Seismic hooks as defined in Chapter 2.
506.2 MINIMUM BEND DIAMETERS
Minimum reinforcement bend diameters utilized in concrete construction shall comply with this
section.
All rights reserved
227 / 496
506.2.1
Diameter of bend measured on the inside of the bar, other than for stirrups and ties in sizes No.
10 through No. 16, shall not be less than the values in Table 506.2.3-1.
506.2.2
Inside diameter of bend for stirrups and ties shall not be less than 4db for No. 16 bar and
smaller. For bars larger than No. 16, diameter of bend shall be in accordance with Table 506.2.31.
506.2.3
Inside diameter of bend in welded wire reinforcement for stirrups and ties shall not be less than
4db for deformed wire larger than MD40 and 2db for all other wires. Bends with inside diameter
of less than 8db shall not be less than 4db from nearest welded intersection.
TABLE 506.2.3-1 MINIMUM DIAMETERS OF BEND
Bar size
No. 10 through No. 25
No. 29, No. 32, and No. 36
No. 43 and No. 57
Minimum diameter
6db
8db
10db
506.3 BENDING
The bending of reinforcement shall comply with this section.
506.3.1
All reinforcement shall be bent cold, unless otherwise permitted by the licensed design
professional.
506.3.2
Reinforcement partially embedded in concrete shall not be field bent, except as shown on the
design drawings or permitted by the licensed design professional.
506.4 SURFACE CONDITIONS OF REINFORCEMENT
The surface conditions of reinforcement shall comply with the provisions of this section.
506.4.1
At the time concrete is placed, reinforcement shall be free from mud, oil, or other nonmetallic
coatings that decrease bond.
506.4.2
Except for prestressing steel, steel reinforcement with rust, mill scale, or a combination of both
shall be considered satisfactory, provided the minimum dimensions (including height of
deformations) and weight of a hand-wire-brushed test specimen comply with applicable ASTM
specifications referenced in Section 511.5.
506.5 PLACING REINFORCEMENT
All rights reserved
228 / 496
The placement of reinforcement, including tolerances on depth and cover, shall comply with the
provisions of this section. Reinforcement shall be accurately placed and adequately supported before
concrete is placed.
Welding of crossing bars shall not be permitted for assembly of reinforcement unless authorized by the
licensed design professional.
506.5.1
Reinforcement, including tendons, and posttensioning ducts shall be accurately placed and
adequately supported before concrete is placed, and shall be secured against displacement
within tolerances permitted in 506.5.2.
506.5.2
Unless otherwise specified by the licensed design professional, reinforcement, including
tendons, and post-tensioning ducts shall be placed within the tolerances in 506.5.2.1 and
506.5.2.2.
506.5.2.1
Tolerances for d and for concrete cover in flexural members, walls, and compression
members shall be as follows:
d ≤ 200 mm
d > 200 mm
Tolerance on d
±10 mm
±13 mm
Tolerance on specified concrete cover
–10 mm
–13 mm
except that tolerance for the clear distance to formed soffits shall be minus 6 mm. In
addition, tolerance for cover shall also not exceed minus 1/3 the concrete cover specified in
the design drawings and project specifications.
506.5.2.2
Tolerance for longitudinal location of bends and ends of reinforcement shall be ±50 mm,
except the tolerance shall be ±13 mm at the discontinuous ends of brackets and corbels, and
±25 mm at7the discontinuous ends of other members. The tolerance for concrete cover of
506.5.2.1 shall also apply at discontinuous ends of members.
506.5.3
Welded wire reinforcement (with wire size not greater than MW30 or MD30) used in slabs not
exceeding 3 m in span shall be permitted to be curved from a point near the top of slab over the
support to a point near the bottom of slab at midspan, provided such reinforcement is either
continuous over, or securely anchored at support.
506.6 SPACING LIMITS FOR REINFORCEMENT
The clear distance between reinforcing bars, bundled bars, tendons and ducts shall comply with
this section.
506.6.1
The minimum clear spacing between parallel bars in a layer shall be db, but not less than 25
mm. See also 511.3.2.
506.6.2
Where parallel reinforcement is placed in two or more layers, bars in the upper layers shall
be placed directly above bars in the bottom layer with clear distance between layers not less
than 25 mm.
All rights reserved
229 / 496
506.6.3
In spirally reinforced or tied reinforced compression members, clear distance between
longitudinal bars shall be not less than 1.5db nor less than 40 mm. See also 511.3.2.
506.6.4
Clear distance limitation between bars shall apply also to the clear distance between a contact
lap splice and adjacent splices or bars.
506.6.5
In walls and slabs other than concrete joist construction, primary flexural reinforcement shall
not be spaced farther apart than three times the wall or slab thickness, nor farther apart than
450 mm.
506.6.6 BUNDLED BARS
506.6.6.1
Groups of parallel reinforcing bars bundled in contact to act as a unit shall be limited to four
in any one bundle.
506.6.6.2
Bundled bars shall be enclosed within stirrups or ties.
506.6.6.3
Bars larger than No. 36 shall not be bundled in beams.
506.6.6.4
Individual bars within a bundle terminated within the span of flexural members shall
terminate at different points with at least 40db stagger.
506.6.6.5
Where spacing limitations or concrete cover requirements are based on bar diameter, db, a
unit of bundled bars shall be treated as a single bar of a diameter derived from the
equivalent total area.
506.7 CONCRETE PROTECTION FOR REINFORCEMENT
The minimum specified concrete cover for reinforcement shall comply with Sections 506.7.1 through
506.7.8.
506.7.1 CAST-IN-PLACE CONCRETE (NONPRESTRESSED)
Minimum specified concrete cover shall be provided for reinforcement in nonprestressed, cast-inplace concrete construction in accordance with this section.
Unless a greater concrete cover is required by 506.7.6 or 506.7.8, specified cover for
reinforcement shall not be less than the following:
Concrete cover, mm
(a) Concrete cast against and permanently exposed to earth ...................................................... 75
(b) Concrete exposed to earth or weather: No. 19 through No. 57 bars ....................................50
No. 16 bar, MW200 or MD200 wire, and smaller.............................................................................40
(c) Concrete not exposed to weather or in contact with ground: Slabs, walls, joists:
No. 43 and No. 57 bars .....................................................................................................................40
No. 36 bar and smaller......................................................................................................................20
All rights reserved
230 / 496
Beams, columns:
Primary reinforcement, ties, stirrups, spirals ...................................................................................40
Shells, folded plate members:
No. 19 bar and larger .......................................................................................................................20
No. 16 bar, MW200 or MD200 wire, and smaller ……………………………………………..…………..……..13
506.7.2 CAST-IN-PLACE CONCRETE (PRESTRESSED)
Unless a greater concrete cover is required by 506.7.6 or 506.7.8, specified cover for prestressed
and nonprestressed reinforcement, ducts, and end fittings shall not be less than the following:
Concrete cover, mm
(a) Concrete cast against and permanently exposed to earth.......................................................75
(b) Concrete exposed to earth or weather:
Wall panels, slabs, joists .................................................................................................................25
Other members...............................................................................................................................40
(c) Concrete not exposed to weather or in contact with ground:
Slabs, walls, joists ...........................................................................................................................20
Beams, columns:
Primary reinforcement...................................................................................................................40
Ties, stirrups, spirals ......................................................................................................................25
Shells, folded plate members:
No. 16 bar, MW200 or MD200 wire, and smaller ........................................................................10
Other reinforcement ..................................................................................db but not less than 20
506.7.3 PRECAST CONCRETE (MANUFATURED UNDER PLANT CONTROL CONDITIONS)
The minimum specified concrete cover for prestressed and nonprestressed reinforcement, ducts
and end fittings in precast concrete manufactured under plant control conditions shall comply
with this section.
Unless a greater cover is required by Sections 506.7.6 or 506.7.8, specified cover for prestressed
and onprestressed reinforcement, ducts, and end fittings shall not be less than the following:
Concrete cover, mm
(a) Concrete exposed to earth or weather:
Wall panels:
No. 43 and No. 57 bars, prestressing tendons larger than 40 mm diameter …...........................40
No. 36 bar and smaller, prestressing tendons 40 mm diameter and smaller, MW200 and MD200
wire and smaller ..............................................................................................................................20
Other members:
No. 43 and No. 57 bars, prestressing tendons larger than 40 mm diameter ..............................50
No. 19 through No. 36 bars, prestressing tendons larger than 16 mm diameter through 40 mm
diameter ..........................................................................................................................................40
No. 16 bar and smaller, prestressing tendons 16 mm diameter and smaller, MW200 and MD200
wire, and smaller .............................................................................................................................30
(b) Concrete not exposed to weather or in contact with ground:
Slabs, walls, joists:
No. 43 and No. 57 bars, prestressing tendons larger than 40 mm diameter ..............................30
Prestressing tendons 40 mm diameter and smaller ........................................................................20
No. 36 bar and smaller, MW200 or MD200 wire, and smaller ..................................................... 16
Beams, columns:
Primary reinforcement ...................................... db but not less than 16 and need not exceed 40
Ties, stirrups, spirals ........................................................................................................................10
Shells, folded plate members:
Prestressing tendons .......................................................................................................................20
All rights reserved
231 / 496
No. 19 bar and larger ......................................................................................................................16
No. 16 bar and smaller, MW200 or MD200 wire, and smaller ....................................................10
506.7.4 BUNDLED BARS
The minimum specified concrete cover for bundled bars shall comply with this section. For bundled
bars, minimum specified concrete cover shall not be less than the equivalent diameter of the
bundle, but need not be greater than 50 mm; except for concrete cast against and permanently
exposed to earth, where specified concrete cover shall not be less than 75 mm.
506.7.5 HEADED SHEAR STUD REINFORCEMENT
For headed shear stud reinforcement, specified concrete cover for the heads or base rails shall not
be less than that required for the reinforcement in the type of member in which the headed shear
stud reinforcement is placed.
All rights reserved
232 / 496
FIGURE 506.7.5-1 Concrete cover requirements for headed shear stud reinforcement.
506.7.6 CORROSIVE ENVIRONMENTS
In corrosive environments or other severe exposure conditions, amount of concrete protection
shall be suitably increased, and the pertinent requirements for concrete based on applicable
exposure categories in Section 503 shall be met, or other protection shall be provided.
506.7.7 FUTURE EXTENSIONS
Exposed reinforcement, inserts and plates intended for bonding with future extensions shall be
protected from corrosion.
All rights reserved
233 / 496
506.7.8 FIRE PROTECTION
If the general building code (of which this Code forms a part) requires a thickness of cover for
fire protection greater than the concrete cover in 506.7.1 through 506.7.7, such greater
thicknesses shall be specified.
506.8 SPECIAL REINFORCEMENT DETAILS FOR COLUMNS
Offset bent longitudinal bars in columns and load transfer in structural steel cores of composite
compression members shall comply with the provisions of this section.
506.8.1 OFFSET BARS
Offset bent longitudinal bars shall conform to the following:
506.8.1.1
Slope of inclined portion of an offset bar with axis of column shall not exceed 1 in 6.
506.8.1.2
Portions of bar above and below an offset shall be parallel to axis of column.
506.8.1.3
Horizontal support at offset bends shall be provided by lateral ties, spirals, or parts of the
floor construction. Horizontal support provided shall be designed to resist 1-1/2 times the
horizontal component of the computed force in the inclined portion of an offset bar. Lateral
ties or spirals, if used, shall be placed not more than 150 mm from points of bend.
506.8.1.4
Offset bars shall be bent before placement in the forms. See 506.3.
506.8.1.5
Where a column face is offset 75 mm or greater, longitudinal bars shall not be offset bent.
Separate dowels, lap spliced with the longitudinal bars adjacent to the offset column faces,
shall be provided. Lap splices shall conform to Section 516.17.
506.8.2 STEEL CORES
Load transfer in structural steel cores of composite compression members shall be provided by
the following:
506.8.2.1
Ends of structural steel cores shall be accurately finished to bear at end bearing splices, with
positive provision for alignment of one core above the other in concentric contact.
506.8.2.2
At end bearing splices, bearing shall be considered effective to transfer not more than 50
percent of the total compressive stress in the steel core.
506.8.2.3
Transfer of stress between column base and footing shall be designed in accordance with
Section 519.8.
506.8.2.4
Base of structural steel section shall be designed to transfer the total load from the entire
composite member to the footing; or, the base shall be designed to transfer the load from
the steel core only, provided ample concrete section is available for transfer of the portion
All rights reserved
234 / 496
of the total load carried by the reinforced concrete section to the footing by compression in
the concrete and by reinforcement.
506.9 CONNECTIONS
Connections between concrete framing members shall comply with the provisions of this section.
506.9.1
At connections of principal framing elements (such as beams and columns), enclosure shall be
provided for splices of continuing reinforcement and for anchorage of reinforcement terminating
in such connections.
506.9.2
Enclosure at connections shall consist of external concrete or internal closed ties, spirals, or
stirrups.
506.10 LATERAL REINFORCEMENT FOR COMPRESSION MEMBERS
Lateral reinforcement for concrete compression members shall comply with the provisions of this
section.
506.10.1
Lateral reinforcement for compression members shall conform to the provisions of Sections
506.10.4 and 506.10.5.
506.10.2
Lateral reinforcement requirements for composite compression members shall conform to
Section 514.13.
506.10.3
It shall be permitted to waive the lateral reinforcement requirements of Sections 506.10 and
506.13 where tests and structural analysis show adequate strength and feasibility of
construction.
506.10.4 SPIRALS
Spiral reinforcement for compression members shall conform to 514.9.3 and to the following:
506.10.4.1
Spirals shall consist of evenly spaced continuous bar or wire of such size and so assembled to
permit handling and placing without distortion from designed dimensions.
506.10.4.2
For cast-in-place construction, size of spirals shall not be less than 10 mm diameter.
506.10.4.3
Clear spacing between spirals shall not exceed 75 mm, nor be less than 25 mm. See also
Section 511.3.2.
506.10.4.4
Anchorage of spiral reinforcement shall be provided by 1-1/2 extra turns of spiral bar or wire
at each end of a spiral unit.
506.10.4.5
Spiral reinforcement shall be spliced, if needed, by any one of the following methods:
(a) Lap splices not less than the larger of 300 mm and the length indicated in one of (1)
through (5) below:
All rights reserved
235 / 496
(1) deformed uncoated bar or wire.....................................................................................48db
(2) plain uncoated bar or wire ............................................................................................72db
(3) plain uncoated bar or wire with a standard stirrup or tie hook in accordance with Section
506.1.3 at ends of lapped spiral reinforcement.
The hooks shall be embedded within the core confined by the spiral
reinforcement......................................................................................................................48db
506.10.4.6
Spirals shall extend from top of footing or slab in any story to level of lowest horizontal
reinforcement in members supported above.
506.10.4.7
Where beams or brackets do not frame into all sides of a column, ties shall extend above
termination of spiral to bottom of slab, drop panel, or shear cap.
506.10.4.8
In columns with capitals, spirals shall extend to a level at which the diameter or width of
capital is two times that of the column.
506.10.4.9
Spirals shall be held firmly in place and true to line.
506.10.5 TIES
Tie reinforcement for compression members shall conform to the following:
506.10.5.1
All nonprestressed bars shall be enclosed by lateral ties, at least No. 10 in size for
longitudinal bars No. 32 or smaller, and at least No. 13 in size for No. 36, No. 43, No. 57, and
bundled longitudinal bars. Deformed wire or welded wire reinforcement of equivalent area
shall be permitted.
506.10.5.2
Vertical spacing of ties shall not exceed 16 longitudinal bar diameters, 48 tie bar or wire
diameters, or least dimension of the compression member.
506.10.5.3
Ties shall be arranged such that every corner and alternate longitudinal bar shall have lateral
support provided by the corner of a tie with an included angle of not more than 135 degrees
and no bar shall be farther than 150 mm clear on each side along the tie from such a
laterally supported bar. Where longitudinal bars are located around the perimeter of a
circle, a complete circular tie shall be permitted.
All rights reserved
236 / 496
FIGURE 506.10.5.3-1 Sketch to clarify measurements between laterally supported column bars.
506.10.5.4
Ties shall be located vertically not more than one-half a tie spacing above the top of footing
or slab in any story, and shall be spaced as provided herein to not more than one-half a tie
spacing below the lowest horizontal reinforcement in slab, drop panel, or shear cap above.
506.10.5.5
Where beams or brackets frame from four directions into a column, termination of ties not
more than 75 mm below lowest reinforcement in shallowest of such beams or brackets shall
be permitted.
506.10.5.6
Where anchor bolts are placed in the top of columns or pedestals, the bolts shall be
enclosed by lateral reinforcement that also surrounds at least four vertical bars of the
column or pedestal. The lateral reinforcement shall be distributed within 125 mm of the top
of the column or pedestal, and shall consist of at least two No. 13 or three No. 10 bars.
506.11 LATERAL REINFORCEMENT FOR FLEXURAL MEMBERS
Lateral reinforcement for compression reinforcement in concrete flexural members shall comply with
the provisions of this section.
506.11.1
Compression reinforcement in beams shall be enclosed by ties or stirrups satisfying the size and
spacing limitations in Section 506.10.5 or by welded wire reinforcement of equivalent area. Such
ties or stirrups shall be provided throughout the distance where compression reinforcement is
required.
506.11.2
Lateral reinforcement for flexural framing members subject to stress reversals or to torsion at
supports shall consist of closed ties, closed stirrups, or spirals extending around the flexural
reinforcement.
506.11.3
Closed ties or stirrups shall be formed in one piece by overlapping standard stirrup or tie end
hooks around a longitudinal bar, or formed in one or two pieces lap spliced with a Class B splice
(lap of 1.3ld) or anchored in accordance with Section 516.13.
All rights reserved
237 / 496
506.12 SHRINKAGE AND TEMPERATURE REINFORCEMENT
Reinforcement for shrinkage and temperature stresses in concrete members shall comply with the
provisions of this section.
506.12.1
Reinforcement for shrinkage and temperature stresses normal to flexural reinforcement shall be
provided in structural slabs where the flexural reinforcement extends in one direction only.
506.12.1.1
Shrinkage and temperature reinforcement shall be provided in accordance with either
Sections 506.12.2 or 506.12.3.
506.12.1.2
Where shrinkage and temperature movements are significantly restrained, the requirements
of Sections 512.2.4 and 512.2.3 shall be considered.
506.12.2
Deformed reinforcement conforming to Section 511.5.3 used for shrinkage and temperature
reinforcement shall be provided in accordance with the following:
506.12.2.1
Area of shrinkage and temperature reinforcement shall provide at least the following ratios
of reinforcement area to gross concrete area, but not less than 0.0014:
(a) Slabs where Grade 280 or 530 deformed bars are used ........................................0.0020
(b) Slabs where Grade 420 deformed bars or welded wire reinforcement are used
..........................................................................................................................................0.0018
(c) Slabs where reinforcement with yield stress exceeding 420 MPa measured at a yield
strain of 0.35 percent is used.......................................................................(0.0018 × 420) / fy
506.12.2.2
Shrinkage and temperature reinforcement shall be spaced not farther apart than five times
the slab thickness, nor farther apart than 450 mm.
506.12.2.3
At all sections where required, reinforcement to resist shrinkage and temperature stresses
shall develop fy in tension in accordance with Section 516.
506.13 REQUIREMENTS FOR STRUCTURAL INTEGRITY
The detailing of reinforcement and connections between concrete members shall comply with the
provisions of this section, to improve structural integrity.
506.13.1
In the detailing of reinforcement and connections, members of a structure shall be effectively
tied together to improve integrity of the overall structure.
All rights reserved
238 / 496
FIGURE 516.131-1 Example of a two-piece stirrup that complies with the requirements of 506.13.2.3.
506.13.2
For cast-in-place construction, the following shall constitute minimum requirements:
506.13.2.1
In joist construction at least one bottom bar shall be continuous or shall be spliced with a
Class B tension splice or a mechanical or welded splice satisfying 516.14.3 and at
noncontinuous supports shall be anchored to develop fy at the face of the support using a
standard hook satisfying 516.5 or headed deformed bar satisfying 516.6.
506.13.2.2
Beams along the perimeter of the structure shall have continuous reinforcement over the
span length passing through the region bounded by the longitudinal reinforcement of the
column consisting of (a) and (b):
(a) at least one-sixth of the tension reinforcement required for negative moment at the
support, but not less than two bars;
(b) at least one-quarter of the tension reinforcement required for positive moment at
midspan, but not less than two bars.
At noncontinuous supports, the reinforcement shall be anchored to develop fy at the face of
the support using a standard hook satisfying 516.5 or headed deformed bar satisfying 516.6.
506.13.2.3
The continuous reinforcement required in 506.13.2.2 shall be enclosed by transverse
reinforcement. The transverse reinforcement shall be anchored. The transverse
reinforcement need not be extended through the column.
506.13.2.4
Where splices are required to satisfy Section 506.13.2.2, the top reinforcement shall be
spliced at or near midspan and bottom reinforcement shall be spliced at or near the support.
Splices shall be Class B tension splices, or mechanical or welded splices satisfying 516.14.3.
All rights reserved
239 / 496
506.13.2.5
In other than perimeter beams, where transverse reinforcement as defined in Section
506.13.2.3 is provided, there are no additional requirements for longitudinal integrity
reinforcement. Where such transverse reinforcement is not provided, at least one quarter of
the positive moment reinforcement required at midspan, but not less than two bars, shall
pass through the region bounded by the longitudinal reinforcement of the column and shall
be continuous or shall be spliced over or near the support with a Class B tension splice, or a
mechanical or welded splice satisfying Section 516.14.3. At noncontinuous supports, the
reinforcement shall be anchored to develop fy at the face of the support using a standard
hook satisfying Section 516.5 or headed deformed bar satisfying Section 516.6.
506.13.2.6
For nonprestressed two-way slab construction, see Section 517.3.8.5.
506.13.3
For precast concrete construction, tension ties shall be provided in the transverse, longitudinal,
and vertical directions and around the perimeter of the structure to effectively tie elements
together. The provisions of Section 520.5 shall apply.
SECTION 507 STRUCTURAL PLAIN CONCRETE
507.1 SCOPE
The design and construction of structural plain concrete, both cast-in-place and precast, shall comply
with the minimum requirements of this section.
507.1.1 SPECIAL STRUCTURES
For special structures, such as arches, underground utility structures, gravity walls and shielding
walls, the provisions of this section shall govern where applicable.
507.2 LIMITATIONS
The use of structural plain concrete shall be limited to:
1. Members that are continuously supported by soil, such as walls and footings, or by other structural
members capable of providing continuous vertical support.
2. Members for which arch action provides compression under all conditions of loading.
3. Walls and pedestals.
The use of structural plain concrete columns and structural plain concrete footings on piles is not
permitted.
507.3 JOINTS
Contraction or isolation joints shall be provided to divide structural plain concrete members into
flexurally discontinuous elements in accordance with this section.
507.3.1
Contraction or isolation joints shall be provided to divide structural plain concrete members into
flexurally discontinuous elements. The size of each element shall be chosen to limit stress
caused by restraint to movements from creep, shrinkage, and temperature effects.
507.3.2
In determining the number and location of contraction or isolation joints, consideration shall be
given to: influence of climatic conditions; selection and proportioning of materials; mixing,
placing, and curing of concrete; degree of restraint to movement; stresses due to loads to which
an element is subject; and construction techniques.
All rights reserved
240 / 496
507.4 DESIGN METHOD
Structural plain concrete walls, footings and pedestals shall be designed for adequate strength in
accordance with Sections 507.4 through 507.8.
Exception: For Group R-3 occupancies and buildings of other occupancies less than two stories above
grade plane of light-frame construction, the required edge thickness of Appendix A is permitted to be
reduced to 150 mm, provided that the footing does not extend more than 100 mm on either side of the
supported wall.
507.4 DESIGN METHOD
507.4.1
Factored loads and forces shall be in combinations as in Section 513.2.
507.4.2
Where required strength exceeds design strength, reinforcement shall be provided and the
member designed as a reinforced concrete member in accordance with appropriate design
requirements of this Code.
507.4.3
Strength design of structural plain concrete members for flexure and axial loads shall be based
on a linear stress-strain relationship in both tension and compression.
507.4.4
Tensile strength of concrete shall be permitted to be considered in design of plain concrete
members when provisions of Section 507.3 have been followed.
507.4.5
No strength shall be assigned to steel reinforcement that may be present.
507.4.6
Tension shall not be transmitted through outside edges, construction joints, contraction joints,
or isolation joints of an individual plain concrete element. No flexural continuity due to tension
shall be assumed between adjacent structural plain concrete elements.
507.4.7
When computing strength in flexure, combined flexure and axial load, and shear, the entire
cross section of a member shall be considered in design, except for concrete cast against soil
where overall thickness h shall be taken as 50 mm less than actual thickness.
507.5 STRENGTH DESIGN
507.5.1
Design of cross sections subject to flexure shall be based on
φMn ≥ Mu
EQUATION 507.5.1-1
where
Mn = 0.42λ √
EQUATION 507.5.1-2
if tension controls, and
Mn = 0.85f΄c Sm
All rights reserved
EQUATION 507.5.1-3
241 / 496
if compression controls, where Sm is the corresponding elastic section modulus.
507.5.2
Design of cross sections subject to compression shall be based on
φPn ≥ Pu
EQUATION 507.5.2-1
where Pn is computed by
Pn= 0.60f΄c [ 1-(lc/32h)2] A1
EQUATION 507.5.2-2
and A1 is the loaded area.
507.5.3
Members subject to combined flexure and axial load in compression shall be proportioned
such that on the compression face:
Pu /φPn + Mu /φMn ≤ 1
EQUATION 507.5.3-1
and on the tension face
Mu /Sm – Pu /Ag ≤ 0.42φλ √
EQUATION 507.5.3-2
507.5.4
Design of rectangular cross sections subject to shear shall be based on
φVn ≥ Vu
EQUATION 507.5.4-1
where Vn is computed by
Vn = 0.11λ √
bwh
EQUATION 507.5.4-2
for beam action and by
Vn = 0.11 [1+ 2/β λ √
boh
EQUATION 507.5.4-3
for two-way action, but not greater than 0.22λ √ boh.
In Equation 507.5.4-3, β corresponds to ratio of long side to short side of concentrated load
or reaction area.
507.5.5
Design of bearing areas subject to compression shall be based on
φBn ≥ Bu
EQUATION 507.5.5-1
where Bu is factored bearing load and Bn is nominal bearing strength of loaded area A1
calculated by
Bn = 0.85f΄c A1
All rights reserved
EQUATION 507.5.5-2
242 / 496
except where the supporting surface is wider on all sides than the loaded area, then Bn shall
be multiplied by √
but not more than 2.
507.6 WALLS
507.6.1
Structural plain concrete walls shall be continuously supported by soil, footings, foundation
walls, grade beams, or other structural members capable of providing continuous vertical
support.
507.6.2
Structural plain concrete walls shall be designed for vertical, lateral, and other loads to which
they are subjected.
507.6.3
Structural plain concrete walls shall be designed for an eccentricity corresponding to the
maximum moment that can accompany the axial load but not less than 0.10h. If the resultant of
all factored loads is located within the middle third of the overall wall thickness, the design shall
be in accordance with Section 507.5.3 or 507.6.5. Otherwise, walls shall be designed in
accordance with Section 507.5.3.
507.6.4
Design for shear shall be in accordance with 507.5.4.
507.6.5 EMPRICAL DESIGN METHOD
507.6.5.1
Structural plain concrete walls of solid rectangular cross section shall be permitted to be
designed by Equation 507.6.5.2-1 if the resultant of all factored loads is located within the
middle-third of the overall thickness of wall.
507.6.5.2
Design of walls subject to axial loads in compression shall be based on
φPn ≥ Pu
EQUATION 507.6.5.2-1
where Pu is factored axial force and Pn is nominal axial strength calculated by
Pn= 0.45f΄c Ag [1-(lc/32h)2]
EQUATION 507.6.5.2-2
507.6.6 LIMITATIONS
507.6.6.1
Unless demonstrated by a detailed analysis, horizontal length of wall to be considered
effective for each vertical concentrated load shall not exceed center-to-center distance
between loads, nor width of bearing plus four times the wall thickness.
507.6.6.2
Except as provided in 507.6.6.3, thickness of bearing walls shall be not less than 1/24 the
unsupported height or length, whichever is shorter, nor less than 140 mm.
507.6.6.3
Thickness of exterior basement walls and foundation walls shall be not less than 190 mm.
All rights reserved
243 / 496
507.6.6.4
Walls shall be braced against lateral translation. See 507.3 and 507.4.7.
507.6.6.5
Not less than two No. 16 bars shall be provided around all window and door openings. Such
bars shall extend at least 600 mm beyond the corners of openings.
507.6.7
Detailed plain concrete structural walls.
507.6.7.1
Detailed plain concrete structural walls are walls conforming to the requirements of ordinary
struc- tural plain concrete walls and 507.6.7.2.
507.6.7.2
Reinforcement shall be provided as follows:
(a) Vertical reinforcement of at least 130 mm2 in cross-sectional area shall be provided
continuously from support to support at each corner, at each side of each opening and at
the ends of walls. The continuous vertical bar required beside an opening is permitted
to sub- stitute for one of the two No. 5 bars required by 507.6.6.5.
(b) Horizontal reinforcement at least 130 mm2 in cross-sectional area shall be provided:
1. Continuously at structurally connected roof and floor levels and at the top of walls;
2. At the bottom of load-bearing walls or in the top of foundations where doweled to the
wall; and
3. At a maximum spacing of 3000 mm.
Reinforcement at the top and bottom of openings, where used in determining the maximum
spacing specified in Item 3 above, shall be continuous in the wall.
507.7 FOOTINGS
507.7.1
Structural plain concrete footings shall be designed for factored loads and induced reactions in
accordance with appropriate design requirements of this Code and as provided in 507.7.2
through 507.7.8.
507.7.2
Base area of footing shall be determined from unfactored forces and moments transmitted by
footing to soil and permissible soil pressure selected through principles of soil mechanics.
507.7.3
Plain concrete shall not be used for footings on piles.
507.7.4
Thickness of structural plain concrete footings shall be not less than 200 mm. See 507.4.7.
507.7.5
Maximum factored moment shall be computed at (a), (b), and (c):
(a) At the face of the column, pedestal, or wall, for footing supporting a concrete column,
pedestal, or wall;
(b) Halfway between center and face of the wall, for footing supporting a masonry wall;
(c) Halfway between face of column and edge of steel base plate, for footing supporting a
column with steel base plate.
All rights reserved
244 / 496
507.7.6 SHEAR IN PLAIN CONCRETE FOOTINGS
507.7.6.1
Vu shall be computed in accordance with 507.7.6.2, with location of critical section
measured from face of column, pedestal, or wall for footing supporting a column, pedestal,
or wall. For footing supporting a column with steel base plates, the critical section shall be
measured at location defined in 507.7.5(c).
507.7.6.2
φVn of structural plain concrete footings in the vicinity of concentrated loads or reactions
shall be governed by the more severe of two conditions:
(a) Beam action for footing, with a critical section extending in a plane across the entire
footing width and located at a distance h from face of concentrated load or reaction
area. For this condition, the footing shall be designed in accordance with Equation
507.5.4-2;
(b) Two-way action for footing, with a critical section perpendicular to plane of footing and
located so that its perimeter bo is a minimum, but need not approach closer than h/2 to
perimeter of concentrated load or reaction area. For this condition, the footing shall be
designed in accordance with Equation 507.5.4-3.
507.7.7
Circular or regular polygon-shaped concrete columns or pedestals shall be permitted to be
treated as square members with the same area for location of critical sections for moment
and shear.
507.7.8
Factored bearing load, Bu, on concrete at contact surface between supporting and
supported member shall not exceed design bearing strength, φBn, for either surface as given
in 507.5.5.
507.8 PEDESTALS
507.8.1
Plain concrete pedestals shall be designed for vertical, lateral, and other loads to which they are
subjected.
507.8.2
Ratio of unsupported height to average least lateral dimension of plain concrete pedestals shall
not exceed 3.
507.8.3
Maximum factored axial load, Pu, applied to plain concrete pedestals shall not exceed design
bearing strength, φBn, given in 507.5.5.
507.9 PRECAST MEMBERS
The design, fabrication, transportation and erection of precast, structural plain concrete elements shall
be in accordance with this section.
507.9.1
All rights reserved
245 / 496
Design of precast plain concrete members shall consider all loading conditions from initial
fabrication to completion of the structure, including form removal, storage, transportation, and
erection.
507.9.2
Limitations of 507.2 apply to precast members of plain concrete not only to the final condition
but also during fabrication, transportation, and erection.
507.9.3
Precast members shall be connected securely to transfer all lateral forces into a structuralsystem
capable of resisting such forces.
507.9.4
Precast members shall be adequately braced and supported during erection to ensure proper
alignment and structural integrity until permanent connections are completed.
507.10 PLAIN CONCRETE IN EARTHQUAKE RESISTING STRUCTURES
Plain concrete in structures assigned to Seismic Design Category C, D, E or F.
507.10.1
Structures assigned to Seismic Design Category C, D, E or F shall not have elements of structural
plain concrete, except as follows:
(a) Structural plain concrete basement, foundation or other walls below the base are permitted
in detached one- and two-family dwellings three stories or less in height constructed
with stud-bearing walls. In dwellings assigned to Seismic Design Category D or E, the height of
the wall shall not exceed 2400 mm, the thickness shall not be less than 190 mm, and the wall
shall retain no more than 1200 mm of unbalanced fill. Walls shall have reinforcement in
accordance with 507.6.6.5.
(b) Isolated footings of plain concrete supporting pedestals or columns are permitted, provided
the projection of the footing beyond the face of the supported member does not exceed the
footing thickness.
Exception: In detached one- and two-family dwellings three stories or less in height, the
projection of the footing beyond the face of the sup- ported member is permitted to exceed
the footing thickness.
(c) Plain concrete footings supporting walls are permitted, provided the footings have at least
two continuous longitudinal reinforcing bars. Bars shall not be smaller than No. 4 and shall
have a total area of not less than 0.002 times the gross cross-sectional area of the footing. For
footings that exceed 200mm in thickness, a minimum of one bar shall be provided at the top
and bottom of the footing. Continuity of reinforcement shall be provided at corners and
intersections.
Exceptions:
1. In detached one- and two-family dwellings three stories or less in height and constructed
with stud-bearing walls, plain concrete footings without longitudinal reinforcement
supporting walls are permitted.
2. For foundation systems consisting of a plain concrete footing and a plain concrete
stemwall, a minimum of one bar shall be provided at the top of the stemwall and at the
bottom of the footing.
3. Wher e a sl ab on ground i s cast monolithically with the footing, one No. 5 bar is
permitted to be located at either the top of the slab or bottom of the footing.
SECTION 508 MINIMUM SLAB PROVISIONS
508.1 GENERAL
All rights reserved
246 / 496
The thickness of concrete floor slabs supported directly on the ground shall not be less than 100 mm. A 6mil (0.15 mm) polyethylene vapor retarder with joints lapped not less than 150 mm shall be placed
between the base course or subgrade and the concrete floor slab, or other approved equivalent methods
or materials shall be used to retard vapor transmission through the floor slab.
SECTION 509 ANCHORAGE TO CONCRETE-ALLOWABLE STRESS DESIGN
509.1 SCOPE
The provisions of this section shall govern the allowable stress design of headed bolts and headed
stud anchors cast in normal-weight concrete for purposes of transmitting structural loads from one
connected element to the other. These provisions do not apply to anchors installed in hardened
concrete or where load combinations include earthquake loads or effects. The bearing area of headed
anchors shall be not less than one and one-half times the shank area. Where strength design is used,
or where load combinations include earthquake loads or effects, the design strength of anchors shall
be determined in accordance with Section 510. Bolts shall conform to ASTM A 317 or an approved
equivalent.
509.2 ALLOWABLE SERVICE LOAD
The allowable service load for headed anchors in shear or tension shall be as indicated in Table 1911.2.
Where anchors are subject to combined shear and tension, the following relationship shall be satisfied:
5/3
5/3
(Ps / Pt ) + (Vs / Vt )
≤ 1
where:
Ps
= Applied tension service load, N.
EQUATION 509.2-1
Pt
= Allowable tension service load from Table 509.5-1, N.
Vs
= Applied shear service load, N.
Vt
= Allowable shear service load from Table 509.5-1, N.
509.3 REQUIRED EDGE DISTANCE AND SPACING
The allowable service loads in tension and shear specified in Table 509.5-1are for the edge distance and
spacing specified. The edge distance and spacing are permitted to be reduced to 50 percent of the values
specified with an equal reduction in allowable service load. Where edge distance and spacing are
reduced less than 50 percent, the allowable service load shall be determined by linear interpolation.
509.4 INCREASE IN ALLOWABLE LOAD
Increase of the values in Table 509.5-1 by one-third is permitted where the provisions of Section
302.4.3 permit an increase in allowable stress for wind loading.
509.5 INCREASE FOR SPECIAL INSPECTION
Where special inspection is provided for the installation of anchors, a 100-percent increase in the
allowable tension values of Table 509.5-1 is permitted. No increase in shear value is permitted.
TABLE 509.5-1 ALLOWABLE SERVICE LOAD ON EMBEDDED BOLTS (N)
BOLT
DIAMETER
(mm)
6
9
13
16
All rights reserved
MINIMUM
EMBEDMENT
(mm)
60
80
100
100
120
EDGE
DISTANCE
(mm)
40
60
80
130
100
SPACING
(mm)
80
120
150
150
190
MINIMUM CONCRETE STRENGTH (MPa)
f΄c = 17
f΄c = 21
f΄c = 28
Tension Shear Tension Shear Tension Shear
890
2220
890
2220
890
2220
2220
4890
2220
4890
2220
4890
4230
5560
950
5560
950
5560
6450
7120
6670
7340
6900
7790
6670
12240 6670
12240 6670
12240
247 / 496
120
130
130
150
180
200
230
19
22
25
28
32
160
120
190
130
150
170
190
190
230
230
270
300
350
380
9460
10010
12570
11350
13570
15130
17800
13130
14460
19020
16460
18360
21140
25810
9790
10010
13130
11350
14460
15130
17800
13350
15840
19130
18020
20020
21140
25810
10680
10010
14240
11350
16240
15130
17800
13570
15840
19580
18020
23580
21140
25810
SECTION 510 ANCHORAGE TO CONCRETE-STRENGTH DESIGN
510.1 SCOPE
The provisions of this section shall govern the strength design of anchors installed in concrete for
purposes of transmitting structural loads from one connected element to the other. Headed bolts,
headed studs and hooked (J- or L-) bolts cast in concrete and expansion anchors and undercut anchors
installed in hardened concrete shall be designed in accordance with Appendix B.
SECTION 511 MATERIALS
511.1 TEST OF MATERIALS
511.1.1
The building official shall have the right to order testing of any materials used in concrete
construction to determine if materials are of quality specified.
511.1.2
Tests of materials and of concrete shall be made in accordance with standards listed in 511.8.
511.1.3
A complete record of tests of materials and of concrete shall be retained by the inspector for 2
years after completion of the project, and made available for inspection during the progress of
the Work.
511.2 CEMENTITIOUS MATERIALS
511.2.1
Cementitious materials shall conform to the relevant specifications as follows:
(a) Portland cement: ASTM C150;
(b) Blended hydraulic cements: ASTM C595 excluding Type IS (≥70), which is not intended as
principal cementing constituents of structural concrete;
(c) Expansive hydraulic cement: ASTM C845;
(d) Hydraulic cement: ASTM C1157;
(e) Fly ash and natural pozzolan: ASTM C618;
(f) Ground-granulated blast-furnace slag: ASTM C989;
(g) Silica fume: — Cementitious materials used in the Work shall correspond to those used as the
basis for selecting concrete mixture proportions. See 504.2.
511.3 AGGREGATES
511.3.1
Concrete aggregates shall conform to one of the following specifications:
Normalweight: ASTM C33;
511.3.2
Nominal maximum size of coarse aggregate shall be not larger than:
(a) 1/5 the narrowest dimension between sides of forms, nor
All rights reserved
248 / 496
(b) 1/3 the depth of slabs, nor
(c) 3/4 the minimum clear spacing between individual reinforcing bars or wires, bundles of bars,
individual tendons, bundled tendons, or ducts.
511.4 WATER
511.4.1
Water used in mixing concrete shall conform to ASTM C1602M.
511.5
511.5.1
Reinforcement shall be deformed reinforcement, except that plain reinforcement shall be
permitted for spirals or prestressing steel; and reinforcement consisting of headed shear studs,
structural steel, steel pipe, or steel tubing shall be permitted as specified.
511.5.2
Welding of reinforcing bars shall conform to AWS D1.4. Type and location of welded splices and
other required welding of reinforcing bars shall be indicated on the design drawings or in the
project specifications. ASTM specifications for bar reinforcement, except for ASTM A706M, shall
be supplemented to require a report of material properties necessary to conform to the
requirements in AWS D1.4.
511.5.3 DEFORMED REINFORCEMENT
511.5.3.1
Deformed reinforcing bars shall conform to the requirements for deformed bars in one of
the following specifications, except as permitted by 511.5.3.3:
(a) Carbon steel: ASTM A615M;
(b) Low-alloy steel: ASTM A706M;
511.5.3.2
Deformed reinforcing bars shall conform to one of the ASTM specifications listed in
515.7.3.1, except that for bars with fy exceeding 420 MPa, the yield strength shall be taken
as the stress corresponding to a strain of 0.35 percent. See 513.4.
511.5.3.3
Deformed reinforcing bars conforming to ASTM A1035 shall be permitted to be used as
transverse reinforcement in 521.6.4 or spiral reinforcement in 514.9.3.
511.5.3.4
Bar mats for concrete reinforcement shall conform to ASTM A184M. Reinforcing bars used
in bar mats shall conform to ASTM A615M or ASTM A706M.
511.5.3.5
Deformed wire for concrete reinforcement shall conform to ASTM A496M, except that wire
shall not be smaller than size MD25 or larger than size MD200 unless as permitted in
511.5.3.7. For wire with fy exceeding 420 MPa, the yield strength shall be taken as the stress
corresponding to a strain of 0.35 percent.
511.5.3.6
Welded plain wire reinforcement shall conform to ASTM A185M, except that for wire with fy
exceeding 420 MPa, the yield strength shall be taken as the stress corresponding to a strain
of 0.35 percent. Spacing of welded intersections shall not exceed 300 mm in direction of
All rights reserved
249 / 496
calculated stress, except for welded wire reinforcement used as stirrups in accordance with
516.13.2.
511.5.3.7
Welded deformed wire reinforcement shall conform to ASTM A497M, except that for wire
with fy exceeding 420 MPa, the yield strength shall be taken as the stress corresponding to a
strain of 0.35 percent. Spacing of welded intersections shall not exceed 400 mm in direction
of calculated stress, except for welded deformed wire reinforcement used as stirrups in
accordance with 516.13.2. Deformed wire larger than MD200 is permitted when used in
welded wire reinforcement conforming to ASTM A497M, but shall be treated as plain wire
for development and splice design.
511.5.3.8
Galvanized reinforcing bars shall conform to ASTM A767M. Epoxy-coated reinforcing bars
shall comply with ASTM A775M or with ASTM A934M. Bars to be galvanized or epoxy-coated
shall conform to one of the specifications listed in 511.5.3.1.
511.5.3.9
Epoxy-coated wires and welded wire reinforcement shall conform to ASTM A884M. Wires to
be epoxy-coated shall conform to 511.5.3.4 and welded wire reinforcement to be epoxycoated shall conform to 511.5.3.5 or 511.5.3.6.
511.5.3.10
Deformed stainless-steel wire and deformed and plain stainless-steel welded wire for
concrete reinforcement shall conform to ASTM A1022M, except deformed wire shall not be
smaller than size MD25 or larger than size MD200, and the yield strength for wire with fy
exceeding 420 MPa shall be taken as the stress corresponding to a strain of 0.35 percent.
511.5.4 PLAIN REINFORCEMENT
511.5.4.1
Plain bars for spiral reinforcement shall conform to the specification in 511.5.3.1(a) or (b).
511.5.4.2
Plain wire for spiral reinforcement shall3conform to ASTM A82M, except that for wire with
fy exceeding 420 MPa, the yield strength shall be taken as the stress corresponding to a
strain of 0.35 percent.
511.5.5 HEADED SHEAR STUD REINFORCEMENT
511.5.5.1
Headed studs and headed stud assemblies shall conform to ASTM A1044M.
511.5.6
Headed deformed bars shall conform to ASTM A970M and obstructions or interruptions of the
bar deformations, if any, shall not extend more than 2db from the bearing face of the head.
511.6 ADMIXTURES
511.6.1
Admixtures for water reduction and setting time modification shall conform to ASTM C494M.
Admixtures for use in producing flowing concrete shall conform to ASTM C1017M.
All rights reserved
250 / 496
511.6.2
Air-entraining admixtures shall conform to ASTM C260.
511.6.3
Admixtures to be used in concrete that do not conform to 511.6.1 and 511.6.2 shall be subject
to prior approval by the licensed design professional.
511.6.4
Calcium chloride or admixtures containing chloride from sources other than impurities in
admixture ingredients shall not be used in prestressed concrete, in concrete containing
embedded aluminum, or in concrete cast against stay-in-place galvanized steel forms. See
503.3.1.
511.6.5
Admixtures used in concrete containing expansive cements conforming to ASTM C845 shall be
compatible with the cement and produce no deleterious effects.
511.7 STORAGE OF MATERIALS
511.7.1
Cementitious materials and aggregates shall be stored in such manner as to prevent
deterioration or intrusion of foreign matter.
511.7.2
Any material that has deteriorated or has been contaminated shall not be used for concrete.
511.8 REFERENCED STANDARDS
511.8.1
Standards of ASTM International referred to in this Code are listed below with their serial
designations, including year of adoption or revision, and are declared to be part of this Code as if
fully set forth herein:
A36/A36M-05 Standard Specification for Carbon Structural Steel
A53/A53M-07 Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc- Coated,
Welded and Seamless
A82/A82M-07 Standard Specification for Steel Wire, Plain, for Concrete Reinforcement
A184/A184M-06 Standard Specification for Welded Deformed Steel Bar Mats for Concrete
Reinforcement
A185/A185M-07 Standard Specification for Steel Welded Wire Reinforcement, Plain, for
Concrete
A242/A242M-04ε1 Standard Specification for High- Strength Low-Alloy Structural Steel
A307-07a Standard Specification for Carbon Steel Bolts and Studs, 60,000 psi Tensile Strength
A416/A416M-06 Standard Specification for Steel Strand, Uncoated Seven-Wire for Prestressed
Concrete
A421/A421M-05 Standard Specification for Uncoated Stress-Relieved Steel Wire for Prestressed
Concrete
A496/A496M-07 Standard Specification for Steel Wire, Deformed, for Concrete Reinforcement
A497/A497M-07 Standard Specification for Steel Welded Wire Reinforcement, Deformed, for
Concrete
A500/A500M-07 Standard Specification for Cold- Formed Welded and Seamless Carbon Steel
Structural Tubing in Rounds and Shapes
A501-07 Standard Specification for Hot- Formed Welded and Seamless Carbon Steel Structural
Tubing
All rights reserved
251 / 496
A572/A572M-07 Standard Specification for High- Strength Low-Alloy Columbium- Vanadium
Structural Steel
A588/A588M-05 Standard Specification for High- Strength Low-Alloy Structural Steel with 50 ksi
[345 MPa] Minimum Yield Point to 4-in. [100-mm] Thick
A615/A615M-07 Standard Specification for Deformed and Plain Carbon Steel Bars for Concrete
Reinforcement
A706/A706M-06a Standard Specification for Low- Alloy Steel Deformed and Plain Bars for
Concrete Reinforcement
A722/A722M-07 Standard Specification for Uncoated High-Strength Steel Bars for Prestressing
Concrete
A767/A767M-05 Standard Specification for Zinc- Coated (Galvanized) Steel Bars for Concrete
Reinforcement
A775/A775M-07a Standard Specification for Epoxy- Coated Steel Reinforcing Bars
A820/A820M-06 Standard Specification for Steel Fibers for Fiber-Reinforced Concrete
A884/A884M-06 Standard Specification for Epoxy- Coated Steel Wire and Welded Wire
Reinforcement
A934/A934M-07 Standard Specification for Epoxy- Coated Prefabricated Steel Reinforcing Bars
A955/A955M-07a Standard Specification for Deformed and Plain Stainless- Steel Bars for
Concrete Reinforcement
A970/A970M-06 Standard Specification for Headed Steel Bars for Concrete Reinforcement
A992/A992M-06a Standard Specification for Structural Steel Shapes
A996/A996M-06a Standard Specification for Rail- Steel and Axle-Steel Deformed Bars for
Concrete Reinforcement
A1022/A1022M-07 Standard Specification for Deformed and Plain Stainless Steel Wire and
Welded Wire for Concrete Reinforcement
A1035/A1035M-07 Standard Specification for Deformed and Plain, Low-Carbon, Chromium,
Steel Bars for Concrete Reinforcement
A1044/A1044M-05 Standard Specification for Steel Stud Assemblies for Shear Reinforcement
of Concrete
C29/C29M-97(2003)Standard Test Method for Bulk Density (“Unit Weight”) and Voids
in Aggregate
C31/C31M-06 Standard Practice for Making and Curing Concrete Test Specimens
in the Field
C33-03 Standard Specification for Concrete Aggregates
C39/C39M-05ε1 Standard Test Method for ompressive Strength of ylindrical oncrete
Specimens
C42/C42M-04 Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams
of Concrete
C94/C94M-06 Standard Specification for Ready- Mixed Concrete
C109/C109M-05 Standard Test Method for Compressive Strength of Hydraulic
Cement Mortars (Using 2-in. Or [50-mm] Cube Specimens)
C144-04 Standard Specification for Aggregate for Masonry Mortar
C150-05 Standard Specification for Portland Cement
C172-04 Standard Practice for Sampling Freshly Mixed Concrete
C192/C192M-06 Standard Practice for Making and Curing Concrete Test Specimens in the
Laboratory
C231-04 Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure
Method
C260-06 Standard Specification for Air- Entraining Admixtures for Concrete
C330-05 Standard Specification for Lightweight Aggregates for Structural Concrete
C494/C494M-05a Standard Specification for Chemical Admixtures for Concrete
C496/C496M-04 Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete
specimens
All rights reserved
252 / 496
C567-05a Standard Test Method for Determining Density of Structural Lightweight Concrete
C595-07 Standard Specification for Blended Hydraulic Cements
C618-05 Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in
Concrete
C685/C685M-01 Standard Specification for Concrete Made by Volumetric Batching and
Continuous Mixing
C845-04 Standard Specification for Expansive Hydraulic Cement
C989-06 Standard Specification for Ground Granulated Blast-Furnace Slag for Use in Concrete
and Mortars
C1012-04 Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate
Solution
C1017/C1017M-03 Standard Specification for Chemical Admixtures for Use in Producing Flowing
Concrete
C1116-06 Standard Specification for Fiber- Reinforced Concrete and Shotcrete
C1157-03 Standard Performance Specification for Hydraulic Cement
C1218/1218M-99 Standard Test Method for Water- Soluble Chloride in Mortar and Concrete
C1240-05 Standard Specification for Silica Fume Used in Cementitious Mixtures
C1602/C1602M-06 Standard Specification for Mixing Water Used in the Production of Hydraulic
Cement Concrete
SECTION 512 ANALYSIS AND DESIGN – GENERAL CONSIDERATIONS
512.1 DESIGN METHODS
512.1.1
In design of structural concrete, members shall be proportioned for adequate strength in
accordance with provisions of this code, using load factors and strength reduction factors φ
specified in Section 513.
512.1.2
Design of reinforced concrete using the provisions of this code shall be permitted.
512.1.3
Anchors within the scope of Appendix B installed in concrete to transfer loads between
connected elements shall be designed using Appendix B.
512.2 LOADING
512.2.1
Design provisions of this Code are based on the assumption that structures shall be designed to
resist all applicable loads.
512.2.2
Service loads shall be in accordance with the general building code of which this Code forms a
part, with such live load reductions as are permitted in the general building code.
512.2.3
In design for wind and earthquake loads, integral structural parts shall be designed to resist the
total lateral loads.
512.2.4
All rights reserved
253 / 496
Consideration shall be given to effects of forces due to prestressing, crane loads, vibration,
impact, shrinkage, temperature changes, creep, expansion of shrinkage-compensating concrete,
and unequal settlement of supports.
512.3 METHODS OF ANALYSIS
512.3.1
All members of frames or continuous construction shall be designed for the maximum effects of
factored loads as determined by the theory of elastic analysis, except as modified according to
512.4. It shall be permitted to simplify design by using the assumptions specified in 512.7
through 512.11.
512.3.2
Except for prestressed concrete, approximate methods of frame analysis shall be permitted for
buildings of usual types of construction, spans, and story heights.
512.3.3
As an alternate to frame analysis, the following approximate moments and shears shall be
permitted for design of continuous beams and one-way slabs (slabs reinforced to resist flexural
stresses in only one direction), provided (a) through (e) are satisfied:
(a) There are two or more spans;
(b) Spans are approximately equal, with the larger of two adjacent spans not greater than the
shorter by more than 20 percent;
(c) Loads are uniformly distributed;
(d) Unfactored live load, L, does not exceed three times unfactored dead load, D; and
(e) Members are prismatic.
For calculating negative moments, ln is taken as the average of the adjacent clear span lengths.
Positive moment
End spans
Discontinuous end unrestrained ..........................................................................wuln2/11
Discontinuous end integral with support …………………………………………………. wu ln2/14
Interior spans .....................................................................................................wu ln2/16
Negative moments at exterior face of first interior support
Two spans.................................................................................................................wuln2/9
More than two spans .............................................................................................wuln2/10
Negative moment at other faces of interior supports ...................................................... wu ln2/11
Negative moment at face of all supports for Slabs with spans not exceeding 3 m.; and beams
where ratio of sum of column stiffnesses to beam stiffness exceeds 8 at each end of the
span....................................................................................................................................wu ln2/12
Negative moment at interior face of exterior support for members built integrally with supports
Where support is spandrel beam ......................................................................................wu ln2/24
Where support is a column ...............................................................................................wu ln2/16
Shear in end members at face of first interior support .............................................. 1.15wu ln /2
Shear at face of all other supports .......................................................................................wu ln /2
All rights reserved
254 / 496
512.4 REDISTRIBUTION OF MOMENTS ON CONTINUOUS FLEXURAL MEMBERS
FIGURE 512.4-1 Permissible moment redistribution for minimum rotation capacity.
512.4.1
Except where approximate values for moments are used, it shall be permitted to decrease
factored moments calculated by elastic theory at sections of maximum negative or maximum
positive moment in any span of continuous flexural members for any assumed loading
arrangement by not more than 1000εt percent, with a maximum of 20 percent.
512.4.2
Redistribution of moments shall be made only when εt is equal to or greater than 0.0075 at the
section at which moment is reduced.
512.4.3
The reduced moment shall be used for calculating redistributed moments at all other sections
within the spans. Static equilibrium shall be maintained after redistribution of moments for each
loading arrangement.
512.5 MODULUS OF ELASTICITY
512.5.1
Modulus of elasticity, Ec , for concrete shall be permitted to be taken as
All rights reserved
255 / 496
wc
1.5
0.043 √
(in MPa)
for values of wc between 1440 and 2560 kg/m3. For normalweight concrete, Ec shall be
permitted to be taken as 4700 √ .
512.5.2
Modulus of elasticity, Es , for nonprestressed reinforcement shall be permitted to be taken as
200,000 MPa.
512.6 STIFFNESS
512.6.1
Use of any set of reasonable assumptions shall be permitted for computing relative flexural and
torsional stiffnesses of columns, walls, floors, and roof systems. The assumptions adopted shall
be consistent throughout analysis.
512.6.2
Effect of haunches shall be considered both in determining moments and in design of members.
512.7 EFFECTIVE STIFFNESS TO DETERMINE LATERAL DEFLECTIONS
512.7.1
Lateral deflections of reinforced concrete building systems resulting from service lateral loads
shall be computed by either a linear analysis with member stiffness determined using 1.4 times
the flexural stiffness defined in 512.7.2 and 512.7.3 or by a more detailed analysis. Member
properties shall not be taken greater than the gross section properties.
512.7.2
Lateral deflections of reinforced concrete building systems resulting from factored lateral loads
shall be computed either by linear analysis with member stiffness defined by (a) or (b), or by a
more detailed analysis considering the reduced stiffness of all members under the loading
conditions:
(a) By section properties defined in 514.10.4.1(a) through (c); or
(b) 50 percent of stiffness values based on gross section properties.
512.7.3
Where two-way slabs without beams are designated as part of the seismic-force-resisting
system, lateral deflections resulting from factored lateral loads shall be permitted to be
computed by using linear analysis. The stiffness of slab members shall be defined by a model
that is in substantial agreement with results of comprehensive tests and analysis and the
stiffness of other frame members shall be as defined in 512.7.2.
512.8 SPAN LENGTH
512.8.1
Span length of members not built integrally with supports shall be considered as the clear span
plus the depth of the member, but need not exceed distance between centers of supports.
512.8.2
In analysis of frames or continuous construction for determination of moments, span length
shall be taken as the distance center-to-center of supports.
512.8.3
All rights reserved
256 / 496
For beams built integrally with supports, design on the basis of moments at faces of support
shall be permitted.
512.8.4
It shall be permitted to analyze solid or ribbed slabs built integrally with supports, with clear
spans not more than 3 m, as continuous slabs on knife edge supports with spans equal to the
clear spans of the slab and width of beams otherwise neglected.
512.9 COLUMNS
512.9.1
Columns shall be designed to resist the axial forces from factored loads on all floors or roof and
the maximum moment from factored loads on a single adjacent span of the floor or roof under
consideration. Loading condition giving the maximum ratio of moment to axial load shall also be
considered.
512.9.2
In frames or continuous construction, consideration shall be given to the effect of unbalanced
floor or roof loads on both exterior and interior columns and of eccentric loading due to other
causes.
512.9.3
In computing gravity load moments in columns, it shall be permitted to assume far ends of
columns built integrally with the structure to be fixed.
512.9.4
Resistance to moments at any floor or roof level shall be provided by distributing the moment
between columns immediately above and below the given floor in proportion to the relative
column stiffnesses and conditions of restraint.
512.10 ARRANGEMENT OF LIVE LOAD
512.10.1
It shall be permitted to assume that:
(a) The live load is applied only to the floor or roof under consideration; and
(b) The far ends of columns built integrally with the structure are considered to be fixed.
512.10.2
It shall be permitted to assume that the arrangement of live load is limited to combinations of:
(a) Factored dead load on all spans with full factored live load on two adjacent spans; and
(b) Factored dead load on all spans with full factored live load on alternate spans.
512.11 T-BEAM CONSTRUCTION
512.11.1
In T-beam construction, the flange and web shall be built integrally or otherwise effectively
bonded together.
512.11.2
All rights reserved
257 / 496
Width of slab effective as a T-beam flange shall not exceed one-quarter of the span length of the
beam, and the effective overhanging flange width on each side of the web shall not exceed:
(a) Eight times the slab thickness; and
(b) One-half the clear distance to the next web.
512.11.3
For beams with a slab on one side only, the effective overhanging flange width shall not exceed:
(a) One-twelfth the span length of the beam;
(b) Six times the slab thickness; and
(c) One-half the clear distance to the next web.
512.11.4
Isolated beams, in which the T-shape is used to provide a flange for additional compression area,
shall have a flange thickness not less than one-half the width of web and an effective flange
width not more than four times the width of web.
512.11.5
Where primary flexural reinforcement in a slab that is considered as a T-beam flange (excluding
joist construction) is parallel to the beam, reinforcement perpendicular to the beam shall be
provided in the top of the slab in accordance with the following:
512.11.5.1
Transverse reinforcement shall be designed to carry the factored load on the overhanging
slab width assumed to act as a cantilever. For isolated beams, the full width of overhanging
flange shall be considered. For other T-beams, only the effective overhanging slab width
need be considered.
512.11.5.2
Transverse reinforcement shall be spaced not farther apart than five times the slab
thickness, nor farther apart than 450 mm.
512.12 JOIST CONSTRUCTION
512.12.1
Joist construction consists of a monolithic combination of regularly spaced ribs and a top slab
arranged to span in one direction or two orthogonal directions.
512.12.2
Ribs shall be not less than 100 mm in width, and shall have a depth of not more than 3-1/2 times
the minimum width of rib.
512.12.3
Clear spacing between ribs shall not exceed 750 mm.
512.12.4
Joist construction not meeting the limitations of 512.13.1 through 512.13.3 shall be designed as
slabs and beams.
512.12.5
When permanent burned clay or concrete tile fillers of material having a unit compressive
strength at least equal to f΄c in the joists are used:
512.12.5.1
All rights reserved
258 / 496
For shear and negative moment strength computations, it shall be permitted to include the
vertical shells of fillers in contact with the ribs. Other portions of fillers shall not be included
in strength computations.
512.12.5.2
Slab thickness over permanent fillers shall be not less than one-twelfth the clear distance
between ribs, nor less than 40 mm.
512.12.5.3
In one-way joists, reinforcement normal to the ribs shall be provided in the slab as required
by 506.12.
512.12.6
When removable forms or fillers not complying with 512.13.5 are used:
512.12.6.1
Slab thickness shall be not less than one-twelfth the clear distance between ribs, nor less
than 50 mm.
512.12.6.2
Reinforcement normal to the ribs shall be provided in the slab as required for flexure,
considering load concentrations, if any, but not less than required by 506.12.
512.12.7
Where conduits or pipes as permitted by 505.3 are embedded within the slab, slab thickness
shall be at least 25 mm greater than the total overall depth of the conduits or pipes at any point.
Conduits or pipes shall not impair significantly the strength of the construction.
512.12.8
For joist construction, Vc shall be permitted to be 10 percent more than that specified in Section
515.
512.13 SEPARATE FLOOR FINISH
512.13.1
A floor finish shall not be included as part of a structural member unless placed monolithically
with the floor slab or designed in accordance with requirements of Section 524.
512.13.2
It shall be permitted to consider all concrete floor finishes as part of required cover or total
thickness for nonstructural considerations.
SECTION 513 STRENGTH AND SERVICEABILITY
513.1 GENERAL
513.1.1
Structures and structural members shall be designed to have design strengths at all sections at
least equal to the required strengths calculated for the factored loads and forces in such
combinations as are stipulated in this code.
513.1.2
Members also shall meet all other requirements of this Code to ensure adequate performance
at service load levels.
All rights reserved
259 / 496
513.1.3
Design of structures and structural members using the load factor combinations and strength
reduction factors of this code shall be permitted. Use of load factor combinations from this
chapter in conjunction with strength reduction factors of this code shall not be permitted.
513.2 REQUIRED STRENGTH
513.2.1
Required strength U shall be at least equal to the effects of factored loads in Equations 513.2.1-1
through 513.2.1-7. The effect of one or more loads not acting simultaneously shall be
investigated.
U = 1.4(D + F )
U = 1.2(D + F + T) + 1.6(L + H) + 0.5(Lr or S or R)
U = 1.2D + 1.6(Lr or S or R) + (1.0L or 0.8W)
U = 1.2D + 1.6W + 1.0L + 0.5(Lr or S or R)
U = 1.2D + 1.0E + 1.0L + 0.2S
U = 0.9D + 1.6W + 1.6H
U = 0.9D + 1.0E + 1.6H
EQUATION 513.2.1-1
EQUATION 513.2.1-2
EQUATION 513.2.1-3
EQUATION 513.2.1-4
EQUATION 513.2.1-5
EQUATION 513.2.1-6
EQUATION 513.2.1-7
except as follows:
(a) The load factor on the live load L in Equations 513.2.1-3 to 513.2.1-5 shall be permitted to be
reduced to 0.5 except for garages, areas occupied as places of public assembly, and all areas
where L is greater than 4.8 kN/m2.
(b) Where wind load W has not been reduced by a directionality factor, it shall be permitted to
use 1.3W in place of 1.6W in Equations 513.2.1-4 and 513.2.1-6.
(c) Where E, the load effects of earthquake, is based on service-level seismic forces, 1.4E shall
be used in place of 1.0E in Equations 513.2.1-5 and 513.2.1-7.
(d) The load factor on H, loads due to weight and pressure of soil, water in soil, or other
materials, shall be set equal to zero in Equations 513.2.1-6 and 513.2.1-7 if the structural
action due to H counteracts that due to W or E. Where lateral earth pressure provides
resistance to structural actions from other forces, it shall not be included in H but shall be
included in the design resistance.
513.2.2
If resistance to impact effects is taken into account in design, such effects shall be included with
L.
513.2.3
Estimations of differential settlement, creep, shrinkage, expansion of shrinkage-compensating
concrete, or temperature change shall be based on a realistic assessment of such effects
occurring inservice.
513.3 DESIGN STRENGTH
513.3.1
Design strength provided by a member, its connections to other members, and its cross sections,
in terms of flexure, axial load, shear, and torsion, shall be taken as the nominal strength
calculated in accordance with requirements and assumptions of this Code, multiplied by the
strength reduction factors φ in 513.3.2, 513.3.4, and 513.3.5.
All rights reserved
260 / 496
513.3.2
Strength reduction factor φ shall be as given in 5139.3.2.1 through 513.3.2.7:
FIGURE 513.3.2-1—Variation of φ with net tensile strain in extreme tension steel, εt, and c /dt for
Grade 420 reinforcement and for prestressing steel.
513.3.2.1
Tension-controlled sections as defined in 514.3.4 ..........................................................0.90
(See also 513.3.2.7)
513.3.2.2
Compression-controlled sections, as defined in 514.3.3:
(a) Members with spiral reinforcement conforming to 514.9.3.....................................0.75
(b) Other reinforced members ...........................................................................................0.65
For sections in which the net tensile strain in the extreme tension steel at nominal strength,
εt, is between the limits for compression-controlled and tension-controlled sections, φ shall
be permitted to be linearly increased from that for compression-controlled sections to 0.90
as εt increases from the compressioncontrolled strain limit to 0.005.
Alternatively, for members in which fy does not exceed 420 MPa, with symmetric
reinforcement, and with (d – d′)/h not less than 0.70, φ shall be permitted to be increased
linearly to 0.90 as φPn decreases from 0.10f΄cAg to zero. For other reinforced members, φ
shall be permitted to be increased linearly to 0.90 as φPn decreases from 0.10f΄cAg or φPb ,
whichever is smaller, to zero.
513.3.2.3
Shear and torsion ..............................................................................................................0.75
513.3.2.4
Bearing on concrete (except for post-tensioned anchorage zones and strut-and-tie models)
...........................................................................................................................................0.65
513.3.2.5
Strut-and-tie models, and struts, ties, nodal zones, and bearing areas in such models
..........................................................................................................................................0.75
513.3.3
Development lengths specified in Section 516 do not require a φ-factor.
513.3.4
All rights reserved
261 / 496
For structures that rely on intermediate precast structural walls in Seismic Design Category D,E,
or F, special moment frames, or special structural walls to resist earthquake effects, E, φ shall be
modified as given in (a) through (c):
(a) For any structural member that is designed to resist E, φ for shear shall be 0.60 if the nominal
shear strength of the member is less than the shear corresponding to the development of the
nominal flexural strength of the member. The nominal flexural strength shall be determined
considering the most critical factored axial loads and including E;
(b) For diaphragms, φ for shear shall not exceed the minimum φ for shear used for the vertical
components of the primary seismic-force-resisting system;
(c) For joints and diagonally reinforced coupling beams, φ for shear shall be 0.85.
513.3.5
In Section 507, φ shall be 0.60 for flexure, compression, shear, and bearing of structural plain
concrete.
513.4 DESIGN STRENGTH FOR REINFORCEMENT
The values of fy and fyt used in design calculations shall not exceed 550 MPa, except for prestressing
steel and for transverse reinforcement in 514.9.3 and 521.1.5.4.
513.5 CONTROL OF DEFLECTIONS
513.5.1
Reinforced concrete members subjected to flexure shall be designed to have adequate stiffness
to limit deflections or any deformations that adversely affect strength or serviceability of a
structure.
513.5.2 ONE-WAY CONSTRUCTION (NONPRESTRESSED)
513.5.2.1
Minimum thickness stipulated in Table 513.5.2.2-1 shall apply for one-way construction not
supporting or attached to partitions or other construction likely to be damaged by large
deflections, unless computation of deflection indicates a lesser thickness can be used
without adverse effects.
513.5.2.2
Where deflections are to be computed, deflections that occur immediately on application of
load shall be computed by usual methods or formulas for elastic deflections, considering
effects of cracking and reinforcement on member stiffness.
TABLE 513.5.2.2-1 MINIMUM THICKNESS OF NONPRESTRESSED BEAMS OR ONE-WAY SLABS UNLESS
DEFLECTIONS ARE CALCULATED
Minimum thickness, h
Simply supported One end continuous Both ends continuous
Cantilever
Members not supporting or attached to partitions or other construction likely
Member
to be damaged by large deflections
Solid one- way slabs
l/20
l/24
l/28
l/10
Beams or ribbed oneway slabs
l/16
l/18.5
l/21
l/8
Notes:
Values given shall be used directly for members with normalweight concrete and Grade 420
reinforcement. For other conditions, the values shall be modified as follows:
All rights reserved
262 / 496
3
a) For lightweight concrete having equilibrium density, wc , in the range of 1440 to 1840 kg/m , the
values shall be multiplied by (1.65 – 0.0003wc) but not less than 1.09.
b) For fy other than 420 MPa, the values shall be multiplied by (0.4 + fy/700).
513.5.2.3
Unless stiffness values are obtained by a more comprehensive analysis, immediate
deflection shall be computed with the modulus of elasticity for concrete, Ec, as specified in
512.5.1 (normalweight or lightweight concrete) and with the effective moment of inertia, Ie,
as follows, but not greater than Ig
Ie = (Mcr/ Ma)3 Ig+[1-( Mcr/ Ma)3] Icr
EQUATION 513.5.2.3-1
Where
Mcr= fr Ig/ yt
EQUATION 513.5.2.3-2
and
fr = 0.62λ √
EQUATION 513.5.2.3-13
513.5.2.4
For continuous members, Ie shall be permitted to be taken as the average of values
obtained from Eq. (9-8) for the critical positive and negative moment sections. For prismatic
members, Ie shall be permitted to be taken as the value obtained from Equation 513.5.2.3-1
at midspan for simple and continuous spans, and at support for cantilevers.
513.5.2.5
Unless values are obtained by a more comprehensive analysis, additional long-term
deflection resulting from creep and shrinkage of flexural members shall be determined by
multiplying the immediate deflection caused by the sustained load considered, by the factor
λΔ
λΔ= ξ/(1 + 50ρ′)
EQUATION 513.5.2.5-1
where ρ′ shall be the value at midspan for simple and continuous spans, and at support for
cantilevers. It shall be permitted to assume ξ, the time-dependent factor for sustained loads,
to be equal to:
5 years or more ....................................................... 2.0
12 months................................................................ 1.4
6 months.................................................................. 1.2
3 months.................................................................. 1.0
All rights reserved
263 / 496
FIGURE 513.5.2.5-1 Multipliers for long-term deflections.
513.5.2.6
Deflection computed in accordance with 513.5.2.2 through 513.5.2.5 shall not exceed limits
stipulated in Table 513.5.3.1-1.
513.5.3 TWO-WAY CONSTRUCTION (NONPRESTRESSED)
513.5.3.1
Section 513.5.3 shall govern the minimum thickness of slabs or other two-way construction
designed in accordance with the provisions of Section 517 and conforming with the
requirements of 517.6.1.2. The thickness of slabs without interior beams spanning between
the supports on all sides shall satisfy the requirements of 513.5.3.2 or 9.5.3.4. The thickness
of slabs with beams spanning between the supports on all sides shall satisfy requirements of
513.5.3.3 or 513.5.3.4.
TABLE 513.5.3.1-1 — MAXIMUM PERMISSIBLE COMPUTED DEFLECTIONS
Type of member
Flat roofs not supporting or
attached
to
nonstructural
elements likely to be damaged
by large deflections
Floors not supporting or
attached
to
nonstructural
elements likely to be damaged
by large deflections
Roof or floor construction
supporting or attached to
nonstructural elements likely to
be damaged by large deflections
Roof or floor construction
supporting or attached to
nonstructural elements not likely
to be damaged by large
deflections
All rights reserved
Immediate deflection due to live load L
Deflection
limitation
l /180a
Immediate deflection due to live load L
l /360
That part of the total deflection occurring after
attachment of nonstructural elements (sum of
the long-term deflection due to all sustained
loads and the immediate deflection due to any
additional live load)b
l /480c
Deflection to be considered
l /240d
264 / 496
a: Limit not intended to safeguard against ponding. Ponding should be checked by suitable calculations
of deflection, including added deflections due to ponded water, and considering long-term effects
of all sustained loads, camber, construction tolerances, and reliability of provisions for drainage.
b: Long-term deflection shall be determined in accordance with 513.5.2.5 or 513.5.4.3, but may be
reduced by amount of deflection calculated to occur before attachment of nonstructural elements.
This amount shall be determined on basis of accepted engineering data relating to time-deflection
characteristics of members similar to those being considered.
c: Limit may be exceeded if adequate measures are taken to prevent damage to supported or attached
elements.
d: Limit shall not be greater than tolerance provided for nonstructural elements. Limit may be
exceeded if camber is provided so that total deflection minus camber does not exceed limit.
513.5.3.2
For slabs without interior beams spanning between the supports and having a ratio of long
to short span not greater than 2, the minimum thickness shall be in accordance with the
provisions of Table 9.5(c) and shall not be less than the following values:
(a) Slabs without drop panels as defined in 517.2.5...............................................125 mm;
(b) Slabs with drop panels as defined in 517.2.5 .................................................. 100 mm.
513.5.3.3
For slabs with beams spanning between the supports on all sides, the minimum thickness, h,
shall be as follows:
(a) For αfm equal to or less than 0.2, the provisions of 513.5.3.2 shall apply;
(b) For αfm greater than 0.2 but not greater than 2.0, h shall not be less than
h=( ln 0.8+ fy/1400)/( 36 + 5β(αfm – 0.2))
EQUATION 513.5.3.3-1
and not less than 125 mm;
(c) For αfm greater than 2.0, h shall not be less than
h=( ln 0.8+ fy/1400)/( 36 + 9β)
EQUATION 513.5.3.3-2
and not less than 90 mm;
(d) At discontinuous edges, an edge beam shall be provided with a stiffness ratio αf not less
than 0.80 or the minimum thickness required by Equation 513.5.3.3-1 or 513.5.3.3-2
9
TABLE 513.5.3.3-1 MINIMUM THICKNESS OF SLABS WITHOUT INTERIOR BEAMS
fy , MPab
280
420
520
Without drop panelsc
Interior
Exterior panels
panels
Without
With edge
beamsd
edge beams
ln /33
ln /36
ln /36
ln /30
ln /33
ln /33
ln /28
ln /31
ln /31
With drop panelsc
Interior panels
Exterior panels
Without edge With edge
beamsd
beams
ln /36
ln /40
ln /40
ln /33
ln /36
ln /36
ln /31
ln /34
ln /34
a: For two-way construction, ln is the length of clear span in the long direction, measured face-to-face
of supports in slabs without beams and face-to-face of beams or other supports in other cases.
b: For fy between the values given in the table, minimum thickness shall be determined by linear
interpolation.
All rights reserved
265 / 496
c: Drop panels as defined in 517.2.5.
d: Slabs with beams between columns along exterior edges. The value of αf for the edge beam shall
not be less than 0.8.
shall be increased by at least 10 percent in the panel with a discontinuous edge.
Term ln in (b) and (c) is length of clear span in long direction measured face-to-face of beams. Term β
in (b) and (c) is ratio of clear spans in long to short direction of slab.
513.5.3.4
Slab thickness less than the minimum required by 513.5.3.1, 513.5.3.2, and 513.5.3.3 shall
be permitted where computed deflections do not exceed the limits of Table 513.5.3.1-1.
Deflections shall be computed taking into account size and shape of the panel, conditions of
support, and nature of restraints at the panel edges. The modulus of elasticity of concrete,
Ec , shall be as specified in 512.5.1. The effective moment of inertia, Ie , shall be that given by
Equation 513.5.2.3-1; other values shall be permitted to be used if they result in computed
deflections in reasonable agreement with results of comprehensive tests. Additional longterm deflection shall be computed in accordance with 513.5.2.5.
513.5.4
Deflection computed in accordance with 513.5.4.1 or 513.5.4.2, and 513.5.4.3 shall not exceed
limits stipulated in Table 513.5.3.1-1.
513.5.5 COMPOSITE CONSTRUCTION
513.5.5.1 SHORED CONSTRUCTION
If composite flexural members are supported during construction so that, after removal of
temporary
supports, dead load is resisted by the full composite section, it shall be permitted to
consider the composite member equivalent to a monolithically cast member for
computation of deflection. For nonprestressed members, the portion of the member in
compression shall determine whether values in Table 513.5.2.2-1 for normalweight or
lightweight concrete shall apply. If deflection is computed, accou shall be taken of
curvatures resulting from differential shrinkage ofpr ecast and cast-in-place components,
and of axial creep effects in a prestressed concrete member.
513.5.5.2 UNSHORED CONSTRUCTION
If the thickness of a nonprestressed precast flexural member meets the requirements of
Table 513.5.2.2-1, deflection need not be computed. If the thickness of a nonprestressed
composite member meets the requirements of Table 513.5.2.2-1, it is not required to
compute deflection occurring after the member becomes composite, but the long-term
deflection of the precast member shall be investigated for magnitude and duration of load
prior to beginning of effective composite action.
513.5.5.3
Deflection computed in accordance with 513.5.5.1 or 513.5.5.2 shall not exceed limits
stipulated in Table 513.5.3.1-1.
SECTION 514 FLEXURE AND AXIAL LOADS
514.1 SCOPE
Provisions of this section shall apply for design of members subject to flexure or axial loads or to
combined flexure and axial loads.
514.2 DESIGN ASSUMPTIONS
All rights reserved
266 / 496
514.2.1
Strength design of members for flexure and axial loads shall be based on assumptions given in
514.2.2 through 514.2.7, and on satisfaction of applicable conditions of equilibrium and
compatibility of strains.
514.2.2
Strain in reinforcement and concrete shall be assumed directly proportional to the distance from
the neutral axis, except that, for deep beams as defined in 514.7.1, an analysis that considers a
nonlinear distribution of strain shall be used
514.2.3
Maximum usable strain at extreme concrete compression fiber shall be assumed equal to 0.003.
For deformed reinforcement, it is reasonably accurate to assume that the stress in
reinforcement is
proportional to strain below the specified yield strength fy. The increase in strength due to the
effect of strain hardening of the reinforcement is neglected for strength computations. In
strength computations, the force developed in tensile or compressive reinforcement is
computed as:
when εs < εy (yield strain)
As fs = AsEsεs
when εs ≥ εy
As fs = As fy
514.2.4
Tensile strength of concrete shall be neglected in axial and flexural calculations of reinforced
concrete.
514.2.5
The relationship between concrete compressive stress distribution and concrete strain
shall be assumed to be rectangular, trapezoidal, parabolic, or any other shape that results in
prediction of strength in substantial agreement with results of comprehensive tests.
514.2.6
Requirements of 514.2.6 are satisfied by an equivalent rectangular concrete stress distribution
defined by the following:
514.2.6.1
Concrete stress of 0.85f΄c shall be assumed uniformly distributed over an equivalent
compression zone bounded by edges of the cross section and a straight line located parallel
to the neutral axis at a distance a = β1c from the fiber of maximum compressive strain.
514.2.6.2
Distance from the fiber of maximum strain to the neutral axis, c, shall be measured in a
direction perpendicular to the neutral axis.
514.2.6.3
All rights reserved
267 / 496
For f΄c between 17 and 28 M a, β1 shall be taken as 0.85. For f΄c above 28 M a, β1 shall be
reduced linearly at a rate of 0.05 for each 7 M a of strength in excess of 28 M a, but β1 shall
not be taken less than 0.65.
514.3 GENERAL PRINCIPLES AND REQUIREMENTS
514.3.1
Design of cross sections subject to flexure or axial loads, or to combined flexure and axial loads,
shall be based on stress and strain compatibility using assumptions in 514.2.
514.3.2
Balanced strain conditions exist at a cross section when tension reinforcement reaches the strain
corresponding to fy just as concrete in compression reaches its assumed ultimate strain of 0.003.
514.3.3
Sections are compression-controlled if the net tensile strain in the extreme tension steel, εt, is
equal to or less than the compression-controlled strain limit when the concrete in compression
reaches its assumed strain limit of 0.003. The compressioncontrolled strain limit is the net
tensile strain in the reinforcement at balanced strain conditions. For Grade 420 reinforcement,
and for all prestressed reinforcement, it shall be permitted to set the compression-controlled
strain limit equal to 0.002.
FIGURE 514.3.3-1 Strain distribution and net tensile strain.
514.3.4
Sections are tension-controlled if the net tensile strain in the extreme tension steel, εt, is equal
to or greater than 0.005 when the concrete in compression reaches its assumed strain limit of
0.003. Sections with εt between the compression-controlled strain limit and 0.005 constitute a
transition region between compression-controlled and tension-controlled sections.
514.3.5
For nonprestressed flexural members and nonprestressed members with factored axial
compressive load less than 0.10 f΄c Ag, εt at nominal strength shall not be less than 0.004.
514.3.5.1
All rights reserved
268 / 496
Use of compression reinforcement shall be permitted in conjunction with additional tension
reinforcement to increase the strength of flexural members.
514.3.6
Design axial strength φPn of compression members shall not be taken greater than φPn,max,
computed by Equation 514.3.6.1-1 or 514.3.6.2-1.
514.3.6.1
For nonprestressed members with spiral reinforcement conforming to 506.10.4 or
composite members conforming to 514.13:
φPn,max = 0.85φ [0.85 f΄c (Ag – Ast) + fyAst ] EQUATION 514.3.6.1-1
514.3.6.2
For nonprestressed members with tie reinforcement conforming to 506.10.5:
φPn,max = 0.80φ [0.85 f΄c (Ag – Ast) + fyAst ] EQUATION 514.3.6.1-1
514.3.6.3
A simple and somewhat conservative estimate of nominal strength Pni can be obtained from
the reciprocal load relationship.
where:
Pni = nominal axial load strength at given eccentricity along both axes
Po = nominal axial load strength at zero eccentricity
Pnx = nominal axial load strength at given eccentricity along x-axis
Pny = nominal axial load strength at given eccentricity along y-axis
This relationship is most suitable when values Pnx and Pny are greater than the balanced
axial force Pb for the particular axis.
514.3.7
Members subject to compressive axial load shall be designed for the maximum moment that can
accompany the axial load. The factored axial force Pu at given eccentricity shall not exceed that
given in 514.3.6. The maximum factored moment Mu shall be magnified for slenderness effects
in accordance with 514.10.
514.4 DISTANCE BETWEEN LATERAL SUPPORTS OF FLEXURAL MEMBERS
514.4.1
Spacing of lateral supports for a beam shall not exceed 50 times b, the least width of
compression flange or face.
514.4.2
Effects of lateral eccentricity of load shall be taken into account in determining spacing of lateral
supports.
514.5 MINIMUM REINFORCEMENT OF FLEXURAL MEMBERS
514.5.1
All rights reserved
269 / 496
At every section of a flexural member where tensile reinforcement is required by analysis,
except as provided in 514.5.2, 514.5.3, and 514.5.4, As provided shall not be less than that given
by
)/fy] bwd
EQUATION 514.5.1-1
As, min=[(0.25 √
and not less than 1.4bwd/fy.
514.5.2
For statically determinate members with a flange in tension, As,min shall not be less than the
value given by Equation 514.5.1-1, except that bw is replaced by either 2bw or the width of the
flange, whichever is smaller.
514.5.3
The requirements of 514.5.1 and 514.5.2 need not be applied if, at every section, As provided is
at least one-third greater than that required by analysis.
514.5.4
For structural slabs and footings of uniform thickness, As,min in the direction of the span shall be
the same as that required by 506.12.2.1. Maximum spacing of this reinforcement shall not
exceed three times the thickness, nor 450 mm.
514.6 DISTRIBUTION OF FLEXURAL REINFORCEMENT ON BEAMS AND ONE-WAY SLABS
514.6.1
This section prescribes rules for distribution of flexural reinforcement to control flexural cracking
in beams and in one-way slabs (slabs reinforced to resist flexural stresses in only one direction).
514.6.2
Distribution of flexural reinforcement in twoway slabs shall be as required by 517.3.
514.6.3
Flexural tension reinforcement shall be well distributed within maximum flexural tension zones
of a member cross section as required by 514.6.4.
514.6.4
The spacing of reinforcement closest to the tension face, s, shall not exceed that given by
s =380(280/fs) – 2.5cc
EQUATION 514.6.4-1
but not greater than 300(280/fs), where cc is the least distance from surface of reinforcement or
prestressing steel to the tension face. If there is only one bar or wire nearest to the extreme
tension face, s used in Equation 514.6.4-1 is the width of the extreme tension face. Calculated
stress fs in reinforcement closest to the tension face at service load shall be computed based on
the unfactored moment. It shall be permitted to take fs as 2/3fy.
514.6.5
Provisions of 514.6.4 are not sufficient for structures subject to very aggressive exposure or
designed to be watertight. For such structures, special investigations and precautions are
required.
514.6.6
All rights reserved
270 / 496
Where flanges of T-beam construction are in tension, part of the flexural tension reinforcement
shall be distributed over an effective flange width as defined in 512.12, or a width equal to onetenth the span, whichever is smaller. If the effective flange width exceeds one-tenth the span,
some longitudinal reinforcement shall be provided in the outer portions of the flange.
514.6.7
Where h of a beam or joist exceeds 900 mm, longitudinal skin reinforcement shall be uniformly
distributed along both side faces of the member. Skin reinforcement shall extend for a distance
h/2 from the tension face. The spacing s shall be as provided in 10.6.4, where cc is the least
distance from the surface of the skin reinforcement or prestressing steel to the side face. It shall
be permitted to include such reinforcement in strength computations if a strain compatibility
analysis is made to determine stress in the individual bars or wires.
FIGURE 514.6.7-1 Skin reinforcement for beams and joists with h > 900 mm.
514.7 DEEP BEAMS
514.7.1
Deep beams are members loaded on one face and supported on the opposite face so that
compression struts can develop between the loads and the supports, and have either:
(a) clear spans, ln, equal to or less than four times the overall member depth; or
(b) regions with concentrated loads within twice the member depth from the face of the
support.
Deep beams shall be designed either taking into account nonlinear distribution of strain.
(See also 515.9.1 and 516.9.6.) Lateral buckling shall be considered.
514.7.2
Vn of deep beams shall be in accordance with 515.9.
514.7.3
All rights reserved
271 / 496
Minimum area of flexural tension reinforcement, As,min, shall conform to 514.5.
514.7.4
Minimum horizontal and vertical reinforcement in the side faces of deep beams shall satisfy
either 515.9.4 and 515.9.5.
514.8 DESIGN DIMENSIONS FOR COMPRESSION MEMBERS
514.8.1 ISOLATED COMPRESSION MEMBER WITH MULTIPLE SPIRALS
Outer limits of the effective cross section of a compression member with two or more
interlocking spirals shall be taken at a distance outside the extreme limits of the spirals equal to
the minimum
concrete cover required by 506.7.
514.8.2 COMPRESSION MEMBER BUILT MONOLITHICALLY WITH WALL
Outer limits of the effective cross section of a spirally reinforced or tied reinforced compression
member built monolithically with a concrete wall or pier shall be taken not greater than 40 mm
outside the spiral or tie reinforcement.
514.8.3 EQUIVALENT CIRCULAR COMPRESSION MEMBER
As an alternative to using the full gross area for design of a compression member with a square,
octagonal, or other shaped cross section, it shall be permitted to use a circular section with a
diameter equal to the least lateral dimension of the actual shape. Gross area considered,
required percentage of reinforcement, and design strength shall be based on that circular
section.
514.8.4 LIMITS OF SECTION
For a compression member with a cross section larger than required by considerations of
loading, it shall be permitted to base the minimum reinforcement and strength on a reduced
effective area Ag not less than one-half the total area. This provision shall not apply to special
moment frames or special structural walls designed in accordance with Section 521.
514.9 LIMITS FOR REINFORCEMENT OF COMPRESSION MEMBERS
514.9.1
Area of longitudinal reinforcement, Ast, for noncomposite compression members shall be not
less than 0.01Ag or more than 0.08Ag.
514.9.2
Minimum number of longitudinal bars in compression members shall be 4 for bars within
rectangular or circular ties, 3 for bars within triangular ties, and 6 for bars enclosed by spirals
conforming to 514.9.3.
514.9.3
Volumetric spiral reinforcement ratio, ρs , shall be not less than the value given by
ρs= 0.45(Ag/ Ach– 1)( f΄c /fyt)
EQUATION 514.9.3-1 (10-5)
where the value of fyt used in Equation 514.9.3-1
All rights reserved
272 / 496
shall not exceed 700 MPa. For fyt greater than 420 MPa, lap splices according to 506.10.4.5(a)
shall not be used.
514.10 SLENDERNESS EFFECTS IN COMPRESSION MEMBERS
514.10.1
Slenderness effects shall be permitted to be neglected in the following cases:
(a) for compression members not braced against sidesway when:
klu/ r ≤ 22
EQUATION 514.10.1-1
(b) for compression members braced against sidesway when:
klu ≤ 34 – 12(M1/M2) ≤ 40
EQUATION 514.10.1-2
where M1/M2 is positive if the column is bent in single curvature, and negative if the member is
bent in double curvature. It shall be permitted to consider compression members braced against
sidesway when bracing elements have a total stiffness, resisting lateral movement of that story,
of at least 12 times the gross stiffness of the columns within the story.
FIGURE 514.10.1-1 Effective length factors k.
514.10.1.1
The unsupported length of a compression member, lu, shall be taken as the clear distance
between floor slabs, beams, or other members capable of providing lateral support in the
direction being considered. Where column capitals or haunches are present, lu shall be
measured to the lower extremity of the capital or haunch in the plane considered.
514.10.1.2
All rights reserved
273 / 496
It shall be permitted to take the radius of gyration, r, equal to 0.30 times the overall
dimension in the direction stability is being considered for rectangular compression
members and 0.25 times the diameter for circular compression members. For other shapes,
it shall be permitted to compute r for the gross concrete section.
514.10.2
When slenderness effects are not neglected as permitted by 514.10.1, the design of
compression members, restraining beams, and other supporting members shall be based on the
factored forces and moments from a second-order analysis satisfying 514.10.3, 514.10.4, or
514.10.5. These members shall also satisfy 514.10.2.1 and 514.10.2.2. The dimensions of each
member cross section used in the analysis shall be within 10 percent of the dimensions of the
members shown on the design drawings or the analysis shall be repeated.
514.10.2.1
Total moment including second-order effects in compression members, restraining beams,
or other structural members shall not exceed 1.4 times the moment due to first-order
effects.
514.10.2.2
Second-order effects shall be considered along the length of compression members. It shall
be permitted to account for these effects using the moment magnification procedure
outlined in 514.10.6.
514.10.3 NONLINEAR SECOND-ORDER ANALYSIS
Second-order analysis shall consider material nonlinearity, member curvature and lateral
drift, duration of loads, shrinkage and creep, and interaction with the supporting
foundation. The analysis procedure shall have been shown to result in prediction of strength
in substantial agreement with results of comprehensive tests of columns in statically
indeterminate reinforced concrete structures.
514.10.4 ELASTIC SECOND-ORDER ANALYSIS
Elastic second-order analysis shall consider section properties determined taking into
account the influence of axial loads, the presence of cracked regions along the length of the
member, and the effects of load duration.
514.10.4.1
It shall be permitted to use the following properties for the members in the structure:
(a) Modulus of elasticity ...................... Ec from 512.5.1
(b) Moments of inertia, I
Compression members:
Columns.................................................... 0.70Ig
Walls
—Uncracked.............................................. 0.70Ig
—Cracked ................................................. 0.35Ig
Flexural members:
Beams....................................................... 0.35Ig
Flat plates and flat slabs ............................. 0.25Ig
(c) Area ..................................................... 1.0Ag
Alternatively, the moments of inertia of compression and flexural members, I, shall be
permitted to be computed as follows:
Compression members:
All rights reserved
274 / 496
I=(0.80+25 Ast/ Ag)(1- (Mu/ Puh )-0.5 (Pu/ Po)) Ig ≤0.875Ig
EQUATION 514.10.4.1-1
where Pu and Mu shall be determined from the particular load combination under
consideration, or
the combination of Pu and Mu determined in the smallest value of I. I need not be taken
less than 0.35Ig.
Flexural members:
I =(0.10 + 25ρ)[ 1.2-0.2( bw/ d)] Ig ≤ 0.5Ig
EQUATION 514.10.4-2
For continuous flexural members, I shall be permitted to be taken as the average of
values obtained from Equation 514.10.4-2 for the critical positive and negative moment
sections. I need not be taken less than 0.25Ig.
The cross-sectional dimensions and reinforcement ratio used in the above formulas shall
be within 10 percent of the dimensions and reinforcement ratio shown on the design
drawings or the stiffness evaluation shall be repeated.
514.10.4.2
When sustained lateral loads are present, I for compression members shall be divided by
(1 + βds). The term βds shall be taken as the ratio of maximum factored sustained shear
within a story to the maximum factored shear in that story associated with the same
load combination, but shall not be taken greater than 1.0.
514.10.5 MOMENT MAGNIFICATION PROCEDURE
Columns and stories in structures shall be designated as nonsway or sway columns or stories.
The design of columns in nonsway frames or stories shall be based on 514.10.6. The design of
columns in sway frames or stories shall be based on 514.10.7.
514.10.5.1
It shall be permitted to assume a column in a structure is nonsway if the increase in column
end moments due to second-order effects does not exceed 5 percent of the first-order end
moments.
514.10.5.2
It also shall be permitted to assume a story within a structure is nonsway if:
Q= (ΣPuΔo/Vuslc) ≤ 0.05
EQUATION 514.10.5.2-1
where ΣPu and Vus are the total factored vertical load and the horizontal story shear,
respectively, in the story being evaluated, and Δo is the first-order relative lateral deflection
between the top and the bottom of that story due to Vus .
514.10.6 MOMENT MAGNIFICATION PROCEDURE - NONSWAY
Compression members shall be designed for factored axial force Pu and the factored moment
amplified for the effects of member curvature Mc where
Mc = δnsM2
All rights reserved
EQUATION 514.10.6-1
275 / 496
where
δns= Cm/(1 – (Pu/0.75Pc)) ≥ 1.0
EQUATION 514.10.6-2
and
Pc= π2EI/(klu)2
EQUATION 514.10.6-3
514.10.6.1
EI shall be taken as
EI= (0.2EcIg + EsIse)/ (1 + βdns)
EQUATION 514.10.6.1-1
or
EI= 0.4EcIg)/ (1 + βdns)
EQUATION 514.10.6.1-2
Alternatively, EI shall be permitted to be computed using the value of I from Equation
514.10.4-1 divided by
(1 + βdns ).
514.10.6.2
The term βdns shall be taken as the ratio of maximum factored axial sustained load to
maximum factored axial load associated with the same load combination, but shall not be
taken greater than 1.0.
514.10.6.3
The effective length factor, k, shall be permitted to be taken as 1.0.
514.10.6.4
For members without transverse loads between supports, Cm shall be taken as
Cm= 0.6 + 0.4 M1/M2
EQUATION 514.10.6.4-1
where M1/M2 is positive if the column is bent in single curvature, and negative if the
member is bent in double curvature. For members with transverse loads between supports,
Cm shall be taken as 1.0.
514.10.6.5
Factored moment, M2, in Equation 514.10.6-1 shall not be taken less than
M2,min = Pu(0.6 + 0.03h)
EQUATION 514.10.6.5-1
about each axis separately, where 0.6 and h are in inches. For members in which M2,min
exceeds M2, the value of Cm in Equation 514.10.6.4-1 shall either be taken equal to 1.0, or
shall be based on the ratio of the computed end moments, M1/M2.
514.10.7 MOMENT MAGNIFICATION PROCEDURE - SWAY
Moments M1 and M2 at the ends of an individual compression member shall be taken as
All rights reserved
276 / 496
M1 = M1ns + δsM1s
EQUATION 514.10.7-1
M2 = M2ns + δsM2s
EQUATION 514.10.7-2
where δs is computed according to 514.10.7.3 or 514.10.7.4.
514.10.7.1
Flexural members shall be designed for the total magnified end moments of the
compression members at the joint.
514.10.7.2
The effective length factor k shall be determined using the values of Ec and I given in
514.10.4 and shall not be less than 1.0.
514.10.7.3
The moment magnifier δs shall be calculated as
δs=1/(1 – Q) ≥ 1
EQUATION 514.10.7.3-1
If δs calculated by Equation 514.10.7.3-1 exceeds 1.5, δs shall be calculated using secondorder elastic analysis or 514.10.7.4.
514.10.7.4
Alternatively, it shall be permitted to calculate δs as
δs=1/(1-(ΣPu/0.75ΣPc)) ≥ 1
EQUATION 514.10.7.4-1
where ΣPu is the summation for all the factored vertical loads in a story and ΣPc is the
summation for
all sway-resisting columns in a story. Pc is calculated using Equation 514.10.6-3 with k
determined from 514.10.7.2 and EI from 514.10.6.1.
514.11 AXIALLY LOADED MEMBERS SUPPORTING SLAB SYSTEM
Axially loaded members supporting a slab system included within the scope of 517.1 shall be designed
as provided in Section 514 and in accordance with the additional requirements of Section 517.
514.12 TRANSMISSION OF COLUMN LOADS THROUGH FLOOR SYSTEM
If f’c of a column is greater than 1.4 times that of the floor system, transmission of load through the
floor system shall be provided by 514.12.1, 514.12.2, or 514.12.3.
514.12.1
Concrete of strength specified for the column shall be placed in the floor at the column location.
Top surface of the column concrete shall extend 600 mm into the slab from face of column.
Column concrete shall be well integrated with floor concrete, and shall be placed in accordance
with 505.4.6 and 505.4.7.
514.12.2
Strength of a column through a floor system shall be based on the lower value of concrete
strength with vertical dowels and spirals as required.
514.12.3
For columns laterally supported on four sides by beams of approximately equal depth or by
slabs, it shall be permitted to base strength of the column on an assumed concrete strength in
the column joint equal to 75 percent of column concrete strength plus 35 percent of floor
All rights reserved
277 / 496
concrete strength. In the application of 514.12.3, the ratio of column concrete strength to slab
concrete strength shall not be taken greater than 2.5 for design.
514.13 COMPOSITE COMPRESSION MEMBERS
514.13.1
Composite compression members shall include all such members reinforced longitudinally with
structural steel shapes, pipe, or tubing with or without longitudinal bars.
514.13.2
Strength of a composite member shall be computed for the same limiting conditions applicable
to ordinary reinforced concrete members.
514.13.3
Any axial load strength assigned to concrete of a composite member shall be transferred to the
concrete by members or brackets in direct bearing on the composite member concrete.
514.13.4
All axial load strength not assigned to concrete of a composite member shall be developed by
direct connection to the structural steel shape, pipe, or tube.
514.13.5
For evaluation of slenderness effects, radius of gyration, r, of a composite section shall be not
greater than the value given by
r= √
(
)
(
)
EQUATION 514.13.5-1
and, as an alternative to a more accurate calculation, EI in Equation 514.10.6-3 shall be taken
either as Equation 514.10.6.1-1 or
EI =
(
)
EQUATION 514.13.5-2
514.13.6 STRUCTURAL STEEL ENCASED CONCRETE CORE
514.13.6.1
For a composite member with a concrete core encased by structural steel, the thickness of
the steel encasement shall be not less than
b√
for each face of width b
nor
b√
for circular sections of diameter h
514.13.6.2
Longitudinal bars located within the encased concrete core shall be permitted to be used in
computing Asx and Isx.
514.13.7
A composite member with spirally reinforced concrete around a structural steel core shall
All rights reserved
278 / 496
conform to 514.13.7.1 through 514.13.7.4.
514.13.7.1
Design yield strength of structural steel core shall be the specified minimum yield strength
for the grade of structural steel used but not to exceed 350 MPa.
514.13.7.2
Spiral reinforcement shall conform to 514.9.3.
514.13.7.3
Longitudinal bars located within the spiral shall be not less than 0.01 nor more than 0.08
times net area of concrete section.
514.13.7.4
Longitudinal bars located within the spiral shall be permitted to be used in computing Asx
and Isx .
514.13.8
A composite member with laterally tied concrete around a structural steel core shall
conform to 514.13.8.1 through 514.13.8.7.
514.13.8.1
Design yield strength of structural steel core shall be the specified minimum yield strength
for the grade of structural steel used but not to exceed 350 MPa.
514.13.8.2
Lateral ties shall extend completely around the structural steel core.
514.13.8.3
Lateral ties shall have a diameter not less than 0.02 times the greatest side dimension of
composite member, except that ties shall not be smaller than No. 10 and are not required to
be larger than No. 16. Welded wire reinforcement of equivalent area shall be permitted.
514.13.8.4
Vertical spacing of lateral ties shall not exceed 16 longitudinal bar diameters, 48 tie bar
diameters, or 0.5 times the least side dimension of the composite member.
514.13.8.5
Longitudinal bars located within the ties shall be not less than 0.01 nor more than 0.08 times
net area of concrete section.
514.13.8.6
A longitudinal bar shall be located at every corner of a rectangular cross section, with other
longitudinal bars spaced not farther apart than one- half the least side dimension of the
composite member.
514.13.8.7
Longitudinal bars located within the ties shall be permitted to be used in computing Asx
and Isx .
All rights reserved
279 / 496
514.14 BEARING STRENGTH
FIGURE 514.14-1 Application of frustum to find A2 in stepped or sloped supports.
All rights reserved
280 / 496
514.14.1
Design bearing strength of concrete shall not exceed φ(0.85f’cA1), except when the supporting
surface is wider on all sides than the loaded area, then the design bearing strength of the loaded
area shall be permitted to be multiplied by √
but by not more than 2.
SECTION 515 SHEAR AND TORSION
515.1 SHEAR STRENGTH
515.1.1
Except for members designed in accordance with Appendix A, design of cross sections subject to
shear shall be based on
φVn ≥ Vu
EQUATION 515.1.1-1
where Vu is the factored shear force at the section considered and Vn is nominal shear strength
computed by
Vn = Vc + Vs
EQUATION 515.1.1-2
where Vc is nominal shear strength provided by concrete calculated in accordance with 515.2, or
515.13, and Vs is nominal shear strength provided by shear reinforcement calculated in
accordance with 515.3, 515.11.9, or 515.13.
515.1.1.1
In determining Vn, the effect of any openings in members shall be considered.
515.1.1.2
In determining Vc, whenever applicable, effects of axial tension due to creep and shrinkage
in restrained members shall be considered and effects of inclined flexural compression in
variable depth members shall be permitted to be included.
515.1.2
The values of √
used in this chapter shall not exceed 8.3 MPa except as allowed in 515.1.2.1.
515.1.2.1
Values of √
greater than 8.3 MPa shall be permitted in computing Vc, Vci , and Vcw for
reinforced or prestressed concrete beams and concrete joist construction having minimum
web reinforcement in accordance with 515.5.3, or 515.7.5.2.
515.1.3
Computation of maximum Vu at supports in accordance with 515.1.3.1 or 515.1.3.2 shall be
permitted if all conditions (a), (b), and (c) are satisfied:
(a) Support reaction, in direction of applied shear, introduces compression into the end regions
of member;
(b) Loads are applied at or near the top of the member;
(c) No concentrated load occurs between face of support and location of critical section defined
in 515.1.3.1 or 515.1.3.2.
515.1.3.1
For nonprestressed members, sections located less than a distance d from face of support
shall be permitted to be designed for Vu computed at a distance d.
All rights reserved
281 / 496
515.1.4
For deep beams, brackets and corbels, walls, and slabs and footings, the special provisions of
515.9 through 515.13 shall apply.
515.2 SHEAR STRENGTH PROVIDED BY CONCRETE FOR NONPRESTRESSED MEMBERS
515.2.1
Vc shall be computed by provisions of 515.2.1.1 through 515.2.1.3, unless a more detailed
calculation is made in accordance with 515.2.2. Throughout this chapter, except in 515.8, λ shall
be as defined in 512.6.1.
515.2.1.1
For members subject to shear and flexure only,
Vc = 0.17λ√
b wd
EQUATION 515.2.1.1-1
515.2.1.2
For members subject to axial compression,
Vc =0.17 (1+Nu/14Ag) λ √ bwd
EQUATION 515.2.1.1-2
Quantity Nu /Ag shall be expressed in MPa.
515.2.1.3
For members subject to significant axial tension, Vc shall be taken as zero unless a more
detailed analysis is made using 515.2.2.3.
515.2.2
Vc shall be permitted to be computed by the more detailed calculation of A11.2.2.1 through
515.2.2.3.
515.2.2.1
For members subject to shear and flexure only,
Vc=( 0.16λ √ +17ρw(Vud/Mu) bwd
but not greater than 0.29λ √
EQUATION 515.2.2.1-1
bwd. When computing Vc by Equation 515.2.2.1-1, Vud /Mu
shall not be taken greater than 1.0, where Mu occurs simultaneously with Vu at section
considered.
515.2.2.2
For members subject to axial compression, it shall be permitted to compute Vc using
Equation 515.2.2.1-1 with Mm substituted for Mu and Vud /Mu not then limited to 1.0,
where
Mm = [Mu – Nu(4h – d)]/ 8
EQUATION 515.2.2.2-1
However, Vc shall not be taken greater than
Vc= 0.29λ √
All rights reserved
bwd 1 √
EQUATION 515.2.2.2-2
282 / 496
Nu /Ag shall be expressed in MPa. When Mm as computed by Equation 515.2.2.2-1 is
negative, Vc shall be computed by Equation 515.2.2.2-2.
FIGURE 515.2.2.2-1 Comparison of shear strength equations for members subject to axial load.
515.2.2.3
For members subject to significant axial tension,
Vc= 0.17 [1+0.29Nu/Ag]λ√ bwd
EQUATION 515.2.2.3-1
but not less than zero, where Nu is negative for tension. Nu /Ag shall be expressed in MPa.
515.2.3
For circular members, the area used to compute Vc shall be taken as the product of the diameter
and effective depth of the concrete section. It shall be permitted to take d as 0.80 times the
diameter of the concrete section.
515.3 SHEAR STRENGTH PROVIDED BY SHEAR REINFORCEMENT
515.3.1 TYPES OF SHEAR REINFORCEMENT
Shear reinforcement consisting of the following shall be permitted:
(a) Stirrups perpendicular to axis of member;
(b) Welded wire reinforcement with wires located perpendicular to axis of member;
(c) Spirals, circular ties, or hoops.
515.3.2
For nonprestressed members, shear reinforcement shall be permitted to also consist of:
(a) Stirrups making an angle of 45 degrees or more with longitudinal tension reinforcement;
(b) Longitudinal reinforcement with bent portion making an angle of 30 degrees or more with
the longitudinal tension reinforcement;
(c) Combinations of stirrups and bent longitudinal reinforcement.
515.3.3
The values of fy and fyt used in design of shear reinforcement shall not exceed 420 MPa, except
the value shall not exceed 550 MPa for welded deformed wire reinforcement.
515.3.4
All rights reserved
283 / 496
Where the provisions of 515.3 are applied to prestressed members, d shall be taken as the
distance from extreme compression fiber to centroid of the prestressed and nonprestressed
longitudinal tension reinforcement, if any, but need not be taken less than 0.80h.
515.3.5
Stirrups and other bars or wires used as shear reinforcement shall extend to a distance d from
extreme compression fiber and shall be developed at both ends according to 516.13.
515.4 SPACING LIMITS FOR SHEAR REINFORCEMENT
515.4.1
Spacing of shear reinforcement placed perpendicular to axis of member shall not exceed d/2 in
nonprestressed members or 0.75h in prestressed members, nor 600 mm.
515.4.2
Inclined stirrups and bent longitudinal reinforcement shall be so spaced that every 45-degree
line, extending toward the reaction from mid-depth of member d/2 to longitudinal tension
reinforcement, shall be crossed by at least one line of shear reinforcement.
515.4.3
Where Vs exceeds 0.33 √
bwd, maximum spacings given in 515.4.1 and 515.4.2 shall be
reduced by one-half.
515.5 MINIMUM SHEAR REINFORCEMENT
515.5.1
A minimum area of shear reinforcement, Av,min, shall be provided in all reinforced concrete
flexural members (prestressed and nonprestressed) where Vu exceeds 0.5φVc, except in
members satisfying one or more of (a) through (f):
(a) Footings and solid slabs;
(b) Hollow-core units with total untopped depth not greater than 315 mm and hollow-core units
where: Vu is not greater than 0.5φVcw;
(c) Concrete joist construction defined by 512.13;
(d) Beams with h not greater than 250 mm;
(e) Beam integral with slabs with h not greater than 600 mm and not greater than the larger of
2.5 times thickness of flange, and 0.5 times width of web;
515.5.2
Minimum shear reinforcement requirements of 515.5.1 shall be permitted to be waived if shown
by test that required Mn and Vn can be developed when shear reinforcement is omitted. Such
tests shall simulate effects of differential settlement, creep, shrinkage, and temperature change,
based on a realistic assessment of such effects occurring in service.
515.5.3
Where shear reinforcement is required by 515.5.1 or for strength and where 515.7.1 allows
torsion to be neglected, Av,min for prestressed and nonprestressed members shall be computed
by
Av, min= 0.062 √ (bws/fyt)
EQUATION 515.5.3-1
but shall not be less than (0.35bws)/fyt.
515.6 DESIGN OF SHEAR REINFORCEMENT
All rights reserved
284 / 496
515.6.1
Where Vu exceeds φVc , shear reinforcement shall be provided to satisfy Equation 515.1.1-1 and
515.1.1-2, where Vs shall be computed in accordance with 515.6.2 through 515.6.9.
515.6.2
Where shear reinforcement perpendicular to axis of member is used,
Vs=Avfytd/s
EQUATION 515.6.2-1
where Av is the area of shear reinforcement within spacing s.
515.6.3
Where circular ties, hoops, or spirals are used as shear reinforcement, Vs shall be computed
using Equation 515.6.2-1 where d is defined in 515.2.3 for circular members, Av shall be taken as
two times the area of the bar in a circular tie, hoop, or spiral at a spacing s, s is measured in a
direction parallel to longitudinal reinforcement, and fyt is the specified yield strength of circular
tie, hoop, or spiral reinforcement.
515.6.4
Where inclined stirrups are used as shear reinforcement,
Vs=[Avfyt(sinα + cosα)d]/s
EQUATION 515.6.4-1
where α is angle between inclined stirrups and longitudinal axis of the member, and s is
measured in
direction parallel to longitudinal reinforcement.
515.6.5
Where shear reinforcement consists of a single bar or a single group of parallel bars, all bent up
at the same distance from the support,
Vs = Avfysinα
EQUATION 515.6.5-1
but not greater than 0.25 bwd, where α is angle between bent-up reinforcement and
longitudinal axis of the member.
515.6.6
Where shear reinforcement consists of a series of parallel bent-up bars or groups of parallel
bent-up bars at different distances from the support, Vs shall be computed by Equation 515.6.41.
515.6.7
Only the center three-fourths of the inclined portion of any longitudinal bent bar shall be
considered effective for shear reinforcement.
515.6.8
Where more than one type of shear reinforcement is used to reinforce the same portion of a
member, Vs shall be computed as the sum of the values computed for the various types of shear
reinforcement.
All rights reserved
285 / 496
515.6.9
Vs shall not be taken greater than 0.66 bwd.
515.7 DESIGN FOR TORSION
Design for torsion shall be in accordance with 515.3 through 515.5, or 515.6.
FIGURE 515.7-1 (a) Thin-walled tube; (b) area enclosed by shear flow path.
515.7.1 THRESHOLD TORSION
It shall be permitted to neglect torsion effects if the factored torsional moment Tu is less than:
(a) For nonprestressed members
φ0.083λ √
2
[A cp/pcp]
(b) For nonprestressed members subjected to an axial tensile or compressive force
φ0.083λ √
(
)√
√
For members cast monolithically with a slab, the overhanging flange width used in computing
Acp and pcp shall conform to 517.2.4. For a hollow section, Ag shall be used in place of Acp in
515.7.1, and the outer boundaries of the section shall conform to 517.2.4.
515.7.1.1
For isolated members with flanges and for members cast monolithically with a slab, the
overhanging flange width used to compute Acp and pcp shall conform to 517.2.4, except that
2
the overhanging flanges shall be neglected in cases where the parameter A cp /pcp
calculated for a beam with flanges is less than that computed for the same beam ignoring
the flanges.
515.7.2 CALCULATION OF FACTORED TORSIONAL MOMENT
All rights reserved
286 / 496
515.7.2.1
If the factored torsional moment, Tu, in a member is required to maintain equilibrium and
exceeds the minimum value given in 515.7.1, the member shall be designed to carry Tu in
accordance with 515.7.3 through 515.7.6.
FIGURE 515.7.2-1 Design torque may not be reduced
515.7.2.2
In a statically indeterminate structure where reduction of the torsional moment in a
member can occur due to redistribution of internal forces upon cracking, the maximum Tu
shall be permitted to be reduced to the values given in (a) or (b), as applicable:
(a) For nonprestressed members, at the sections described in 515.7.2.4
φ0.33λ√
(
)
EQUATION 515.7.2.2-1
(b) For nonprestressed members subjected to an axial tensile or compressive force
φ0.33λ√
(
)√
√
EQUATION 515.7.2.2-2
In (a) or (b), the correspondingly redistributed bending moments and shears in the adjoining
members shall be used in the design of these members. For hollow sections, Acp shall not be
replaced with Ag in 515.7.2.1.
All rights reserved
287 / 496
FIGURE 515.7.2.1-1 Design torque may be reduced
515.7.2.3
Unless determined by a more exact analysis, it shall be permitted to take the torsional
loading from a slab as uniformly distributed along the member.
515.7.2.4
In nonprestressed members, sections located less than a distance d from the face of a
support shall be designed for not less than Tu computed at a distance d. If a concentrated
torque occurs within this distance, the critical section for design shall be at the face of the
support.
515.7.3 TORSIONAL MOMENT STRENGTH
515.7.3.1
The cross-sectional dimensions shall be such that:
(a) For solid sections
EQUATION
515.7.3.1-1
(b) For hollow sections
EQUATION 515.7.3.1-2
All rights reserved
288 / 496
FIGURE 515.7.3.1-1 Addition of torsional and shear stresses.
515.7.3.2
If the wall thickness varies around the perimeter of a hollow section, Equation 515.7.3.1-2
shall be valuated at the location where the left-hand side of Equation 515.7.3.1-2 is a
maximum.
515.7.3.3
If the wall thickness is less than Aoh /ph , the second term in Equation 515.7.3.1-2 shall be
taken as where t is the thickness of the wall of the hollow section at the location where the
stresses are being checked. Tu/1.7Aoht
where t is the thickness of the wall of the hollow section at the location where the stresses
are being checked.
515.7.3.4
The values of fy and fyt used for design of torsional reinforcement shall not exceed
420 MPa.
515.7.3.5
Where Tu exceeds the threshold torsion, design of the cross section shall be based on
All rights reserved
289 / 496
φTn ≥ Tu
EQUATION 515.7.3.5-1
515.7.3.6
Tn shall be computed by
Tn=(2AoAtfyt/s)cotθ
EQUATION 515.7.3.6-1
where Ao shall be determined by analysis except that it shall be permitted to take Ao equal
to 0.85Aoh; θ shall not be taken smaller than 30 degrees nor larger than 60 degrees. It shall
be permitted to take θ equal to: 45 degrees for nonprestressed members.
FIGURE 515.7.3.6-1 Space truss analogy.
515.7.3.7
The additional area of longitudinal reinforcement to resist torsion, Al, shall not be less than
EQUATION 515.7.3.7-1
where θ shall be the same value used in Equation 515.7.3.6-1 and At /s shall be taken as the
amount computed from Equation 515.7.3.6-1 not modified in accordance with 515.7.5.2 or
515.7.5.3; fyt refers to closed transverse torsional reinforcement, and fy refers to
longitudinal torsional reinforcement.
515.7.3.8
Reinforcement required for torsion shall be added to that required for the shear, moment,
and axial force that act in combination with the torsion. The most restrictive requirements
for reinforcement spacing and placement shall be met.
515.7.3.9
It shall be permitted to reduce the area of longitudinal torsion reinforcement in the flexural
compression zone by an amount equal to Mu /(0.9dfy ), where Mu occurs at the section
All rights reserved
290 / 496
simultaneously with Tu, except that the reinforcement provided shall not be less than that
required by 515.7.5.3 or 515.7.6.2.
515.7.4 DETAILS OF TORSIONAL REINFORCEMENT
515.7.4.1
Torsion reinforcement shall consist of longitudinal bars or tendons and one or more of
the following:
(a) Closed stirrups or closed ties, perpendicular to the axis of the member;
(b) A closed cage of welded wire reinforcement with transverse wires perpendicular to
the axis of themember;
(c) In nonprestressed beams, spiral reinforcement.
515.7.4.2
Transverse torsional reinforcement shall be anchored by one of the following:
(a) A 135-degree standard hook, or seismic hook as defined in Section 2, around a
longitudinal bar;
(b) According to 516.13.2.1, 516.13.2.2, or 516.13.2.3 in regions where the concrete
surrounding the anchorage is restrained against spalling by a flange or slab or similar
member.
FIGURE 515.7.4.2-1 Spalling of corners of beams loaded in torsion.
All rights reserved
291 / 496
515.7.4.3
Longitudinal torsion reinforcement shall be developed at both ends.
515.7.4.4
For hollow sections in torsion, the distance from the centerline of the transverse torsional
reinforcement to the inside face of the wall of the hollow section shall not be less than
0.5Aoh /ph .
515.7.5 MINIMUM TORSION REINFORCEMENT
515.7.5.1
A minimum area of torsional reinforcement shall be provided in all regions where Tu exceeds
the threshold torsion given in 515.7.1.
515.7.5.2
Where torsional reinforcement is required by 515.7.5.1, the minimum area of transverse
closed stirrups shall be computed by
(Av + 2At)= 0.062 √
(bws/fyt)
EQUATION 515.7.5.2-1
but shall not be less than (0.35bw s)/fyt .
515.7.5.3
Where torsional reinforcement is required by 515.7.5.1, the minimum total area of
longitudinal torsional reinforcement, Al,min, shall be computed by
EQUATION 515.7.5.2-2
where At /s shall not be taken less than 0.175bw /fyt; fyt refers to closed transverse torsional
reinforcement, and fy refers to longitudinal reinforcement.
515.7.6 SPACING OF TORSION REINFORCEMENT
515.7.6.1
The spacing of transverse torsion reinforcement shall not exceed the smaller of ph /8 or
300 mm.
515.7.6.2
The longitudinal reinforcement required for torsion shall be distributed around the
perimeter of the closed stirrups with a maximum spacing of 300 mm. The longitudinal
bars or tendons shall be inside the stirrups. There shall be at least one longitudinal bar
or tendon in each corner of the stirrups. Longitudinal bars shall have a diameter at least
0.042 times the stirrup spacing, but not less than No. 10.
515.7.6.3
Torsional reinforcement shall be provided for a distance of at least (bt + d) beyond the
point required by analysis.
All rights reserved
292 / 496
515.7.7 ALTERNATIVE DESIGFN FOR TORSION
For torsion design of solid sections within the scope of this code with an aspect ratio, h/bt, of 3
or greater, it shall be permitted to use another procedure, the adequacy of which has been
shown by analysis and substantial agreement with results of comprehensive tests. Sections
515.7.4 and 515.7.6 shall apply.
515.8 SHEAR-FRICTION
515.8.1
Provisions of 515.8 are to be applied where it is appropriate to consider shear transfer across a
given plane, such as: an existing or potential crack, an interface between dissimilar materials, or
an interface between two concretes cast at different times.
515.8.2
Design of cross sections subject to shear transfer as described in 515.8.1 shall be based on
Equation 515.1.1-1), where Vn is calculated in accordance with provisions of 515.8.3 or 515.8.4.
FIGURE 515.8.2-1 Structural action of a corbel.
515.8.3
A crack shall be assumed to occur along the shear plane considered. The required area of
shearfriction reinforcement Avf across the shear plane shall be designed using either 515.8.4 or
any other shear transfer design methods that result in prediction of strength in substantial
agreement with results of comprehensive tests.
515.8.3.1
Provisions of 515.8.5 through 515.8.10 shall apply for all calculations of shear transfer
strength.
515.8.4 SHEAR-FRICTION DESIGN METHOD
515.8.4.1
Where shear-friction reinforcement is perpendicular to the shear plane, Vn shall be
All rights reserved
293 / 496
computed by
Vn = Avf fy μ
EQUATION 515.8.4.1-1
where μ is coefficient of friction in accordance with 515.8.4.3.
515.8.4.2
Where shear-friction reinforcement is inclined to the shear plane, such that the shear force
produces tension in shear-friction reinforcement, Vn shall be computed by
Vn = Avf fy (μ sin α + cosα)
EQUATION 515.8.4.2-1
where α is angle between shear-friction reinforcement and shear plane.
FIGURE 515.8.4.2-1 Shear-friction reinforcement at an angle to assumed crack.
515.8.4.3
The coefficient of friction μ in Equation 515.8.4.1-1 and Equation 515.8.4.2-1 shall be taken
as:
Concrete placed monolithically........................................................................................... 1.4λ
Concrete placed against hardened concrete with surface intentionally roughened as
specified in 515.8.9.............................................................................................................. 1.0λ
Concrete placed against hardened concrete not intentionally roughened.................... 0.6λ
Concrete anchored to as-rolled structural steel by headed studs or by reinforcing bars
(see 515.8.10)......................................................................................................... 0.7λ
where λ = 1.0 for normalweight concrete. Otherwise, λ shall be determined based on
volumetric proportions of normalweight aggregates as specified in 512.6.1, but shall not
exceed 0.85.
515.8.5
For normalweight concrete either placed monolithically or placed against hardened concrete
with surface intentionally roughened as specified in 515.8.9, Vn shall not exceed the smallest of
0.2f΄cAc, (3.3 + 0.08f΄c )Ac and 11Ac, where Ac is area of concrete section resisting shear transfer.
For all other cases, Vn shall not exceed the smaller of 0.2f΄cAc or 5.5Ac. Where concretes of
All rights reserved
294 / 496
different strengths are cast against each other, the value of f΄c used to evaluate Vn shall be that
of the lower-strength concrete.
515.8.6
The value of fy used for design of shearfriction reinforcement shall not exceed 420 MPa.
515.8.7
Net tension across shear plane shall be resisted by additional reinforcement. Permanent net
compression across shear plane shall be permitted to be taken as additive to Avf fy, the force in
the shearfriction reinforcement, when calculating required Avf .
515.8.8
Shear-friction reinforcement shall be appropriately placed along the shear plane and shall be
anchored to develop fy on both sides by embedment, hooks, or welding to special devices.
515.8.9
For the purpose of 515.8, when concrete is placed against previously hardened concrete, the
interface for shear transfer shall be clean and free of laitance. If μ is assumed equal to 1.0λ,
interface shall be roughened to a full amplitude of approximately 6 mm.
515.8.10
When shear is transferred between asrolled steel and concrete using headed studs or
welded reinforcing bars, steel shall be clean and free of paint.
515.9 DEEP BEAMS
515.9.1
The provisions of 515.9 shall apply to members with ln not exceeding four times the overall
member depth or regions of beams with concentrated loads within twice the member depth
from the support that are loaded on one face and supported on the opposite face so that
compression struts can develop between the loads and supports.
515.9.2
Deep beams shall be designed using either nonlinear analysis as permitted in 514.7.1.
515.9.3
Vn for deep beams shall not exceed 0.83 √
bwd.
515.9.4
The area of shear reinforcement perpendicular to the flexural tension reinforcement, Av, shall
not be less than 0.0025bws, and s shall not exceed the smaller of d/5 and 300 mm.
515.9.5
The area of shear reinforcement parallel to the flexural tension reinforcement, Avh, shall not be
less than 0.0015bws2, and s2 shall not exceed the smaller of d/5 and 300 mm.
515.9.6
It shall be permitted to provide reinforcement satisfying 511.3 instead of the minimum
horizontal and vertical reinforcement specified in 515.9.4 and 515.9.5.
All rights reserved
295 / 496
515.10 PROVISIONS FOR BRACKETS AND CORBELS
515.10.1
Brackets and corbels with a shear span-todepth ratio av /d less than 2 shall be permitted to be
designed using this code. Design shall be permitted using 515.10.3 and 515.10.4 for brackets and
corbels with:
(a) av /d not greater than 1, and
(b) subject to factored horizontal tensile force, Nuc, not larger than Vu.
The requirements of 515.10.2, 515.10.3.2.1, 515.10.5, 515.10.6, and 515.10.7 shall apply to design
of brackets and corbels. Effective depth d shall be determined at the face of the support.
FIGURE 515.10.1-1 Notation used in Section 515.10.
515.10.2
Depth at outside edge of bearing area shall not be less than 0.5d.
515.10.3
Section at face of support shall be designed to resist simultaneously Vu, a factored moment
[Vuav + Nuc(h – d)], and a factored horizontal tensile force, Nuc.
515.10.3.1
In all design calculations in accordance with 515.10, φ shall be taken equal to 0.75.
515.10.3.2
Design of shear-friction reinforcement, Avf , to resist Vu shall be in accordance with 515.8.
515.10.3.2.1
For normalweight concrete, Vn shall not exceed the smallest of 0.2f΄cbwd, (3.3 +
0.08f΄c)bwd, and 11bwd.
515.10.3.3
All rights reserved
296 / 496
Reinforcement Af to resist factored moment [Vuav + Nuc(h – d)] shall be computed in
accordance with 514.2 and 514.3.
515.10.3.4
Reinforcement An to resist factored tensile force Nuc shall be determined from
φAnfy ≥ Nuc. Factored tensile force, Nuc, shall not be taken less than 0.2Vu unless provisions
are made to avoid tensile forces. Nuc shall be regarded as a live load even if tension results
from restraint of creep,shrinkage, or temperature change.
515.10.3.5
Area of primary tension reinforcement Asc shall not be less than the larger of (Af + An) and
(2Avf /3 + An).
515.10.4
Total area, Ah, of closed stirrups or ties parallel to primary tension reinforcement shall not be
less than 0.5(Asc – An). Distribute Ah uniformly within (2/3)d adjacent to primary tension
reinforcement.
515.10.5
Asc /bd shall not be less than 0.04(f’c/fy).
515.10.6
At front face of bracket or corbel, primary tension reinforcement shall be anchored by one of the
following:
(a) By a structural weld to a transverse bar of at least equal size; weld to be designed to develop
fy of
primary tension reinforcement;
(b) By bending primary tension reinforcement back to form a horizontal loop; or
(c) By some other means of positive anchorage.
515.10.7
Bearing area on bracket or corbel shall not project beyond straight portion of primary tension
reinforcement, nor project beyond interior face of transverse anchor bar (if one is provided).
515.11 PROVISION FOR WALLS
515.11.1
Design for shear forces perpendicular to face of wall shall be in accordance with provisions for
slabs in 515.13. Design for horizontal in-plane shear forces in a wall shall be in accordance with
515.11.2 through 515.11.9. Alternatively, it shall be permitted to design walls with a height not
exceeding two times the length of the wall for horizontal shear forces in accordance with
515.11.9.2 through 515.11.9.5.
515.11.2
Design of horizontal section for shear in plane of wall shall be based on Equation 515.1.1-1 and
515.1.1-2, where Vc shall be in accordance with 515.11.5 or 515.11.6 and Vs shall be in
accordance with 515.11.9.
515.11.3
Vn at any horizontal section for shear in plane of wall shall not be taken greater than 0.83 √
where h is thickness of wall, and d is defined in 515.11.4.
All rights reserved
297 / 496
,
515.11.4
For design for horizontal shear forces in plane of wall, d shall be taken equal to 0.8lw. A larger
value of d, equal to the distance from extreme compression fiber to center of force of all
reinforcement in tension, shall be permitted to be used when determined by a strain
compatibility analysis.
515.11.5
Unless a more detailed calculation is made in accordance with 515.11.6, Vc shall not be taken
greater than 0.17λ hd for walls subject to axial compression, or Vc shall not be taken greater
than the value given in 515.2.2.3 for walls subject to axial tension.
515.11.6
Vc shall be permitted to be the lesser of the values computed from Equation 515.11.6-1 and
515.11.6-2
Vc= 0.27λ√
or
hd+Nud/4lw
Vc= (
√
EQUATION 515.11.6-1
(
√
)
EQUATION 515.11.6-2
where lw is the overall length of the wall, and Nu is positive for compression and negative for
tension. If
(Mu/Vu – lw /2) is negative, Equation 515.11.6-2 shall not apply.
515.11.7
Sections located closer to wall base than a distance lw /2 or one-half the wall height, whichever
is less, shall be permitted to be designed for the same Vc as that computed at a distance lw /2 or
one-half the height.
515.11.8
Where Vu is less than 0.5φVc, reinforcement shall be provided in accordance with 515.11.9 or in
accordance with Section 518. Where Vu exceeds 0.5φVc, wall reinforcement for resisting shear
shall be provided in accordance with 515.11.9.
515.11.9 DESIGN OF SHEAR REINFORCEMENT FOR WALLS
515.11.9.1
Where Vu exceeds φVc , horizontal shear reinforcement shall be provided to satisfy Equation
515.1.1-1 and 515.1.1-2, where Vs shall be computed by
Vs=Avfyd/s
EQUATION 515.11.9.1-1
where Av is area of horizontal shear reinforcement within spacing s, and d is determined in
accordance with 515.11.4. Vertical shear reinforcement shall be provided in accordance with
A11.9.9.4.
515.11.9.2
All rights reserved
298 / 496
Ratio of horizontal shear reinforcement area to gross concrete area of vertical section,ρ t
shall not be less than 0.0025.
515.11.9.3
Spacing of horizontal shear reinforcement shall not exceed the smallest of lw /5, 3h, and 450
mm, where lw is the overall length of the wall.
515.11.9.4
Ratio of vertical shear reinforcement area to gross concrete area of horizontal section, ρl ,
shall not be less than the larger of
ρl = 0.0025 + 0.5 (ρt – 0.0025)
EQUATION 515.11.9.4-1
and 0.0025, The value of ρl calculated by Equation 515.11.9.4-1 need not be greater than ρt
required by 515.11.9.1. In Equation 515.11.9.4-1, lw is the overall length of the wall, and hw
is the overall height of the wall.
515.11.9.5
Spacing of vertical shear reinforcement shall not exceed the smallest of lw /3, 3h, and 450
mm, where lw is the overall length of the wall.
515.12 TRANSFER OF MOMENTS TO COLUMNS
515.12.1
When gravity load, wind, earthquake, or other lateral forces cause transfer of moment at
connections of framing elements to columns, the shear resulting from moment transfer shall be
considered in the design of lateral reinforcement in the columns.
515.12.2
Except for connections not part of a primary seismic load-resisting system that are
restrained on four sides by beams or slabs of approximately equal depth, connections shall have
lateral reinforcement not less than that required by Equation 515.5.3-1 within the column for a
depth not less than that of the deepest connection of framing elements to the columns. See also
506.9.
515.13 PROVISIONS FOR SLABS AND FOOTINGS
515.13.1
The shear strength of slabs and footings in the vicinity of columns, concentrated loads, or
reactions is governed by the more severe of two conditions:
515.13.1.1
Beam action where each critical section to be investigated extends in a plane across the
entire width. For beam action, the slab or footing shall be designed in accordance with 515.1
through 515.3.
515.13.1.2
For two-way action, each of the critical sections to be investigated shall be located so that its
perimeter bo is a minimum but need not approach closer than d/2 to:
(a) Edges or corners of columns, concentrated loads, or reaction areas; and
All rights reserved
299 / 496
(b) Changes in slab thickness such as edges of capitals, drop panels, or shear caps. For twoway action, the slab or footing shall be designed in accordance with 515.13.2 through
515.13.6.
FIGURE 515.13.1.2-1 Value of β for a nonrectangular loaded area.
515.13.1.3
For square or rectangular columns, concentrated loads, or reaction areas, the critical
sections with four straight sides shall be permitted.
515.13.2
The design of a slab or footing for two-way action is based on Equation 515.1.1-1 and 515.1.1-2.
Vc shall be computed in accordance with 515.13.2.1, 515.13.2.2, or 515.13.3.1. Vs shall be
computed in accordance with 515.13.3. For slabs with shearheads, Vn shall be in accordance
with 515.13.4. When moment is transferred between a slab and a column, 515.13.6 shall apply.
515.13.2.1
For nonprestressed slabs and footings, Vc shall be the smallest of (a), (b), and (c):
(a) Vc =0.17( 1+ 2/β)λ √
bod
EQUATION 515.13.2.1-1
where
β is the ratio of long side to short side of the column, concentrated load or reaction area;
(b) Vc= 0.083(αsd/bo + 2)λ √
bod
EQUATION 515.13.2.1-2
where
αs is 40 for interior columns, 30 for edge columns, 20 for corner columns; and
(c) Vc = 0.33λ √
bod
EQUATION 515.13.2.1-3
515.13.2.2
At columns of two-way prestressed slabs and footings
All rights reserved
300 / 496
Vc = (βpλ √
+ 0.3fpc)bod + Vp
EQUATION 515.13.2.2-1
where
βp is the smaller of 3.5 and 0.083(αsd/bo + 1.5), αs is 40 for interior columns, 30 for edge
columns, and 20 for corner columns, bo is perimeter of critical section defined in 515.13.1.2,
fpc is taken as the average value of fpc for the two directions, and Vp is the vertical
component of all effective prestress forces crossing the critical section. Vc shall be permitted
to be computed by Equation 515.13.2.2-1 if the following are satisfied; otherwise,
515.13.2.1 shall apply:
(a) No portion of the column cross section shall be closer to a discontinuous edge than four
times the slab thickness;
(b) The value of√ f΄c used in Equation 515.13.2.2-1 shall not be taken greater than 5.8 MPa;
and
(c) In each direction, fpc shall not be less than 0.9 MPa, nor be taken greater than 3.5 MPa.
515.13.3
Shear reinforcement consisting of bars or wires and single- or multiple-leg stirrups shall be
permitted in slabs and footings with d greater than or equal to 150 mm, but not less than 16
times the shear reinforcement bar diameter. Shear reinforcement shall be in accordance with
515.13.3.1 through 515.13.3.4.
All rights reserved
301 / 496
FIGURE 515.13.3-1(a)-(c): Single- or multiple-leg stirrup-type slab shear reinforcement.
FIGURE 515.13.3-1(d) Arrangement of stirrup shear reinforcement, interior column.
All rights reserved
302 / 496
FIGURE 515.13.3-1(e)—Arrangement of stirrup shear reinforcement, edge column.
515.13.3.1
Vn shall be computed by Equation 515.1.1-2, where Vc shall not be taken greater than
0.17λ√
bod, and Vs shall be calculated in accordance with 515.3. In Equation 515.6.2-1,
Av shall be taken as the cross-sectional area of all legs of reinforcement on one peripheral
line that is geometrically similar to the perimeter of the column section.
515.13.3.2
Vn shall not be taken greater than 0.5√
bod.
515.13.3.3
The distance between the column face and the first line of stirrup legs that surround the
column shall not exceed d/2. The spacing between adjacent stirrup legs in the first line of
shear reinforcement shall not exceed 2d measured in a direction parallel to the column face.
The spacing between successive lines of shear reinforcement that surround the column shall
not exceed d/2 measured in a direction perpendicular to the column face.
515.13.3.4
Slab shear reinforcement shall satisfy the anchorage requirements of 516.13 and shall
engage the longitudinal flexural reinforcement in the direction being considered.
515.13.4
Shear reinforcement consisting of structural steel I- or channel-shaped sections (shearheads)
shall be permitted in slabs. The provisions of 515.13.4.1 through 515.13.4.9 shall apply where
All rights reserved
303 / 496
shear due to gravity load is transferred at interior column supports. Where moment is
transferred to columns, 515.13.7.3 shall apply.
515.13.4.1
Each shearhead shall consist of steel shapes fabricated by welding with a full penetration
weld into identical arms at right angles. Shearhead arms shall not be interrupted within the
column section.
515.13.4.2
A shearhead shall not be deeper than 70 times the web thickness of the steel shape.
515.13.4.3
The ends of each shearhead arm shall be permitted to be cut at angles not less than 30
degrees with the horizontal, provided the plastic moment strength of the remaining tapered
section is adequate to resist the shear force attributed to that arm of the shearhead.
515.13.4.4
All compression flanges of steel shapes shall be located within 0.3d of compression surface
of slab.
515.13.4.5
The ratio αv between the flexural stiffness of each shearhead arm and that of the
surrounding composite cracked slab section of width (c2 + d) shall not be less than 0.15.
FIGURE 515.13.4.5-1 Idealized shear acting on shearhead.
515.13.4.6
Plastic moment strength, Mp , required for each arm of the shearhead shall be computed by
Mp=Vu/2φn{ hv+ αv[ lv-c1/2]}
EQUATION 515.13.4.6-1
where φ is for tension-controlled members, n is number of shearhead arms, and lv is
minimum length of each shearhead arm required to comply with requirements of 515.13.4.7
and 515.13.4.8.
All rights reserved
304 / 496
515.13.4.7
The critical slab section for shear shall be perpendicular to the plane of the slab and shall
cross each shearhead arm at three-quarters the distance [lv – (c1/2)] from the column face
to the end of the shearhead arm. The critical section shall be located so that its perimeter bo
is a minimum, but need not be closer than the perimeter defined in 515.13.1.2(a).
FIGURE 515.13.4.7-1 Location of critical section defined in 515.13.4.7.
515.13.4.8
Vn shall not be taken greater than 0.33 √
bod on the critical section defined in
515.13.4.7. When shearhead reinforcement is provided, Vn shall not be taken greater than
0.58√
bod on the critical section defined in 515.13.1.2(a).
515.13.4.9
Moment resistance Mv contributed to each slab column strip by a shearhead shall not be
taken greater than
Mv=φαvVu/2n( lv-c1/2)
EQUATION 515.13.4.9-1
where φ is for tension-controlled members, n is number of shearhead arms, and lv is length
of each
shearhead arm actually provided. However, Mv shall not be taken larger than the smallest
of:
(a) 30 percent of the total factored moment required for each slab column strip;
All rights reserved
305 / 496
(b) The change in column strip moment over the length lv;
(c) Mp computed by Equation 515.13.4.6-1.
515.13.4.10
When unbalanced moments are considered, the shearhead must have adequate
anchorage to transmit Mp to the column.
515.13.5
Headed shear stud reinforcement, placed perpendicular to the plane of a slab or footing, shall be
permitted in slabs and footings in accordance with 515.13.5.1 through 515.13.5.4. The overall
height of the shear stud assembly shall not be less than the thickness of the member less the
sum of:
(1) the concrete cover on the top flexural reinforcement;
(2) the concrete cover on the base rail; and
(3) one-half the bar diameter of the tension flexural reinforcement.
Where flexural tension reinforcement is at the bottom of the section, as in a footing, the overall
height of the shear stud assembly shall not be less than the thickness of the member less the
sum of:
(1) the concrete cover on the bottom flexural reinforcement;
(2) the concrete cover on the head of the stud; and
(3) one-half the bar diameter of the bottom flexural reinforcement.
All rights reserved
306 / 496
FIGURE 515.13.5-1 Typical arrangements of headed shear stud reinforcement and critical sections.
515.13.5.1
For the critical section defined in 515.13.1.2, Vn shall be computed using Equation 515.1.1-2,
with Vc and Vn not exceeding 0.25λ√
bod and 0.66 √
bod, respectively. Vs shall be
calculated using Equation 515.6.2-1 with Av equal to the cross-sectional area of all the shear
reinforcement on one peripheral line that is approximately parallel to the perimeter of the
column section, where s is the spacing of the peripheral lines of headed shear stud
reinforcement. Avfyt /(bos) shall not be less than 0.17√
.
515.13.5.2
The spacing between the column face and the first peripheral line of shear reinforcement
shall not exceed d/2. The spacing between peripheral lines of shear reinforcement,
measured in a direction perpendicular to any face of the column, shall be constant. For
prestressed slabs or footings satisfying 515.13.2.2, this spacing shall not exceed 0.75d; for all
other slabs and footings, the spacing shall be based on the value of the shear stress due to
factored shear force and unbalanced moment at the critical section defined in 515.13.1.2,
and shall not exceed:
All rights reserved
307 / 496
(a) 0.75d where maximum shear stresses due to factored loads are less than or equal to
0.5φ√ ; and
(b) 0.5d where maximum shear stresses due to factored loads are greater than 0.5φ√ .
515.13.5.3
The spacing between adjacent shear reinforcement elements, measured on the perimeter of
the first peripheral line of shear reinforcement, shall not exceed 2d.
515.13.5.4
Shear stress due to factored shear force and moment shall not exceed 0.17φλ√
at the
critical section located d/2 outside the outermost peripheral line of shear reinforcement.
515.13.6 OPENINGS IN SLABS
When openings in slabs are located at a distance less than 10 times the slab thickness from a
concentrated load or reaction area, or when openings in flat slabs are located within column
strips as defined in Section 517, the critical slab sections for shear defined in 515.13.1.2 and
515.13.4.7 shall be modified as follows:
FIGURE 515.13.6-1 Effect of openings and free edges (effective perimeter shown with dashed lines).
All rights reserved
308 / 496
FIGURE 515.13.6-2 Assumed distribution of shear stress.
515.13.6.1
For slabs without shearheads, that part of the perimeter of the critical section that is
enclosed by straight lines projecting from the centroid of the column, concentrated load,
or reaction area and tangent to the boundaries of the openings shall be considered
ineffective.
515.13.6.2
For slabs with shearheads, the ineffective portion of the perimeter shall be one-half of
that defined in 515.13.6.1.
515.13.7 TRANSFER OF MOMENT IN SLAB-COLUMN CONNECTIONS
515.13.7.1
Where gravity load, wind, earthquake, or other lateral forces cause transfer of unbalanced
moment Mu between a slab and column, γfMu shall be transferred by flexure in accordance
with 517.5.3. The remainder of the unbalanced moment, γvMu, shall be considered to be
transferred by eccentricity of shear about the centroid of the critical section defined in
515.13.1.2 where
γv = (1 – γf)
EQUATION 515.13.7.1-1
All rights reserved
309 / 496
FIGURE 515.13.7.1-1 Effect of openings and free edges (effective perimeter shown with dashed
lines).
515.13.7.2
The shear stress resulting from moment transfer by eccentricity of shear shall be assumed to
vary linearly about the centroid of the critical sections defined in 515.13.1.2. The maximum
shear stress due to Vu and Mu shall not exceed φvn:
(a) For members without shear reinforcement,
φvn = φVc /(bod)
EQUATION 515.13.7.2-1
where Vc is as defined in 515.13.2.1 or 515.13.2.2.
(b) For members with shear reinforcement other than shearheads,
φvn = φ(Vc + Vs)/(bod)
EQUATION 515.13.7.2-2
where Vc and Vs are defined in 515.13.3.1. The design shall take into account the variation of
shear
stress around the column. The shear stress due to factored shear force and moment shall
not exceed
φ(0.17λ√
) at the critical section located d/2 outside the outermost line of stirrup legs
that
surround the column.
515.13.7.3
When shear reinforcement consisting of structural steel I- or channel-shaped sections
(shearheads) is provided, the sum of the shear stresses due to vertical load acting on the
critical section defined by 515.13.4.7 and the shear stresses resulting from moment
transferred by eccentricity of shear about the centroid of the critical section defined in
515.13.1.2(a) and 515.13.1.3 shall not exceed φ0.33λ√ .
All rights reserved
310 / 496
SECTION 516 DEVELOPMENT AND SPLICES OF REINFORCEMENT
Is any 516.1
516.1.1
Calculated tension or compression in reinforcement at each section of structural concrete
members shall be developed on each side of that section by embedment length, hook, headed
deformed bar or mechanical device, or a combination thereof. Hooks and heads shall not be
used to develop bars in compression.
516.1.2
The values of √
used in this chapter shall not exceed 8.3 MPa.
516.1.3
In addition to requirements in this chapter that affect detailing of reinforcement, structural
integrity requirements of 506.13 shall be satisfied.
516.2 DEVELOPMENT OF DEFORMED BARS AND DEFORMED WIRE TENSION
516.2.1
Development length for deformed bars and deformed wire in tension, ld, shall be determined
from either 516.2.2 or 516.2.3 and applicable modification factors of 516.2.4 and 516.2.5, but ld
shall not be less than 300 mm.
516.2.2
For deformed bars or deformed wire, ld shall be as follows:
No. 19 and
smaller bars and
deformed wires
Spacing and cover
No. 22 and
larger bars
Clear spacing of bars or wires being
developed or spliced not less than
db, clear cover not less than db , and
stirrups or ties throughout ld not less
than the Code minimum Or Clear
spacing of bars or wires being
developed or spliced not less than
2db and clear cover not less than db
Other cases
516.2.3
For deformed bars or deformed wire, ld shall be
(
√ ΄ (
)
)
EQUATION 516.2.3-1
in which the confinement term (cb + Ktr )/db shall not be taken greater than 2.5, and
Ktr = 40Atr/sn
All rights reserved
EQUATION 516.2.3-2
311 / 496
where n is the number of bars or wires being spliced or developed along the plane of splitting. It
shall be permitted to use Ktr = 0 as a design simplification even if transverse reinforcement is
present.
516.2.4
The factors used in the expressions for development of deformed bars and deformed wires in
tension in 516.2 are as follows:
(a) Where horizontal reinforcement is placed such that more than 300 mm of fresh concrete is
cast below the development length or splice, ψt = 1.3. For other situations, ψt = 1.0.
(c) For No. 19 and smaller bars and deformed wires, ψs = 0.8. For No. 22 and larger bars, ψs =
1.0.
516.2.5 EXCESS REINFORCEMENT
Reduction in ld shall be permitted where reinforcement in a flexural member is in excess of that
required by analysis except where anchorage or development for fy is specifically required or the
reinforcement is designed under provisions of 521.1.1.6..................... (As required)/(As
provided).
516.3 DEVELOPMENT OF DEFORMED BARS AND DEFORMED WIRE IN COMPRESSION
516.3.1
Development length for deformed bars and deformed wire in compression, ldc , shall be
determined from 516.3.2 and applicable modification factors of 516.3.3, but ldc shall not be less
than 200 mm.
516.3.2
For deformed bars and deformed wire, ldc shall be taken as the larger of
(0.24fy /λ√
)db and (0.043fy)db, with λ as given in 516.2.4(d) and the constant 0.043 carries
2
the unit of mm /N.
516.3.3
Length ldc in 12.3.2 shall be permitted to be multiplied by the applicable factors for:
(a) Reinforcement in excess of that required by analysis.................... (As required)/(As provided)
(b) Reinforcement enclosed within spiral reinforcement not less than 6 mm diameter and not
more than 100 mm pitch or within No. 13 ties in conformance with 506.10.5 and spaced at not
more than 100 mm on center ........................................................................................ 0.75
516.4 DEVELOPMENT OF BUNDLE BARS
516.4.1
Development length of individual bars within a bundle, in tension or compression, shall be that
for the individual bar, increased 20 percent for three-bar bundle, and 33 percent for four-bar
bundle.
516.4.2
For determining the appropriate spacing and cover values in 516.2.2, the confinement term in
516.2.3, and the ψe factor in 516.2.4(b), a unit of bundled bars shall be treated as a single bar of
a diameter derived from the equivalent total area and having a centroid that coincides with that
of the bundled bars.
All rights reserved
312 / 496
516.5 DEVELOPMENT OF STANDARD HOOKS IN TENSION
FIGURE 516.5-1 Ties or stirrups placed parallel to the bar being developed, spaced along the length
of the tail extension of the hook plus bend.
FIGURE 516.5-2 Concrete cover per 12.5.4.
516.5.1
Development length for deformed bars in tension terminating in a standard hook (see 506.1),
ldh, shall be determined from 516.5.2 and the applicable modification factors of 516.5.3, but ldh
shall not be less than the larger of 8db and 150 mm.
516.5.2
For deformed bars, ldh shall be (0.24ψefy / λ ć′ )db with ψe taken as 1.2 for epoxycoated reinforcement, and λ taken as 0.75 for lightweight concrete. For other cases, ψe and λ shall
be taken as 1.0.
All rights reserved
313 / 496
516.5.3
Length ldh in 516.5.2 shall be permitted to be multiplied by the following applicable factors:
(a) For No. 36 bar and smaller hooks with side cover (normal to plane of hook) not less than 65
mm, and for 90-degree hook with cover on bar extension beyond hook not less than 50
mm................................................................................................................................ 0.7
(b) For 90-degree hooks of No. 36 and smaller bars that are either enclosed within ties or
stirrups
perpendicular to the bar being developed, spaced not greater than 3db along ldh; or enclosed
within
ties or stirrups parallel to the bar being developed, spaced not greater than 3db along the length
of the tail extension of the hook plus bend................................................................... 0.8
(c) For 180-degree hooks of No. 36 and smaller bars that are enclosed within ties or stirrups
perpendicular to the bar being developed, spaced not greater than 3db along ldh
.......................... 0.8
(d) Where anchorage or development for fy is not specifically required, reinforcement in excess
of that required by analysis .......................................................... (As required)/(As provided)
In 516.5.3(b) and 516.5.3(c), db is the diameter of the hooked bar, and the first tie or stirrup shall
enclose the bent portion of the hook, within 2db of the outside of the bend.
FIGURE 516.5.3-1 Hooked bar details for development of standard hooks.
All rights reserved
314 / 496
516.5.3
For bars being developed by a standard hook at discontinuous ends of members with both side
cover and top (or bottom) cover over hook less than 65 mm, the hooked bar shall be enclosed
within ties or stirrups perpendicular to the bar being developed, spaced not greater than 3db
along ldh. The first tie or stirrup shall enclose the bent portion of the hook, within 2db of the
outside of the bend, where db is the diameter of the hooked bar. For this case, the factors of
516.5.3(b) and (c) shall not apply.
516.5.4
Hooks shall not be considered effective in developing bars in compression.
516.6 DEVELOPMENT OF HEADED AND MECHANICALLY ANCHORED DEFORMED BARS IN TENSION
516.6.1
Development length for headed deformed bars in tension, ldt, shall be determined from 516.6.2.
Use of heads to develop deformed bars in tension shall be limited to conditions satisfying (a)
through (f):
(a) Bar fy shall not exceed 420 MPa;
(b) Bar size shall not exceed No. 36;
(c) Concrete shall be normalweight;
(d) Net bearing area of head Abrg shall not be less than 4Ab;
(e) Clear cover for bar shall not be less than 2db; and
(f) Clear spacing between bars shall not be less than 4db.
516.6.2
For headed deformed bars satisfying 511.5.6, development length in tension ldt shall be
(0.19ψefy / √
)db , where the value of f΄c used to calculate ldt shall not exceed 40 MPa, and
factor ψe shall be taken as 1.0. Where reinforcement provided is in excess of that required by
analysis, except where development of fy is specifically required, a factor of (As required)/(As
provided) may be applied to the expression for ldt. Length ldt shall not be less than the larger of
8db and 150 mm.
516.6.3
Heads shall not be considered effective in developing bars in compression.
516.6.4
Any mechanical attachment or device capable of developing fy of reinforcement is allowed,
provided that test results showing the adequacy of such attachment or device are approved by
the building official. Development of reinforcement shall be permitted to consist of a
combination of mechanical anchorage plus additional embedment length of reinforcement
between the critical section and the mechanical attachment or device.
516.7 DEVELOPMENT OF WELDED DEFORMED WIRE REINFORCEMENT IN TENSION
516.7.1
Development length for welded deformed wire reinforcement in tension, ld, measured from the
point of critical section to the end of wire shall be computed as the product of ld, from 516.2.2
or 516.2.3, times welded deformed wire reinforcement factor, ψw, from 516.7.2 or 516.7.3. It
All rights reserved
315 / 496
shall be permitted to reduce ld in accordance with 516.2.5 when applicable, but ld shall not be
less than 200 mm except in computation of lap splices by 516.18.
FIGURE 516.7.1-1 Development of welded deformed wire reinforcement.
516.7.2
For welded deformed wire reinforcement with at least one cross wire within ld and not less than
50 mm from the point of the critical section, ψw shall be the greater of (fy – 240)/fy and 5db/s
but not greater than 1.0, where s is the spacing between the wires to be developed.
516.7.3
For welded deformed wire reinforcement with no cross wires within ld or with a single cross wire
less than 50 mm from the point of the critical section, ψw shall be taken as 1.0, and ld shall be
determined as for deformed wire.
516.7.4
Where any plain wires, or deformed wires larger than D-31, are present in the welded deformed
wire reinforcement in the direction of the development length, the reinforcement shall be
developed in accordance with 516.8.
516.8 DEVELOPMENT OF WELDED PLAIN WIRE REINFORCEMENT IN TENSION
Yield strength of welded plain wire reinforcement shall be considered developed by embedment of
two cross wires with the closer cross wire not less than 50 mm from the point of the critical section.
However, ld shall not be less than
ld= 3.3 (Ab/s)(fy/λ√ )
EQUATION 516.8-1
where ld is measured from the point of the critical section to the outermost crosswire, s is the spacing
between the wires to be developed, and λ as given in 516.2.4(d). Where reinforcement provided is in
excess of that required, ld may be reduced in accordance with 516.2.5. Length, ld, shall not be less than
150 mm except in computation of lap splices by 516.19.
FIGURE 516.8-1 Development of welded plain wire reinforcement
All rights reserved
316 / 496
516.9 DEVELOPMENT OF FLEXURAL REINFORCEMENT - GENERAL
FIGURE 516.9-1 Lap splices of welded deformed wire reinforcement.
516.9.1
Development of tension reinforcement by bending across the web to be anchored or made
continuous with reinforcement on the opposite face of member shall be permitted.
516.9.2
Critical sections for development of reinforcement in flexural members are at points of
maximum stress and at points within the span where adjacent reinforcement terminates, or is
bent. Provisions of 516.11.3 must be satisfied.
FIGURE 516.9.2-1 Development of flexural reinforcement in a typical continuous beam.
All rights reserved
317 / 496
516.9.3
Reinforcement shall extend beyond the point at which it is no longer required to resist flexure
for a distance equal to d or 12db, whichever is greater, except at supports of simple spans and at
free end of cantilevers.
516.9.4
Continuing reinforcement shall have an embedment length not less than ld beyond the point
where bent or terminated tension reinforcement is no longer required to resist flexure.
516.9.5
Flexural reinforcement shall not be terminated in a tension zone unless 516.9.5.1, 516.9.5.2, or
516.9.5.3 is satisfied.
516.9.5.1
Vu at the cutoff point does not exceed (2/3)φVn.
516.9.5.2
Stirrup area in excess of that required for shear and torsion is provided along each
terminated bar or wire over a distance (3/4)d from the termination point. Excess stirrup
area shall be not less than 0.41bws/fyt. Spacing s shall not exceed d/(8βb).
516.9.5.3
For No. 36 bars and smaller, continuing reinforcement provides double the area required for
flexure at the cutoff point and Vu does not exceed (3/4)φVn.
516.9.6
Adequate anchorage shall be provided for tension reinforcement in flexural members where
reinforcement stress is not directly proportional to moment, such as: sloped, stepped, or
tapered footings; brackets; deep flexural members; or members in which tension reinforcement
is not parallel to compression face. See 516.11.4 and 516.12.4 for deep flexural members.
FIGURE 516.9.6-1 Member largely dependent on end anchorage.
516.10 DEVELOPMENT OF POSITIVE MOMENT REINFORCEMENT
516.10.1
At least one-third the positive moment reinforcement in simple members and one-fourth the
positive moment reinforcement in continuous members shall extend along the same face of
All rights reserved
318 / 496
member into the support. In beams, such reinforcement shall extend into the support at least
150 mm.
516.10.2
When a flexural member is part of a primary seismic-load-resisting system, positive moment
reinforcement required to be extended into the support by 516.10.1 shall be anchored to
develop fy in tension at the face of support.
516.10.3
At simple supports and at points of inflection, positive moment tension reinforcement shall be
limited to a diameter such that ld computed for fy by 516.2 satisfies Equation 516.10.3-1; except,
Equation 516.10.3-1 need not be satisfied for reinforcement terminating beyond centerline of
simple supports by a standard hook, or a mechanical anchorage at least equivalent to a standard
hook.
ld ≤ ( Mn/Vu) + la
EQUATION 516.10.3-1
where:
Mn is calculated assuming all reinforcement at the section to be stressed to fy;
Vu is calculated at the section;
la at a support shall be the embedment length beyond center of support; or
la at a point of inflection shall be limited to d or 12db ,
whichever is greater.
An increase of 30 percent in the value of Mn /Vu shall be permitted when the ends of
reinforcement are confined by a compressive reaction.
FIGURE 516.10.3-1 Concept for determining maximum bar size per 516.10.3.
All rights reserved
319 / 496
516.10.4
At simple supports of deep beams, positive moment tension reinforcement shall be anchored to
develop fy in tension at the face of the support . At interior supports of deep beams, positive
moment tension reinforcement shall be continuous or be spliced with that of the adjacent
spans.
516.11 DEVELOPMENT OF NEGATIVE MOMENT REINFORCEMENT
516.11.1
Negative moment reinforcement in a continuous, restrained, or cantilever member, or in any
member of a rigid frame, shall be anchored in or through the supporting member by
embedment length, hooks, or mechanical anchorage.
516.11.2
Negative moment reinforcement shall have an embedment length into the span as required by
516.1 and 516.9.3.
516.11.3
At least one-third the total tension reinforcement provided for negative moment at a support
shall have an embedment length beyond the point of inflection not less than d, 12db, or ln/16,
whichever is greater.
516.11.4
At interior supports of deep flexural members, negative moment tension reinforcement shall be
continuous with that of the adjacent spans.
516.12 DEVELOPMENT OF WEB REINFORCEMENT
516.12.1
Web reinforcement shall be as close to the compression and tension surfaces of the member as
cover requirements and proximity of other reinforcement permits.
516.12.2
(ACI 12.12.2) — Ends of single leg, simple U-, or multiple Ustirrups shall be anchored as required
by 516.12.2.1 through 516.12.2.5.
516.12.2.1
For No. 16 bar and MD200 wire, and smaller, and for No. 19, No. 22, and No. 25 bars with fyt
of 280 MPa or less, a standard hook around longitudinal reinforcement.
All rights reserved
320 / 496
FIGURE 516.12.2.1-1 Development of negative moment reinforcement.
516.12.2.2
For No. 19, No. 22, and No. 25 stirrups with fyt greater than 280 MPa, a standard stirrup
hook around a longitudinal bar plus an embedment between midheight of the member and
the outside end of the hook equal to or greater than 0.17dbfyt /(λ √ ).
516.12.2.3
For each leg of welded plain wire reinforcement forming simple U-stirrups, either:
All rights reserved
321 / 496
(a) Two longitudinal wires spaced at a 50 mm spacing along the member at the top of the U;
or
(b) One longitudinal wire located not more than d/4 from the compression face and a
second wire closer to the compression face and spaced not less than 50 mm from the
first wire. The second wire shall be permitted to be located on the stirrup leg beyond a
bend, or on a bend with an inside diameter of bend not less than 8db.
FIGURE 516.12.2.3-1 Anchorage in compression zone of welded plain wire reinforcement U-stirrups.
516.12.2.4
For each end of a single leg stirrup of welded wire reinforcement, two longitudinal wires at a
minimum spacing of 50 mm and with the inner wire at least the greater of d/4 or 50 mm
from d/2. Outer longitudinal wire at tension face shall not be farther from the face than the
portion of primary flexural reinforcement closest to the face.
FIGURE 516.12.2.4-1 Anchorage of single leg welded wire reinforcement shear reinforcement.
516.12.2.5
In joist construction as defined in 512.11, for No. 13 bar and MD130 wire and smaller, a
standard hook.
All rights reserved
322 / 496
516.12.3
Between anchored ends, each bend in the continuous portion of a simple U-stirrup or multiple
Ustirrup shall enclose a longitudinal bar.
516.12.4
Longitudinal bars bent to act as shear reinforcement, if extended into a region of tension,shall
be continuous with longitudinal reinforcement and, if extended into a region of compression,
shall be anchored beyond mid-depth d/2 as specified for development length in 516.2 for that
part of fyt required to satisfy Equation 515.6.5-1.
516.12.5
Pairs of U-stirrups or ties so placed as to form a closed unit shall be considered properly spliced
when length of laps are 1.3ld. In members at least 450 mm deep, such splices with Abfyt not
more than 40 kN per leg shall be considered adequate if stirrup legs extend the full available
depth of member.
516.13 SPLICES OF REINFORCEMENT - GENERAL
516.13.1
Splices of reinforcement shall be made only as required or permitted on design drawings, or in
specifications, or as authorized by the licensed design professional.
516.13.2 LAP SPLICES
516.13.2.1
Lap splices shall not be used for bars larger than No. 36 except as provided in 516.15.2 and
519.8.2.3.
516.13.2.2
Lap splices of bars in a bundle shall be based on the lap splice length required for individual
bars within the bundle, increased in accordance with 516.4. Individual bar splices within a
bundle shall not overlap. Entire bundles shall not be lap spliced.
516.13.2.3
Bars spliced by noncontact lap splices in flexural members shall not be spaced transversely
farther apart than the smaller of one-fifth the required lap splice length, and 150 mm.
516.13.3 MECHANICAL AND WELDED SPLICES
516.13.3.1
Mechanical and welded splices shall be permitted.
516.13.3.2
A full mechanical splice shall develop in tension or compression, as required, at least 1.25fy
of the bar.
516.13.3.3
Except as provided in this code, all welding shall conform to “Structural Welding Code—
Reinforcing Steel” (AWS D1.4).
516.13.3.4
A full welded splice shall develop at least 1.25fy of the bar.
All rights reserved
323 / 496
516.13.3.5
Mechanical or welded splices not meeting requirements of 516.13.3.2 or 516.13.3.4 shall be
permitted only for No. 16 bars and smaller and in accordance with 516.14.5.
516.14 SPLICES OF DEFORMEND BARS AND DEFORMED WIRE IN TENSION
516.14.1
Minimum length of lap for tension lap splices shall be as required for Class A or B splice, but not
less than 300 mm, where:
Class A splice.................................................................................................................. 1.0ld
Class B splice.................................................................................................................. 1.3ld
where ld is calculated in accordance with 516.2 to develop fy, but without the 300 mm minimum
of 516.2.1 and without the modification factor of 516.2.5.
FIGURE 516.14.1-1 Clear spacing of spliced bars.
516.14.2
Lap splices of deformed bars and deformed wire in tension shall be Class B splices except that
Class A splices are allowed when:
(a) the area of reinforcement provided is at least twice that required by analysis over the entire
length of the splice; and
(b) one-half or less of the total reinforcement is spliced within the required lap length.
All rights reserved
324 / 496
516.14.3
When bars of different size are lap spliced in tension, splice length shall be the larger of ld of
larger bar and tension lap splice length of smaller bar.
516.14.4
Mechanical or welded splices used where area of reinforcement provided is less than twice that
required by analysis shall meet requirements of 516.13.3.2 or 516.13.3.4.
516.14.5
Mechanical or welded splices not meeting the requirements of 516.13.3.2 or 516.13.3.4 shall be
permitted for No. 16 bars and smaller if the requirements of 516.14.5.1 through 516.14.5.3 are
met:
516.14.5.1
Splices shall be staggered at least 600 mm.
516.14.5.2
In computing the tensile forces that can be developed at each section, the spliced
reinforcement stress shall be taken as the specified splice strength, but not greater than fy.
The stress in the unspliced reinforcement shall be taken as fy times the ratio of the shortest
length embedded beyond the section to ld, but not greater than fy.
TABLE 516.14.5.2-1 TENSION LAP SPLICES
Maximum percent of As spliced within required lap length
50
100
Equal to or greater than 2
Class A
Class B
Less than 2
Class B
Class B
*: Ratio of area of reinforcement provided to area of reinforcement required by analysis at splice
locations.
516.14.5.3
The total tensile force that can be developed at each section must be at least twice that
required by analysis, and at least 140 MPa times the total area of reinforcement provided.
516.14.6
Splices in tension tie members shall be made with a full mechanical or full welded splice in
accordance with 516.13.3.2 or 516.13.3.4 and splices in adjacent bars shall be staggered at least
750 mm.
516.15 SPLICES OF DEFORMED BARS IN COMPRESSION
516.15.1
Compression lap splice length shall be 0.071fydb , for fy of 420 MPa or less, or (0.13fy – 24)db for
fy greater than 420 MPa, but not less than 300 mm. For f΄c less than 21 MPa, length of lap shall
be increased by one-third.
516.15.2
All rights reserved
325 / 496
When bars of different size are lap spliced in compression, splice length shall be the larger of ldc
of larger bar and compression lap splice length of smaller bar. Lap splices of No. 43 and No. 57
bars to No. 36 and smaller bars shall be permitted.
516.15.3
Mechanical or welded splices used in compression shall meet requirements of 516.13.3.2 or
516.13.3.4.
516.15.4 END-BEARING SPLICES
516.15.4.1
In bars required for compression only, transmission of compressive stress by bearing of
square cut ends held in concentric contact by a suitable device shall be permitted.
516.15.4.2
Bar ends shall terminate in flat surfaces within 1.5 degrees of a right angle to the axis of the
bars and shall be fitted within 3 degrees of full bearing after assembly.
516.15.4.3
End-bearing splices shall be used only in members containing closed ties, closed stirrups, or
spirals.
516.16 SPLICE REQUIREMENTS FOR COLUMNS
516.16.1
Lap splices, mechanical splices, buttwelded splices, and end-bearing splices shall be used with
the limitations of 516.16.2 through 516.16.4. A splice shall satisfy requirements for all load
combinations for the column.
516.16.2 LAP SPLICES IN COLUMNS
516.16.2.1
Where the bar stress due to factored loads is compressive, lap splices shall conform to
516.15.1, 516.15.2, and, where applicable, to 516.16.2.4 or 516.16.2.5.
516.16.2.2
Where the bar stress due to factored loads is tensile and does not exceed 0.5fy in tension,
lap splices shall be Class B tension lap splices if more than one-half of the bars are spliced at
any section, or Class A tension lap splices if half or fewer of the bars are spliced at any
section and alternate lap splices are staggered by ld.
516.16.2.3
Where the bar stress due to factored loads is greater than 0.5fy in tension, lap splices shall
be Class B tension lap splices.
516.16.2.4
In tied reinforced compression members, where ties throughout the lap splice length have
an effective area not less than 0.0015hs in both directions, lap splice length shall be
permitted to be multiplied by 0.83, but lap length shall not be less than 300 mm. Tie legs
perpendicular to dimension h shall be used in determining effective area.
516.16.2.5
All rights reserved
326 / 496
In spirally reinforced compression members, lap splice length of bars within a spiral shall be
permitted to be multiplied by 0.75, but lap length shall not be less than 300 mm.
516.16.3 MECHANICAL OR WELDED SPLICES IN COLUMNS
Mechanical or welded splices in columns shall meet the requirements of 516.13.3.2 or
516.13.3.4.
FIGURE 516.16.3-1 Example application of 516.16.2.4.
516.16.4 END-BEARING SPLICES IN COLUMNS
End-bearing splices complying with 516.15.4 shall be permitted to be used for column bars
stressed in compression provided the splices are staggered or additional bars are provided at
splice locations. The continuing bars in each face of the column shall have a tensile strength,
based on fy, not less than 0.25fy times the area of the vertical reinforcement in that face.
516.17 SPLICES OF WELDED DEFORMED WIRE REINFORCEMENT ON TENSION
516.17.1
Minimum lap splice length of welded deformed wire reinforcement measured between the ends
of each reinforcement sheet shall be not less than the larger of 1.3ld and 200 mm, and the
overlap measured between outermost cross wires of each reinforcement sheet shall be not less
than 50 mm, where ld is calculated in accordance with 516.7 to develop fy.
516.17.2
Lap splices of welded deformed wire reinforcement, with no cross wires within the lap splice
length, shall be determined as for deformed wire.
516.17.3
Where any plain wires, or deformed wires larger than MD200, are present in the welded
deformed wire reinforcement in the direction of the lap splice or where welded deformed wire
reinforcement is lap spliced to welded plain wire reinforcement, the reinforcement shall be lap
spliced in accordance with 516.18.
516.18 SPLICES OF WELDED PLAIN WIRE REINFORCEMENT IN TENSION
Minimum length of lap for lap splices of welded plain wire reinforcement shall be in accordance with
516.18.1 and 516.18.2.
516.18.1
All rights reserved
327 / 496
Where As provided is less than twice that required by analysis at splice location, length of
overlap measured between outermost cross wires of each reinforcement sheet shall be not less
than the largest of one spacing of cross wires plus 50 mm, 1.5ld, and 150 mm, where ld is
calculated in accordance with 516.8 to develop fy.
516.18.2
Where As provided is at least twice that required by analysis at splice location, length of overlap
measured between outermost cross wires of each reinforcement sheet shall not be less than the
larger of 1.5ld, and 50 mm, where ld is calculated in accordance with 516.8 to develop fy.
SECTION 517 TWO-WAY SLAB SYSTEMS
517.1 SCOPE
517.1.1
Provisions of Section 517 shall apply for design of slab systems reinforced for flexure in more
than one direction, with or without beams between supports.
517.1.2
For a slab system supported by columns or walls, dimensions c1, c2, and ln shall be based on an
effective support area defined by the intersection of the bottom surface of the slab, or of the
drop panel or shear cap if present, with the largest right circular cone, right pyramid, or tapered
wedge whose surfaces are located within the column and the capital or bracket and are oriented
no greater than 45 degrees to the axis of the column.
517.1.3
Solid slabs and slabs with recesses or pockets made by permanent or removable fillers between
ribs or joists in two directions are included within the scope of Section 517.
517.1.4
Minimum thickness of slabs designed in accordance with Section 517 shall be as required by
513.5.3.
517.2 GENERAL
517.2.1
Column strip is a design strip with a width on each side of a column centerline equal to 0.25l2 or
0.25l1, whichever is less. Column strip includes beams, if any.
517.2.2
Middle strip is a design strip bounded by two column strips.
517.2.3
A panel is bounded by column, beam, or wall centerlines on all sides.
517.2.4
For monolithic or fully composite construction, a beam includes that portion of slab on each side
of the beam extending a distance equal to the projection of the beam above or below the slab,
whichever is greater, but not greater than four times the slab thickness.
All rights reserved
328 / 496
FIGURE 517.2.4-1 Examples of the portion of slab to be included with the beam under 517.2.4.
517.2.5
When used to reduce the amount of negative moment reinforcement over a column or
minimum required slab thickness, a drop panel shall:
(a) project below the slab at least one-quarter of the adjacent slab thickness; and
(b) extend in each direction from the centerline of support a distance not less than one-sixth the
span length measured from center-to-center of supports in that direction.
517.2.6
When used to increase the critical condition section for shear at a slab-column joint, a shear cap
shall project below the slab and extend a minimum horizontal distance from the face of the
column that is equal to the thickness of the projection below the slab soffit.
517.3 SLAB REINFORCEMENT
517.3.1
Area of reinforcement in each direction for two-way slab systems shall be determined from
moments at critical sections, but shall not be less than required by 506.12.2.1.
517.3.2
Spacing of reinforcement at critical sections shall not exceed two times the slab thickness,
except for portions of slab area of cellular or ribbed construction. In the slab over cellular
spaces, reinforcement shall be provided as required by 506.12.
517.3.3
Positive moment reinforcement perpendicular to a discontinuous edge shall extend to the edge
of slab and have embedment, straight or hooked, at least 150 mm in spandrel beams, columns,
or walls.
517.3.4
Negative moment reinforcement perpendicular to a discontinuous edge shall be bent, hooked,
or otherwise anchored in spandrel beams, columns, or walls, and shall be developed at face of
support according to provisions of Section 516.
517.3.5
Where a slab is not supported by a spandrel beam or wall at a discontinuous edge, or where a
slab cantilevers beyond the support, anchorage of reinforcement shall be permitted within the
slab.
517.3.6
At exterior corners of slabs supported by edge walls or where one or more edge beams have a
value of αf greater than 1.0, top and bottom slab reinforcement shall be provided at exterior
corners in accordance with 517.3.6.1 through 517.3.6.4.
517.3.6.1
All rights reserved
329 / 496
Corner reinforcement in both top and bottom of slab shall be sufficient to resist a moment
per unit of width equal to the maximum positive moment per unit width in the slab panel.
517.3.6.2
The moment shall be assumed to be about an axis perpendicular to the diagonal from the
corner in the top of the slab and about an axis parallel to the diagonal from the corner in the
bottom of the slab.
517.3.6.3
Corner reinforcement shall be provided for a distance in each direction from the corner
equal to one-fifth the longer span.
All rights reserved
330 / 496
FIGURE 517.3.6.3-1 Slab corner reinforcement.
517.3.6.4
Corner reinforcement shall be placed parallel to the diagonal in the top of the slab and
perpendicular to the diagonal in the bottom of the slab. Alternatively, reinforcement shall be
placed in two layers parallel to the sides of the slab in both the top and bottom of the slab.
All rights reserved
331 / 496
517.3.7
When a drop panel is used to reduce the amount of negative moment reinforcement over the
column of a flat slab, the dimensions of the drop panel shall be in accordance with 517.2.5. In
computing required slab reinforcement, the thickness of the drop panel below the slab shall not
be assumed to be greater than one-quarter the distance from the edge of drop panel to the face
of column or column capital.
517.3.8 DETAILS OF REINFORCEMENT IN SLABS WITHOUT BEAMS
517.3.8.1
In addition to the other requirements of 517.3, reinforcement in slabs without beams shall
have minimum extensions as prescribed in Figure 517.3.8.3-1.
517.3.8.2
Where adjacent spans are unequal, extensions of negative moment reinforcement beyond
the face of support as prescribed in Figure 517.3.8.3-1 shall be based on requirements of the
longer span.
517.3.8.3
Bent bars shall be permitted only when depth-span ratio permits use of bends of 45 degrees
or less.
FIGURE 517.3.8.3-1 Minimum extensions for reinforcement in slabs without beams.
517.3.8.4
In frames where two-way slabs act as primary members resisting lateral loads, lengths of
reinforcement shall be determined by analysis but shall not be less than those prescribed in
Figure 517.3.8.3-1.
All rights reserved
332 / 496
517.3.8.5
All bottom bars or wires within the column strip, in each direction, shall be continuous or
spliced with Class B tension splices or with mechanical or welded splices satisfying 516.13.3.
Splices shall be located as shown in Fig. A13.3.8. At least two of the column strip bottom
bars or wires in each direction shall pass within the region bounded by the longitudinal
reinforcement of the column and shall be anchored at exterior supports.
517.3.8.6
In slabs with shearheads and in lift-slab construction where it is not practical to pass the
bottom bars required by 517.3.8.5 through the column, at least two bonded bottom bars or
wires in each direction shall pass through the shearhead or lifting collar as close to the
column as practicable and be continuous or spliced with a Class A splice. At exterior
columns, the reinforcement shall be anchored at the shearhead or lifting collar.
517.4 OPENINGS IN SLAB SYSTEMS
517.4.1
Openings of any size shall be permitted in slab systems if shown by analysis that the design
strength is at least equal to the required strength set forth in 513.2 and 513.3, and that all
serviceability conditions, including the limits on deflections, are met.
517.4.2
As an alternate to analysis as required by A13.4.1, openings shall be permitted in slab systems
without beams only, in accordance with 517.4.2.1 through 517.4.2.4.
517.4.2.1
Openings of any size shall be permitted in the area common to intersecting middle strips,
provided total amount of reinforcement required for the panel without the opening is
maintained.
517.4.2.2
In the area common to intersecting column strips, not more than one-eighth the width of
column strip in either span shall be interrupted by openings. An amount of reinforcement
equivalent to that interrupted by an opening shall be added on the sides of the opening.
517.4.2.3
In the area common to one column strip and one middle strip, not more than one-quarter of
the reinforcement in either strip shall be interrupted by openings. An amount of
reinforcement equivalent to that interrupted by an opening shall be added on the sides of
the opening.
517.4.2.4
Shear requirements of 515.13.6 shall be satisfied.
517.5 DESIGN PROCEDURES
517.5.1
A slab system shall be designed by any procedure satisfying conditions of equilibrium and
geometric compatibility, if shown that the design strength at every section is at least equal to
the required strength set forth in 513.2 and 513.3, and that all serviceability conditions,
including limits on deflections, are met.
All rights reserved
333 / 496
517.5.1.1
Design of a slab system for gravity loads, including the slab and beams (if any) between
supports and supporting columns or walls forming orthogonal frames, by either the Direct
Design Method or the Equivalent Frame Method, shall be permitted.
517.5.1.2
For lateral loads, analysis of frames shall take into account effects of cracking and
reinforcement on stiffness of frame members.
517.5.1.3
Combining the results of the gravity load analysis with the results of the lateral load analysis
shall be permitted.
517.5.2
The slab and beams (if any) between supports shall be proportioned for factored moments
prevailing at every section.
517.5.3
When gravity load, wind, earthquake, or other lateral forces cause transfer of moment between
slab and column, a fraction of the unbalanced moment shall be transferred by flexure in
accordance with 517.5.3.2 through 517.5.3.4.
517.5.3.1
The fraction of unbalanced moment not transferred by flexure shall be transferred by
eccentricity of shear in accordance with 515.13.7.
517.5.3.2
A fraction of the unbalanced moment given by γfMu shall be considered to be transferred by
flexure within an effective slab width between lines that are one and one-half slab or drop
panel thickness (1.5h) outside opposite faces of the column or capital, where Mu is the
factored moment to be transferred and
γf = 1/(1 + (2 ⁄ 3)√
)
EQUATION 517.5.3.2-1
517.5.3.3
For nonprestressed slabs with unbalanced moments transferred between the slab and
columns, it shall be permitted to increase the value of γf given by Equation 517.5.3.2-1 in
accordance with the following:
(a) For edge columns with unbalanced moments about an axis parallel to the edge, γf = 1.0
provided that Vu at an edge support does not exceed 0.75φVc , or at a corner support
does not exceed 0.5φVc.
(b) For unbalanced moments at interior supports, and for edge columns with unbalanced
moments about an axis perpendicular to the edge, increase γf to as much as 1.25 times
the value from
Equation 517.5.3.2-1, but not more than γf = 1.0, provided that Vu at the support does
not exceed 0.4φVc. The net tensile strain εt calculated for the effective slab width
defined in 13.5.3.2 shall not be less than 0.010. The value of Vc in items (a) and (b) shall
be calculated in accordance with 515.13.2.1.
517.5.3.4
All rights reserved
334 / 496
Concentration of reinforcement over the column by closer spacing or additional
reinforcement shall be used to resist moment on the effective slab width defined in
517.5.3.2.
517.5.4
Design for transfer of load from slabs to supporting columns or walls through shear and torsion
shall be in accordance with Section 515.
SECTION 518 WALLS
518.1 SCOPE
518.1.1
Provisions of Section 518 shall apply for design of walls subjected to axial load, with or without
flexure.
518.1.2
Cantilever retaining walls are designed according to flexural design provisions of Section 514
with minimum horizontal reinforcement according to 518.3.3.
518.2 GENERAL
518.2.1
Walls shall be designed for eccentric loads,any lateral or other loads to which they are
subjected.
518.2.2
Walls subject to axial loads shall be designed in accordance with 518.2, 518.3, and either 518.4,
518.5, or 518.8.
518.2.3
Design for shear shall be in accordance with 515.11.
518.2.4
Unless otherwise demonstrated by an analysis, the horizontal length of wall considered as
effective for each concentrated load shall not exceed the smaller of the center-to-center
distance between loads, and the bearing width plus four times the wall thickness.
518.2.5
Compression members built integrally with walls shall conform to 514.8.2.
518.2.6
Walls shall be anchored to intersecting elements, such as floors and roofs; or to columns
pilasters, buttresses, of intersecting walls; and to footings.
518.2.7
Quantity of reinforcement and limits of thickness required by 518.3 and 518.5 shall be permitted
to be waived where structural analysis shows adequate strength and stability.
518.2.8
Transfer of force to footing at base of wall shall be in accordance with 519.8.
All rights reserved
335 / 496
518.3 MINIMUM REINFORCEMENT
518.3.1
Minimum vertical and horizontal reinforcement shall be in accordance with 518.3.2 and 518.3.3
unless a greater amount is required for shear by 515.9.8 and 515.9.9.
518.3.2
Minimum ratio of vertical reinforcement area to gross concrete area, ρl, shall be:
(a) 0.0012 for deformed bars not larger than No. 16 with fy not less than 420 MPa; or
(b) 0.0015 for other deformed bars; or
(c) 0.0012 for welded wire reinforcement not larger than MW200 or MD200.
518.3.3
Minimum ratio of horizontal reinforcement area to gross concrete area, ρt, shall be:
(a) 0.0020 for deformed bars not larger than No. 16 with fy not less than 420 MPa; or
(b) 0.0025 for other deformed bars; or
(c) 0.0020 for welded wire reinforcement not larger than MW200 or MD200.
518.3.4
Walls more than 250 mm thick, except basement walls, shall have reinforcement for each
direction placed in two layers parallel with faces of wall in accordance with the following:
(a) One layer consisting of not less than one-half and not more than two-thirds of total
reinforcement required for each direction shall be placed not less than 50 mm nor more
than one-third the thickness of wall from the exterior surface;
(b) The other layer, consisting of the balance of required reinforcement in that direction, shall be
placed not less than 20 mm nor more than one-third the thickness of wall from the interior
surface.
518.3.5
Vertical and horizontal reinforcement shall not be spaced farther apart than three times the wall
thickness, nor farther apart than 450 mm.
518.3.6
Vertical reinforcement need not be enclosed by lateral ties if vertical reinforcement area is not
greater than 0.01 times gross concrete area, or where vertical reinforcement is not required as
compression reinforcement.
518.3.7
In addition to the minimum reinforcement required by 518.3.1, not less than two No. 16 bars in
walls having two layers of reinforcement in both directions and one No. 16 bar in walls having a
single layer of reinforcement in both directions shall be provided around window, door, and
similar sized openings. Such bars shall be anchored to develop fy in tension at the corners of the
openings.
518.4 WALLS DESIGNED AS COMPRESSION MEMBERS
Except as provided in 518.5, walls subject to axial load or combined flexure and axial load shall be
designed as compression members in accordance with provisions of 514.2, 514.3, 514.10, 514.11,
514.14, 518.2, and 518.3.
All rights reserved
336 / 496
518.5 EMPIRICAL DESIGN METHOD
518.5.1
Walls of solid rectangular cross section shall be permitted to be designed by the empirical
provisions of 14.5 if the resultant of all factored loads is located within the middle third of the
overall thickness of the wall and all limits of 518.2, 518.3, and 518.5 are satisfied.
518.5.2
Design axial strength φPn of a wall satisfying limitations of 518.5.1 shall be computed by
Equation 518.5.2-1 unless designed in accordance with 518.4.
φPn =
[
(
) ]
EQUATION 518.5.2-1
where φ shall correspond to compression-controlled sections in accordance with 513.3.2.2 and
effective
length factor k shall be:
For walls braced top and bottom against lateral translation and
(a) Restrained against rotation at one or both ends
(top, bottom, or both)....................................................................................................0.8
(b) Unrestrained against rotation at both ends...................................................................1.0
For walls not braced against lateral translation .......................................................... 2.0
518.5.3
Minimum thisckness of walls designed by empirical design method
518.5.3.1
Thickness of bearing walls shall not be less than 1/25 the supported height or length,
whichever is shorter, nor less than 100 mm.
518.5.3.2
Thickness of exterior basement walls and foundation walls shall not be less than 190 mm.
518.6 NONBEARING WALLS
518.6.1
Thickness of nonbearing walls shall not be less than 100 mm, nor less than 1/30 the least
distance between members that provide lateral support.
518.7 WALLS AS GRADE BEAMS
518.7.1
Walls designed as grade beams shall have top and bottom reinforcement as required for
moment in accordance with provisions of 514.2 through 514.7. Design for shear shall be in
accordance with provisions of Section 515.
518.7.2
Portions of grade beam walls exposed above grade shall also meet requirements of 518.3.
518.8 ALTERNATIVE DESIGN OF SLENDER WALLS
518.8.1
When flexural tension controls the out-ofplane design of a wall, the requirements of 518.8
are considered to satisfy 514.10.
All rights reserved
337 / 496
518.8.2
Walls designed by the provisions of 518.8 shall satisfy 518.8.2.1 through 518.8.2.6.
518.8.2.1
The wall panel shall be designed as a simply supported, axially loaded member subjected
to an out-of-plane uniform lateral load, with maximum moments and deflections
occurring at midspan.
518.8.2.2
The cross section shall be constant over the height of the panel.
518.8.2.3
The wall shall be tension-controlled.
518.8.2.4
Reinforcement shall provide a design strength
φMn ≥ Mcr
EQUATION 518.8.2.4-1
where Mcr shall be obtained using the modulus of rupture, fr , given by Equation
513.5.2.3-3.
518.8.2.5
Concentrated gravity loads applied to the wall above the design flexural section shall be
assumed to be distributed over a width:
(a) Equal to the bearing width, plus a width on each side that increases at a slope of 2
vertical to 1 horizontal down to the design section; but
(b) Not greater than the spacing of the concentrated loads; and
(c) Not extending beyond the edges of the wall panel.
518.8.2.6
Vertical stress Pu /Ag at the midheight section shall not exceed 0.06f΄c.
518.8.3
Design moment strength φMn for combined flexure and axial loads at midheight shall be
φMn ≥ Mu
EQUATION 518.8.3-1
where
Mu = Mua + PuΔu
EQUATION 518.8.3-2
Mua is the maximum factored moment at midheight of wall due to lateral and eccentric vertical
loads, not including PΔ effects, and Δu is
(
)
EQUATION 518.8.3-3
Mu shall be obtained by iteration of deflections, or by Equation 518.8.3-4.
All rights reserved
338 / 496
EQUATION 518.8.3-4
(
)
where
Icr =
)(
(
)
EQUATION 518.8.3-5
and the value of Es /Ec shall not be taken less than 6.
518.8.4
Maximum out-of-plane deflection, Δs, due to service loads, including PΔ effects, shall not exceed
lc /150. If Ma, maximum moment at midheight of wall due to service lateral and eccentric
vertical loads, including PΔ effects, exceeds (2/3)Mcr , Δs shall be calculated by Equation 518.8.41
Δs = ( )
(
( )
)
(
( )
)
(
( )
)
EQUATION 518.8.4-1
If Ma does not exceed (2/3)Mcr , Δs shall be calculated by Equation 518.8.4-2
Δs=(Ma/Mcr) Δcr
EQUATION 518.8.4-2
where
Δcr =(5Mcrl c /48EcIg)
2
EQUATION 518.8.4-3
Δn =(5Mnl2c /48EcIcr)
EQUATION 518.8.4-4
Icr shall be calculated by Equation 518.8.3-5, and Ma shall be obtained by iteration of
deflections.
SECTION 519 FOOTINGS
519.1 SCOPE
519.1.1
Provisions of Section 519 shall apply for design of isolated footings and, where applicable, to
Acombined footings and mats.
519.1.2
Additional requirements for design of combined footings and mats are given in 519.10.
519.2 LOADS AND REACTIONS
519.2.1
Footings shall be proportioned to resist the factored loads and induced reactions, in accordance
with the appropriate design requirements of this Code and as provided in Section 519.
All rights reserved
339 / 496
519.2.2
Base area of footing or number and arrangement of piles shall be determined from unfactored
forces and moments transmitted by footing to soil or piles and permissible soil pressure or
permissible pile capacity determined through principles of soil mechanics.
519.2.3
For footings on piles, computations for moments and shears shall be permitted to be based on
the assumption that the reaction from any pile is concentrated at pile center.
519.3 FOOTINGS SUPPOTING CIRCULAR OR REGULAR POLYGON-SHAPED COLUMNS OR PEDESTALS
For location of critical sections for moment, shear, and development of reinforcement in footings, it
shall be permitted to treat circular or regular polygon-shaped concrete columns or pedestals as square
members with the same area.
519.4 MOMENT IN FOOTINGS
519.4.1
External moment on any section of a footing shall be determined by passing a vertical plane
through the footing, and computing the moment of the forces acting over entire area of footing
on one side of that vertical plane.
519.4.2
Maximum factored moment, Mu, for an isolated footing shall be computed as prescribed in
519.4.1 at critical sections located as follows:
(a) At face of column, pedestal, or wall, for footings supporting a concrete column, pedestal, or
wall;
(b) Halfway between middle and edge of wall, for footings supporting a masonry wall;
(c) Halfway between face of column and edge of steel base plate, for footings supporting a
column with steel base plate.
519.4.3
In one-way footings and two-way square footings, reinforcement shall be distributed uniformly
across entire width of footing.
519.4.4
In two-way rectangular footings, reinforcement shall be distributed in accordance with 519.4.4.1
and 519.4.4.2.
519.4.4.1
Reinforcement in long direction shall be distributed uniformly across entire width of footing.
519.4.4.2
For reinforcement in short direction, a portion of the total reinforcement, γsAs, shall be
distributed uniformly over a band width (centered on centerline of column or pedestal)
equal to the length of short side of footing. Remainder of reinforcement required in short
direction, (1 – γs)As, shall be distributed uniformly outside center band width of footing.
γs= 2/(β + 1)
EQUATION 519.4.4.2-1
where β is ratio of long to short sides of footing.
All rights reserved
340 / 496
519.5 SHEAR IN FOOTINGS
519.5.1
Shear strength of footings supported on soil or rock shall be in accordance with 515.13.
519.5.2
Location of critical section for shear in accordance with Section 515 shall be measured from face
of column, pedestal, or wall, for footings supporting a column, pedestal, or wall. For footings
supporting a column or pedestal with steel base plates, the critical section shall be measured
from location defined in 519.4.2(c).
519.5.3
Where the distance between the axis of any pile to the axis of the column is more than two
times the distance between the top of the pile cap and the top of the pile, the pile cap shall
satisfy 515.13 and 519.5.4. Other pile caps shall satisfy 515.13 and 519.5.4.
FIGURE 519.5.3-1 Modified critical perimeter for shear with overlapping critical perimeters.
519.5.4
Computation of shear on any section through a footing supported on piles shall be in accordance
with 519.5.4.1, 519.5.4.2, and 519.5.4.3.
519.5.4.1
Entire reaction from any pile with its center located dpile /2 or more outside the section shall be
considered as producing shear on that section.
519.5.4.2
Reaction from any pile with its center located dpile /2 or more inside the section shall be
considered as producing no shear on that section.
519.5.4.3
For intermediate positions of pile center, the portion of the pile reaction to be considered as
producing shear on the section shall be based on straight-line interpolation between full value at
dpile /2 outside the section and zero value at dpile /2 inside the section.
519.6 DEVELOPMENT OF REINFORCEMENT IN FOOTINGS
519.6.1
Development of reinforcement in footings shall be in accordance with Section 516.
All rights reserved
341 / 496
519.6.2
Calculated tension or compression in reinforcement at each section shall be developed on each
side of that section by embedment length, hook (tension only) or mechanical device, or a
combination thereof.
519.6.3
Critical sections for development of reinforcement shall be assumed at the same locations as
defined in 519.4.2 for maximum factored moment, and at all other vertical planes where
changes of section or reinforcement occur. See also 516.9.6.
519.7 MINIMUM FOOTING DEPTH
Depth of footing above bottom reinforcement shall not be less than 150 mm for footings on soil, nor
less than 300 mm for footings on piles.
519.8 TRANSFER OF FORCE AT BASE OF COLUMN, WALL, OR REINFORCED PEDESTAL
519.8.1
Forces and moments at base of column, wall, or pedestal shall be transferred to supporting
pedestal or footing by bearing on concrete and by reinforcement, dowels, and mechanical
connectors.
519.8.1.1
Bearing stress on concrete at contact surface between supported and supporting member
shall not exceed concrete bearing strength for either surface as given by 514.14.
519.8.1.2
Reinforcement, dowels, or mechanical connectors between supported and supporting
members shall be adequate to transfer:
(a) All compressive force that exceeds concrete bearing strength of either member;
(b) Any computed tensile force across interface.
In addition, reinforcement, dowels, or mechanical connectors shall satisfy 519.8.2 or
519.8.3.
519.8.1.3
If calculated moments are transferred to supporting pedestal or footing, then
reinforcement, dowels, or mechanical connectors shall be adequate to satisfy 516.17.
519.8.1.4
Lateral forces shall be transferred to supporting pedestal or footing in accordance with
shear-friction provisions of 515.8, or by other appropriate means.
519.8.2
In cast-in-place construction, reinforcement required to satisfy 519.8.1 shall be provided either
by extending longitudinal bars into supporting pedestal or footing, or by dowels.
519.8.2.1
For cast-in-place columns and pedestals, area of reinforcement across interface shall be not
less than 0.005Ag, where Ag is the gross area of the supported member.
519.8.2.2
For cast-in-place walls, area of reinforcement across interface shall be not less than
minimum vertical reinforcement given in 518.3.2.
All rights reserved
342 / 496
519.8.2.3
At footings, it shall be permitted to lap splice No. 43 and No. 57 longitudinal bars, in
compression only, with dowels to provide reinforcement required to satisfy 519.8.1. Dowels
shall not be larger than No. 36 bar and shall extend into supported member a distance not
less than the larger of ldc , of No. 43 or No. 57 bars and compression lap splice length of the
dowels, whichever is greater, and into the footing a distance not less than ldc of the dowels.
519.8.2.4
If a pinned or rocker connection is provided in cast-in-place construction, connection shall
conform to 519.8.1 and 519.8.3.
519.8.3
In precast construction, anchor bolts or suitable mechanical connectors shall be permitted for
satisfying 519.8.1. Anchor bolts shall be designed in accordance with Appendix B.
519.8.3.1
Connection between precast columns or pedestals and supporting members shall meet the
requirements of 520.5.1.3(a).
519.8.3.2
Connection between precast walls and supporting members shall meet the requirements of
520.5.1.3(b) and (c).
519.8.3.3
Anchor bolts and mechanical connections shall be designed to reach their design strength
before anchorage failure or failure of surrounding concrete. Anchor bolts shall be designed
in accordance with Appendix B.
519.9 SLOPED OR STEPPED FOOTINGS
519.9.1
In sloped or stepped footings, angle of slope or depth and location of steps shall be such that
design requirements are satisfied at every section.
519.9.2
Sloped or stepped footings designed as a unit shall be constructed to ensure action as a unit.
519.10 COMBINED FOOTINGS AND MATS
519.10.1
Footings supporting more than one column, pedestal, or wall (combined footings or mats) shall
be proportioned to resist the factored loads and induced reactions, in accordance with
appropriate design requirements of the code.
519.10.2
The direct design method of Section 517 shall not be used for design of combined footings and
mats.
519.10.3
Distribution of soil pressure under combined footings and mats shall be consistent with
properties of the soil and the structure and with established principles of soil mechanics.
All rights reserved
343 / 496
519.10.4
Minimum reinforcing steel in nonprestressed mat foundations shall meet the requirements of
506.12.2 in each principal direction. Maximum spacing shall not exceed 450 mm.
SECTION 520 PRECAST CONCRETE
520.1 SCOPE
520.1.1
All provisions of this Code, not specifically excluded and not in conflict with the provisions of
Chapter 16, shall apply to structures incorporating precast concrete structural members.
520.2 GENERAL
520.2.1
Design of precast members and connections shall include loading and restraint conditions
from initial fabrication to end use in the structure, including form removal, storage,
transportation, and erection.
520.2.2
When precast members are incorporated into a structural system, the forces and
deformations occurring in and adjacent to connections shall be included in the design.
520.2.3
Tolerances for both precast members and interfacing members shall be specified. Design of
precast members and connections shall include the effects of these tolerances.
520.2.4
In addition to the requirements for drawings and specifications in 1.2, (a) and (b) shall be
included in either the contract documents or shop drawings:
(a) Details of reinforcement, inserts and lifting devices required to resist temporary loads
from handling, storage, transportation, and erection;
(b) Required concrete strength at stated ages or stages of construction.
520.3 DISTRIBUTION OF FORCES AMONG MEMBERS
520.3.1
Distribution of forces that are perpendicular to the plane of members shall be established by
analysis or by test.
520.3.2
Where the system behavior requires inplane forces to be transferred between the members of a
precast floor or wall system, 520.3.2.1 and 520.3.2.2 shall apply.
520.3.2.1
In-plane force paths shall be continuous through both connections and members.
520.3.2.2
Where tension forces occur, a continuous path of steel or steel reinforcement shall be
provided.
All rights reserved
344 / 496
520.4 MEMBER DESIGN
520.4.1
In one-way precast floor and roof slabs and in one-way precast, prestressed wall panels, all not
wider than 3.7 m, and where members are not mechanically connected to cause restraint in the
transverse direction, the shrinkage and temperature reinforcement requirements of 506.12 in
the direction normal to the flexural reinforcement shall be permitted to be waived. This waiver
shall not apply to members that require reinforcement to resist transverse flexural stresses.
520.4.2
For precast, nonprestressed walls the reinforcement shall be designed in accordance with the
provisions of Sections 514 or 518, except that the area of horizontal and vertical reinforcement
each shall be not less than 0.001Ag, where Ag is the gross cross-sectional area of the wall panel.
Spacing of reinforcement shall not exceed 5 times the wall thickness nor 750 mm for interior
walls nor 450 mm for exterior walls.
520.5 STRUCTURAL INTEGRITY
520.5.1
Except where the provisions of 520.5.2 govern, the minimum provisions of 520.5.1.1 through
520.5.1.4 for structural integrity shall apply to all precast concrete structures.
520.5.1.1
Longitudinal and transverse ties required by 506.13.3 shall connect members to a lateral
loadresisting system.
520.5.1.2
Where precast elements form floor or roof diaphragms, the connections between
diaphragm and those members being laterally supported shall have a nominal tensile
strength capable of resisting not less than 4.4 kN per linear m.
520.5.1.3
Vertical tension tie requirements of 506.13.3 shall apply to all vertical structural members,
except cladding, and shall be achieved by providing connections at horizontal joints in
accordance with (a) through (c):
(a) Precast columns shall have a nominal strength in tension not less than 1.4Ag, in lb. For
columns with a larger cross section than required by consideration of loading, a reduced
effective area Ag, based on cross section required but not less than one-half the total
area, shall be permitted;
(b) Precast wall panels shall have a minimum of two ties per panel, with a nominal tensile
strength not less than 44 kN per tie;
(c) When design forces result in no tension at the base, the ties required by 520.5.1.3(b)
shall be permitted to be anchored into an appropriately reinforced concrete floor slabon-ground.
520.5.1.4
Connection details that rely solely on friction caused by gravity loads shall not be used.
520.5.2
For precast concrete bearing wall structures three or more stories in height, the minimum
provisions of 520.5.2.1 through 520.5.2.5 shall apply.
All rights reserved
345 / 496
FIGURE 520.5.2-1 Typical arrangement of tensile ties in large panel structures.
520.5.2.1
Longitudinal and transverse ties shall be provided in floor and roof systems to provide a
nominal strength of 22 kN per meter of width or length. Ties shall be provided over interior
wall supports and between members and exterior walls. Ties shall be positioned in or within
600 mm of the plane of the floor or roof system.
520.5.2.2
Longitudinal ties parallel to floor or roof slab spans shall be spaced not more than 3 m on
centers. Provisions shall be made to transfer forces around openings.
520.5.2.3
Transverse ties perpendicular to floor or roof slab spans shall be spaced not greater than the
bearing wall spacing.
520.5.2.4
Ties around the perimeter of each floor and roof, within 1.2 m of the edge, shall provide a
nominal strength in tension not less than 70 kN.
520.5.2.5
Vertical tension ties shall be provided in all walls and shall be continuous over the height of
the building. They shall provide a nominal tensile strength not less than 44 kN per horizontal
meter of wall. Not less than two ties shall be provided for each precast panel.
520.6 CONNECTION AND BEARINBG DESIGN
520.6.1
Forces shall be permitted to be transferred between members by grouted joints, shear keys,
mechanical connectors, reinforcing steel connections, reinforced topping, or a combination of
these means.
520.6.1.1
The adequacy of connections to transfer forces between members shall be determined by
analysis or by test. Where shear is the primary result of imposed loading, it shall be
permitted to use the provisions of 515.8 as applicable.
520.6.1.2
When designing a connection using materials with different structural properties, their
relative stiffnesses, strengths, and ductilities shall be considered.
All rights reserved
346 / 496
520.6.2
Bearing for precast floor and roof members on simple supports shall satisfy 520.6.2.1 and
520.6.2.2.
FIGURE 520.6.2-1 Bearing length on support.
520.6.2.1
The allowable bearing stress at the contact surface between supported and supporting
members and between any intermediate bearing elements shall not exceed the bearing
strength for either surface or the bearing element, or both. Concrete bearing strength shall
be as given in 514.14.
520.6.2.2
Unless shown by test or analysis that performance will not be impaired, (a) and (b) shall be
met:
(a) Each member and its supporting system shall have design dimensions selected so that,
after consideration of tolerances, the distance from the edge of the support to the end
of the precast member in the direction of the span is at least ln/180, but not less than:
For solid or hollow-core slabs................................................................................50 mm
For beams or stemmed members .........................................................................75 mm
(b) Bearing pads at unarmored edges shall be set back a minimum of 13 mm from the face of
the support, or at least the chamfer dimension at chamfered edges.
520.6.2.3
The requirements of 516.11.1 shall not apply to the positive bending moment reinforcement
for statically determinate precast members, but at least one-third of such reinforcement
shall extend to the center of the bearing length, taking into account permitted tolerances in
506.5.2.2 and 520.2.3.
520.7 ITEMS EMBEDDED AFTER CONCRETE PLACEMENT
520.7.1
When approved by the licensed design professional, embedded items (such as dowels or inserts) that
either protrude from the concrete or remain exposed for inspection shall be permitted to be
embedded while the concrete is in a plastic state provided that 520.7.1.1, 520.7.1.2, and 520.7.1.3 are
met.
All rights reserved
347 / 496
520.7.1.1
Embedded items are not required to be hooked or tied to reinforcement within the concrete.
520.7.1.2
Embedded items are maintained in the correct position while the concrete remains plastic.
520.7.1.3
The concrete is properly consolidated around the embedded item.
520.8 MARKING AND IDENTIFICATION
520.8.1
Each precast member shall be marked to indicate its location and orientation in the structure
and date of manufacture.
520.8.2
Identification marks shall correspond to placing drawings.
520.9 HANDLING
520.9.1
Member design shall consider forces and distortions during curing, stripping, storage,
transportation, and erection so that precast members are not overstressed or otherwise
damaged.
520.9.2
During erection, precast members and structures shall be adequately supported and braced to
ensure proper alignment and structural integrity until permanent connections are completed.
520.10 STRENGTH ECALUATION OF PRECAST CONSTRUCTION
520.10.1
A precast element to be made composite with cast-in-place concrete shall be permitted to be
tested in flexure as a precast element alone in accordance with 520.10.1.1 and 520.10.1.2.
520.10.1.1
Test loads shall be applied only when calculations indicate the isolated precast element will
not be critical in compression or buckling.
520.10.1.2
The test load shall be that load which, when applied to the precast member alone, induces
the same total force in the tension reinforcement as would be induced by loading the
composite member with the test load required by 915.3.2.
520.10.2
The provisions of 915.5 shall be the basis for acceptance or rejection of the precast element.
All rights reserved
348 / 496
SECTION 521 EARTHQUAKE RESISTANT STRUCTURES
521.1 GENERAL REQUIREMENTS
521.1.1 SCOPE
521.1.1.1
Section 521 contains requirements for design and construction of reinforced concrete
members of a structure for which the design forces, related to earthquake motions, have
been determined on the basis of energy dissipation in the nonlinear range of response.
521.1.1.2
All structures shall be assigned to a seismic design category (SDC) in accordance with
Chapter 3.
521.1.1.3
All members shall satisfy requirements of this Chapter. Structures assigned to SDC B, C, D, E,
or F also shall satisfy 521.1.1.4 through 521.1.1.8, as applicable.
521.1.1.4
Structures assigned to SDC B shall satisfy 521.1.2.
521.1.1.5
Structures assigned to SDC C shall satisfy 521.1.2 and 521.1.8.
521.1.1.6
Structures assigned to SDC D, E, or F shall satisfy 521.1.2 through 521.1.8, and 521.11
through 521.13.
521.1.1.7
Structural systems designated as part of the seismic-force-resisting system shall be
restricted to those designated by the legally adopted general building code of determined by
other authority having jurisdiction in areas without a legally adopted building code. Except
for SDC A, for which Section 521 does not apply, the following provisions shall be satisfied
for each structural system designated as part of the seismic-forceresisting system, regardless
of the SDC:
(a) Ordinary moment frames shall satisfy 521.2.
(b) Ordinary reinforced concrete structural walls and ordinary precast structural walls need
not satisfy any provisions in Section 521.
(c) Intermediate moment frames shall satisfy 521.3. Intermediate precast structural walls
shall satisfy 521.4.
(d) Intermediate precast walls shall satisfy 521.4.
(e) Special moment frames shall satisfy 521.5 through 521.8.
(f) Special structural walls shall satisfy 521.9.
(g) Special structural walls constructed using precast concrete shall satisfy 521.10.
All special moment frames and special structural walls shall also satisfy 521.1.3
through521.1.7.
521.1.1.8
A reinforced concrete structural system not satisfying the requirements of this chapter shall
be permitted if it is demonstrated by experimental evidence and analysis that the proposed
system will have strength and toughness equal to or exceeding those provided by a
comparable monolithic reinforced concrete structure satisfying this chapter.
All rights reserved
349 / 496
521.1.2 ANALYSIS AND PROPORTIONING OF STRUCTURAL MEMBERS
521.1.2.1
The interaction of all structural and nonstructural members that affect the linear and
nonlinear response of the structure to earthquake motions shall be considered in the
analysis.
521.1.2.2
Rigid members assumed not to be a part of the seismic-force-resisting system shall be
permitted provided their effect on the response of the system is considered and
accommodated in the structural design. Consequences of failure of structural and
nonstructural members that are not a part of the seismic-force-resisting system shall be
considered.
521.1.2.3
Structural members extending below the base of structure that are required to transmit
forces resulting from earthquake effects to the foundation shall comply with the
requirements of Section 521 that are consistent with the seismic-force-resisting system
above the base of structure.
521.1.3 STRENGTH REDUCTION FACTORS
Strength reduction factors shall be as given in 513.3.4.
521.1.4 CONCRETE IN SPECIAL MOMENT FRAMES AND SPECIAL STRUCTURAL WALLS
521.1.4.1
Requirements of 521.1.4 apply to special moment frames and special structural walls and
coupling beams.
521.1.4.2
Specified compressive strength of concrete, f΄c, shall be not less than 21 MPa.
521.1.5 REINFORCEMENT ON SPECIAL MOMENT FRAMES AND SPECIAL STRUCTURAL WALLS
521.1.5.1
Requirements of 521.1.5 apply to special moment frames and special structural walls and
coupling beams.
521.1.5.2
Deformed reinforcement resisting earthquake-induced flexural and axial forces in frame
members, structural walls, and coupling beams, shall comply with ASTM A706M. ASTM
A615M Grades 280 and 420 reinforcement shall be permitted in these members if:
(a) The actual yield strength based on mill tests does not exceed fy by more than 125 MPa;
and
(b) The ratio of the actual tensile strength to the actual yield strength is not less than 1.25.
521.1.5.3
Prestressing steel resisting earthquakeinduced flexural and axial loads in frame members
and in precast structural walls shall comply with ASTM A416M or A722M.
521.1.5.4
The value of fyt used to compute the amount of confinement reinforcement shall not exceed
700 MPa.
All rights reserved
350 / 496
521.1.5.5
The value of fy or fyt used in design of shear reinforcement shall conform to 515.3.3.
521.1.6 MECHANICAL SPLICES IN SPECIAL MOMENT FRAMES AND SPECIAL STRUCTURAL
WALLS
521.1.6.1
Mechanical splices shall be classified as either Type 1 or Type 2 mechanical splices, as
follows:
(a) Type 1 mechanical splices shall conform to 516.13.3.2;
(b) Type 2 mechanical splices shall conform to 516.13.3.2 and shall develop the specified
tensile strength of the spliced bar.
521.1.6.2
Type 1 mechanical splices shall not be used within a distance equal to twice the member
depth from the column or beam face for special moment frames or from sections where
yielding of the reinforcement is likely to occur as a result of inelastic lateral displacements.
Type 2 mechanical splices shall be permitted to be used at any location.
521.1.7 WELDED SPLICES IN SPECIAL MOMENT FRAMES AND SPECIAL STRUCTURAL WALLS
521.1.7.1
Welded splices in reinforcement resisting earthquake-induced forces shall conform to
516.13.3.4 and shall not be used within a distance equal to twice the member depth from
the column or beam face for special moment frames or from sections where yielding of the
reinforcement is likely to occur as a result of inelastic lateral displacements.
521.1.7.2
Welding of stirrups, ties, inserts, or other similar elements to longitudinal reinforcement
that is required by design shall not be permitted.
521.1.8 ANCHORING TO CONCRETE
Anchors resisting earthquake-induced forces in structures assigned to SDC C, D, E, or F shall
conform
to the requirements of Chapter 3.
521.2 ORDINARY MOMENT FRAMES
521.2.1 SCOPE
Requirements of 521.2 apply to ordinary moment frames forming part of the seismic-forceresisting system.
521.2.2
Beams shall have at least two of the longitudinal bars continuous along both the top and bottom
faces. These bars shall be developed at the face of support.
521.2.3
Columns having clear height less than or equal to five times the dimension c1 shall be designed
for shear in accordance with 521.3.3.
All rights reserved
351 / 496
521.3 INTERMEDIATE MOMENT FRAMES
521.3.1 SCOPE
Requirements of 521.3 apply to intermediate moment frames forming part of the seismic-forceresisting system.
521.3.2
Reinforcement details in a frame member shall satisfy 521.3.4 if the factored axial compressive
load, Pu, for the member does not exceed Ag f΄c /10. If Pu is larger, frame reinforcement details
shall satisfy 521.3.5. Where a two-way slab system without beams forms a part of the seismicforce-resisting system, reinforcement details in any span resisting moments caused by E shall
satisfy 521.3.6.
521.3.3
φVn of beams and columns resisting earthquake effect, E, shall not be less than the smaller of (a)
and (b):
(a) The sum of the shear associated with development of nominal moment strengths of the
member at each restrained end of the clear span and the shear calculated for factored
gravity loads;
(b) The maximum shear obtained from design load combinations that include E, with E assumed
to be twice that prescribed by the legally adopted general building code for earthquakeresistant design.
521.3.4 BEAMS
521.3.4.1
The positive moment strength at the face of the joint shall be not less than one-third the
negative moment strength provided at that face of the joint. Neither the negative nor the
positive moment strength at any section along the length of the beam shall be less than onefifth the maximum moment strength provided at the face of either joint.
521.3.4.2
At both ends of the beam, hoops shall be provided over lengths not less than 2h measured
from the face of the supporting member toward midspan. The first hoop shall be located not
more than 50 mm from the face of the supporting member. Spacing of hoops shall not
exceed the smallest of (a), (b), (c), and (d):
(a) d/4;
(b) Eight times the diameter of the smallest longitudinal bar enclosed;
(c) 24 times the diameter of the hoop bar;
(d) 300 mm
All rights reserved
352 / 496
FIGURE 521.3.4.2-1 Design shears for intermediate moment frames.
521.3.4.3
Stirrups shall be spaced not more than d/2 throughout the length of the beam.
521.3.5 COLUMNS
521.3.5.1
Columns shall be spirally reinforced in accordance with 506.10.4 or shall conform with
521.3.5.2 through 521.3.5.4. Section 521.3.5.5 shall apply to all columns, and 521.3.5.6 shall
apply to all columns supporting discontinuous stiff members.
521.3.5.2
At both ends of the column, hoops shall be provided at spacing so over a length lo measured
from the joint face. Spacing so shall not exceed the smallest of (a), (b), (c), and (d):
All rights reserved
353 / 496
(a) Eight times the diameter of the smallest longitudinal bar enclosed;
(b) 24 times the diameter of the hoop bar;
(c) One-half of the smallest cross-sectional dimension of the column;
(d) 300 mm.
Length lo shall not be less than the largest of (e), (f), and (g):
(e) One-sixth of the clear span of the column;
(f) Maximum cross-sectional dimension of the column;
(g) 450 mm.
521.3.5.3
The first hoop shall be located not more than so /2 from the joint face.
521.3.5.4
Outside the length lo , spacing of transverse reinforcement shall conform to 506.10 and
515.4.1.
521.3.5.5
Joint transverse reinforcement shall conform to 515.12.
521.3.5.6
Columns supporting reactions from discontinuous stiff members, such as walls, shall be
provided with transverse reinforcement at the spacing, so , as defined in 521.3.5.2 over the
full height beneath the level at which the discontinuity occurs if the portion of factored axial
compressive force in these members related to earthquake effects exceeds Agf΄c/10. Where
design forces have been magnified to account for the overstrength of the vertical elements
of the seismicforce- resisting system, the limit of Agf΄c/10 shall be increased to Agf΄c/4. This
transverse reinforcement shall extend above and below the columns as required in
521.6.4.6(b).
521.3.6 TWO-WAY SLABS WITHOUT BEAMS
521.3.6.1
Factored slab moment at support including earthquake effects, E, shall be determined for
load combinations given in Equation 513.2.1-5 and 513.2.1-7. Reinforcement provided to
resist Mslab shall be placed within the column strip defined in 517.2.1.
521.3.6.2
Reinforcement placed within the effective width specified in 517.5.3.2 shall be proportioned
to resist γfMslab. Effective slab width for exterior and corner connections shall not extend
beyond the column face a distance greater than ct measured perpendicular to the slab span.
All rights reserved
354 / 496
FIGURE 521.3.6.2-1 Effective width for reinforcement placement in edge and corner connections.
Note: Applies to both top and bottom reinforcement
FIGURE 521.3.6.2-2 Location of reinforcement in slabs.
All rights reserved
355 / 496
FIGURE 521.3.6.2-3 Arrangement of reinforcement in slabs.
521.3.6.3
Not less than one-half of the reinforcement in the column strip at support shall be placed
within the effective slab width given in 517.5.3.2.
521.3.6.4
Not less than one-quarter of the top reinforcement at the support in the column strip shall
be continuous throughout the span.
521.3.6.5
Continuous bottom reinforcement in the column strip shall be not less than one-third of the
top reinforcement at the support in the column strip.
521.3.6.6
Not less than one-half of all bottom middle strip reinforcement and all bottom column strip
reinforcement at midspan shall be continuous and shall develop fy at face of support as
defined in 522.2.5.
521.3.6.7
At discontinuous edges of the slab, all top and bottom reinforcement at support shall be
developed at the face of support as defined in 522.2.5.
All rights reserved
356 / 496
521.3.6.8
At the critical sections for columns defined in 515.13.1.2, two-way shear caused by factored
gravity loads shall not exceed 0.4φVc, where Vc shall be calculated as defined in 515.13.2.1
for nonprestressed slabs and in 515.13.2.2 for prestressed slabs. It shall be permitted to
waive this requirement if the slab design satisfies requirements of 521.13.6.
521.4 INTERMEDIATE PRECAST STRUCTURAL WALLS
521.4.1 SCOPE
Requirements of 521.4 apply to intermediate precast structural walls forming part of the
seismic-forceresisting system.
521.4.2
In connections between wall panels, or between wall panels and the foundation, yielding shall
be restricted to steel elements or reinforcement.
521.4.3
Connections that are designed to yield shall be capable of maintaining 80 percent of their
design strength at the deformation induced by the design displacement or shall use Type 2
mechanical splices.
521.4.4
Elements of the connection that are not designed to yield shall develop at least 1.5Sy.
521.4.5
Wall piers not designed as part of a moment frame shall have transverse reinforcement designed
to resist the shear forces determined from 521.3.3. Spacing of transverse reinforcement shall not
exceed 200 mm. Transverse reinforcement shall be extended beyond the pier clear height for at
least 300 mm.
Exceptions:
1. Wall piers that satisfy 521.13.
2. Wall piers along a wall line within a story where other shear wall segments provide lateral
support to the wall piers and such segments have a total stiffness of at least six times the sum
of the stiffnesses of all the wall piers.
521.4.6
Wall segments with a horizontal length-to-thickness ratio less than 2.5 shall be designed as
columns.
521.5 FLEXURAL MEMBERS OF SPECIAL MOMENT FRAMES
521.5.1 SCOPE
Requirements of 521.5 apply to special moment frame members that form part of the seismicforce-resisting system and are proportioned primarily to resist flexure. These frame members
shall also satisfy the conditions of 521.5.1.1 through 521.5.1.4.
521.5.1.1
Factored axial compressive force on the member, Pu, shall not exceed Agf΄c /10.
521.5.1.2
Clear span for member, ln, shall not be less than four times its effective depth.
All rights reserved
357 / 496
521.5.1.3
Width of member, bw, shall not be less than the smaller of 0.3h and 250 mm.
521.5.1.4
Width of member, bw, shall not exceed width of supporting member, c2, plus a distance on
each side of supporting member equal to the smaller of (a) and (b):
(a) Width of supporting member, c2, and
(b) 0.75 times the overall dimension of supporting member, c1.
521.5.2 LONGITUDINAL REINFORCEMENT
FIGURE 521.5.2-1 Maximum effective width of wide beam and required transverse reinforcement.
All rights reserved
358 / 496
521.5.2.1
At any section of a flexural member, except as provided in 514.5.3, for top as well as for
bottom reinforcement, the amount of reinforcement shall not be less than that given by
Equation 514.5.1-1 but not less than 1.4bwd/fy, and the reinforcement ratio, ρ, shall not
exceed 0.025. At least two bars shall be provided continuously at both top and bottom.
521.5.2.2
Positive moment strength at joint face shall be not less than one-half the negative moment
strength provided at that face of the joint. Neither the negative nor the positive moment
strength at any section along member length shall be less than onefourth the maximum
moment strength provided at face of either joint.
521.5.2.3
Lap splices of flexural reinforcement shall be permitted only if hoop or spiral reinforcement
is provided over the lap length. Spacing of the transverse reinforcement enclosing the lapspliced bars shall not exceed the smaller of d/4 and 100 mm. Lap splices shall not be used:
(a) Within the joints;
(b) Within a distance of twice the member depth from the face of the joint; and
(c) Where analysis indicates flexural yielding is caused by inelastic lateral displacements of
the frame.
521.5.2.4
Mechanical splices shall conform to 521.1.6 and welded splices shall conform to 521.1.7.
521.5.3 TRANSVERSE REINFORCEMENT
521.5.3.1
Hoops shall be provided in the following regions of frame members:
(a) Over a length equal to twice the member depth measured from the face of the
supporting member toward midspan, at both ends of the flexural member;
(b) Over lengths equal to twice the member depth on both sides of a section where flexural
yielding is likely to occur in connection with inelastic lateral displacements of the frame.
FIGURE 521.5.3.1-1 Examples of overlapping hoops.
521.5.3.2
The first hoop shall be located not more than 2 in. from the face of a supporting member.
Spacing of the hoops shall not exceed the smallest of (a), (b), (c) and (d):
All rights reserved
359 / 496
(a) d/4;
(b) Eight times the diameter of the smallest longitudinal bars;
(c) 24 times the diameter of the hoop bars; and
(d) 300 mm.
521.5.3.3
Where hoops are required, longitudinal bars on the perimeter shall have lateral support
conforming to 506.10.5.3.
521.5.3.4
Where hoops are not required, stirrups with seismic hooks at both ends shall be spaced at a
distance not more than d/2 throughout the length of the member.
521.5.3.5
Stirrups or ties required to resist shear shall be hoops over lengths of members in 521.5.3.1.
521.5.3.6
Hoops in flexural members shall be permitted to be made up of two pieces of
reinforcement: a stirrup having seismic hooks at both ends and closed by a crosstie.
Consecutive crossties engaging the same longitudinal bar shall have their 90-degree hooks at
opposite sides of the flexural member. If the longitudinal reinforcing bars secured by the
crossties are confined by a slab on only one side of the flexural frame member, the 90degree hooks of the crossties shall be placed on that side.
521.5.4 SHEAR STRENGTH REQUIREMENTS
521.5.4.1 DESIGN FORCES
The design shear force, Ve , shall be determined from consideration of the statical forces on
the portion of the member between faces of the joints. It shall be assumed that moments of
opposite sign corresponding to probable flexural moment strength, Mpr, act at the joint
faces and that the member is loaded with the factored tributary gravity load along its span.
521.5.4.2 TRANSVERSE REINFORCEMENT
Transverse reinforcement over the lengths identified in 521.5.3.1 shall be proportioned to
resist shear
assuming Vc = 0 when both (a) and (b) occur:
(a) The earthquake-induced shear force calculated in accordance with 521.5.4.1 represents
one-half or
more of the maximum required shear strength within those lengths;
(b) The factored axial compressive force, Pu, including earthquake effects is less than
Agf΄c/20.
All rights reserved
360 / 496
FIGURE 521.5.4.2-1 Design shears for beams and columns.
521.6 SPECIAL MOMENT FRAME MEMBERS SUBJECTED TO BENDING AND AXIAL LOAD
521.6.1 SCOPE
Requirements of this section apply to special moment frame members that form part of the
seismic-forceresisting system and that resist a factored axial compressive force Pu under any
load combination exceeding Agf΄c/10. These frame members shall also satisfy the conditions of
521.6.1.1 and 521.6.1.2.
All rights reserved
361 / 496
521.6.1.1
The shortest cross-sectional dimension, measured on a straight line passing through the
geometric centroid, shall not be less than 300 mm.
521.6.1.2
The ratio of the shortest cross-sectional dimension to the perpendicular dimension shall not
be less than 0.4.
521.6.2 MINIMUM FLEXURAL STRENGTH OF COLUMNS
521.6.2.1
Columns shall satisfy 521.6.2.2 or 521.6.2.3.
521.6.2.2
The flexural strengths of the columns shall satisfy Equation 521.6.2.2-1
ΣMnc ≥ (1.2)ΣMnb
EQUATION 521.6.2.2-1
ΣMnc = sum of nominal flexural strengths of columns framing into the joint, evaluated at the
faces of the joint. Column flexural strength shall be calculated for the factored axial force,
consistent with the direction of the lateral forces considered, resulting in the lowest flexural
strength.
ΣMnb = sum of nominal flexural strengths of the beams framing into the joint, evaluated at
the faces of the joint. In T-beam construction, where the slab is in tension under moments at
the face of the joint, slab reinforcement within an effective slab width defined in 512.13
shall be assumed to contribute to Mnb if the slab reinforcement is developed at the critical
section for flexure. Flexural strengths shall be summed such that the column moments
oppose the beam moments. Equation 521.6.2.2-1 shall be satisfied for beam moments
acting in both directions in the vertical plane of the frame considered.
521.6.2.3
If 521.6.2.2 is not satisfied at a joint, the lateral strength and stiffness of the columns
framing into that joint shall be ignored when determining the calculated strength and
stiffness of the structure. These columns shall conform to 521.13.
521.6.3 LONGITUDINAL REINFORCEMENT
521.6.3.1
Area of longitudinal reinforcement, Ast , shall not be less than 0.01Ag or more than 0.06Ag.
521.6.3.2
Mechanical splices shall conform to 521.1.6 and welded splices shall conform to 521.1.7. Lap
splices shall be permitted only within the center half of the member length, shall be
designed as tension lap splices, and shall be enclosed within transverse reinforcement
conforming to 521.6.4.2 and 521.6.4.3.
521.6.4 TRANSVERSE REINFORCEMENT
521.6.4.1
Transverse reinforcement required in 521.6.4.2 through 521.6.4.4 shall be provided over a
length lo from each joint face and on both sides of any section where flexural yielding is
All rights reserved
362 / 496
likely to occur as a result of inelastic lateral displacements of the frame. Length lo shall not
be less than the largest of (a), (b), and (c):
(a) The depth of the member at the joint face or at the section where flexural yielding is
likely to occur;
(b) One-sixth of the clear span of the member; and
(c) 450 mm.
521.6.4.2
Transverse reinforcement shall be provided by either single or overlapping spirals satisfying
506.10.4, circular hoops, or rectilinear hoops with or without crossties. Crossties of the same
or smaller bar size as the hoops shall be permitted. Each end of the crosstie shall engage a
peripheral longitudinal reinforcing bar. Consecutive crossties shall be alternated end for end
along the longitudinal reinforcement. Spacing of crossties or legs of rectilinear hoops, hx,
within a cross
section of the member shall not exceed 350 mm on center.
The dimension xi from centerline to centerline of tie legs is not to exceed 350 mm. The term hx used in
Equation 521.6.4.3-1 taken as the largest value of xi.
FIGURE 521.6.4.2-1 Example of transverse reinforcement in columns.
521.6.4.3
Spacing of transverse reinforcement along the length lo of the member shall not exceed the
smallest of (a), (b), and (c):
(a) One-quarter of the minimum member dimension;
(b) Six times the diameter of the smallest longitudinal bar; and
(c) so, as defined by Equation 521.6.4.3-1
so= 100 + (350 – hx)/3
EQUATION 521.6.4.3-1
The value of so shall not exceed 150 mm and need not be taken less than 100 mm.
521.6.4.4
Amount of transverse reinforcement required in (a) or (b) shall be provided unless a larger
amount is required by 521.6.5.
All rights reserved
363 / 496
(a) The volumetric ratio of spiral or circular hoop reinforcement, ρs, shall not be less than
required by Equation 521.6.4.4-1
ρs = 0.12 (f΄c/fyt)
EQUATION 521.6.4.4-1
and shall not be less than required by Equation 521.6.4.4-3.
(b) The total cross-sectional area of rectangular hoop reinforcement, Ash, shall not be less
than required by Equation 521.6.4.4-2 and 521.6.4.4-3
Ash = 0.3 [sbc f΄c /fyt][( Ag/ Ach) – 1]
EQUATION 521.6.4.4-2
Ash = 0.09 (sbc f΄c/fyt)
EQUATION 521.6.4.4-3
521.6.4.5
Beyond the length lo specified in 521.6.4.1, the column shall contain spiral or hoop
reinforcement satisfying 506.10 with center-to-center spacing, s, not exceeding the smaller
of six times the diameter of the smallest longitudinal column bars and 150 mm, unless a
larger amount of transverse reinforcement is required by 521.6.3.2 or 521.6.5.
521.6.4.6
Columns supporting reactions from discontinued stiff members, such as walls, shall satisfy
(a) and (b):
(a) Transverse reinforcement as required in 521.6.4.2 through 521.6.4.4 shall be provided
over their full height at all levels beneath the discontinuity if the factored axial
compressive force in these members, related to earthquake effect, exceeds Agf΄c/10.
Where design forces have been magnified to account for the overstrength of the vertical
elements of the seismic-force-resisting system, the limit of Agf΄c/10 shall be increased
to Agf΄c/4.
(b) The transverse reinforcement shall extend into the discontinued member at least ld of
the largest longitudinal column bar, where ld is determined in accordance with 521.7.5.
Where the lower end of the column terminates on a wall, the required transverse
reinforcement shall extend into the wall at least ld of the largest longitudinal column bar
at the point of termination. Where the column terminates on a footing or mat, the
required transverse reinforcement shall extend at least 300 mm into the footing or mat.
521.6.4.7
If the concrete cover outside the confining transverse reinforcement specified in 521.6.4.1,
521.6.4.5, and 521.6.4.6 exceeds 100 mm, additional transverse reinforcement shall be
provided. Concrete cover for additional transverse reinforcement shall not exceed 100 mm
and spacing of additional transverse reinforcement shall not exceed 300 mm.
521.6.5 SHEAR STRENGTH REQUIREMENTS
521.6.5.1 DESIGN FORCES
The design shear force, Ve, shall be determined from consideration of the maximum forces
that can be generated at the faces of the joints at each end of the member. These joint
forces shall be determined using the maximum probable moment strengths, Mpr , at each
end of the member associated with the range of factored axial loads, Pu, acting on the
member. The member shears need not exceed those determined from joint strengths based
on Mpr of the transverse members framing into the joint. In no case shall Ve be less than the
factored shear determined by analysis of the structure.
All rights reserved
364 / 496
521.6.5.2 TRANSVERSE REINFORCEMENT
Transverse reinforcement over the lengths lo, identified in 521.6.4.1, shall be proportioned
to resist shear assuming Vc = 0 when both (a) and (b) occur:
(a) The earthquake-induced shear force, calculated in accordance with 521.6.5.1, represents
one-half or more of the maximum required shear strength within lo;
(b) The factored axial compressive force, Pu, including earthquake effects is less than
Agf΄c/20.
521.7 JOINTS OF SPECIAL MOMENT FRAMES
521.7.1 SCOPE
Requirements of 521.7 apply to beam-column joints of special moment frames forming part of
the seismicforce-resisting system.
521.7.2 GENERAL REQUIREMENTS
521.7.2.1
Forces in longitudinal beam reinforcement at the joint face shall be determined by assuming
that the stress in the flexural tensile reinforcement is 1.25fy.
521.7.2.2
Beam longitudinal reinforcement terminated in a column shall be extended to the far face of
the confined column core and anchored in tension according to 521.7.5 and in compression
according to Section 516.
521.7.2.3
Where longitudinal beam reinforcement extends through a beam-column joint, the column
dimension parallel to the beam reinforcement shall not be less than 20 times the diameter
of the largest longitudinal beam bar for normalweight concrete. For lightweight concrete,
the dimension shall be not less than 26 times the bar diameter.
521.7.3 TRANSVERSE REINFORCEMENT
521.7.3.1
Joint transverse reinforcement shall satisfy either 521.6.4.4(a) or 521.6.4.4(b), and shall also
satisfy 521.6.4.2, 521.6.4.3, and 521.6.4.7, except as permitted in 521.7.3.2.
521.7.3.2
Where members frame into all four sides of the joint and where each member width is at
least three-fourths the column width, the amount of reinforcement specified in 521.6.4.4(a)
or 521.6.4.4(b) shall be permitted to be reduced by half, and the spacing required in
521.6.4.3 shall be permitted to be increased to 150 mm within the overall depth h of the
shallowest framing member.
521.7.3.3
Longitudinal beam reinforcement outside the column core shall be confined by transverse
reinforcement passing through the column that satisfies spacing requirements of 521.5.3.2,
and requirements of 521.5.3.3 and 21.5.3.6, if such confinement is not provided by a beam
framing into the joint.
All rights reserved
365 / 496
521.7.4 SHEAR STRENGTH
521.7.4.1
Vn of the joint shall not be taken as greater than the values specified below for
normalweight concrete.
For joints confined on all four faces .......... 1.7√ Aj
For joints confined on three faces or
on two opposite faces............................... 1.2√ Aj
For others ................................................. 1.0√ Aj
A member that frames into a face is considered to provide confinement to the joint if at
least three-quarters of the face of the joint is covered by the framing member. Extensions of
beams at least one overall beam depth h beyond the joint face are permitted to be
considered as confining members. Extensions of beams shall satisfy 521.5.1.3, 521.5.2.1,
521.5.3.2, 521.5.3.3, and 521.5.3.6. A joint is considered to be confined if such confining
members frame into all faces of the joint.
Aj is the effective cross-sectional area within a joint computed from joint depth times
effective joint width. Joint depth shall be the overall depth of the column, h. Effective joint
width shall be the overall width of the column, except where a beam frames into a wider
column, effective joint width shall not exceed the smaller of (a) and (b):
(a) Beam width plus joint depth
(b) Twice the smaller perpendicular distance from longitudinal axis of beam to column side.
521.7.4.2
For lightweight concrete, the nominal shear strength of the joint shall not exceed threequarters of the limits given in 521.7.4.1.
FIGURE 521.7.4.2-1 Effective joint area.
All rights reserved
366 / 496
521.7.5 DEVELOPMENT LENGTH OF BARS IN TENSION
521.7.5.1
For bar sizes No. 10 through No. 36, the development length, ldh, for a bar with a Standard
90-degree hook in normalweight concrete shall not be less than the largest of 8db , 150 mm,
and the length required by Equation 521.7.5.1-1
ldh = fydb/ (5.4 √
)
EQUATION 521.7.5.1-1
For lightweight concrete, ldh for a bar with a standard 90-degree hook shall not be less than
the largest of 10db , 190 mm, and 1.25 times the length required by Equation 521.7.5.1-1.
The 90-degree hook shall be located within the confined core of a column or of a boundary
element.
521.7.5.2
For bar sizes No. 10 through No. 36, ld, the development length in tension for a straight bar,
shall not be less than the larger of (a) and (b):
(a) 2.5 times the length required by 521.7.5.1 if the depth of the concrete cast in one lift
beneath the bar does not exceed 300 mm;
(b) 3.25 times the length required by 521.7.5.1 if the depth of the concrete cast in one lift
beneath the bar exceeds 300 mm.
521.7.5.3
Straight bars terminated at a joint shall pass through the confined core of a column or of a
boundary element. Any portion of ld not within the confined core shall be increased by a
factor of 1.6.
521.8 SPECIAL MOMENT FRAMES CONSTRUCTED USING PRECAST CONCRETE
521.8.1 SCOPE
Requirements of 521.8 apply to special moment frames constructed using precast concrete
forming part of the seismic-force-resisting system.
521.8.2
Special moment frames with ductile connections constructed using precast concrete shall satisfy
(a) and (b) and all requirements for special moment frames constructed with cast-in-place
concrete:
(a) Vn for connections computed according to 515.8.4 shall not be less than 2Ve, where Ve is
calculated according to 521.5.4.1 or 521.6.5.1;
(b) Mechanical splices of beam reinforcement shall be located not closer than h/2 from the joint
face
and shall meet the requirements of 521.1.6.
521.8.3
Special moment frames with strong connections constructed using precast concrete shall satisfy
all requirements for special moment frames constructed with cast-in-place concrete, as well as
(a), (b), (c), and (d).
(a) Provisions of 521.5.1.2 shall apply to segments between locations where flexural yielding is
intended to occur due to design displacements;
(b) Design strength of the strong connection, φSn, shall be not less than Se;
All rights reserved
367 / 496
(c) Primary longitudinal reinforcement shall be made continuous across connections and shall be
developed outside both the strong connection and the plastic hinge region; and
(d) For column-to-column connections, φSn shall not be less than 1.4Se . At column-to-column
connections, φMn shall be not less than 0.4Mpr for the column within the story height, and
φVn of the connection shall be not less than Ve determined by 521.6.5.1.
FIGURE 521.8.3-1 Strong connection examples
All rights reserved
368 / 496
521.8.4
Special moment frames constructed using precast concrete and not satisfying the requirements
of 521.8.2 or 521.8.3 shall satisfy the requirements of ACI 374.1 and the requirements of (a) and
(b):
(a) Details and materials used in the test specimens shall be representative of those used in the
structure; and
(b) The design procedure used to proportion the test specimens shall define the mechanism by
which the frame resists gravity and earthquake effects, and shall establish acceptance values
for sustaining that mechanism.
521.9 SPECIAL STRUCTURAL WALLS AND COUPLING BEAMS
521.9.1 SCOPE
Requirements of 521.9 apply to special structural walls, cast-in-place or precast, and coupling
beams forming part of the seismic-force-resisting system. Special structural walls constructed
using precast concrete shall also comply with 521.10.
521.9.2 REINFORCEMENT
521.9.2.1
The distributed web reinforcement ratios, ρl and ρt, for structural walls shall not be less than
0.0025, except that if Vu does not exceed 0.083Acvλ√
, ρl and ρt shall be permitted to be
reduced to the values required in 518.3. Reinforcement spacing each way in structural walls
shall not exceed 450 mm. Reinforcement contributing to Vn shall be continuous and shall be
distributed across the shear plane.
521.9.2.2
At least two curtains of reinforcement shall be used in a wall if Vu exceeds 0.17Acvλ√
.
521.9.2.3
Reinforcement in structural walls shall be developed or spliced for fy in tension in
accordance with Section 516, except:
(a) The effective depth of the member referenced in 516.10.3 shall be permitted to be taken
as 0.8lw for walls.
(b) The requirements of 516.11, 516.12, and 516.13 need not be satisfied.
(c) At locations where yielding of longitudinal reinforcement is likely to occur as a result of
lateral
displacements, development lengths of longitudinal reinforcement shall be 1.25 times the
values calculated for fy in tension.
(d) Mechanical splices of reinforcement shall conform to 521.1.6 and welded splices of
reinforcement
shall conform to 521.1.7.
521.9.3 DESIGN FORCES
Vu shall be obtained from the lateral load analysis in accordance with the factored load
combinations.
521.9.4 SHEAR STRENGTH
521.9.4.1
Vn of structural walls shall not exceed
All rights reserved
369 / 496
Vn = Acv(αcλ√
+ ρtfy)
EQUATION 521.9.4.1-1
where the coefficient αc is 0.25 for hw /lw ≤ 1.5, is 0.17 for hw /lw ≥ 2.0, and varies linearly
between 0.25 and 0.17 for hw /lw between 1.5 and 2.0.
521.9.4.2
In 521.9.4.1, the value of ratio hw /lw used for determining Vn for segments of a wall shall be
the larger of the ratios for the entire wall and the segment of wall considered.
521.9.4.3
Walls shall have distributed shear reinforcement providing resistance in two orthogonal
directions in the plane of the wall. If hw /lw does not exceed 2.0, reinforcement ratio ρl shall
not be less than reinforcement ratio ρt .
521.9.4.4
For all wall piers sharing a common lateral force, Vn shall not be taken larger than 0.66Acv
√
, where Acv is the gross area of concrete bounded by web thickness and length of
section. For any one of the individual wall piers, Vn shall not be taken larger than 0.83Acw
√
, where Acw is the area of concrete section of the individual pier considered.
521.9.4.5
For horizontal wall segments and coupling beams, Vn shall not be taken larger than 0.83Acw
, where Acw is the area of concrete section of a horizontal wall segment or coupling
√
beam.
521.9.5 DESIGN FOR FLEXURE AND AXIAL LOADS
521.9.5.1
Structural walls and portions of such walls subject to combined flexural and axial loads shall
be designed in accordance with 514.2 and 514.3 except that 514.3.6 and the nonlinear strain
requirements of 514.2.2 shall not apply. Concrete and developed longitudinal reinforcement
within effective flange widths, boundary elements, and the wall web shall be considered
effective. The effects of openings shall be considered.
521.9.5.2
Unless a more detailed analysis is performed, effective flange widths of flanged sections
shall extend from the face of the web a distance equal to the smaller of one-half the
distance to an adjacent wall web and 25 percent of the total wall height.
521.9.6 BOUNDARY ELEMENTS OF SPECIAL STRUCTURAL WALLS
521.9.6.1
The need for special boundary elements at the edges of structural walls shall be evaluated in
accordance with 521.9.6.2 or 21.9.6.3. The requirements of 521.9.6.4 and 521.9.6.5 also
shall be satisfied.
All rights reserved
370 / 496
521.9.6.2
This section applies to walls or wall piers that are effectively continuous from the base of
structure to top of wall and designed to have a single critical section for flexure and axial
loads. Walls not satisfying these requirements shall be designed by 21.9.6.3.
(a) Compression zones shall be reinforced with special boundary elements where
c≥lw/600(δu/hw)
EQUATION 521.9.6.2-1
c in Equation 521.9.6.2-1 corresponds to the largest neutral axis depth calculated for the
factored axial force and nominal moment strength consistent with the design displacement
δu. Ratio δu /hw in Equation 521.9.6.2-1 shall not be taken less than 0.007;
(b) Where special boundary elements are required by 21.9.6.2(a), the special boundary
element reinforcement shall extend vertically from the critical section a distance not less
than the larger of lw or Mu /4Vu.
521.9.6.3
Structural walls not designed to the provisions of 521.9.6.2 shall have special boundary
elements at boundaries and edges around openings of structural walls where the maximum
extreme fiber compressive stress, corresponding to load combinations including earthquake
effects, E, exceeds 0.2f΄c. The special boundary element shall be permitted to be
discontinued where the calculated compressive stress is less than 0.15f΄c. Stresses shall be
calculated for the factored forces using a linearly elastic model and gross section properties.
For walls with flanges, an effective flange width as defined in 521.9.5.2 shall be used.
521.9.6.4
Where special boundary elements are required by 521.9.6.2 or 521.9.6.3, (a) through (e)
shall be satisfied:
(a) The boundary element shall extend horizontally from the extreme compression fiber a
distance not less than the larger of c – 0.1lw and c/2, where c is the largest neutral axis
depth calculated for the factored axial force and nominal moment strength consistent
with δu;
(b) In flanged sections, the boundary element shall include the effective flange width in
compression and shall extend at least 300 mm into the web;
(c) The boundary element transverse reinforcement shall satisfy the requirements of
521.6.4.2 through 521.6.4.4, except Equation 521.6.4.4-1 need not be satisfied and the
transverse reinforcement spacing limit of 521.6.4.3(a) shall be one-third of the least
dimension of the boundary element;
(d) The boundary element transverse reinforcement at the wall base shall extend into the
support at least ld, according to 521.9.2.3, of the largest longitudinal reinforcement in
the special boundary element unless the special boundary element terminates on a
footing or mat, where special boundary element transverse reinforcement shall extend
at least 300 mm into the footing or mat;
(e) Horizontal reinforcement in the wall web shall be anchored to develop fy within the
confined core of the boundary element.
521.9.6.5
Where special boundary elements are not required by 521.9.6.2 or 521.9.6.3, (a) and (b)
shall be satisfied:
(a) If the longitudinal reinforcement ratio at the wall boundary is greater than 2.8/fy,
boundary transverse reinforcement shall satisfy 521.6.4.2 and 521.9.6.4(a). The
All rights reserved
371 / 496
maximum longitudinal spacing of transverse reinforcement in the boundary shall not
exceed 200 mm;
(b) Except when Vu in the plane of the wall is less than 0.083Acvλ√
, horizontal
reinforcement terminating at the edges of structural walls without boundary elements
shall have a standard hook engaging the edge reinforcement or the edge reinforcement
shall be enclosed in U-stirrups having the same size and spacing as, and spliced to, the
horizontal reinforcement.
FIGURE 521.9.6.5-1 Longitudinal reinforcement ratios for typical wall boundary conditions.
All rights reserved
372 / 496
FIGURE 521.9.6.5-2 Coupling beams with diagonally oriented reinforcement. Wall boundary
reinforcement shown on one side only for clarity.
521.9.7 COUPLING BEAMS
521.9.7.1
Coupling beams with (ln/h) ≥ 4 shall satisfy the requirements of 521.5. The provisions of
521.5.1.3 and 521.5.1.4 need not be satisfied if it can be shown by analysis that the beam
has adequate lateral stability.
521.9.7.2
Coupling beams with (ln/h) < 2 and with Vu exceeding 0.33λ √
Acw shall be reinforced
with two intersecting groups of diagonally placed bars symmetrical about the midspan,
unless it can be shown that loss of stiffness and strength of the coupling beams will not
impair the vertical loadcarrying ability of the structure, the egress from the structure, or the
integrity of nonstructural components and their connections to the structure.
All rights reserved
373 / 496
521.9.7.3
Coupling beams not governed by 521.9.7.1 or 521.9.7.2 shall be permitted to be reinforced
either with two intersecting groups of diagonally placed bars symmetrical about the
midspan or according to 521.5.2 through 521.5.4.
521.9.7.4
Coupling beams reinforced with two intersecting groups of diagonally placed bars
symmetrical about the midspan shall satisfy (a), (b), and either (c) or (d). Requirements of
515.9 shall not apply.
(a) Vn shall be determined by
Vn = 2Avdfysinα ≤ 10 √
Acw
EQUATION 521.9.7.4-1
where α is the angle between the diagonal bars and the longitudinal axis of the coupling
beam.
(b) Each group of diagonal bars shall consist of a minimum of four bars provided in two or
more layers. The diagonal bars shall be embedded into the wall not less than 1.25 times
the development length for fy in tension.
(c) Each group of diagonal bars shall be enclosed by transverse reinforcement having out-toout dimensions not smaller than bw /2 in the direction parallel to bw and bw /5 along the
other sides, where bw is the web width of the coupling beam. The transverse
reinforcement shall satisfy 521.6.4.2 and 521.6.4.4, shall have spacing measured parallel
to the diagonal bars satisfying 521.6.4.3(c) and not exceeding six times the diameter of
the diagonal bars, and shall have spacing of crossties or legs of hoops measured
perpendicular to the diagonal bars not exceeding 350 mm. For the purpose of
computing Ag for use in Equation 514.9.3-1 and 521.6.4.4-2, the concrete cover as
required in 506.7 shall be assumed on all four sides of each group of diagonal bars. The
transverse reinforcement, or its alternatively configured transverse reinforcement
satisfying the spacing and volume ratio requirements of the transverse reinforcement
along the diagonals, shall continue through the intersection of the diagonal bars.
Additional longitudinal and transverse reinforcement shall be distributed around the
beam perimeter with total area in each direction not less than 0.002bws and spacing not
exceeding 300 mm.
(d) Transverse reinforcement shall be provided for the entire beam cross section satisfying
521.6.4.2, 521.6.4.4, and 521.6.4.7, with longitudinal spacing not exceeding the smaller
of 150 mm and six times the diameter of the diagonal bars, and with spacing of crossties
or legs of hoops both vertically and horizontally in the plane of the beam cross section
not exceeding 200 mm. Each crosstie and each hoop leg shall engage a longitudinal bar
of equal or larger diameter. It shall be permitted to configure hoops as specified in
521.5.3.6.
521.9.8 CONSTRUCTION JOINTS
All construction joints in structural walls shall conform to 505.4 and contact surfaces shall be
roughened as in 515.8.9.
521.9.9 DISCONTINUOUS WALLS
Columns supporting discontinuous structural walls shall be reinforced in accordance with
521.6.4.6.
521.9.10
Wall piers and wall segments.
All rights reserved
374 / 496
521.9.10.1
Wall piers not designed as a part of a special moment frame shall have transverse
reinforcement designed to satisfy the requirements in 521.9.10.2.
Exceptions:
1. Wall piers that satisfy 521.13.
2. Wall piers along a wall line within a story where other shear wall segments provide lateral
support to the wall piers and such segments have a total stiffness of at least six times the
sum of the stiffnesses of all the wall piers.
521.9.10.2 – Transverse reinforcement with seismic hooks at both ends shall be designed
to resist the shear forces determined from 521.6.5.1. Spacing of transverse reinforcement
shall not exceed 150mm. Transverse reinforcement shall be extended beyond the pier
clear height for at least 300mm.
521.9.10.3 – Wall segments with a horizontal length-to- thickness ratio less than 2.5 shall
be designed as columns.
521.10 SPECIAL STRUCTURAL WALLS CONSTRUCTED USING PRECAST CONCRETE
521.10.1 SCOPE
Requirements of 521.10 apply to special structural walls constructed using precast concrete
forming part of the seismic-force-resisting system.
521.10.2
Special structural walls constructed using precast concrete shall satisfy all the requirements of
521.9 for cast-in-place special structural walls in addition to Sections 521.4.2 through 521.4.4.
521.10.3
Special structural walls constructed using precast concrete and unbonded post-tensioning
tendons and not satisfying the requirements of 521.10.2 are permitted provided they satisfy the
requirements of ACI ITG-5.1.
521.11 STRUCTURAL DIAPHRAGMS AND TRUSSES
521.11.1 SCOPE
Floor and roof slabs acting as structural diaphragms to transmit forces induced by earthquake
ground motions in structures assigned to SDC D, E, or F shall be designed in accordance with this
section. This section also applies to collector elements and trusses forming part of the seismicforce-resisting system.
521.11.2 DESIGN FORCES
The earthquake design forces for structural diaphragms shall be obtained from the legally
adopted
general building code using the applicable provisions and load combinations.
521.11.3 SEISMIC LOAD PATH
521.11.3.1
All diaphragms and their connections shall be proportioned and detailed to provide for a
complete transfer of forces to collector elements and to the vertical elements of the seismicforce-resisting system.
All rights reserved
375 / 496
521.11.3.2
Elements of a structural diaphragm system that are subjected primarily to axial forces and
used to transfer diaphragm shear or flexural forces around openings or other discontinuities,
shall comply with the requirements for collectors in 521.11.7.5 and 521.11.7.6.
FIGURE 521.11.3.2-1R21.11.3.2—Example of diaphragm subject to the requirements of
521.11.3.2 and showing an element having confinement as required by 521.11.7.5.
521.11.4 CAST-IN-PLACE COMPOSITE-TOPPING SLAB DIAPHRAGMS
A composite-topping slab cast in place on a precast floor or roof shall be permitted to be used as
a structural diaphragm, provided the topping slab is reinforced and the surface of the previously
hardened concrete on which the topping slab is placed is clean, free of laitance, and
intentionally roughened.
521.11.5 CAST-IN-PLACE TOPPING SLAB DIAPHRAGMS
A cast-in-place noncomposite topping on a precast floor or roof shall be permitted to serve as a
structural diaphragm, provided the cast-in-place topping acting alone is proportioned and
detailed to resist the design earthquake forces.
521.11.6 MINIMUM THICKNESS OF DIAPHRAGMS
Concrete slabs and composite topping slabs serving as structural diaphragms used to transmit
earthquake forces shall not be less than 50 mm thick. Topping slabs placed over precast floor or
roof elements, acting as structural diaphragms and not relying on composite action with the
precast elements to resist the design earthquake forces, shall have thickness not less than 65
mm.
521.11.7 REINFORCEMENT
521.11.7.1
The minimum reinforcement ratio for structural diaphragms shall be in conformance with
506.12. Except for post-tensioned slabs, reinforcement spacing each way in floor or roof
systems shall not exceed 450 mm. Where welded wire reinforcement is used as the
distributed reinforcement to resist shear in topping slabs placed over precast floor and roof
elements, the wires parallel to the span of the precast elements shall be spaced not less
All rights reserved
376 / 496
than 250 mm on center. Reinforcement provided for shear strength shall be continuous and
shall be distributed uniformly across the shear plane.
521.11.7.2
Bonded tendons used as reinforcement to resist collector forces or diaphragm shear or
flexural tension shall be proportioned such that the stress due to design earthquake forces
does not exceed 420 MPa. Precompression from unbonded tendons shall be permitted to
resist diaphragm design forces if a seismic load path is provided.
521.11.7.3
All reinforcement used to resist collector forces, diaphragm shear, or flexural tension shall
be developed or spliced for fy in tension.
521.11.7.4
Type 2 splices are required where mechanical splices are used to transfer forces
between the diaphragm and the vertical elements of the seismic-force-resisting system.
521.11.7.5
Collector elements with compressive stresses exceeding 0.2f΄cat any section shall have
transverse reinforcement satisfying 521.9.6.4(c) over the length of the element. The
specified transverse reinforcement is permitted to be discontinued at a section where the
calculated compressive stress is less than 0.15f΄c . Where design forces have been amplified
to account for the overstrength of the vertical elements of the seismic-force-resisting
system, the limit of 0.2f΄c shall be increased to 0.5f΄c, and the limit of 0.15f΄c shall be
increased to 0.4 f΄c .
521.11.7.6
Longitudinal reinforcement for collector elements at splices and anchorage zones shall have
either:
(a) A minimum center-to-center spacing of three longitudinal bar diameters, but not less
than 40 mm, and a minimum concrete clear cover of two and one-half longitudinal bar
diameters, but not less than 50 mm; or
(b) Transverse reinforcement as required by 515.5.3, except as required in 521.11.7.5.
521.11.8 FLEXURAL STRENGTH
Diaphragms and portions of diaphragms shall be designed for flexure in accordance with 514.2
and 514.3 except that the nonlinear distribution of strain requirements of 514.2.2 for deep
beams need not apply. The effects of openings shall be considered.
521.11.9 SHEAR STRENGTH
521.11.9.1
Vn of structural diaphragms shall not exceed
Vn = Acv(0.17λ √
+ ρt fy)
EQUATION 521.11.9.1-1
For cast-in-place topping slab diaphragms on precast floor or roof members, Acv shall be
computed using the thickness of topping slab only for noncomposite topping slab
diaphragms and the combined thickness of cast-in-place and precast elements for composite
topping slab diaphragms. For composite topping slab diaphragms, the value of f΄c used to
determine Vn shall not exceed the smaller of f΄c for the precast members and f΄c for the
topping slab.
All rights reserved
377 / 496
521.11.9.2
Vn of structural diaphragms shall not exceed 0.66Acv √
.
521.11.9.3
Above joints between precast elements in noncomposite and composite cast-in-place
topping slab diaphragms, Vn shall not exceed
Vn = Avffyμ
EQUATION 521.11.9.3-1
where Avf is total area of shear friction reinforcement within topping slab, including both
distributed and boundary reinforcement, that is oriented perpendicular to joints in the
precast system and coefficient of friction, μ, is 1.0λ, where λ is given in 515.8.4.3. At least
onehalf of Avf shall be uniformly distributed along the length of the potential shear plane.
Area of distributed reinforcement in topping slab shall satisfy 506.12.2.1 in each direction.
521.11.9.4
Above joints between precast elements in noncomposite and composite cast-in-place
topping slab diaphragms, Vn shall not exceed the limits in 515.8.5 where Ac is computed
using the thickness of the topping slab only.
521.11.10 CONSTRUCTION JOINTS
All construction joints in diaphragms shall conform to 505.4 and contact surfaces shall be
roughened as in 515.8.9.
521.11.11 STRUCTURAL TRUSSES
521.11.11.1
Structural truss elements with compressive stresses exceeding 0.2f΄c at any section shall
have transverse reinforcement, as given in 521.6.4.2 through 521.6.4.4 and 521.6.4.7, over
the length of the element.
521.11.11.2
All continuous reinforcement in structural truss elements shall be developed or spliced for fy
in tension.
521.12 FOUNDATIONS
521.12.1 SCOPE
521.12.1.1
Foundations resisting earthquake-induced forces or transferring earthquake-induced forces
between a structure and ground shall comply with the requirements of Section 521.12, unless
modified by Section 512 of this code.
521.12.1.2
The provisions in this section for piles, drilled piers, caissons, and slabs-on-ground shall
supplement other applicable design and construction criteria.
All rights reserved
378 / 496
521.12.2 FOOTINGS, FOUNDATION MATS, AND PILE CAPS
521.12.2.1
Longitudinal reinforcement of columns and structural walls resisting forces induced by
earthquake effects shall extend into the footing, mat, or pile cap, and shall be fully
developed for tension at the interface.
521.12.2.2
Columns designed assuming fixed-end conditions at the foundation shall comply with
521.12.2.1 and, if hooks are required, longitudinal reinforcement resisting flexure shall have
90-degree hooks near the bottom of the foundation with the free end of the bars oriented
toward the center of the column.
521.12.2.3
Columns or boundary elements of special structural walls that have an edge within onehalf
the footing depth from an edge of the footing shall have transverse reinforcement in
accordance with 521.6.4.2 through 521.6.4.4 provided below the top of the footing. This
reinforcement shall extend into the footing, mat, or pile cap and be developed for fy in
tension.
521.12.2.4
Where earthquake effects create uplift forces in boundary elements of special structural
walls or columns, flexural reinforcement shall be provided in the top of the footing, mat, or
pile cap to resist actions resulting from the design load combinations, and shall not be less
than required by 514.5.
521.12.2.5
See 507.10 for use of structural plain concrete in footings and basement walls.
521.12.3 GRADE BEAMS AND SLABS-ON-GROUND
521.12.3.1
Grade beams designed to act as horizontal ties between pile caps or footings shall have
continuous longitudinal reinforcement that shall be developed within or beyond the
supported column or anchored within the pile cap or footing at all discontinuities.
521.12.3.2
Grade beams designed to act as horizontal ties between pile caps or footings shall be
proportioned such that the smallest cross-sectional dimension shall be equal to or greater
than the clear spacing between connected columns divided by 20, but need not be greater
than 450 mm. Closed ties shall be provided at a spacing not to exceed the lesser of one-half
the smallest orthogonal cross-sectional dimension and 300 mm.
521.12.3.3
Grade beams and beams that are part of a mat foundation subjected to flexure from
columns that are part of the seismic-force-resisting system shall conform to 521.5.
521.12.3.4
Slabs-on-ground that resist seismic forces from walls or columns that are part of the seismicforce-resisting system shall be designed as structural diaphragms in accordance with 521.11.
The design drawings shall clearly state that the slab-onground is a structural diaphragm and
part of the seismic-force-resisting system.
All rights reserved
379 / 496
521.12.4 PILES, PIERS, AND CAISSONS
521.12.4.1
Provisions of 521.12.4 shall apply to concrete piles, piers, and caissons supporting structures
designed for earthquake resistance.
521.12.4.2
Piles, piers, or caissons resisting tension loads shall have continuous longitudinal
reinforcement over the length resisting design tension forces. The longitudinal
reinforcement shall be detailed to transfer tension forces within the pile cap to supported
structural members.
521.12.4.3
Where tension forces induced by earthquake effects are transferred between pile cap or
mat foundation and precast pile by reinforcing bars grouted or post-installed in the top of
the pile, the grouting system shall have been demonstrated by test to develop at least
1.25fy of the bar.
521.12.4.4
Piles, piers, or caissons shall have transverse reinforcement in accordance with 521.6.4.2
through 521.6.4.4 at locations (a) and (b):
(a) At the top of the member for at least 5 times the member cross-sectional dimension, but
not less than 1.8 m below the bottom of the pile cap;
(b) For the portion of piles in soil that is not capable of providing lateral support, or in air and
water, along the entire unsupported length plus the length required in 521.12.4.4(a).
521.12.4.5
For precast concrete driven piles, the length of transverse reinforcement provided shall be
sufficient to account for potential variations in the elevation in pile tips.
521.12.4.6
Concrete piles, piers, or caissons in foundations supporting one- and two-story stud bearing
wall construction are exempt from the transverse reinforcement requirements of 521.12.4.4
and 521.12.4.5.
521.12.4.7
Pile caps incorporating batter piles shall be designed to resist the full compressive strength
of the batter piles acting as short columns. The slenderness effects of batter piles shall be
considered for the portion of the piles in soil that is not capable of providing lateral support,
or in air or water.
521.13 MEMBERS NOT DESIGNATED AS PART OF THE SEISMIC-FORCE-RESISTING SYSTEMS
521.13.1 SCOPE
Requirements of 521.13 apply to frame members not designated as part of the seismic-forceresisting
system in structures assigned to SDC D, E, and F.
521.13.2
Frame members assumed not to contribute to lateral resistance, except two-way slabs without
beams, shall be detailed according to 521.13.3 or 521.13.4 depending on the magnitude of
moments induced in those members when subjected to the design displacement δu. If effects of
δu are not explicitly checked, it shall be permitted to apply the requirements of 521.13.4. For
All rights reserved
380 / 496
two-way slabs without beams, slab-column connections shall meet the requirements of
521.13.6.
521.13.3
Where the induced moments and shears under design displacements, δu, combined with the
factored gravity moments and shears do not exceed the design moment and shear strength of
the frame member, the conditions of 521.13.3.1, 52113.3.2, and 521.13.3.3 shall be satisfied.
The gravity load combinations of (1.2D + 1.0L + 0.2S) or 0.9D, whichever is critical, shall be used.
The load factor on the live load, L, shall be permitted to be reduced to 0.5 except for garages,
areas occupied as places of public assembly, and all areas where L is greater than 4.8 kN/m2.
521.13.3.1
Members with factored gravity axial forces not exceeding Agf΄c/10 shall satisfy 521.5.2.1.
Stirrups shall be spaced not more than d/2 throughout the length of the member.
521.13.3.2
Members with factored gravity axial forces exceeding Agf΄c/10 shall satisfy 521.6.3.1,
521.6.4.2, and 521.6.5. The maximum longitudinal spacing of ties shall be so for the full
member length.
Spacing so shall not exceed the smaller of six diameters of the smallest longitudinal bar
enclosed and 150 mm.
521.13.3.3
Members with factored gravity axial forces exceeding 0.35Po shall satisfy 521.13.3.2 and
521.6.4.7. The amount of transverse reinforcement provided shall be one-half of that
required by 521.6.4.4 but shall not be spaced greater than so for the full member length.
521.13.4
If the induced moment or shear under design displacements, δu, exceeds φMn or φVn of the
frame member, or if induced moments are not calculated, the conditions of 521.13.4.1,
521.13.4.2, and 521.13.4.3 shall be satisfied.
521.13.4.1
Materials shall satisfy 521.1.4.2, 521.1.4.3, 521.1.5.2, 521.1.5.4, and 521.1.5.5. Mechanical
splices shall satisfy 521.1.6 and welded splices shall satisfy 521.1.7.1.
521.13.4.2
Members with factored gravity axial forces not exceeding Agf΄c/10 shall satisfy 521.5.2.1 and
521.5.4. Stirrups shall be spaced at not more than d/2 throughout the length of the
member.
521.13.4.3
Members with factored gravity axial forces exceeding Agf΄c /10 shall satisfy 521.6.3, 21.6.4,
521.6.5, and 521.7.3.1.
521.13.5
Precast concrete frame members assumed not to contribute to lateral resistance, including their
connections, shall satisfy (a), (b), and (c), in addition to 521.13.2 through 521.13.4:
(a) Ties specified in 521.13.3.2 shall be provided over the entire column height, including the
depth of the beams;
(b) Structural integrity reinforcement, as specified in 520.5, shall be provided; and
All rights reserved
381 / 496
(c) Bearing length at support of a beam shall be at least 50 mm longer than determined from
calculations using bearing strength values from 514.14.
521.13.6
For slab-column connections of two-way slabs without beams, slab shear reinforcement
satisfying the requirements of 515.13.3 and 515.13.5 and providing Vs not less than 0.29 √
bod shall extend at least four times the slab thickness from the face of the support, unless either
(a) or (b) is satisfied:
(a) The requirements of 515.13.7 using the design shear Vug and the induced moment
transferred between the slab and column under the design displacement;
(b) The design story drift ratio does not exceed the larger of 0.005 and [0.035 – 0.05(Vug /φVc)].
Design story drift ratio shall be taken as the larger of the design story drift ratios of the adjacent
stories above and below the slab-column connection. Vc is defined in 515.13.2. Vug is the
factored shear force on the slab critical section for two-way action, calculated for the load
combination 1.2D + 1.0L + 0.2S. The load factor on the live load, L, shall be permitted to be
reduced to 0.5 except for garages, areas occupied as places of public assembly, and all areas
where L is greater than 4.8 kN/m2.
FIGURE 521.13.6 Illustration of the criterion of 521.13.6(b).
SECTION 522 DIRECT DESIGN METHOD
522.1 LIMITATIONS
Design of slab systems within the limitations of 522.1.1 through 522.1.8 by the direct design method
shall be permitted.
522.1.1
There shall be a minimum of three continuous spans in each direction.
522.1.2
Panels shall be rectangular, with a ratio of longer to shorter span center-to-center of supports
within a panel not greater than 2.
522.1.3
Successive span lengths center-tocenter of supports in each direction shall not differ by more
than one-third the longer span.
All rights reserved
382 / 496
522.1.4
Offset of columns by a maximum of 10 percent of the span (in direction of offset) from either
axis between centerlines of successive columns shall be permitted.
522.1.5
All loads shall be due to gravity only and uniformly distributed over an entire panel. The
unfactored live load shall not exceed two times the unfactored dead load.
522.1.6
For a panel with beams between supports on all sides, Equation 522.1.6-1 shall be satisfied for
beams in the two perpendicular directions
EQUATION 522.1.6-1
where αf1 and αf 2 are calculated in accordance with Equation 522.1.6-2.
EQUATION 522.1.6-2
522.1.7
Moment redistribution as permitted by 512.4 shall not be applied for slab systems designed by
the direct design method. See 522.7.
522.1.8
Variations from the limitations of 522.1 shall be permitted if demonstrated by analysis that
requirements of 517.5.1 are satisfied.
522.2 TOTAL FACTORED STATIC MOMENT FOR A SPAN
522.2.1
Total factored static moment, Mo , for a span shall be determined in a strip bounded laterally by
centerline of panel on each side of centerline of supports.
522.2.2
Absolute sum of positive and average negative factored moments in each direction shall not be
less than
EQUATION 522.2.2-1
where ln is length of clear span in direction that moments are being determined.
522.2.3
Where the transverse span of panels on either side of the centerline of supports varies, l2 in
Equation 522.2.2-1 shall be taken as the average of adjacent transverse spans.
522.2.4
When the span adjacent and parallel to an edge is being considered, the distance from edge to
panel centerline shall be substituted for l2 in Equation 522.2.2-1.
All rights reserved
383 / 496
522.2.5
Clear span ln shall extend from face to face of columns, capitals, brackets, or walls. Value of ln
used in Equation 522.2.2-1 shall not be less than 0.65l1. Circular or regular polygon-shaped
supports shall be treated as square supports with the same area.
522.3 NEGATIVE AND POSITIVE FACTORED MOMENTS
522.3.1
Negative factored moments shall be located at face of rectangular supports. Circular or regular
polygon-shaped supports shall be treated as square supports with the same area.
522.3.2
In an interior span, total static moment, Mo , shall be distributed as follows:
Negative factored moment..................................0.65
Positive factored moment ...................................0.35
522.3.3
In an end span, total factored static moment, Mo , shall be distributed as follows:
Interior
negative
factored
moment
Positive
factored
moment
Exterior
negative
factored
moment
(1)
Exterior edge
unrestrained
(2)
Slab with
beams
between all
supports
(5)
Exterior
edge fully
restrained
0.70
(3)
(4)
Slab without beams
between interior
supports
Without
With edge
edge
beam
beam
0.70
0.70
0.75
0.63
0.57
0.52
0.50
0.35
0
0.16
0.26
0.30
0.65
0.65
522.3.4
Negative moment sections shall be designed to resist the larger of the two interior negative
factored moments determined for spans framing into a common support unless an analysis is
made to distribute the unbalanced moment in accordance with stiffnesses of adjoining
elements.
522.3.5
Edge beams or edges of slab shall be proportioned to resist in torsion their share of exterior
negative factored moments.
522.3.6
The gravity load moment to be transferred between slab and edge column in accordance with
517.5.3.1 shall be 0.3Mo.
All rights reserved
384 / 496
522.4 FACTORED MONETS IN COLUMN STRIPS
522.4.1
Column strips shall be proportioned to resist the following portions in percent of interior
negative factored moments:
l2/l1
(αf1l2/l1) = 0
(αf1l2/l1) ≥ 1.0
0.5
1.0
2.0
75
90
75
75
75
45
Linear interpolations shall be made between values shown.
522.4.2
Column strips shall be proportioned to resist the following portions in percent of exterior
negative factored moments:
l2/l1
(αf1l2/l1) = 0
(αf1l2/l1) ≥ 1.0
0.5
100
075
100
90
βt = 0
βt ≥ 2.5
βt = 0
βt ≥ 2.5
1.0
100
75
100
75
2.0
100
75
100
45
Linear interpolations shall be made between values shown, where βt is calculated in Equation 522.4.61 and C is calculated in Equation 522.4.6-2.
EQUATION 522.4.6-1
∑(
)
EQUATION 522.4.6-2
The constant C for T- or L-sections shall be permitted to be evaluated by dividing the section into
separate rectangular parts, as defined in 517.2.4, and summing the values of C for each part.
522.4.3
Where supports consist of columns or walls extending for a distance equal to or greater than
(0.75)l2 used to compute Mo, negative moments shall be considered to be uniformly distributed
across l2.
522.4.4
Column strips shall be proportioned to resist the following portions in percent of positive
factored moments:
l2/l1
(αf1l2/l1) = 0
(αf1l2/l1) ≥ 1.0
0.5
60
90
1.0
60
75
2.0
60
45
Linear interpolations shall be made between values shown.
522.4.5
For slabs with beams between supports, the slab portion of column strips shall be proportioned
to resist that portion of column strip moments not resisted by beams.
All rights reserved
385 / 496
522.5 FACTORED MOMENTS INBEAMS
522.5.1
Beams between supports shall be proportioned to resist 85 percent of column strip moments if
αf1l2/l1 is equal to or greater than 1.0.
522.5.2
For values of αf1l2/l1 between 1.0 and zero, proportion of column strip moments resisted by
beams shall be obtained by linear interpolation between 85 and zero percent.
522.5.3
In addition to moments calculated for uniform loads according to 522.2.2, 522.5.1, and 522.5.2,
beams shall be proportioned to resist all moments caused by concentrated or linear loads
applied directly to beams, including weight of projecting beam stem above or below the slab.
522.6 FACTORED MOMENTS IN MIDDLE STRIPS
522.6.1
That portion of negative and positive factored moments not resisted by column strips shall be
proportionately assigned to corresponding half middle strips.
522.6.2
Each middle strip shall be proportioned to resist the sum of the moments assigned to its two half
middle strips.
522.6.3
A middle strip adjacent to and parallel with a wall-supported edge shall be proportioned to resist
twice the moment assigned to the half middle strip corresponding to the first row of interior
supports.
522.7 MODIFICATION OF FACTORED MOMENTS
Modification of negative and positive factored moments by 10 percent shall be permitted provided the
total static moment for a panel, Mo , in the direction considered is not less than that required by
Equation 522.2.2-1.
522.8 FACTORED SHEAR IN SLABF SYSTEMS WITH BEAMS
522.8.1
Beams with αf1l2/l1 equal to or greater than 1.0 shall be proportioned to resist shear caused by
factored loads on tributary areas which are bounded by 45-degree lines drawn from the corners
of the panels and the centerlines of the adjacent panels parallel to the long sides.
522.8.2
In proportioning beams with αf1l2/l1 less than 1.0 to resist shear, linear interpolation, assuming
beams carry no load at αf1 = 0, shall be permitted.
522.8.3
In addition to shears calculated according to 522.8.1 and 522.8.2, beams shall be proportioned
to resist shears caused by factored loads applied directly on beams.
All rights reserved
386 / 496
522.8.4
Computation of slab shear strength on the assumption that load is distributed to supporting
beams in accordance with 522.8.1 or 522.8.2 shall be permitted. Resistance to total shear
occurring on a panel shall be provided.
522.8.5
Shear strength shall satisfy the requirements of Section 515.
522.9 FACTORED MOMENTS IN COLUMNS AND WALLS
522.9.1
Columns and walls built integrally with a slab system shall resist moments caused by factored
loads on the slab system.
522.9.2
At an interior support, supporting elements above and below the slab shall resist the factored
moment specified by Equation 522.9.2-1 in direct proportion to their stiffnesses unless a general
analysis is made.
(
)
(
)
EQUATION 522.9.2-1
where qDu′ , l2′, and ln′ refer to shorter span.
SECTION 523 EQUIVALENT FRAME METHOD
523.1
Design of slab systems by the equivalent frame method shall be based on assumptions given in 523.7.2
through 523.7.6, and all sections of slabs and supporting members shall be proportioned for moments
and shears thus obtained.
523.1.1
Where metal column capitals are used, it shall be permitted to take account of their
contributions to stiffness and resistance to moment and to shear.
523.1.2
It shall be permitted to neglect the change in length of columns and slabs due to direct stress,
and deflections due to shear.
523.2 EQUIVALENT FRAME
523.2.1
The structure shall be considered to be made up of equivalent frames on column lines taken
longitudinally and transversely through the building.
523.2.2
Each frame shall consist of a row of columns or supports and slab-beam strips, bounded laterally
by the centerline of panel on each side of the centerline of columns or supports.
523.2.3
Columns or supports shall be assumed to be attached to slab-beam strips by torsional
members (see 523.7.5) transverse to the direction of the span for which moments are being
determined and extending to bounding lateral panel centerlines on each side of a column.
All rights reserved
387 / 496
523.2.4
Frames adjacent and parallel to an edge shall be bounded by that edge and the centerline of
adjacent panel.
523.2.5
Analysis of each equivalent frame in its entirety shall be permitted. Alternatively, for gravity
loading, a separate analysis of each floor or roof with far ends of columns considered fixed shall
be permitted.
523.2.6
Where slab-beams are analyzed separately, determination of moment at a given support
assuming that the slab-beam is fixed at any support two panels distant therefrom, shall be
permitted, provided the slab continues beyond that point.
523.3 SLAB-BEAMS
523.3.1
Determination of the moment of inertia of slab-beams at any cross section outside of joints or
column capitals using the gross area of concrete shall be permitted.
523.3.2
Variation in moment of inertia along axis of slab-beams shall be taken into account.
523.3.3
Moment of inertia of slab-beams from center of column to face of column, bracket, or capital
shall be assumed equal to the moment of inertia of the slab-beam at face of column, bracket, or
capital divided by the quantity (1 – c2/l2)2, where c2 and l2 are measured transverse to the
direction of the span for which moments are being determined.
523.4 COLUMNS
523.4.1
Determination of the moment of inertia of columns at any cross section outside of joints or
column capitals using the gross area of concrete shall be permitted.
523.4.2
Variation in moment of inertia along axis of columns shall be taken into account.
523.4.3
Moment of inertia of columns from top to bottom of the slab-beam at a joint shall be assumed
to be infinite.
523.5 TORSIONAL MEMBERS
523.5.1
Torsional members (see 523.2.3) shall be assumed to have a constant cross section
throughout their length consisting of the largest of (a), (b), and (c):
(a) A portion of slab having a width equal to that of the column, bracket, or capital in the
direction of the span for which moments are being determined;
(b) For monolithic or fully composite construction, the portion of slab specified in (a) plus that
part of the transverse beam above and below the slab;
(c) The transverse beam as defined in 517.2.4.
All rights reserved
388 / 496
523.5.2
Where beams frame into columns in the direction of the span for which moments are being
determined, the torsional stiffness shall be multiplied by the ratio of the moment of inertia of
the slab with such a beam to the moment of inertia of the slab without such a beam.
523.6 ARRANGEMENT OF LIVE LOAD
523.6.1
When the loading pattern is known, the equivalent frame shall be analyzed for that load.
523.6.2
When the unfactored live load is variable but does not exceed three-quarters of the unfactored
dead load, or the nature of live load is such that all panels will be loaded simultaneously, it shall
be permitted to assume that maximum factored moments occur at all sections with full factored
live load on entire slab system.
523.6.3
For loading conditions other than those defined in 523.6.2, it shall be permitted to assume that
maximum positive factored moment near midspan of a panel occurs with three-quarters of the
full factored live load on the panel and on alternate panels; and it shall be permitted to assume
that maximum negative factored moment in the slab at a support occurs with three-quarters of
the full factored live load on adjacent panels only.
523.6.4
Factored moments shall be taken not less than those occurring with full factored live load on all
panels.
523.7 FACTORED MOMENTS
523.7.1
At interior supports, the critical section for negative factored moment (in both column and
middle strips) shall be taken at face of rectilinear supports, but not farther away than 0.175l1
from the center of a column.
523.7.2
At exterior supports with brackets or capitals, the critical section for negative factored moment
in the span perpendicular to an edge shall be taken at a distance from face of supporting
element not greater than one-half the projection of bracket or capital beyond face of supporting
element.
523.7.3
Circular or regular polygon-shaped supports shall be treated as square supports with the same
area for location of critical section for negative design moment.
523.7.4
Where slab systems within limitations of 522.1 are analyzed by the equivalent frame method, it
shall be permitted to reduce the resulting computed moments in such proportion that the
absolute sum of the positive and average negative moments used in design need not exceed the
value obtained from Equation 522.2.2-1.
All rights reserved
389 / 496
523.7.5
Distribution of moments at critical sections across the slab-beam strip of each frame to column
strips, beams, and middle strips as provided in 522.4, 13.6.5, and 522.6 shall be permitted if the
requirement of 522.1.6 is satisfied.
SECTION 524 COMPOSITE CONCRETE FLEXURAL MEMBERS
524.1 SCOPE
524.1.1
Provisions of Section 524 shall apply for design of composite concrete flexural members defined
as precast concrete, cast-in-place concrete elements, or both, constructed in separate
placements but so interconnected that all elements respond to loads as a unit.
524.1.2
All provisions of the Code shall apply to composite concrete flexural members, except as
specifically modified in Section 524.
524.2 GENERAL
524.2.1
The use of an entire composite member or portions thereof for resisting shear and moment shall
be permitted.
524.2.2
Individual elements shall be investigated for all critical stages of loading.
524.2.3
If the specified strength, unit weight, or other properties of the various elements are different,
properties of the individual elements or the most critical values shall be used in design.
524.2.4
In strength computations of composite members, no distinction shall be made between shored
and unshored members.
524.2.5
All elements shall be designed to support all loads introduced prior to full development of design
strength of composite members.
524.2.6
Reinforcement shall be provided as required to minimize cracking and to prevent separation of
individual elements of composite members.
524.2.7
Composite members shall meet requirements for control of deflections in accordance with
513.5.5.
524.3 SHORING
When used, shoring shall not be removed until supported elements have developed design properties
required to support all loads and limit deflections and cracking at time of shoring removal.
All rights reserved
390 / 496
524.4 VERTICAL SHEAR STRENGTH
524.4.1
Where an entire composite member is assumed to resist vertical shear, design shall be in
accordance with requirements of Section 515 as for a monolithically cast member of the same
crosssectional shape.
524.4.2
Shear reinforcement shall be fully anchored into interconnected elements in accordance with
516.13.
524.4.3
Extended and anchored shear reinforcement shall be permitted to be included as ties for
horizontal shear.
524.5 HORIZONTAL SHEAR STRENGTH
524.5.1
In a composite member, full transfer of horizontal shear forces shall be ensured at contact
surfaces of interconnected elements.
524.5.2
For the provisions of 17.5, d shall be taken as the distance from extreme compression fiber for
entire composite section to centroid of prestressed and nonprestressed longitudinal tension
reinforcement, if any, but need not be taken less than 0.80h for prestressed concrete members.
524.5.3
Unless calculated in accordance with 524.5.4, design of cross sections subject to horizontal shear
shall be based on
Vu ≤ φVnh
EQUATION 524.5.3-1
where Vnh is nominal horizontal shear strength in accordance with 524.5.3.1 through 524.5.3.4.
524.5.3.1
Where contact surfaces are clean, free of laitance, and intentionally roughened, Vnh shall
not be taken greater than 0.55bvd.
524.5.3.2
Where minimum ties are provided in accordance with 524.6, and contact surfaces are clean
and free of laitance, but not intentionally roughened, Vnh shall not be taken greater than
0.55bvd.
524.5.3.3
Where ties are provided in accordance with 524.6, and contact surfaces are clean, free of
laitance, and intentionally roughened to a full amplitude of approximately 6 mm, Vnh shall
be taken equal to (1.8 + 0.6ρvfy)λbvd, but not greater than 3.5bvd. Values for λ in 515.8.4.3
shall apply and ρv is Av /(bvs).
All rights reserved
391 / 496
524.5.3.4
Where Vu at section considered exceeds φ (3.5bvd), design for horizontal shear shall be in
accordance with 515.8.4.
524.5.4
As an alternative to 524.5.3, horizontal shear shall be permitted to be determined by computing
the actual change in compressive or tensile force in any segment, and provisions shall be made
to transfer that force as horizontal shear to the supporting element. The factored horizontal
shear force Vu shall not exceed horizontal shear strength φVnh as given in 524.5.3.1 through
524.5.3.4, where area of contact surface shall be substituted for bvd.
524.5.4.1
Where ties provided to resist horizontal shear are designed to satisfy 524.5.4, the tie area to
tie spacing ratio along the member shall approximately reflect the distribution of shear
forces in the member.
524.5.5
Where tension exists across any contact surface between interconnected elements, shear
transfer by contact shall be permitted only when minimum ties are provided in accordance with
524.6.
524.6 TIES FOR HORIZONTAL SHEAR
524.6.1
Where ties are provided to transfer horizontal shear, tie area shall not be less than that
required by 515.5.3, and tie spacing shall not exceed four times the least dimension of
supported element, nor exceed 600 mm.
524.6.2
Ties for horizontal shear shall consist of single bars or wire, multiple leg stirrups, or vertical
legs of welded wire reinforcement.
524.6.3
All ties shall be fully anchored into interconnected elements in accordance with 516.13.
All rights reserved
392 / 496
CHAPTER 6
STEEL
SECTION 601 GENERAL
601.1 SCOPE
The provisions of this chapter govern the quality, design, fabrication and erection of steel used
structurally in buildings or structures.
SECTION 602 IDENTIFICATION AND PROTECTION OF STEEL FOR STRUCTURAL PURPOSES
602.1 IDENTIFICATION
Identification of structural steel members shall comply with the requirements contained in AISC 360.
Identification of cold-formed steel members shall comply with the requirements contained in AISI S100.
Identification of cold-formed steel light-frame construction shall also comply with the requirements
contained in AISI S200. Other steel furnished for structural load-carrying purposes shall be properly
identified for conformity to the ordered grade in accordance with the specified ASTM standard or
other specification and the provisions of this chapter. Steel that is not readily identifiable as to grade
from marking and test records shall be tested to determine conformity to such standards.
602.2 PROTECTION
Painting of structural steel members shall comply with the requirements contained in AISC 360. Painting
of open-web steel joists and joist girders shall comply with the requirements of SJI CJ-1.0, SJI JG-1.1, SJI
K-1.1 and SJI LH/DLH-1.1. Individual structural members and assembled panels of cold-formed steel
construction shall be protected against corrosion in accordance with the requirements contained in
AISI S100. Protection of cold-formed steel light-frame construction shall also comply with the
requirements contained in AISI S200.
SECTION 603 CONNECTIONS
603.1 WELDING
The details of design, workmanship and technique for welding, inspection of welding and qualification
of welding operators shall conform to the requirements of the specifications listed in Sections 604,
605, 606, and 607. Special inspection of welding shall be provided where required by Section 903.
603.2 BOLTING
The design, installation and inspection of bolts shall be in accordance with the requirements of the
specifications listed in Sections 604 and 605. Special inspection of the installation of high-strength bolts
shall be provided where required by Section 903.
603.2.1 ANCHOR RODS
Anchor rods shall be set accurately to the pattern and dimensions called for on the plans. The
protrusion of the threaded ends through the connected material shall be sufficient to fully engage
the threads of the nuts, but shall not be greater than the length of the threads on the bolts.
SECTION 604 STRUCTURAL STEEL
604.1 GENERAL
The design, fabrication and erection of structural steel for buildings and structures shall be in
accordance with AISC 360. Where required, the seismic design of steel structures shall be in
accordance with the additional provisions of Section 604.2.
All rights reserved
393 / 496
604.2 SEISMIC REQUIREMENTS FOR STEEL STRUCTURES
The design of structural steel structures to resist seismic forces shall be in accordance with the
provisions of Section 604.2.1 or 604.2.2 for the appropriate seismic design category.
604.2.1 SEISMIC DESIGN CATEGORY A, B OR C
Structural steel structures assigned to Seismic Design Category A, B or C shall be of any construction
permitted in Section 604. An R factor as set forth in Section 311.6.2.1 for the appropriate steel
system is permitted where the structure is designed and detailed in accordance with the
provisions of AISC 341, Part I. Systems not detailed in accordance with the above shall use the R
factor in ASCE Section 311.6.2.1 designated for “structural steel systems not specifically detailed
for seismic resistance.”
604.2.2 SIESMIC DESIGN CATEGORY D, E OR F
Structural steel structures assigned to Seismic Design Category D, E or F shall be designed and
detailed in accordance with AISC 341, Part I.
604.3 SEISMIC REQUIREMENTS FOR COMPOSITE CONSTRUCTION
The design, construction and quality of composite steel and concrete components that resist
seismic forces shall conform to the requirements of the AISC 360 and ACI 318. An R factor as set
forth in Section 311.6.2.1 for the appropriate composite steel and concrete system is permitted
where the structure is designed and detailed in accordance with the provisions of AISC 341, Part
II. In Seismic Design Category B or above, the design of such systems shall conform to the
requirements of AISC 341, Part II.
604.3.1 SEISMIC DESIGN CATEGORIES D, E AND F
Composite structures are permitted in Seismic Design Categories D , E and F, subject to the
limitations in Section 311.6.2.1, where substantiating evidence is provided to demonstrate that
the proposed system will perform as intended by AISC 341, Part II. The substantiating
evidence shall be subject to building official approval. Where composite elements or
connections are required to sustain inelastic deformations, the substantiating evidence shall
be based on cyclic testing.
SECTION 605 STEEL JOISTS
605.1 GENERAL
The design, manufacture and use of open web steel joists and joist girders shall be in accordance with
one of the following Steel Joist Institute (SJI) specifications:
1. SJI CJ-1.0
2. SJI K-1.1
3. SJI LH/DLH-1.1
4. SJI JG-1.1
Where required, the seismic design of buildings shall be in accordance with the additional provisions of
Section 604.2 or 607.5.
605.2 DESIGN
The registered design professional shall indicate on the construction documents the steel joist and/or
steel joist girder designations from the specifications listed in Section 605.1 and shall indicate the
requirements for joist and joist girder design, layout, end supports, anchorage, non-SJI standard
bridging, bridging termination connections and bearing connection design to resist uplift and lateral
loads. These documents shall indicate special requirements as follows:
1. Special loads including:
1.1. Concentrated loads;
1.2. Nonuniform loads;
All rights reserved
394 / 496
1.3. Net uplift loads;
1.4. Axial loads;
1.5. End moments; and
1.6. Connection forces.
2. Special considerations including:
2.1. Profiles for nonstandard joist and joist girder configurations (standard joist and joist girder
configurations are as indicated in the SJI catalog);
2.2. Oversized or other nonstandard web openings; and
2.3. Extended ends.
3. Deflection criteria for live and total loads for non-SJI standard joists.
605.3 CALCULATIONS
The steel joist and joist girder manufacturer shall design the steel joists and/or steel joist girders in
accordance with the current SJI specifications and load tables to support the load requirements of
Section 605.2. The registered design professional may require submission of the steel joist and joist
girder calculations as prepared by a registered design professional responsible for the product design.
If requested by the registered design professional, the steel joist manufacturer shall submit design
calculations with a cover letter bearing the seal and signature of the joist manufacturer’s registered
design professional. In addition to standard calculations under this seal and signature, submittal of the
following shall be included:
1. Non-SJI standard bridging details (e.g. for cantilevered conditions, net uplift, etc.).
2. Connection details for:
2.1. Non-SJI standard connections (e.g. flush-framed or framed connections);
2.2. Field splices; and
2.3. Joist headers.
605.4 STEEL JOIST DRAWINGS
Steel joist placement plans shall be provided to show the steel joist products as specified on the
construction documents and are to be utilized for field installa- tion in accordance with specific project
requirements as stated in Section 605.2. Steel placement plans shall include, at a minimum, the
following:
1. Listing of all applicable loads as stated in Section 605.2 and used in the design of the steel joists and
joist girders as specified in the construction documents.
2. Profiles for nonstandard joist and joist girder configurations (standard joist and joist girder
configurations are as indicated in the SJI catalog).
3. Connection requirements for:
3.1. Joist supports;
3.2. Joist girder supports;
3.3. Field splices; and
3.4. Bridging attachments.
4. Deflection criteria for live and total loads for non-SJI standard joists.
5. Size, location and connections for all bridging.
6. Joist headers.
605.5 CERTIFICATION
At completion of manufacture, the steel joist manufacturer shall submit a certificate of compliance in
accordance with Section 903.2 stating that work was per- formed in accordance with approved
construction documents and with SJI standard specifications.
All rights reserved
395 / 496
SECTION 606 STEEL CABLE STRUCTURES
606.1 GENERAL
The design, fabrication and erection including related connections, and protective coatings of steel
cables for buildings shall be in accordance with ASCE 19.
606.2 SEISMIC REQUIREMENTS FOR STEEL CABLE STRUCTURES
The design strength of steel cables shall be determined by the provisions of ASCE 19 except as modified
by these provisions.
1. A load factor of 1.1 shall be applied to the prestress force included in T3 and T4 as defined in Section
3.12.
2. In Section 3.2.1, Item (c) shall be replaced with “1.5 T3” and Item (d) shall be replaced with
“1.5 T4.”
SECTION 607 COLD-FORMED STEEL LIGHT-FRAME CONSTRUCTION
607.1 GENERAL
The design and installation of structural members and nonstructural members utilized in cold-formed
steel light-frame construction where the specified minimum base steel thickness is between 0.50 mm
and 3.00 mm shall be in accordance with AISI S200 and Sections 2210.2 through 2210.7, as applicable.
607.2 HEADER DESIGN
Headers, including box and back-to-back headers, and double and single L-headers shall be designed in
accordance with AISI S212 or AISI S100.
607.3 TRUSSES
607.3.1 DESIGN
Cold-formed steel trusses shall be designed in accordance with AISI S214, Sections 607.3.1
through 607.3.5 and accepted engineering practice.
607.3.2 TRUSS DESIGN DRAWINGS
The truss design drawings shall conform to the requirements of Section B2.3 of AISI S214 and
shall be provided with the shipment of trusses delivered to the job site. The truss design
drawings shall include the details of permanent individual truss member restraint/bracing in
accordance with Section B6(a) or B6(c) of AISI S214 where these methods are utilized to provide
restraint/bracing.
607.3.3 TRUSSES SPANNING 18.000 mm OR GREATER
The owner shall contract with a registered design professional for the design of the temporary
installation restraint/bracing and the permanent individual truss member restraint/bracing for
trusses with clear spans 18 000 mm or greater. Special inspection of trusses over 18 000 mm in
length shall conform to Section 903.
607.3.4 TRUSS QUALITY ASSURANCE
Trusses not part of a manufacturing process that provides requirements for quality control done
under the supervision of a third-party quality control agency, shall be manufactured in
compliance with Sections 903.2 and 903.3, as applicable.
All rights reserved
396 / 496
607.4 WALL STUD DESIGN
Wall studs shall be designed in accordance with either AISI S211 or AISI S100.
607.5 FLOOR AND ROOF SYSTEM DESIGN
Framing for floor and roof systems in buildings shall be designed in accordance with either AISI S210 or
AISI S100.
607.6 LATERAL DESIGN
Light-frame shear walls, diagonal strap bracing that is part of a structural wall and diaphragms used to
resist wind, seismic and other in-plane lateral loads shall be designed in accordance with AISI S213.
607.7 PERSPECTIVE FRAMING
Detached one- and two-family dwellings and townhouses, less than or equal to three stories above
grade plane, shall be permitted to be constructed in accordance with AISI S230 subject to the
limitations therein.
All rights reserved
397 / 496
CHAPTER 7
MASONRY
SECTION 701 GENERAL
701.1 SCOPE
This chapter shall govern the materials, design, construction and quality of masonry.
701.2 DESIGN METHODS
Masonry shall comply with the provisions of one of the following design methods in this chapter as
well as the requirements of Sections 701 through 704. Masonry designed by the allowable stress design
provisions of Section 701.2.1, the strength design provisions of Section 701.2.2 shall comply with
Section 705.
701.2.1 ALLOWABLE STRESS DESIGN
Masonry designed by the allowable stress design method shall comply with the provisions of
Sections 706 and 707.
701.2.2 STRENGTH DESIGN
Masonry designed by the strength design method shall comply with the provisions of Sections 706
and 708, except that autoclaved aerated concrete (AAC) masonry shall comply with the provisions
of Section 706.
701.2.3 EMPIRICAL DESIGN
Masonry designed by the empirical design method shall comply with the provisions of Sections
706 and 709.
701.3 CONSTRUCTION DOCUMENTS
The construction documents shall show all of the items required by this code including the following:
1. Specified size, grade, type and location of reinforcement, anchors and wall ties.
2. Reinforcing bars to be welded and welding procedure.
3. Size and location of structural elements.
4. Provisions for dimensional changes resulting from elastic deformation, creep, shrinkage,
temperature and moisture.
5. Loads used in the design of masonry.
6. Specified compressive strength of masonry at stated ages or stages of construction for which masonry
is designed, except where specifically exempted by this code.
7. Details of anchorage of masonry to structural members, frames and other construction, including
the type, size and location of connectors.
8. Size and location of conduits, pipes and sleeves.
9. The minimum level of testing and inspection as defined in Chapter 9, or an itemized testing and
inspection program that meets or exceeds the requirements of Chapter 9.
SECTION 702 NOTATIONS
db
= Diameter of reinforcement, mm.
Fs
= Allowable tensile or compressive stress in reinforce- ment MPa.
fr
f’ m
= Modulus of rupture MPa.
= Specified compressive strength of AAC masonry, the minimum compressive strength for a
class of AAC masonry as specified in ASTM C , MPa.
= Specified compressive strength of masonry at age of 28 days, MPa.
f’mi
= Specified compressive strength of masonry at the time of prestress transfer, MPa.
f΄AAC
All rights reserved
398 / 496
K
= The lesser of the masonry cover, clear spacing between adjacent reinforcement, or five times
db, mm.
Ls
= Distance between supports, mm.
ld
P
St
= Required development length or lap length of reinforcement, mm.
= The applied load at failure, N.
= Thickness of the test specimen measured parallel to the direction of load, mm.
Sw
= Width of the test specimen measured parallel to the loading cylinder, mm.
SECTION 703 MASONRY CONSTRUCTION MATERIALS
703.1 CONCRETE MASONRY UNITS
Concrete masonry units shall conform to the following standards: ASTM C 55 for concrete brick; ASTM C
73 for calcium silicate face brick; ASTM C 90 for load-bearing concrete masonry units or ASTM C 744 for
prefaced concrete and calcium silicate masonry units.
703.2 CLAY OR SHALE MASONRY UNITS
Clay or shale masonry units shall conform to the following standards: ASTM C 34 for structural clay loadbearing wall tile; ASTM C 56 for structural clay nonload-bearing wall tile; ASTM C 62 for building brick
(solid masonry units made from clay or shale); ASTM C 1088 for solid units of thin veneer brick; ASTM C
126 for ceramic-glazed structural clay facing tile, facing brick and solid masonry units; ASTM C 212 for
structural clay facing tile; ASTM C 216 for facing brick (solid masonry units made from clay or shale);
ASTM C 652 for hollow brick (hollow masonry units made from clay or shale) or ASTM C 1405 for
glazed brick (single-fired solid brick units).
703.3 AAC MASONRY
AAC masonry units shall conform to ASTM C 1386 for the strength class specified.
703.4 STONE MASONRY UNITS
Stone masonry units shall conform to the following standards: ASTM C 503 for marble building stone
(exterior); ASTM C 568 for limestone building stone; ASTM C 615 for granite building stone; ASTM C
616 for sandstone building stone; or ASTM C 629 for slate building stone.
703.5 CERAMIC TILE
Ceramic tile shall be as defined in, and shall conform to the requirements of, ANSI A137.1.
703.6 MORTAR
Mortar for use in masonry construction shall conform to ASTM C 270 and Articles 2.1 and 2.6 A of
TMS 602/ACI 530.1/ASCE 6, except for mortars listed in Section 703.7. Type S or N mortar conforming
to ASTM C 270 shall be used for glass unit masonry.
703.7 SURFACE-BONDING MORTAR
Surface-bonding mortar shall comply with ASTM C 887. Surface bonding of concrete masonry units
shall comply with ASTM C 946.
703.8 MORTARS FOR CERAMIC WALL AND FLOOR TILE
Portland cement mortars for installing ceramic wall and floor tile shall comply with ANSI A108.1A and
ANSI A108.1B and be of the compositions indicated in Table 703.8-1.
All rights reserved
399 / 496
TABLE 703.8-1 CERAMIC TILE MORTAR COMPOSITIONS
LOCATION
MORTAR
Scratchcoat
Walls
Setting bed and leveling coat
Floors
Ceilings
Setting bed
Scratchcoat and sand bed
COMPOSITION
1 cement; 1/5 hydrated lime;
4 dry or 5 damp sand
1 cement; 1/2 hydrated lime;
5 damp sand to 1 cement
1 hydrated lime, 7 damp sand
1 cement; 1/10 hydrated lime;
5 dry or 6 damp sand; or 1
cement; 5 dry or 6 damp sand
1 cement; 1/2 hydrated lime;
21/2 dry sand or 3 damp sand
703.9 PORTLAND CEMENT GROUTS
Portland cement grouts used for the installation of ceramic tile shall comply with ANSI A118.6.
Portland cement grouts for tile work shall be installed in accordance with ANSI A108.10.
703.9.1 GROUT
Grout shall comply with Article 2.2 of TMS 602/ACI 530.1/ASCE 6.
703.10 METAL REINFORCEMENT AND ACCESSORIES
Metal reinforcement and accessories shall conform to Article 2.4 of TMS 602/ACI 530.1/ASCE 6. Where
unidentified reinforcement is approved for use, not less than three tension and three bending tests
shall be made on representative specimens of the reinforcement from each shipment and grade of
reinforcing steel proposed for use in the work.
SECTION 704 CONSTRUCTION
704.1 MASONRY CONSTRUCTION
Masonry construction shall comply with the requirements of Sections 704.1.1 through 704.4 and
with TMS 602/ACI 530.1/ASCE 6.
704.1.1 TOLERANCES
Masonry, except masonry veneer, shall be constructed within the tolerances specified in TMS
602/ACI 530.1/ASCE 6.
704.1.2 PLACING MORTAR AND UNITS
Placement of mortar, grout, and clay, concrete, glass, and AAC masonry units shall comply with
TMS 602/ACI 530.1/ASCE 6.
704.1.3 INSTALLATION OF WALL TIES
Wall ties shall be installed in accordance with TMS 602/ACI 530.1/ASCE 6.
704.1.4 CHASES AND RECESSES
Chases and recesses shall be constructed as masonry units are laid. Masonry directly above
chases or recesses wider than 300 mm shall be supported on lintels.
704.1.5 LINTELS
The design for lintels shall be in accordance with the masonry design provisions of either Section
707 or 708.
All rights reserved
400 / 496
704.1.6 SUPPORT ON WOOD
Masonry shall not be supported on wood girders or other forms of wood construction.
704.2 CORBELED MASONRY
Corbeled masonry shall comply with the requirements of Section 1.12 of TMS 402/ACI 530/ASCE
5.
704.2.1 MOLDED CORNICES
Unless structural support and anchorage are provided to resist the overturning moment the
center of gravity of projecting masonry or molded cornices shall lie within the middle one-third
of the supporting wall. Terra cotta and metal cornices shall be provided with a structural frame of
approved noncombustible material anchored in an approved manner.
704.3 COLD WEATHER CONSTRUCTION
The cold weather construction provisions of TMS 602/ACI 530.1/ASCE 6, Article 1.8 C, shall be
implemented when the ambient temperature falls below 4°C.
704.4 HOT WEATHER CONSTRUCTION
The hot weather construction provisions of TMS 602/ACI 530.1/ASCE 6, Article 1.8 D, shall be
implemented when the ambient air temperature exceeds 40°C, or 30°C with a wind velocity greater
than 13.0 km/hr.
SECTION 705 QUALITY ASSURANCE
705.1 GENERAL
A quality assurance program shall be used to ensure that the constructed masonry is in compliance
with the construction documents. The quality assurance program shall comply with the inspection
and testing requirements of Chapter 9.
705.2 ACCEPTANCE RELATIVE TO TRENGTH REQUIREMENTS
705.2.1 COMPLIANCE WITH f΄m and f΄AAC
Compressive strength of masonry shall be considered satisfactory if the compressive strength of
each masonry wyth e and grouted collar joint equals or ex ceeds the value of f’ m for clay and
concrete masonry and f’AAC for AAC masonry. For partially grouted clay and concrete
masonry, the compressive strength of both the grouted and ungrouted masonry shall equal or
exceed the applicable f’m . At the time of prestress, the comp ressive strength of the masonry
shall equal or exceed f’mi, which shall be less than or equal to f’m.
705.2.2 DETERMINATION OF COMPRESSIVE STRENGTH
The compressive strength for each wythe shall be determined by the unit strength method or by
the prism test method as specified herein.
705.2.2.1 UNIT STRENGTH METHOD
705.2.2.1.1 CLAY MASONRY
The compressive strength of masonry shall be determined based on the strength of the
units and the type of mortar specified using Table 705.2.2.1.1-1, provided:
1. Units are sampled and tested to verify compli- ance with ASTM C 62, ASTM C 216 or
ASTM C 652.
2. Thickness of bed joints does not exceed 16.0 mm.
3. For grouted masonry, the grout meets one of the following requirements:
All rights reserved
401 / 496
3.1. Grout conforms to Article 2.2 of TMS 602/ACI 530.1/ASCE 6.
3.2. Minimum grout com pressive strength equals or exceeds f’m but not less than
14.00 MPa. The compressive strength of grout shall be determined in accordance
with ASTM C 1019.
TABLE 705.2.2.1.1-1 COMPRESSIVE STRENGTH OF CLAY MASONRY
NET AREA COMPRESSIVE STRENGTH OF CLAY MASONRY UNITS (MPa)
Type M or S mortar
Type N mortar
NET AREA COMPRESSIVE STRENGTH OF MASONRY
(MPa)
12.00
15.00
7.00
23.00
30.00
10.00
34.00
43.00
14.00
45.00
57.00
17.00
57.00
70.00
21.00
68.00
—
24.00
80.00
—
28.00
705.2.2.1.2 CONCRETE MASONRY
The compressive strength of masonry shall be determined based on the strength of the
unit and type of mortar specified using Table 705.2.2.1.2-1, provided:
1. Units are sampled and tested to verify compliance with ASTM C 55 or ASTM C 90.
2. Thickness of bed joints does not exceed 16.0 mm.
3. For grouted masonry, the grout meets one of the following requirements:
3.1. Grout conforms to Article 2.2 of TMS 602/ACI 530.1/ASCE 6.
3.2. Minimum grout com pressive strength equals or exceeds f΄m but not less than
14.00 MPa. The compressive strength of grout shall be determined in
accordance with ASTM C 1019.
TABLE 705.2.2.1.2-1 COMPRESSIVE STRENGTH OF CONCRETE MASONRY
NET AREA COMPRESSIVE STRENGTH OF CLAY MASONRY UNITS (MPa)
NET AREA COMPRESSIVE STRENGTH OF MASONRY
(MPa)
Type M or S mortar
Type N mortar
9.00
9.00
7.00
13.00
15.00
10.00
20.00
21.00
14.00
26.00
28.00
17.00
33.00
36.00
21.00
705.2.2.1.3 AAC MASONRY
The compressive strength of AAC masonry shall be based on the strength of the AAC
masonry unit only and the following shall be met:
1. Units conform to ASTM C 1386.
2. Thickness of bed joints does not exceed 3.0 mm.
3. For grouted masonry, the grout meets one of the following requirements:
3.1. Grout conforms to Article 2.2 of TMS 602/ACI 530.1/ASCE 6.
3.2. Minimum grout compressive strength equals or exceeds f’AAC but not less than
215.00 MPa. The compressive strength of grout shall be determined in
accordance with ASTM C 1019.
All rights reserved
402 / 496
705.2.2.2 PRISM TEST METHOD
705.2.2.2.1 GENERAL
The compressive strength of clay and concrete masonry shall be determined by the prism
test method:
1. Where specified in the construction documents.
2. Where masonry does not meet the requirements for application of the unit strength
method in Section 705.2.2.1.
705.2.2.2.2 NUMBER OF PRISMS PER TEST
A prism test shall consist of three prisms constructed and tested in accordance with
ASTM C 1314.
705.3 TESTING PRISMS FROM CONSTRUCTED MASONRY
When approved by the building official, acceptance of masonry that does not meet the requirements
of Section 705.2.2.1 or 705.2.2.2 shall be permitted to be based on tests of prisms cut from the
masonry construction in accordance with Sections 705.3.1, 705.3.2 and 705.3.3.
705.3.1 PRISM SAMPLING AND REMOVAL
A set of three masonry prisms that are at least 28 days old shall be saw cut from the masonry for
each 450 m2 of the wall area that is in question but not less than one set of three masonry prisms
for the project. The length, width and height dimensions of the prisms shall comply with the
requirements of ASTM C 1314. Transporting, preparation and testing of prisms shall be in
accordance with ASTM C 1314.
705.3.2 COMPRESSIVE STRENGTH CALCULATIONS
The compressive strength of prisms shall be the value calculated in accordance ASTM C 1314,
except that the net cross-sectional area of the prism shall be based on the net mortar bedded
area.
705.3.3 COMPLIANCE
Compliance with the requirement for the specified compressive strength of masonry, f’m shall be
considered satisfied provided the modified compressive strength equals or exceeds the specified
f’m. Additional testing of specimens cut from locations in question shall be
permitted.
SECTION 706 SEISMIC DESIGN
706.1 SEISMIC DESIGN REQUIREMENTS FOR MASONRY
Masonry structures and components shall comply with the requirements in Section 1.17 of TMS
402/ACI 530/ASCE 5 depending on the structure’s seismic design category as determined in Section
311.
SECTION 707 ALLOWABLE STRESS DESIGN
707.1 GENERAL
The design of masonry structures using allowable stress design shall comply with Section 706 and the
requirements of Chapters 1 and 2 of TMS 402/ACI 530/ASCE 5 except as modified by Sections 707.2
through 707.5.
707.2
TMS 402/ACI 530/ASCE 5, Section 2.1.2, load combinations.
All rights reserved
403 / 496
707.3
TMS 402/ACI 530/ASCE 5, Section 2.1.9.7.1.1, lap splices.
The minimum length of lap splices for reinforcing bars in tension or compression, ld, shall be
ld = 0.29dbfs
EQUATION 707.3-1
but not less than 300 mm. In no case shall the length of the lapped splice be less than
40 bar diameters.
where:
db = Diameter of reinforcement, mm.
fs = Computed stress in reinforcement due to design loads, MPa.
In regions of moment where the design tensile stresses in the reinforcement are greater than 80
percent of the allowable steel tension stress, Fs, the lap length of splices shall be increased not less than
50 percent of the minimum required length. Other equivalent means of stress transfer to accomplish
the same 50 percent increase shall be permitted. Where epoxy coated bars are used, lap length shall be
increased by 50 percent.
707.4
TMS 402/ACI 530/ASCE 5, Section 2.1.9.7, splices of reinforcement.
Splices of reinforcement. Lap splices, welded splices or mechanical splices are permitted in accordance
with the provisions of this section. All welding shall conform to AWS D1.4. Welded splices shall be of ASTM
A706 steel reinforcement. Reinforcement larger than No. 29 shall be spliced using mechanical
connections in accordance with Section 2.1.9.7.3.
707.5
TMS 402/ACI 530/ASCE 5, Section 2.3.6, maximum bar size.
The bar diameter shall not exceed one-eighth of the nominal wall thickness and shall not exceed onequarter of the least dimension of the cell, course or collar joint in which it is placed.
SECTION 708 STRENGTH DESIGN OF MASONRY
708.1 GENERAL
The design of masonry structures using strength design shall comply with Section 706 and the
requirements of Chapters 1 and 3 of TMS 402/ACI 530/ASCE 5, except as modified by Sections 708.2
through 708.3.
Exception: AAC masonry shall comply with the requirements of Chapter 1 and Appendix A of
TMS 402/ACI 530/ASCE 5.
708.2
TMS 402/ACI 530/ASCE 5, Section 3.3.3.3 development.
The required development length of reinforcement shall be determined by Equation (3-16), but shall
not be less than 300 mm and need not be greater than 72 db.
708.3
TMS 402/ACI 530/ASCE 5, Section 3.3.3.4, splices.
A welded splice shall have the bars butted and welded to develop at least 125 percent of the yield
strength, fy , of the bar in tension or compression, as required. Welded splices shall be of ASTM A 706
steel reinforcement. Welded splices shall not be permitted in plastic hinge zones of intermediate or
special reinforced walls or special moment frames of masonry.
All rights reserved
404 / 496
Mechanical splices shall be classified as Type 1 or 2 according to Section 21.2.6.1 of Appendix A. Type 1
mechanical splices shall not be used within a plastic hinge zone or within a beam-column joint of
intermediate or special reinforced masonry shear walls or special moment frames. Type 2 mechanical
splices are permitted in any location within a member.
SECTION 709 EMPIRICAL DESIGN OF MASONRY
709.1 GENERAL
Empirically designed masonry shall conform to the requirements of Chapter 5 of TMS 402/ACI
530/ASCE 5, except where otherwise noted in this section.
709.1.1 LIMITATIONS
The use of empirical design of masonry shall be limited as noted in Section 5.1.2 of TMS 402/ACI
530/ASCE 5. The use of dry-stacked, surface-bonded masonry shall be prohibited in Occupancy
Category IV structures. In buildings that exceed one or more of the limitations of Section 5.1.2 of
TMS 402/ACI 530/ASCE 5, masonry shall be designed in accordance with the engineered design
provisions of Section 701.2.1, 701.2.2 or 701.2.3.
709.2 ADOBE CONSTRUCTION
Adobe construction shall comply with this section and shall be subject to the requirements of this code
for Type V construction, Chapter 5 of TMS 402/ACI 530/ASCE 5, and this section.
709.2.1 UNSTABILIZED ADOBE
709.2.1.1 COMPRESSIVE STRENGTH
Adobe units shall have an average compressive strength of 2000 kPa when tested in
accordance with ASTM C 67. Five samples shall be tested and no individual unit is permitted
to have a compressive strength of less than 1700 kPa.
709.2.1.2 MODULUS OF RUPTURE
Adobe units shall have an average modulus of rupture of 345 kPa when tested in accordance
with the following procedure. Five samples shall be tested and no individual unit shall have a
modulus of rupture of less than 240 kPa.
709.3.1.2.1 SUPPORT CONDITIONS
A cured unit shall be simply supported by 50 mm diameter cylindrical supports located
50mm in from each end and extending the full width of the unit.
709.3.1.2.2 LOADING CONDITIONS
A 50 mm diameter cylinder shall be placed at midspan parallel to the supports.
709.3.1.2.3 TESTING PROCEDURE
A vertical load shall be applied to the cylinder at the rate of 35 N/s until failure occurs.
709.3.1 MODULUS OF RUPTURE DETERMINATION
The modulus of rupture shall be determined by the equation:
2
fr = 3 PLs /2 Sw (St )
EQUATION 709.3.1-1
where, for the purposes of this section only:
Sw = W i d t h of the test specimen measured parallel to the loading cylinder, mm.
fr = Modulus of rupture, MPa.
All rights reserved
405 / 496
Ls = Distance between supports, mm.
St = T h i c k n e s s of the test specimen measured parallel to the direction of load, mm.
P = The applied load at failure, pounds N.
709.3.2 MOISTURE CONTENT REQUIREMENTS
Adobe units shall have a moisture content not exceeding 4 percent by weight.
709.3.3 SHRINKAGE CRACKS
Adobe units shall not contain more than three shrinkage cracks and any single shrinkage crack
shall not exceed 70 mm in length or 3.0 mm in width.
709.4 STABILIZED ADOBE
709.4.1 MATERIAL REQUIREMENTS
Stabilized adobe shall comply with the material requirements of unstabilized adobe in addition
to Section 709.4.1.
709.4.2 SOIL REQUIREMENTS
Soil used for stabilized adobe units shall be chemically compatible with the stabilizing material.
709.4.3 ABSORBTION REQUIREMENTS
A 100 mm cube, cut from a stabilized adobe unit dried to a constant weight in a ventilated oven
at 100°C to 115°C, shall not absorb more than 21/2 percent moisture by weight when placed
upon a constantly water-saturated, porous surface for seven days. A minimum of five specimens
shall be tested and each specimen shall be cut from a separate unit.
709.4.4 ALLOWABLE STRESS
The allowable compressive stress based on gross cross-sectional area of adobe shall not exceed
200 kPa.
709.4.5 BOLTS
Bolt values shall not exceed those set forth in Table 709.4.5-1.
TABLE 709.4.5-1 COMPRESSIVE STRENGTH OF CONCRETE MASONRY
DIAMETER OF BOLTS (mm)
MINIMUM EMBEDMENT (mm)
SHEAR (N)
12.0
16.00
20.00
22.00
25.00
28.00
300
380
450
530
610
900
1300
1700
2200
2600
709.4.6 CONSTRUCTION
709.4.6.1 GENERAL
Adobe construction shall be limited as stated in Sections 709.4.7.1 through 709.4.7.4.
709.4.6.2 HEIGHT RESTRICTIONS
Adobe construction shall be limited to buildings not exceeding one story, except that twostory construction is allowed when designed by a registered design professional.
All rights reserved
406 / 496
709.4.6.3 MORTAR RESTRICTIONS
Mortar for stabilized adobe units shall comply with Chapter 7 or adobe soil. Adobe soil used
as mortar shall comply with material requirements for stabilized adobe. Mortar for
unstabilized adobe shall be portland cement mortar.
709.4.6.4 MORTAR JOINTS
Adobe units shall be laid with full head and bed joints and in full running bond.
709.4.6.5 PARAPET WALLS
Parapet walls constructed of adobe units shall be waterproofed.
709.4.6.6 WALL THICKNESS
The minimum thickness of exterior walls in one-story buildings shall be 250 mm. The walls
shall be laterally supported at intervals not exceeding 7300 mm. The minimum thickness of
interior load-bearing walls shall be 200mm. In no case shall the unsupported height of any wall
constructed of adobe units exceed 10 times the thickness of such wall.
709.4.6.7 FOUNDATIONS
Foundations for adobe construction shall be in accordance with Sections 709.4.6.7.1 and
709.4.6.7.2.
709.4.6.7.1 FOUNDATION SUPPORT
Walls and partitions constructed of adobe units shall be supported by foundations or
footings that extend not less than 150 mm above adjacent ground surfaces and are
constructed of solid masonry (excluding adobe) or concrete. Footings and foundations
shall comply with Chapter 4.
709.4.6.7.2 LOWER COURSE REQUIREMENTS
Stabilized adobe units shall be used in adobe walls for the first 100 mm above the
finished first-floor elevation.
709.4.6.8 ISOLATED PIERS OR COLUMNS
Adobe units shall not be used for isolated piers or columns in a load-bearing capacity. Walls
less than 600 mm in length shall be considered isolated piers or columns.
709.4.6.9 TIE BEAMS
Exterior walls and interior load-bearing walls constructed of adobe units shall have a
continuous tie beam at the level of the floor or roof bearing and meeting the following
requirements.
709.4.6.10 CONCRETE TIE BEAMS
Concrete tie beams shall be a minimum depth of 150 mm and a minimum width of 250 mm.
Concrete tie beams shall be continuously reinforced with a minimum of two No. 4
reinforcing bars. The specifed compressive strength of concrete shall be at least 17.0 MPa.
709.4.6.11 WOOD TIE BEAMS
Wood tie beams shall be solid or built up of lumber having a minimum nominal thickness of 25
mm, and shall have a minimum depth of 150 mm and a minimum width of 250 mm. Joints in
wood tie beams shall be spliced a minimum of 150 mm. No splices shall be allowed within 300
mm of an opening. Wood used in tie beams shall be approved naturally decay-resistant or
preservative-treated wood.
All rights reserved
407 / 496
709.4.7 EXTERIOR FINISH
Exterior walls constructed of unstabilized adobe units shall have their exterior surface covered
with a minimum of two coats of portland cement plaster having a minimum thickness of 19.0
mm and conforming to ASTM C 926. Lathing shall comply with ASTM C 1063. Fasteners shall be
spaced at 400 mm o.c. maximum. Exposed wood surfaces shall be treated with an approved
wood preservative or other protective coating prior to lath application.
709.4.8 LINTELS
Lintels shall be considered structural members and shall be designed in accordance with the
applicable provisions of Chapter 3.
SECTION 710 MASONRY CHIMNEYS
710.1 DEFINITION
A masonry chimney is a chimney constructed of concrete or masonry, hereinafter referred to as
“masonry.” Masonry chimneys shall be constructed, anchored, supported and reinforced as required in
this chapter.
710.2 FOOTINGS AND FOUNDATIONS
Footings for masonry chimneys shall be constructed of concrete or solid masonry at least 300 mm thick
and shall extend at least 150 mm beyond the face of the foundation or support wall on all sides. Footings
shall be founded on natural undisturbed earth or engineered fill below frost depth. In areas not
subjected to freezing, footings shall be at least 300 mm below finished grade.
710.3 SEISMIC REINFORCING
Masonry or concrete chimneys shall be constructed, anchored, supported and reinforced as required
in this chapter. In Seismic Design Category C or D, masonry and concrete chimneys shall be reinforced
and anchored as detailed in Sections 710.3.1, 710.3.2 and 710.4. In Seismic Design Category A or B,
reinforcement and seismic anchorage is not required. In Seismic Design Category E or F, masonry and
concrete chimneys shall be reinforced in accordance with the requirements of Sections 7 01 through
708.
710.3.1 VERTICAL REINFORCING
For chimneys up to 1000 mm wide, four No. 4 continuous vertical bars anchored in the
foundation shall be placed in the concrete between wythes of solid masonry or within the cells of
hollow unit masonry and grouted in accordance with Section 703.9.1. Grout shall be prevented
from bonding with the flue liner so that the flue liner is free to move with thermal expansion. For
chimneys greater than 1000 mm wide, two additional No. 4 vertical bars shall be provided for each
additional 1000 mm in width or fraction thereof.
710.3.2 HORIZONTAL REINFORCING
Vertical reinforcement shall be placed enclosed within 8.0 mm ties, or other reinforcing of
equivalent net cross-sectional area, spaced not to exceed 450 mm o.c. in concrete, or placed in
the bed joints of unit masonry, at a minimum of every 450 mm of vertical height. Two such ties
shall be provided at each bend in the vertical bars.
710.4 SEISMIC ANCHORAGE
Masonry and concrete chimneys and foundations in Seismic Design Category C or D shall be anchored
at each floor, ceiling or roof line more than 1800 mm above grade, except where constructed
completely within the exterior walls. Anchorage shall conform to the
following requirements.
All rights reserved
408 / 496
710.4.1 ANCHORAGE
Two 5.0 mm by 25 mm straps shall be embedded a minimum of 300 mm into the chimney Straps
shall be hooked around the outer bars and extend 150 mm beyond the bend. Each strap shall be
fastened to a minimum of four floor joists with two 12.0 mm bolts.
710.5 CORBELING
Masonry chimneys shall not be corbeled more than half of the chimney’s wall thickness from a wall or
foundation, nor shall a chimney be corbeled from a wall or foundation that is less than 300 mm in
thickness unless it projects equally on each side of the wall, except that on the second story of a twostory dwelling, corbeling of chimneys on the exterior of the enclosing walls is permitted to equal the
wall thickness. The projection of a single course shall not exceed one-half the unit height or one-third
of the unit bed depth, whichever is less.
710.6 CHANGES IN DIMENSION
The chimney wall or chimney flue lining shall not change in size or shape within 150 mm above or
below where the chimney passes through floor components, ceiling components or roof components.
710.7 OFFSETS
Where a masonry chimney is constructed with a fireclay flue liner surrounded by one wythe of
masonry, the maximum offset shall be such that the centerline of the flue above the offset does not
extend beyond the center of the chim- ney wall below the offset. Where the chimney offset is
supported by masonry below the offset in an approved manner, the maximum offset limitations shall
not apply. Each individual corbeled masonry course of the offset shall not exceed the projection
limitations.
710.8 ADDITIONAL LOAD
Chimneys shall not support loads other than their own weight unless they are designed and
constructed to support the additional load. Masonry chimneys are permitted to be constructed as part
of the masonry walls or concrete walls of the building.
710.9 TERMINATION
Chimneys shall extend at least 600 mm higher than any portion of the building within 3000 mm, but shall
not be less than 900 mm above the highest point where the chimney passes through the roof.
710.9.1 SPARK ARRESTORS
Where a spark arrestor is installed on a masonry chimney, the spark arrestor shall meet all of the
following requirements:
1. The net free area of the arrestor shall not be less than four times the net free area of the
outlet of the chimney flue it serves.
2. The arrestor screen shall have heat and corrosion resistance equivalent to 19-gage galvanized
steel or 24-gage stainless steel.
3. Openings shall not permit the passage of spheres hav- ing a diameter greater than 13 mm nor
block the passage of spheres having a diameter less than 11 mm.
4. The spark arrestor shall be accessible for cleaning and the screen or chimney cap shall be
removable to allow for cleaning of the chimney flue.
710.10 WALL THICKNESS
Masonry chimney walls shall be constructed of concrete, solid masonry units or hollow masonry units
grouted solid with not less than 100 mm nominal thickness.
710.11 MASONRY VENEER CHIMNEYS
Where masonry is used as veneer for a framed chimney, through flashing and weep holes shall be
provided as required by AAC (Afghan Architecture Code)
All rights reserved
409 / 496
710.12 FLUE LINING (MATERIAL)
Masonry chimneys shall be lined. The lining material shall be appropriate for the type of appliance
connected, according to the terms of the appliance listing and the manufacturer’s instructions.
710.12.1 RESIDENTIAL-TYPE APPLIANCES (GENERAL)
Flue lining systems shall comply with one of the following:
1. Clay flue lining complying with the requirements of ASTM C 315.
2. Listed chimney lining systems complying with UL 1777.
3. Factory-built chimneys or chimney units listed for installation within masonry chimneys.
4. Other approved materials that will resist corrosion, erosion, softening or cracking from flue
gases and condensate at temperatures up to 980°C.
710.12.1.1 FLUE LININGS FOR SPECIFIC APPLIANCES
Flue linings intended for use with specific appliances shall comply with Sections 710.12.1.2
through 710.12.1.4 and Sections 710.2 and 710.3.
710.12.1.2 GAS APPLIANCES
Flue lining systems for gas appliances shall be in accordance with the International Fuel Gas
Code.
710.12.1.3 PELLET FUEL-BURNING APPLIANCES
Flue lining and vent systems for use in masonry chimneys with pellet fuel-burning appliances
shall be limited to flue lining systems complying with Section 710.12.1 and pellet vents listed
for installation within masonry chimneys (see Section 710.12.1.5 for marking).
710.12.1.4 OIL-FIRED APPLIANCES APPROVED FOR USE WITH L-VENT
Flue lining and vent systems for use in masonry chimneys with oil-fired appliances
approved for use with Type L vent shall be limited to flue lining systems complying with
Section 710.12.1 and listed chimney liners complying with UL 641 (see Section 710.12.1.5
for marking).
710.12.1.5 NOTICE OF USAGE
When a flue is relined with a material not complying with Section 710.12.1, the chimney shall
be plainly and permanently identified by a label attached to a wall, ceiling or other
conspicuous location adjacent to where the connector enters the chim- ney. The label shall
include the following message or equivalent language: “This chimney is for use only with
(type or category of appliance) that burns (type of fuel). Do not connect other types of
appliances.”
710.12.2 CONCRETE AND MASONRY CHIMNEYS FOR MEDIUM-HEAT APPLIANCES
710.12.2.1 GENERAL
Concrete and masonry chimneys for medium-heat appliances shall comply with Sections
710.1 through 710.5.
710.12.2.2 CONSTRUCTION
Chimneys for medium-heat appliances shall be constructed of solid masonry units or of
concrete with walls a minimum of 200 mm thick, or with stone masonry a minimum of 300
mm thick.
710.12.2.3 LINING
Concrete and masonry chimneys shall be lined with an approved medium-duty refractory
brick a minimum of 110 mm thick laid on the 110 mm in an approved medium-duty
refractory mortar. The lining shall start 600 mm or more below the lowest chimney
All rights reserved
410 / 496
connector entrance. Chimneys terminating 7600 mm or less above a chimney connector
entrance shall be lined to the top.
710.12.2.4 MULTIPLE PASSAGEWAYS
Concrete and masonry chimneys containing more than one passage-way shall have the
liners separated by a minimum 100 mm concrete or solid masonry wall.
710.12.2.5 TERMINATION HEIGHT
Concrete and masonry chimneys for medium-heat appliances shall extend a minimum of
3000 mm higher than any portion of any building within 7600 mm.
710.12.2.6 CLEARANCE
A minimum clearance of 100 mm shall be provided between the exterior surfaces of a
concrete or masonry chimney for medium-heat appliances and combustible material.
710.12.3 CONCRETE AND MASONRY CHIMNEYS FOR HIGH-HEAT APPLIANCES
710.12.3.1 GENERAL
Concrete and masonry chimneys for high-heat appliances shall comply with Sections 710.1
through 710.5.
710.12.3.2 CONSTRUCTION
Chimneys for high-heat appliances shall be constructed with double walls of solid masonry
units or of concrete, each wall to be a minimum of 200 mm thick with a minimum air- space of
50 mm between the walls.
710.12.3.3 LINING
The inside of the interior wall shall be lined with an approved high-duty refractory brick, a
minimum of 110 mm thick laid on the 110 mm in an approved high-duty refractory
mortar. The lining shall start at the base of the chimney and extend continuously to the top.
710.12.3.4 TERMINATION HEIGHT
Concrete and masonry chimneys for high-heat appliances shall extend a minimum of 6000
mm higher than any portion of any building within 15 000 mm.
710.12.3.5 CLEARANCE
Concrete and masonry chimneys for high-heat appliances shall have approved clearance
from buildings and structures to prevent overheating combustible materials, permit
inspection and maintenance operations on the chimney and prevent danger of burns to
persons.
710.13 CLAY FLUE LINING (INSTALLATION)
Clay flue liners shall be installed in accordance with ASTM C 1283 and extend from a point not less than
200 mm below the lowest inlet or, in the case of fireplaces, from the top of the smoke chamber to a
point above the enclosing walls. The lining shall be carried up vertically, with a maximum slope no greater
than 30 degrees (0.52 rad) from the vertical.
Clay flue liners shall be laid in medium-duty refractory mortar conforming to ASTM C 199 with tight
mortar joints left smooth on the inside and installed to maintain an air space or insulation not to
exceed the thickness of the flue liner separating the flue liners from the interior face of the chimney
masonry walls. Flue lining shall be supported on all sides. Only enough mortar shall be placed to make
the joint and hold the liners in position.
All rights reserved
411 / 496
710.14 ADDITIONAL REQUIREMENTS
710.14.1 LISTED MATERIALS
Listed materials used as flue linings shall be installed in accordance with the terms of their
listings and the manufacturer’s instructions.
710.14.2 SPACE AROUND LINING
The space surrounding a chimney lining system or vent installed within a masonry chimney shall
not be used to vent any other appliance.
Exception: This shall not prevent the installation of a separate flue lining in accordance with the
manufacturer’s instructions.
710.15 MULTIPLE FLUES
When two or more flues are located in the same chimney, masonry wythes shall be built between
adjacent flue linings. The masonry wythes shall be at least 100 mm thick and bonded into the walls of
the chimney.
Exception: When venting only one appliance, two flues are permitted to adjoin each other in the same
chimney with only the flue lining separation between them. The joints of the adjacent flue linings shall
be staggered at least 100 mm.
710.16 FLUE AREA (APPLIANCE)
Chimney flues shall not be smaller in area than the area of the connector from the appliance. Chimney
flues connected to more than one appliance shall not be less than the area of the largest connector
plus 50 percent of the areas of additional chimney connectors.
Exceptions:
1. Chimney flues serving oil-fired appliances sized in accordance with NFPA 31.
2. Chimney flues serving gas-fired appliances sized in accordance with the International Fuel
Gas Code.
710.17 FLUE AREA (MASONRY FIREPLACE)
Flue sizing for chimneys serving fireplaces shall be in accordance with Section 710.17.1 or 710.17.2.
710.17.1 MINIMUM AREA
Round chimney flues shall have a minimum net cross-sectional area of at least (1/12) of the fireplace opening. Square chimney flues shall have a minimum net cross-sectional area of at least
(1/10) of the fireplace opening. Rectangular chimney flues with an aspect ratio less than 2 to 1
shall have a minimum net cross-sectional area of at least (1/10) of the fireplace opening.
Rectangular chimney flues with an aspect ratio of 2 to 1 or more shall have a mini- mum net
cross-sectional area of at least (1/8) of the fireplace opening.
710.17.2 DETERMINATION OF MINIMUM AREA
The minimum net cross-sectional area of the flue shall be determined in accordance with Figure
710.17.2-1. A flue size providing at least the equivalent net cross-sectional area shall be used.
Cross-sectional areas of clay flue linings are as provided in Tables 710.17.2-1 and 710.17.2-2 or as
provided by the manufacturer or as measured in the field. The height of the chimney shall be
measured from the firebox floor to the top of the chimney flue.
All rights reserved
412 / 496
TABLE 710.17.2-1 NET CROSS-SECTIONAL AREA OF ROUND FLUE SIZES
FLUE SIZE, INSIDE DIAMETER, mm
150
180
205
255
275
305
380
455
a
CROSS-SECTIONAL AREA, mm
17600
25400
33000
51000
59300
73000
113400
162500
2
a: Flue sizes are based on ASTM C 315.
TABLE 710.17.2-2 NET CROSS-SECTIONAL AREA OF SQUARE AND RECTANGULAR FLUE SIZES
FLUE SIZE, OUTSIDE NOMINAL DIMENSIONS, mm
115 x 215
115 x 330
205 x 205
215 x 215
205 x 305
215 x 330
305 x 305
215 x 450
330 x 330
305 x 405
330 x 455
405 x 405
405 x 510
455 x 455
510 x 510
510 x 610
610 x 610
All rights reserved
CROSS-SECTIONAL AREA mm
14800
21900
27100
31600
43200
49000
65800
65100
81900
84500
111600
116700
143200
150300
192200
216100
278000
2
413 / 496
FIGURE 710.17.2-1 FLUE SIZES FOR MASONRY CHIMNEYS
710.18 INLET
Inlets to masonry chimneys shall enter from the side. Inlets shall have a thimble of fireclay, rigid
refractory material or metal that will prevent the connector from pulling out of the inlet or from
extending beyond the wall of the liner.
710.19 MASONRY CHIMNEY CLEANOUT OPENINGS
Cleanout openings shall be provided within 150 mm of the base of each flue within every masonry
chimney. The upper edge of the cleanout shall be located at least 150 mm below the lowest chimney
inlet opening. The height of the opening shall be at least 150 mm. The cleanout shall be provided with
a noncombustible cover.
All rights reserved
414 / 496
CHAPTER 8
WOOD
SECTION 801 GENERAL
801.1 SCOPE
The provisions of this chapter shall govern the materials, design, construction and quality of wood
members and their fasteners.
801.2 GENERAL DESIGN REQUIREMENTS
The design of structural elements or systems, constructed partially or wholly of wood or wood-based
products, shall be in accordance with one of the following methods:
1. Allowable stress design in accordance with Sections 803, 804 and 805.
2. Load and resistance factor design in accordance with Sections 803, 804 and 806.
3. Conventional light-frame construction in accordance with Section 803.
Exception: Buildings designed in accordance with the provisions of the AF&PA WFCM shall be
deemed to meet the requirements of the provisions of this Chapter.
4. The design and construction of log structures shall be in accordance with the provisions
of ICC 400.
801.3 NOMINAL SIZES
For the purposes of this chapter, where dimensions of lumber are specified, they shall be deemed to
be nominal dimensions unless specifically designated as actual dimensions (see Section 803.2).
SECTION 802 MINIMUM STANDARD AND QUANTITY
802.1 GENERAL
Structural sawn lumber; end-jointed lumber; prefabricated wood I-joists; structural glued-laminated
timber; wood structural panels, fiberboard sheathing (when used structurally ); hardboard siding
(when used structurally); particleboard; preservative-treated wood; structural log members; structural
composite lumber; round timber poles and piles; fire-retardant-treated wood; hardwood plywood;
wood trusses; joist hangers; nails; and staples shall conform to the applicable provisions of this
section.
802.1.1 SAWN LUMBER
Sawn lumber used for load-sup- porting purposes, including end-jointed or edge-glued lumber,
machine stress-rated or machine-evaluated lumber, shall be identified by the grade mark of a
lumber grading or inspection agency that has been approved by an accreditation body that
complies with DOC PS 20 or equivalent. Grading practices and identification shall comply with
rules published by an agency approved in accordance with the procedures of DOC PS 20 or
equivalent procedures. In lieu of a grade mark on the material, a certificate of inspection as to
species and grade issued by a lumber grading or inspection agency meeting the requirements of
this section is permitted to be accepted for precut, remanufactured or rough-sawn lumber
and for sizes larger than 75 mm nominal thickness.
Approved end-jointed lumber is permitted to be used interchangeably with solid-sawn members
of the same species and grade.
802.1.2 WOOD STRUCTURAL PANELS
Wood structural panels, when used structurally (including those used for siding, roof and wall
sheathing, subflooring, diaphragms and built-up members), shall conform to the requirements
All rights reserved
415 / 496
for their type in DOC PS 1 or PS 2. Each panel or member shall be identified for grade and glue
type by the trademarks of an approved testing and grading agency. Wood structural panel
components shall be designed and fabricated in accordance with the applicable standards listed
in Section 805.1 and identified by the trademarks of an approved testing and inspection agency
indicating conformance with the applicable standard. In addition, wood structural panels when
permanently exposed in outdoor applications shall be of exterior type, except that wood
structural panel roof sheath- ing exposed to the outdoors on the underside is permitted to be
interior type bonded with exterior glue, Exposure 1.
802.1.3 HARDBOARD
Hardboard siding used structurally shall be identified by an approved agency conforming to
CPA/ANSI A135.6. Hardboard underlayment shall meet the strength requirements of 5.6 mm or
6.4 mm service class hardboard planed or sanded on one side to a uniform thickness of not less
than 5.1 mm. Prefinished hardboard paneling shall meet the requirements of CPA/ANSI A135.5.
Other basic hardboard products shall meet the requirements of CPA/ANSI A135.4. Hardboard
products shall be installed in accordance with manufacturer’s recommendations.
802.1.4 PRESERVATIVE-TREATED WOOD
Lumber, timber, plywood, piles and poles supporting permanent structures required by 803.10.1
to be preservative treated shall conform to the requirements of the applicable AWPA Standard
U1 and M4 for the species, product, preservative and end use. Preservatives shall be listed in
Section 4 of AWPA U1. Lumber and plywood used in wood foundation systems shall conform to
AAC (Afghan Architecture Code).
802.1.4.1 IDENTIFICATION
Wood to be preservative treated shall bear the quality mark of an inspection agency that
maintains continuing supervision, testing and inspection over the quality of the preservativetreated wood. The quality mark shall be on a stamp or label affixed to the preservativetreated wood, and shall include the following information:
1. Identification of treating manufacturer.
2. Type of preservative used.
3. Minimum preservative retention
4. End use for which the product is treated.
5. AWPA standard to which the product was treated.
6. Identity of the accredited inspection agency.
802.1.4.2 MOISTURE CONTENT
Where preservative-treated wood is used in enclosed locations where drying in service
cannot readily occur, such wood shall be at a moisture content of 19 percent or less before
being covered with insulation, interior wall finish, floor covering or other materials.
802.1.5 STRUCTURAL LOG MEMBERS
Stress grading of structural log members of nonrectangular shape, as typically used in log
buildings, shall be in accordance with ASTM D 3957. Such structural log members shall be
identified by the grade mark of an approved lumber grading or inspection agency. In lieu of a
grade mark on the material, a certificate of inspection as to species and grade issued by a
lumber grading or inspection agency meeting the requirements of this section shall be
permitted.
802.1.6 ROUND TIMBER POLES AND PILES
Round timber poles and piles shall comply with ASTM D 3200 and ASTM D 25, respectively.
802.2 FIRE-RETARDANT-TREATED WOOD
Fire-retardant-treated wood is any wood product which, when impregnated with chemicals by a
pressure process or other means during manu- facture, shall have, when tested in accordance with
All rights reserved
416 / 496
ASTM E 84 or UL 723, a listed flame spread index of 25 or less and show no evidence of significant
progressive combustion when the test is continued for an additional 20-minute period. Additionally,
the flame front shall not progress more than 3200 mm beyond the centerline of the burners at any
time during the test.
802.2.1 PRESSURE PROCESS
For wood products impregnated with chemicals by a pressure process, the process shall be
performed in closed vessels under pressures not less than 345 kPa.
802.2.2 OTHER MEANS DURING MANUFACTURE
For wood products produced by other means during manufacture, the treatment shall be an
integral part of the manufacturing process of the wood product. The treatment shall provide
permanent protection to all surfaces of the wood product.
802.2.3 TESTING
For wood products produced by other means during manufacture, other than a pressure
process, all sides of the wood product shall be tested in accordance with and produce the results
required in Section 802.2. Wood structural panels shall be permitted to test only the front and
back faces.
802.2.4 LABELING
Fire-retardant-treated lumber and wood structural panels shall be labeled. The label shall
contain the following items:
1. The identification mark of an approved agency in accordance with Section 902.5.
2. Identification of the treating manufacturer.
3. The name of the fire-retardant treatment.
4. The species of wood treated.
5. Flame spread and smoke-developed index.
6. Method of drying after treatment.
7. Conformance with appropriate standards in accordance with Sections 802.2.2 through
802.2.5.
8. For fire-retardant-treated wood exposed to weather, damp or wet locations, include the
words “No increase in the listed classification when subjected to the Standard Rain Test”
(ASTM D 2898).
802.2.5 STRENGTH ADJUSTMENS
Design values for untreated lumber and wood structural panels, as specified in Section 802.1,
shall be adjusted for fire-retardant-treated wood. Adjustments to design values shall be
based on an approved method of investigation that takes into consideration the effects of the
anticipated temperature and humidity to which the fire-retardant-treated wood will be
subjected, the type of treatment and redrying procedures.
802.2.5.1 WOOD STRUCTURAL PANELS
The effect of treatment and the method of redrying after treatment, and exposure to high
temperatures and high humidities on the flexure properties of fire-retardant-treated softwood plywood shall be determined in accordance with ASTM D 5516. The test data
developed by ASTM D 5516 shall be used to develop adjustment factors, maximum loads and
spans, or both, for untreated plywood design values in accordance with ASTM D 6305. Each
manufacturer shall publish the allowable maximum loads and spans for service as floor and
roof sheathing for its treatment.
802.2.5.2 LUMBER
For each species of wood that is treated, the effects of the treatment, the method of
redrying after treatment and exposure to high temperatures and high humidities on the
All rights reserved
417 / 496
allowable design properties o f fire-retardan t- treated lumber shall b e determined in
accordance with ASTM D 5664. The test data developed by ASTM D 5664 shall be used
to develop modification factors for use at or near room temperature and at elevated
temperatures and humidity in accordance with ASTM D 6841. Each manufacturer shall
publish the modification factors for service at tem- peratures of not less than 27°C and for
roof framing. The roof framing modification factors shall take into consideration the
climatological location.
802.2.6 EXPOSURE TO WEATHER, DAMP OR WET LOCATIONS
Where fire-retardant-treated wood is exposed to weather, or damp or wet locations, it shall be
identified as “Exterior” to indicate there is no increase in the listed flame spread index as
defined in Section 802.2 when subjected to ASTM D 2898.
802.2.7 INTERIOR APPLICATIONS
Interior fire-retar- dant-treated wood shall have moisture content of not over 28 percent when
tested in accordance with ASTM D 3201 procedures at 92-percent relative humidity.
Interior fire-retardant-treated wood shall be tested in accordance with Section 802.2.5.1 or
802.2.5.2. Interior fire-retardant-treated wood designated as Type A shall be tested in
accordance with the provisions of this section.
802.2.8 MOISTURE CONTENT
Fire-retardant-treated wood shall be dried to a moisture content of 19 percent or less for lumber
and 15 percent or less for wood structural panels before use. For wood kiln dried after
treatment (KDAT), the kiln temperatures shall not exceed those used in kiln drying the lumber
and plywood submitted for the tests described in Section 802.2.5.1 for plywood and
802.2.5.2 for lumber.
802.2.9 TYPE I AND II CONSTRUCTION APPLICATIONS
See AAC (Afghan Architecture Code) for limitations on the use of fire-retardant-treated
wood in buildings of Type I or II construction.
802.3 HARDWOOD AND PLYWOOD
Hardwood and decorative plywood shall be manufactured and identified as required in HPVA HP-1.
802.4 TRUSSES
802.4.1 DESIGN
Wood trusses shall be designed in accor- dance with the provisions of this code and accepted
engineering practice. Members are permitted to be joined by nails, glue, bolts, timber
connectors, metal connector plates or other approved framing devices.
802.4.1.1 TRUSS DESIGN DRAWINGS
The written, graphic and pictorial depiction of each individual truss shall be provided to the
building official for approval prior to installation. Truss design drawings shall also be
provided with the shipment of trusses delivered to the job site. Truss design drawings shall
include, at a minimum, the information specified below:
1. Slope or depth, span and spacing;
2. Location of all joints and support locations;
3. Number of plies if greater than one;
4. Required bearing widths;
5. Design loads as applicable, including;
5.1. Top chord live load;
5.2. Top chord dead load;
All rights reserved
418 / 496
5.3. Bottom chord live load;
5.4. Bottom chord dead load;
5.5. Additional loads and locations; and
5.6. Environmental design criteria and loads (wind, rain, snow, seismic, etc.).
6. Other lateral loads, including drag strut loads;
7. Adjustments to wood member and metal connec- tor plate design value for conditions of
use;
8. Maximum reaction force and direction, including maximum uplift reaction forces where
applicable;
9. Metal-connector-plate type, size and thickness or gage, and the dimensioned location of
each metal connector plate except where symmetrically located relative to the joint
interface;
10. Size, species and grade for each wood member;
11. Truss-to-truss connections and truss field assembly requirements;
12. Calculated span-to-deflection ratio and maxi- mum vertical and horizontal deflection for
live and total load as applicable;
13. Maximum axial tension and compression forces in the truss members; and
14. Required permanent individual truss member restraint location and the method and
details of restraint/bracing to be used in accordance with Section 802.4.1.2.
802.4.1.2 PERMANENT
individual truss member restraint. Where permanent restraint of truss members is required
on the truss design drawings, it shall be accomplished by one of the following methods:
1. Permanent individual truss member restraint/bracing shall be installed using standard
industry lat- eral restraint/bracing details in accordance with generally accepted
engineering practice. Loca- tions for lateral restraint shall be identified on the truss
design drawing.
2. The trusses shall be designed so that the buckling of any individual truss member is
resisted inter- nally by the individual truss through suitable means (i.e., buckling
reinforcement by T-reinforcement or L-reinforcement, proprietary rein- forcement,
etc.). The buckling reinforcement of individual members of the trusses shall be installed
as shown on the truss design drawing or on supple mental truss member buckling
reinforcement details provided by the truss designer.
3. A project-specific permanent individual truss member restraint/bracing design shall be
permit- ted to be specified by any registered design profes- sional.
802.4.1.3 TRUSSES SPANNING 18 METER OR GREATER
The owner shall contract with any qualified registered design professional for the design of
the temporary installation restraint/bracing and the permanent individual truss member
restraint/bracing for all trusses with clear spans 18 m or greater.
802.4.1.4 TRUSS DESIGNER
The individual or organization responsible for the design of trusses.
802.4.1.4.1 TRUSS DESIGN DRAWINGS
Where required by the registered design professional, the building official or the
statutes of the jurisdiction in which the project is to be constructed, each individual truss
design drawing shall bear the seal and signature of the truss designer.
Exceptions:
1. Where a cover sheet and truss index sheet are combined into a single sheet and
attached to the set of truss design drawings, the single cover/truss index sheet is the
only document required to be signed and sealed by the truss designer.
All rights reserved
419 / 496
2. When a cover sheet and a truss index sheet are separately provided and attached to
the set of truss design drawings, the cover sheet and the truss index sheet are the
only documents required to be signed and sealed by the truss designer.
802.4.2 TRUSS PLACEMENT DIAGRAM
The truss manufac- turer shall provide a truss placement diagram that identifies the proposed
location for each individually designated truss and references the corresponding truss design
drawing. The truss placement diagram shall be provided as part of the truss submittal package,
and with the shipment of trusses delivered to the job site. Truss placement diagrams that serve
only as a guide for installation and do not deviate from the permit submittal drawings shall not be
required to bear the seal or signature of the truss designer.
802.4.3 TRUSS SUBMITTAL PACKAGE
The truss submittal package provided by the truss manufacturer shall consist of each individual
truss design drawing, the truss placement diagram, the permanent individual truss member
restraint/bracing method and details and any other structural details germane to the trusses;
and, as applicable, the cover/truss index sheet.
802.4.4 ANCHORAGE
The design for the transfer of loads and anchorage of each truss to the supporting structure is the
responsibility of the registered design professional.
802.4.5 ALTERATIONS TO TRUSSES
Truss members and com- ponents shall not be cut, notched, drilled, spliced or other- wise
altered in any way without written concurrence and approval of a registered design
professional. Alterations resulting in the addition of loads to any member (e.g., HVAC equipment,
piping, additional roofing or insulation, etc.) shall not be permitted without verification that the
truss is capable of supporting such additional loading.
802.4.6 TPI 1 SPECIFICATIONS
In addition to Sections 802.4.1 through 802.4.5, the design, manufacture and quality assurance
of metal-plate-connected wood trusses shall be in accordance with TPI 1. Job-site inspections
shall be in compliance with AAC (Afghan Architecture Code), as applicable.
802.4.7 TRUSS QUALITY ASSURANCE
Trusses not part of a manufacturing process in accordance with either Section802.4.6, which
provides requirements for quality control done under the supervision of a third-party quality
control agency, shall be manufactured in compliance with Sections 1704.2 and 1704.6, as
applicable.
802.5 TEST STANDARD FOR JOIST HANGERS AND CONNECTORS
For the required test standards for joist hangers and connectors, see Chapter 3.
802.6 NAILS AND STAPLES
Nails and staples shall conform to requirements of ASTM F 1667. Nails used for framing and sheathing
connections shall have minimum average bending yield strengths as follows: 550 MPa for shank
diameters larger than 4.50 mm but not larger than 6.45 mm, 620 MPa for shank diameters larger than
3.60 mm but not larger than 4.50 mm and 690 MPa for shank diameters of at least 2.50 mm but not
larger than 3.60 mm.
802.7 SHRINKAGE
Consideration shall be given in design to the possible effect of cross-grain dimensional changes considered vertically which may occur in lumber fabricated in a green condition.
All rights reserved
420 / 496
SECTION 803 GENERAL CONSTRUCTION REQUIREMENTS
803.1 GENERAL
The provisions of this section apply to design methods specified in this chapter.
803.2 SIZE OF STRUCTURAL MEMBERS
Computations to determine the required sizes of members shall be based on the net dimensions
(actual sizes) and not nominal sizes.
803.3 WALL FRAMING
The framing of exterior and interior walls shall be in accordance with the provisions specified in this
chapter unless a specific design is furnished.
803.3.1 BOTTOM PLATES
Studs shall have full bearing on a 50 mm (actual 40 mm) or larger plate or sill having a width at
least equal to the width of the studs.
803.3.2 FRAMING OVER OPENINGS
Headers, double joists, trusses or other approved assemblies that are of adequate size to
transfer loads to the vertical members shall be pro- vided over window and door openings in
load-bearing walls and partitions.
803.3.3 SHRINKAGE
Wood walls and bearing partitions shall not support more than two floors and a roof unless an
analysis satisfactory to the building official shows that shrinkage of the wood framing will not
have adverse effects on the structure or any plumbing, electrical or mechanical systems, or other
equipment installed therein due to excessive shrinkage or differential movements caused by
shrink- age. The analysis shall also show that the roof drainage system and the foregoing systems
or equipment will not be adversely affected or, as an alternate, such systems shall be designed to
accommodate the differential shrinkage or movements.
803.4 FLOOR AND ROOF FRAMING
The framing of wood-joisted floors and wood framed roofs shall be in accordance with the provisions
specified in this chapter unless a specific design is furnished.
803.5 FRAMING AROUND FLUES AND CHIMNEYS
Combustible framing shall be a minimum of 51 mm, but shall not be less than the distance specified in
the International Mechanical Code, from flues, chimneys and fireplaces, and 150 mm away from flue
openings.
803.6 WALL SHEATING
Except as provided for in AAC (Afghan Architecture Code) for weatherboarding or where stucco
construction that complies with AAC (Afghan Architecture Code) is installed, enclosed buildings shall
be sheathed with one of the materials of the nominal thickness specified in Table 802.6 or any other
approved material of equivalent strength or durability.
TABLE 803.6-1 MINIMUM THICKNESS OF WALL SHEATHING
SHEATHING TYPE
Wood boards
Fiberboard
Gypsum sheathing
Gypsum wallboard
Reinforced cement mortar
All rights reserved
MINIMUM THICKNESS
16 mm
13 mm
13 mm
13 mm
25 mm
MAXIMUM WALL STUD
SPACING
600 mm on center
400 mm on center
400 mm on center
400 mm on center
600 mm on center
421 / 496
803.6.1 WOOD STRUCTURAL PANEL SHEATING
Where wood structural panel sheathing is used as the exposed finish on the exterior of outside
walls, it shall have an exterior exposure durability classification. Where wood structural panel
sheathing is used elsewhere, but not as the exposed finish, it shall be of a type manufactured
with exterior glue (Exposure 1 or Exterior). Wood structural panel wall sheathing or siding used
as structural sheathing shall be capable of resisting wind pressures in accordance with Chapter 3.
Maximum wind speeds for wood structural panel sheathing used to resist wind pressures shall
be in accordance with Table 803.6.1-1 for enclosed buildings with a mean roof height not
greater than 9000 mm, an importance factor (I) of 1.0 and a topographic factor (Kz t) of 1.0.
TABLE 803.6.1-1 MAXIMUM BASIC WIND SPEED (m/s) (3-SECOND GUST) PERMITTED FOR WOOD
a, b, c
STRUCTURAL PANEL WALL SHEATHING USED TO RESIST WIND PRESSURES
MAXIMUM
WIND SPEED
(km/hr)
Wind exposure
category
D
C
B
135 145 175
145 160 175
300 200 240
170 300 210
300 200 150
135 145 300
135 145 150
PANEL NAIL
SPACING
Field
Edges
(mm
o.c.)
300
300
150
300
150
300
150
(mm
o.c.)
150
MAXIMUM
WALL STUD
SPACING
(mm)
400
150
400
150
400
150
600
MINIMUM
NOMINAL
PANEL
THICKNESS
(mm)
MINIMUM
WOOD
STRUCTURAL
PANEL SPAN
RATING
10
600/0
12
600/400
12
600/400
MINIMUM NAIL
PENETRATION
(mm)
SIZE
40
6 d common
(50 mm x 3
mm)
45
8 d common
(63 mm x 3
mm)
a. Panel strength axis shall be parallel or perpendicular to supports. Three-ply plywood sheathing with
studs spaced more than 400 mm on center shall be applied with panel strength axis perpendicular
to supports.
b. The table is based on wind pressures acting toward and away from building surfaces in accordance
with Chapter 3. Lateral requirements shall be in accordance with Section 804.
c. Wood structural panels with span ratings of wall-400 or wall-600 shall be permitted as an alternative
to panels with a 609/0 span rating. Plywood siding rated 400 o.c. or 600 o.c. shall be permitted as
an alternative to panels with a 600/400 span rating. Wall-400 and plywood siding 400 o.c. shall be
used with studs spaced a maximumof 400 mm o.c.
803.6.2 INTERIOR PANELING
Softwood wood structural panels used for interior paneling shall conform to the provisions of
AAC (Afghan Architecture Code) and shall be installed in accordance with Table 803.8.1-1. Panels
shall comply with DOC PS 1 or PS 2. Prefinished hardboard paneling shall meet the requirements
of CPA/ANSI A135.5. Hardwood plywood shall conform to HPVA HP-1.
803.7 FLOOR AND ROOF SHEATING
803.7.1 STRUCTURAL FLOOR SHEATING
Structural floor sheathing shall be designed in accordance with the general provisions of this
code and the special provisions in this section. Floor sheathing conforming to the provisions of
Table 803.7.1-1, 803.7.1-2, 803.7.1-3 or 803.7.1-4 shall be deemed to meet the requirements of
this section.
All rights reserved
422 / 496
TABLE 803.7.1-1 ALLOWABLE SPANS FOR LUMBER FLOOR AND ROOF SHEATHING
MINIMUM NET THICKNESS (mm) OF LUMBER PLACED
Diagonally to supports
Perpendicular to supports
Surfaced
c
c
Surfaced dry
Surfaced unseasoned
Surfaced dry
unseasoned
Floors
20
19
20
19
17
15
17
15
Roofs
20
19
17
a, b
SPAN (mm)
600
400
15
600
a. Installation details shall conform to Sections 803.7.1 and 803.7.2 for floor and roof sheathing,
respectively.
b. Floor or roof sheathing conforming with this table shall be deemed to meet the design criteria of
Section 803.7.
c. Maximum 19-percent moisture content.
TABLE 803.7.1-2 SHEATHING LUMBER, MINIMUM GRADE REQUIREMENTS: BOARD GRADE
SOLID FLOOR OR ROOF
SHEATHING
Utility
4 common or utility
No. 3
Merchantable
SPACED ROOF SHEATHING
Standard
3 common or standard
No. 2
Construction common
GRADING RULES
NLGA, WCLIB, WWPA
NLGA, WCLIB, WWPA, NSLB or NELMA
SPIB
RIS
TABLE 803.7.1-3 ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANEL SHEATHING AND
SINGLE-FLOOR GRADES CONTINUOUS OVER TWO OR MORE SPANS WITH STRENGTH AXIS
a, b
PERPENDICULAR TO SUPPORTS
FLOOR
d
c
ROOF
e
2
Load (kN/m )
Maximum
span (mm)
0
0
0
400
h
400
h,i
500
600
800
800
d
FLOOR
Live load
Total load
Without
edge support
With edge
f
support
1.4
1.4
1.4
2
1.4
1.4
1.7
1.7
1.7
2
2
2
2.4
2
2
2.1
2.1
2.1
400
500
500
g
600
700
800
900
1000
1200
400
500
600
600
800
1000
1200
1300
1500
h
400
h,i
500
600
800
1200
c
ROOF
e
Maximum
span (mm)
Maximum span (mm)
2
Load (kN/m )
Live load
Total load
2
1.4
1.2
2
2
2.4
2
1.7
2.4
2.4
Maximum span (mm)
Without
With edge
f
edge support
support
600
600
800
800
900
1200
1000
1200
1200
1500
SHEATHING GRADES
Panel span
Panel
rating
thickness
roof/floor
(mm)
span
9
400/0
9
500/0
9, 11, 13
600/0
11, 13
600/400
12, 13, 16
800/400
15, 16, 19, 22
1000/500
18, 19, 22
1200/600
22, 25
1300/800
22, 28
1500/800
SINGLE FLOOR GRADES
Panel
Panel span
thickness
rating
(mm)
13, 15, 16
400 o.c.
15, 16, 19
500 o.c.
18, 19
600 o.c.
22, 25
800 o.c.
27, 28
1200 o.c.
a. Applies to panels 600 mm or wider.
b. Floor and roof sheathing conforming with this table shall be deemed to meet the design criteria of
Section 803.7.
c. Uniform load deflection limitations 1/180 of span under live load plus dead load, 1/240 under live
load only.
d. Panel edges shall have approved tongue-and-groove joints or shall be supported with blocking
unless 6 mm minimum thickness underlayment or 140 mm of approved cellular or lightweight
All rights reserved
423 / 496
concrete is placed over the subfloor, or finish floor is 19 mm wood strip. Allowable uniform load
2
based on deflection of 1/360 of span is 4.8 kN/m except the span rating of 1200 mm on center is
2
based on a total load of 3.0 kN/m .
e. Allowable load at maximum span.
f. Tongue-and-groove edges, panel edge clips (one midway between each support, except two equally
spaced between supports 1200 mm on center), lumber blocking or other. Only lumber blocking
shall satisfy blocked diaphragm requirements.
g. For 13 mm panel, maximum span shall be 600 mm.
h. Span is permitted to be 600 mm on center where 19 mm wood strip flooring is installed at right
angles to joist.
i. Span is permitted to be 600 mm on center for floors where 140 mm of cellular or lightweight
concrete is applied over the panels.
TABLE 803.7.1-4 ALLOWABLE SPAN FOR WOOD STRUCTURAL PANEL COMBINATION SUBFLOORa, b
UNDERLAYMENT (SINGLE FLOOR)
(Panels Continuous Over Two or More Spans and Strength Axis Perpendicular to Supports)
1200
1200 o. c.
MAXIMUM SPACING OF JOISTS (mm)
800
600
500
Thickness (mm)
19
15
22
19
24
22
600 o. c.
800 o. c.
500 o. c.
IDENTIFICATION
400
c
Species group
1
2, 3
4
Single floor span
d
rating
12
15
19
400 o .c.
a. Spans limited to value shown because of possible effects of concentrated loads. Allowable uniform
2
loads based on deflection of 1/360 of span is 44 kN/m except allowable total uniform load for 35
2
mm wood structural panels over joists spaced 1200 mm on center is 30 kN/m . Panel edges shall
have approved tongue-and-groove joints or shall be supported with blocking, unless 6 mm
minimum thickness underlayment or 140 mm of approved cellular or lightweight concrete is placed
over the subfloor, or finish floor is 19 mm wood strip.
b. Floor panels conforming with this table shall be deemed to meet the design criteria of Section
803.7.
c. Applicable to all grades of sanded exterior-type plywood. See DOC PS 1 for plywood species groups.
d. Applicable to Underlayment grade, C-C (Plugged) plywood, and Single Floor grade wood structural
panels.
TABLE 803.7.1-5 ALLOWABLE LOAD (PSF) FOR WOOD STRUCTURAL PANEL ROOF SHEATHING
CONTINUOUS OVER TWO OR MORE SPANS AND STRENGTH AXIS PARALLEL TO SUPPORTS
a, b
(Plywood Structural Panels Are Five-Ply, Five-Layer Unless Otherwise Noted)
2
LOAD AT MAXIMUM SPAN (kN/m )
Total
Live
13
9
c
c
20
15.5
c
c
22
18
35.5
31
44.5
40
22.5
18
11
9
13
11
c
c
22.5
18
c
c
24.5
20
c
c
29
26.5
MAXIMUM SPAN
(mm)
600
600
600
600
600
400
600
600
600
600
600
THICKNESS (mm)
11
12
13
15, 16
18, 19
11
12
13
15
16
18, 19
PANEL GRADE
Structural I
sheathing
Sheathing, other
grades covered in
DOC PS 1 or DOC PS
2
a. Roof sheathing conforming with this table shall be deemed to meet the design criteria of Section
803.7.
All rights reserved
424 / 496
b. Uniform load deflection limitations 1/180 of span under live load plus dead load, 1/240 under live
load only. Edges shall be blocked with lumber or other approved type of edge supports.
c. For composite and four-ply plywood structural panel, load shall be reduced by 6.7 kN/m2.
803.7.2 STRUCTURAL ROOF SHEATING
Structural roof sheathing shall be designed in accordance with the general provisions of this
code and the special provisions in this section. Roof sheathing conforming to the provisions of
Table 803.7.1-1, Table 803.7.1-2, Table 803.7.1-3 or Table 803.7.1-5 shall be deemed to meet
the requirements of this section. Wood structural panel roof sheathing shall be bonded by
exterior glue.
803.8 CONNECTIONS AND FASTNERS
803.8.1 FASTENER REQUIREMENTS
Connections for wood members shall be designed in accordance with the appropriate
methodology in this Chapter. The number and size of fasteners connecting wood members shall
not be less than that set forth in Table 803.8.1-1.
TABLE 803.8.1-1 FASTENING SCHEDULE
CONNECTION
1. Joist to sill or girder
2. Bridging to joist
3. 25 mm x 152 mm subfloor or less
to each joist
4. Wider than 25 x 152 subfloor to
each joist
5. 50 mm subfloor to joist or girder
6. Sole plate to joist or blocking
Sole plate to joist or blocking at
braced wall panel
7. Top plate to stud
8. Stud to sole plate
9. Double studs
10. Double top plates
Double top plates
All rights reserved
a, m
FASTENING
3 - 8d common (63 mm x 3 mm)
3 – 76 mm x 3 mm3 nails
3 – 76 mm 14 gage staples
2 - 8d common (63 mm x 3 mm)
2 – 76 mm x 3 mm3 nails
2 – 76 mm 14 gage staples
LOCATION
toenail
toenail each end
2 - 8d common (63 mm x 3 mm)
face nail
3 - 8d common (63 mm x 3 mm)
face nail
2 - 16d common (89 mm x 4 mm)
16d (89 mm x 3.5 mm) at 406 mm o.c.
76 mm x 3 mm nails at 203 mm o.c.
76 mm 14 gage staples at 304 mm o.c.
blind and face nail
3 - 16d (89 mm x 3.5 mm) at 406 mm o.c.
4 - 76 mm x 3 mm nails at 406 mm o.c.
4 - 76 mm 14 gage staples at 406 mm o.c.
2 - 16d (89 mm x 4 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage
4 - 8d common (63 mm x 3 mm)
4 - 76 mm x 3 mm nails
3 - 76 mm 14 gage
braced wall panels
2 - 16d (89 mm x 4 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage
16d (89 mm x 3.5 mm) at 609 mm o.c.
76 mm x 3 mm nails at 203 mm o.c.
4 - 76 mm 14 gage staples at 203 mm o.c.
16d (89 mm x 3.5 mm) at 406 mm o.c.
76 mm x 3 mm nails at 304 mm o.c.
76 mm 14 gage staples at 304 mm o.c.
end nail
8 - 16d (89 mm x 4 mm)
12 - 76 mm x 3 mm nails
lap splice
typical face nail
end nail
toenail
face nail
typical face nail
425 / 496
11. Blocking between joists or
rafters to top plate
12. Rim joist to top plate
13. Top plates, laps and
intersections
14. Continuous header, two pieces
15. Ceiling joists to plate
16. Continuous header to stud
17. Ceiling joists, laps over
partitions
18. Ceiling joists to parallel rafters
19. Rafter to plate
20. 25 mm diagonal brace to each
stud and plate
21. 25 mm x 203 mm sheathing to
each bearing
22. Wider than 25 mm x 203 mm
sheathing to each bearing
23. Built-up corner studs
24. Built-up girder and beams
25. 50 mm planks
26. Collar tie to rafter
27. Jack rafter to hip
28. Roof rafter to 2-by ridge beam
29. Joist to band joist
All rights reserved
12 - 76 mm 14 gage staples
3 - 8d common (63 mm x 3 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage
8d common (63 mm x 3 mm) at 152 mm o.c.
76 mm x 3 mm nails 152 mm o.c.
76 mm 14 gage staple at 152 mm o.c.
2 - 16d (89 mm x 4 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage staples
16d (89 mm x 4 mm)
3 - 8d common (63 mm x 3 mm)
5 - 76 mm x 3 mm nails
5 - 76 mm 14 gage
4 - 8d common (63 mm x 3 mm)
3 - 16d (89 mm x 4 mm)
4 - 76 mm x 3 mm nails
4 - 76 mm 14 gage staples
3 - 16d (89 mm x 4 mm)
4 - 76 mm x 3 mm nails
4 - 76 mm 14 gage staples
3 - 8d common (63 mm x 3 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage
2 - 8d common (63 mm x 3 mm)
2 - 76 mm x 3 mm nails
3 - 76 mm 14 gage
3 - 8d common (63 mm x 3 mm)
toenail
toenail
face nail
400 mm o.c. along edge
toenail
toenail
face nail
face nail
toenail
face nail
face nail
3 - 8d common (63 mm x 3 mm)
face nail
16d (89 mm x 4 mm)
76 mm x 3 mm nails
76 mm 14 gage staples
20d common (101 mm x 5 mm) 812 mm o.c.
76 mm x 3 mm nails at 609 mm o.c.
76 mm 14 gage staples at 609 mm o.c.
609 mm o.c.
406 mm o.c.
406 mm o.c.
face nail at top and
bottom staggered
on opposite sides
2 - 20d common (101 mm x 5 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage staples
16d (89 mm x 4 mm)
3 - 10d common (76 mm x 3.7 mm)
4 - 76 mm x 3 mm nails
4 - 76 mm 14 gage staples
3 - 10d common (76 mm x 3.7 mm)
4 - 76 mm x 3 mm nails
4 - 76 mm 14 gage staples
face nail at ends and at
each splice
2 - 16d (89 mm x 4 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage staples
2 - 16d (89 mm x 4 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage staples
2 - 16d (89 mm x 4 mm)
3 - 76 mm x 3 mm nails
3 - 76 mm 14 gage staples
3 - 16d (89 mm x 4 mm)
at each bearing
face nail
toenail
face nail
toenail
face nail
face nail
426 / 496
30. Ledger strip
31. Wood structural panels and
b
particleboard
Subfloor, roof and wall sheathing
(to framing)
4 - 76 mm x 3 mm nails
4 - 76 mm 14 gage staples
3 - 16d (89 mm x 4 mm)
4 - 76 mm x 3 mm nails
4 - 76 mm 14 gage staples
c,1
6d
13 mm and less
n
60 mm x 3 mm nail
o
44 mm 16 gage
d
e
15 mm to 19 mm
8d or 6d
p
60 mm x 3 mm nail
o
50 mm 16 gage
c
22 mm to 25 mm
8d
d
e
d
e
28 mm to 31 mm
10d or 8d
19 mm and less
6d
e
Single floor (combination subfloorunderlayment to framing)
22 mm to 25 mm
8d
e
28 mm to 31 mm
10d or 8d
32. Panel siding (to framing)
13 mm or less 6df
15 mm
8df
h
12 mm No. 11 gage roofing nail
6d common nail (50 mm x 3 mm)
i
No. 16 gage staple
33. Fiberboard sheathingg
face nail at each joist
h
34. Interior paneling
20 mm No. 11 gage roofing nail
8d common nail (63 mm x 3 mm)
i
No. 16 gage staple
j
6 mm 4d
k
9 mm 6d
a. Common or box nails are permitted to be used except where otherwise stated.
b. Nails spaced at 150 mm on center at edges, 300 mm at intermediate supports except 150 mm at
supports where spans are 1200 mm or more. For nailing of wood structural panel and particleboard
diaphragms and shear walls, refer to Section 804. Nails for wall sheathing are permitted to be
common, box or casing.
c. Common or deformed shank (6d – 50 mm x 3 mm; 8d – 63 mm x 3 mm; 10d – 76 mm x 4 mm).
d. Common (6d – 50 mm x 3 mm; 8d – 63 mm x 3 mm; 10d – 76 mm x 4 mm).
e. Deformed shank (6d – 50 mm x 3 mm; 8d – 63 mm x 3 mm; 10d – 76 mm x 4 mm).
f. Corrosion-resistant siding (6d – 47 mm x 2.7 mm; 8d – 60 mm x 3.25 mm) or casing (6d – 50 mm x
2.5; 8d – 63 mm x 3 mm) nail.
g. Fasteners spaced 76 mm on center at exterior edges and 152 mm on center at intermediate
supports, when used as structural sheathing. Spacing shall be 152 mm on center on the edges and
304 mm on center at intermediate supports for nonstructural applications.
h. Corrosion-resistant roofing nails with 11 mm-diameter head and 39 mm length for 12.5 mm
sheathing and 44 mm length for 20 mm sheathing.
i. Corrosion-resistant staples with nominal 11 mm crown or 25 mm crown and 31 mm length for 12.5
mm sheathing and 39 mm length for 20 mm sheathing.
Panel supports at 406 mm (508 mm if strength axis in the long direction of the panel, unless
otherwisemarked).
j. Casing (39 mm x 2 mm) or finish (39 mm x 1.8 mm) nails spaced 152 mm on panel edges, 304 mm at
intermediate supports.
k. Panel supports at 609 mm. Casing or finish nails spaced 152 mm on panel edges, 304 mm at
intermediate supports.
l. For roof sheathing applications, 8d nails (63 mm x 3 mm) are the minimum required for wood
structural panels.
m.Staples shall have a minimum crown width of 11 mm.
All rights reserved
427 / 496
n. For roof sheathing applications, fasteners spaced 100 mm on center at edges, 200 mm at
intermediate supports.
o. Fasteners spaced 100 mm on center at edges, 200 mm at intermediate supports for subfloor
andwall sheathing and 76 mm on center at edges, 152 mm at intermediate supports for roof
sheathing.
p. Fasteners spaced 100 mm on center at edges, 200 mm at intermediate supports.
803.8.2 SHEATING FASTNERS
Sheathing nails or other approved sheathing connectors shall be driven so that their head or
crown is flush with the surface of the sheathing.
803.8.3 JOIST HANGERS AND FRAMING ANCHORS
Connections depending on joist hangers or framing anchors, ties and other mechanical
fastenings not otherwise covered are permitted where approved. The vertical load-bearing
capacity, torsional moment capacity and deflection characteristics of joist hangers shall be
determined in accordance with Chapter 3.
803.8.4 OTHER FASTENERS
Clips, staples, glues and other approved methods of fastening are permitted where approved.
803.8.5 FASTENERS AND CONNECTORS IN CONTACT
With preservative-treated and fire-retardant-treated wood. Fasteners and connectors in contact
with preservative-treated and fire-retardant-treated wood shall be in accordance with Sections
803.8.5. The coating weights for zinc-coated fasteners shall be in accordance with ASTM A 153
forces.
803.9 HEAVY TIMBER CONSTRUCTION
803.9.1 COLUMNS
Columns shall be continuous or super- imposed throughout all stories by means of reinforced
concrete or metal caps with brackets, or shall be connected by properly designed steel or iron
caps, with pintles and base plates, or by timber splice plates affixed to the columns by metal
connectors housed within the contact faces, or by other approved methods.
803.9.1.1 COLUMN CONNECTIONS
Girders and beams shall be closely fitted around columns and adjoining ends shall be cross
tied to each other, or intertied by caps or ties, to transfer horizontal loads across joints.
Wood bolsters shall not be placed on tops of columns unless the columns support roof loads
only.
803.9.2 FLOOR FRAMING
Approved wall plate boxes or hangers shall be provided where wood beams, girders or trusses
rest on masonry or concrete walls. Where intermediate beams are used to support a floor, they
shall rest on top of girders, or shall be supported by ledgers or blocks securely fastened to the
sides of the girders, or they shall be supported by an approved metal hanger into which the ends
of the beams shall be closely fitted.
803.9.3 ROOF FRAMING
Every roof girder and at least every alternate roof beam shall be anchored to its supporting
member; and every monitor and every sawtooth construction shall be anchored to the main
roof construction. Such anchors shall consist of steel or iron bolts of sufficient strength to resist
vertical uplift of the roof.
All rights reserved
428 / 496
803.9.4 FLOOR DECKS
Floor decks and covering shall not extend closer than 12.0 mm to walls. Such 12.7 mm spaces shall
be covered by a molding fastened to the wall either above or below the floor and arranged such
that the molding will not obstruct the expansion or contraction movements of the floor.
Corbeling of masonry walls under floors is permitted in place of such molding.
803.9.5 ROOF DECKS
Where supported by a wall, roof decks shall be anchored to walls to resist uplift forces
determined in accordance with Chapter 3. Such anchors shall consist of steel or iron bolts of
sufficient strength to resist vertical uplift of the roof.
803.10 PROTECTION AGAINST DECAY AND TERMITES
803.10.1 GENERAL
Where required by this section, protec- tion from decay and termites shall be provided by the use
of naturally durable or preservative-treated wood.
803.10.2 WOOD USED ABOVE GROUND
Wood used above ground in the locations specified in Sections 803.10.2.1 through 803.10.2.5
shall be naturally durable wood or preservative-treated wood using water-borne preservatives, in
accordance with AWPA U1 (Commodity Specifications A or F) for above-ground use.
803.10.2.1 JOISTS, GIRDERS AND SUBFLOOR
Where wood joists or the bottom of a wood structural floor without joists are closer than 450
mm, or wood girders are closer than 300 mm to the exposed ground in crawl spaces or
unexcavated areas located within the perim- eter of the building foundation, the floor
construction (including posts, girders, joists and subfloor) shall be of naturally durable or
preservative-treated wood.
803.10.2.2 WOOD SUPPORTED BY EXTERIOR FOUNDATION WALLS
Wood framing members, including wood sheathing, that rest on exterior foundation walls
and are less than 200 mm from exposed earth shall be of naturally durable or preservativetreated wood.
803.10.2.3 EXTERIOR WALLS BELOW GRADE
Wood framing members and furring strips attached directly to the interior of exterior
masonry or concrete walls below grade shall be of approved naturally durable or preservativetreated wood.
803.10.2.4 SLEEPERS AND SILLS
Sleepers and sills on a concrete or masonry slab that is in direct contact with earth shall be of
naturally durable or preservative-treated wood.
803.10.2.5 GIRDERS ENDS
The ends of wood girders entering exterior masonry or concrete walls shall be provided with
a 12.0 mm air space on top, sides and end, unless naturally durable or preservative-treated
wood is used.
803.10.3 WOOD IN CONTACT WITH THE GROUND OF FRESH WATER
Wood used in contact with the ground (exposed earth) in the locations specified in Sections
803.10.3.1 and 803.10.3.2 shall be naturally durable (species for both decay and termite
resistance) or preservative treated using water-borne preservatives in accordance with AWPA
U1 (Commodity Specifications A or F) for soil or fresh water use.
All rights reserved
429 / 496
Exception: Untreated wood is permitted where such wood is continuously and entirely below
the groundwater level or submerged in fresh water.
803.10.3.1 POSTS OR COLUMNS
Posts and columns supporting permanent structures that are embedded in concrete that is
in direct contact with the earth, embedded in concrete that is exposed to the weather or in
direct contact with the earth shall be of preservative-treated wood.
803.10.3.2 WOOD STRUCTURAL MEMBERS
Wood struc- tural members that support moisture-permeable floors or roofs that are exposed
to the weather, such as concrete or masonry slabs, shall be of naturally durable or
preservative-treated wood unless separated from such floors or roofs by an impervious
moisture barrier.
803.10.4 SUPPORTING MEMBERS FOR PERMANENT APPURTE-NANCES
Naturally durable or preservative-treated wood shall be utilized for those portions of wood
members that form the structural supports of buildings, balconies, porches or similar
permanent building appurtenances where such members are exposed to the weather
without adequate pro- tection from a roof, eave, overhang or other covering to prevent
moisture or water accumulation on the surface or at joints between members.
Exception: When a building is located in a geographical region where experience has
demonstrated that climatic conditions preclude the need to use durable materials where
the structure is exposed to the weather.
803.11 LONG-TERM LOADING
Wood members supporting concrete, masonry or similar materials shall be checked for the effects of
long-term loading using the provisions of the AF&PA NDS. The total deflection, including the effects of
long-term loading, shall be limited in accordance with Chapter 3 for these supported materials.
Exception: Horizontal wood members supporting masonry or concrete nonstructural floor or roof
surfacing not more than 100 mm thick need not be checked for long-term loading.
SECTION 804 GENERAL DESIGN REQUIREMENTS FOR LATERA-FORCE-RESISTING SYSTEMS
804.1 GENERAL
Structures using wood shear walls and diaphragms to resist wind, seismic and other lateral loads shall
be designed and constructed in accordance with AF&PA SDPWS and the provisions of Sections 803,
804 and 805.
804.1.1 OPENINGS IN SHEAR PANELS
Openings in shear panels that materially affect their strength shall be detailed on the plans,
and shall have their edges ade- quately reinforced to transfer all shearing stresses.
804.2 DIAPHRAGM DEFLECTIONS
The deflection (Δ) of a blocked wood structural panel diaphragm uniformly fastened throughout with
staples is permitted to be calculated by using the following equation. If not uniformly fastened, the
constant 1/1627 in the third term shall be modified accordingly.
Δ=(0.052vL3)/(EAb) + (vL)/(4GT) + Len /1627+ Σ(ΔcX)/(2b)
EQUATION 804.2-1
where:
2
A = Area of chord cross section, in mm .
B = Diaphragm width, in mm.
2
E = Elastic modulus of chords, in N/mm .
en = Staple deformation, in mm (see Table 804.2-1).
All rights reserved
430 / 496
Gt = Panel rigidity through the thickness, in N/mm of panel width or depth (see Table 804.2-1).
L = Diaphragm length, in mm.
v = Maximum shear due to design loads in the direction under consideration, in N/mm.
Δ = The calculated deflection, in inches (mm).
Σ(ΔcX) = Sum of individual chord-splice slip values on both sides of the diaphragm, each multiplied by
its distance to the nearest support
TABLE 804.2-1 en VALUES (mm) FOR USE IN CALCULATING DIAPHRAGM AND SHEAR WALL
DEFLECTION DUE TO FASTENER SLIP (Structural I)
a, c
FASTENER DESIGNATIONS
14-Ga staple x 50 mm long
3.80
5.50
8.5
12
16
21
b
LOAD PER FASTENER (N)
265
355
445
530
620
710
a. Increase en values 20 percent for plywood grades other than Structural I.
b. Load per fastener = maximum shear per foot divided by the number of fasteners per mm at interior
panel edges.
c. Decrease en values 50 percent for seasoned lumber (moisture content < 19 percent).
TABLE 804.2-2 VALUES OF Gt FOR USE IN CALCULATING DEFLECTION OF WOOD STRUCTURAL PANEL
SHEAR WALLS AND DIAPHRAGMS
OSB
13600
VALUES OF Gt (N/mm panel depth or width)
STRUCTURAL I
OTHER
5-ply
4-ply
3-ply
5-ply
4-ply
OSB
a
a
Plywood
Plywood Plywood
Plywood
Plywood
7200
7400
5700
13500
6500
5700
3-ply
Plywood
4400
SPAN
RATING
600/0
14600
7800
7900
6100
14600
7100
6100
4700
600/400
14600
7800
7900
6100
14600
7100
6100
4700
800/400
15500
8300
8400
6400
15500
7500
6400
5000
1000/500
16800
8900
9200
7100
16800
8100
7100
5400
1200/600
14600
7800
7900
6100
14600
7100
6100
4700
400 o. c.
15200
8000
8300
6400
15200
7300
6400
4900
500 o. c.
16200
8600
8800
6800
16200
7800
6800
5200
600 o. c.
19200
10400
10700
8200
19200
9400
8200
6300
810 o. c.
27100
14600
14900
11400
27100
13300
11400
8800
1200 o. c.
All Other Grades
Marine
4200
4400
4500
6600
6700
8500
8600
8800
8900
9200
12800
13100
5400
5700
5900
8600
8700
11100
11300
11400
11600
12000
16700
17000
A-A,
A-C
4200
4400
4500
6600
6700
8500
8600
8800
8900
9200
12800
13100
Thickness
mm
6,5
8,5
9,5
12
12,5
15
16
18
19
22
25,5
28,5
STRUCTURAL I
All Other Grades
Marine
5400
5700
5900
8600
8700
11100
11300
11400
11600
12000
16700
17000
5400
5700
5900
8600
8700
11100
11300
11400
11600
12000
16700
17000
All rights reserved
PANEL
TYPE
Sheathing
Single
Floor
OTHER
A-A,
A-C
5400
5700
5900
8600
8700
11100
11300
11400
11600
12000
16700
17000
Sanded
Plywood
431 / 496
804.3 SHEAR WALL DEFLECTION
The deflection (Δ) of a blocked wood structural panel shear wall uniformly fastened throughout with
staples is permitted to be calculated by the use of the following equation:
3
Δ ( vh )/(3EAb) + (vh)/(GT) + hen /407.6+ da(h)/(b)
EQUATION 804.3-1
where:
A = Area of boundary element cross section in square mm2 (vertical member at shear wall boundary).
b = Wall width, in mm.
da = Vertical elongation of overturning anchorage (including fastener slip, device elongation, anchor
rod elongation, etc.) at the design shear load (v).
E = Elastic modulus of boundary element (vertical member at shear wall boundary), in N/mm2.
en = Staple deformation, in mm (see Table 804.2-1).
Gt = Panel rigidity through the thickness, in N/mm of panel width or depth (see Table 804.2-2).
h = Wall height, in feet mm.
v = Maximum shear due to design loads at the top of the wall, in N/mm.
Δ = The calculated deflection, in mm.
SECTION 805 ALLOWABLE STRESS DESIGN
805.1 ALLOWABLE STRESS DESIGN
The structural analysis and construction of wood elements in structures using allowable stress design
shall be in accordance with the following applicable standards:
American Forest & Paper Association.
NDS NationalDesign Specification forWoodConstruction
SDPWS Special Design Provisions for Wind and Seismic
American Institute of Timber Construction.
AITC 104 Typical Construction Details
AITC 110 Standard Appearance Grades for Structural Glued Laminated Timber
AITC 113 Standard for Dimensions of Structural Glued Laminated Timber
AITC 117 Standard Specifications for Structural Glued Laminated Timber of Softwood Species
AITC 119 Standard Specifications for Structural Glued Laminated Timber of Hardwood Species
ANSI/ AITC A190.1 Structural Glued Laminated Timber
AITC 200 Inspection Manual
American Society of Agricultural Engineers.
ASAE EP 484.2 Diaphragm Design of Metal-clad, Post-Frame Rectangular Buildings
ASAE EP 486.1 Shallow Post Foundation Design
ASAE 559 Design Requirements and Bending Properties for Mechanically Laminated Columns
APA—The Engineered Wood Association.
Panel Design Specification
Plywood Design Specification Supplement 1 - Design & Fabrication of Plywood Curved Panel
Plywood Design Specification Supplement 2 - Design & Fabrication of Glued Plywood-lumber Beams
Plywood Design Specification Supplement 3 - Design & Fabrication of Plywood Stressed-skin Panels
Plywood Design Specification Supplement 4 - Design & Fabrication of Plywood Sandwich Panels
Plywood Design Specification Supplement 5 - Design & Fabrication of All-plywood Beams
EWS T300 Glulam Connection Details
EWS S560 Field Notching and Drilling of Glued Laminated Timber Beams
EWS S475 Glued Laminated Beam Design Tables
EWS X450 Glulam in Residential Construction
EWS X440 Product and Application Guide: Glulam
EWS R540 Builders Tips: Proper Storage and Handling of Glulam Beams
Truss Plate Institute, Inc.
TPI 1 National Design Standard for Metal Plate Connected Wood Truss Construction
All rights reserved
432 / 496
805.1.1 JOISTS AND RAFTERS
The design of rafter spans is permitted to be in accordance with the AF&PA Span Tables for Joists
and Rafters.
805.1.2 PLANK AND BEAM FLOORING
The design of plank and beam flooring is permitted to be in accordance with the AF&PA Wood
Construction Data No. 4.
805.1.3 TREATED WOOD STRESS ADJUSTMENT
The allowable unit stresses for preservative-treated wood need no adjustment for treatment,
but are subject to other adjustments.
The allowable unit stresses for fire-retardant-treated wood, including fastener values, shall be
developed from an approved method of investigation that considers the effects of anticipated
temperature and humidity to which the fire-retardant-treated wood will be subjected, the type
of treatment and the redrying process. Other adjustments are applicable except that the impact
load duration shall not apply.
805.2 WOOD DIAPHRAGMS
805.2.1 WOOD STRUCTURAL PANEL DIAPHRAGMS
Wood structural panel diaphragms shall be designed and con- structed in accordance with
AF&PA SDPWS.
805.2.2 SINGLE DIAGONALLY SHEATHED LUMBER DIAPHRAGMS
Single diagonally sheathed lumber diaphragms shall be designed and constructed in accordance
with AF&PA SDPWS.
805.2.3 DOUBLE DIAGONALLY SHEATHED LUMBER DIAPHRAGMS
Double diagonally sheathed lumber diaphragms shall be designed and constructed in accordance
with AF&PA SDPWS.
805.3 WOOD STRUCTURAL PANEL SHEAR WALLS
Wood structural panel shear walls shall be designed and constructed in accordance with AF&PA
SDPWS.
805.4 LUMBER SHEATHED SHEAR WALLS
Single and double diagonally sheathed lumber shear walls shall be designed and constructed in
accordance with AF&PA SDPWS. Single and double diagonally sheathed lumber walls shall not be used
to resist seismic forces in structures assigned to Seismic Design Category E or F.
805.5 PARTICLEBOARD SHEAR WALLS
Particleboard shear walls shall be designed and constructed in accordance with AF&PA SDPWS.
Particleboard shall not be used to resist seismic forces in structures assigned to Seismic Design Category
D, E or F.
SECTION 806 LOAD RESISTANCE FACTOR DESIGN
806.1 LOAD AND RESISTANCE FACTOR DESIGN
The structural analysis and construction of wood elements and structures using load and resistance
factor design shall be in accordance with AF&PA NDS and AF&PA SDPWS.
All rights reserved
433 / 496
806.1.1 WOOD STRUCTURAL PANEL SHEAR WALLS
In Seismic Design Category D, E or F, where shear design values exceed 7000 N/m, all framing
members receiving edge nailing from abutting panels shall not be less than a single 80 mm
nominal member or two 50 mm nominal members fastened together in accordance with
AF&PA NDS to transfer the design shear value between framing members. Wood structural
panel joint and sill plate nailing shall be staggered at all panel edges. See Sections 4.3.6.1 and
4.3.6.4.3 of AF&PA SDPWS for sill plate size and anchorage requirements.
Note: Space panel end and edge joint 3 mm. Reduce spacing between lines of nails as necessary to
maintain minimum 9.5 mm fastener edge margins, minimum spacing between lines is 9.5 mm.
All rights reserved
434 / 496
CHAPTER 9
STRUCTURAL TESTS & EVALUATION OF EXISTING STRUCTURES
SECTION 901 GENERAL
901.1 SCOPE
The provisions of this chapter shall govern the quality, workmanship and requirements for materials
covered. Materials of construction and tests shall conform to the applicable standards listed in this
code.
901.2 NEW MATERIALS
New building materials, equipment, appliances, systems or methods of construction not provided for
in this code, and any material of questioned suitability proposed for use in the construction of a building
or structure, shall be subjected to the tests prescribed in this chapter and in the approved rules to
determine character, quality and limitations of use.
901.3 USED MATERIALS
The use of second-hand materials that meet the minimum requirements of this code for new materials
shall be permitted.
SECTION 902 APPROVALS
902.1 APPROVED AGENCY
An approved agency shall provide all information as necessary for the building official to determine
that the agency meets the applicable requirements.
902.1.1 INDEPENDENCE
An approved agency shall be objective, competent and independent from the contractor
responsible for the work being inspected. The agency shall also disclose possible conflicts of
interest so that objectivity can be confirmed.
902.1.2 EQUIPMENT
An approved agency shall have adequate equipment to perform required tests. The equipment
shall be periodically calibrated.
902.1.3 PERSONNEL
An approved agency shall employ experienced personnel educated in conducting, supervising
and evaluating tests and/or inspections.
902.2 WRITTEN APPROVAL
Any material, appliance, equipment, system or method of construction meeting the requirements of
this code shall be approved in writing after satisfactory completion of the required tests and
submission of required test reports.
902.3 APPROVED RECORD
For any material, appliance, equipment, system or method of construction that has been approved,
a record of such approval, including the conditions and limitations of the approval, shall be kept on file in
the building official’s office and shall be open to public inspection at appropriate times.
902.4 PERFORMANCE
Specific information consisting of test reports conducted by an approved testing agency shall be
provided for the building official to determine that the material meets the applicable code
requirements.
All rights reserved
435 / 496
902.4.1 RESEARCH AND INVESTIGATION
Sufficient technical data shall be submitted to the building official to substantiate the proposed
use of any material or assembly. If it is determined that the evidence submitted is satisfactory
proof of performance for the use intended, the building official shall approve the use of the
material or assembly subject to the requirements of this code. The costs, reports and
investigations required under these provisions shall be paid by the applicant.
902.4.2 RESEARCH REPORTS
Supporting data, where necessary to assist in the approval of materials or assemblies not
specifically provided for in this code, shall consist of valid research reports from approved
sources.
902.5 LABELING
Where materials or assemblies are required by this code to be labeled, such materials and assemblies
shall be labeled by an approved agency in accordance with Section 902. Products and materials
required to be labeled shall be labeled in accordance with the procedures set forth in Section 902.5.
902.5.1 TESTING
An approved agency shall test a representative sample of the product or material being labeled to
the relevant standard or standards. The approved agency shall maintain a record of the tests
performed. The record shall provide sufficient detail to verify compliance with the test standard.
902.5.2 INSPECTION AND IDENTIFICATION
The approved agency shall periodically perform an inspection, which shall be in-plant if
necessary, of the product or material that is to be labeled. The inspection shall verify that the
labeled product or material is representative of the product or material tested.
902.5.3 LABEL INFORMATION
The label shall contain the manufacturer’s or distributor’s identification, model number, serial
number or definitive information describing the product or material’s performance
characteristics and approved agency’s identification.
902.6 EVALUATION AND FOLLOW-UP INSPECTION SERVICES
Where structural components or other items regulated by this code are not visible for inspection after
completion of a prefabricated assembly, the applicant shall submit a report of each prefabricated
assembly. The report shall indicate the complete details of the assembly, including a description of the
assembly and its components, the basis upon which the assembly is being evaluated, test results and
similar information and other data as necessary for the building official to determine conformance to
this code. Such a report shall be approved by the building official.
902.6.1 FOLLOW-UP INSPECTION
The applicant shall provide for special inspections of fabricated items in accordance with Section
903.2.
902.6.2 TEST AND INSPECTION RECORDS
Copies of necessary test and inspection records shall be filed with the building official.
SECTION 903 SPECIAL INSPECTIONS
903.1 GENERAL
Where application is made for construction as described in this section, the owner or the registered
design professional in responsible charge acting as the owner’s agent shall employ one or more
approved agencies to perform inspections during construction on the types of work listed under
All rights reserved
436 / 496
Section 903. The special inspector shall be a qualified person who shall demonstrate competence, to
the satisfaction of the building official, for the inspection of the particular type of construction or
operation requiring special inspection. The registered design professional in responsible charge and
engineers of record involved in the design of the project are permitted to act as the approved agency
and their personnel are permitted to act as the special inspector for the work designed.
The special inspector shall be a qualified person who shall demonstrate competence, to the
satisfaction of the building official, for the inspection of the particular type of construction or
operation requiring special inspection. The registered design professional in responsible charge and
engineers of record involved in the design of the project are permitted to act as the approved agency
and their personnel are permitted to act as the special inspector for the work designed by them,
provided those personnel meet the qualification requirements of this section to the satisfaction of the
building official. The special inspector shall provide written documentation to the building official
demonstrating his or her competence and relevant experience or training. Experience or training shall
be considered relevant when the documented experience or training is related in complexity to the
same type of special inspection activities for projects of similar complexity and material qualities.
These qualifications are in addition to qualifications specified in other sections of this code.
Exceptions:
1. Special inspections are not required for work of a minor nature or as warranted by conditions in the
jurisdiction as approved by the building official.
2. Special inspections are not required for building components unless the design involves the practice
of professional engineering or architecture as defined by applicable state statutes and regulations
governing the professional registration and certification of engineers or architects.
3. Unless otherwise required by the building official, special inspections are not required for Group U
occupancies that are accessory to a residential occupancy including, but not limited to, those listed
in AAC (Afghan Architecture Code).
903.2 INSPECTION OF FABRICATORS
Where fabrication of structural load-bearing members and assemblies is being performed on the
premises of a fabricator’s shop, special inspection of the fabricated items shall be required by this
section and as required elsewhere in this code.
903.3 STEEL CONSTRUCTION
The special inspections for steel elements of buildings and structures shall be as required by this
section.
Exceptions:
1. Special inspection of the steel fabrication process shall not be required where the fabricator does
not perform any welding, thermal cutting or heating operation of any kind as part of the fabrication
process. In such cases, the fabricator shall be required to submit a detailed procedure for material
control that demonstrates the fabricator’s ability to maintain suitable records and procedures such
that, at any time during the fabrication process, the material specification, grade and mill test
reports for the main stress-carrying elements are capable of being determined.
2. The special inspector need not be continuously present during welding of the following items,
provided the materials, welding procedures and qualifications of welders are verified prior to the
start of the work; periodic inspections are made of the work in progress and a visual inspection of
all welds is made prior to completion or prior to shipment of shop welding.
903.3.1 WELDING
Welding inspection and welding inspector qualification shall be in accordance with this section.
All rights reserved
437 / 496
TABLE 903.3.1-1 REQUIRED VERIFICATION AND INSPECTION OF STEEL CONSTRUCTION
VERIFICATION AND INSPECTION
PERIODIC
REFERENCED
a
STANDARD
-
x
AISC 360, Section A3.3
and applicable ASTM
material standards
-
x
-
-
x
AISC 360, Section M2.5
-
-
x
-
-
x
-
X
-
X
-
X
-
x
X
-
X
X
X
-
X
X
X
X
-
x
x
-
x
-
x
-
x
x
x
CONTINUOUS
1. Material verification of high-strength bolts, nuts and
washers:
a.Identification markings to conform to ASTM
standards specified in the approved construction
documents.
b.Manufacturer’s certificate of compliance
required.
2. Inspection of high-strength bolting:
a.Snug-tight joints.
b.Pretensioned and slip-critical joints using
turn-of-nut with matchmarking, twist-off bolt or
direct tension indicator methods of installation.
c.Pretensioned and slip-critical joints using
turn-of-nut without matchmarking or calibrated
wrench methods of installation.
3. Material verification of structural steel and
cold-formed steel deck:
a.For structural steel, identification markings to
conform to AISC 360.
b. For other steel, identification markings to
conform to ASTM standards specified in the
approved construction documents.
c.Manufacturer’s certified test reports.
4. Material verification of weld filler materials:
a.Identification markings to conform to AWS
specification in the approved construction
documents.
b.Manufacturer’s certificate of compliance
required.
5. Inspection of welding:
a.Structural steel and cold-formed steel deck:
1) Complete and partial joint penetration groove
welds.
2) Multipass fillet welds.
3) Single-pass fillet welds > 8 mm
4) Plug and slot welds.
5) Single-pass fillet welds ≤ 8 mm
6) Floor and roof deck welds.
b.Reinforcing steel:
1) Verification of weldability of reinforcing steel
other than ASTM A 706.
2) Reinforcing steel resisting flexural and axial
forces in intermediate and special moment
frames, and boundary elements of special
structural walls of concrete and shear
reinforcement.
3) Shear reinforcement.
4) Other reinforcing steel.
6. Inspection of steel frame joint details for compliance:
a. Details such as bracing and stiffening.
b. Member locations.
c. Application of joint details at each connection.
ASC
REFERENCE
-
903.3.3
AISC 360, Section M5.5
Applicable ASTM
material standards
AISC 360, Section A3.5
and applicable AWS
A5 documents
-
-
AWS D1.1
903.3.1
-
AWS D1.3
AWS D1.4 ACI 318:
Section 3.5.2
-
903.3.2
a. Where applicable, see also Section 906.1, Special inspection for seismic resistance.
903.3.2 DETAILS.
The special inspector shall perform an inspection of the steel frame to verify compliance with
the details shown on the approved construction documents, such as bracing, stiffening, member
locations and proper application of joint details at each connection.
All rights reserved
438 / 496
903.3.3 HIGH-STRENGTH BOLTS
Installation of high-strength bolts shall be inspected in accordance with AISC 360.
903.4 CONCRETE CONSTRUCTION
The special inspections and verifications for concrete construction shall be as required by this section.
Exception: Special inspections shall not be required for:
1. Isolated spread concrete footings of buildings three stories or less above grade plane that are fully
supported on earth or rock.
2. Continuous concrete footings supporting walls of buildings three stories or less above grade
plane that are fully supported on earth or rock where:
2.1. The footings support walls of light-frame construction;
2.2. The footings are designed in accordance with Section 408; or
2.3. The structural design of the footing is b ased on a specified compressive strength , fc no
greater than 17.0 MPa, regardless of the compressive strength specified in the construction
documents or used in the footing construction.
3. Nonstructural concrete slabs supported directly on the ground, including prestressed slabs on
grade, where the effective prestress in the concrete is less than 1.00 MPa.
4. Concrete foundation walls constructed in accordance with Section 406.
5. Concrete patios, driveways and sidewalks, on grade.
TABLE 903.4-1 REQUIRED VERIFICATION AND INSPECTION OF CONCRETE CONSTRUCTION
VERIFICATION AND INSPECTION
1. Inspection of reinforcing steel, including
prestressing tendons, and placement.
2. Inspection of reinforcing steel welding
in accordance with Table 903.3.1-1, Item
5b.
3. Inspection of bolts to be installed in
concrete prior to and during placement of
concrete where allowable loads have been
increased or where strength design is
used.
4. Inspection of anchors installed in
hardened concrete.
5. Verifying use of required design mix.
6. At the time fresh concrete is sampled to
fabricate specimens for strength tests,
perform slump and air content tests, and
determine the temperature of the
concrete.
7. Inspection of concrete and shotcrete
placement for proper application
techniques.
8. Inspection for maintenance of specified
curing temperature and techniques.
9. Inspection of prestressed concrete:
a.Application of prestressing forces.
b.Grouting of bonded prestressing
tendons in the seismic-force-resisting
system.
10. Erection of precast concrete members.
11. Verification of in-situ concrete
strength, prior to stressing of tendons in
All rights reserved
CONTINUOUS
PERIODIC
REFERENCED
a
STANDARD
ASC REFERENCE
-
x
-
511.5, 506
x
-
AWS D1.4
511.5.2
x
-
ACI 318:
21.2.8
512.1.3
-
x
ACI 318:
3.8.6, 8.1.3,
21.2.8
1912.1
-
x
x
-
ASTM C 172
ASTM C 31
504.6, 504.8
x
-
-
504.9, 504.10
-
x
-
504.11-504.13
X
x
-
ACI 318: 18.20
ACI 318:
18.18.4
-
-
x
-
520
-
x
-
505.2
Ch 5, 504.2-504.4
439 / 496
posttensioned concrete and prior to
removal of shores and forms from beams
and structural slabs.
12. Inspect formwork for shape, location
and dimensions of the concrete member
being formed.
-
x
-
505.1.1
a. Where applicable, see also Section 906.1, Special inspection for seismic resistance.
903.4 MATERIALS
In the absence of sufficient data or documentation providing evidence of conformance to quality
standards for materials in Section 511, the building official shall require testing of materials in
accordance with the appropriate standards and criteria for the material in Section 511.
903.5 MASONRY CONSTRUCTION
Masonry construction shall be inspected and verified in accordance with the requirements of Section
903.5, depending on the occupancy category of the building or structure.
Exception: Special inspections shall not be required for:
1. Empirically designed masonry, glass unit masonry or masonry veneer designed by Section 709, or by
Chapter 5, 6 or 7 of TMS 402/ACI 530/ASCE 5, respectively, when they are part of structures
classified as Occupancy Category I, II or III in accordance with Section 301.6.
2. Masonry foundation walls constructed in accordance with Table 406.2.3-2, 406.2.3-3, 406.2.3-4 or
406.2.3-5.
3. Masonry fireplaces, masonry heaters or masonry chimneys installed or constructed in accordance
with Section 710, respectively.
TABLE 903.5-1 LEVEL 1 REQUIRED VERIFICATION AND INSPECTION OF MASONRY CONSTRUCTION
VERIFICATION AND INSPECTION
FREQUENCY OF
INSPECTION
CONTINUOUS
PERIODIC
REFERENCE FOR CRITERIA
ASC
SECTION
TMS 402/ACI
a
530/ASCE 5
1. Compliance with required
inspection provisions of the
construction documents and
x
the approved submittals shall be
verified.
2. Verification of f΄m and f'AAC
prior to construction except
x
where specifically exempted by
this code.
3. Verification of slump flow and
VSI as delivered to the site for
x
self-consolidating
grout.
4. As masonry construction begins, the following shall be verified to ensure compliance:
a. Proportions of site-prepared
x
mortar.
b. Construction of mortar joints.
x
c. Location of reinforcement,
connectors, prestressing
x
tendons and anchorages.
d. Prestressing technique.
x
e. Grade and size of prestressing
x
tendons and anchorages.
5. During construction the inspection program shall verify:
All rights reserved
TMS 602/ACI
a
530.1/ASCE 6
Art. 1.5
Art. 1.4B
Art. 1.5B.1.b.3
Art. 2.6A
Art. 3.3B
Art. 3.4, 3.6A
Art. 3.6B
Art. 2.4B, 2.4H
440 / 496
a. Size and location of structural
elements.
b. Type, size and location of
anchors, including other details
of anchorage of masonry to
structural members, frames or
other construction.
c. Specified size, grade and type
of reinforcement, anchor bolts,
prestressing tendons and
anchorages.
d. Welding of reinforcing bars.
-
x
-
-
Art. 3.3F
-
x
-
Sec. 1.2.2(e),
1.16.1
-
-
x
-
Sec. 1.15
Art. 2.4, 3.4
x
-
-
Sec. 2.1.9.7.2,
3.3.3.4(b)
-
-
Art. 1.8C,
1.8D
-
Art. 3.6B
-
Art. 3.2D
Sec. 1.13
Art. 3.4
-
Art. 2.6B
-
Art. 3.3B
-
Art. 3.5
-
Art. 3.6C
-
Art. 1.4
e. Preparation, construction and
protection of masonry during
cold weather (temperature
Sec. 704.3,
x
below 4°C)
704.4
or hot weather (temperature
above 32°C).
f. Application and measurement
x
of prestressing force.
6. Prior to grouting, the following shall be verified to ensure compliance:
a. Grout space is clean.
x
b. Placement of reinforcement
and connectors, and
x
prestressing tendons and
anchorages.
c. Proportions of site-prepared
grout and prestressing rout for
x
bonded tendons.
d. Construction of mortar joints.
x
7. Grout placement shall be
x
verified to ensure compliance:
a. Grouting of prestressing
x
bonded tendons.
8. Preparation of any required
grout specimens, mortar
x
Sec. 705.3
specimens and/or prisms shall
be observed.
a. The specific standards referenced.
903.5.1 ENGINEERED MASONRY IN OCCUPANCY CATEGORY I, II OR III
The minimum special inspection program for masonry designed by Section 707 or 708 or by
chapters other than Chapter 5, 6 or 7 of TMS 402/ACI 530 in structures classified as Occupancy
Category I, II or III, in accordance with Section 301.6, shall comply with Table 903.5-1.
903.5.2 ENGINEERED MASONRY IN OCCUPANCY CATEGORY IV
The minimum special inspection program for masonry designed by Section 707 or 708 or by
chapters other than Chapter 5, 6 or 7 of TMS 402/ACI 530/ASCE 5 in structures classified as
Occupancy Category IV, in accordance with Section 301.6, shall comply with Table 903.5.2-1.
All rights reserved
441 / 496
TABLE 903.5.2-1 LEVEL 2 REQUIRED VERIFICATION AND INSPECTION OF MASONRY CONSTRUCTION
VERIFICATION AND INSPECTION
1. Compliance with required inspection
provisions of the construction documents
and the approved submittals.
2. Verification of f'm and f'AAC prior to
2
construction and for every 465 m during
construction.
3. Verification of proportions of materials in
premixed or preblended mortar and grout as
delivered to the site.
4. Verification of slump flow and VSI as
delivered to the site for self-consolidating
grout.
5. The following shall be verified to ensure
compliance:
a. Proportions of site-prepared mortar,
grout and prestressing grout for bonded
tendons.
b. Placement of masonry units and
construction of mortar joints.
c. Placement of reinforcement, connectors
and prestressing tendons and anchorages.
d. Grout space prior to grout.
e. Placement of grout.
f. Placement of prestressing grout.
g. Size and location of structural elements.
h. Type, size and location of anchors,
including other details of anchorage of
masonry to structural members, frames
or other construction.
i. Specified size, grade and type of
reinforcement, anchor bolts, prestressing
tendons and anchorages.
j. Welding of reinforcing bars.
k. Preparation, construction and protection
of masonry during cold weather
(temperature below 4°C) or hot
weather (temperature above 32°C).
l. Application and measurement of
prestressing force.
6. Preparation of any required grout
specimens and/or prisms shall be observed.
REFERENCE FOR CRITERIA
TMS 402/ACI
TMS 602/ACI
a
a
530/ASCE 5
530.1/ASCE 6
CONTINUOUS
PERIODIC
ASC
SECTION
-
X
-
-
Art. 1.5
-
X
-
-
Art. 1.4B
-
X
-
-
Art. 1.5B
x
-
-
-
Art. 1.5B.1.b.3
-
x
-
-
Art. 2.6A
-
x
-
-
Art. 3.3B
-
x
-
Sec. 1.15
Art. 3.4, 3.6A
x
x
x
-
x
-
-
Art. 3.2D
Art. 3.5
Art. 3.6C
Art. 3.3F
x
-
-
Sec.1.2.2(e),
1.16.1
-
-
x
-
Sec. 1.15
Art. 2.4, 3.4
x
-
-
Sec. 2.1.9.7.2,
3.3.3.4 (b)
-
-
x
Sec.
704.3,
704.4
-
Art. 1.8C, 1.8D
x
-
-
-
Art. 3.6B
x
-
Sec.
705.2.2,
705.3
-
Art. 1.4
a. The specific standards referenced.
903.6 WOOD CONSTRUCTION
Special inspections of site-built assemblies shall be in accordance with this section.
903.7 SOILS
Special inspections for existing site soil conditions, fill placement and load-bearing requirements shall
be as required by this section and Table 903.7-1. The approved geotechnical report, and the
construction documents prepared by the registered design professionals shall be used to determine
compliance. During fill placement, the special inspector shall determine that proper materials and
procedures are used in accordance with the provisions of the approved geotechnical report.
All rights reserved
442 / 496
Exception: Where Section 402 does not require reporting of materials and procedures for fill
placement, the special inspector shall verify that the in-place dry density of the compacted fill is not
less than 90 percent of the maximum dry density at optimum moisture content determined in
accordance with referred standard.
TABLE 903.7-1 REQUIRED VERIFICATION AND INSPECTION OF SOILS
VERIFICATION AND INSPECTION TASK
1. Verify materials below shallow foundations are adequate to achieve
the design bearing capacity.
2. Verify excavations are extended to proper depth and have reached
proper material.
3. Perform classification and testing of compacted fill materials.
4. Verify use of proper materials, densities and lift thicknesses during
placement and compaction of compacted fill.
5. Prior to placement of compacted fill, observe subgrade and verify that
site has been prepared properly.
CONTINUOUS
DURING TASK LISTED
PERIODICALLY
DURING TASK LISTED
-
x
-
x
-
x
x
-
-
x
903.8 DRIVEN DEEP FOUNDATIONS
Special inspections shall be performed during installation and testing of driven deep foundation
elements as required by Table 903.8-1. The approved geotechnical report, and the construction
documents prepared by the registered design professionals, shall be used to determine compliance.
TABLE 903.8-1 REQUIRED VERIFICATION AND INSPECTION OF DRIVEN DEEP FOUNDATION ELEMENTS
VERIFICATION AND INSPECTION TASK
1. Verify element materials, sizes and lengths comply with the
requirements.
2. Determine capacities of test elements and conduct additional load
tests, as required.
3. Observe driving operations and maintain complete and accurate
records for each element.
4. Verify placement locations and plumbness, confirm type and size of
hammer, record number of blows per foot of penetration, determine
required penetrations to achieve design capacity, record tip and butt
elevations and document any damage to foundation element.
5. For steel elements, perform additional inspections in accordance with
Section 903.3.
6. For concrete elements and concrete-filled elements, perform additional
inspections in accordance with Section 903.4.
7. For specialty elements, perform additional inspections as determined
by the registered design professional in responsible charge.
CONTINUOUS
DURING TASK LISTED
PERIODICALLY
DURING TASK LISTED
x
-
x
-
x
-
x
-
-
-
-
-
-
-
903.9 CAST-IN-PLACE DEEP FOUNDATIONS
Special inspections shall be performed during installation and testing of cast-in-place deep
foundation elements as required by Table 903.9-1. The approved geotechnical report, and the
construction documents prepared by the registered design professionals, shall be used to determine
compliance.
All rights reserved
443 / 496
TABLE 903.9-1 REQUIRED VERIFICATION AND INSPECTION OF CAST-IN-PLACE DEEP FOUNDATION
ELEMENTS
VERIFICATION AND INSPECTION TASK
1. Observe drilling operations and maintain complete and accurate
records for each element.
2. Verify placement locations and plumbness, confirm element diameters,
bell diameters (if applicable), lengths, embedment into bedrock (if
applicable) and adequate end-bearing strata capacity. Record concrete or
grout volumes.
3. For concrete elements, perform additional inspections in accordance
with Section 903.4.
CONTINUOUS
DURING TASK LISTED
PERIODICALLY
DURING TASK LISTED
x
-
x
-
-
-
903.10 HELICAL PILE FOUNDATIONS
Special inspections shall be performed continuously during installation of helical pile foundations. The
information recorded shall include installation equipment used, pile dimensions, tip elevations, final
depth, final installation torque and other pertinent installation data as required by the registered
design professional in responsible charge. The approved geotechnical report and the construction
documents prepared by the registered design professional shall be used to determine compliance.
903.11 VERTICAL MASONRY FOUNDATION ELEMENTS
Special inspection shall be performed in accordance with Section 903.5 for vertical masonry
foundation elements.
903.12 SPRAYED FIRE-RESISTANT MATERIALS
Special inspections for sprayed fire-resistant materials applied to floor, roof and wall assemblies and
structural members shall be in accordance with Sections 903.12.1 through 903.12.6. Special
inspections shall be based on the fire-resistance design as designated in the approved construction
documents.
903.12.1 PHYSICAL AND VISUAL TESTS
The special inspections shall include the following tests and observations to demonstrate
compliance with the listing and the fire-resistance rating:
1. Condition of substrates.
2. Thickness of application.
3. Density in kg/m3.
4. Bond strength adhesion/cohesion.
5. Condition of finished application.
903.12.2 STRUCTURAL MEMBER SURFACE CONDITIONS
The surfaces shall be prepared in accordance with the approved fire-resistance design and
the written instructions of approved manufacturers. The prepared surface of structural
members to be sprayed shall be inspected before the application of the sprayed fireresistant material.
903.12.3 APPLICATION
The substrate shall have a minimum ambient temperature before and after application as
specified in the written instructions of approved manufacturers. The area for application
shall be ventilated during and after application as required by the written instructions of
approved manufacturers.
903.12.4 THICKNESS
No more than 10 percent of the thickness measurements of the sprayed fire-resistant
materials applied to floor, roof and wall assemblies and structural members shall be less
All rights reserved
444 / 496
than the thickness required by the approved fire-resistance design, but in no case less than
the minimum allowable thickness required by Section 903.12.4.1.
903.12.4.1 MINIMUM ALLOWABLE THICKNESS
For design thicknesses 25 mm or greater, the minimum allowable individual thickness
shall be the design thickness minus 6.4 mm. For design thicknesses less than 25 mm, the
minimum allowable individual thickness shall be the design thickness minus 25 percent.
Thickness shall be determined in accordance with ASTM E 605. Samples of the sprayed
fire-resistant materials shall be selected in accordance with Sections 903.12.4.2 and
903.12.4.3.
903.12.4.2 FLOOR, ROOF AND WALL ASSEMBLIES
The thickness of the sprayed fire-resistant material applied to floor, roof and wall
assemblies shall be determined in accordance with ASTM E 605, making not less than
four measurements for each 90 m2 of the sprayed area in each story or portion thereof.
903.12.4.2.1 CELLULAR DECKS
Thickness measurements shall be selected from a square area, 300 mm by 300 mm
in size. A minimum of four measurements shall be made, located symmetrically
within the square area.
903.12.4.2.2 FLUTED DECKS
Thickness measurements shall be selected from a square area, 300 mm by 300 mm
in size. A minimum of four measurements shall be made, located symmetrically
within the square area, including one each of the following: valley, crest and sides.
The average of the measurements shall be reported.
903.12.4.3 STRUCTURAL MEMBERS
The thickness of the sprayed fire-resistant material applied to structuralmembers shall be
determined in accordance with ASTM E 605. Thickness testing shall be performed on not less
than 25 percent of the structural members on each floor.
903.12.4.3.1 BEAMS AND GRIDERS
At beams and girders thickness measurements shall be made at nine locations around
the beam or girder at each end of a 300 mm length.
903.12.4.3.2 JOISTS AND TRUSSES
At joists and trusses, thickness measurements shall be made at seven locations around
the joist or truss at each end of a 300 mm length.
903.12.4.3.3 WIDE-FLANGED COLUMNS
At wide-flanged columns, thickness measurements shall be made at 12 locations around
the column at each end of a 300 mm length.
903.12.4.3.4 HOLLOW STRUCTURAL SECTION AND PIPE
At hollow structural section and pipe columns, thickness measurements shall be made at
a minimum of four locations around the column at each end of a 300 mm length.
903.12.5 DENSITY
The density of the sprayed fire-resistant material shall not be less than the density specified
in the approved fire-resistance design. Density of the sprayed fire-resistant material shall be
determined in accordance with ASTM E 605. The test samples for determining the density of
the sprayed fire-resistant materials shall be selected as follows:
All rights reserved
445 / 496
1. From each floor, roof and wall assembly at the rate of not less than one sample for every
230 m2 or portion thereof of the sprayed area in each story.
2. From beams, girders, trusses and columns at the rate of not less than one sample for each
type of structural member for each 230 m2 of floor area or portion thereof in each story.
903.12.6 BOND STRENGTH
The cohesive/adhesive bond strength of the cured sprayed fire-resistant material applied to
floor, roof and wall assemblies and structural members shall not be less than 7.00 kN/m2.
The cohesive/adhesive bond strength shall be determined in accordance with the field test
specified in ASTM E 736 by testing in-place samples of the sprayed fire-resistant material
selected in accordance with Sections 903.12.6.1 through 903.12.6.3.
903.12.6.1 FLOOR, ROOF AND WALL ASSEMBLIES
The test samples for determining the cohesive/adhesive bond strength of the sprayed
fire-resistant materials shall be selected from each floor, roof and wall assembly at the
rate of not less than one sample for every 230 m2 of the sprayed area in each story or
portion thereof.
903.12.6.2 STRUCTURAL MEMBERS
The test samples for determining the cohesive/adhesive bond strength of the sprayed
fire-resistant materials shall be selected from beams, girders, trusses, columns and other
structural members at the rate of not less than one sample for each type of structural
member for each 230 m2 of floor area or portion thereof in each story.
903.12.6.3 PRIMER, PAINT AND ENCAPSULANT BOND TESTS
Bond tests to qualify a primer, paint or encapsulant shall be conducted when the
sprayed fire-resistant material is applied to a primed, painted or encapsulated surface
for which acceptable bond-strength performance between these coatings and the fireresistant material has not been determined. A bonding agent approved by the SFRM
manufacturer shall be applied to a primed, painted or encapsulated surface where the
bond strengths are found to be less than required values.
SECTION 904 STATEMENT OF SPECIAL INSPECTIONS
904.1 GENERAL
Where special inspection or testing is required by Section 903, 906 or 907, the registered design
professional in responsible charge shall prepare a statement of special inspections in accordance with
Section 904.
904.2 CONTENT OF STATEMENT OF SPECIAL INSPECTIONS
The statement of special inspections shall identify the following:
1. The materials, systems, components and work required to have special inspection or testing by the
building official or by the registered design professional responsible for each portion of the work.
2. The type and extent of each special inspection.
3. The type and extent of each test.
4. Additional requirements for special inspection or testing for seismic or wind resistance as specified
in Section 904.3, 904.4, 906 or 907.
5. For each type of special inspection, identification as to whether it will be continuous special
inspection or periodic special inspection.
904.3 SEISMIC RESISTANCE
The statement of special inspections shall include seismic requirements for cases covered in Sections
904.3.1 through 904.3.5.
All rights reserved
446 / 496
Exception: Seismic requirements are permitted to be excluded from the statement of special
inspections for structures designed and constructed in accordance with the following:
1. The structure consists of light-frame construction; the design spectral response acceleration at short
periods, SDS, as determined in Section 311.4.4, does not exceed 0.5g; and the height of the structure
does not exceed 10 600 mm) above grade plane; or
2. The structure is constructed using a reinforced masonry structural system or reinforced concrete
structural system; the design spectral response acceleration at short periods, SDS, as determined in
Section 311.4.4, does not exceed 0.5g, and the height of the structure does not exceed 7600 mm
above grade plane; or
3. Detached one-or two-family dwellings not exceeding two stories above grade plane, provided the
structure does not have any of the following plan or vertical irregularities in accordance with
Section 311.6.3.2:
3.1. Torsional irregularity.
3.2. Nonparallel systems.
3.3. Stiffness irregularity—extreme soft story and soft story.
3.4. Discontinuity in capacity—weak story.
904.3.1 SEISMIC-FORCE-RESISTING SYSTEMS
The seismicforce-resisting systems in structures assigned to Seismic Design Category C, D, E or F,
in accordance with Section 311.
Exception: Requirements for the seismic-force-resisting system are permitted to be excluded
from the statement of special inspections for steel systems in structures assigned to Seismic
Design Category C that are not specifically detailed for seismic resistance, with a response
modification coefficient, R, of 3 or less, excluding cantilever column systems.
904.3.2 DESIGNATED SEISMIC SYSTEMS
Designated seismic systems in structures assigned to Seismic Design Category D, E or F.
904.3.3 SEISMIC DESIGN CATEGORY C
The following additional systems and components in structures assigned to Seismic Design
Category C:
1. Heating, ventilating and air-conditioning (HVAC) ductwork containing hazardous materials and
anchorage of such ductwork.
2. Piping systems and mechanical units containing flammable, combustible or highly toxic
materials.
3. Anchorage of electrical equipment used for emergency or standby power systems.
904.3.4 SEISMIC DESIGN CATEGORY D
The following additional systems and components in structures assigned to Seismic Design
Category D:
1. Systems required for Seismic Design Category C.
2. Exterior wall panels and their anchorage.
3. Suspended ceiling systems and their anchorage.
4. Access floors and their anchorage.
5. Steel storage racks and their anchorage, where the importance factor is equal to 1.5.
904.3.5 SEISMIC DESIGN CATEGORY E OR F
The following additional systems and components in structures assigned to Seismic Design
Category E or F:
1. Systems required for Seismic Design Categories C and D.
2. Electrical equipment.
All rights reserved
447 / 496
904.3.6 SEISMIC REQUIREMENTS IN THE STATEMENT OF SPECIAL INSPECTIONS
The statement of special inspections shall identify the following:
1. The designated seismic systems and seismic-force-resisting systems that are subject to
special inspections in accordance with Sections 904.3 through 904.3.4.
2. The additional special inspections and testing to be provided as required by Sections 906 and
907 and other applicable sections of this code, including the applicable standards referenced
by this code.
904.4 WIND RESISTANCE
The statement of special inspections shall include wind requirements for structures constructed in the
following areas:
1. In wind Exposure Category B, where the 3-second-gust basic wind speed is 193 km/hr or greater.
2. In wind Exposure Category C or D, where the 3-second- gust basic wind speed is 177 km/hr or
greater.
904.4.1 WIND REQUIREMENTS IN THE STATEMENT OF SPECIAL INSPECTIONS
When Section 904.4 specifies that wind requirements be included, the statement of special
inspections shall identify the main wind-force-resisting systems and wind-resisting components
subject to special inspections as specified in Section 904.4.2.
904.4.2 DETAILED REQUIREMENTS
The statement of special inspections shall include at least the following systems and
components:
1. Roof cladding and roof framing connections.
2. Wall connections to roof and floor diaphragms and framing.
3. Roof and floor diaphragm systems, including collectors, drag struts and boundary elements.
4. Vertical wind-force-resisting systems, including braced frames, moment frames and shear
walls.
5. Wind-force-resisting system connections to the foundation.
6. Fabrication and installation of systems or components required to meet the impact-resistance
requirements.
Exception: Fabrication of manufactured systems or components that have a label indicating
compliance with the wind-load and impact-resistance requirements of this code.
SECTION 905 SPECIAL INSPECTIONS FOR WIND REQUIREMENTS
905.1 SPECIAL INSPECTIONS FOR WIND REQUIREMENTS
Special inspections itemized in Sections 905.2 through 905.3, unless exempted by the exceptions to
Section 903.1, are required for buildings and structures constructed in the following areas:
1. In wind Exposure Category B, where the 3-second-gust basic wind speed is 193 km/hr or greater.
2. In wind Exposure Categories C or D, where the 3-second-gust basic wind speed is 177 km/hr or
greater.
905.2 STRUCTURAL WOOD
Continuous special inspection is required during field gluing operations of elements of the main
windforce-resisting system. Periodic special inspection is required for nailing, bolting, anchoring and
other fastening of components within the main windforce-resisting system, including wood shear
walls, wood diaphragms, drag struts, braces and hold-downs.
Exception: Special inspection is not required for wood shearwalls, shear panels and diaphragms,
including nailing, bolting, anchoring and other fastening to other components of the main windforceresisting system, where the fastener spacing of the sheathing is more than 100 mm on center.
All rights reserved
448 / 496
905.3 WIND-RESISTING COMPONENTS
Periodic special inspection is required for the following systems and components:
1. Roof cladding.
2. Wall cladding.
SECTION 906 SPECIAL INSPECTIONS FOR SEISMIC RESISTANCE
906.1 SPECIAL INSPECTIONS FOR SEISMIC RESISTANCE
Special inspections itemized in Sections 906.2 through 906.6, unless exempted by the exceptions of
Section 903.1, 904.3, or 904.3.1, are required for the following:
1. The seismic-force-resisting systems in structures assigned to Seismic Design Category C, D, E or F,
as determined in Chapter 3.
2. Designated seismic systems in structures assigned to Seismic Design Category D, E or F.
3. Architectural, mechanical and electrical components in structures assigned to Seismic Design
Category C, D, E or F that are required in Sections 906.6 and 906.7.
906.2 STRUCTURAL STEEL
Special inspection for structural steel shall be in accordance with the quality assurance plan
requirements of AISC 341.
Exceptions:
1. Special inspections of structural steel in structures assigned to Seismic Design Category C that are
not specifically detailed for seismic resistance, with a response modification coefficient, R, of 3 or
less, excluding cantilever column systems.
2. For ordinary moment frames, ultrasonic and magnetic particle testing of complete joint penetration
groove welds are only required for demand critical welds.
906.3 STRUCTURAL WOOD
Continuous special inspection is required during field gluing operations of elements of the seismicforce-resisting system. Periodic special inspection is required for nailing, bolting, anchoring and other
fastening of components within the seismic-force-resisting system, including wood shear walls, wood
diaphragms, drag struts, braces, shear panels and hold-downs.
Exception: Special inspection is not required for wood shearwalls, shear panels and diaphragms,
including nailing, bolting, anchoring and other fastening to other components of the seismic-forceresisting system, where the fastener spacing of the sheathing is more than 100 mm on center (o.c.).
906.4 STORAGE RACKS AND ACCESS FLOORS
Periodic special inspection is required during the anchorage of access floors and storage racks 2400
mm or greater in height in structures assigned to Seismic Design Category D, E or F.
906.5 ARCHITECTURAL COMPONENTS
Periodic special inspection during the erection and fastening of exterior cladding, interior and exterior
nonbearing walls and interior and exterior veneer in structures assigned to Seismic Design Category D,
E or F.
Exceptions:
1. Special inspection is not required for exterior cladding, interior and exterior nonbearing walls and
interior and exterior veneer 9000 mm or less in height above grade or walking surface.
2. Special inspection is not required for exterior cladding and interior and exterior veneer weighing
25.0 N/m2 or less.
3. Special inspection is not required for interior nonbearing walls weighing 70.0 N/m2 or less.
906.6 MECHANICAL AND ELECTRICAL COMPONENTS
Special inspection for mechanical and electrical equipment shall be as follows:
All rights reserved
449 / 496
1. Periodic special inspection is required during the anchorage of electrical equipment for emergency or
standby power systems in structures assigned to Seismic Design Category C, D, E or F;
2. Periodic special inspection is required during the installation of anchorage of other electrical
equipment in structures assigned to Seismic Design Category E or F;
3. Periodic special inspection is required during installation of piping systems intended to carry
flammable, combustible or highly toxic contents and their associated mechanical units in
structures assigned to Seismic Design Category C, D, E or F;
4. Periodic special inspection is required during the installation of HVAC ductwork that will contain
hazardous materials in structures assigned to Seismic Design Category C, D, E or F; and
5. Periodic special inspection is required during the installation of vibration isolation systems in
structures assigned to Seismic Design Category C, D, E or F where the construction documents
require a nominal clearance of 6.0 mm or less between the equipment support frame and restraint.
906.7 DESIGNATED SEISMIC SYSTEM VERIFICATION
The special inspector shall examine designated seismic systems requiring seismic qualification in
accordance with Section 907.4 and verify that the label, anchorage or mounting conforms to the
certificate of compliance.
SECTION 907 STRUCTURAL TESTING FOR SEISMIC RESISTANCE
907.1 TESTING AND QUALIFICATION FOR SEISMIC RESISTANCE
The testing and qualification specified in Sections 907.2 through 907.4, unless exempted from special
inspections by the exceptions of Section 903.1, 904.3 or 904.3.1 are required as follows:
1. The seismic-force-resisting systems in structures assigned to Seismic Design Category C, D, E or F,
as determined in Chapter 3 shall meet the requirements of Sections 907.2 and 907.3, as applicable.
2. Designated seismic systems in structures assigned to Seismic Design Category C, D, E or F subject to
the special certification are required to be tested in accordance with Section 907.4.
3. Architectural, mechanical and electrical components in structures assigned to Seismic Design
Category C, D, E or F with an Ip = 1.0 are required to be tested in accordance with Section 907.4.
907.2 CONCRETE REINFORCEMENT
Where reinforcement complying with ASTM A 615 is used to resist earthquake-induced flexural and
axial forces in special moment frames, special structural walls and coupling beams connecting special
structural walls, in structures assigned to Seismic Design Category B, C, D, E or F as determined in
Chapter 3, the reinforcement shall comply with Section 521.1.5.
907.3 STRUCTURAL STEEL
Testing for structural steel shall be in accordance with the quality assurance plan requirements of AISC
341.
907.4 SEISMIC CERTIFICATION OF NONSTRUCTURAL COMPONENTS
The registered design professional shall state the applicable seismic certification requirements for
nonstructural components and designated seismic systems on the construction documents.
1. The manufacturer of each designated seismic system components subject to the provisions of
Chapter 3 shall test or analyze the component and its mounting system or anchorage and submit a
certificate of compliance for review and acceptance by the registered design professional
responsible for the design of the designated seismic system and for approval by the building
official. Certification shall be based on an actual test on a shake table, by three-dimensional shock
tests, by an analytical method using dynamic characteristics and forces, by the use of experience
data (i.e., historical data demonstrating acceptable seismic performance) or by more rigorous
analysis providing for equivalent safety.
2. Manufacturer’s certification of compliance for the general design requirements of Chapter 3 shall be
based on analysis, testing or experience data.
All rights reserved
450 / 496
SECTION 908 CONTRACTOR RESPONSIBILITY
908.1 CONTRACTOR RESPONSIBILITY
Each contractor responsible for the construction of a main wind- or seismic-force-resisting system,
designated seismic system or a wind-or seismic-resisting component listed in the statement of
special inspections shall submit a written statement of responsibility to the building official and the
owner prior to the commencement of work on the system or component.
SECTION 909 STRUCTURAL OBSERVATIONS
909.1 GENERAL
Where required by the provisions of Section 909.2 or 909.3, the owner shall employ a registered design
professional to perform structural observations as defined in Section 901.
909.2 STRUCTURAL OBSERVATIONS FOR SEISMIC RESISTANCE
Structural observations shall be provided for those structures assigned to Seismic Design Category D, E
or F, as determined in Chapter 3, where one or more of the following conditions exist:
1. The structure is classified as Occupancy Category III or IV in accordance with Table 301.6-1.
2. The height of the structure is greater than 22 000 mm above the base.
3. The structure is assigned to Seismic Design Category E, is classified as Occupancy Category I or II in
accordance with Table 301.6-1, and is greater than two stories above grade plane.
4. When so designated by the registered design professional responsible for the structural design.
5. When such observation is specifically required by the building official.
909.3 STRUCTURAL OBSERVATIONS FOR WIND REQUIREMENTS
Structural observations shall be provided for those structures sited where the basic wind speed
exceeds 49 m/sec , where one or more of the following conditions exist:
1. The structure is classified as Occupancy Category III or IV in accordance with Table 301.6-1.
2. The building height of the structure is greater than 22 000 mm.
3. When so designated by the registered design professional responsible for the structural design.
SECTION 910 DESIGN STRENGTH OF MATERIALS
910.1 CONFORMANCE TO STANDARDS
The design strengths and permissible stresses of any structural material that are identified by a
manufacturer’s designation as to manufacture and grade by mill tests, or the strength and stress grade
is otherwise confirmed to the satisfaction of the building official, shall conform to the specifications and
methods of design of accepted engineering practice or the approved rules in the absence of applicable
standards.
910.2 NEW MATERIALS
For materials that are not specifically provided for in this code, the design strengths and permissible
stresses shall be established by tests as provided for in Section 911.
SECTION 911 ALTERNATIVE TEST PROCEDURE
911.1 GENERAL
In the absence of approved rules or other approved standards, the building official shall make, or
cause to be made, the necessary tests and investigations; or the building official shall accept duly
authenticated reports from approved agencies in respect to the quality and manner of use of new
materials or assemblies. The cost of all tests and other investigations required under the provisions of
this code shall be borne by the applicant.
All rights reserved
451 / 496
SECTION 912 TEST SAFE LOAD
912.1 WHERE REQUIRED
Where proposed construction is not capable of being designed by approved engineering analysis, or
where proposed construction design method does not comply with the applicable material design
standard, the system of construction or the structural unit and the connections shall be subjected to
the tests. The building official shall accept certified reports of such tests conducted by an approved
testing agency, provided that such tests meet the requirements of this code and approved procedures.
SECTION 913 IN-SITU LOAD TESTS
913.1 GENERAL
Whenever there is a reasonable doubt as to the stability or load-bearing capacity of a completed
building, structure or portion thereof for the expected loads, an engineering assessment shall be
required. The engineering assessment shall involve either a structural analysis or an in-situ load test, or
both. The structural analysis shall be based on actual material properties and other as-built conditions
that affect stability or load-bearing capacity, and shall be conducted in accordance with the applicable
design standard. If the structural assessment determines that the load-bearing capacity is less than that
required by the code, load tests shall be conducted in accordance with Section 913.2. If the building,
structure or portion thereof is found to have inadequate stability or load-bearing capacity for the
expected loads, modifications to ensure structural adequacy or the removal of the inadequate
construction shall be required.
913.2 TEST STANDARDS
Structural components and assemblies shall be tested in accordance with the appropriate material
standards. In the absence of a standard that contains an applicable load test procedure, the test
procedure shall be developed by a registered design professional and approved. The test procedure shall
simulate loads and conditions of application that the completed structure or portion thereof will be
subjected to in normal use.
913.3 IN-SITU LOAD TESTS
In-situ load tests shall be conducted in accordance with Section 913.3.1 or 913.3.2 and shall be
supervised by a registered design professional. The test shall simulate the applicable loading conditions
specified in Chapter 3 as necessary to address the concerns regarding structural stability of the
building, structure or portion thereof.
913.3.1 LOAD TEST PROCEDURE SPECIFIED
In the absence of specific load factors or acceptance criteria, the load factors and acceptance
criteria in Section 913.3.2 shall apply.
913.3.2 LOAD TEST PROCEDURE NOT SPECIFIED
In the absence of applicable load test procedures contained within a standard referenced by this
code or acceptance criteria for a specific material or method of construction, such existing
structure shall be subjected to a test procedure developed by a registered design professional that
simulates applicable loading and deformation conditions. For components that are not a part of
the seismic-load-resisting system, the test load shall be equal to two times the unfactored design
loads. The test load shall be left in place for a period of 24 hours. The structure shall be
considered to have successfully met the test requirements where the following criteria are
satisfied:
1. Under the design load, the deflection shall not exceed the limitations specified in Section
301.4.
2. Within 24 hours after removal of the test load, the structure shall have recovered not less than
75 percent of the maximum deflection.
All rights reserved
452 / 496
3. During and immediately after the test, the structure shall not show evidence of failure.
SECTION 914 EXISTING BUILDING PROVISIONS
914.1 SCOPE
The provisions of this appendix shall apply to the design and construction of alterations and additions
and to existing structures with a change in use.
914.2 STRUCTURALLY INDEPENDENT ADDITIONS
An addition that is structurally independent from an existing structure shall be designed and
constructed in accordance with the seismic requirements for new structures.
914.3 STRUCTURALLY DEPENDENT ADDITIONS
Where an addition is not structurally independent from an existing structure, the addition and
alterations to the existing structure shall be designed and constructed such that the entire structure
conforms to the seismic force-resistance requirements for new structures.
EXCEPTIONS: The entire structure shall not be required to comply with the seismic forceresistance
requirements for new structures where all of the following conditions are met:
1. The addition complies with the requirements for new structures.
2. The addition does not increase the seismic forces in any structural element of the existing structure
by more than 10 percent unless the capacity of the element subject to the increased forces is still in
compliance with this standard.
3. The addition does not decrease the seismic resistance of any structural element of the existing
structure unless the reduced resistance is equal to or greater than that required for new structures.
914.4 ALTERATIONS
Alterations are permitted to be made to any structure without requiring the existing structure to
comply with this standard provided the alterations comply with the requirements for a new structure.
Alterations that increase the seismic force in any existing structural element by more than 10 percent
or decrease the design strength of any existing structural element to resist seismic forces by more than
10 percent shall not be permitted unless the entire seismic force-resisting system is determined to
comply with this standard for a new structure.
EXCEPTIONS: Alterations to existing structural elements or additions of new structural elements that
are not required by this standard and are initiated for the purpose of increasing the strength or
stiffness of the seismic force-resisting system of an existing structure shall not be required to be
designed for forces in accordance with this standard provided that an engineering analysis is
submitted indicating the following:
1. The design strengths of existing structural elements required to resist seismic forces are not
reduced.
2. The seismic force to required existing structural elements is not increased beyond their design
strength.
3. New structural elements are detailed and connected to the existing structural elements as required
by this standard.
4. New or relocated nonstructural elements are detailed and connected to existing or new structural
elements as required by this standard.
5. The alteration does not create a structural irregularity or make an existing irregularity more severe.
914.5 CHANGE OF USE
Where a change of use results in a structure being reclassifi ed to a higher occupancy category as
defined in Table 305.1-1, the structure shall conform to the seismic requirements for new
construction.
All rights reserved
453 / 496
EXCEPTIONS:
1. Where a change of use results in a structure being reclassified from Occupancy Category I or II to
Occupancy Category III and the structure is located in a seismic map area where SDS < 0.33,
compliance with the seismic requirements of this standard is not required.
2. Specifi c seismic detailing requirements of this standard for a new structure need not be met where
it can be shown that the level of performance and seismic safety is equivalent to that of a new
structure. Such analysis shall consider the regularity, overstrength, redundancy, and ductility of the
structure within the context of the existing and retrofit (if any) detailing provided.
SECTION 915 STRENGTH EVALUATION OF EXISTING STRUCTURES
915.1 Strength evaluation — General
915.1.1
If there is doubt that a part or all of a structure meets the safety requirements of this Code, a
strength evaluation shall be carried out as required by the licensed design professional or
building official.
915.1.2
If the effect of the strength deficiency is well understood and if it is feasible to measure the
dimensions and material properties required for analysis, analytical evaluations of strength
based on those measurements shall suffice. Required data shall be determined in accordance
with 915.2.
915.1.3
If the effect of the strength deficiency is not well understood or if it is not feasible to establish
the required dimensions and material properties by measurement, a load test shall be required
if the structure is to remain in service.
915.1.4
If the doubt about safety of a part or all of a structure involves deterioration, and if the observed
response during the load test satisfies the acceptance criteria, the structure or part of the
structure shall be permitted to remain in service for a specified time period. If deemed
necessary by the licensed design professional, periodic reevaluations shall be conducted.
915.2 DETERMINATION OF REQUIRED DIMENSIONS AND MATERIAL PROPERTIES
915.2.1
Dimensions of the structural elements shall be established at critical sections.
915.2.2
Locations and sizes of the reinforcing bars, welded wire reinforcement, or tendons shall be
determined by measurement. It shall be permitted to base reinforcement locations on available
drawings if spot checks are made confirming the information on the drawings.
915.2.3
If required, concrete strength shall be based on results of cylinder tests from the original
construction or tests of cores removed from the part of the structure where the strength is in
question. For strength evaluation of an existing structure, cylinder or core test data shall be used
to estimate an equivalent fc′ . The method for obtaining and testing cores shall be in accordance
with ASTM C42M.
All rights reserved
454 / 496
915.2.4
If required, reinforcement or prestressing steel strength shall be based on tensile tests of
representative samples of the material in the structure in question.
915.2.5
If the required dimensions and material properties are determined through measurements and
testing, and if calculations can be made in accordance with 915.1.2, it shall be permitted to
increase φ from those specified in 513.3, but φ shall not be more than:
Tension-controlled sections, as defined in 514.3.4.................................................................... 1.0
Compression-controlled sections, as defined in 514.3.3:
Members with spiral reinforcement conforming to 514.9.3..................................................... 0.9
Other reinforced members......................................................................................................... 0.8
Shear and/or torsion................................................................................................................... 0.8
Bearing on concrete ................................................................................................................... 0.8
915.3 LOAD TEST PROCEDURE
915.3.1 LOAD ARRANGEMENT
The number and arrangement of spans or panels loaded shall be selected to maximize the
deflection and stresses in the critical regions of the structural elements of which strength is in
doubt. More than one test load arrangement shall be used if a single arrangement will not
simultaneously result in maximum values of the effects (such as deflection, rotation, or stress)
necessary to demonstrate the adequacy of the structure.
915.3.2 LOAD INTENSITY
The total test load (including dead load already in place) shall not be less than the larger of (a),
(b), and (c):
(a) 1.15D + 1.5L + 0.4(Lr or S or R)
(b) 1.15D + 0.9L + 1.5(Lr or S or R)
(c) 1.3D
The load factor on the live load L in (b) shall be permitted to be reduced to 0.45 except for
garages, areas occupied as places of public assembly, and all areas where L is greater than 4.8
2
kN/m . It shall be
permitted to reduce L in accordance with the provisions of the applicable general building code.
915.3.3
A load test shall not be made until that portion of the structure to be subjected to load is at least
56 days old. If the owner of the structure, the contractor, and all involved parties agree, it shall
be permitted to make the test at an earlier age.
915.4 LOADING CRITERIA
915.4.1
The initial value for all applicable response measurements (such as deflection, rotation, strain,
slip, crack widths) shall be obtained not more than 1 hour before application of the first load
increment. Measurements shall be made at locations where maximum response is expected.
Additional measurements shall be made if required.
All rights reserved
455 / 496
915.4.2
Test load shall be applied in not less than four approximately equal increments.
915.4.3
Uniform test load shall be applied in a manner to ensure uniform distribution of the load
transmitted to the structure or portion of the structure being tested. Arching of the applied load
shall be avoided.
915.4.4
A set of response measurements shall be made after each load increment is applied and after
the total load has been applied on the structure for at least 24 hours.
915.4.5
Total test load shall be removed immediately after all response measurements defined in 20.4.4
are made.
915.4.6
A set of final response measurements shall be made 24 hours after the test load is removed.
915.5 ACCEPTANCE CRITERIA
915.5.1
The portion of the structure tested shall show no evidence of failure. Spalling and crushing of
compressed concrete shall be considered an indication of failure.
915.5.2
Measured deflections shall satisfy either Equation 915.5.2-1 or 915.5.2-2:
EQUATION 915.5.2-1
EQUATION 915.5.2-2
If the measured maximum and residual deflections, Δ1 and Δr , do not satisfy Equation 915.5.2-1
or 915.5.2-2, it shall be permitted to repeat the load test.
The repeat test shall be conducted not earlier than 72 hours after removal of the first test load.
The portion of the structure tested in the repeat test shall be considered acceptable if deflection
recovery Δr satisfies the condition:
EQUATION 915.5.2-3
where Δ2 is the maximum deflection measured during the second test relative to the position of
the structure at the beginning of the second test.
915.5.3
Structural members tested shall not have cracks indicating the imminence of shear failure.
915.5.4
In regions of structural members without transverse reinforcement, appearance of structural
cracks inclined to the longitudinal axis and having a horizontal projection longer than the depth
of the member at midpoint of the crack shall be evaluated.
All rights reserved
456 / 496
915.5.5
In regions of anchorage and lap splices, the appearance along the line of reinforcement of a
series of short inclined cracks or horizontal cracks shall be evaluated.
915.6 PROVISION FOR LOWER LOAD RATING
If the structure under investigation does not satisfy conditions or criteria of 915.1.2, 915.5.2, or
915.5.3, the structure shall be permitted for use at a lower load rating based on the results of the load
test or analysis, if approved by the building official.
915.7 SAFETY
915.7.1
Load tests shall be conducted in such a manner as to provide for safety of life and structure
during the test.
915.7.2
Safety measures shall not interfere with load test procedures or affect results.
All rights reserved
457 / 496
APPENDIX A
GRADING
SECTION A101 GENERAL
A101.1 SCOPE
The provisions of this chapter apply to grading, excavation and earthwork construction, including fills
and embankments. Where conflicts occur between the technical requirements of this chapter and the
geotechnical report, the geotechnical report shall govern.
SECTION A102 PERMITS REQUIRED
A102.1
No grading shall be performed without first having obtained a permit therefor from the building official.
A grading permit does not include the construction of retaining walls or other structures.
A102.2 EXEMPTIONS
A grading permit shall not be required for the following:
1. Grading in an isolated, self-contained area, provided there is no danger to the public, and that such
grading will not adversely affect adjoining properties.
2. Excavation for construction of a structure permitted under this code.
3. Cemetery graves.
4. Refuse disposal sites controlled by other regulations.
5. Excavations for wells, or trenches for utilities.
6. Mining, quarrying, excavating, processing or stockpiling rock, sand, gravel, aggregate or clay
controlled by other regulations, provided such operations do not affect the lateral support of, or
significantly increase stresses in, soil on adjoining properties.
7. Exploratory excavations performed under the direction of a registered design professional.
Exemption from the permit requirements of this appendix shall not be deemed to grant authorization
for any work to be done in any manner in violation of the provisions of this code or any other laws or
ordinances of this jurisdiction.
SECTION A103 PERMIT APPLICATION AND SUBMITTALS
A103.1 SUBMITTAL REQUIREMENTS
Refer to the Administrative Document for this article.
A103.2 SITE PLAN REQUIREMENTS
Refer to the Administrative Document for this article.
A103.3 GEOTECHNICAL REPORT
Refer to the Administrative Document for this article.
A103.4 LIQUEFACTION STUDY
Refer to the Administrative Document for this article.
SECTION A104 INSPECTIONS
A104.1 GENERAL
Inspections shall be governed by provisions of this code.
All rights reserved
458 / 496
A104.2 SPECIAL INSPECTIONS
The special inspection requirements of Section 903.7 shall apply to work performed under a grading
permit where required by the building official.
SECTION A105 EXCAVATIONS
A105.1 MAXIMUM SLOPE
The slope of cut surfaces shall be no steeper than is safe for the intended use, and shall be no steeper
than two units horizontal to one unit vertical (50-percent slope) unless the owner or authorized agent
furnishes a geotechnical report justifying a steeper slope.
Exceptions:
1. A cut surface shall be permitted to be at a slope of 1.5 units horizontal to one unit vertical (67-percent
slope) provided that all of the following are met:
1.1. It is not intended to support structures or sur- charges.
1.2. It is adequately protected against erosion.
1.3. It is no more than 2400 mm in height.
1.4. It is approved by the building code official.
1.5. Ground water is not encountered.
2. A cut surface in bedrock shall be permitted to be at a slope of one unit horizontal to one unit
vertical (100-percent slope).
SECTION A106 FILLS
A106.1 GENERAL
Unless otherwise recommended in the geotechnical report, fills shall comply with the provisions of
this section.
A106.2 SURFACE PREPARATION
The ground surface shall be pre- pared to receive fill by removing vegetation, topsoil and other
unsuitable materials, and scarifying the ground to provide a bond with the fill material.
A106.3 BENCHING
Where existing grade is at a slope steeper than five units horizontal to one unit vertical (20-percent slope)
and the depth of the fill exceeds 1500 mm benching shall be provided in accordance with Figure A106.31. A key shall be provided which is at least 3000 mm in width and 600 mm in depth.
All rights reserved
459 / 496
FIGURE A106.3-1 BENCHING DETAILS
A106.4 FILL MATERIAL
Fill material shall not include organic, frozen or other deleterious materials. No rock or similar
irreducible material greater than 300 mm in any dimension shall be included in fills.
A106.5 COMPACTION
All fill material shall be compacted to 90 percent of maximum density as determined by ASTM D 1557,
Modified Proctor, in lifts not exceeding 300 mm in depth.
A106.6 MAXIMUM SLOPE
The slope of fill surfaces shall be no steeper than is safe for the intended use. Fill slopes steeper than two
units horizontal to one unit vertical (50-percent slope) shall be justified by a geotechnical report or
engineering data.
SECTION A107 SETBACKS
A107.1 GENERAL
Cut and fill slopes shall be set back from the property lines in accordance with this section. Setback
dimensions shall be measured perpendicular to the property line and shall be as shown in Figure
A107.1-1, unless substantiating data is submitted justifying reduced setbacks.
All rights reserved
460 / 496
FIGURE A107.1-1 DRAINAGE DIMENSIONS
A107.2 TOP OF SLOPE
The setback at the top of a cut slope shall not be less than that shown in Figure A107.1-1, or than is
required to accommodate any required interceptor drains, whichever is greater.
A107.3 SLOPE PROTECTION
Where required to protect adjacent properties at the toe of a slope from adverse effects of the grading,
additional protection, approved by the building official, shall be included. Such protection may include
but shall not be limited to:
1. Setbacks greater than those required by Figure A107.1-1.
2. Provisions for retaining walls or similar construction.
3. Erosion protection of the fill slopes.
4. Provision for the control of surface waters.
SECTION A108 DRAINAGE AND TERRACING
A108.1 GENERAL
Unless otherwise recommended by a registered design professional, drainage facilities and terracing
shall be provided in accordance with the requirements of this section.
Exception: Drainage facilities and terracing need not be provided where the ground slope is not
steeper than 3 horizontal to 1 vertical (33 percent).
A108.2 TERRACES
Terraces at least 1800 mm in width shall be established at not more than 9000 mm vertical intervals
on all cut or fill slopes to control surface drainage and debris. Suitable access shall be provided to allow
for cleaning and maintenance.
Where more than two terraces are required, one terrace, located at approximately mid-height, shall
be at least 3600 mm in width.
All rights reserved
461 / 496
Swales or ditches shall be provided on terraces. They shall have a minimum gradient of 20 horizontal
to 1 vertical (5 percent) and shall be paved with concrete not less than 80 mm in thickness, or with
other materials suitable to the application. They shall have a minimum depth of 300 mm and a
minimum width of 1500 mm.
A single run of swale or ditch shall not collect runoff from a tributary area exceeding 1200 m 2
(projected) without discharging into a down drain.
A108.3 INTERCEPTOR DRAINS
Interceptor drains shall be installed along the top of cut slopes receiving drainage from a tributary
width greater than 12 000 mm, measured horizontally. They shall have a minimum depth of 300 mm
and a minimum width of 900 mm. The slope shall be approved by the building official, but shall not be
less than 50 horizontal to 1 vertical (2 percent). The drain shall be paved with concrete not less than 80
mm in thickness, or by other materials suitable to the application. Discharge from the drain shall be
accomplished in a manner to prevent erosion and shall be approved by the building official.
A108.4 DRAINAGE ACROSS PROPERTY LINES
Drainage across property lines shall not exceed that which existed prior to grading. Excess or
concentrated drainage shall be contained on site or directed to an approved drainage facility. Erosion
of the ground in the area of discharge shall be prevented by installation of nonerosive down drains or
other devices.
SECTION A109 EROSION CONTROL
A109.1 GENERAL
The faces of cut and fill slopes shall be prepared and maintained to control erosion. This control shall
be permitted to consist of effective planting.
Exception: Erosion control measures need not be provided on cut slopes not subject to erosion due to
the erosion-resistant character of the materials. Erosion control for the slopes shall be installed as
soon as practicable and prior to calling for final inspection.
A109.2 OTHER DEVICES
Where necessary, check dams, cribbing, riprap or other devices or methods shall be employed to
control erosion and provide safety.
All rights reserved
462 / 496
APPENDIX B
ANCHORING TO CONCRETE
SECTION B101 SCOPE
B101.1
This appendix provides design requirements for anchors in concrete used to transmit structural loads
by means of tension, shear, or a combination of tension and shear between: (a) connected structural
elements; or (b) safety-related attachments and structural elements. Safety levels specified are
intended for in-service conditions, rather than for short-term handling and construction conditions.
B101.2
This appendix applies to both cast-in anchors and post-installed anchors. Specialty inserts,
throughbolts, multiple anchors connected to a single steel plate at the embedded end of the anchors,
adhesive or grouted anchors, and direct anchors such as powder or pneumatic actuated nails or bolts,
are not included. Reinforcement used as part of the embedment shall be designed in accordance with
other parts of ASC (Afgan Structural Code).
B101.3
Headed studs and headed bolts having a geometry that has been demonstrated to result in a pullout
strength in uncracked concrete equal or exceeding 1.4Np (where Np is given by Equation B104.3.4-1
are included. Hooked bolts that have a geometry that has been demonstrated to result in a pullout
strength without the benefit of friction in uncracked concrete equal or exceeding 1.4Np (where Np is
given by Equation B104.3.5-1 are included. Post-installed anchors that meet the assessment
requirements of ACI 355.2 are included. The suitability of the post-installed anchor for use in concrete
shall have been demonstrated by the ACI 355.2 prequalification tests.
B101.4
Load applications that are predominantly high cycle fatigue or impact loads are not covered by this
appendix.
SECTION B102 GENERAL REQUIREMENTS
B102.1
Anchors and anchor groups shall be designed for critical effects of factored loads as determined by
elastic analysis. Plastic analysis approaches are permitted where nominal strength is controlled by
ductile steel elements, provided that deformational compatibility is taken into account.
B102.2
The design strength of anchors shall equal or exceed the largest required strength calculated from the
applicable load combinations in 513.2.
B102.3
When anchor design includes earthquake forces for structures assigned to Seismic Design Category C,
D, E, or F, the additional requirements of B102.3.1 through B102.3.6 shall apply.
B102.3.1
The provisions of Appendix B do not apply to the design of anchors in plastic hinge zones of
concrete structures under earthquake forces.
All rights reserved
463 / 496
B102.3.2
Post-installed structural anchors shall be qualified for use in cracked concrete and shall have
passed the Simulated Seismic Tests in accordance with ACI 355.2. Pullout strength Np and steel
strength of the anchor in shear Vsa shall be based on the results of the ACI 355.2 Simulated
Seismic Tests.
B102.3.3
The anchor design strength associated with concrete failure modes shall be taken as 0.75φNn
and 0.75φVn, where φ is given in B103.3 or B103.4, and Nn and Vn are determined in accordance
with B104.2, B104.3, B104.4, B105.2, and B105.3, assuming the concrete is cracked unless it can
be demonstrated that the concrete remains uncracked.
B102.3.4
Anchors shall be designed to be governed by the steel strength of a ductile steel element as
determined in accordance with B104.1 and B105.1, unless either B102.3.5 or B102.3.6 is
satisfied.
B102.3.5
Instead of B102.3.4, the attachment that the anchor is connecting to the structure shall be
designed so that the attachment will undergo ductile yielding at a force level corresponding to
anchor forces no greater than the design strength of anchors specified in B102.3.3.
D
B102.3.6
As an alternative to B102.3.4 and B102.3.5, it shall be permitted to take the design strength of
the anchors as 0.4 times the design strength determined in accordance with B102.3.3. For the
anchors of stud bearing walls, it shall be permitted to take the design strength of the anchors as
0.5 times the design strength determined in accordance with B102.3.3.
B102.4
The values of fc’ used for calculation purposes in this appendix shall not exceed 70 MPa for cast-in
anchors, and 55 MPa for post-installed anchors. Testing is required for post-installed anchors when
used in concrete with fc’ greater than 55 MPa.
SECTION B103 GENERAL REQUIREMENTS FOR STRENGTH OF ANCHORS
B103.1
Strength design of anchors shall be based either on computation using design models that satisfy the
requirements of B103.2, or on test evaluation using the 5 percent fractile of test results for the
following:
(a) Steel strength of anchor in tension (B104.1);
(b) Steel strength of anchor in shear (B105.1);
(c) Concrete breakout strength of anchor in tension (B104.2);
(d) Concrete breakout strength of anchor in shear (B105.2);
(e) Pullout strength of anchor in tension (B104.3);
(f) Concrete side-face blowout strength of anchor in tension (B104.4); and
(g) Concrete pryout strength of anchor in shear (B105.3).
In addition, anchors shall satisfy the required edge distances, spacings, and thicknesses to preclude
splitting failure, as required in B107.
All rights reserved
464 / 496
FIGURE B103.1-1 FAILURE MODE FOR ANCHORS
B103.1.1
For the design of anchors, except as required in B102.3,
φNn ≥ Nua
EQUATION B103.1.1-1
φVn ≥ Vua
EQUATION B103.1.1-2
B103.1.2
In Equation B103.1.1-1 and Equation B103.1.1-2, φNn and φVn are the lowest design strengths
determined from all appropriate failure modes. φNn is the lowest design strength in tension of
an anchor or group of anchors as determined from consideration of φNsa, φnNpn, either φNsb or
φNsbg, and either φNcb or φNcbg. φVn is the lowest design strength in shear of an anchor or a
group of anchors as determined from consideration of: φVsa, either φVsb or φVsbg, and either
φVcb or φVcbg.
B103.1.3
When both Nua and Vua are present, interaction effects shall be considered in accordance with
B103.2.3.
B103.2
The nominal strength for any anchor or group of anchors shall be based on design models that result
in predictions of strength in substantial agreement with results of comprehensive tests. The materials
All rights reserved
465 / 496
used in the tests shall be compatible with the materials used in the structure. The nominal strength
shall be based on the 5 percent fractile of the basic individual anchor strength. For nominal strengths
related to concrete strength, modifications for size effects, the number of anchors, the effects of close
spacing of anchors, proximity to edges, depth of the concrete member, eccentric loadings of anchor
groups, and presence or absence of cracking shall be taken into account. Limits on edge distances and
anchor spacing in the design models shall be consistent with the tests that verified the model.
B103.2.1
The effect of reinforcement provided to restrain the concrete breakout shall be permitted to be
included in the design models used to satisfy B103.2. Where anchor reinforcement is provided in
accordance with B104.2.9 and B105.2.9, calculation of the concrete breakout strength in
accordance with B104.2 and B105.2 is not required.
B103.2.2
For anchors with diameters not exceeding 50 mm, and tensile embedments not exceeding 600
mm in depth, the concrete breakout strength requirements shall be considered satisfied by the
design procedure of B104.2 and B105.2.
B103.2.3
Resistance to combined tensile and shear loads shall be considered in design using an interaction
expression that results in computation of strength in substantial agreement with results of
comprehensive tests. This requirement shall be considered satisfied by B106.
B103.3
Strength reduction factor φ for anchors in concrete shall be as follows when the load combinations of
513.2 are used:
a) Anchor governed by strength of a ductile steel element
i) Tension loads....................... 0.75
ii) Shear loads......................... 0.65
b) Anchor governed by strength of a brittle steel element
i) Tension loads....................... 0.65
ii) Shear loads......................... 0.60
c) Anchor governed by concrete breakout, side-face blowout, pullout, or pryout strength
Condition A
0.75
Condition B
0.70
0.75
0.70
Category 1
(Low sensitivity to installation and high reliability)
0.75
0.65
Category 2
(Medium sensitivity to installation and medium reliability)
0.65
0.55
Category 3
0.55
0.45
i) Shear loads
ii) Tension loads
Cast-in headed studs, headed bolts, or hooked bolts
Post-installed anchors with category as determined
from ACI 355.2
All rights reserved
466 / 496
(High sensitivity to installation and lower reliability)
Condition A applies where supplementary reinforcement is present except for pullout and pryout
strengths.
Condition B applies where supplementary reinforcement is not present, and for pullout or pryout
strength.
B103.4
Strength reduction factor φ for anchors in concrete shall be as follows when the load combinations are
used:
a) Anchor governed by strength of a ductile steel element
i) Tension loads............................0.80
ii) Shear loads..............................0.75
b) Anchor governed by strength of a brittle steel element
i) Tension loads............................0.70
ii) Shear loads..............................0.65
c) Anchor governed by concrete breakout, side-face blowout, pullout, or pryout strength
Condition A
0.85
Condition B
0.75
0.85
0.75
Category 1
(Low sensitivity to installation and high reliability)
0.85
0.75
Category 2
(Medium sensitivity to installation and medium reliability)
0.75
0.65
Category 3
(High sensitivity to installation and lower reliability)
0.65
0.55
i) Shear loads
ii) Tension loads
Cast-in headed studs, headed bolts, or hooked bolts
Post-installed anchors with category as determined
from ACI 355.2
Condition A applies where supplementary reinforcement is present except for pullout and pryout
strengths.
Condition B applies where supplementary reinforcement is not present, and for pullout and pryout
strengths.
SECTION B104 DESIGN REQUIREMENTS FOR TENSILE LOADING
B104.1 STEEL STRENGTH OF ANCHOR ON TENSION
B104.1.1
The nominal strength of an anchor in tension as governed by the steel, Nsa, shall be evaluated by
calculations based on the properties of the anchor material and the physical dimensions of the
anchor.
All rights reserved
467 / 496
B104.1.2
The nominal strength of a single anchor or group of anchors in tension, Nsa, shall not exceed
Nsa = nAse,Nfuta
EQUATION B104.1.2-1
where n is the number of anchors in the group, Ase,N is the effective cross-sectional area of a
2
single anchor in tension, mm , and futa shall not be taken greater than the smaller of 1.9fya and
860 MPa.
B104.2 CONCRETE BREAKOUT STRENGTH OF ANCHOR IN TENSION
B104.2.1
The nominal concrete breakout strength, Ncb or Ncbg, of a single anchor or group of anchors in
tension shall not exceed
(a) For a single anchor
Ncb=(Anc/Anco)ψed, Nψc, Nψcp, NNb
EQUATION B104.2.1-1
(b) For a group of anchors
Ncbg=(Anc/Anco)ψec, Nψed, Nψc, Nψcp, NNb
EQUATION B104.2.1-2
Factors ψec,N, ψed,N, ψc,N, and ψcp,N are defined in B104.2.4, B104.2.5, B104.2.6, and B104.2.7,
respectively.
ANc is the projected concrete failure area of a single anchor or group of anchors that shall be
approximated as the base of the rectilinear geometrical figure that results from projecting the
failure surface outward 1.5hef from the centerlines of the anchor, or in the case of a group of
anchors, from a line through a row of adjacent anchors. ANc shall not exceed nANco, where n is
the number of tensioned anchors in the group. ANco is the projected concrete failure area of a
single anchor with an edge distance equal to or greater than 1.5hef
ANco = 9hef
All rights reserved
2
EQUATION B104.2.1-3
468 / 496
FIGURE B104.2.1-1 a) CALCULATION OF ANco AND b) CALCULATION OF ANc FOR SINGLE ACNHORS
AND GROUPS OF ACNHORS
B104.2.2
The basic concrete breakout strength of a single anchor in tension in cracked concrete, Nb, shall
not exceed
Nb = kcλ√
hef
1.5
EQUATION B104.2.2-1
where
kc = 10 for cast-in anchors; and
kc = 7 for post-installed anchors.
The value of kc for post-installed anchors shall be permitted to be increased above 7 based on
ACI 355.2 product-specific tests, but shall in no case exceed 10.
Alternatively, for cast-in headed studs and headed bolts with 280 mm ≤ hef ≤ 600 mm, Nb shall
not exceed
All rights reserved
469 / 496
Nb = 3.9λ√
hef
5/3
EQUATION B104.2.2-2
FIGURE B104.2.2-1 TENSION IN NERROW MEMBERS
B104.2.3
Where anchors are located less than 1.5hef from three or more edges, the value of hef used in
Equation B104.2.1-1 through B104.2.5-1 shall be th