GUIDE DESIGN SPECIFICATIONS FOR
BRIDGE TEMPORARY WORKS
2nd Edition | 2017
GSBTW-2 | ISBN 978-1-56051-642-2
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444 North Capitol Street, NW, Suite 249
Washington, DC 20001
202-624-5800 phone/202-624-5806 fax
www.transportation.org
Cover photos: Top: Utah 4500 South Bridge over I-215. Its temporary staging area for first SPMT
move in Salt Lake City, Utah, September 7, 2007. Photo provided by the Utah DOT. Bottom:
Temporary staging area for SPMT move for the Utah Pioneer Crossing over I-15, Lehi, Utah,
September 9, 2009. Photo provided by the Utah DOT.
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AASHTO EXECUTIVE COMMITTEE
2016–2017
Voting Members
OFFICERS:
PRESIDENT: David Bernhardt, Maine*
VICE PRESIDENT: John Schroer, Tennessee*
SECRETARY-TREASURER: Carlos Braceras, Utah
EXECUTIVE DIRECTOR: Bud Wright, Washington, D. C.
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REGIONAL REPRESENTATIVES:
REGION I:
Leslie Richards, Pennsylvania
Pete Rahn, Maryland
REGION II:
Charles Kilpatrick, Virginia
James Bass, Texas
REGION III:
Randall S. Blankenhorn, Illinois
Patrick McKenna, Missouri
REGION IV:
Carlos Braceras, Utah
Mike Tooley, Montana
IMMEDIATE PAST PRESIDENT: vacant
*Elected at the 2016 Annual Meeting in Boston, Massachusetts
Nonvoting Members
Executive Director: Bud Wright, Washington, DC
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HIGHWAY SUBCOMMITTEE ON BRIDGES AND STRUCTURES, 2016
GREGG FREDRICK, Chair
BRUCE V. JOHNSON, Vice Chair
JOSEPH L. HARTMANN, Federal Highway Administration, Secretary
PATRICIA J. BUSH, AASHTO Liaison
ALABAMA, Eric J. Christie, William “Tim”
Colquett, Randall B. Mullins
ALASKA, Richard A. Pratt
ARIZONA, David B. Benton, David L.
Eberhart, Pe-Shen Yang
ARKANSAS, Charles “Rick” Ellis
CALIFORNIA, Susan Hida, Thomas A.
Ostrom, Dolores Valls
COLORADO, Behrooz Far, Stephen
Harelson, Jessica Martinez
CONNECTICUT, Timothy D. Fields
DELAWARE, Barry A. Benton, Jason
Hastings
DISTRICT OF COLUMBIA, Donald L.
Cooney, Konjit C. “Connie” Eskender,
Richard Kenney
FLORIDA, Sam Fallaha, Dennis William
Potter, Jeff Pouliotte
GEORGIA, Bill DuVall, Steve Gaston
HAWAII, James Fu
IDAHO, Matthew Farrar
ILLINOIS, Tim A. Armbrecht, Carl Puzey
INDIANA, Anne M. Rearick
IOWA, Ahmad Abu-Hawash, Norman L.
McDonald
KANSAS, Mark E. Hoppe, John P. Jones
KENTUCKY, Mark Hite, Marvin Wolfe
LOUISIANA, Arthur D’Andrea, Paul Fossier,
Zhengzheng “Jenny” Fu
MAINE, Jeffrey S. Folsom, Wayne
Frankhauser, Michael Wight
MARYLAND, Earle S. Freedman, Jeffrey L.
Robert, Gregory Scott Roby
MASSACHUSETTS, Alexander K. Bardow,
Thomas Donald, Joseph Rigney
MICHIGAN, Matthew Jack Chynoweth,
David Juntunen
MINNESOTA, Arielle Ehrlich, Kevin
Western
MISSISSIPPI, Austin Banks, Justin Walker,
Scott Westerfield
MISSOURI, Dennis Heckman, Scott
Stotlemeyer
MONTANA, Kent M. Barnes, David F.
Johnson
NEBRASKA, Mark Ahlman, Fouad Jaber,
Mark J. Traynowicz
NEVADA, Troy Martin, Jessen Mortensen
NEW HAMPSHIRE, David L. Scott, Peter
Stamnas
NEW JERSEY, Xiaohua “Hannah” Cheng,
Nagnath “Nat” Kasbekar, Eli D. Lambert
NEW MEXICO, Ted L. Barber, Raymond M.
Trujillo, Jeff C. Vigil
NEW YORK, Wahid Albert, Richard
Marchione
NORTH CAROLINA, Brian Hanks, Scott
Hidden, Thomas Koch
NORTH DAKOTA, Terrence R. Udland
OHIO, Alexander B.C. Dettloff, Timothy J.
Keller
OKLAHOMA, Steven Jacobi, Walter Peters
OREGON, Bruce V. Johnson, Tanarat
Potisuk, Hormoz Seradj
PENNSYLVANIA, James M. Long,Thomas
P. Macioce, Lou Ruzzi
PUERTO RICO, (Vacant)
RHODE ISLAND, Georgette Chahine
SOUTH CAROLINA, Barry W. Bowers,
Terry B. Koon, Jeff Sizemore
SOUTH DAKOTA, Steve Johnson
TENNESSEE, John S. Hastings, Wayne J.
Seger
TEXAS, Bernie Carrasco, Jamie F. Farris,
Gregg A. Freeby
U.S. DOT, Joseph L. Hartmann
UTAH, Carmen Swanwick, Cheryl Hersh
Simmons, Joshua Sletten
VERMONT, James LaCroix, Wayne B.
Symonds
VIRGINIA, Prasad L. Nallapaneni, Kendal R.
Walus
WASHINGTON, Tony M. Allen, Thomas E.
Baker, Bijan Khaleghi
WEST VIRGINIA, Ahmed Mongi, Billy
Varney
iii
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WISCONSIN, Scot Becker, William C.
Dreher, William Olivia
WYOMING, Paul G. Cortez, Gregg C.
Frederick, Michael E. Menghini
GOLDEN GATE BRIDGE, HIGHWAY
AND TRANSPORTATION DISTRICT,
Kary H. Witt
MDTA, Dan Williams
N.J. TURNPIKE AUTHORITY, Richard J.
Raczynski
N.Y. STATE BRIDGE AUTHORITY,
Jeffrey Wright
PENN. TURNPIKE COMMISSION, James
Stump
U.S. ARMY CORPS OF ENGINEERS—
DEPARTMENT OF THE ARMY,
Phillip W. Sauser, Christopher H.
Westbrook
U.S. COAST GUARD, Kamal Elnahal
U.S. DEPARTMENT OF
AGRICULTURE—FOREST
SERVICE, John R. Kattell
KOREA, Eui-Joon Lee, Sang-Soon Lee
SASKATCHEWAN, Howard Yea
TRANSPORTATION RESEARCH BOARD,
Waseem Dekelb
iv
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GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
TABLE OF CONTENTS
SECTION 2—FALSEWORK
2.1—FALSEWORK DRAWINGS ........................................................................................................................... 2-1
2.2—MATERIALS AND MANUFACTURED COMPONENTS ............................................................................ 2-2
2.2.1—General ................................................................................................................................................... 2-2
2.2.2—Structural Steel ....................................................................................................................................... 2-2
2.2.2.1—Identification and Properties......................................................................................................... 2-2
2.2.2.2—Salvaged Steel .............................................................................................................................. 2-3
2.2.2.3—Welding ........................................................................................................................................ 2-3
2.2.3—Wood ...................................................................................................................................................... 2-4
2.2.3.1—Allowable Stresses ....................................................................................................................... 2-4
2.2.3.2—Modification Factors .................................................................................................................... 2-4
2.2.3.3—Used Lumber ................................................................................................................................ 2-4
2.2.4—Other Materials ....................................................................................................................................... 2-5
2.2.5—Manufactured Components..................................................................................................................... 2-5
2.2.5.1—General ......................................................................................................................................... 2-5
2.2.5.2—Maximum Loadings and Deflections ........................................................................................... 2-5
2.2.5.3—Factor of Safety ............................................................................................................................ 2-6
2.3—LOADS ............................................................................................................................................................. 2-6
2.3.1—General ................................................................................................................................................... 2-6
2.3.2—Loads and Load Combinations ............................................................................................................... 2-6
2.3.2.1—Loads and Load Designation ........................................................................................................ 2-6
2.3.2.2—Load Combinations and Load Factors .......................................................................................... 2-7
2.3.2.3—Load and Resistance Factored Design .......................................................................................... 2-8
2.3.2.4—Allowable Stress Design............................................................................................................. 2-10
2.3.3—Dead and Live Loads ............................................................................................................................ 2-10
2.3.3.1—Dead Load .................................................................................................................................. 2-10
2.3.3.2—Live Load ................................................................................................................................... 2-10
2.3.3.2.1—Construction Live Load...................................................................................................... 2-11
2.3.3.2.2—Impact ................................................................................................................................ 2-11
2.3.3.3—Minimum Vertical Load ............................................................................................................. 2-11
2.3.4—Construction Loads ............................................................................................................................... 2-11
2.3.4.1—Construction Dead Load ............................................................................................................. 2-11
2.3.4.2—Material Loads............................................................................................................................ 2-12
2.3.4.3—Personnel and Equipment Load .................................................................................................. 2-12
2.3.4.3.1—General ............................................................................................................................... 2-12
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SECTION 1—INTRODUCTION
1.1—SCOPE.............................................................................................................................................................. 1-1
1.2—RELATED PUBLICATIONS .......................................................................................................................... 1-1
1.3—DEFINITIONS ................................................................................................................................................. 1-2
1.4—METRIC CONVERSIONS .............................................................................................................................. 1-3
2.3.4.3.2—Individual Personnel Load ................................................................................................. 2-12
2.3.4.3.3—Uniformly Distributed Loads ............................................................................................. 2-13
2.3.4.3.4—Concentrated Loads............................................................................................................ 2-13
2.3.4.4—Horizontal Construction Load, Ch .............................................................................................. 2-14
2.3.4.5—Equipment Reactions, CR ........................................................................................................... 2-14
2.3.4.5.1—Rated Equipment ................................................................................................................ 2-14
2.3.4.5.2—Non-Rated Equipment........................................................................................................ 2-14
2.3.4.5.3—Impact ................................................................................................................................ 2-15
2.3.5—Environmental Loads............................................................................................................................ 2-15
2.3.5.1—Risk Category ............................................................................................................................. 2-15
2.3.5.2—Wind ........................................................................................................................................... 2-15
2.3.5.2.1—Design Wind Speed ............................................................................................................ 2-15
2.3.5.2.2—Frameworks without Cladding ........................................................................................... 2-15
2.3.5.2.3—Accelerated Wind Region .................................................................................................. 2-16
2.3.5.3—Snow ........................................................................................................................................... 2-16
2.3.5.4—Earthquake .................................................................................................................................. 2-16
2.3.5.4.1—Applicability ...................................................................................................................... 2-16
2.3.5.4.2—Use of ASCE 7 ................................................................................................................... 2-17
2.3.5.4.3—Other Standards for Earthquake Resistant Design ............................................................. 2-17
2.3.5.5—Stream Flow ............................................................................................................................... 2-17
2.3.5.6—Ice Loads .................................................................................................................................... 2-18
2.4—DESIGN ......................................................................................................................................................... 2-18
2.4.1—General ................................................................................................................................................. 2-18
2.4.2—Deflection ............................................................................................................................................. 2-19
2.4.3—Slenderness ........................................................................................................................................... 2-19
2.4.4—Overturning and Sliding ....................................................................................................................... 2-19
2.4.5—Steel Beam Grillages ............................................................................................................................ 2-20
2.4.6—Proprietary Shoring Systems ................................................................................................................ 2-20
2.4.7—Traffic Openings ................................................................................................................................... 2-21
2.5—FOUNDATIONS ............................................................................................................................................ 2-22
2.5.1—General ................................................................................................................................................. 2-22
2.5.2—Footings ................................................................................................................................................ 2-22
2.5.3—Pile Foundations ................................................................................................................................... 2-24
2.5.4—Foundations for Heavy-Duty Shoring Systems .................................................................................... 2-24
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SECTION 3—FORMWORK
3.1—MATERIALS AND FORM ACCESSORIES .................................................................................................. 3-1
3.1.1—General ................................................................................................................................................... 3-1
3.1.2—Sheathing ................................................................................................................................................ 3-1
3.1.3—Structural Supports ................................................................................................................................. 3-3
3.1.4—Prefabricated Formwork ......................................................................................................................... 3-3
3.1.5—Stay-in-Place Formwork ......................................................................................................................... 3-3
3.1.6—Form Accessories ................................................................................................................................... 3-3
3.2—LOADS ............................................................................................................................................................. 3-4
3.2.1—Vertical Loads ........................................................................................................................................ 3-4
3.2.2—Lateral Pressure of Fluid Concrete ......................................................................................................... 3-4
3.2.2.1—Form Pressure ............................................................................................................................... 3-4
3.2.2.2—Form Pressure—Reduced Hydrostatic Head ................................................................................ 3-5
3.2.3—Horizontal Loads .................................................................................................................................... 3-6
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3.3—DESIGN ........................................................................................................................................................... 3-6
3.3.1—General ................................................................................................................................................... 3-6
3.3.2—Allowable Stresses.................................................................................................................................. 3-7
3.3.3—Deflection ............................................................................................................................................... 3-7
3.3.4—Safety Factors for Form Accessories ...................................................................................................... 3-7
SECTION 4—TEMPORARY RETAINING STRUCTURES
4.1—GENERAL........................................................................................................................................................ 4-1
4.2—TYPES OF RETAINING STRUCTURES ....................................................................................................... 4-1
4.3—LATERAL EARTH PRESSURES ................................................................................................................... 4-1
4.3.1—Cantilever Walls ..................................................................................................................................... 4-2
4.3.1.1—Wall Movement Necessary for Active Pressures ......................................................................... 4-2
4.3.1.2—Active Pressures ........................................................................................................................... 4-2
4.3.1.3—At-Rest Pressures ......................................................................................................................... 4-3
4.3.1.4—Passive Pressures .......................................................................................................................... 4-4
4.3.2—Braced Excavations ................................................................................................................................ 4-5
4.3.3—Surcharge Pressures .............................................................................................................................. 4-13
4.4—STABILITY.................................................................................................................................................... 4-13
4.5—COFFERDAMS.............................................................................................................................................. 4-13
4.5.1—Cantilever Walls ................................................................................................................................... 4-13
4.5.2—Braced Cofferdams ............................................................................................................................... 4-14
APPENDICES
APPENDIX A—MAXIMUM DESIGN VALUES FOR UNGRADED STRUCTURAL LUMBER .................... A-1
APPENDIX B—AISC PROVISIONS FOR WEBS AND FLANGES WITH CONCENTRATED FORCES ....... B-1
B.1—Flange Local Bending .............................................................................................................................. B-1
B.2—Web Local Yielding ................................................................................................................................. B-1
B.3—Web Local Crippling ............................................................................................................................... B-2
B.4—Web Sideway Buckling............................................................................................................................ B-3
B.5—Web Compression Buckling .................................................................................................................... B-4
B.6—Web Panel Zone Shear ............................................................................................................................. B-4
B.7—Unframed Ends of Beams and Girders .................................................................................................... B-5
B.8—Additional Stiffener Requirements for Concentrated Forces ................................................................... B-5
B.9—Additional Doubler Plate Requirements for Concentrated Forces ........................................................... B-6
APPENDIX C—SELECT ASCE 7 WIND PROVISIONS ..................................................................................... C-1
C.1—Basic Wind Speed, V ............................................................................................................................... C-1
C.2—Design Wind Force, F .............................................................................................................................. C-1
C.3—Velocity Pressure Exposure Coefficient, KZ ............................................................................................ C-2
C.4—Topographic Factor, Kzt ........................................................................................................................... C-2
C.5—Wind Directionality Factor, Kd ................................................................................................................ C-3
C.6—Gust Effect Factor, G ............................................................................................................................... C-3
C.7—Force Coefficient, Cf ................................................................................................................................ C-3
C.8—Projected Area, Af .................................................................................................................................... C-3
APPENDIX D—SELECT ASCE 7 SEISMIC PROVISIONS ................................................................................ D-1
D.1—Risk-Targeted Maximum Considered Earthquake, MCER ....................................................................... D-1
D.2—Site Class and Site Coefficients, Fa and Fv .............................................................................................. D-1
D.3—Design Spectral Acceleration Parameters, SDS and SD1 ............................................................................ D-2
D.4—Estimate Fundamental Period of Falsework, Ta ...................................................................................... D-2
D.5—Seismic Response Coefficient, Cs ........................................................................................................... D-2
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REFERENCES ......................................................................................................................................................... R-1
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D.6—Seismic Base Shear and Equivalent Lateral Force, V and Feq ................................................................. D-2
APPENDIX E—SAMPLE WIND AND SEISMIC CALCULATIONS .................................................................. E-1
APPENDIX F—FOUNDATION INVESTIGATION AND DESIGN .................................................................... F-1
F.1—Subsurface Investigation .......................................................................................................................... F-1
F.2—Relative Density of Granular Deposits ..................................................................................................... F-1
F.3—Consistency of Cohesive Soils ................................................................................................................. F-2
F.4—Unified Soil Classification System ........................................................................................................... F-3
F.5—Potential Problem Soils ............................................................................................................................ F-4
F.6—Extended Foundation................................................................................................................................ F-5
F.7—AASHTO and ASTM Reference Standards ............................................................................................ F-5
APPENDIX G—CONVERSION OF EQUATIONS FROM US CUSTOMARY UNITS TO SI METRIC
UNITS ...................................................................................................................................................................... G-1
GUIDE DESIGN SPECIFICATION FOR BRIDGE TEMPORARY WORKS
Figure 4.3.2-1—Apparent Earth Pressure Distributions for Anchored Walls Constructed from the Top
Down in Cohesionless Soils ............................................................................................................................... 4-6
Figure 4.3.2-2—Apparent Earth Pressure Distributions for Anchored Walls Constructed from the Top
Down in Soft to Medium Stiff Cohesive Soils ................................................................................................... 4-7
Figure 4.3.2-3—Unfactored Simplified Earth Pressure Distributions for Permanent Non-Gravity
Cantilevered Walls with Discrete Vertical Wall Elements ................................................................................. 4-8
Figure 4.3.2-4—Unfactored Simplified Earth Pressure Distribution and Design Procedures for
Permanent Non-Gravity Cantilevered Walls with Continuous Vertical Wall Elements Embedded
in Granular Soil Modified after Teng (1962) ..................................................................................................... 4-9
Figure 4.3.2-5—Unfactored Simplified Earth Pressure Distributions for Temporary Non-Gravity
Cantilevered Walls with Discrete Vertical Wall Elements ............................................................................... 4-10
Figure 4.3.2-6—Unfactored Simplified Earth Pressure Distributions for Temporary Non-Gravity
Cantilevered Walls with Continuous Vertical Wall Elements .......................................................................... 4-11
Figure C.1(a)—Basic Wind Speeds for Occupancy Category II Buildings and Other Structures ............................ C-6
Figure C.1(b)—Basic Wind Speeds for Occupancy Category III and IV Buildings and Other Structures .............. C-8
Figure C.2—Topographic Multipliers for Exposure C ........................................................................................... C-10
Figure D.1(a)—S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion
Parameter for the Conterminous United States for 1.0 sec Spectral Response Acceleration
(5 Percent of Critical Dumping), Site Class B ................................................................................................... D-3
Figure D.1(b)—S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion
Parameter for the Conterminous United States for 1.0 sec Spectral Response Acceleration
(5 Percent of Critical Dumping), Site Class B ................................................................................................... D-4
Figure D.2—S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion
Parameter for Alaska for 1.0 sec Spectral Response Acceleration (5 Percent of Critical Dumping),
Site Class B ....................................................................................................................................................... D-5
Figure D.3—S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion
Parameter for Hawaii for 1.0 sec Spectral Response Acceleration (5 Percent of Critical Dumping),
Site Class B ....................................................................................................................................................... D-6
Figure D.4—S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion
Parameter for Puerto Rico and the United States Virgin Islands for 1.0 sec Spectral Response
Acceleration (5 Percent of Critical Dumping), Site Class B ............................................................................. D-7
Figure E.1—Falsework Tower Elevation ................................................................................................................. E-2
Figure E.2—Falsework Tower Elevation ................................................................................................................. E-7
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LIST OF FIGURES
GUIDE DESIGN SPECIFICATION FOR BRIDGE TEMPORARY WORKS
Table 2.1-1—Minimum Mechanical Properties of Structural Steel by Shape, Strength, and Thickness ............... 2-2
Table C2.2.2.2.1—Early ASTM Steep Specifications............................................................................................ 2-3
Table 2.3.2.2-1—Load Combinations and Load Factors ........................................................................................ 2-9
Table 2.3.4.3.3-1—Classes of Working Surfaces for Combined Uniformly Distributed Loads .......................... 2-13
Table 2.3.4.3.4-1—Minimum Concentrated Personnel and Equipment Loads .................................................... 2-13
Table 2.5.2-1—Presumptive Soil-Bearing Values................................................................................................ 2-23
Table 2.5.2-2—Ground Water-Level Modification Errors ................................................................................... 2-23
Table C3.1.2-1—Form Materials with Data Sources for Design and Specification ............................................... 3-2
Table 3.2.2.2-1—Chemistry Factor, Fc................................................................................................................... 3-6
Table 3.2.2.2-2—Unit Weight Factor, Fw ............................................................................................................... 3-6
Table 3.3.4-1—Minimum Safety Factors of Formwork ......................................................................................... 3-7
Table A.1—Maximum Design Values for Ungraded Structural Lumber ............................................................... A-1
Table C.1—Velocity Pressure Coefficient, Kz ........................................................................................................ C-3
Table C.2—Wind Directionality Factor, Kd ........................................................................................................... C-4
Table C.3—Force Coefficients for Trussed Towers, Cf ......................................................................................... C-4
Table C.4—Force Coefficients for Open Signs & Lattice Frameworks, Cf............................................................ C-4
Table C.5—Force Coefficients for Solid Freestanding Walls and Signs ................................................................ C-5
Table D.1— Site Coefficient, Fa ............................................................................................................................ D-1
Table D.2— Site Coefficient, Fv ............................................................................................................................ D-1
Table E.1—Velocity Pressure Exposure Coefficient.............................................................................................. E-3
Table E.2—Velocity Pressure at Each Height Zone ............................................................................................... E-3
Table E.3—Wind Pressure at Each Falsework Height Zone .................................................................................. E-4
Table E.4—Wind Load per Tower for Each Height Zone ...................................................................................... E-5
Table F.1—Determination of Relative Density Based on Standard Penetration Resistance .................................. F-2
Table F.2—CPT and SPT Values for Various Soils ............................................................................................... F-2
Table F.3—Consistency of Cohesive Soils ............................................................................................................ F-3
Table F.4—Soil Classification According to the United Soil Classification System ............................................. F-4
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LIST OF TABLES
ABBREVIATIONS
AASHTO
ACI
AISC
AISI
AITC
ANSI
APA
ASCE
ASTM
AWS
BOCA
FHWA
NAVFAC
NDS
NFPA
OSHA
PCI
SSFI
UBC
American Association of State Highway and Transportation Officials
American Concrete Institute
American Institute of Steel Construction
American Iron and Steel Institute
American Institute of Timber Construction
American National Standards Institute
American Plywood Association
American Society of Civil Engineers
American Society for Testing and Materials
American Welding Society
Building Officials & Code Administrators
Federal Highway Administration
Naval Facilities Engineering Command
National Design Specifications for Wood Construction
National Forest Products Association
Occupational Safety and Health Administration
Precast/Prestressed Concrete Institute
Scaffolding, Shoring and Forming Institute
Uniform Building Code
GENERAL NOTATION
in.
ft
plf
psi
ksi
psf
ksf
tsf
pcf
fps
hr
inches
feet
pounds per linear foot
pounds per square inch
kips per square inch
pounds per square foot
kips per square foot
tons per square foot
pounds per cubic foot
feet per second
hour
xi
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xii
SI* (MODERN METRIC) CONVERSION FACTORS
APPROXIMATE CONVERSIONS TO SI UNITS
Symbol When You Know
APPROXIMATE CONVERSIONS FROM SI UNITS
Multiply by
To Find
Symbol
Symbol When You Know
Multiply by
To Find
Symbol
LENGTH
0.039
3.28
1.09
0.621
inches
feet
yards
miles
in
ft
yd
mi
AREA
0.0016
10.764
1.195
2.47
0.386
square inches
square feet
square yards
acres
square miles
in2
ft2
yd2
ac
mi2
VOLUME
0.034
0.264
35.71
1.307
fluid ounces
gallons
cubic feet
cubic yards
fl oz
gal
ft3
yd3
ounces
pounds
short tons
(2000 lb)
oz
lb
T
in.
ft
yd
mi
inches
feet
yards
miles
LENGTH
25.4
0.305
0.914
1.61
millimeters
meters
meters
kilometers
mm
m
m
km
mm
m
m
km
millimeters
meters
meters
kilometers
in.2
ft2
yd2
ac
mi2
square inches
square feet
square yards
acres
square miles
AREA
645.2
0.093
0.836
0.405
2.59
square millimeters
square meters
square meters
hectares
square kilometers
mm2
m2
m2
ha
km2
mm2
m2
m2
ha
km2
square millimeters
square meters
square meters
hectares
square kilometers
mL
L
M3
m3
mL
L
m3
m3
milliliters
liters
cubic meters
cubic meters
g
kg
Mg
(or “T”)
g
kg
Mg
(or “T”)
grams
kilograms
megagrams
(or “metric ton”)
C
C
Celsius
temperature
lx
cd/m2
lx
cd/m2
lux
candela/m2
N
kPA
N
kPA
FORCE AND PRESSURE OR STRESS
newtons
0.225
poundforce
lbf
kilopascals
0.145
poundforce per lbf/in.2
square inch
VOLUME
fl oz
fluid ounces
29.57
milliliters
gal
gallons
3.785
liters
ft3
cubic feet
0.028
cubic meters
yd3
cubic yards
0.765
cubic meters
NOTE: Volumes greater than 1000 l shall be shown in m3.
MASS
28.35
0.454
0.907
oz
lb
T
ounces
pounds
short tons (2000
lb)
grams
kilograms
megagrams
(or “metric ton”)
F
Fahrenheit
temperature
TEMPERATURE (exact)
5(F-32)/9
Celsius
or (F-32)/1.8 temperature
fc
fl
foot-candles
foot-lamberts
ILLUMINATION
10.76
lux
3.426
candela/m2
FORCE AND PRESSURE OR STRESS
lbf
poundforce
4.45
newtons
lbf/in.2 poundforce per
6.89
kilopascals
square inch
MASS
0.035
2.202
1.103
TEMPERATURE (exact)
1.8C + 32
Fahrenheit
temperature
ILLUMINATION
0.0929
0.2919
foot-candles
foot-Lamberts
* SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. (Revised September 1993)
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F
fc
fl
PREFACE
Background
In 1991, a study was initiated by the Federal Highway Administration (FHWA) to identify the current state of practice
in the United States and abroad for designing, constructing, and inspecting the temporary works used to construct
highway bridge structures. This study was known as the FHWA Bridge Temporary Works Research Program. One of
the documents produced from this study was FHWA Publication No. FHWA-RD-93-032, Guide Design Specification
for Bridge Temporary Works, which was subsequently adopted by the American Association of State Highway and
Transportation Officials (AASHTO) in 1995.
Summary of Changes
This 2017 Second Edition of the AASHTO Guide Design Specifications for Bridge Temporary Works has been
updated to reflect current codes and practice. The organization is generally the same as the First Edition, but the
construction provisions have been moved to the AASHTO LRFD Bridge Construction Specifications. The format was
also changed so the commentary is adjacent to the specification (two column format) similar to the AASHTO LRFD
Bridge Construction Specifications. The loads in Section 2—Falsework have also been significantly revised and both
ASD and LRFD design specifications are included.
Acknowledgments
The AASHTO Guide Design Specifications for Bridge Temporary Works was revised under NCHRP Project 20-07/
Task 294 by Wiss, Janney, Elstner Associates, Inc., Northbrook, Illinois. John F. Duntemann was the Principal
Investigator. This project was directed by the NCHRP Task Group, which consisted of the following representatives:
Arthur W. D’Andrea, Louisiana Department of Transportation
Richard W. Dunne, Michael Baker Jr., Inc.
Shoukry Elnahal, Massachusetts Department of Transportation
Matthew Farrar, Idaho Transportation Department
Kenneth F. Hurst, Kansas Department of Transportation (Retired)
Paul V. Liles, Jr., Georgia Department of Transportation
Carmen Swanwick, Utah Department of Transportation
Sheila Rimal Duwadi, Federal Highway Administration
Jeffry Ger, Federal Highway Administration
Waseem Dekelbab, Transportation Research Board
Danna Powell, Transportation Research Board
The original guide design specification was developed under FHWA Contract No. DTFH61-91-C-00088. The project
was directed by the Scaffolding, Shoring, and Formwork Task Group of the FHWA, which consisted of the following
representatives:
James M. Stout, California Department of Transportation
Donald Flemming, Minnesota Department of Transportation
Nick Yaksich, Associated General Contractors
Kent Starwalt, American Road and Transportation Builders Association
Ramon Cook, The Burke Company
Robert Desjardins, Cianbro Corporation
xiii
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There have been several initiatives since original publication of the AASHTO Guide Design Specifications for Bridge
Temporary Works that have advanced the design and construction of the temporary works used in bridge construction.
The Structural Engineering Institute of the American Society of Civil Engineers (ASCE) developed SEI/ASCE 3702, a standard for design loads on structures during construction. Based upon the period of time that has elapsed since
the development of the original Guide Design Specification, and the development of other related standards over this
period of time, the reassessment and updating of the guide design specification seemed appropriate and necessary.
Richard F. Hoffman, McLean Contracting
Robert T. Ratay, Consulting Engineer
Sheila Rimal Duwadi, Federal Highway Administration
James R. Hoblitzell, Federal Highway Administration
Donald W. Miller, Federal Highway Administration
William S. Cross, Federal Highway Administration
Ian M. Friedland, Transportation Research Board
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Special recognition is extended to Robert G. Lukas and Safdar Gill, Ground Engineering Consultants, Inc.; Robert T.
Ratay, Consulting Engineer; Alan D. Fisher, Cianbro Corporation; William N. Nickas, Precast/Prestressed Concrete
Institute; William F. McEleney, The National Steel Bridge Alliance; L. Edwin Dunn, California Department of
Transportation (retired); Peter Courtois, Dayton-Superior Corporation (deceased); Mark K. Kaler, Dayton-Superior
Corporation; and Donald F. Meinheit, Jon F. Sfura, Raymond H.R. Tide, Joseph M. Toniolo, Penny S. Sympson, and
Holly L. Ryan of Wiss, Janney, Elstner Associates, Inc. for their review comments, assistance with the research, and
preparation of this document.
xiv
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Section 1
1.1—SCOPE
C1.1
This Guide Design Specification has been developed
for use by state agencies to include in their existing
standard specifications for falsework, formwork, and
related temporary construction used to construct highway
bridge structures. The specification should also be useful
to bridge engineers, falsework designers, contractors, and
other engineers. Sections within this specification address
falsework, formwork, and temporary retaining structures.
Related publications and definitions are identified below.
The AASHTO Guide Design Specification for Bridge
Temporary Works was first published in 1995. This
specification was originally developed by Wiss, Janney,
Elstner Associates, Inc., of Northbrook, Illinois with the
FHWA and directed by the Scaffolding, Shoring and
Formwork Task Group of the FHWA. These
specifications provided unified design and construction
criteria that reflected the best practices at the time the
specifications were developed.
Since 1995, there have been several initiatives that
have advanced the state of practice related to the design
and construction of the temporary works used in bridge
construction. ASCE developed SEI/ASCE 37, Design
Loads on Structures during Construction.
This 2017 Second Edition of the AASHTO Guide
Design Specifications for Bridge Temporary Works has
been updated to reflect current codes and practice. The
organization is generally the same as the First Edition,
but the construction requirements have been moved to
the
AASHTO
LRFD
Bridge
Construction
Specifications. The loads in Section 2—Falsework have
also been significantly revised and both ASD and LRFD
design specifications are included. These documents—
the design and construction specifications—complement
each other. The AASHTO Construction Handbook for
Bridge Temporary Works has also been updated and
serves as a useful reference on this subject.
1.2—RELATED PUBLICATIONS
American Association of State Highway and
Transportation Officials, AASHTO LRFD Bridge
Construction Specifications, Third Ed., with 2010, 2011,
2012, 2014, 2015, and 2016 Interim Revisions,
Washington, DC, 2010.
American Association of State Highway and
Transportation Officials, AASHTO LRFD Bridge Design
Specifications, Seventh Ed., with 2015 and 2016 interim
revisions, Washington DC, 2014.
American Association of State Highway and
Transportation Officials, Construction Handbook for
Bridge Temporary Works, Second Edition, Washington,
DC, 2017.
American Association of State Highway and Transportation
Officials, Standard Specifications for Highway Bridges, 17th
Ed., Washington, DC, 2002.
1-1
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INTRODUCTION
1-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
American Society of Civil Engineers, Minimum Design Loads
for Buildings and Other Structures (ASCE 7-10), Reston,
Virginia, 2010.
American Society of Civil Engineers, Design Loads on
Structures During Construction (ASCE 37-02), American
Society of Civil Engineers, Reston, VA, 2002.
Duntemann, J.F., Dunn, L.E., Gill, S., Lukas, R.G., and Kaler,
M.D., Guide Design Specification for Bridge Temporary
Works, Report No. FHWA-RD-93-032, Federal Highway
Administration, Washington, DC, November 1993.
Duntemann, J.F., Calabrese, F., and Gill, S., Construction
Handbook for Bridge Temporary Works, Report No. FWHARD-93-034. Federal Highway Administration, Washington,
DC, November 1993.
Duntemann, J.F., Anderson, N.S., and Longinow, A.,
Synthesis of Falsework, Formwork, and Scaffolding for
Highway Bridge Structures, Report No. FHWA-RD-91-062,
Federal Highway Administration, Washington, DC,
November 1991.
United States Department of Transportation, Federal
Highway Administration, Accelerated Bridge Construction—
Experience in Design, Fabrication, and Erection of
Prefabricated Bridge Elements and Systems, Report No.
FHWA-HIF-12-013, Federal Highway Administration, East
Hartford, CT, 2011.
U.S. Department of Transportation, Federal Highway
Administration, Certification Program for Bridge Temporary
Works
(FHWA-RD-93-033),
Federal
Highway
Administration, Washington, DC, 1993.
U.S. Department of Transportation, Federal Highway
Administration, Standard Specifications for Construction of
Roads and Bridges on Federal Highway Projects, FP-03,
Washington, DC, 2003.
1.3—DEFINITIONS
For the purposes of this specification, the following
definitions apply:
Cofferdam—A watertight structure that allows foundations
to be constructed under dry conditions.
Engineer—Used with a capital “E” refers to the owner’s
engineer.
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Falsework—Temporary construction used to support the
permanent structure until it becomes self-supporting.
Falsework includes steel or timber beams, girders, columns,
piles, and foundations, and any proprietary equipment
including modular shoring frames, post shores, and horizontal
shoring.
Formwork—A temporary structure or mold used to retain the
plastic or fluid concrete in its designated shape until it hardens.
Formwork must have enough strength to resist the fluid
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SECTION 1: INTRODUCTION
1-3
pressure exerted by plastic concrete and any additional fluid
pressure effects generated by vibrations.
Scaffolding—An elevated work platform used to support
workmen materials and equipment, but not intended to
support the structure being constructed.
Shoring—A component of falsework such as horizontal,
vertical, or inclined support members. For the purpose of
this document, this term is used interchangeably with
falsework.
Temporary Retaining Structure—For the purpose of this
document, refers to both earth-retaining structures and
cofferdams.
1.4—METRIC CONVERSIONS
Conversion of equations from U.S. Customary units to
S.I. units is provided in Appendix G.
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Section 2
FALSEWORK
2.1—FALSEWORK DRAWINGS
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All elements of the falsework system shall be shown
on working drawings, hereinafter referred to as falsework
drawings. The falsework drawings shall include the
information and details necessary to construct the
falsework without reference to any supplemental drawing,
calculation sheet, design standard, or other source or
reference document.
The falsework drawings shall include all designcontrolling dimensions, including beam length, beam
spacing, post location and spacing, vertical distance
between connections in diagonal bracing, height of
falsework bents, and similar dimensions controlling
falsework design and erection.
The falsework drawings shall include a superstructure
placing diagram, which shall show the concrete placing
sequence, placement rate, and all construction joint
locations, if not included in or different from contract
plans.
When footing-type foundations are to be used, the soilbearing value assumed in the design shall be shown on the
falsework drawings.
When pile-type foundations are to be used, and the
vertical distance between the ground line and the top of the
pile will equal or exceed four times the pile diameter at the
ground line, the falsework drawings shall show the
maximum horizontal distance that the top of a falsework
pile may be pulled to its position under the cap, and the
maximum allowable deviation of the top of the pile, in its
final position, from a vertical line through the calculated
point of fixity of the pile or the unloaded pile alignment.
The anticipated total settlement of the falsework and
forms shall be shown on the falsework drawings. The
anticipated settlement shall include both foundation
settlement and joint take-up, and shall not exceed 1 in.
The falsework drawings shall show the method by
which the falsework may be adjusted vertically and the
locations where such adjustments will be reinforced.
Where openings through the falsework are required to
permit the passage of public traffic, including pedestrian
traffic, the falsework drawings shall show the location of
the all such openings, including horizontal and vertical
clearances and the location of temporary railing.
Where temporary bracing is to be used during erection
and removal of falsework over or adjacent to public traffic,
the falsework drawings shall show the sequence of erection
and removal and details of the temporary bracing system to
be used.
2-1
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2-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Table 2.1-1—Minimum Mechanical Properties of Structural Steel by Shape, Strength, and Thickness
AASHTO
Designation
M 270M/
M 270
Grade 36
M
270M/
M 270
Grade 50
M 270M/
M 270
Grade 50S
M 270M/
M 270
Grade
50W
M 270M/
M 270
Grade HPS
50W
M 270M/
M 270
Grade HPS
70W
M 270M/
M 270
Grade HPS 100W
Equivalent
ASTM
Designation
A709/
A709M
Grade 36
A709/
A709M
Grade 50
A709/
A709M
Grade
3650S
A709/
A709M
Grade
50W
A709/
A709M
Grade HPS
50W
A709/
A709M
Grade HPS
70W
A709/
A709M
Grade HPS 100W
Thickness of
Plates (in.)
Up to 4.0
incl.
Up to 4.0
incl.
Not
Applicable
Up to 4.0
incl.
Up to 4.0
incl.
Up to 4.0
incl.
Up to 2.5
incl.
Over 2.5 to
4.0 incl.
Shapes
All
Groups
All
Groups
All Groups
All
Groups
Not
Applicable
Not
Applicable
Not
Applicable
Not
Applicable
Minimum
Tensile
Strength,
Fu, (ksi)
58
65
65
70
70
85
110
100
Specified
Minimum Yield
Point or
Specified
Minimum Yield
Strength, Fy,
(ksi)
36
50
50
50
50
70
100
90
The falsework drawings, when submitted to the
owner, shall be accompanied by one set of the design
calculations. The calculations shall show the stresses and
deflections in load-supporting members. The drawings
and calculations shall be stamped and signed by a
Licensed Professional Engineer, registered in the state
where the falsework is to be erected.
2.2—MATERIALS AND MANUFACTURED
COMPONENTS
2.2.1—General
Falsework design may be based on the use of either
new or used materials and manufactured components, or
a combination thereof.
2.2.2—Structural Steel
2.2.2.1—Identification and Properties
New structural steel shall conform to the AASHTO
or ASTM specifications designated in Table 2.1-1. The
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Conversion: 1 ksi = 6.89 N/mm2
SECTION 2: FALSEWORK
2-3
most recent date of issue shall apply to each of these
specifications.
Certified material test reports (CMTR) or certified
reports of tests made by the fabricator or a testing
laboratory in accordance with ASTM A6/A6M or
A568/A568M, as applicable, and the governing
specification shall constitute sufficient evidence of
conformity with one of the above standards. Additionally,
the fabricator shall, if requested, provide an affidavit
stating that the structural steel furnished meets the
requirements of the grade specified.
For new structural steel, the design working stresses
shall not exceed those specified in the AISC Steel
Construction Manual. For structural steel design, the
modulus of elasticity, E, shall be assumed as 29,000 ksi.
2.2.2.2 —Salvaged Steel
C2.2.2.2
Used structural steel, which satisfies ASTM A6/A6M
criteria for surface imperfections, may be used at the
allowable working stresses for new material, provided the
grade of steel can be identified to the owner’s satisfaction.
The specification allows the use of both new and
salvaged structural steel. Salvaged (used) steel is
subject to the same ASTM A6/A6M criteria for
surface imperfections as new steel. For reference,
some of the more common steel designations
predating ASTM A36 are provided in Table
C2.2.2.2-1.
Table C2.2.2.2-1 Early ASTM Steel Specifications
ASTM Requirement
Date
Specification
ASTM A7
1924–1931
ASTM A9
Remark
Tensile Strength (ksi)
Minimum Yield Point (ksi)
Structural Steel
55 to 65
1
Rivet Steel
46 to 56
1
Structural Steel
55 to 65
1
Rivet Steel
46 to 56
1
/2 T.S. or not less than 30
/2 T.S. or not less than 25
/2 T.S. or not less than 30
/2 T.S. or not less than 25
/2 T.S. or not less than 33
1939–1948
ASTM A7-A9
Structural Steel
60 to 72
1
1939–1949
ASTM A141-39
Rivet Steel
52 to 62
1
2.2.2.3—Welding
/2 T.S. or not less than 28
C2.2.2.3
All provisions of the Structural Welding Code, ANSI/
AWS D1.1/D1.1M, of the American Welding Society, as
appropriate, apply to work performed under this
specification with exceptions as noted below:
--`,,,`,,`,`,`,`,`,,`,,,-`

AISC Steel Construction Manual Section J1.6 in lieu
of ANSI/AWS D1.1/D1.1M Section 5.17.1

AISC Steel Construction Manual Section J2.2a in lieu
of ANSI/AWS D1.1/D1.1M Section 2.3.2

AISC Steel Construction Manual Table J2.2 in lieu of
ANSI/AWS D1.1/D1.1M Table 2.1

AISC Steel Construction Manual Table J2.5 in lieu of
ANSI/AWS D1.1/D1.1M Table 2.3
While it is recognized that many provisions of the
Structural Welding Code, ANSI/AWS D1.1/D1.1M
may not be applicable to falsework construction, the
intent of Section 2.2.2.3 is to require the same quality
of workmanship for temporary works as for permanent
construction. The noted exceptions are the same as
those found in the AISC Steel Construction Manual.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS

AISC Steel Construction Manual Appendix 3, Table
A-3 in lieu of ANSI/AWS D1.1/D1.1M Table 2.4

AISC Steel Construction Manual Section B3.9 and
Appendix 3 in lieu of ANSI/AWS D1.1/D1.1M
Section 2, Part C

AISC Steel Construction Manual Section M2.2 in lieu
of ANSI/AWS D1.1/D1.1M Sections 5.15.4.3 and
5.15.4.4
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
2-4
2.2.3—Wood
2.2.3.1—Allowable Stresses
All species and grades of wood to which allowable unit
stresses have been assigned in the National Design
Specification (NDS) for Wood Construction are acceptable
for use in falsework.
Design working stresses for new lumber shall not
exceed the design values for visually graded dimension
lumber and visually graded timbers as tabulated in the
National Design Specification (NDS) for Wood
Construction. The listed values are for normal load duration
and dry service conditions (unless noted otherwise), and shall
be modified as provided herein.
2.2.3.2—Modification Factors
Modification factors for service conditions and duration
of load shall be as prescribed by the NDS. All modification
factors are cumulative.
Load duration factors shall not apply to values for
modulus of elasticity or compression perpendicular to the
grain.
2.2.3.3—Used Lumber
Subject to the owner’s concurrence, used lumber of
known species may be used in accordance with the
following:
(a) Where the grade is known or can be established, the
stress level for used lumber, in good condition and
without obvious defects, shall not exceed the adjusted
allowable stress for new lumber of that grade and
species.
C2.2.3.2
Since falsework is seldom subjected to maximum
loading for more than seven days, a load duration factor
of 1.25 will be applicable to most falsework designs. In
the case of loads of shorter duration, such as wind, a
larger factor is appropriate. The load duration factor for
connections is limited to 1.6 in the NDS. Connections
resisting impact loading, such as the connection at the
base of a falsework post adjacent to a traffic opening,
shall not use a load duration factor larger than 1.6.
C2.2.3.3—Used Lumber
The maximum design values for ungraded structural
lumber tabulated in Appendix A are based on the lowest
stresses for each size classification. These are applicable
only for normal load duration and dry surface conditions,
unless noted otherwise. Refer to the NDS Supplement—
Design Values for Wood Construction for a description
of applicable adjustment factors and species designation.
(b) Where the grade is unknown and cannot be established,
the stress level for used lumber, in good condition and
without obvious defects, shall not exceed the adjusted
allowable stresses as listed in Appendix A.
(c) The stress level for used lumber of lower quality or
showing evidence of abuse shall not exceed the stress
values for the species as listed in Appendix A. The listed
stress values are maximums and shall not be increased
by size factors.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
SECTION 2: FALSEWORK
2-5
Unless otherwise permitted by the owner, the allowable
stress values for lumber of unknown species shall not exceed
the lowest allowable stress values of any species listed in
Appendix A for a particular size classification. Said stresses
are maximums and shall not be increased by application of
load duration or other stress-adjustment factors. The owner
may require any lumber proposed for use under paragraphs
(a) or (b) above to be regraded prior to use.
2.2.4—Other Materials
The design of materials other than structural steel and
timber shall conform to the applicable design standard or
specification for such material.
2.2.5—Manufactured Components
2.2.5.1—General
C2.2.5.1
As used herein, manufactured components include
the following classes of proprietary products:

Vertical shoring systems including tubular welded
frame shoring, tube and coupler shoring, and
components thereof.

Manufactured assemblies including single-post
shores, brackets, jacks, joists, clamps, and similar
devices manufactured for commercial use.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
2.2.5.2—Maximum Loadings and Deflections
The maximum load to be used on any manufactured
component, under any load sequence or combination,
shall not exceed the manufacturer’s recommendations.
When requested by the owner, a manufacturer’s
catalog, technical bulletin, or similar publication shall be
furnished with the falsework drawings showing the use of
manufactured components. The information furnished
shall include, but not be limited to, test data and
limitations and conditions governing the use of the
component.
The dead load deflection of a manufactured
component designed for use in a horizontal or inclined
position shall not exceed 1 ∕240 of the span length under the
weight of the concrete only.
The use of a manufactured assembly for which no
engineering data is furnished will not be permitted, unless
the assembly has been tested under the falsework design.
Vertical shoring systems consist of individual
components that may be assembled and erected in place
to form a series of internally braced steel towers of any
desired height. Safe working loads for these shoring
systems are generally determined empirically by fullscale load tests, where the ultimate capacity is based upon
uniform and concentric loading of the tower legs.
Therefore, the shoring capacity published by the
manufacturer should be considered the maximum load
that the shoring is able to safely support under ideal
loading conditions. Horizontal loads, eccentricity due to
unequal spans or an unbalanced pouring sequence, and
uneven foundation settlement generally will have an
adverse effect on the vertical shoring assembly and
warrant special consideration.
Manufactured assemblies are commercial products
such as jacks, hangers, brackets, and similar items, the
use of which is governed by conditions or limitations
imposed by the manufacturer. When approved for use,
these products become an identifiable component of the
falsework system.
C2.2.5.2
The specifications limit the load or the deflection
or both, of any commercial product to the maximum
recommended or allowed by the manufacturer. The
manufacturer’s recommendation should be shown in a
catalog or design manual published by the
manufacturer, or in a statement of compliance
pertaining to a particular project.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
2-6
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
The working load for such assemblies shall not exceed
40 percent of the maximum load sustained during the test.
2.2.5.3—Factor of Safety
The factor of safety for vertical shoring systems shall
not be less than 2.5. This shall be clearly evident from a
catalog or other engineering data furnished by the
manufacturer.
The factor of safety for jacks that are not a part of a
shoring system, and all types of manufactured assemblies,
shall not be less than the minimum factor of safety
required by the industry standard for the particular device,
and in no case shall the factor of safety be less than 2.0.
2.3.1—General
C2.3.1
The falsework design load shall consist of the sum of
the dead and live vertical loads and a horizontal load.
The vertical design load shall consist of the sum of
the dead and live vertical loads, including live load impact
where appropriate.
The horizontal design load shall consist of the sum of
any actual horizontal loads due to equipment, construction
sequence, or other causes, excluding the specified wind
load, but in no case shall the horizontal design load be less
than 2 percent of the total dead load to be supported at the
point under consideration.
Pursuant to the provisions in Section 2.3.2, the
vertical and horizontal design loads shall be increased as
necessary to account for the effect of load redistribution
due to prestressing, shrinkage, or other causes.
If the effect of a particular loading condition cannot
be determined at the falsework design stage, the design
shall be based on an assumed loading condition. In such
cases the assumptions shall be reviewed when the actual
conditions become known, and the falsework design
revised if necessary.
The minimum lateral load is intended to ensure
that sufficient horizontal load capacity is available so
that the falsework remains stable under normal
conditions, when environmental lateral loads are not
present. The horizontal design load should be
considered separately in both the transverse and
longitudinal directions.
For post-tensioned construction, it is generally
recognized that redistribution of gravity loads occurs
after the superstructure is prestressed. The distribution
of load in the falsework after post-tensioning is
dependent on factors such as spacing and stiffness of
falsework
supports,
foundation
stiffness,
superstructure stiffness, and tendon profile. The
amount of load redistribution can be significant and
may be a governing factor in the falsework design.
Overall temperature variations result in
contraction or expansion. The induced forces must be
resisted or the movement accommodated by the
falsework.
2.3.2—Loads and Load Combinations
2.3.2.1—Loads and Load Designation
The following loads shall be considered:
D
CD
CFML
CVML
CP
CH
CR
CC
EH
PS
SH
LL(or LS)
I
=
=
=
=
=
=
=
=
=
=
=
=
=
dead load
construction dead load
fixed material load
variable material load
personnel and equipment loads
horizontal construction load
equipment reactions
lateral pressure of concrete
horizontal earth pressure load
secondary forces from post-tensionin
force effects due to shrinkage
live load
impact load
C2.3.2.1
The loads are only defined by name and symbol
in this section. The definition of each load is in
subsequent sections. Additional construction and
environmental loads may include (and be accounted
for in the load combinations) such items as
prestressing, rib shortening, buoyancy, and others as
appropriate.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
2.3—LOADS
SECTION 2: FALSEWORK
CE
TG (or TU)
WS
EQ
S
R
WA
IC
WI
SE
=
=
=
=
=
=
=
=
=
=
2-7
centrifugal force
thermal loads
wind load
earthquake load
snow load
rain load
stream flow
ice load
wind load on ice
force effect due to settlement
The specified loads are nominal loads which are
intended to be suitable for use in either Load and
Resistance Factor Design (LRFD) or Allowable Stress
Design (ASD), provided that appropriate load factors and
combinations are used.
2.3.2.2—Load Combinations and Load Factors
The total factored force affect shall be taken as:
(2.3.2.2-1)
𝑄𝑄 = Σ𝛾𝛾𝑖𝑖 𝑄𝑄𝑖𝑖
where:
𝑄𝑄𝑖𝑖
𝛾𝛾𝑖𝑖
=
=
force effects from loads specified herein
load factors specified in Table 2.3.2.2-1
C2.3.2.2
The selection of load factors is intended to be
compatible with ASCE 7. Since little independent
research has been done, the load factor 2.0 is suggested
for those loads that may vary substantially, or about
which we have little information.
The loads suggested herein for consideration in load
combinations are not all-inclusive; therefore, their
selection will require judgment in many situations.
Design should be based on the load combination causing
the most unfavorable effect. In some cases, this may
occur when one or more loads are not applied
simultaneously. Furthermore, the critical load effect may
result from the application of one or more loads on only
part of the structure. Finally, concentrated loads may be
applied in place of or in addition to the assumed
uniformly distributed loads.
Load combinations should be considered based on
the specific type of construction and procedures.
Consideration should be given to construction loads
which may be mutually exclusive, strongly correlated, or
which occur with such a low probability that they may
effectively be neglected.
Environmental loads are considered in a similar way
as in ASCE 7. However, the following differences for
environmental loads during construction must be kept in
mind: (1) modifications to the design load values for the
possibility of a reduced exposure period may be
appropriate, (2) certain loads may be disregarded for
most practical purposes because of the generally very
short reference period associated with typical
construction projects, and (3) certain loads in
combinations may effectively be ignored because of the
practice to shut-down construction sites during these
events (i.e., snow and wind, snow and certain equipment
forces, extreme winds and personnel loads, etc.).
Regional and project-specific conditions should be
considered when deciding which combinations of
environmental and structural loads to use.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
2-8
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
2.3.2.3—Load and Resistance Factor Design
Loads shall be combined to obtain the maximum design
load effects for members and systems.
The most unfavorable effects from both wind and
earthquake loads shall be considered, where appropriate, but
they need not be assumed to act simultaneously. Similarly,
CH need not be assumed to act simultaneously with wind or
seismic loads. Lateral earth pressure, environmental loads,
and other construction loads shall be considered when
applicable using the load factors in Table 2.3.2.2-1.
Where the effect of one load is partially or wholly
resisted by another load, the factor on the resisting load shall
be taken as zero for variable loads and 0.9 for controlled
loads.
A controlled load is a material that is placed in a specific
location to counteract the effect of a specific load.
C2.3.2.3
The load factors provided herein are intended to
reflect the relative uncertainty in the particular action.
This uncertainty can arise from: (1) inherent or natural
variability, (2) range of applications, and (3) possibilities
for misuse or error. It may therefore be reasonable to
make certain modifications to load factors in the presence
or absence of additional information.
Factors on heavy equipment reactions are for
maximum load values only. The load factor is much
lower (1.6) when the equipment is rated such that the
reactions are specified by the manufacturer or is
otherwise known. Also, in the event any equipment is
used which generates dynamic loads (i.e., pumps,
unbalanced rotors), the load effect must be determined
separately first and then multiplied by a factor of 1.3.
OSHA requires that “each scaffold and scaffold
component shall be capable of supporting, without
failure, its own weight and at least four times the
maximum intended load applied or transmitted to it.”
ANSI has a similar requirement. In order to satisfy this
OSHA criterion, the load factor for personnel and
equipment load, CP, fixed material load, CFML, and
variable material load, CVML, should be 4.0 and the load
factor for construction dead load, CD, should be 1.0.
However, assuming CD = 1.0 may be unconservative in
cases where the dead load is high relative to the total load.
Also, capacity reduction factors (ϕ factors) used with
these load factors should be 1.0.
The applicable resistance factors can be determined
in the related codes and standards. The designer should
be aware that temporary structures used repeatedly are
subject to abuse and loss of capacity, and that ϕ factors
may need to be lower than those used for ordinary
strength design to compensate for this loss of capacity.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
Allowable Stress Design
Load and Resistance Factor Design
Load Combination
Limit State
LRFD
1
LRFD
2
LRFD
3
LRFD
4
LRFD
5
LRFD
6
LRFD
7
LRFD
8
LRFD
9
LRFD
10
LRFD
11
LRFD
12
LRFD
13
LRFD
14
LRFD
15
ASD
1
ASD
2
ASD
3
ASD
4
ASD
5
ASD
6
ASD
7
ASD
8
ASD
9
ASD
10
ASD
11
ASD
12
ASD
13
ASD
14
ASD
15
Notes:
CD
1.4
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
0.9
0.9
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
CFML
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
0.0
0.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
0.0
0.0
CVML
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
0.0
0.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
0.0
0.0
CRa
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
1.6/2.0
0.0
0.0
0.0
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
1.0/1.2
0.0
0.0
0.0
CCb
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
1.3/1.5
0.0
0.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
0.0
0.0
PS
SH
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
TG
TU
0.0
1.0
1.0
1.0
1.0
1.0
1.2
1.2
1.0
1.0
1.0
1.0
0.0
0.0
0.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
0.0
0.0
EH c
0.0
γEH
γEH
γEH
γEH
γEH
γEH
γEH
γEH
γEH
γEH
0.0
γEH
γEH
γEH
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
WS
0.0
0.0
0.0
0.0
0.0
0.0
0.5
0.5
1.0
1.0
0.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.6
0.0
0.45
0.45
0.0
0.6
0.0
0.0
EQ
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.7
0.0
0.0
0.53
0.0
0.0
0.7
S
0.0
0.5
0.0
0.5
1.6
0.0
1.6
0.0
0.5
0.0
0.5
0.2
0.0
0.0
0.0
0.0
0.0
1.0
0.0
1.0
0.75
0.0
0.0
0.0
0.75
0.0
0.75
0.0
0.0
0.0
R
0.0
0.0
0.5
0.0
0.0
1.6
0.0
1.6
0.0
0.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
0.75
0.0
0.0
0.0
0.75
0.0
0.0
0.0
0.0
WA
1.4
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
0.0
0.0
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
0.0
1.0
IC
0.0
0.0
0.0
0.2
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
1.0
0.0
0.0
0.7
0.0
0.0
0.7
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.7
0.0
WI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.7
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.7
0.0
SE d
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
1.0/0.0
For LFRD, CR = 1.6 for rated equipment and CR = 2.0 otherwise; for ASD, CR = 1.0 for rated equipment and CR = 1.2 otherwise.
For LFRD, CC = 1.3 for full fluid head condition and CC = 1.5 otherwise.
Where the effect of EH adds to the primary variable load effect, γEH = 1.6; where the effect of EH resists the primary variable and the load is permanent, γEH = 0.9; for all other conditions, γEH = 0.0.
Load Cases which include settlement shall also be applied without settlement.
OSHA requires that scaffolds shall be capable of supporting, without failure, “their own weight and at least four times the maximum intended load.” Where required to satisfy this criterion, CP=1.0, CFML=1.0, CVML=4.0, and CD=1.0. See
C2.3.2.3 for additional information.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
2-9
a.
b.
c.
d.
e.
D
1.4
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
0.9
0.9
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.6
0.6
0.6
LL
LS
I
CE
CP
CH
0.0
1.6
1.6
1.6
1.0
1.0
0.0
0.0
1.0
1.0
1.0
1.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
0.0
0.75
0.75
0.0
0.0
0.75
0.75
0.75
0.0
0.0
0.0
SECTION 2: FALSEWORK
Table 2.3.2.2-1—Load Combinations and Load Factors
2-10
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
2.3.2.4—Allowable Stress Design
Loads shall be combined to obtain the maximum
design load effects for members and systems.
The most unfavorable effects from both wind and
earthquake loads shall be considered where appropriate,
but they need not be considered simultaneously.
Similarly, CH need not be assumed to act simultaneously
with wind or seismic loads.
When structural effects due to two or more variable
loads in combination with dead load are investigated in
load combinations of Section 2.3.2.2, the combined
effects shall comply with both of the following
requirements: (a) the combined effects due to the two or
more variable loads multiplied by 0.75 plus effects due to
dead loads shall not be less than the effects from the load
combination of the dead load plus the load producing the
largest effects; and (b) the allowable stress shall not be
increased to account for these combinations.
Where the effect of one load is partially or wholly
resisted by another load, the factor on the resisting load
shall be taken as zero for variable loads and 0.60 for
controlled loads.
C2.3.2.4
Designers are cautioned against mixing ASD and
LRFD load combinations.
OSHA requires that “Each scaffold and scaffold
component shall be capable of supporting, without
failure, their own weight and at least four times the
maximum intended load applied or transmitted to it.”
ANSI has a similar requirement. ASD ordinarily
provides for safety factors somewhat less than 2; thus, in
order to satisfy the OSHA criteria, the superimposed
design loads effectively need to be more than doubled.
The designer should be aware that temporary
structures used repeatedly are subject to abuse and loss
of capacity and that safety factors may need to be higher
than those used for ordinary ASD to compensate for this
loss of capacity.
2.3.3 —Dead and Live Loads
2.3.3.1—Dead Load
C2.3.3.1
The dead load, for the purposes of this standard, is the
weight of the permanent construction in place at the
particular time in the construction sequence that is under
consideration. The dead load includes all construction in
place that is temporarily shored or braced. It includes
construction whose primary structural system is complete,
but which is being used to support construction materials
and construction equipment. The weights of scaffolding,
shoring, concrete forms, runways for construction
equipment, and other temporary structures are not
included; these loads are considered to be construction
dead load, CD, as defined in Section 2.3.4.1.
The combined weight of concrete, reinforcing and
prestressing steel, and formwork shall be assumed to be
not less than 160 pcf for normal concrete or 130 pcf for
lightweight concrete.
2.3.3.2—Live Load
The contractor usually controls the sequence of
construction and thus controls what loads will be on the
structure at the various construction stages. The design
of temporary shoring and bracing must include these
dead loads as well as the temporary loads described in
this specification.
C2.3.3.2
The live load may vary at different stages of
construction. The live loads shall include impact,
longitudinal forces from vehicles, centrifugal forces from
vehicles, and wind loads on vehicles, as applicable.
The live loads during construction may be different
than the live loads applied on the completed structure.
For example, during reconstruction of a bridge designed
for trucks, a lane may be restricted to cars, resulting in a
lower live load. Reduction of the live load from the final
design value shall not be made unless the actual loads are
strictly monitored and enforced.
The partially completed structure should expose the
occupants or users to no greater risk than inherent in the
codes and standards of practice that pertain to the
completed structure.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
© 2017 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
Order Number: 02250056
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Not for Resale,2019-08-14 12:03:30 UTC
SECTION 2: FALSEWORK
2-11
2.3.3.2.1—Construction Live Load
The construction live load shall consist of the actual
weight of any equipment to be supported applied as
concentrated loads at the points of contact, plus a uniform
load of 20 psf applied over the area supported, plus 75 plf
applied at the outside edge of deck overhangs.
2.3.3.2.2—Impact
C2.3.3.2.1
Construction live loads are inherently transient and,
therefore, for a given falsework scheme the potential
combinations of these loads should be considered.
In bridge deck construction, a concentration of live
load generally occurs at or near the edge of the bridge
deck during concrete placement and finishing. The guide
specifications include a 75 plf live load applied along the
outside edge of all deck overhangs to account for this
loading. In the case of long falsework spans, however,
the application of 75 plf to falsework components below
the overhang support system may be unduly
conservative. Therefore, it is recommended that the 75
plf be applied as a moving load over a length of 20 ft.
and positioned to produce the maximum stress in the
underlying falsework component being considered.
C2.3.3.2.2
When impact can occur, the design load to be applied to
steel members and manufactured components shall be
increased as provided herein.

For members and components subject to impact during
placing operations, the design dead load shall be
increased by an impact factor of not less than 30 percent
of the weight of the material being placed.

For members and components subject to impact during
lifting operations, the static load due to the payload shall
be increased by not less than 30 percent for
mechanically operated lifting equipment and not less
than 15 percent for manually operated lifting equipment.

If motorized carts are used, the uniform live load shall
be increased an additional 25 psf.
The allowance for impact assumes normal care in the
placing of structural elements. It is not intended to cover
excessive impact loads resulting from dropping materials
onto the falsework or dragging structural elements into
position.
2.3.3.3—Minimum Vertical Load
The minimum total design vertical load for any
falsework member shall be not less than 100 psf for the
combined dead and live load, exclusive of any increase for
impact, regardless of slab thickness.
2.3.4—Construction Loads
Construction loads are loads imposed on a partially
completed or temporary structure during and as a result of the
construction process. Construction loads include, but are not
limited to, materials, personnel, and equipment imposed on the
temporary or permanent structure during the construction
process.
2.3.4.1—Construction Dead Load
The construction dead load shall consist of the dead load
of temporary structures that are in place at the stage of
construction being considered. The dead load of the permanent
structure, either partially complete or complete, is not
included.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
2-12
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
The dead load of the permanent structure is defined in
Section 2.3.3.1.
2.3.4.2—Material Loads
The material dead loads consist of two categories:


Fixed material loads (CFML)
Variable material loads (CVML)
Fixed material loads (CFML) are loads from materials that
are fixed in magnitude. Variable material loads (CVML) are
loads from materials that vary in magnitude during the
construction process. If the local magnitude of a material load
varies during the construction process, then that load shall be
considered as a variable material load.
C2.3.4.2
This section separates material dead loads into two
categories: CFML and CVML. CFML and CVML are separated to
permit the use of an appropriate load factor for each category
in strength design. This approach recognizes the difference in
the variability of the load between the two categories.
This section addresses the loads from materials and is
not intended to apply to equipment loads. Personnel and
equipment loads are considered separately in Section 2.3.4.3.
Material loads may be either distributed or concentrated
loads. The designer must consider the pattern of uniformly
distributed loads and the location of concentrated loads that
create the most severe strength and/or serviceability
condition.
The designer must determine whether the superimposed
material load during the construction process is essentially
fixed in magnitude, is variable, or can be adjusted during the
construction process. For example, the load from formwork
becomes a CFML once it is installed, while the load created by
the concrete during fresh concrete placement is considered a
CVML. The load due to concrete placement is considered a
variable material load since fresh concrete can be piled higher
than the finished thickness of the slab.
The distinction between a CFML and a CVML is not
location or position on the structure, rather it is the variability
of the loading magnitude.
The stockpiling of any material is considered a variable
material load. Some materials, such as scaffold or forms, are
considered variable material loads when stockpiled but may
be considered fixed material loads when placed in their final
end use position. Engineering judgment must be used to
determine whether the stockpiled material should be
considered as a uniformly distributed or a concentrated load.
2.3.4.3—Personnel and Equipment Load
2.3.4.3.1—General
Personnel and equipment loads shall be considered in
the analysis or design of a partially completed or temporary
structure. The design or analysis of the structure shall be
governed by either a uniformly distributed and/or a
concentrated personnel and equipment load, whichever
creates the most severe strength and/or serviceability
condition.
The personnel and equipment loads used in the design
or analysis of a partially completed or temporary structure
shall be the maximum loads that are likely to be created
during the sequence of construction.
2.3.4.3.2—Individual Personnel Loads
Individual personnel loads consist of a concentrated
load of 300 lbs that includes the weight of one person plus
equipment carried by the person or equipment that can be
readily picked up by a single person without assistance.
C2.3.4.3.2
Individual Personnel Load is defined differently in
ANSI 10.8 as 250 lbs per person plus 50 lbs of equipment
per person; however, the load totals are the same.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
is aforviolation
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
SECTION 2: FALSEWORK
2-13
2.3.4.3.3—Uniformly Distributed Loads
C2.3.4.3.3
Uniform loads shall be selected to result in forces and
moments that envelope the forces and moments that would
result from the application of concentrated loads that could
occur and which are not separately considered.
Table 2.3.4.3.3-1—Classes of Working Surfaces for
Combined Uniformly Distributed Loads
Operational Class
Uniform Loada
(psf)
Very light duty: sparsely populated with
personnel; hand tools; very small amounts
of construction materials
20
Light duty: sparsely populated with
personnel; hand operated equipment;
staging of materials for lightweight
construction
25
Medium duty: concentrations of
personnel; staging of materials
50
Heavy duty: materials placement by
motorized buggies; staging of materials
for heavy construction
75
Construction loads, except for material loads, will
rarely be distributed uniformly. However, design for
equivalent uniformly distributed loads is a long standing
practice that has stood the test of time. The designer must
select a uniform load that will adequately capture the effects
of real anticipated construction loads. Table 2.3.4.3.3-1
presents a tabulation of traditional minimum uniformly
distributed loads that include personnel, equipment, and
material in transit or staging.
Note:
a. Loads do not include dead load, D, construction dead load, CD, or fixed materials
loads, CFML.
C2.3.4.3.4
The personnel and equipment concentrated loads shall
be the maximum loads expected in the construction process,
but shall be no less than given in Table 2.3.4.3.4-1. The
concentrated load shall be located to produce the maximum
strength and/or serviceability conditions in the structural
members. The designer shall consider each category of
minimum concentrated personnel and equipment load that is
likely to occur during the construction process.
Concentrated loads from equipment shall be determined
in accordance with Section 2.3.4.5.
Table 2.3.4.3.4-1—Minimum Concentrated Personnel &
Equipment Loads
Minimum
Loada
(lbs)
300
Area of Load
Application
(in.2)
12×12
Wheel of
manually
powered vehicle
500
Load divided by
tire pressurec
Wheel of
powered vehicle
2000
Load divided by
tire pressurec
Action
Each personb
Concentrated loads from equipment are a serious
concern. The type of equipment to be used for each
construction operation, its location (on or off the structure),
and its loading must be considered. Loads for different
types of construction equipment have been tabulated. See
also Section C2.3.4.5.1 for precautions in using tabulated
data.
Many specifications require temporary or permanent
structures to be designed for a uniform load and/or a
concentrated load. If the source of the concentrated load can
be clearly identified, such as wheel loads, axle loads, or
equipment reactions, that specific load should be distributed
as determined by its source.
Problems arise in determining the distribution areas of
unidentified, but specified, loads. To determine the
distribution area for an unidentified concentrated load,
assume that the load will be generated by the densest
material normally available on a construction site. That
material is arbitrarily chosen to be concrete at 150 pcf.
The specified concentrated load in Table 2.3.4.3.4-1 is
assumed to be the total load, including dynamic forces.
Notes:
a. Use actual loads where they are larger than tabulated here.
b. Need not be less than 18 in. ctr-to-ctr
c. For hard rubber tires, distribute load over an area 1 in. by the width
of the tire.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
2.3.4.3.4—Concentrated Loads
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
2.3.4.4—Horizontal Construction Load, Ch
One of the following horizontal load criteria, where
appropriate, shall be applied to temporary or partially
complete structures as a minimum horizontal loading,
whichever gives the greatest structural effects in the
direction under consideration:
•
For wheeled vehicles transporting materials,
20 percent for a single vehicle or 10 percent for two
or more vehicles of the fully loaded vehicle weight.
This force shall be applied in any direction of
possible travel, at the running surface.
•
For equipment reactions as described in
Section 2.3.4.5, the calculated or rated horizontal
loads, whichever are the greater.
•
50 lbs/per person, applied at the level of the platform in
any direction.
•
Two (2) percent of the total vertical load. This load shall
be applied in any direction and shall be spatially
distributed in proportion to the mass. This load need not
be applied concurrently with wind or seismic load.
This provision shall not be considered as a substitute for
the analysis of environmental loads.
2.3.4.5—Equipment Reactions, Cr
The equipment reactions shall include the full weight
of the equipment operating at its maximum rated load in
conjunction with any applicable environmental loads
unless the use is restricted and revised reactions are
developed.
2.3.4.5.1—Rated Equipment
The minimum equipment loads for design shall be
those provided by the equipment manufacturer or
supplier.
Unless equipment, such as front end loaders or fork
lifts, are intentionally restricted from tipping on one axle,
the loader self-weight plus tipping load shall be applied to
the front axle.
The designer shall verify the basis of the rating and
the rated reactions given by the equipment supplier. If the
basis of the rating is different than the conditions under
which the equipment will be used, then the more severe
reactions shall be used in design.
C2.3.4.4
The intent of this provision is to provide a minimum
lateral load resistance mechanism and a minimum lateral
stiffness in all temporary or partially complete structures.
Due to unavoidable eccentricities, vertical superimposed
loads may produce some horizontal loading. Also,
horizontal loads can be created from personnel and
equipment operations.
The designer should be aware that the actual
horizontal loads may exceed the minimum specified in
this section, particularly if more than one construction
activity is being conducted at the same time.
The 50 lbs/person load in Criterion 3 represents a
conservative estimate of the lateral force that could be
generated from the activities of personnel.
Criterion 4 is intended to provide a minimum lateral
load resistance and to assure lateral stability for the entire
structure during construction. Generally, it is not expected
that this criterion will result in forces during construction
that exceed the capacity of the permanent lateral load
resisting system of a structure below the level where the
permanent lateral load resisting system has been completed;
however, the permanent lateral load resisting system needs
to be checked for this criterion.
Wind and other phenomena that produce horizontal
loads must be considered separately from the requirements
of this section, as specifically provided in Criterion 4.
C2.3.4.5
Rated equipment is that for which reactions are
given by the equipment or supplier. For non-rated
equipment, the designer is to determine the reactions by
analysis. Crane and Derricks (Shapiro) provides
examples of calculations for reactions from lifting or
hoisting equipment that include assessments of
environmental loads.
C2.3.4.5.1
Care should be exercised when using the tabulated
values for equipment, such as loaders, from references or
from any manufacturer's data. Axle load distributions at
maximum load do assume that all of the axles are
touching the ground and with a certain load distribution.
Unless special precautions are taken, such as limiting
bucket size and floor or deck obstacles, it is a common
occurrence that the loaders, in attempting to pick
materials for transport, will either catch an element of the
deck or try to pick more than their rated load. In this
instance, the entire vehicle picks up and pivots about its
front axle. This load could create axle and wheel loads
more than 30 percent greater than the manufacturer's
rated wheel load.
2.3.4.5.2—Non-Rated Equipment
The equipment loads for non-rated equipment shall
be determined by analysis.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
2-14
SECTION 2: FALSEWORK
2-15
2.3.4.5.3—Impact
The reaction of equipment shall be increased by 30
percent to allow for impact, unless other values (either
larger or smaller) are recommended by the manufacturer,
are required by the authority having jurisdiction, or are
justified by analysis.
2.3.5—Environmental Loads
The basic reference for computation of environmental
loads is the 2010 edition of ASCE 7. The requirements of
ASCE 7 shall apply except as modified herein.
2.3.5.1—Risk Category
Unless otherwise required by the authority having
jurisdiction, the Risk Category, as defined in ASCE 7, shall
be taken as Risk Category II for all environmental loads
during construction, regardless of the Risk Category
assigned for the design of the completed structure.
2.3.5.2—Wind
C2.3.5.1
During construction, the primary occupancy of a
structure is by construction personnel. As such, the risk to
loss of human life is comparable to that for Risk Category
II buildings as defined in ASCE 7. Circumstances in which
the engineer may consider a higher Risk Category, or in
which some authorities have required such consideration,
include construction work immediately adjacent to essential
facilities in which a construction failure would imperil
operation of the essential facility.
C2.3.5.2
Except as modified herein, wind loads shall be
calculated in accordance with procedures in ASCE 7. Select
provisions from ASCE 7-10 have been reproduced in
Appendix C. Design wind pressures shall be based on design
wind speeds calculated in accordance with Section 2.3.5.2.1.
The basic wind pressure shall be increased by 5 psf for
falsework members over or adjacent to traffic openings.
If local conditions so dictate, and for certain hazardous
construction operations, it may be appropriate to apply a
minimum strength level wind pressure, such as 16 psf, to
design.
2.3.5.2.1—Design Wind Speed
The design wind speed shall be taken as the basic wind
speed in ASCE 7. Basic wind speed maps from ASCE 7-10
have been reproduced in Appendix C.
2.3.5.2.2—Frameworks without Cladding
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Structures shall resist the effect of wind acting upon
successive unenclosed components.
Treatment of staging, shoring, and falsework with
regular rectangular plan as trussed towers in accordance with
ASCE 7 shall be permissible. Unless detailed analyses are
performed to show that lower loads may be used, no
allowance shall be given for shielding of successive rows or
towers.
For unenclosed frames and structural elements, wind
loads shall be calculated for each element. Unless detailed
analyses are performed, load reductions due to shielding of
elements in such structures with repetitive patterns of
elements shall be as follows:
•
The loads on the first three rows of elements along the
direction parallel to the wind shall not be reduced for
shielding.
C2.3.5.2.2
Even though the design wind speed during
construction may be lower than that for the completed
structure, the total wind load may actually be higher due to
the cumulative effect of wind acting on many more surfaces
and often with higher drag coefficients than in the fully
enclosed structure. For common arrangements of elements
in typical open frames and temporary structures, shielding
effects are small. Considering the changing nature of the
bridge silhouette and the arrangement of construction
materials on the structure, it is prudent not to assume that
loads will be reduced due to shielding, except in certain
specific cases.
For open structures with regular patterns of elements,
the direction of maximum force on the structure usually is
not parallel to the principal axis of the structure. Shielding
effects are minimized, and therefore loads are at their
highest, when the direction of the wind is not parallel to the
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
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2-16
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
•
The loads on the fourth and subsequent rows shall be
permitted to be reduced by 15 percent.
•
Wind load allowances shall be calculated for all exposed
interior partitions, walls, temporary enclosures, signs,
construction materials, and equipment on or supported
by the structure. These loads shall be added to the loads
on structural elements.
column lines. For this reason, the most severe loads on an
open structure include components of load in both principal
directions of the structure.
For guidance on shielding effects and loads on open
structures, refer to Crane and Derricks (2000), Wind
Loading on Falsework, Part I (1975), Wind Loading on
Open Framed Structures (1981), and the Low Rise Building
Systems Manual (1996).
Calculations shall be performed for each primary axis of
the structure. For each calculation, 50 percent of the wind
load calculated for the perpendicular direction shall be
assumed to act simultaneously.
2.3.5.2.3—Accelerated Wind Region
Structures placed near building edges and corners shall
resist the higher pressures and suctions that will exist in such
regions. The design wind speed shall be factored upward
from the basic wind speed by the square root of the suction
coefficient for cladding as given in ASCE 7. The calculated
wind speed shall be used with appropriate drag factors to
calculate loads on structures. At building corners, the
resulting pressures shall be assumed to act on adjacent
staging structures in horizontal directions parallel to and
perpendicular to the enclosure surface. At top edges of
enclosures, pressures shall be assumed to act upward as well
as horizontally.
2.3.5.3—Snow
When snowfall is expected during the construction
period, snow loads shall be determined for surfaces on which
snow could accumulate in accordance with ASCE 7. If
construction will not occur during winter months when snow
is to be expected, snow loads need not be considered,
provided that the design is reviewed and modified, as
appropriate, to account for snow loads if the construction
period shifts to include winter months.
Design for snow loads that are lower than those
prescribed by this section shall be permissible, provided
adequate procedures and means are employed to remove
snow before it accumulates to levels that exceed the loads
used for design.
2.3.5.4—Earthquake
C2.3.5.4
If required by Section 2.3.5.4.1 and not exempted by
Section 2.3.5.4.3, earthquake loads shall be calculated in
accordance with procedures in ASCE 7 as modified by
Section 2.3.5.4.2. All structures shall be treated as Risk
Category II, per Table 1.5-1 of ASCE 7, regardless of the
group classification of the completed structure.
2.3.5.4.1—Applicability
Earthquake loads need not be considered unless
required by the authority having jurisdiction or the mapped
Risk-Targeted MCER, 5 percent damped, spectral response
acceleration parameter at a period of 1 second, S1, defined in
ASCE 7, Section 11.4.1 equals or exceeds 0.40. Maps
The earthquake provisions of ASCE 7 are modeled on
the 2009 NEHRP Recommended Provisions for Seismic
Regulations for New Buildings and Other Structures
prepared by the Building Seismic Safety Council.
C2.3.5.4.1
It is not reasonable to require seismic resistance for
temporary works where large earthquakes are infrequent or
not considered probable.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
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YANGand
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Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
SECTION 2: FALSEWORK
2-17
indicating the 5 percent damped, spectral response
acceleration parameter at a period of 1 second for the United
States, reproduced from ASCE 7-10, are shown in
Appendix D. Shading indicates those locations where S1
equals or exceeds 0.40.
This section applies to all constructions except those
specifically covered in Section 2.3.5.4.3.
2.3.5.4.2—Use of ASCE 7
C2.3.5.4.2
For use of the earthquake load provisions of ASCE 7,
the following modifications shall be made:
1.
The mapped values for SS and S1 may be multiplied by
a factor less than one to represent the reduced exposure
period, but the factor shall not be less than 0.20.
2.
The restrictions on types of structural systems in seismic
performance categories D and E do not apply, so long
as the temporary bracing system designed in accordance
with this section is limited in height to 60 ft or 5 stories,
whichever is less, above the completed bracing of the
permanent structure.
3.
The R factor used for temporary bracing systems shall
not exceed 2.5 unless the system is detailed in accordance with the provisions of ASCE 7. Where R = 2.5
is used, only the requirements dealing with the strength
of the seismic resisting structural system need be
satisfied.
2.3.5.4.3—Other Standards for Earthquake Resistant
Design
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Partially complete structures of a type that are excluded
by the earthquake load provisions of ASCE 7 and for which
specifically applicable standards for earthquake resistant
design exist shall be designed and evaluated according to the
specifically applicable standard. Earthquake loads for
temporary structures associated with such construction shall
be determined in accordance with Section 2.3.5.4.2 unless
the specifically applicable standard includes provisions for
temporary construction.
The ground motion response acceleration with a two
percent chance of exceedance in 1 yr (a mean recurrence
interval of about 50 yrs), SS*, ranges from approximately 5
to 20 percent of the value mapped as having a two percent
chance of being exceeded in a 50-yr period (a mean
recurrence interval of about 2475 yrs). The percentage is in
the upper portion of the range in the more seismically active
areas. A value of 20 percent is selected as representative of
this ratio. The intent of this section is for the soil
amplification factors, Fa and Fv, to be based on the full value
of SS and S1. With the introduction of ASCE 7, the basis of
the ground motions changed from a two percent chance of
being exceeded in a 50-yr period to a target risk of collapse
of one percent in 50 yrs. While the basis of the ground
motions used in ASCE 7 has changed, the ratio of these
values based on 1 yr and 50 yrs does not change.
The drift limitations and the non-structural provisions
are not required for temporary structures and for structures
during their construction phases.
C2.3.5.4.3
ASCE 7 excludes certain types of structures for various
reasons: unique characteristics of response to ground
shaking, exceptionally high risk associated with poor
performance, and the existence of other standards for
design. The provisions of Section 2.3.5.4.2 are intended to
make ASCE 7 usable for most temporary structures;
however, it is beyond the scope of this document to repeat
complete sets of seismic design provisions for structures
already covered by existing standards. California DOT
(Caltrans) has issued Caltrans Memo to Designers 20-2,
Caltrans Memo to Designers 20-12, and Caltrans Memo to
Designers 15-14 recommending acceleration levels to use
for temporary situations involving bridges carrying traffic
or positioned over traffic, that are higher than the values
specified in paragraph 1 of Section 2.3.5.4.2 for near fault
locations.
2.3.5.5—Stream Flow
When falsework supports are placed in flowing water,
water pressure on the supports shall be determined by the
following formula:
𝑃𝑃𝑤𝑤 = Kv²
(2.3.5.5-1)
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
2-18
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
where:
Pw
v
K
=
=
=
pressure (psf)
water velocity (ft/s)
1.375 for square faces
0.67 for circular piers
0.50 for angular faces
Where a significant amount of drift lodging against a
pier is anticipated, the effects of this drift build-up shall be
considered in the design. When it is anticipated that the flow
area will be significantly blocked by drift build-up, increases
in high water elevations, stream velocities, stream flow
pressures, and the potential increases in scour depths shall be
investigated.
2.3.5.6—Ice Loads
When falsework supports are expected to be exposed to
freshwater ice in rivers and lakes during the construction
period, ice loads shall be determined in accordance with
AASHTO LRFD Bridge Design Specifications. The ice loads
in seawater should be determined by suitable specialists
using site-specific information.
2.4.1—General
The falsework design analysis shall consider the
effect of foundation settlement, interaction between
elements of the falsework system and completed portions
of the permanent structure, and load redistribution due to
shrinkage and dead load deflection. The falsework design
shall accommodate these factors if necessary. For cast-inplace prestressed construction, the falsework shall be
designed to support any increased load resulting from load
redistribution caused by the prestressing forces.
The entire superstructure cross section, except
railing, shall be considered to be placed at one time except
as otherwise provided herein. Girder stems and connected
bottom slabs, if placed more than 5 days prior to the top
slab, may be considered to be self-supporting between
falsework posts at the time the top slab is placed, provided
that the distance between falsework posts does not exceed
four times the depth of the portion of the girder placed in
the first pour.
The support system for form panels supporting
concrete deck slabs and overhangs on girder bridges shall
be considered to be falsework and shall meet all falsework
design criteria and requirements. Additionally, such
falsework shall be designed so no differential settlement
will occur between the girders and the deck forms during
placement of the deck concrete.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
2.4—DESIGN
SECTION 2: FALSEWORK
2-19
2.4.2—Deflection
C2.4.2
The calculated vertical deflection for falsework
members shall not exceed 1 ∕240 of their span under the
dead load of the concrete only, regardless of the fact that
deflection may be compensated for by camber strips.
The theoretical deflection is the deflection that
would occur if all of the concrete in the bridge
superstructure were to be placed in a single pour.
Theoretical deflection is limited to 1 ∕240 of the span of the
falsework beam. This limiting value is included in the
specifications to ensure a certain degree of rigidity in the
falsework and thereby minimize distortion of the forms.
Theoretical deflection (deflection under the weight of the
entire superstructure) is usually greater than the actual
deflection for a given falsework member.
Actual deflection is the deflection that occurs as the
falsework beam is loaded. When calculating the actual
deflection, it is necessary to include the weight of forms
and falsework supported by the beam as well as the
weight of the concrete the beam actually supports. It is
also necessary to consider such factors as the sequence
of construction and the depth of the bridge.
Readily identifiable components of the deflection
arise from elastic shortening of support members and
foundation settlement, but additional and often more
significant deflections may occur due to take-up arising
from the straightening of bent sole plates, crushing of
timber packers, and other causes. The magnitude of
deflections arising from take-up is largely dependent on
the properties of packing materials and joint details. As
a general rule, however, the vertical take-up may be on
the order of 1/16 in. for every lumber surface in contact
with another wood member or steel component.
2.4.3—Slenderness
For compression members, the slenderness ratio Kl/r,
shall not exceed the following:

Main load-carrying members
i. Steel—180
ii. Aluminum—100

Bracing members
i. Steel—200
ii. Aluminum—150
The slenderness ratio of a tension member, other than
guy lines, cables, and rods, shall not exceed 240 for a main
member or 300 for a bracing member. These limits may
be waived if other means are provided to control
flexibility, sag, vibration, and slack in a manner
commensurate with the service conditions of the structure,
or if it can be shown that such factors are not detrimental
to the performance of the structure or of the assembly of
which the member is a part.
2.4.4—Overturning and Sliding
C2.4.4
The falsework system, including individual elements
and units of the system that are subject to overturning
forces, shall be analyzed for stability against overturning
and sliding with the falsework in the loaded and unloaded
For stability analysis, it is generally assumed that the
horizontal design load produces a moment that acts to
overturn the falsework system or element of the system
under consideration. When calculating overturning
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
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2-20
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
moments, the horizontal design load will be applied to
the falsework in accordance with the following:
2.4.5—Steel Beam Grillages
C2.4.5
Webs and flanges of steel beams under concentrated
loads shall satisfy the criteria specified in Chapter J, AISC
Steel Construction Manual, reproduced in Appendix B.
This Guide Design Specification separates flange
and web strength requirements into distinct categories
representing different limit states, namely, flange local
bending (AISC Section J10.1), web local yielding (AISC
Section J10.2), web crippling (AISC Section J10.3), web
sidesway buckling (AISC Section J10.4), web
compression buckling (AISC Section J10.5), and web
panel-zone shear (AISC Section J10.6).
These limit state provisions are applied to two
distinct types of concentrated forces normal to member
flanges:
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
condition; that is, with and without the dead load of the
concrete.
The ratio of the resisting moment to the overturning
and sliding moment shall be equal to or greater than 1.5
for all load combinations. Except as otherwise provided
in the following paragraph, if the ratio of the resisting to
the overturning moments is less than 1.5, external bracing
shall be provided to resist the full overturning moment.
Except for bracing required to prevent overturning or
collapse of the falsework system or any element of the
system, the ability of falsework members to resist
horizontal loads may include the contribution to stability
provided by the supported structure. Bracing required to
prevent overturning or collapse shall be designed to resist
the full horizontal design load with the falsework in the
unloaded (before the concrete is placed) condition, except
for cable bracing used to externally brace heavy duty
shoring systems. Such cables may be designed to resist
the difference between the overturning and resisting
moments.
The ratio of the total resisting force, caused by
friction and adhesion, to the base shear, caused by lateral
forces, shall be equal to or greater than 1.5 for all load
combinations. If the ratio of the resisting force to sliding
force is less than 1.5, external anchorage shall be provided
to resist the full sliding force.
•
Actual loads (such as those due to construction
equipment or to the concrete placing sequence) will
be considered as acting at the point of application to
the falsework.
•
Wind loads should be considered as acting at the
centroid of the wind impact area for each height
zone. When wind loads govern the design, however,
the horizontal design load (to be used in calculating
the overturning moment) is applied in a plane at the
top of the falsework post or shoring.
•
All other horizontal loads, including the minimum
load when the minimum load governs, would be
assumed as acting in a plane at the top of the
falsework posts or shoring.
The intent of Section 2.4.4 is to insure that for each
load combination identified in Section 2.4.2, the righting
moment shall be at least 1.5 times the overturning
moment and the resisting lateral force shall be at least 1.5
times the base shear.
•
•
Single concentrated forces may be tensile (such as
those delivered by tension hangers) or compressive
(such as those delivered by bearing plates at beam
interior positions, reactions at beam ends, and other
bearing connections). Flange local bending applies
only for tensile forces, web local yielding applies to
both tensile and compressive forces, and the
remainder of these limit states apply only to
compressive forces.
Double concentrated forces, one tensile and one
compressive, form a couple on the same side of the
loaded member, such as that delivered to column
flanges through welded and bolted moment
connections.
2.4.6—Proprietary Shoring Systems
C2.4.6 Proprietary Shoring Systems
Differential leg loading of vertical shoring systems
shall be minimized. In cases where differential leg loading
In the U.S., there are several manufacturers of
proprietary shoring systems. However, there are no
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
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SECTION 2: FALSEWORK
2-21
cannot be avoided, the manufacturer of the shoring system
shall furnish a letter of certification stating that the
proposed loading differential will not overstress any
tower component.
industry standards for the various components of these
systems, and as a general rule, towers or components
produced by different manufacturers should not be
intermixed. Some other limitations or general
characteristics of modular systems are as follows:
•
External bracing is recommended when the height
exceeds four times the least base dimension.
•
Allowable leg capacities are generally reduced
when the screw jacks, or extension legs, are fully
extended.
•
Multi-tiered towers stacked in excess of two frames
high have lower allowable leg capacities than
single- or double-tier towers.
•
The drift characteristics of proprietary systems can
vary considerably, depending upon their bracing
configurations. Ladder frames exhibit the least
lateral stiffness, and very little benefit is derived
from the horizontal braces.
Some manufacturers allow a 4 to 1 differential leg
loading between two legs of a frame, or two in a tower.
Examples of where this type of differential leg loading
could occur would be a skewed overpass where the
underlying right-of-way is maintained, or the exterior
shoring towers of a bridge deck supporting screed loads
and the overhang falsework. Significant differential
leg loads are generally discouraged, however, unless
substantiating data can be furnished by the manufacturer
that indicate that the differential loading will not
overstress the tower components.
2.4.7—Traffic Openings
C2.4.7
The vertical loads used for the design of falsework
columns and towers, but not footings, which support the
portion of the falsework over or immediately adjacent to
open public roads, shall be increased to not less than 150
percent of the design loads that would otherwise be
calculated in accordance with these provisions.
Each column or tower frame supporting falsework over
or immediately adjacent to an open public road shall be
mechanically connected to its supporting footing at its base,
or otherwise be laterally restrained, so as to withstand a force
of not less than 2,000 lb applied to the base in any direction.
Such columns or frames shall also be mechanically
connected to the falsework cap or stringer so as to be capable
of withstanding a horizontal force of not less than 1,000 lb in
any direction.
Temporary bracing shall be provided, as necessary, to
withstand all imposed loads during erection, construction,
and removal of any falsework whose height exceeds its clear
distance to either the edge of any sidewalk or shoulder of any
roadway that is open to the public or to a point 10 ft from the
centerline of any railroad track. The falsework drawings shall
show such temporary bracing or methods to be used to
conform to this requirement during each phase of erection
The modified design load requirement is adopted from
Caltrans, where experience has shown that the downward
force exerted by the bridge superstructure increases after the
deck concrete is placed. The increased force is the result of
deck shrinkage during the curing period; consequently, it
will be larger at falsework bents located near the center of
the bridge span that at bents near the abutments or columns.
The increased force is of greater concern in the case of castin-place prestressed structures (which have little loadcarrying capacity until tensioned) than in conventionally
reinforced concrete structures.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
2-22
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
and removal. Wind loads shall be included in the design of
such bracing or methods.
2.5—FOUNDATIONS
2.5.1—General
C2.5.1
The falsework shall be founded on pads, footings, or
piles that are capable of carrying the imposed loads without
aggravated distortion or settlement until the supported
structure becomes self-supporting.
Falsework foundations are generally set at shallow
depths because the loading is frequently temporary and may
only last for months as opposed to loadings from permanent
structures that will last for years. The foundations should be
designed with a minimum safety factor of 2.0 against failure
of the supporting ground and without detrimental
settlements. The ground support factors that need to be
considered include:
•
The properties of the various strata below foundation
level:
• Shear strength
• Compressibility
•
Site and construction considerations:
• Scour of the surface deposits
• Loss of shear strength due to construction
disturbance
• Settlement due to liquefaction from vibrations
• Reduced bearing capacity due to steep ground
slopes, shallow or no embedment, or cuts adjacent
to the loaded area
•
Potential problem soils:
• Collapsible soils
• Swelling and shrinking soils
• Frost-susceptible deposits
• Fill deposits
The purpose of this section is to provide guidelines for
evaluating the properties of the various strata below the
foundation level, including potential problem soils. These
evaluations must be done in order to properly design
foundation support for falsework systems. Detailed design
procedures for these factors are not represented since the
methodology for making these calculations is available in
textbooks or design manuals. The designer of the falsework
foundation should either be familiar with these procedures
or, where deemed necessary, consult with a geotechnical or
foundation engineer for recommendations. Foundation
Engineering (1974), Soil Mechanics (1986), and
Foundations and Earth Structures (1986) provide
simplified foundation design procedures. Additional
information pertaining to the investigation and design of
falsework foundations is provided in Appendix F.
2.5.2—Footings
C2.5.2
Footings shall be designed to distribute the applied load
over the supporting foundation material uniformly, without
exceeding the allowable soil-bearing value. The allowable
soil-bearing value shall be determined by the Contractor
through an examination of the site, a geotechnical foundation
The use of presumptive bearing values for design is
based on judgment and experience developed on a large
number of projects. For most situations, the presumptive
bearing pressures, as given in Table 2.5.2-1, are
conservative. However, the presumptive bearing values do
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
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SECTION 2: FALSEWORK
2-23
investigation, or through other appropriate means. In the
absence of other soils information, the presumptive bearing
values shown in Table 2.5.2-1 may be used as a guide, but
the Contractor is responsible for the actual value used in the
design.
The presumptive bearing values shown in Table 2.5.2-1
are for level and sloping ground where the slope is not greater
than 1 vertical to 6 horizontal.
If the data obtained during the site exploration is
minimal or if there is a significant amount of variation from
one sampling location to another, the presumptive bearing
pressure values given in Table 2.5.2-1 shall be multiplied by
a factor of 0.75 to take into account the non-uniformity and
uncertainty of the site conditions.
These values apply for the ground water level at a depth
below the foundation greater than the width of that
foundation. Continued flooding or wet weather will soften
clay soils. In granular soils, the buoyant unit weight of the
soil will reduce the bearing capacity. Where site flooding
and/or high ground water levels are likely to be experienced,
the presumed allowable bearing pressure in Table 2.5.2-1
shall be multiplied by the factor given in Table 2.5.2-2.
Pursuant to the provisions in Section 2.1, the allowable
soil-bearing value used in the foundation design shall be
shown on the falsework drawings.
Footings with eccentric loadings shall be designed so
that no portion of the footing has uplift pressures.
not consider important factors such as foundation size and
embedment, soil stress history, and stress distribution of
layered soils. Thus, the presumptive soil pressures should
be considered to be an upper bound value. The design
bearing pressures should be based upon site specific
information and a more thorough analysis. The designer
should also check the local building code, since
presumptive bearing values in these codes are based upon
local experience.
Soil descriptions used in Table 2.5.2-1 are in
accordance with the Unified Soil Classification System,
briefly described in Table F.4. These values are based upon
typical soil properties for various types of deposits. For the
pressures listed, settlements should be in an acceptable
range.
Both uniform and differential settlement can affect the
adequacy of the falsework foundations. For soil Groups 1
and 2 in Table 2.5.2-1, settlement should not be a major
factor. However, settlement may be significant for soil
Group 3 and a more detailed settlement analysis shall be
carried out. For soil Group 4, the use of shallow foundations
is generally not acceptable. Deep foundations are normally
used for support of the falsework in these deposits. The
amount of movement that can occur in soil Group 5 is a
function of local conditions, climatic effects, and other
geologic considerations. A local geotechnical engineer shall
be consulted regarding these matters.
Table 2.5.2-1—Presumptive Soil-Bearing Values
Group
1
Excellent
Foundation Support
2
Generally Adequate
Foundation Support
3
Poor Foundation
Support
4
Unacceptable
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
5
Potential Problem
Soils
Foundation Bearing Deposit
A. Hard shales and soft sandstones
B. Soft shales, soft claystones, and very soft sandstones
C. Weak and fractured limestone
D. Dense sands and gravels
E. Very stiff to hard clays
A. Medium dense sands and gravels
B. Medium dense uniform-size sand
C. Stiff clays
A. Loose sand or loose sand and gravel
B. Loose uniform-size sand
C. Soft to medium clays
D. Loose silts
A. Peat and organic silts
B. Very soft clays
A. Collapsible soils
B. Swelling soils
C. Frost-susceptible soils
D. Fill deposits
Presumptive Bearing Pressure
15 tsf
6 to 10 tsf
10 tsf
3 tsf
3 tsf
2 tsf
1.5 tsf
1 5 tsf
1 tsf
0.75 tsf
0.5 tsf
0.5 tsf
•
Requires deep foundations for
soils A and B
•
Requires special attention to
moisture control for soils A and B
•
Could require insulation.
•
Could be same as Groups 2 and 3
depending upon compaction.
Table 2.5.2-2—Groundwater-Level Modification Factors
Condition
Modification Factors for
Cohesive Soils
Noncohesive Soils
Rock
Groundwater level at B, or less, below level of foundation
(where B is width of foundation)
1.00
0.50
1.00
Site liable to flooding
0.67
0.50
1.00
Order Number: 02250056
© 2017 by the American Association of State
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2-24
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
2.5.3—Pile Foundations
C2.5.3
When timber piles are used, the load applied to any
pile in the foundation under any loading condition shall
not exceed 40 tons.
When steel piles are used, the load applied to any pile
in the foundation under any loading condition shall not
exceed the capacity of the pile when analyzed as a short
column. These values presume that piles have been driven
to these capacities with a minimum safety factor of 1.5.
for working stress design.
When piles extend above the ground line, the loadcarrying capacity of both individual piles and piles within
a framed bent shall be evaluated under the combined
action of the vertical and horizontal design loads with a
maximum settlement not to exceed 1 in.
If the surface deposits provide insufficient bearing
capacity, or the shallow foundations are predicted to
deform more than allowed, it will be necessary to extend
the foundations through the surface deposits to a more
competent bearing stratum. If piles are to be used, the
driving criteria should be selected on the basis of a wave
equation analysis or an accepted driving formula. The
penetration data of the last 5 ft of driving should be
recorded and submitted to the designer of the falsework
foundations. Guidelines for the design of the pile
foundations are presented in Chapter 10 of AASHTO
LRFD Bridge Design Specifications.
2.5.4—Foundations for Heavy-Duty Shoring Systems
C2.5.4
Foundations for individual steel towers where the
maximum leg load exceeds 30 kips shall be designed and
constructed to provide uniform settlement under all legs
of each tower under all loading conditions.
In any case where the maximum leg load within a
given tower exceeds 30 kips, the tower foundation
should be designed and constructed to provide uniform
settlement under all legs of the tower under all
loading conditions. This requirement is included in
the specifications to prevent distortion of the tower
components as a consequence of unequal leg settlement.
The effect of unequal leg settlement becomes more
severe as leg loads increase; consequently, the tower
foundation design, including the method employed to
ensure uniform settlement, is relatively more important
when leg loads are high.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
is aforviolation
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
Section 3
FORMWORK
3.1—MATERIALS AND FORM ACCESSORIES
3.1.1—General
C3.1.1
Concrete forms shall be mortartight; true to the
dimensions, lines, and grades of the structure; and of sufficient
strength to prevent appreciable deflection during the placing
of the concrete.
Prior to the use of each forming system to be used for
exposed surfaces and when requested by the Engineer, the
Contractor shall furnish form design and materials data to the
Engineer for approval.
Formwork for Concrete describes the formwork
materials commonly used in the United States and provides
extensive related data for form design. Information is also
available from manufacturers and suppliers of materials.
Table C3.1.2-1 indicates other specific sources of design
and specification data for formwork materials. This
tabulated information should not be interpreted to exclude
the use of any other materials that can meet quality and
safety requirements established for the completed work.
Bridge formwork can be divided into two categories:
vertical and horizontal formwork. Vertical formwork can be
generally constructed using job-built systems or
prefabricated systems. Horizontal formwork can be
constructed utilizing job-built, prefabricated, or permanent
stay-in-place systems. These systems are defined as:
•
Job-Built Formwork—A formwork system designed
and built for a specific application, most commonly
using plywood and lumber.
•
Prefabricated Formwork—Most commonly a
modular system that has the durability for multiple
reuses and normally is built with plywood with a metal
framing. Prefabricated formwork can be built for
custom uses on special projects.
•
Stay-in-Place Formwork—A formwork system
designed such that the formwork is not removed after
construction. This system most commonly consists of
stay-in-place metal decks or precast concrete planks.
3.1.2—Sheathing
C3.1.2
Form panels for exposed surfaces shall be plywood,
conforming to or exceeding the requirements of U.S.
Product Standard PS 1-09 for Exterior B-B (concrete form)
Plyform Class I, Structural Class I, or other equivalent
grades of plywood, used with the face grain perpendicular
to the joists. Overlaid, laminated, or other types of form
panels may be utilized at the Contractor’s discretion,
provided that the physical properties conform to
requirements of the formwork design. They shall be free of
knotholes, warps, or other defects.
Sheathing is defined as the supporting layer of
formwork closest to the concrete. It may be in direct
contact with the concrete or separated from it by a form
liner. Sheathing materials consist of wood, plywood,
metal, or other products capable of transferring the load
of the concrete to supporting members such as joists or
studs. In selecting and using sheathing materials,
important considerations are: (1) strength; (2) stiffness;
(3) ease of release; (4) reuse and cost per use; (5) surface
characteristics imparted to the concrete such as wood
grain transfer, gloss, and paintability; (6) resistance to
mechanical damage, such as from vibrators and abrasion
from slip forming; (7) workability for cutting, drilling,
and attaching fasteners; (8) adaptability to weather and
extreme field conditions, temperature, and moisture; and
(9) weight and ease of handling.
3-1
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
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All rights reserved. Duplication Not
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--`,,,`,,`,`,`,`
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
3-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Table C3.1.2-1—Form Materials with Data Sources for Design and Specification (reproduced from ACI 347)
Item
Principal Uses
Sawn lumber
Form framing, sheathing, and
shoring
Engineered woodb
Form framing and shoring
Plywood
Form sheathing and panels
Panel framing and bracing
Heavy forms and falsework
Column and joist forms
Steel
Stay-in-place deck forms
Shoring
Steel joists used as horizontal
shoring
Expanded metal bulkheads, singlesided forms
Data Sourcesa
“American Softwood Lumber Standard,” PS 20-94
Wood Handbook, Reference 7b
Manual for Wood Frame Construction, Reference 7c
National Design Specification for Wood Construction, ANSI/AF&PA NDS1997, Reference 9
Timber Construction Manual, Reference 7d
Structural Design in Wood, Reference 7e
Engineered Wood Products, Reference 7f
“Code for Engineering Design in Wood,” (Canada) CAN3-086
“Engineering Design in Wood (Limit States Design),” CAN/CSA-096.1-94
“Construction and Industrial Plywood,” PSI-95
APA Plywood Design Specification, Reference 7h
APA Concrete Forming, Reference 7i
Specification for Structural Steel Buildings–Allowable Stress Design and
Plastic Design, Reference 7j
Specification for the Design of Cold-Formed Steel Structural Members,
Reference 7k
Forms for One-Way Joist Construction, ANSI A48.1
Forms for Two-Way Concrete Joist Construction, ANSI A48.2
Recommended Industry Practice for Concrete Joist Construction, part of
Reference 7a
ASTM A446 (galvanized steel)
Recommended Safety Requirements for Shoring Concrete Formwork,
Reference 7o
Recommended Horizontal Shoring Beam Erection Procedure,
Reference 7p
Standard Specifications and Load Tables for Open Web Steel Joists, K-series,
Reference 7q
Expand Your Forming Options, Reference 7r
Aluminumc
Form panels and form framing
members
Horizontal and vertical shoring and
bracing
Reconstituted wood
panel productsd
Form liners sheathing
Mat Formed Wood Particle Board, ANSI A208.1
Hardboard Concrete Form Liners, LLB-810a
Performance Standard for Wood-Based Structural Use Panels, PS2-92
Stay-in-place form liners or
sheathing
Cold-weather protection for fresh
concrete
ASTM C532 (insulating form board)
Insulation materials
Wood fiber or glass
fiber
Other commercial
products
Fiber or laminated
paper pressed tubes
or forms
Corrugated
cardboard
Column and beam forms
Void forms for slabs, beams,
girders, and precast piles
Internal and under-slab void forms
Void forms in beams and girders
(normally used with internal “eggcrate” stiffeners)
Aluminum Construction Manual, Reference 1
A Study of Cardboard Voids for Prestressed Concrete Box Slabs,
Reference 7w
Notes:
a.
Manufacturer’s recommendations, when supported by test data and field experience, are a primary source for many form materials. In addition,
the handbooks, standards specifications, and other data sources cited herein are listed in more detail in Formwork for Concrete and in the
reference section of this document. Be sure to check cautionary footnotes for engineered wood, aluminum, and panel products made of
reconstituted wood.
b. Structural composite lumber products are proprietary and unique to a particular manufacturer. They cannot be interchanged because industrywide common grades have not be established to serve as a basis for equivalence.
c.
Should be readily weldable and protected against galvanic action at the point of contact with steel. If used as a facing material in contact with
fresh concrete, should be nonreactive to concrete or concrete containing calcium chloride.
d. Check surface reaction with wet concrete.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
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Provided by IHS Markit under license with AASHTO
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SECTION 3: FORMWORK
3-3
3.1.3—Structural Supports
Materials used for structural supports shall conform to
the applicable provisions of Section 2.
Vertical side forms, wall forms, and column forms and
their related studs, wales, etc. are all defined as formwork.
Structural supports on bridge deck soffits and slab
overhangs are falsework by definition and shall be
designed accordingly.
3.1.4—Prefabricated Formwork
The Contractor shall furnish shop drawings and
technical data substantiating load-carrying capacity and
detailing application instructions and limitation of use. The
Contractor shall utilize prefabricated product in accordance
with manufacturer’s recommendations.
3.1.5—Stay-in-Place Formwork
C3.1.5
Stay-in-place soffit forms, such as corrugated metal or
precast concrete panels, may be used if approved by the
Engineer. If the use of such forms is proposed by the
Contractor, complete details for their use shall be provided
to the Engineer for review and approval prior to use. The
detailed plans for structures unless otherwise noted, are
dimensioned for the use of removable forms. Any changes
necessary to accommodate stay-in-place forms, if
approved, shall be at the expense of the Contractor.
Stay-in-place steel bridge deck forms and supports
shall be fabricated from steel conforming to ASTM
A653/A653M Grade A-3, coating class G165.
Stay-in-place precast bridge deck forms shall be
manufactured in accordance with Recommended Practice
for Precast Prestressed Concrete Composite Bridge Deck
Panels (1988).
In areas where form removal is expensive or
hazardous, the use of stay-in-place (S.I.P.) forms may be
desirable. The additional dead weight of the deck slab,
appearance, and corrosiveness of the environment are
some of the factors that should be considered when
deciding if metal or concrete S.I.P forms should be used.
Some states have developed criteria for allowing the use
of corrugated steel S.I.P forms. These criteria are
generally based on FHWA Instructional Memorandum
40-3-72 (no longer an active FHWA policy), except that
deflections are limited to 1∕240 or 0.75 in. (20 mm),
whichever is less.
3.1.6—Form Accessories
C3.1.6
When form ties, form hangers, anchor ties, column
clamps, inserts, and other similar devices are used to
support formwork, the allowable working load shall be
based on the in situ load conditions. When requested by the
Engineer, the Contractor shall provide shop drawings and
technical data substantiating the load-carrying capacity and
detailing application instructions and limitations of use. In
all cases, the Contractor is required to follow the
manufacturer’s recommended instructions.
Since a large proportion of formwork accessories
consists of proprietary equipment, the designer shall,
prior to use in designs, ensure that the engineering data
provided by equipment suppliers include the following:
•
The basis on which the safe working loads were
determined, and whether the factor of safety is based
on yield load or ultimate load.
•
A statement as to whether the supplier’s data are
based on calculations or test results.
•
Instructions for both use and maintenance, including
points that may require special attention during
formwork erection or dismantling.
•
Detailed information on mass, dimensions, load
capacities, deflections, shear, bending moment, and
torsional strength if applicable.
•
Number of reuses before refurbishment is required.
•
When threaded parts are utilized in the formwork
design, the designer must call out thread type and
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
3-4
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
dimensions to ensure that the component parts have
compatible threads. Caution is warranted when
interchanging component formwork accessories
from different manufacturers because most
formwork accessories are designed and tested as a
system. Interchanging component parts may affect
load-carrying capacity or formwork connections,
leading to premature failures. Manufacturer’s
recommended procedures and instructions must be
followed in formwork design and construction.
3.2—LOADS
3.2.1—Vertical Load
The total dead load shall equal the weight of the
formwork plus the weight of the freshly placed concrete.
The minimum live load shall be 50 psf for the vertical
load of construction traffic. This requirement is for
formwork only and does not apply to the underlying
falsework. When large equipment is to be utilized during
the construction process, including motorized carts, the
minimum live load shall be 75 psf.
The minimum design load for combined dead and live
loads shall not be less than 100 psf, or 125 psf if motorized
carts are used.
3.2.2—Lateral Pressure of Fluid Concrete
3.2.2.1—Form Pressure
C3.2.2.1
CC = wh
(3.2.2.1-1)
where:
CC
w
h
=
=
=
lateral pressure (psf)
unit weight of fresh concrete (pcf)
depth of fluid or plastic concrete from top of
placement to point of consideration in form
(ft)
The lateral pressure formulas are adopted from ACI
347-04. Equation 3.2.2.1-1 assumes a fully liquid head
and normally can be applied without restriction.
However, there are exceptions. Caution must be taken
when using external vibration or concrete made with
shrinkage compensating cement. In these situations,
pressures in excess of equivalent hydrostatic pressures
may occur.
The designer must consider the uplift caused by the
vertical component of the normal pressure of freshly
placed concrete on inward sloping forms.
The set characteristics of a mixture should be
understood, and using the rate of placement, the level of
fluid concrete can be determined. For columns or other
forms that may be filled rapidly before any stiffening of the
concrete takes place, h shall be taken as the full height of
the form or the distance between horizontal construction
joints when more than one placement of concrete is to be
made. When working with mixtures using newly
introduced admixtures that increase set time or increase
slump characteristics, such as self-consolidating concrete,
Eq. 3.2.2.1-1 shall be used until the effect on formwork
pressure is understood by measurement.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
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YANGand
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Unless the conditions of Section 3.2.2.2 are met,
formwork shall be designed for the lateral pressure of the
newly placed concrete given by Equation 3.2.2.1-1.
Maximum and minimum values given for other pressure
formulas do not apply to Equation 3.2.2.1-1.
SECTION 3: FORMWORK
3-5
3.2.2.2—Form Pressure—Reduced Hydrostatic
Head
For concrete having a slump of 7 in. or less and placed
with normal internal vibration to a depth of 4 ft. or less,
formwork can be designed for a lateral pressure as follows:
For columns:
CC = FcFw [150 + 9000 R/T] (psf)
(3.2.2.2-1)
with a minimum of 600Fw (psf), but in no case greater than
wh.
C3.2.2.2
Under the limitations listed, the formwork may be
designed for a maximum lateral pressure, as provided in
Eqs. 3.2.2.2-1, 3.2.2.2-2, and 3.2.2.2-3 that is less than
the full hydrostatic head.
Where any of the limitations are not met, the
lateral pressure must be taken as provided in
Equation 3.2.2.1-1. Eqs. 3.2.2.2-1, 3.2.2.2-2, and
3.2.2.2-3 are applicable for concrete with unit weights up
to 150 pcf.
For walls with placement rate less than 7 ft/h and a
placement height not exceeding 14 ft.:
CC = FcFw [150 + 9000 R/T] (psf)
(3.2.2.2-2)
with a minimum of 600Fw psf, but in no case greater than
wh.
For walls with placement rate of less than 7 ft/h where
placement height exceeds 14 ft. and for all walls with a
placement rate of 7 to 15 ft/h:
CC = FcFw [150 + 43,400/T + 2800 R/T] (psf) (3.2.2.2-3)
with a minimum of 600Fw (psf), but in no case greater
than wh.
where:
=
=
=
=
chemistry factor per Table 3.2.2.2-1
unit weight factored per Table 3.2.2.2-2
rate of placement, ft/hr
temperature of concrete in the form (°F)
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Fc
Fw
R
T
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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- CPCP-WEST@CFBPC.COM,
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3-6
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Table 3.2.2.2-1—Chemistry Factor, Fc
Cement Type
Fc
Types I, II, and III without retardersa
1.0
Types I, II, and III with a retardera
1.2
Other types or blends containing less than
70% slag or 40% fly ash without retardersa
1.2
Other types or blends containing less than
70% slag or 40% fly ash with a retardera
1.4
Blends containing more than 70% slag or
40% fly ash
1.4
Note:
a.
Retarders include any admixture, such as a retarder,
retarding water reducer, retarding midrange waterreducing admixture, or high-range water-reducing
admixture (superplasticizer), that delays setting of
concrete.
Table 3.2.2.2-2—Unit Weight Factor, Fw
U.S. Customary
Unit Weight of Concrete
Fw
Less than 140 lb/ft3
0.5[1+w/145 lb/ft3]
But not less than 0.80
140 to 150 lb/ft3
1.0
More than 150 lb/ft3
w/145 lb/ft3
3.2.3—Horizontal Loads
Vertical wall or side form bracing shall be designed to
meet the minimum wind load requirements of Section 2.3.5.2
or the local building code, whichever is more conservative.
For wall forms exposed to the elements, the minimum wind
design load shall not be less than 15 psf. Bracing for wall
forms shall be designed for a minimum horizontal load of 100
plf of wall applied at the top.
3.3—DESIGN
The design of formwork shall be the responsibility of the
Contractor. When required by the Contract Documents or
pursuant to Section 3.1.1, shop drawings shall be submitted
for review by the Engineer. Such review does not relieve the
Contractor of the responsibility of constructing the structure in
accordance with the Contract Documents.
In selecting the hydrostatic pressure to be used in the
design of forms, consideration shall be given to the maximum
rate of concrete placement to be used, the effects of vibration,
the temperature of the concrete, and any expected use of setretarding admixtures or pozzolanic materials in the concrete
mix.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
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Provided by IHS Markit under license with AASHTO
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--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
3.3.1—General
SECTION 3: FORMWORK
3-7
3.3.2—Allowable Stresses
C3.3.2
Unit stresses for use in the design of formwork,
exclusive of accessories, shall conform with applicable
codes or standards. When fabricated formwork, shoring, or
scaffolding
units
are
used,
manufacturer’s
recommendations for allowable loads may be followed if
supported by the test reports of a qualified and recognized
testing agency. For formwork materials that will
experience substantial reuse, reduced values should be
used.
For formwork materials with limited reuse, allowable
stresses specified in the appropriate design codes or for
temporary loads on permanent structures may be used.
Where there will be a considerable number of formwork
reuses or where formwork is fabricated from materials
such as steel, aluminum, or magnesium, it is
recommended that the formwork be designed as a
permanent structure carrying permanent loads.
3.3.3—Deflection
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Forms for exposed concrete surfaces shall be designed
and constructed so that the formed surface of the concrete
does not undulate excessively in any direction between
studs, joists, form stiffeners, form fasteners, or
wales. Undulations exceeding either ⅛ in. or 1/240 of the
center-to-center distance between studs, joists, form
stiffeners, form fasteners, or wales will be considered
excessive.
Should any form or forming system, even though
previously approved for use, produce a concrete surface
with excessive undulations, its use shall be discontinued
until modifications satisfactory to the Engineer have been
made. Portions of concrete structures with surface
undulations in excess of the limits herein may be rejected
by the Engineer.
3.3.4—Safety Factors for Form Accessories
Minimum factors of safety for formwork accessories such
as form ties, form anchors, and form hangers shall conform
with the safety factors presented in Table 3.3.4-1 In
selecting these accessories, the formwork designer shall
make certain that materials furnished for the job meet these
minimum strength safety requirements.
Table 3.3.4-1—Minimum Safety Factors of Formwork Accessoriesa
Accessory
Safety Factor
Type of Construction
Form tie
2.0
All applications
2.0
Formwork supporting weight and concrete pressures only
3.0
Formwork supporting weight of forms, concrete, construction live loads and impact
Form hangers
2.0
All applications
Anchoring inserts
used as form ties
2.0
Precast concrete panels when used as formwork
Form anchor
Note:
a. Safety factors are based on ultimate strength of accessory.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
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Section 4
TEMPORARY RETAINING STRUCURES
4.1—GENERAL
C4.1
All excavations shall meet Federal OSHA Standards
as outlined in 29CFR Part 1926, Subpart P. Sloped
excavations shall have side slopes no steeper than those
specified in Subpart P of OSHA 29CFR Part 1926 for the
type of soil, as identified by a licensed geotechnical
engineer.
Vertical-sided excavations shall be sheeted and braced
as necessary to retain the earth and water pressures as
specified in Section 4.3. The effects of any live load and
dead load surcharges acting on the surrounding area shall
also be considered in the design of the temporary retaining
structure. Formulas given are for vertical walls with
horizontal ground surface structure. For other cases, refer
to standard textbooks in soil mechanics or
NAVFAC DM-7.
Excavations required for construction of
foundations and any other below-grade components of
structures are made with sloping sides or with vertical or
near vertical sides, depending on several factors such as
available space, type of soil, water table, depth of cut,
duration of the work, etc. In all cases, the conditions
must provide for stability and protection of workmen as
well as the newly constructed and adjacent existing
structures. OSHA has specified certain minimum slopes
for the various types of soils and shoring requirements
for vertical-sided trenches. However, actual on-site soils
and neighboring conditions may require supplementary
measures such as flattening of slopes, dewatering, and
additional bracing.
The influence zone of surcharge pressures will
depend on the type of soil. In weak soils, the zone of
influence may be flatter than 45° from the base of
excavation.
The formulae for lateral pressures given in
Section 4.3 are for the simple case of a vertical cut in
homogenous ground with a level surface. For
complicated geometry, either a simplified model can be
made, or an analysis can be done using the actual specific
geometry and formulae given in standard textbooks.
4.2—TYPES OF RETAINING STRUCTURES
C4.2
Selection of the type of retaining structure shall be
based on an assessment of the type of soil, depth of cut,
position of the water table, environmental conditions such
as location of nearby foundations, physical constraints,
sensitivity of adjacent structures to movements, and ease
of construction.
For excavations in stiff cohesive soils, common types of
temporary retaining structures are wood sheeting, steel
soldier piles and wood lagging, and steel sheet piles. In soft
cohesive soils and wet granular soils, steel sheet piles are
most commonly used. Soil washout shall be prevented by
use of admixtures attached to the sheeting joints, hay,
geotextiles, excelsior, or similar materials. Where ground
movement is to be minimized, all voids outside the lagging
or sheeting shall be packed with soil, sand, gravel, or grout,
as necessary.
The type of retaining structure is usually selected by the
Contractor. The selected scheme must satisfy the
protection requirements of the constructed and existing
facilities and, of course, the workmen. Ground water
control is an essential element for maintaining the
stability and support capacity of the soils. Soil retaining
schemes may include soil stabilization by grouting,
freezing, soil nailing, etc. Trench boxes installed in
overexcavated trenches do not prevent ground
movements. Their primary objective is protection of
workmen and the installations within the trench box.
4.3 —LATERAL EARTH PRESSURES
C4.3
Charts and graphs are available in many textbooks
for active and passive earth pressure coefficients related
to the soil angle of internal friction, angle of friction
between the wall element (for example, sheetpiles) and
the soil, inclination of the surcharge or backfill, and the
inclination of the wall. Various design simplifications
4-1
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
4-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
are often made in the surcharge geometry to utilize the
available earth pressure coefficient charts.
4.3.1—Cantilever Walls
For a cantilever retaining wall system or walls with a
single level of bracing, lateral pressures shall be computed
by the Rankine or Coulomb method. For active pressure
calculation, friction between the soil and the wall element
shall be neglected.
4.3.1.1—Wall Movement Necessary for Active
Pressures
In order for the calculated pressures to be attained, the
soil must undergo some strain, dependent upon the elastic
modulus of the soil and the structural member in contact.
Restraining effects of anchors and tie backs may create
higher pressures than the basic active pressures from the
Rankine or Coulomb formulas. Pressures in restrained
cases may approach those from the passive pressure or atrest pressure formulas.
For passive pressure calculations by the Coulomb
method, the angle of wall friction shall be less than onethird the effective angle of internal friction for the soil.
Wall movements considered necessary to mobilize
active pressure are tabulated below.
Soil Type
Wall Movement
Cohesionless—dense
0.001H
Cohesionless—medium to
loose
0.002H to 0.004H
Cohesive—hard to stiff
0.01H to 0.02H
Cohesive—medium to soft
0.02H to 0.04H
C4.3.1.1
For very rigid retaining structures, ground
movements may not be sufficient to mobilize active
pressures. In such cases, the design should consider the
higher at-rest pressures. If the retaining wall is restrained
by prestressed anchors, high pressures are usually
induced at the anchor location. Earth pressure
distribution would be irregular and different from the
usual triangular pattern of active or at-rest state. Such
cases should be designed by an experienced geotechnical
engineer.
The wall movements given in the specifications are
for rotation about the bottom of the excavation. If the top
of the retaining structure is restrained and it acts as the
fulcrum for rotation, then the earth pressure distribution
is no longer triangular and a higher pressure occurs at the
location of the support.
where:
H = height of wall
4.3.1.2—Active Pressures
C4.3.1.2
Active Earth Pressure for Cohesionless Soils:
pₐ = kₐγ𝑠𝑠 H (psf)
(4.3.1.2-1)
where:
γ𝑠𝑠
=
unit weight of soil (pcf); for most soils, moist
unit weight ranges from 100 to 130 pcf. Use
total moist weight above the water table and
buoyant unit weight below the water table.
Cohesionless Soils—The angle of internal friction for a
cohesionless soil may be estimated from standard
penetration tests and charts given in many soil mechanics
textbooks and also in NAVFAC DM-7. Careful
evaluation of loose layers or zones is recommended
because they may act as the weak zone of a potential
slide.
--`,,,`,,`,`,`,`,`,,`,,,-`-
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
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SECTION 4: TEMPORARY RETAINING STRUCTURES
H
=
depth below ground level (ft)
ka
=
active earth pressure coefficient
=
tan2 (45° - ϕ𝑓𝑓 /2)
=
ϕ𝑓𝑓
angle of internal friction which usually ranges
from 26° to 30° for medium to dense soils
Active Earth Pressure for Cohesive Soils:
pₐ = γs H – 2c (psf)
(4.3.1.2-2)
where:
=
total unit weight of soil (pcf)
H
=
depth below ground level (ft)
c
=
cohesion = Qᵤ/2
Qᵤ
=
undrained unconfined compressive strength
in (psf)
γ𝑠𝑠
4-3
Cohesive Soils—Tension cracks and fissures, etc. in
cohesive soils can destroy the cohesion. Cohesion is also
lost from exposure to weather, pore pressure dissipation,
erosion, remolding, and other construction activities.
Hence, a minimum active pressure coefficient of 0.25
has been specified.
In the absence of test data, cohesion, c, may be estimated
to range between 20 to 25 percent of the effective overburden
pressure.
Pressures given by this formula may be negative in the
upper portion of the wall, depending on the value of cohesion.
In such cases, minimum active pressure shall not be less than
those for a cohesionless soil with an active earth pressure
coefficient, kₐ, of 0.25.
Active Earth Pressure for Mixed Soils:
pₐ = kₐγ𝑠𝑠 H – 2c�𝑘𝑘ₐ (psf)
(4.3.1.2-3)
where the symbols have the same meaning as described
above.
Minimum pressures shall not be less than those
corresponding to an active earth pressure coefficient of 0.25.
4.3.1.3—At-Rest Pressures
C4.3.1.3
Where ground movement is prevented, lateral
pressures shall correspond to the at-rest values given by:
pₒ = kₒγs H (psf)
(4.3.1.3-1)
where:
=
unit weight of soil (psf)
H
=
depth below ground level (ft)
kₒ
=
at-rest earth pressure coefficient, given
empirically as follows:
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
γ𝑠𝑠
Many published empirical formulas are available for
at-rest earth pressure coefficients. The selected value
should be consistent with local practice. Soil type and
stress history have a significant effect on these
coefficients. Hydrostatic pressures should be added
below the water table.
Cohesionless soils: ko = 1 – sin ϕ𝑓𝑓
Cohesive soils: ko = 0.95 – sin ϕ𝑓𝑓
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
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4-4
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
ϕ𝑓𝑓
=
effective angle of internal friction
Where free ground water can exist, earth pressures should
be determined for the buoyant unit weight of the soil below
the water table and separate hydrostatic pressures added to the
submerged soil pressures to determine the total earth pressure.
Mixed Soils—The above commentary for cohesive soils is
also applicable to the case of mixed soils.
For most normally consolidated clays, ϕ ranges between
20° and 28°. In overconsolidated and compacted clays, kₒ
values can be higher and design values shall be based on
appropriate values from standard textbooks.
4.3.1.4—Passive Pressures
C4.3.1.4
Passive Pressure—Cohesionless Soils:
pp = 𝑘𝑘𝑝𝑝 γs 𝐻𝐻 (psf)
(4.3.1.4-1)
where:
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
γs
=
unit weight of soil (psf)
H
=
depth below ground level (ft)
kp
=
passive earth pressure coefficient
=
(1 + sinϕ𝑓𝑓 )/(1 - sinϕ𝑓𝑓 ) for zero angle of wall
friction. For values of kp including the effect of
wall friction, refer to charts in standard
textbooks or NAVFAC DM-7.
Passive Pressure—Cohesive Soils:
pp = γs H + 2c (psf)
(4.3.1.4-2)
where:
=
unit weight of soil (psf)
H
=
depth below ground level (ft)
c
=
Qu/2 (psf)
Qᵤ
=
undrained unconfined compressive strength in
(psf)
γ𝑠𝑠
Passive Pressure—Mixed Soils:
pp = kpγ𝑠𝑠 H + 2c�𝑘𝑘𝑝𝑝 (psf)
(4.3.1.2-3)
where:
=
unit weight of soil (psf)
H
=
depth below ground level (ft)
c
=
Qu/2 (psf)
kp
=
passive earth pressure coefficient
=
(1 + sinϕ𝑓𝑓 )/(1 - sinϕ𝑓𝑓 ) for zero angle of wall
friction. For values of 𝑘𝑘𝑝𝑝 including the effect
γs
Cohesionless Soils—Passive pressure coefficients for
various geometries and angles of internal friction and wall
friction can be obtained from charts given in many soil
mechanics textbooks and handbooks. In computing the
passive pressures below the water table, use buoyant unit
weight of the soil and add hydrostatic pressure. The angle
of internal friction for the soil should be estimated
conservatively. Charts are available in textbooks that relate
the angle of internal friction to the relative density or
standard penetration test values. Seepage gradients will
reduce the passive pressure.
Cohesive Soils—The formula given for the passive pressure
is for undrained conditions. Pore pressure dissipation can
reduce the passive resistance significantly. For long
duration exposure, passive pressures should also be
evaluated for the drained effective friction angles using the
formulas for cohesionless soils and the design based on the
lower pressures. Ground water table conditions must also
be considered in the analysis of earth pressures.
Mixed Soils—The above commentary for cohesionless and
cohesive soils is also applicable to the mixed soils.
Hydrostatic pressures in cohesionless layers interbedded in
cohesive layers can cause uplift and heaving and reduce
passive pressures significantly. The design should consider
relief of uplift pressures, as appropriate.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
SECTION 4: TEMPORARY RETAINING STRUCTURES
4-5
of wall friction, refer to charts in standard
textbooks or NAVFAC DM-7.
Qᵤ
=
undrained unconfined compressive strength in
(psf)
Passive resistance in top 1 ft should be neglected. Design
values of cohesion shall be selected conservatively with a
minimum factor of safety of 1.5. Effect of soil disturbance at
the excavated subgrade shall also be considered. If duration of
exposure is sufficient for pore pressure dissipation, design
values in cohesive and mixed soils shall be based on effective
strength parameters, neglecting the undrained cohesion.
Full passive pressures will be mobilized where ground
movements will cause strains of 0.02H to 0.04H for medium
to dense cohesionless soils, and 0.02H to 0.04H or more for
hard to soft cohesive soils. Where smaller movements are
anticipated, computed passive pressures shall be reduced
appropriately.
4.3.2—Braced Excavations
C4.3.2
For braced retaining structures with two or more levels of
bracings, design shall be based on apparent earth pressure
diagrams given by empirical methods or any other acceptable
earth pressure distribution developed for this purpose. The
apparent earth pressure diagrams in Figures 4.3.2-1 and
4.3.2-2 are reproduced from the LRFD Bridge Design
Specification. Figure 4.3.2-2 shall be used when:
Bracing should be designed for various stages of the
excavation, corresponding to the cuts necessary to install
the braces at each level. The uppermost stage is analyzed
for a cantilever condition, using active pressures. The next
stage with a single brace is also analyzed using active
pressures and passive pressures. The braced case empirical
diagrams are generally used for conditions of two or more
levels of bracing.
The location of the hinge point for determining
reactions at bracing levels may be estimated from the
position of net zero pressure (where the passive pressure
equals the active or the empirical design pressure). The wall
elements must have sufficient embedment below the
assumed hinge position to obtain passive reaction greater
than the required toe reaction.
The design of braces should include allowances for
thermal
changes
from
ambient
temperatures,
misalignments, and impact from construction activities.
stability number = γH/Su > 6.0
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Using Figures 4.3.2-1 and 4.3.2-2, reaction at the bracing
levels shall be determined by assuming simple hinges at the
bracing points and a fictitious hinge below the cut level.
Penetration of sheathing shall be sufficient so that enough
passive soil resistance can be developed. The lower hinge
point shall depend on the strength of soil, depth of cut,
duration, and the type of retention system. For normal soils,
this depth would be in the range of 2 to 6 ft below the
excavation level and may be assumed at the point of zero net
pressure. Wall elements may be designed for the same
pressures, assuming hinges at support points.
Alternate design methods based on active and passive
pressures and staged excavations with continuous wall
elements may also be used provided the continuity of wall
elements, soil–structure interaction, and deflections during the
various stages of excavation are considered.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
4-6
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Figure 4.3.2-1—Apparent Earth Pressure
Distributions for Anchored Walls Constructed
from the Top Down in
Cohesionless Soils
Notes:
a. 𝑝𝑝𝑎𝑎 = 𝑘𝑘𝑎𝑎 γ′𝑠𝑠 𝐻𝐻 for one anchor level
b. 𝑝𝑝𝑎𝑎 = 𝑘𝑘𝑎𝑎 γ′𝑠𝑠 𝐻𝐻 2 ⁄(1.5𝐻𝐻 − 0.5𝐻𝐻1 − 0.5𝐻𝐻𝑛𝑛+1 ) for
multiple anchor levels
c. 𝑘𝑘𝑎𝑎 = tan2 �45° − ϕ𝑓𝑓 /2� for β = 0
e.
f.
𝑘𝑘𝑎𝑎 =
sin2 �θ+ϕ′f �
Γ[sin2 θ sin(θ−δ) ]
T = �1 + �
for β ≠ 0
sin�ϕ′f +δ�sin�ϕ′f −β�
sin(θ−δ)sin(θ+β)
�
2
Surcharge and water pressures must be added to
|these earth pressure diagrams.
Notation:
H = final wall height (ft)
𝑘𝑘𝑎𝑎 = active earth pressure coefficient
ϕf = angle of internal friction (degrees)
ϕ′f = effective angle of internal friction (degrees)
θ = angle of back of wall to the horizontal (degrees)
δ = friction angle between fill and wall (degrees)
γ′s = effective soil unit weight (kcf)
γ𝑠𝑠 = total soil unit weight (kcf)
T
= horizontal load in ground anchor (kip/ft)
R = reaction to be resisted by subgrade (kip/ft)
β = slope of backfill surface behind retaining
wall: (+) for slope up from wall, (-)
for slope down from wall (degrees)
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
d.
SECTION 4: TEMPORARY RETAINING STRUCTURES
4-7
Figure 4.3.2-2—Apparent Earth Pressure
Distribution for Anchored Walls Constructed from
the Top Down in Soft to Medium Stiff Cohesive
Soils
Notes:
a. 𝑝𝑝𝑎𝑎 = 0.2γs 𝐻𝐻 to 0.4γ𝑠𝑠 𝐻𝐻 for stiff to hard soils
b. 𝑝𝑝𝑎𝑎 = 𝑘𝑘𝑎𝑎 γ𝑠𝑠 𝐻𝐻 for soft to medium stiff soils
4𝑆𝑆
𝑑𝑑 1−5.14𝑆𝑆𝑢𝑢𝑢𝑢
c. 𝑘𝑘𝑎𝑎 = 1 − 𝑢𝑢 + 2√2 �
� ≥ 0.22
γs 𝐻𝐻
𝐻𝐻
γ𝑠𝑠 𝐻𝐻
Surcharge and water pressures must be added to
these earth pressure diagrams.
Notation:
𝑘𝑘𝑎𝑎 = active earth pressure coefficient
𝑆𝑆𝑢𝑢 = undrained strength of retained soil (ksf)
𝑆𝑆𝑢𝑢𝑢𝑢 = undrained strength of soil below excavation
base (ksf)
γ𝑠𝑠 = effective soil unit weight (kcf)
H = final wall height (ft)
T
= horizontal load in ground anchor (kip/ft)
R = reaction to be resisted by subgrade (kip/ft)
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
d.
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
a) Embedment in Granular Soil
b) Embedment in Rock
Figure 4.3.2-3—Unfactored Simplified Earth
Pressure Distributions for Permanent
Non-Gravity Cantilevered Walls with Discrete
Vertical Wall Elements
Notes:
a. For temporary walls embedded in granular soil
or rock, see above figure, determine passive
resistance, and use diagrams in Figure 4.3.2-5 to
determine active earth pressure of retained soil.
b. Surcharge and water pressures must be added to
the indicated earth pressures.
c. Forces shown are per vertical wall element.
d. Pressure distributions below the exposed portion
of the wall are based on an effective element
width of 3b, which is valid for l ≥ 5b. For l < 5b,
refer to Figures 4.3.2-4 and 4.3.2-6 for
continuous wall elements to determine pressured
distributions on embedded portions of the wall.
e. Refer to Reference 5 for determination of ka and
kp.
Notation:
γ′𝑠𝑠 = effective unit weight of soil (kcf)
b = vertical element width (ft)
l
= spacing between vertical wall elements (c/c)
(ft)
𝑆𝑆𝑚𝑚 = shear strength of rock mass (ksf)
𝑝𝑝𝑝𝑝 = passive resistance per vertical wall element
(ksf)
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
4-8
SECTION 4: TEMPORARY RETAINING STRUCTURES
𝑝𝑝𝑎𝑎
β
β′
𝑘𝑘𝑎𝑎
𝑘𝑘𝑝𝑝
= active earth pressure per vertical wall element (ksf)
= ground surface slope behind wall: (+) for
slope up from wall, (–) for slope down
from wall (degrees)
= ground surface slope in front of wall: (+)
for slope up from wall, (–) for slope down
from wall (degrees)
= active earth pressure coefficient
= passive earth pressure coefficient
ϕ𝑓𝑓 = angle of internal friction (degrees)
Figure 4.3.2-4—Unfactored Simplified Earth
Pressure Distribution and Design Procedures for
Permanent Non-Gravity Cantilevered Walls
with Continuous Vertical Wall Elements
Embedded in Granular Soil Modified after Teng
(1962)
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Notes:
a. Surcharge and water pressures must be added to
the above earth pressures.
b. Forces shown are per horizontal foot of vertical
wall element.
1.
Determine the active earth pressure on the wall
due to surcharge loads, the retained soil, and
differential water pressure above the design grade
(refer to AASHTO Standard Specifications for
Highway Bridges for determination of ka).
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
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Provided by IHS Markit under license with AASHTO
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4-9
4-10
3.
4.
5.
6.
7.
Determine the magnitude of active pressure at the
design grade (𝑝𝑝∗ = 𝑘𝑘𝑎𝑎2 γ1′ 𝐻𝐻) due to surcharge
loads, retained soil, and differential water
pressure, using the earth pressure coefficient ka2.
Determine the value of x = 𝑝𝑝∗ /��𝑘𝑘𝑝𝑝2 − 𝑘𝑘𝑎𝑎2 �γ′2 �
for the distribution of net passive pressure in front
of the wall below the design grade (refer to
AASHTO Standard Specifications for Highway
Bridges for determination of ka and kp).
Sum moments about the point of action of F to
determine the embedment (D0) for which the net
passive pressure is sufficient to provide
equilibrium.
Determine the depth (point α) at which the shear in
the wall is zero (i.e., the point at which the areas
of the driving and resisting pressure diagrams are
equivalent).
Calculate the maximum bending moment at the
point of zero shear.
Calculate the design depth, D = 1.2D0 to 1.4D0
for a safety factor of 1.5 to 2.0.
a) Embedment in cohesive soil retaining granular soil
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
2.
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
b) Embedment in cohesive soil retaining cohesive soil
Figure 4.3.2-5—Unfactored Simplified Earth
Pressure Distributions for Temporary Nongravity
Cantilevered Walls with Discrete Vertical Wall
Elements
Notes:
a. For temporary walls embedded in granular soil or
rock, refer to Figure 4.3.2-3 to determine
passive resistance and use diagrams in
above figure to determine active earth pressure
of retained soil.
b. Surcharge and water pressures must be added to
the indicated earth pressures.
c. Forces shown are per vertical wall element.
d. Pressure distributions below the exposed portion
of the wall are based on an effective element
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
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No reproduction or networking permitted without license from IHS
SECTION 4: TEMPORARY RETAINING STRUCTURES
e.
f.
g.
h.
4-11
width of 3b, which is valid for 1 ≥ 5b. For 1 < 5b,
refer to Figures 4.3.2-4 and 4.3.2-6 for continuous wall
elements to determine pressured distributions on
embedded portions of the wall
The ratio of total overburden pressure to
undrained shear strength, 𝑁𝑁𝑠𝑠 , should be < 3 at
wall base.
The active earth pressure shall not be less than
0.25 times the effective overburden pressure at
any depth, or 0.035 ksf/ft of wall height,
whichever is greater.
In Figure 4.3.2-5(b), a portion of negative loading
at the top of the wall due to cohesion is ignored
and hydrostatic pressure in a tension crack should
be considered, but is not shown in the figure.
Refer to Reference 5 for determination of ka.
a)
Embedment in cohesive soil retaining granular soil
Figure 4.3.2-6—Unfactored Simplified Earth
Pressure Distributions for Temporary Non-Gravity
Cantilevered Walls with Continuous Vertical Wall
Elements [modified after Teng (1962)]
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Notation:
γ′𝑠𝑠 = effective unit weight of soil (kcf)
b
= vertical element width (ft)
l
= spacing between vertical wall elements (c/c) (ft)
𝑆𝑆𝑢𝑢 = undrained shear strength of cohesive soil (ksf)
𝑝𝑝𝑝𝑝 = passive resistance per vertical wall element (ksf)
𝑝𝑝𝑎𝑎 = active earth pressure per vertical wall element
(ksf)
β
= ground surface slope behind wall: ( + ) for slope
up from wall, (–) for slope down from wall
(degrees)
β′ = ground surface slope in front of wall: ( + ) for
slope up from wall, (–) for slope sown from
wall (degrees)
𝑘𝑘𝑎𝑎 = active earth pressure coefficient
ϕ𝑓𝑓 = angle of internal friction (degrees)
4-12
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
b) Embedment in cohesive soil retaining cohesive soil
Figure 4.3.2-6 (cont.)—Unfactored Simplified
Earth Pressure Distributions for Temporary
Non-Gravity Cantilevered Walls with Continuous
Vertical Wall Elements [modified after Teng
(1962)]
Notes:
a. For walls embedded in granular soil, refer to
Figure 4.3.3-4 and use above diagram for
retained cohesive soil when appropriate.
b. Refer to Figure 4.3.2-4 for simplified design
procedure.
c. Surcharge and water pressures must be added
to the above earth pressure.
d.
e.
f.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
g.
Forces shown are per horizontal foot of vertical wall
element.
The ratio of total overburden pressure to
undrained shear strength, 𝑁𝑁𝑠𝑠 , should be < 3 at
wall base.
The active earth pressure shall not be less than
0.25 times the effective overburden pressure at
any depth, or 0.035 ksf/ft of wall height,
whichever is greater.
Refer to Reference 5 for determination of 𝑘𝑘𝑎𝑎 .
Notation:
= effective unit weight of soil (kcf)
γ′𝑠𝑠
𝑆𝑆𝑢𝑢 = undrained shear strength of cohesive soil
(ksf)
β
= ground surface slope behind wall: ( + ) for
slope up from wall, ( - ) for slope down from
wall (degrees)
𝑘𝑘𝑎𝑎 = active earth pressure coefficient
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
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SECTION 4: TEMPORARY RETAINING STRUCTURES
4-13
4.3.3—Surcharge Pressures
C4.3.3
In addition to soil and hydrostatic pressures, the retaining
structure shall be designed to include the effect of surcharge
loads acting within a 1.5 (horizontal): 1 (vertical) zone from
the base of the excavation. Surcharge lateral pressures shall be
evaluated using the same earth pressure coefficient as for the
active soil pressures or using elastic solution charts and tables
given in NAVFAC DM-7 or any standard textbook on soil
mechanics.
Surcharges near an excavation are varied in form (for
example, existing foundations, proposed foundations,
embankments, and construction equipment). Ground
pressure on the crane tracks or pads varies during the
operation of the crane. Surcharge effects should be analyzed
for the most severe loading conditions. Charts are available
in many soil mechanics textbooks and handbooks for
analysis of lateral pressure due to various configurations of
loadings.
4.4—STABILITY
C4.4
Overall stability of a sloped excavation or a retained
excavation shall be investigated by limit equilibrium methods
or empirical methods. Charts and figures for stability analyses
are available in standard textbooks in soil mechanics. A
computer program based on the Simplified Bishop method or
the Janbu method can also be used for stability analysis. The
minimum factor of safety shall be 1.3.
For excavations in cohesive soils, stability against basal
heave shall be investigated, using standard methods or
empirical charts given in NAVFAC DM-7 and other
textbooks on soil mechanics. Critical conditions shall be
evaluated by a licensed geotechnical engineer.
Excavations in wet cohesionless soils shall be evaluated
against piping or basal quick conditions by use of flow nets or
charts for control of ground water seepage, as given in
NAVFAC DM-7. Similar charts are also available in standard
textbooks in geotechnical engineering. In layered soil, blowup
of cohesive soil layers due to hydrostatic pressure in
underlying cohesionless layers shall be considered. Where
conditions require, a pressure relief system shall be provided.
Variations of loadings on different sides of a cofferdam
due to different ground levels and surcharge loadings shall be
evaluated.
Where simplified analyses indicate critical stability
conditions, methods for improvement of the soil conditions
should be implemented. These methods depend on soil,
ground water, depth of cut, and many other factors.
Consultation with an experienced geotechnical engineer is
recommended for such a condition.
4.5—COFFERDAMS
C4.5
Temporary cofferdams for construction of bridge
foundations shall be designed for soil and water pressures and
other loads and factors as outlined in the previous sections.
Design water levels shall be specified on the drawings with
provision for wave height.
Cofferdam size shall be adequate for the construction of
the foundations and structure within it. Allowance in size shall
be made of possible misalignment of the wall elements during
their installation (driving) of sheet piles or soldier piles,
presence of obstructions, and anticipated movements. In
braced excavations, encroachments by walers and struts shall
be considered.
The shape and size of a cofferdam is usually selected
by the Contractor. The minimum size should be sufficient
to construct the specified foundation. If piled foundations
are to be constructed, strut and waler locations should be
adjusted to allow installation of the piles.
4.5.1—Cantilever Walls
C4.5.1
Cantilever systems shall have a factor of safety against
overturning of at least 1.5. Figures 4.3.2-3 through 4.3.2-6,
reproduced from the AASHTO LRFD Bridge Design
Specifications, are diagrams of active and passive pressures
for analysis of cantilever systems.
Assumptions made in the design of cantilever walls
should be shown on the drawings. This is particularly
important for surcharges, depths of cuts, water table, and
dewatering requirements. In the case of cohesive soils,
passive pressure on the embedded portion of the wall shall
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
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4-14
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Embedment depth of sheet piles in wet cohesionless soils
shall be adequate to control piping with a minimum factor of
safety of 1.5.
not exceed 2Sᵤ in the case that the active pressure at the cut
level on the soil side (i.e. γH – 2c) is negative.
4.5.2—Braced Cofferdams
C4.5.2
Braced cofferdams in dry conditions shall be designed as
a structure to resist loads as outlined in the previous sections.
The designer shall specify the design assumptions including
soil parameters, ground water levels outside and inside the
cofferdam during various stages of excavation, and the cut
levels when braces are to be installed. For cofferdams in wet
construction, any installation of bracing under water and prior
to interior excavation shall be so specified. Design loads for
the braces and required preloads shall be indicated on the
design drawings.
Cofferdams in wet conditions such as those for
construction of foundations in a body of water shall be
designed for conditions occurring during various stages of
construction, considering the stability of basal soils, the
cofferdam, and the structure to be constructed. Where
hydrostatic uplift cannot be controlled by dewatering alone, a
tremie seal shall be designed to resist hydrostatic uplift during
dewatering.
Resistance of tremie seals shall be based on the weight of
the seal concrete, the cofferdam elements, and the foundation
piles, if any, bonded to the tremie seal. Skin frictional
resistance of piling and cofferdam elements (for example,
sheeting) below the depth of excavation shall be evaluated
based on the effective stress principles, but shall not exceed
100 psf.
Provision shall be made for flooding of the cofferdam at
stages of water level exceeding the design water level of the
tremie seal.
Cofferdams in a navigable channel shall be designed for
impact from waterway traffic and/or flowing ice or suitably
protected from impact. Loads imposed by work barges and
from flowing water and/or ice shall be included along with
dynamic forces from fluctuating water level. Dynamic water
pressure from flowing water shall be calculated from:
Design assumption should be clearly indicated on the
drawings so that construction personnel do not violate the
assumptions, and variations from the design assumptions
are approved by the Engineer.
Dynamic Water Pressure from Flowing Water:
𝑃𝑃𝑤𝑤 = Kv² (psf)
(4.5.2-1)
where:
Pw
=
pressure (psf)
V
=
water velocity (ft/s)
K
=
1.375 for square faces
0.67 for circular piers
0.50 for angular faces
These pressures are applicable for both a cantilever and a
braced cofferdam.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
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Officials.
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YANGand
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APPENDIX A
MAXIMUM DESIGN VALUES FOR UNGRADED STRUCTURAL LUMBERa
Stress (psi)
Compression
Horizontal Perpendicular
Shear,
to Grain,
Fv
Fc˔
Extreme
Fiber in
Bending,
Fb
Tension
Parallel
to Grain,
Ft
250
150
180
520
Joists and Planksc
1175
300
180
Beams and Stringersd
825
425
Posts and Timberse
675
Light Framingb
Joists and Planksc
Beams and Stringersd
Posts and Timberse
Modulus of
Elasticity (psi)
Compression
Parallel
to Grain,
Fc
E
Emin
900
1,000,000
370,000
520
775
1,100,000
400,000
165
520
550
1,000,000
370,000
450
165
520
650
1,000,000
370,000
250
150
145
405
850
1,100,000
400,000
500
300
145
405
725
1,200,000
440,000
675
325
135
405
475
1,100,000
400,000
550
375
135
405
575
1,100,000
400,000
Light Framingb
225
125
195
620
375
900,000
330,000
Joists and Planksc
400
250
195
620
325
1,000,000
370,000
Beams and Stringersd
625
325
180
620
375
900,000
330,000
Posts and Timberse
500
350
180
620
300
900,000
330,000
Light Framingb
250
150
170
800
425
800,000
290,000
Joists and Planksc
475
275
170
800
375
800,000
290,000
Beams and Stringersd
725
375
155
800
450
800,000
290,000
Posts and Timberse
575
400
155
800
350
800,000
290,000
Light Framingb
300
175
220
885
500
1,000,000
370,000
Joists and Planksc
550
325
220
885
425
1,200,000
440,000
Beams and Stringersd
875
425
205
885
500
1,000,000
370,000
Posts and Timberse
700
475
205
885
400
1,000,000
370,000
Light Framingb
275
150
210
615
475
1,200,000
440,000
Joists and Planksc
525
300
210
615
400
1,300,000
470,000
Beams and Stringersd
800
400
195
615
475
1,200,000
440,000
Posts and Timberse
650
425
195
615
375
1,200,000
440,000
Species/Size
Classification
DOUGLAS FIR-LARCH
(All sub-species)
Light Framingb
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
HEM-FIR
(All sub-species)
MIXED MAPLE
MIXED OAK
NORTHERN RED OAK
RED MAPLE
A-1
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
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A-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
APPENDIX A
MAXIMUM DESIGN VALUES FOR UNGRADED STRUCTURAL LUMBERa (CONT.)
Stress (psi)
Compression
Horizontal Perpendicular
Shear,
to Grain,
Fv
Fc˔
Extreme
Fiber in
Bending,
Fb
Tension
Parallel
to Grain,
Ft
Light Framingb
250
150
170
820
Joists and Planksc
475
275
170
Beams and Stringersd
725
375
Posts and Timberse
575
Light Framingb
Joists and Planksc
Beams and Stringersd
Posts and Timberse
Compression
Parallel
to Grain,
Fc
Modulus of Elasticity
(psi)
E
Emin
425
1,000,000
370,000
820
375
1,100,000
400,000
155
820
450
1,000,000
370,000
400
155
820
350
1,000,000
370,000
575
325
175
565
825
1,400,000
510,000
575
325
175
565
825
1,400,000
510,000
850
550
165
375
525
1,200,000
440,000
850
550
165
375
525
1,200,000
440,000
Light Framingb
225
100
135
335
675
900,000
330,000
Joists and Planksc
450
200
135
335
575
1,000,000
370,000
Beams and Stringersd
575
300
125
335
375
1,000,000
370,000
Posts and Timberse
475
325
125
335
425
1,000,000
370,000
Light Framingb
250
150
220
800
475
800,000
290,000
Joists and Planksc
475
275
220
800
400
800,000
290,000
Beams and Stringersd
750
375
205
800
475
800,000
290,000
Posts and Timberse
600
400
205
800
400
800,000
290,000
Species/Size
Classification
RED OAK
SOUTHERN PINEf
SPRUCE-PINE-FIR
(All sub-species)
WHITE OAK
Notes:
a. Tabulated values are generally based on the lowest stresses for each size classification and apply only for normal load duration and dry surface
conditions unless noted otherwise. Refer to NDS for a description of applicable adjustment factors and species designation.
b. Lumber nominally 2 in. to 4 in. thick, and a maximum of 4 in. wide. Tabulated values shall be adjusted for all applicable factors given in
NDS Table 4A, except for size.
c. Lumber nominally 2 in. to 4 in. thick, and at least 5 in. wide. Tabulated values shall be adjusted for all applicable factors given in NDS
Table 4A, except for size.
d. Timber of rectangular cross section, nominally at least 5 in. thick with a width more than 2 in. greater than the thickness (e.g. 6 × 10, 8 × 14).
Refer to NDS Part IV for restrictions related to use of resawn, cantilevered, continuous, and flatwise use of beams and stringers.
e. Timber of approximately square cross section, nominally at least 5 in. square with the larger dimension not more than 2 in. greater than the
smaller dimension (e.g., 6 × 6, 6 × 8, 12 × 14).
f. Wet service condition.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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APPENDIX B
AISC 360-10 PROVISIONS FOR WEBS AND FLANGES WITH CONCENTRATED FORCES
This section applies to single- and double-concentrated forces applied normal to the flange(s) of wide flange
sections and similar built-up shapes. A single-concentrated force can be either tensile or compressive. Doubleconcentrated forces are one tensile and one compressive and form a couple on the same side of the loaded member.
When the required strength exceeds the available strength as determined for the limit states listed in this
section, stiffeners and/or doublers shall be provided and shall be sized for the difference between the required strength
and the available strength for the applicable limit state. Stiffeners shall also meet the design requirements in
Section B.8. Doublers shall also meet the design requirement in Section B.9. See AISC 360-10 Appendix 6.3 for
requirements for the ends of cantilever members.
Stiffeners are required at unframed ends of beams in accordance with the requirements of Section B.7.
B.1—Flange Local Bending
This section applies to tensile single-concentrated forces and the tensile component of double-concentrated
forces.
The design strength, ϕ𝑅𝑅𝑛𝑛 , and the allowable strength, 𝑅𝑅𝑛𝑛 /Ω, for the limit state of flange local bending shall
be determined as follows:
𝑅𝑅𝑛𝑛 = 6.25𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓 2
Ω = 1.67 (ASD)
ϕ = 0.90 (LRFD)
where:
𝐹𝐹𝑦𝑦𝑦𝑦
𝑡𝑡𝑓𝑓
(B-1)
= specified minimum yield stress of the flange, ksi
= thickness of the loaded flange, in.
If the length of loading across the member flange is less than 0.15bf, where bf is the member flange width,
Eq. B-1 need not be checked.
When the concentrated force to be resisted is applied at a distance from the member end that is less than
10𝑡𝑡𝑓𝑓 ,𝑅𝑅𝑛𝑛 shall be reduced by 50 percent.
When required, a pair of transverse stiffeners shall be provided.
B.2—Web Local Yielding
This section applies to single-concentrated forces and both components of double-concentrated forces.
The available strength for the limit state of web local yielding shall be determined as follows:
ϕ = 1.00 (LRFD)
Ω = 1.50 (ASD)
B-1
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
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Officials.
Sold to:QING
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B-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
The nominal strength, 𝑅𝑅𝑛𝑛 , shall be determined as follows:
(a) When the concentrated force to be resisted is applied at a distance from the member end that is greater than the
depth of the member d,
(B-2)
𝑅𝑅𝑛𝑛 = 𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑤𝑤 (5k + lb)
(b) When the concentrated force to be resisted is applied at a distance from the member end that is less than or equal
to the depth of the member d,
𝑅𝑅𝑛𝑛 = 𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑤𝑤 (2.5k + lb)
(B-3)
where:
= specified minimum yield stress of the web, ksi
= web thickness, in.
= distance from outer face of the flange to the web toe of the fillet, in.
= length of bearing (not less than k for end beam reactions), in.
Fyw
Tw
k
lb
When required, a pair of transverse stiffeners or a doubler plate shall be provided.
B.3—Web Local Crippling
ϕ = 0.75 (LRFD)
Ω = 2.00 (ASD)
The nominal strength, 𝑅𝑅𝑛𝑛 , shall be determined as follows:
(a) When the concentrated compressive force to be resisted is applied at a distance from the member end that is greater
than or equal to d/2:
𝑙𝑙
𝑡𝑡
1.5
Rn = 0.80 𝑡𝑡𝑤𝑤2 �1 + 3 � 𝑏𝑏 � � 𝑤𝑤� � �
𝑑𝑑
𝑡𝑡𝑓𝑓
(B-4)
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
𝑡𝑡𝑤𝑤
(b) When the concentrated compressive force to be resisted is applied at a distance from the member end that is less
than d/2:
(i) For lb / d ≤ 0.2
(ii) For lb / d > 0.2
𝑡𝑡
1.5
𝑑𝑑
4𝑙𝑙
𝑡𝑡𝑓𝑓
(B-5a)
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
𝑡𝑡
𝑡𝑡𝑤𝑤
1.5
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
Rn = 0.40 𝑡𝑡𝑤𝑤2 �1 + � 𝑏𝑏 − 0.2� � 𝑤𝑤� � �
𝑑𝑑
𝑡𝑡
where:
𝑑𝑑
𝑙𝑙
Rn = 0.40𝑡𝑡𝑤𝑤2 �1 + 3 � 𝑏𝑏 � � 𝑤𝑤� � �
𝑓𝑓
𝑡𝑡𝑤𝑤
= full nominal depth of the section, in.
Wh
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
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(B-5b)
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
This section applies to compressive single-concentrated forces or the compressive component of doubleconcentrated forces.
The available strength for the limit state of web local crippling shall be determined as follows:
APPENDIX B: AISC 360-10 PROVISIONS
B-3
en required, a transverse stiffener, a pair of transverse stiffeners, or a doubler plate extending at least onehalf the depth of the web shall be provided.
B.4—Web Sideway Buckling
This Section applies only to compressive single-concentrated forces applied to members where relative
lateral movement between the loaded compression flange and the tension flange is not restrained at the point of
application of the concentrated force.
The available strength of the web for the limit state of web sideways buckling shall be determined as follows:
ϕ = 0.85 (LRFD)
Ω = 1.76 (ASD)
The nominal strength, 𝑅𝑅𝑛𝑛 , shall be determined as follows:
(a) If the compression flange is restrained against rotation:
(i) When (h /tw) / (lb /bf) ≤ 2.3
𝑅𝑅𝑛𝑛 =
3
𝐶𝐶𝑟𝑟 𝑡𝑡𝑤𝑤3 𝑡𝑡𝑓𝑓
ℎ/ 𝑡𝑡𝑤𝑤
�1 + 0.4 �
� �
2
ℎ
𝑙𝑙𝑏𝑏 /𝑏𝑏𝑓𝑓
(B-6)
(ii) When (h /tw) / (lb /bf) > 2.3, the limit state of web sideway bucking does not apply.
When the required strength of the web exceeds the available strength, local lateral bracing shall be provided
at the tension flange or either a pair of transverse stiffeners or a doubler plate shall be provided.
(b) If the compression flange is not restrained against rotation:
(i) For (h /tw) / (lb /bf) ≤ 1.7
𝑅𝑅𝑛𝑛 =
3
𝐶𝐶𝑟𝑟 𝑡𝑡𝑤𝑤3 𝑡𝑡𝑓𝑓
ℎ/ 𝑡𝑡𝑤𝑤
�0.4 �
� �
2
ℎ
𝑙𝑙𝑏𝑏 /𝑏𝑏𝑓𝑓
(B-7)
(ii) For (h /tw) / (lb /bf) > 1.7, the limit state of web sideway buckling does not apply.
When the required strength of the web exceeds the available strength, local lateral bracing shall be provided
at both flanges at the point of application of the concentrated forces.
In Eqs. B-6 and B-7, the following definitions apply:
bf
Cr
h
= width of the flange, in.
= 960,000 ksi when 𝑀𝑀𝑢𝑢 < 𝑀𝑀𝑦𝑦 (LRFD) or 1.5 𝑀𝑀𝑎𝑎 < 𝑀𝑀𝑦𝑦 (ASD) at the
location of the force
= 480,000 ksi when 𝑀𝑀𝑢𝑢 ≥ 𝑀𝑀𝑦𝑦 (LRFD) or 1.5 𝑀𝑀𝑎𝑎 ≥ 𝑀𝑀𝑦𝑦 (ASD) at the
location of the force
= clear distance between flanges less the fillet or corner radius for rolled shapes; distance
between adjacent lines of fasteners or the clear distance between flanges when welds are used for
built-up shapes, in.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
is aforviolation
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
B-4
lb
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
= largest laterally unbraced length along either flange at the point of load, in.
Note: For determination of adequate restraint, refer to AISC 360-10 Appendix 6.
B.5—Web Compression Buckling
This Section applies to a pair of compressive single-concentrated forces or the compressive components in
a pair of double-concentrated forces, applied at both flanges of a member at a same location.
The available strength for the limit state of web local buckling shall be determined as follows:
𝑅𝑅𝑛𝑛 =
ϕ = 0.90 (LRFD)
24𝑡𝑡𝑤𝑤3 �𝐸𝐸𝐸𝐸𝑦𝑦𝑦𝑦
ℎ
(B-8)
Ω = 1.67 (ASD)
When the pair of concentrated compressive forces to be resisted is applied at a distance from the member end
that is less than d / 2, 𝑅𝑅𝑛𝑛 shall be reduced by 50 percent.
When required, a single transverse stiffener, a pair of transverse stiffeners, or a doubler plate extending the
full depth of the web shall be provided.
B.6—Web Panel Zone Shear
location.
follows:
This section applies to double-concentrated forces applied to one or both flanges of a member at the same
The available strength of the web panel zone for the limit state of shear yielding shall be determined as
ϕ = 0.90 (LRFD)
Ω = 1.67 (ASD)
The nominal strength, 𝑅𝑅𝑛𝑛 , shall be determined as follows:
(a) When the effect of panel-zone deformation on frame stability is not considered in the analysis:
(i) For 𝑃𝑃𝑟𝑟 ≤ 0.4 𝑃𝑃𝑐𝑐
(ii) For 𝑃𝑃𝑟𝑟 > 0.4 𝑃𝑃𝑐𝑐
(B-9)
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
𝑃𝑃
(B-10)
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1.4 − 𝑟𝑟�
𝑃𝑃𝑐𝑐
(b) When frame stability, including plastic panel-zone deformation, is considered in the analysis:
i) For 𝑃𝑃𝑟𝑟 ≤ 0.75 𝑃𝑃𝑐𝑐
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
APPENDIX B: AISC 360-10 PROVISIONS
ii) For 𝑃𝑃𝑟𝑟 > 0.75 𝑃𝑃𝑐𝑐
B-5
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1 +
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1 +
2
3𝑏𝑏𝑐𝑐𝑐𝑐 𝑡𝑡𝑐𝑐𝑐𝑐
𝑑𝑑𝑏𝑏 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
2
3𝑏𝑏𝑐𝑐𝑐𝑐 𝑡𝑡𝑐𝑐𝑐𝑐
𝑑𝑑𝑏𝑏 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
(B-11)
�
� �1.9 −
1.2𝑃𝑃𝑟𝑟
In Eqs. B-9 through B-12, the following definitions apply:
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Ag
bcf
db
dc
Fy
Pc
Pc
Pr
Py
tcf
tw
𝑃𝑃𝑐𝑐
�
(B-12)
= gross cross-sectional area of member, in.2
= width of column flange, in.
= beam depth, in.
= column depth, in.
= specified minimum yield stress of column web, ksi
= 𝑃𝑃𝑦𝑦 , kips (LRFD)
= 0.60𝑃𝑃𝑦𝑦 , kips (ASD)
= required axial strength using LRFD or ASD load combinations, kips
= 𝐹𝐹𝑦𝑦 𝐴𝐴𝑔𝑔 , axial yield strength of the column, kips
= thickness of the column flange, in.
= thickness of column web, in.
When required, doubler plate(s) or a pair of diagonal stiffeners shall be provided within the boundaries of
the rigid connection whose webs lie in a common plane.
See Section B.9 for doubler plate design requirements.
B.7—Unframed Ends of Beams and Girders
At unframed ends of beams and girders not otherwise restrained against rotation about their longitudinal
axes, a pair of transverse stiffeners, extending the full depth of the web, shall be provided.
B.8—Additional Stiffener Requirements for Concentrated Forces
Stiffeners required to resist tensile concentrated forces shall be designed in accordance with the requirements
of AISC 360-10 Section J4.1 and welded to the loaded flange and the web. The welds to the flange shall be sized for
the difference between the required strength and available strength. The stiffener to web welds shall be sized to
transfer to the web the algebraic difference in tensile force at the ends of the stiffener.
Stiffeners required to resist compressive concentrated forces shall be designed in accordance with the
requirements in AISC 360-10 Section J4.4 and shall either bear on or be welded to the loaded flange and welded to
the web. The welds to the flange shall be sized for the difference between the required strength and the applicable
limit state strength. The weld to the web shall be sized to transfer to the web the algebraic difference in compression
force at the ends of the stiffener. For fitted bearing stiffeners, see AISC 360-10 Section J7.
Transverse full depth bearing stiffeners for compressive forces applied to a beam or plate girder flange(s)
shall be designed as axially compressed members (columns) in accordance with the requirements of AISC 360-10
Sections E6.2 and J4.4. The member properties shall be determined using an effective length of 0.75h and a cross
section composed of two stiffeners and a strip of the web having the width of 25𝑡𝑡𝑤𝑤 at interior stiffeners and 12𝑡𝑡𝑤𝑤 at
the end of members. The weld connecting full depth bearing stiffeners to the web shall be sized to transmit the
difference in compressive force at each of the stiffeners to the web.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
B-6
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Transverse and diagonal stiffeners shall comply with the following additional requirements:
(1) The width of each stiffener plus one-half the thickness of the column web shall not be less than one-third of the
width of the flange or moment connection plate width delivering the concentrated force.
(2) The thickness of a stiffener shall not be less than one-half the thickness of the flange or moment connection plate
delivering the concentrated load, and greater than or equal to the width divided by 16.
(3) Transverse stiffeners shall extend a minimum of one-half the depth of the member expect as required in AISC 36010 Sections J10.5 and J10.7.
B.9—Additional Doubler Plate Requirements for Concentrated Forces
Doubler plates required for compression strength shall be designed in accordance with the requirements of
AISC 360-10 Chapter E.
Doubler plates required for tensile strength shall be designed in accordance with the requirements of AISC
360-10 Chapter D.
Doubler plates required for shear strength (see Section B.6) shall be designed in accordance with the
provisions of AISC 360-10 Chapter G.
Doubler plates shall comply with the following additional requirements:
(1) The thickness and extent of the doubler plate shall provide the additional material necessary to equal or exceed
the strength requirements.
(2) The doubler plate shall be welded to develop the proportion of the total force transmitted to the doubler plate.
Reproduced from Manual of Steel Construction, Fourteenth Edition, copyright © 2010, with the permission of the
American Institute of Steel Construction, Inc.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
is aforviolation
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
APPENDIX C
SELECT ASCE 7 WIND PROVISIONS
This section provides provisions consistent with ASCE 7-10 to determine wind loads on trussed towers, lattice
frameworks, and other solid surfaces. For the determination of wind loads on other types of temporary structures, refer to
ASCE 7-10 Section 26.
C.1—Basic Wind Speed, V
The basic wind speed is the three-second gust wind speed at 33 ft above the ground of Exposure C. Wind speeds
correspond to approximately a 7 percent probability of exceedance in 50 years.
The basic wind speed, V, used in the determination of design wind loads on buildings and other structures shall be given
in Figure C.1, except as follows. Mountainous terrain, gorges, and special wind regions shown in Figure C.1 shall be
examined for unusual wind conditions as outlined in ASCE 7-10 Section 26.5.2. The estimation of basic wind speeds from
regional climatic data shall be allowed as outlined in ASCE 7-10 Section 26.5.3. The basic wind speed used shall be at
least 110 mph.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
C.2—Design Wind Force, F
The wind force for each primary axis of trussed towers and lattice frameworks shall be determined from
Eq. C-1:
F = qz G Cf Af (lb)
(C-1)
where:
=
=
=
=
=
=
=
=
qz
Kz
Kzt
Kd
V
G
Cf
Af
velocity pressure = 0.00256 Kz Kzt Kd V2 (psf)
velocity pressure exposure coefficient—see Section C.3
topographic factor—see Section C.4
wind directionality factor—see Section C.5
basic wind speed (mph)—see Figure C.1
gust-effect factor—see Section C.6
force coefficient—see Section C.7
projected area normal to the wind—see Section C.8
The wind force for each primary axis of solid surfaces shall be determined from Eq. C-2:
F = qh G Cf Ag (lb)
(C-2)
where:
qh
Kz
Kzt
Kd
V
G
Cf
Ag
=
=
=
=
=
=
=
=
velocity pressure = 0.00256 Kz Kzt Kd V2 (psf), evaluated at height h (defined in Table C.5.)
velocity pressure exposure coefficient—see Section C.3
topographic factor—see Section C.4
wind directionality factor—see Section C.5
basic wind speed (mph)—see Figure C.1
gust-effect factor—see Section C.6
force coefficient—see Section C.7
gross area of solid surface
For each primary axis of the structure, 50 percent of the wind load calculated for the perpendicular direction shall be
assumed to act simultaneously.
C-1
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
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C-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
C.3—Velocity Pressure Exposure Coefficient, Kz
The velocity pressure exposure coefficient shall be determined from Table C.1 1 following the determination of the
applicable surface roughness category and exposure category. Surface roughness categories and exposure categories are
as follows:
(a) Surface Roughness Categories
Surface Roughness B—Surface Roughness B is defined as 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—Surface Roughness C is defined as open terrain with scattered obstructions having heights generally
less than 30 ft. This category includes flat open country and grasslands.
Surface Roughness D—Surface Roughness D is defined as flat, unobstructed areas and water surfaces. This category
includes smooth mud flats, salt flats, and unbroken ice.
(b) Exposure Categories
Exposure B—For structures with a mean roof height of less than or equal to 30 ft., Exposure B shall apply where the ground
surface roughness, as defined by Surface Roughness B, prevails in the upwind direction for a distance greater than 1,500
ft. For structures with a mean roof height greater than 30 ft, Exposure B shall apply where Surface Roughness B prevails
in the upwind direction for a distance greater than 2,600 ft or 20 times the height of the structure, whichever is greater.
Exposure C— Exposure C shall apply for all cases where Exposures B or D do 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 greater than 5,000 ft or 20 times the structure height, whichever is greater. Exposure
D shall also apply where the ground surface roughness immediately upwind of the site is B or C, and the site is within a
distance of 600 ft or 20 times the structure height, whichever is greater, from an Exposure D condition as defined in the
previous sentence.
C.4—Topographic Factor, Kzt
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:
1.
2.
3.
4.
5.
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 2 miles, 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.
The hill, ridge, or escarpment protrudes above the height of upwind terrain features within a 2-mi radius in any
quadrant by a factor of two or more.
The structure is located as shown in Figure C.2 in the upper one-half of a hill or ridge or near the crest of an escarpment.
H/Lh ≥ 0.2.
H is greater than or equal to 15 ft for Exposure C and D and 60 ft. for Exposure B.
Select tables and figures reproduced from ASCE 7-10
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
APPENDIX C: SELECT ASCE 7 WIND PROVISIONS
C-3
The topographic factor, Kzt, shall be determined as follows:
Kzt = (1 + K1K2K3)2 where K1, K2, and K3 are given in Figure C.2.
If site conditions and locations of structures do not meet all the conditions specified above, then Kzt = 1.0.
C.5—Wind Directionality Factor, Kd
The wind directionality factor shall be determined from Table C.2.
C.6—Gust-Effect Factor, G
The gust-effect factor for a rigid building or other structure is permitted to be taken as 0.85.
C.7—Force Coefficient, Cf
The force coefficient for trussed towers shall be determined from Table C.3. The force coefficient for lattice
frameworks shall be determined from Table C.4. The force coefficient for solid surfaces shall be determined from Table
C.5.
C.8—Projected Area, Af
The projected area shall be the solid area of a trussed tower or lattice framework face normal to the wind projected
on the plane of that face for the segment under consideration.
Table C.1—Velocity Pressure Coefficient, 𝑲𝑲𝒛𝒛
Height above
ground level, z
(ft)
Exposure
B
C
D
0-15
0.57
0.85
1.03
20
0.62
0.90
1.08
25
0.66
0.94
1.12
30
0.70
0.98
1.16
40
0.76
1.04
1.22
50
0.81
1.09
1.27
60
0.85
1.13
1.31
70
0.89
1.17
1.34
80
0.93
1.21
1.38
90
0.96
1.24
1.40
100
0.99
1.26
1.43
120
1.04
1.31
1.48
140
1.09
1.36
1.52
160
1.13
1.39
1.55
180
1.17
1.43
1.58
200
1.20
1.46
1.61
250
1.28
1.53
1.68
300
1.35
1.59
1.73
350
1.41
1.64
1.78
400
1.47
1.69
1.82
450
1.52
1.73
1.86
500
1.56
1.77
1.89
Notes:
a.
Linear interpolation for intermediate values of height z is acceptable.
b.
Exposure categories are defined above.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
© 2017 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
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Order Number: 02250056
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Not for Resale,2019-08-14 12:03:30 UTC
C-4
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Table C.2—Wind Directionality Factor, Kd
Structure Type
Kd
Trussed Towers— triangular, square, or rectangular cross sections
0.85
Trussed Towers—all other cross sections
0.95
Open Signs and Lattice Framework
0.85
Table C.3—Force Coefficients for Trussed Towers, Cf
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Tower Cross Section
Cf
Square
4.0ε2 - 5.9ε + 4.0
Triangle
3.4ε2 - 4.7ε + 3.4
Notes:
a. 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.
b. The specified force coefficients are for towers with structural angles or similar flat-sided members.
c. 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:
0.51ε2 + 0.57 but not greater than 1.0.
d.
Wind forces shall be applied in the directions resulting in maximum member forces and reactions. For towers with square crosssections, wind forces shall be multiplied by the following factor when the wind is directed along a tower diagonal:
1 + 0.75ε but not greater than 1.2.
e.
f.
g.
Wind forces on tower appurtenances such as ladders, conduits, lights, elevators, etc., shall be calculated using appropriate force
coefficients for these elements.
Loads due to ice accretion shall be accounted for.
Notation:
ε: ratio of solid area to gross area of one tower face for the segment under consideration.
Table C.4—Force Coefficients for Open Signs & Lattice Frameworks, Cf
ε
Flat-Sided
Members
< 0.1
Rounded Members
2.0
𝑫𝑫�𝒒𝒒𝒛𝒛 ≤ 𝟐𝟐. 𝟓𝟓
(𝑫𝑫�𝒒𝒒𝒛𝒛 ≤ 𝟓𝟓. 𝟑𝟑)
1.2
𝑫𝑫�𝒒𝒒𝒛𝒛 > 𝟐𝟐. 𝟓𝟓
(𝑫𝑫�𝒒𝒒𝒛𝒛 > 𝟓𝟓. 𝟑𝟑)
0.1 to 0.29
1.8
1.3
0.9
0.3 to 0.7
1.6
1.5
1.1
0.8
Notes:
a. Signs with openings comprising 30 percent or more of the gross area are classified as open signs.
b. 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.
c. The area, Af, consistent with these coefficients is the solid area projected normal to the wind direction.
d. Notation:
ε: ratio of solid area to gross area;
D: diameter of a typical round member, in ft; and
qz: velocity pressure evaluated at height z above ground in psf.
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
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[248215100001]
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Copyright American Association of State Highway and Transportation Officials
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APPENDIX C: SELECT ASCE 7 WIND PROVISIONS
Table C.5—Force Coefficients for Solid Freestanding Walls and Signs
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
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C-5
C-6
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Figure C.1(a)—Basic Wind Speeds for Occupancy Category II Building and Other Structures
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
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C-7
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
APPENDIX C: SELECT ASCE 7 WIND PROVISIONS
Figure C.1(a)—Basic Wind Speeds for Occupancy Category II Building and Other Structures (cont.)
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C-8
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Figure C.1(b)—Basic Wind Speeds for Occupancy Category III and IV Buildings and Other Structures
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APPENDIX C: SELECT ASCE 7 WIND PROVISIONS
C-9
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Figure C.1(b)—Basic Wind Speeds for Occupancy Category III and IV Buildings and Other Structures (cont.)
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AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
C-10
Figure C.2—Topographic Multipliers for Exposure C
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APPENDIX C: SELECT ASCE 7 WIND PROVISIONS
Figure C.2—Topographic Multipliers for Exposure C (cont.)
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
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C-11
APPENDIX D
SELECT ASCE 7 SEISMIC PROVISIONS
This section provides provisions consistent with ASCE 7-10 to determine seismic loads on falsework towers less
than 60 feet in height. For the determination of seismic loads on other types and heights of temporary structures, refer
to ASCE 7-10.
D.1—Risk-Targeted Maximum Considered Earthquake, MCER
This section provides the 5 percent damped, risk-targeted maximum considered earthquake (MCER) spectral
response acceleration parameter at a period of 1 s for the United States, S1, reproduced from ASCE 7-10. Yellow
shading indicates those locations where S1 equals or exceeds 0.40.
Earthquake loads need not be considered unless required by the authority having jurisdiction and the mapped
MCER, 5 percent damped, spectral response acceleration parameter at a period of 1 second, S1, defined in Section
11.4.1 of ASCE 7, equals or exceeds 0.40.
Larger, more detailed versions of these maps are no longer provided with the 2010 publication of ASCE 7. It is
recommended that the corresponding USGS web tool (http://earthquake.usgs.gov/designmaps/us/application.php) be
used to determine the mapped value for a specific location.
In addition, if earthquake loads must be considered, the 5 percent damped, risk-targeted maximum considered
earthquake (MCER) spectral response acceleration parameter at short periods for the United States, SS, can also be
determined using the USGS web tool.
D.2—Site Class and Site Coefficients, Fa and Fv
Based on site soil properties, the site shall be classified as Site Class A, B, C, D, E, or F in accordance with ASCE
7-10 Chapter 20. If a building site is classified as Site Class F, refer to ASCE 7-10.
The site coefficients Fa and Fv shall be determined based on the Site Class and MCER parameters at short periods
and 1 s using Tables D.1 and D.2 below.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Site Class
A
B
C
D
E
SS ≤ 0.25
0.8
1.0
1.2
1.6
2.5
Table D.1 Site Coefficient, Fa
SS = 0.5
SS = 0.75
0.8
0.8
1.0
1.0
1.2
1.1
1.4
1.2
1.7
1.2
SS = 1.0
0.8
1.0
1.0
1.1
0.9
SS ≥ 1.25
0.8
1.0
1.0
1.0
0.9
Site Class
A
B
C
D
E
S1 ≤ 0.1
0.8
1.0
1.7
2.4
3.5
Table D.2 Site Coefficient, Fv
S1 = 0.2
S1 = 0.3
0.8
0.8
1.0
1.0
1.6
1.5
2.0
1.8
3.2
2.8
S1 = 0.4
0.8
1.0
1.4
1.6
2.4
S1 ≥ 0.5
0.8
1.0
1.3
1.5
2.4
D-1
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D-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
D.3—Design Spectral Acceleration Parameters, SDS and SD1
The design spectral acceleration parameters shall be determined from Equations D-1 and D-2:
SDS = 2/3FaSS
(D-1)
SD1 = 2/3FvS1
(D-2)
D.4—Estimate Fundamental Period of Falsework, Ta
The approximate fundamental period shall be determined from Equation D-3:
Ta = 0.02 hn0.75
where:
(D-3)
hn = the vertical distance from the base, or ground, to the highest level of the falsework
D.5—Seismic Response Coefficient, Cs
The seismic response coefficient shall be determined from Equation D-4 but shall not exceed the value determined
from Equation D-5:
Cs = SDS / 2.5
(D-4)
Cs = SD1 / (2.5Ta)
(D-5)
D.6—Seismic Base Shear and Equivalent Lateral Force, V and Feq
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
The design seismic base shear shall be determined from Equation D-6:
V = CsW
(D-6)
where: W = effective seismic weight of the falsework and supported structure
The equivalent lateral seismic force applied to the falsework shall be equal to the base shear and applied at
the top of the falsework, unless an alternate force distribution is determined based on ASCE 7-10 or rational
engineering principles.
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APPENDIX D: SELECT ASCE 7 SEISMIC PROVISIONS
D-3
FIGURE D.1(a) S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion Parameter for the Conterminous
United States for 1.0 sec Spectral Response Acceleration (5 Percent of Critical Damping), Site Class B.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
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D-4
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
FIGURE D.1(b) S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion Parameter for the
Conterminous United States for 1.0 sec Spectral Response Acceleration (5 Percent of Critical Damping), Site Class B.
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APPENDIX D: SELECT ASCE 7 SEISMIC PROVISIONS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
FIGURE D.2 S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion Parameter for Alaska for 1.0 sec Spectral Response Acceleration (5
Percent of Critical Damping), Site Class B.
D-5
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AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
D-6
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
FIGURE D.3 S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion Parameter for Hawaii for 1.0
sec Spectral Response Acceleration (5 Percent of Critical Damping), Site Class B.
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D-7
IGURE D.4 S1 Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion Parameter for Puerto Rico and
the United States Virgin Islands for 1.0 sec Spectral Response Acceleration (5 Percent of Critical Damping), Site Class B.
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--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
APPENDIX D: SELECT ASCE 7 SEISMIC PROVISIONS
APPENDIX E
SAMPLE WIND AND SEISMIC CALCULATIONS
EXAMPLE 1—WIND LOAD ON FALSEWORK
Problem Description
Determine the horizontal load to be applied to falsework Bent A shown in Figure E-1. Specifically investigate the
following items:
•
•
•
Calculate design wind pressure for the applicable height zones.
Calculate wind load and overturning moment for Bent A.
Calculate horizontal load due to dead load.
•
Tower dimensions are given in Figure E-1.
•
Falsework is to be constructed in California.
•
Dead load due to concrete is DLconc = 150 kip = 667.233 kN and dead load due to forms, rebar stringers, and caps is
DLsupp = 40 kip = 177.929 kN.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Design Conditions
References:
California Falsework Manual, Example No. 8
ASCE 7-10 Minimum Design Loads for Buildings and Other Structures
E-1
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E-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Figure E.1—Falsework Tower Elevation
Calculation and Discussion
1.
Determine the basic wind speed per Figure C.1.
Risk category II assumed (Section 2.2.5.1)
Basic wind speed, in miles per
hour (Figure C.1). Note that the
basic wind speed values are for
strength level wind load
application. Apply a factor of
0.6 to obtain service level wind
loads.
2.
V = 110 mph
=
V 49.2 ⋅
m
s
Determine the velocity pressure exposure coefficient, Kz, per Table C.1.
Exposure category B, C, or D
(Section C.3):
Exposure category C assumed
Velocity pressure exposure
coefficient, Kh, at top of the
bridge superstructure:
K h = 1.28
Table E.1 shows the velocity pressure exposure coefficient, Kz, at various height zones for wind load application to
the shoring towers.
--`,,,`,,`,`,`,`,`,,`,,,-`-``
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APPENDIX E: SAMPLE WIND AND SEISMIC CALCULATIONS
E-3
Table E.1—Velocity Pressure Exposure Coefficient
Height above
ground level, z
0–15 ft
30 ft
50 ft
Kz
0.85
0.98
1.09
100 ft
105 ft
107 ft
1.27
1.28
1.28
3. Determine wind load parameters.
4.
Wind directionality factor, Kd
(Section C.5):
K d = 0.85
Topographic factor, Kzt
(Section C.4):
K zt = 1.0
Gust-Effect factor
(Section C.6):
G = 0.85
Determine the velocity pressure, qz or qh.
Velocity Pressure, qh, evaluated
at the top of the bridge
superstructure (Section C.2) in
pounds per square foot.
2
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
 V 
0.00256 ⋅ K h ⋅ K zt ⋅ K d 
 ⋅ psf = 33.7 ⋅ psf
 mph 
kN
=
qh 1.614 ⋅
m2
=
qh
Table E.2 shows the velocity pressure, qz, evaluated at various heights for wind pressures applied to the shoring
towers.
Table E.2—Velocity Pressure at Each Height Zone
Height above
Velocity
Ground Level, z
Pressure, qz (psf)
0–15 ft
22
30 ft
50 ft
100 ft
105 ft
26
29
33
34
107 ft
34
5. Determine the force coefficient, Cf, per Section C.7.
The force coefficient for the shoring towers is determined as follows:
Projected solid area of tower
(Section C.8):
Af ⋅s = 2
ft 2
ft
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E-4
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Projected gross area of tower:
Ag ⋅s = 10
Ratio of solid area to gross area:
=
εs
Force coefficient, tower
members are assumed to be
round (Table C.3):
Cf ⋅ s=
ft 2
ft
Af ⋅s
= 0.2
Ag ⋅s
( 4.0 ⋅ ε − 5.9 ⋅ ε + 4.0 ) ⋅ ( 0.51⋅ ε + 0.57= 1.8)
s
2
s
2
s
The force coefficient for the formwork of the bridge superstructure is determined per Table C.5 as follows:
Height of formwork:
s = 2 ft
Height from ground level to top
of formwork:
h = 107 ft
Ratio of formwork height to
height of top of formwork above
ground level:
s
= 0.02
h
Width of formwork assumed
based on spacing of shoring
towers:
B = 40 ft
Ratio of formwork width to
height of formwork:
B
= 20
s
Force coefficient
(Table C.5):
C f ⋅ f = 1.9
Table E.3—Wind Pressure at Each Falsework Height Zone
Height above
Falsework Velocity Pressure,
Falsework Wind Pressure
ground level, z
Type
(psf)
qz (psf)
0–15 ft
Truss Tower
22
22 ⋅ 0.85 ⋅ 1.8 = 34
30 ft
Truss Tower
26
26 ⋅ 0.85 ⋅ 1.8 = 40
50 ft
100 ft
Truss Tower
Truss Tower
29
33
105 ft
Truss Tower
34
105 ft
107 ft
Formwork
Formwork
34
34
29 ⋅ 0.85 ⋅ 1.8 = 44
33 ⋅ 0.85 ⋅ 1.8 = 50
34 ⋅ 0.85 ⋅ 1.8 = 52
34 ⋅ 0.85 ⋅ 1.9 = 55
34 ⋅ 0.85 ⋅ 1.9 = 55
6. Calculate the wind force and the overturning moment.
Determine the wind load applied to the shoring towers:
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Table E.3 shows the wind pressures applied to the falsework after applying the applicable force coefficient.
APPENDIX E: SAMPLE WIND AND SEISMIC CALCULATIONS
E-5
Wind force applied to shoring
towers (Section C.2), lb
F = qz ⋅ G ⋅ Cr ⋅ Ar
Height of bottom zone
h15 = 15 ft
Wind pressure on bottom zone
w15 = 22 psf ⋅ G ⋅ C f ⋅s = 34 ⋅ psf
=
w15 1.612 ⋅
Calculate wind load on tower in
bottom wind zone:
F15 = w15 ⋅ Af ⋅s ⋅ h15 = 4492 N
=
F15 4.492 ⋅ kN
Height of tower to center of
bottom wind zone:
x15 =
h15
− 1 ft = 1.981 m
2
=
x15 1.981 ⋅ m
Overturning moment of tower in
bottom wind zone:
OTM 15 = F15 ⋅ x15 = 6564 ⋅ lbf ⋅ ft
C f ⋅s = 1.8
OTM 15 = 8.899 ⋅ kN ⋅ m
Determine the wind load applied to the conventional falsework:
Projected area of superstructure
(Section C.8):
Af ⋅c = s ⋅ B = 7.432 m 2
=
Af ⋅c 7.432 ⋅ m 2
Wind load applied to
conventional falsework:
F107 = qh ⋅ G ⋅ C f ⋅ f ⋅ Af ⋅c = 19369 N
=
F107 19.369 ⋅ kN
Table E.4—Wind Load per Tower for Each Height Zone
Falsework
Height above
Falsework
Wind
Ground Level, z
Type
Pressure (psf)
Wind Load (lb)
0–15 ft
Truss Tower
34
34 ⋅ 2.0 ⋅ 15 = 1,020
15–30 ft
Truss Tower
37
37 ⋅ 2.0 ⋅ 15 = 1,110
30–50 ft
Truss Tower
42
42 ⋅ 2.0 ⋅ 20 = 1,680
50–100 ft
Truss Tower
47
47 ⋅ 2.0 ⋅ 50 = 4,700
100–105 ft
Truss Tower
51
51 ⋅ 2.0 ⋅ 5 = 510
105–107 ft
Formwork
55
55 ⋅ 2.0 ⋅ 40 ⋅ 0.5(1) = 2,200
Distance to
Centroid of
Overturning Moment
Zone (ft)
(lb ⋅ ft)
6.5
1,020 ⋅ 6.5 = 6,630
21.5
1,110 ⋅ 21.5 = 23,865
39
1,680 ⋅ 39 = 65,520
74
4,700 ⋅ 74 = 347,800
101.5
510 ⋅ 101.5 = 51,765
105
2,200 ⋅ 105 = 231,000
Total Overturning Moment = 726,580
Conversion: 1 ft = 304.8 mm, 1 psf = 47.9 N/m2, 1 lbf = 4.4 N
Note: Half of the load from the supported falsework section goes to each tower.
7.
Calculate equivalent horizontal wind load at top of tower.
Overturning moment:
Height of tower:
=
OTM 726,580 lbf ⋅ ft = 985.11 ⋅ kN ⋅ m
=
htower 104 ft = 31.669 ⋅ m
Equivalent horizontal wind
load:
8.
=
H wind
OTM
= 31077 N
htower
=
H wind 31.077 ⋅ kN
Determine horizontal design dead load for Bent A:
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--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
kN
m2
E-6
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Horizontal load due to dead load is assumed to be 2 percent of the dead load.
Dead load of bridge
concrete:
9.
=
DLconc 150 kip = 667.233 ⋅ kN
Dead load of forms, rebar,
stringers, and caps:
DLsupp =
40 kip ⋅ 177.929 ⋅ kN
Horizontal load due to dead
load:
H DL = 2% ⋅ ( DLconc + DLsupp ) = 1.69 ⋅ 104 m ⋅ kg ⋅ s −2 kN
Determine controlling horizontal design load.
H wind = 31077 N
>
H DL = 1.69 ⋅ 104 m ⋅ kg ⋅ s −2
H=
31.1 ⋅ kN
wind
>
=
H DL 16.903 ⋅ kN
The wind load controls the horizontal design load for the falsework tower.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
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APPENDIX E: SAMPLE WIND AND SEISMIC CALCULATIONS
E-7
EXAMPLE 2—SEISMIC LOAD ON FALSEWORK
Problem Description
Determine the horizontal load to be applied to falsework Bent A shown in Figure E.2. Specifically investigate the following
items:
 Calculate the seismic design parameters.
 Calculate the seismic base shear and overturning moment for Bent A.
 Compare the seismic design load with the minimum horizontal load.
Design Conditions
 Tower dimensions are given in Figure E.2.
 Falsework is to be constructed in Anaheim, California. The Site Class is D.
 The dead load for concrete is 150 kip = 667 kN.
 The dead load for forms, rebar, stringers, and caps is 40 kip = 178 kN.
References
 California Falsework Manual, Example No. 8
 ASCE 7-10 Minimum Design Loads for Buildings and Other Structures
Figure E.2—Falsework Tower Elevation
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
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E-8
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Calculation and Discussion
1.
Determine the spectral response acceleration parameters per Figure E.1.
Mapped maximum considered earthquake (MCE)
spectral response acceleration parameter at short
periods (Figure D.1):
SS = 1.5 g
Mapped maximum considered earthquake (MCE)
spectral response acceleration parameter at 1-s
period (Figure D.1):
S1 = 0.57 g
Earthquake loads must be considered when S1 is greater than or equal to 0.4,
per Section 2.3.5.4.1.
Earthquake loads must be considered in the design
of the falsework.
2.
S1 = 0.57 g > 0.4 g
Determine the site coefficients per Tables E.1 and E.2.
Site Class is D
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
3.
4.
Short-period site coefficient, Fa
(ASCE 7-10 Table 11.4-1):
Fa = 1.0
Long-period site coefficient, Fv
(ASCE 7-10 Table 11.4-2):
Fv = 1.5
Determine the design spectral acceleration parameters per Section D.3.
Design spectral acceleration
parameter at short periods
(ASCE 7-10 Eq. 11.4-3):
SDS = Fa SS = 1.0 g
Design spectral acceleration
parameter at 1-s period
(ASCE 7-10 Eq. 11.4-3):
SD1 = FVS1 = 0.57 g
3
2
3
Estimate the fundamental period of the falsework per Section D.4.
Height of top of falsework
measured from ground in feet
Estimated period of falsework
in seconds
5.
2
hn = 58.0 ft
ℎ
ft
Determine the seismic response coefficient per Section D.5.
Response modification factor
(Section 2.3.5.4.2):
0.75
Ta = 0.02 � 𝑛𝑛 �
sec = 0.42 s
R = 2.5
Risk Category II assumed (Section 2.3.5.4)
Importance Factor
(ASCE 7-10 Table 1.5-2)
Ie = 1.0
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APPENDIX E: SAMPLE WIND AND SEISMIC CALCULATIONS
6.
7.
E-9
Seismic response coefficient for
structures
Cs =
The value of seismic response
coefficient shall not exceed the
following:
Csmax = 𝑇𝑇𝑎𝑎
𝑆𝑆𝐷𝐷𝐷𝐷
𝑅𝑅
𝐼𝐼𝑒𝑒
∙
1
g
𝑆𝑆𝐷𝐷1
sec
∙�
= 0.4
𝑅𝑅
�
𝐼𝐼
𝑒𝑒
∙
1
g
= 0.54
Determine the seismic base shear per Section D.6 and overturning moment for Bent A.
Dead load of bridge concrete:
DLconc = 150 kip = 667.2 kN
Dead load of forms, rebar,
stringers, and caps:
DLsupp = 40 kip = 177.9 kN
Total weight of bridge:
W = DLconc + DLsupp = 190 kip
W = 845.2 kN
Seismic base shear:
V = CsW = 76 kip
V = 338.1 kN
The equivalent lateral force is
equal to the seismic base shear
and is applied at the top of the
falsework.
Feq = V = 76 kip
Feq = 338.1 kN
Height above ground to top of
falsework:
hn = 58.0 ft
Overturning moment on bent A
(half of load from supported
falsework section goes to each
tower):
Mseis = Feq hn = 2204 kip/ft
1
2
Mseis = 2988 kN/m
Determine minimum horizontal design load for Bent A.
Minimum horizontal load is assumed to be 2 percent of dead load (Section 2.3.4.4).
Minimum horizontal load:
8.
HDL = 0.02 W = 3.8 kip
HDL = 16.9 kip
Compare seismic design load to minimum horizontal load.
Feq = 76 kip > HDL = 3.8 kip
Feq = 338.1 kN > HDL = 16.9 kN
The seismic design load exceeds the minimum horizontal design load for the falsework
tower.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
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APPENDIX F
FOUNDATION INVESTIGATION AND DESIGN
F.1—Subsurface Investigation
Because all of the falsework structural loads are ultimately transferred to the soil or rock underlying the falsework
foundation, a subsurface investigation may be necessary to determine the load-supporting ability of the various strata
of soil or rock. Before designing the falsework foundation, it is necessary to determine the type, depth, and properties
of the various soil or rock formations. If a foundation investigation has already been completed for the permanent
structure, this information can be used for the design of the falsework foundation.
A. The best subsurface information is generally obtained from soil borings completed throughout the area of the
falsework foundation. The borings should be extended to a depth where the induced foundation pressures from
the new loading will be less than 10 percent of the overburden pressure, but not less than 15 ft. Soil samples
should be obtained at intervals not exceeding 21/2 ft. The sampling should be performed by conventional methods,
resulting in test samples that are indicative of the strength and compressibility of the soil deposits. This should
include standard penetration resistance testing (AASHTO T 206), briefly described in Section F.3. In situ tests
provide sufficient information for foundation design even though test samples are not obtained. These tests
include cone penetrometer testing (ASTM D3441), pressuremeter testing (ASTM D4719), and dilatometer
testing. Samples obtained by Shelby tubes (AASHTO T 207) in cohesive soils are also acceptable when
accompanied by appropriate laboratory tests, including the unconfined compressive strength test (AASHTO T
208) and water content testing (AASHTO T 265). Disturbed samples from auger cuttings are not considered
acceptable.
B. Test pits can be dug throughout the area to investigate the various soil or rock formations. Test pits should be
used to supplement the soil-boring investigation wherever erratic or discontinuous subsurface conditions are
present. It is easier to determine the thickness and character of these deposits from a large excavation than from
examination of small diameter samples. The person logging the test pits should not only be capable of identifying
the various strata, but should have some means for determining the relative density of each deposit. The hand
penetrometer is sufficient for determining the shear strength of cohesive soils. Section F.4 provides guidelines for
estimating the unconfined compressive strength of cohesive soils based on field observations. The determination
of the relative density of granular soils is more difficult and may be subjective on the part of the observer.
However, techniques such as the dynamic cone penetrometer can be used for this purpose. Alternatively, field
density tests can be performed within the granular formations (AASHTO T 191).
C. Field tests may be undertaken and used as a guide where either the borings or test pits indicate questionable
surface support conditions. This should include proof-testing of the ground surface with a fully loaded dump truck
that has a minimum weight of 20 tons. As the dump truck traverses the area, the amount of ground deflection
under loading should be observed. Deflections of 2 in. or less under wheel load traffic are indicative of reasonably
good support conditions. Large deflections and severe rutting are indicative of very poor support conditions. Plate
load tests can be performed within the potential bearing strata for the foundations. The plate load test consists of
a 12 in. minimum diameter plate with a jack used to provide a force and a truck or other heavy object used as a
reaction. Deflections should be measured with either survey instruments or dial gauges. As the jack loads are
applied, deflection readings should be taken at the design load and at twice the design load. The plate load test
only measures the subgrade reaction of the soil within a depth of 11/2 times the diameter of the plate. Other deeper
strata could also affect future performance of the foundation.
F.2—Relative Density of Granular Deposits
In the United States, the most commonly used method of determining relative density of granular deposits is the
standard penetration test (SPT). It is made by dropping a 140-lb hammer onto the drill rods from a height of 30 in.
The number of blows required to advance a split barrel sampling tube 1 ft is called the standard penetration resistance.
AASHTO T 206 describes the test procedure. Table F.1 relates the SPT to relative density.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
F-1
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F-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Table F.1—Determination of Relative Density Based on Standard Penetration Resistance
Standard Penetration Resistance
Relative Density
0–4
Very loose
4–10
Loose
10–30
Medium
30–50
Dense
Over 50
Very dense
Note: The standard penetration resistance (SPT) values correspond to an effective overburden pressure of 1 tsf. The correction
factor 𝐶𝐶𝑁𝑁 , to be applied to field SPT values for other pressures is given by:
CN = 0.77log10(20⁄𝑝𝑝̅ )
(F-1)
where 𝑝𝑝̅ is the effective vertical overburden pressure in tsf at the elevation of the SPT test. This equation is valid for 𝑝𝑝̅ ≥ 0.25 tsf.
In certain areas of the country, the cone penetration test (CPT) is used for soil exploration. The approximate
relationship between SPT and CPT is shown in Table F.2.
Table F.2—CPT and SPT Values for Various Soils
CPT/SPT
Silts, sandy silts, slightly cohesive silt–sand mixtures
2
Clean fine to medium sands and slightly silty sands
3 to 4
Coarse sands and sands with little gravel
5 to 6
Sandy gravels and gravels
8 to 10
F.3—Consistency of Cohesive Soils
The most important index property used to describe cohesive soils is “consistency,” which is qualitatively
described as “soft,” “medium,” “stiff,” “very stiff,” or “hard.” The consistency of a cohesive soil can also be
determined quantitatively in terms of unconfined compressive strength. Table F.3 relates the qualitative terms for
consistency to the quantitative values of unconfined compressive strength.
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--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Soil Type
APPENDIX F: FOUNDATION INVESTIGATION & DESIGN
F-3
Table F.3—Consistency of Cohesive Soils
Consistency
Field Identification
Unconfined Compressive Strength (tsf)
Very soft
Easily penetrated several inches by fist
Less than 0.25
Soft
Easily penetrated several inches by thumb
0.25 – 0.5
Medium
Can be penetrated several inches by thumb with
moderate effort
0.5 – 1.0
Stiff
Readily indented by thumb but penetrated only with
great effort
1.0 – 2.0
Very stiff
Readily indented by thumbnail
2.0 – 4.0
Hard
Indented with difficulty by thumbnail
Over 4.0
Note:
a. ASTM D2488 has a slightly different criteria for describing consistency.
F.4—Unified Soil Classification System
The soil classification system most widely used by foundation engineers in the United States is known as the
Unified Soil Classification System and has been adopted by the American Society for Testing and Materials as
Standard Test Method for Classification of Soils for Engineering Purposes, ASTM D2487. The main points of ASTM
D2487 are summarized in Table F.4.
According to the Unified System, soils are categorized by particle-size and plasticity characteristics. Because this
system is based on properties of the grains and of the remolded material, it does not fully describe the engineering
properties of the intact material as encountered in the field. However, it permits reliable classification without
extensive testing, and provides useful information about soils that have been properly classified by this method.
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
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F-4
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
Table F.4—Soil Classification According to the Unified Soil Classification System (ASTM D2487)
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
F.5—Potential Problem Soils
Certain soil deposits may experience movements that are not related to loading. These movements are due to the
geologic composition of the deposits or climatic effects. The foundation designer should be cognizant of local problem
soils and incorporate measures to reduce soil deformations.
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APPENDIX F: FOUNDATION INVESTIGATION & DESIGN
F-5
In portions of the western and southern United States, collapsible soil deposits are sometimes encountered. These
are generally fine sands and silts that are deposited in a very loose condition. A low amount of cementation holds the
soil particles in the loose condition until they become wetted. Following wetting, the soils collapse into a denser state,
thereby leading to significant settlements.
Throughout many parts of the United States, active soil deposits are present that can either significantly swell
upon wetting or shrink upon drying. Shallow foundations supported upon these deposits should either be located below
the limit of the moisture content variations, or the area around the foundation should be protected from an increase or
decrease in moisture content.
In the northern portions of the United States where cold weather prevails, freezing of the bearing strata can occur
and cause movements of falsework foundations. Sandy and silty soils are more susceptible to frost than other deposits,
so foundations bearing upon these materials in cold weather shall be protected against frost penetrating into the ground.
Protection can be afforded by a cover of fill or insulation such as styrofoam.
Fill deposits can vary widely in foundation support. If the fill was properly compacted in place, the support can
be excellent, similar to a stiff clay or medium dense sand. On the other hand, loosely dumped fill without compaction
can be very compressible, similar to deposits consisting of a soft clay or loose sand. If not properly controlled, the fill
can also be variable, with some weak pockets contained within a generally firm soil mass. This is especially true for
cohesive soil deposits, where the water content at the time of placement is crucial to the degree of compaction that is
achieved. For cohesive fill deposits, a thorough exploration program is necessary not only to determine the properties
of the cohesive deposits, but also the uniformity of the entire fill mass.
F.6—Extended Foundation
For all deposits consisting of peat, organic silts, or very soft clays, and for some deposits with potential problem
soils, such as collapsible or frost-susceptible soils, extended foundations will be necessary to carry the loads through
the weak or problem deposits to more suitable foundation-bearing material. These extended foundations shall consist
of very deep footings, drilled piers, or piles. Site improvement of organic soils and very soft clays by compaction or
other means is not considered practical.
Where deep foundations will be used, the subsurface exploration shall extend to a depth of at least 10 ft below
the planned base of the foundation (unless rock is encountered at shallower depth) so that side friction and end-bearing
capacity of the extended foundations can be calculated. The deep foundation design shall consider lateral as well as
vertical loads.
If piles are to be used, the driving criteria shall be selected on the basis of a wave equation analysis or an accepted
driving formula. The penetration data of the last 5 ft of driving shall be recorded and submitted to the designer of the
falsework foundations. Guidelines for the design of pile foundations are presented in Chapter 10 of the AASHTO
LRFD Bridge Design Specifications.
If drilled piers are used, the base of each of the drilled piers shall be monitored to see that the proper bearing
stratum has been reached and that the base of the drilled piers excavation is clean and free of sloughing and water
prior to being filled with concrete. The strength of the bearing stratum shall be tested by the monitoring person and
the results submitted to the designer of the falsework foundations. Guidelines for the design of drilled piers are
presented in the American Concrete Institute publication Suggested Design and Construction Procedures for Pier
Foundations, ACI 336.3R.
F.7—AASHTO and ASTM Reference Standards
•
•
•
•
•
•
•
Standard Method of Test for Density of Soil In-Place by the Sand-Cone Method (AASHTO T 191)
Standard Method for Penetration Test and Split-Barrel Sampling of Soils (AASHTO T 206)
Standard Method for Thin-Walled Tub Sampling of Soils (AASHTO T 207)
Standard Method of Test for Unconfined Compressive Strength of Cohesive Soil (AASHTO T 208)
Standard Method of Test for Laboratory Determination of Moisture Content of Soils (AASHTO T 265)
Method of Deep, Quasi-Static, Cone and Friction-Cone Penetration of Soil (ASTM D3441)
Test Method for Pressuremeter Testing in Soils (ASTM D4719)
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
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APPENDIX G
CONVERSION OF EQUATIONS FROM U.S. CUSTOMARY UNITS TO SI UNITS
SI
U.S. CUSTOMARY
Section 2.3.5.5
Section 2.3.5.5
𝑃𝑃𝑤𝑤 = Kv² (psf)
where:
v =
K =
(2.3.5.5-1)
where:
v =
K =
water velocity (ft/s)
constant—see Section 2.3.5.5
water velocity (m/s)
constant—see Section 2.3.5.5
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Section 3.2.2.1
Section 3.2.2.1
Cc = wh (psf)
where:
w =
h =
𝑃𝑃𝑤𝑤 = 515 Kv² (N/m2)
(3.2.2.1-1)
unit weight of fresh concrete (pcf)
depth of fluid—see Section 3.2.2.1 for rest of
definition (ft)
Cc = wh (kN/m2)
where:
w =
h =
unit weight of fresh concrete (kN/m2)
depth of fluid—see Section 3.2.2.1 for rest of
definition (m)
Section 3.2.2.2
Section 3.2.2.2
For columns:
For columns:
Cc = FcFw [150 + 9,000 R/T] (psf)
(3.2.2.2-2)
Cc = FcFw �7.2 +
785𝑅𝑅
𝑇𝑇+17.8
� (kN/m2)
with a minimum of 600Fw (psf), but in no case greater
than wh.
with a minimum of 30Fw (kN/m2) but in no case greater
than ρgh.
For walls with a rate of placement less than 7 ft/h and a
placement height not exceeding 14 ft:
For walls with a rate of placement less than 2.1 m/h and
a placement height not exceeding 4.2 m:
Cc = FcFw [150 + 9,000 R/T] (psf)
Cc = FcFw �7.2 +
(3.2.2.2-3)
with minimum of 600Fw (psf), but in no case greater
than wh.
For walls with a rate of placement of less than 7 ft/h
where placement height exceeds 14 ft and for all walls
with a placement rate of 7 to 15 ft/h:
Cc = FcFw [150 + 43,400/T + 2,800R/T]
(3.2.2.2-4)
785𝑅𝑅
𝑇𝑇+17.8
� (kN/m2)
with a minimum of 30Fw (kN/m2) but in no case greater
than ρgh..
For walls with a rate of placement of less than 2.1 m/h
where placement height exceeds 4.2 m and for all walls
with a placement rate of 2.1 to 4.5 m/h:
Cc = FcFw �7.2 +
1156
𝑇𝑇+17.8
+
244𝑅𝑅
𝑇𝑇+17.8
� (kN/m2)
with a minimum of 600Fw (psf), but in no case greater
than wh.
with a minimum of 30Fw (kN/m2) but in no case greater
than ρgh.
where:
Fc
=
Fw
=
R
=
T
=
where:
chemistry factor per Table 3.2.2.2-1
unit weight factor per Table 3.2.2.2-2
rate of placement (ft/h)
temperature of concrete in the form (°F)
Fc
Fw
R
T
=
=
=
=
chemistry factor per Table 3.2.2.2-1
unit weight factor per Table 3.2.2.2-2
rate of placement (m/h)
temperature of concrete in the form (°C)
G-1
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G-2
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
SI
U.S. CUSTOMARY
Section 4.3.1.2
Section 4.3.1.2
Active Earth Pressure—Cohesionless Soils:
Active Earth Pressure—Cohesionless Soils:
pₐ = kₐγs H (psf)
pₐ = kₐγs H (kN/m2)
where:
γs =
H =
kₐ =
(4.3.1.2-1)
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
unit weight of soil (pcf)
depth below ground level (ft)
active earth pressure coefficient—see
Section 4.3.1.2
where:
=
γ𝑠𝑠
H
=
c
=
Qᵤ
=
(4.3.1.2-2)
total unit weight of soil (pcf)
depth below ground level (ft)
cohesion = Qᵤ/2 (psf)
undrained unconfined compressive strength
in (psf)
γs
H
c
Qu
=
=
=
=
unit weight of soil (kN/m2)
depth below ground level (m)
active earth pressure coefficient—see
Section 4.3.1.2
pₐ = γs H – 2c (kN/m2)
where:
=
γ𝑠𝑠
H
=
c
=
Qᵤ
=
total unit weight of soil (kN/m2)
depth below ground level (m)
cohesion = Qᵤ/2 (kN/m2)
undrained unconfined compressive strength
in (kN/m2)
Active Earth Pressure Mixed Soils:
Active Earth Pressure Mixed Soils:
pₐ = kₐγsH – 2c�𝑘𝑘ₐ (psf)
=
=
=
Active Earth Pressure—Cohesive Soils:
Active Earth Pressure—Cohesive Soils:
pₐ = γs H – 2c (psf)
where:
γ𝑠𝑠
H
kₐ
(4.3.1.2-3)
total unit weight of soil (pcf)
depth below ground level (ft)
cohesion = Qu/2 (psf)
undrained unconfined compressive strength
(psf)
pₐ = kₐγsH – 2c�𝑘𝑘ₐ
γs
H
c
Qu
=
=
=
=
total unit weight of soil (kN/m2)
depth below ground level (m)
cohesion = Qu/2 (kN/m2)
undrained unconfined compressive strength
(kN/m2)
Section 4.3.1.3
Section 4.3.1.3
At-Rest Pressure:
At-Rest Pressure:
pₒ = kₒ γs H (psf)
γs
H
k0
=
=
=
(4.3.1.3-1)
unit weight of soil (pcf)
depth below ground level (ft)
at-rest earth pressure coefficient—see
Section 4.3.1.3
pₒ = kₒ γs H (kN/m2)
γs
H
k0
=
=
=
unit weight of soil (kN/m2)
depth below ground level (m)
at-rest earth pressure coefficient—see
Section 4.3.1.3
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[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
APPENDIX G: UNIT CONVERSIONS
G-3
SI
U.S. CUSTOMARY
Section 4.3.1.4
Section 4.3.1.4
𝑝𝑝𝑝𝑝 = 𝑘𝑘𝑝𝑝 γsH (psf)
(4.3.1.4-1)
γs
=
unit weight of soil (pcf)
H
=
kp
γs
=
unit weight of soil (kN/m2)
depth below ground level (ft)
H
=
depth below ground level (m)
=
passive earth pressure coefficient
kp
=
passive earth pressure coefficient
=
(1 + sinϕ𝑓𝑓 )/(1 - sinϕ𝑓𝑓 ) for zero angle of wall
friction. For values of Kp including the effect
of wall friction, refer to charts in standard
textbooks or NAVFAC DM-7.
=
(1 + sinϕ𝑓𝑓 )/(1 - sinϕ𝑓𝑓 ) for zero angle of wall
friction. For values of Kp including the effect
of wall friction, refer to charts in standard
textbooks or NAVFAC DM-7.
𝑝𝑝𝑝𝑝 = γs H + 2c
(4.3.1.4-2)
γs
=
unit weight of soil (pcf)
H
=
c
Qᵤ
𝑝𝑝𝑝𝑝 = γs H + 2c
γs
=
unit weight of soil (kN/m2)
depth below ground level (ft)
H
=
depth below ground level (m)
=
Qu/2 (psf)
c
=
Qu/2 (kN/m2)
=
undrained unconfined compressive strength
in (psf)
Qᵤ
=
undrained unconfined compressive strength
in (kN/m2)
𝑝𝑝𝑝𝑝 = 𝑘𝑘𝑝𝑝 γsH + 2c�𝑘𝑘𝑝𝑝
(4.3.1.2-3)
γs
=
unit weight of soil (pcf)
H
=
c
kp
Qᵤ
𝑝𝑝𝑝𝑝 = 𝑘𝑘𝑝𝑝 γsH
𝑝𝑝𝑝𝑝 = 𝑘𝑘𝑝𝑝 γsH + 2c�𝑘𝑘𝑝𝑝
γs
=
unit weight of soil (kN/m2)
depth below ground level (ft)
H
=
depth below ground level (m)
=
Qu/2 (psf)
c
=
Qu/2 (kN/m2)
=
passive earth pressure coefficient
kp
=
passive earth pressure coefficient
=
(1 + sinϕ𝑓𝑓 )/(1 - sinϕ𝑓𝑓 ) for zero angle of wall
friction. For values of 𝑘𝑘𝑝𝑝 including the effect
of wall friction, refer to charts in standard
textbooks or NAVFAC DM-7.
=
(1 + sinϕ𝑓𝑓 )/(1 - sinϕ𝑓𝑓 ) for zero angle of wall
friction. For values of 𝑘𝑘𝑝𝑝 including the effect
of wall friction, refer to charts in standard
textbooks or NAVFAC DM-7.
=
undrained unconfined compressive strength
in (psf)
=
undrained unconfined compressive strength
in (kN/m2)
Qᵤ
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
G-4
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
SI
U.S. CUSTOMARY
Section 4.5.2
Section 4.5.2
𝑃𝑃𝑤𝑤 = Kv² (psf)
where:
v =
K =
(4.5.2-1)
where:
v =
K =
water velocity (ft/s)
constant
Section B.1
𝑡𝑡𝑓𝑓
=
(B-1)
specified minimum yield stress of the
flange (ksi)
thickness of the loaded flange (in.)
=
Section B.2
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
tw
k
=
=
lb
=
(B-2)
specified minimum yield stress of the web
(ksi)
web thickness (in.)
distance from outer face of the flange to
the web toe of the fillet (in.)
length of bearing (not less than k for end
beam reactions) (in.)
𝑅𝑅𝑛𝑛 = 𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑤𝑤 (2.5k + lb)
where:
Fyw =
tw
k
=
=
lb
=
(B-3)
specified minimum yield stress of the web
(ksi)
web thickness (in.)
distance from outer face of the flange to
the web toe of the fillet (in.)
length of bearing (not less than k for end
beam reactions) (in.)
Section B.3
𝐹𝐹𝑦𝑦𝑦𝑦
𝑡𝑡𝑓𝑓
=
specified minimum yield stress of the
flange (MPa)
thickness of the loaded flange (mm)
=
𝑅𝑅𝑛𝑛 = 𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑤𝑤 (5k + lb)
where:
Fyw =
tw
k
=
=
lb
=
specified minimum yield stress of the web
(MPa)
web thickness (mm)
distance from outer face of the flange to
the web toe of the fillet (mm)
length of bearing (not less than k for end
beam reactions) (mm)
𝑅𝑅𝑛𝑛 = 𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑤𝑤 (2.5k + lb)
where:
Fyw =
tw
k
=
=
lb
=
specified minimum yield stress of the web
(MPa)
web thickness (mm)
distance from outer face of the flange to
the web toe of the fillet (mm)
length of bearing (not less than k for end
beam reactions) (mm)
Section B.3
𝑙𝑙
𝑡𝑡
1.5
Rn = 0.80 𝑡𝑡𝑤𝑤2 �1 + 3 � 𝑏𝑏 � � 𝑤𝑤� � �
𝑑𝑑
where:
𝑑𝑑 =
𝑅𝑅𝑛𝑛 = 6.25𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓 2
Section B.2
𝑅𝑅𝑛𝑛 = 𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑤𝑤 (5k + lb)
where:
Fyw =
water velocity (m/s)
constant
Section B.1
𝑅𝑅𝑛𝑛 = 6.25𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓 2
𝐹𝐹𝑦𝑦𝑦𝑦
𝑃𝑃𝑤𝑤 = 515 Kv² (N/m2)
𝑡𝑡𝑓𝑓
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
𝑡𝑡𝑤𝑤
(B-4)
full nominal depth of the section (in.)
𝑙𝑙
𝑡𝑡
1.5
Rn = 0.80 𝑡𝑡𝑤𝑤2 �1 + 3 � 𝑏𝑏 � � 𝑤𝑤� � �
𝑑𝑑
where:
𝑑𝑑 =
𝑡𝑡𝑓𝑓
𝑡𝑡𝑤𝑤
full nominal depth of the section (mm)
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
APPENDIX G: UNIT CONVERSIONS
G-5
SI
U.S. CUSTOMARY
𝑙𝑙
𝑡𝑡
1.5
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
Rn = 0.40𝑡𝑡𝑤𝑤2 �1 + 3 � 𝑏𝑏 � � 𝑤𝑤� � �
𝑑𝑑
where:
𝑑𝑑 =
𝑡𝑡𝑓𝑓
full nominal depth of the section (in.)
4𝑙𝑙𝑏𝑏
Rn = 0.40 𝑡𝑡𝑤𝑤2 �1 + �
𝑑𝑑
where:
𝑑𝑑 =
(B-5a)
𝑡𝑡𝑤𝑤
𝑡𝑡𝑤𝑤
1.5
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
− 0.2� � � � �
𝑡𝑡𝑓𝑓
𝑡𝑡𝑤𝑤
(B-5b)
full nominal depth of the section (in.)
Section B.4
𝑅𝑅𝑛𝑛 =
3 𝑡𝑡
𝐶𝐶𝑟𝑟 𝑡𝑡𝑤𝑤
𝑓𝑓
ℎ2
where:
bf =
Cr =
=
h
=
lb
=
𝑙𝑙
𝑡𝑡
1.5
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
Rn = 0.40𝑡𝑡𝑤𝑤2 �1 + 3 � 𝑏𝑏 � � 𝑤𝑤� � �
𝑑𝑑
where:
𝑑𝑑 =
𝑡𝑡𝑓𝑓
𝑡𝑡𝑤𝑤
full nominal depth of the section (mm)
4𝑙𝑙
𝑡𝑡
1.5
𝐸𝐸𝐹𝐹𝑦𝑦𝑦𝑦 𝑡𝑡𝑓𝑓
Rn = 0.40 𝑡𝑡𝑤𝑤2 �1 + � 𝑏𝑏 − 0.2� � 𝑤𝑤� � �
𝑑𝑑
where:
𝑑𝑑 =
𝑡𝑡𝑓𝑓
𝑡𝑡𝑤𝑤
full nominal depth of the section (mm)
Section B.4
�1 + 0.4 �
ℎ/ 𝑡𝑡𝑤𝑤
𝑙𝑙𝑏𝑏 /𝑏𝑏𝑓𝑓
3
� �
(B-6)
width of the flange (in.)
960,000 ksi when 𝑀𝑀𝑢𝑢 < 𝑀𝑀𝑦𝑦 (LRFD) or
1.5 𝑀𝑀𝑎𝑎 < 𝑀𝑀𝑦𝑦 (ASD) at the location of the
force
480,000 ksi when 𝑀𝑀𝑢𝑢 ≥ 𝑀𝑀𝑦𝑦 (LRFD) or
1.5 𝑀𝑀𝑎𝑎 ≥ 𝑀𝑀𝑦𝑦 (ASD) at the location of the
force
clear distance between flanges less the
fillet or corner radius for rolled shapes;
distance between adjacent lines of
fasteners or the clear distance between
flanges when welds are used for built-up
shapes (in.)
largest laterally unbraced length along
either flange at the point of load (in.)
𝑅𝑅𝑛𝑛 =
3 𝑡𝑡
𝐶𝐶𝑟𝑟 𝑡𝑡𝑤𝑤
𝑓𝑓
ℎ2
where:
bf =
Cr =
=
h
=
lb
=
�1 + 0.4 �
ℎ/ 𝑡𝑡𝑤𝑤
𝑙𝑙𝑏𝑏 /𝑏𝑏𝑓𝑓
3
� �
width of the flange (mm)
6.62 x 106 MPa when 𝑀𝑀𝑢𝑢 < 𝑀𝑀𝑦𝑦 (LRFD) or
1.5 𝑀𝑀𝑎𝑎 < 𝑀𝑀𝑦𝑦 (ASD) at the location of the
force
3.31 x 106 MPa when 𝑀𝑀𝑢𝑢 ≥ 𝑀𝑀𝑦𝑦 (LRFD) or
1.5 𝑀𝑀𝑎𝑎 ≥ 𝑀𝑀𝑦𝑦 (ASD) at the location of the
force
clear distance between flanges less the
fillet or corner radius for rolled shapes;
distance between adjacent lines of
fasteners or the clear distance between
flanges when welds are used for built-up
shapes (mm)
largest laterally unbraced length along
either flange at the point of load (mm)
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
AASHTO GUIDE DESIGN SPECIFICATIONS FOR BRIDGE TEMPORARY WORKS
SI
U.S. CUSTOMARY
𝑅𝑅𝑛𝑛 =
3 𝑡𝑡
𝐶𝐶𝑟𝑟 𝑡𝑡𝑤𝑤
𝑓𝑓
ℎ2
where:
bf =
Cr =
=
h
=
lb
=
�0.4 �
ℎ/ 𝑡𝑡𝑤𝑤
𝑙𝑙𝑏𝑏 /𝑏𝑏𝑓𝑓
3
(B-7)
� �
width of the flange (in.)
960,000 ksi when 𝑀𝑀𝑢𝑢 < 𝑀𝑀𝑦𝑦 (LRFD) or 1.5
𝑀𝑀𝑎𝑎 < 𝑀𝑀𝑦𝑦 (ASD) at the location of the
force
480,000 ksi when 𝑀𝑀𝑢𝑢 ≥ 𝑀𝑀𝑦𝑦 (LRFD) or 1.5
𝑀𝑀𝑎𝑎 ≥ 𝑀𝑀𝑦𝑦 (ASD) at the location of the
force
clear distance between flanges less the
fillet or corner radius for rolled shapes;
distance between adjacent lines of
fasteners or the clear distance between
flanges when welds are used for built-up
shapes (in.)
largest laterally unbraced length along
either flange at the point of load (in.)
Section B.5
𝑅𝑅𝑛𝑛 =
3 𝑡𝑡
𝐶𝐶𝑟𝑟 𝑡𝑡𝑤𝑤
𝑓𝑓
ℎ2
where:
bf =
Cr =
=
h
=
lb
=
�0.4 �
ℎ/ 𝑡𝑡𝑤𝑤
𝑙𝑙𝑏𝑏 /𝑏𝑏𝑓𝑓
3
� �
width of the flange (mm)
6.62 x 106 MPa when 𝑀𝑀𝑢𝑢 < 𝑀𝑀𝑦𝑦 (LRFD) or
1.5 𝑀𝑀𝑎𝑎 < 𝑀𝑀𝑦𝑦 (ASD) at the location of the
force
3.31 x 106 MPa when 𝑀𝑀𝑢𝑢 ≥ 𝑀𝑀𝑦𝑦 (LRFD) or
1.5 𝑀𝑀𝑎𝑎 ≥ 𝑀𝑀𝑦𝑦 (ASD) at the location of the
force
clear distance between flanges less the
fillet or corner radius for rolled shapes;
distance between adjacent lines of
fasteners or the clear distance between
flanges when welds are used for built-up
shapes (mm)
largest laterally unbraced length along
either flange at the point of load (mm)
Section B.5
3 𝐸𝐸𝐸𝐸
24𝑡𝑡𝑤𝑤
� 𝑦𝑦𝑦𝑦
(B-8)
ℎ
𝑅𝑅𝑛𝑛 =
3 𝐸𝐸𝐸𝐸
24𝑡𝑡𝑤𝑤
� 𝑦𝑦𝑦𝑦
ℎ
Section B.6
Section B.6
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
𝑃𝑃
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1.4 − 𝑟𝑟�
𝑃𝑃𝑐𝑐
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1 +
𝑅𝑅𝑛𝑛 =
2
3𝑏𝑏𝑐𝑐𝑐𝑐 𝑡𝑡𝑐𝑐𝑐𝑐
𝑑𝑑𝑏𝑏 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
�
(B-9)
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
(B-10)
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1.4 − 𝑟𝑟�
(B-11)
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1 +
𝑃𝑃
𝑃𝑃𝑐𝑐
2
3𝑏𝑏𝑐𝑐𝑐𝑐 𝑡𝑡𝑐𝑐𝑐𝑐
𝑑𝑑𝑏𝑏 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
�
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
G-6
APPENDIX G: UNIT CONVERSIONS
G-7
SI
U.S. CUSTOMARY
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1 +
2
3𝑏𝑏𝑐𝑐𝑐𝑐 𝑡𝑡𝑐𝑐𝑐𝑐
𝑑𝑑𝑏𝑏 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
� �1.9 −
1.2𝑃𝑃𝑟𝑟
where, for (B-9) through (B-12):
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Ag
=
bcf
db
dc
Fy
=
=
=
=
Pc
Pc
Pr
=
=
=
Py
=
tcf
=
=
tw
𝑃𝑃𝑐𝑐
�
(B-12)
gross cross-sectional area of member
(in.2)
width of column flange (in.)
beam depth (in.)
column depth (in.)
specified minimum yield stress of column
web (ksi)
𝑃𝑃𝑦𝑦 (kips) (LRFD)
0.60𝑃𝑃𝑦𝑦 (kips) (ASD)
required axial strength using LRFD or
ASD load combinations (kips)
𝐹𝐹𝑦𝑦 𝐴𝐴𝑔𝑔 , axial yield strength of the column
(kips)
thickness of the column flange (in.)
thickness of column web (in.)
(C-1)
=
gust-effect factor
Cf
=
force coefficient
Af
=
projected area normal to wind
qz = 0.00256 Kz Kzt Kd V2 (psf)
=
(C-2)
velocity pressure exposure coefficient
topographic factor
Kd
=
wind directionality factor
V
=
basic wind speed (mph)
Section F.2
� �1.9 −
1.2𝑃𝑃𝑟𝑟
=
bcf
db
dc
Fy
=
=
=
=
Pc
Pc
Pr
=
=
=
Py
=
tcf
=
=
tw
𝑃𝑃𝑐𝑐
�
gross cross-sectional area of member
(mm2)
width of column flange (mm)
beam depth (mm)
column depth (mm)
specified minimum yield stress of column
web (MPa)
𝑃𝑃𝑦𝑦 (N) (LRFD)
0.60𝑃𝑃𝑦𝑦 (N) (ASD)
required axial strength using LRFD or
ASD load combinations (N)
𝐹𝐹𝑦𝑦 𝐴𝐴𝑔𝑔 , axial yield strength of the column
(N)
thickness of the column flange (mm)
thickness of column web (mm)
F = qzGCfAf (N)
velocity pressure (N/m2)
G
=
gust-effect factor
Cf
=
force coefficient
Af
=
projected area normal to wind
qz = 0.613 Kz Kzt Kd V2 (N/m2)
where:
Kz =
velocity pressure exposure coefficient
Kzt
=
topographic factor
Kd
=
wind directionality factor
V
=
basic wind speed (m/s)
Section F.2
CN = 0.77log10(20⁄𝑝𝑝̅ )
where:
𝑝𝑝̅ =
Ag
where:
qz =
velocity pressure (psf)
G
Kzt
𝑑𝑑𝑏𝑏 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤
Section C.2
F = qzGCfAf (lbs)
where:
Kz =
2
3𝑏𝑏𝑐𝑐𝑐𝑐 𝑡𝑡𝑐𝑐𝑐𝑐
where, for (B-9) through (B-12):
Section C.2
where:
qz =
𝑅𝑅𝑛𝑛 = 0.60 𝐹𝐹𝑦𝑦 𝑑𝑑𝑐𝑐 𝑡𝑡𝑤𝑤 �1 +
(F-1)
effective vertical overburden pressure (tsf)
CN = 0.77log10(1920⁄𝑝𝑝̅)
where:
𝑝𝑝̅ =
effective vertical overburden pressure
(kN/m2)
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
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law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
1.
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7b.
7c.
7d.
7e.
7f.
7g.
7h.
7i.
7j.
7k.
7l.
7m.
7n.
7o.
7p.
7q.
7r.
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R-1
© 2017 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
Order Number: 02250056
Sold to:QING YANG [248215100001] - CPCP-WEST@CFBPC.COM,
Not for Resale,2019-08-14 12:03:30 UTC
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
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Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
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All rights reserved. Duplication Not
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Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS
--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
7s.
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--`,,,`,,`,`,`,`,`,,`,,,-`-``,```,,,`---
Order Number: 02250056
© 2017 by the American Association of State
Highway
Transportation
Officials.
Sold to:QING
YANGand
[248215100001]
- CPCP-WEST@CFBPC.COM,
Resale,2019-08-14
12:03:30 UTC
All rights reserved. Duplication Not
is aforviolation
of applicable
law.
Copyright American Association of State Highway and Transportation Officials
Provided by IHS Markit under license with AASHTO
No reproduction or networking permitted without license from IHS