Table Of ContentNATIONAL
COOPERATIVE
HIGHWAY
RESEARCH
NCHRP PROGRAM
REPORT 651
LRFD Design and Construction
of Shallow Foundations
for Highway Bridge Structures
TRANSPORTATION RESEARCH BOARD 2010 EXECUTIVE COMMITTEE*
OFFICERS
CHAIR: Michael R. Morris, Director of Transportation, North Central Texas Council of Governments, Arlington
VICE CHAIR: Neil J. Pedersen, Administrator, Maryland State Highway Administration, Baltimore
EXECUTIVE DIRECTOR: Robert E. Skinner, Jr., Transportation Research Board
MEMBERS
J. Barry Barker, Executive Director, Transit Authority of River City, Louisville, KY
Allen D. Biehler, Secretary, Pennsylvania DOT, Harrisburg
Larry L. Brown, Sr., Executive Director, Mississippi DOT, Jackson
Deborah H. Butler, Executive Vice President, Planning, and CIO, Norfolk Southern Corporation, Norfolk, VA
William A.V. Clark, Professor, Department of Geography, University of California, Los Angeles
Nicholas J. Garber, Henry L. Kinnier Professor, Department of Civil Engineering, and Director, Center for Transportation Studies, University of
Virginia, Charlottesville
Jeffrey W. Hamiel, Executive Director, Metropolitan Airports Commission, Minneapolis, MN
Edward A. (Ned) Helme, President, Center for Clean Air Policy, Washington, DC
Randell H. Iwasaki, Director, California DOT, Sacramento
Adib K. Kanafani, Cahill Professor of Civil Engineering, University of California, Berkeley
Susan Martinovich, Director, Nevada DOT, Carson City
Debra L. Miller, Secretary, Kansas DOT, Topeka
Pete K. Rahn, Director, Missouri DOT, Jefferson City
Sandra Rosenbloom, Professor of Planning, University of Arizona, Tucson
Tracy L. Rosser, Vice President, Corporate Traffic, Wal-Mart Stores, Inc., Mandeville, LA
Steven T. Scalzo, Chief Operating Officer, Marine Resources Group, Seattle, WA
Henry G. (Gerry) Schwartz, Jr., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, MO
Beverly A. Scott, General Manager and Chief Executive Officer, Metropolitan Atlanta Rapid Transit Authority, Atlanta, GA
David Seltzer, Principal, Mercator Advisors LLC, Philadelphia, PA
Daniel Sperling, Professor of Civil Engineering and Environmental Science and Policy; Director, Institute of Transportation Studies; and Interim
Director, Energy Efficiency Center, University of California, Davis
Douglas W. Stotlar, President and CEO, Con-Way, Inc., Ann Arbor, MI
C. Michael Walton, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin
EX OFFICIO MEMBERS
Thad Allen (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, U.S. Department of Homeland Security, Washington, DC
Peter H. Appel, Administrator, Research and Innovative Technology Administration, U.S.DOT
J. Randolph Babbitt, Administrator, Federal Aviation Administration, U.S.DOT
Rebecca M. Brewster, President and COO, American Transportation Research Institute, Smyrna, GA
George Bugliarello, President Emeritus and University Professor, Polytechnic Institute of New York University, Brooklyn; Foreign Secretary,
National Academy of Engineering, Washington, DC
Anne S. Ferro, Administrator, Federal Motor Carrier Safety Administration, U.S.DOT
LeRoy Gishi, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Washington, DC
Edward R. Hamberger, President and CEO, Association of American Railroads, Washington, DC
John C. Horsley, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC
David T. Matsuda, Deputy Administrator, Maritime Administration, U.S.DOT
Victor M. Mendez, Administrator, Federal Highway Administration, U.S.DOT
William W. Millar, President, American Public Transportation Association, Washington, DC
Cynthia L. Quarterman, Administrator, Pipeline and Hazardous Materials Safety Administration, U.S.DOT
Peter M. Rogoff, Administrator, Federal Transit Administration, U.S.DOT
David L. Strickland, Administrator, National Highway Traffic Safety Administration, U.S.DOT
Joseph C. Szabo, Administrator, Federal Railroad Administration, U.S.DOT
Polly Trottenberg, Assistant Secretary for Transportation Policy, U.S.DOT
Robert L. Van Antwerp (Lt. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers, Washington, DC
*Membership as of February 2010.
N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M
NCHRP REPORT 651
LRFD Design and Construction
of Shallow Foundations
for Highway Bridge Structures
Samuel G. Paikowsky
Mary C. Canniff
GEOSCIENCES TESTING AND RESEARCH, INC.
North Chelmsford, MA
UNIVERSITY OF MASSACHUSETTS
Lowell, MA
Kerstin Lesny
Aloys Kisse
INSTITUTE OF SOIL MECHANICS AND FOUNDATION ENGINEERING
DEPARTMENT OF CIVIL ENGINEERING
University of Duisburg-Essen, Germany
Shailendra Amatya
Robert Muganga
GEOTECHNICAL ENGINEERING RESEARCH LABORATORY
UNIVERSITY OF MASSACHUSETTS
Lowell, MA
Subscriber Categories
Highways • Bridges and Other Structures • Geotechnology
Research sponsored by the American Association of State Highway and Transportation Officials
in cooperation with the Federal Highway Administration
T R A NSPORTAT ION RESEARCH BOARD
WASHINGTON, D.C.
2010
www.TRB.org
NATIONAL COOPERATIVE HIGHWAY NCHRP REPORT 651
RESEARCH PROGRAM
Systematic, well-designed research provides the most effective Project 24-31
approach to the solution of many problems facing highway ISSN 0077-5614
administrators and engineers. Often, highway problems are of local ISBN 978-0-309-15467-3
Library of Congress Control Number 2010927174
interest and can best be studied by highway departments individually
or in cooperation with their state universities and others. However, the © 2010 National Academy of Sciences. All rights reserved.
accelerating growth of highway transportation develops increasingly
complex problems of wide interest to highway authorities. These
problems are best studied through a coordinated program of
COPYRIGHT INFORMATION
cooperative research.
Authors herein are responsible for the authenticity of their materials and for obtaining
In recognition of these needs, the highway administrators of the
written permissions from publishers or persons who own the copyright to any previously
American Association of State Highway and Transportation Officials published or copyrighted material used herein.
initiated in 1962 an objective national highway research program Cooperative Research Programs (CRP) grants permission to reproduce material in this
employing modern scientific techniques. This program is supported on publication for classroom and not-for-profit purposes. Permission is given with the
understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA,
a continuing basis by funds from participating member states of the
FMCSA, FTA, or Transit Development Corporation endorsement of a particular product,
Association and it receives the full cooperation and support of the method, or practice. It is expected that those reproducing the material in this document for
Federal Highway Administration, United States Department of educational and not-for-profit uses will give appropriate acknowledgment of the source of
any reprinted or reproduced material. For other uses of the material, request permission
Transportation.
from CRP.
The Transportation Research Board of the National Academies was
requested by the Association to administer the research program
because of the Board’s recognized objectivity and understanding of
NOTICE
modern research practices. The Board is uniquely suited for this
The project that is the subject of this report was a part of the National Cooperative Highway
purpose as it maintains an extensive committee structure from which
Research Program, conducted by the Transportation Research Board with the approval of
authorities on any highway transportation subject may be drawn; it
the Governing Board of the National Research Council.
possesses avenues of communications and cooperation with federal,
The members of the technical panel selected to monitor this project and to review this
state and local governmental agencies, universities, and industry; its report were chosen for their special competencies and with regard for appropriate balance.
relationship to the National Research Council is an insurance of The report was reviewed by the technical panel and accepted for publication according to
procedures established and overseen by the Transportation Research Board and approved
objectivity; it maintains a full-time research correlation staff of
by the Governing Board of the National Research Council.
specialists in highway transportation matters to bring the findings of
The opinions and conclusions expressed or implied in this report are those of the
research directly to those who are in a position to use them.
researchers who performed the research and are not necessarily those of the Transportation
The program is developed on the basis of research needs identified Research Board, the National Research Council, or the program sponsors.
by chief administrators of the highway and transportation departments
The Transportation Research Board of the National Academies, the National Research
and by committees of AASHTO. Each year, specific areas of research Council, and the sponsors of the National Cooperative Highway Research Program do not
endorse products or manufacturers. Trade or manufacturers’ names appear herein solely
needs to be included in the program are proposed to the National
because they are considered essential to the object of the report.
Research Council and the Board by the American Association of State
Highway and Transportation Officials. Research projects to fulfill these
needs are defined by the Board, and qualified research agencies are
selected from those that have submitted proposals. Administration and
surveillance of research contracts are the responsibilities of the National
Research Council and the Transportation Research Board.
The needs for highway research are many, and the National
Cooperative Highway Research Program can make significant
contributions to the solution of highway transportation problems of
mutual concern to many responsible groups. The program, however, is
intended to complement rather than to substitute for or duplicate other
highway research programs.
Published reports of the
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
are available from:
Transportation Research Board
Business Office
500 Fifth Street, NW
Washington, DC 20001
and can be ordered through the Internet at:
http://www.national-academies.org/trb/bookstore
Printed in the United States of America
C O O P E R A T I V E R E S E A R C H P R O G R A M S
CRP STAFF FOR NCHRP REPORT 651
Christopher W. Jenks, Director, Cooperative Research Programs
Crawford F. Jencks, Deputy Director, Cooperative Research Programs
David B. Beal, Senior Program Officer, Retired
Waseem Dekelbab, Senior Program Officer
Danna Powell, Senior Program Assistant
Eileen P. Delaney, Director of Publications
Ellen Chafee, Editor
NCHRP PROJECT 24-31 PANEL
Field of Soils and Geology—Area of Mechanics and Foundations
Donald Dwyer, New York State DOT, Albany, NY (Chair)
Nabil Hourani, HNTB Corporation, Boston, MA
Lyndi D. Blackburn, Alabama DOT, Montgomery, AL
James G. Cuthbertson, Washington State DOT, Olympia, WA
Jie Han, University of Kansas, Lawrence, KS
Richard A. Lamb, Minnesota DOT, Maplewood, MN
Andrzej S. Nowak, University of Nebraska—Lincoln, Lincoln, NE
Martin I. Okorie, South Carolina DOT, Columbia, SC
Hani H. Titi, University of Wisconsin—Milwaukee, Milwaukee, WI
Michael Adams, FHWA Liaison
G. P. Jayaprakash, TRB Liaison
AUTHOR ACKNOWLEDGMENTS
Ms. Yu Fu of the Geotechnical Engineering Research Laboratory at the University of Massachusetts
Lowell developed the original shallow foundations database as part of her master’s research work, with the
help of Mr. Jenia Nemirovsky. This database was greatly enhanced by load test case histories gathered and
conducted at the University of Duisburg-Essen in Germany. All the responders to the questionnaires, in
particular those that participated in the telephone interviews—Mr. Leo Fontaine of the Connecticut
Department of Transportation (DOT), Mr. Nabil Hourani of the Massachusetts Highway Department,
Ms. Beverly Miller of the Pennsylvania DOT, Mr. Jim Cuthbertson of the Washington State DOT, Ms.
Laura Krusinski of the Maine DOT, and Mssrs. Edward Wasserman and Len Oliver and Ms. Vanessa Bate-
man of the Tennessee DOT—are acknowledged for providing DOT insight on the prevailing practices of
bridge shallow foundation design.
F O R E W O R D
By Waseem Dekelbab
Staff Officer
Transportation Research Board
This report develops and calibrates procedures and modifies the AASHTO LRFD Bridge
Design Specifications, Section 10—Foundations for the Strength Limit State Design of Shal-
low Foundations. The material in this report will be of immediate interest to bridge engi-
neers and geotechnical engineers involved in the design of shallow foundations.
Shallow foundations are used for a large percentage of bridges, retaining walls, and other
transportation structures. Reliability-based resistance factors are needed to incorporate into
design specifications for use by transportation agencies.
LRFD design specifications for shallow foundations of highway structures need to be
developed using a reliability-based calibration procedure, consistent with the calibration of
load and resistance factors for bridge superstructures. Load and resistance factors should
account for uncertainties related to load combinations, site conditions, soil and rock type
and properties, and methods of testing and analysis. It is believed that resistance factors for
shallow foundations in Section 10 of the current AASHTO LRFD Bridge Design Specifica-
tions do not satisfy these requirements.
The objective of this project was to develop recommended changes to Section 10 of the
AASHTO LRFD Bridge Design Specifications for the strength limit state design of shallow
foundations.
This research was performed under NCHRP Project 24-31 by Geosciences Testing and
Research, Inc., and the University of Massachusetts at Lowell with the assistance of the Uni-
versity of Duisburg-Essen, Germany. The report fully documents the research leading to the
recommended design specifications for the strength limit state design of shallow founda-
tions.
Appendixes A through H from the research agency’s final report are not published herein
but are available on the TRB website (www.trb.org) by searching on “NCHRP Report 651”.
These appendixes are titled as follows:
• Appendix A: Alternative Model Background
• Appendix B: Findings—State of Practice, Serviceability and Databases
• Appendix C: Questionnaire Summary
• Appendix D: UML-GTR ShalFound07 Database
• Appendix E: UML-GTR RockFound07 Database
• Appendix F: Shallow Foundations Modes of Failure and Failure Criteria
• Appendix G: Bias Calculation Examples
• Appendix H: Design Examples
C O N T E N T S
1 Summary
3 Chapter 1 Background
3 1.1 Research Objectives
3 1.2 Engineering Design Methodologies
4 1.3 Load and Resistance Factor Design
10 1.4 Format for Design Factor Development
15 1.5 Bearing Capacity of Shallow Foundations
24 1.6 An Alternative Approach and Method of Analysis for Limit State
Design of Shallow Foundations
33 1.7 Bearing Capacity of Shallow Foundations on Rock
40 1.8 Rock Classification and Properties
52 Chapter 2 Research Approach
52 2.1 Scope and Structure
52 2.2 Methodology
56 2.3 Execution and Presentation
57 Chapter 3 Findings
57 3.1 Design and Construction State of Practice
61 3.2 Assembled Databases
66 3.3 Determination of the Measured Strength Limit State
for Foundations Under Vertical-Centric Loading
69 3.4 Determination of the Calculated Strength Limit States
for the Case Histories (Foundations on Soils)
73 3.5 Uncertainty in the Bearing Capacity of Footings in/on Granular Soils
Subjected to Vertical-Centric Loading
76 3.6 Uncertainty in the Bearing Capacity of Footings in/on Granular Soils
Subjected to Vertical-Eccentric, Inclined-Centric,
and Inclined-Eccentric Loading
82 3.7 Loading Direction Effect for Inclined-Eccentric Loading
85 3.8 Uncertainty in the Bearing Capacity of Footings in/on Rock
92 3.9 Uncertainties in the Friction Along the Soil-Structure Interface
100 Chapter 4 Interpretations and Appraisal
100 4.1 Overview
100 4.2 Uncertainty in Vertical and Lateral Loading
104 4.3 Calibration Methodology
107 4.4 Examination of the Factor Nγ as a Source of Uncertainty
in Bearing Capacity Analysis
110 4.5 Examination of Footing Size Effect on the Uncertainty
in Bearing Capacity Analysis
110 4.6 In-Depth Re-Examination of the Uncertainty in Bearing Capacity
of Footings in/on Granular Soils Under Vertical-Centric Loading
116 4.7 In-Depth Re-Examination of the Uncertainty in Bearing Capacity
of Footings in/on Granular Soils Under Vertical-Eccentric Loading
121 4.8 In-Depth Re-Examination of the Uncertainty in Bearing Capacity
of Footings in/on Granular Soils Under Inclined-Centric Loading
123 4.9 In-Depth Re-Examination of the Uncertainty in Bearing Capacity
of Footings in/on Granular Soils Under Inclined-Eccentric Loading
124 4.10 Summary of Recommended Resistance Factors for Footings
in/on Granular Soils
124 4.11 Goodman’s (1989) Semi-Empirical Bearing Capacity Method
for Footings in/on Rock
126 4.12 Carter and Kulhawy’s (1988) Semi-Empirical Bearing Capacity
Method for Footings in/on Rock
127 4.13 Summary of Recommended Resistance Factors for Shallow
Foundations in/on Rock
127 4.14 Sliding Friction Resistance
130 Chapter 5 Design Examples
130 5.1 Introduction
130 5.2 Loading Conventions and Notations
130 5.3 Examples Summary
132 References
139 Unpublished Material
1
S U M M A R Y
LRFD Design and Construction of
Shallow Foundations for Highway
Bridge Structures
NCHRP Project 24-31, “LRFD Design Specifications for Shallow Foundations” was initi-
ated with the objective to “develop recommended changes to Section 10 of the AASHTO
LRFD Bridge Design Specifications for the strength limit state design of shallow foundations.”
The AASHTO specifications are traditionally observed on all federally aided projects and are
generally viewed as the national code of U.S. highway practice; hence, they influence the con-
struction of all foundations of highway bridges throughout the United States. This report
represents the results of the studies and analyses conducted for NCHRP Project 24-31.
The current AASHTO specifications, as well as other existing codes employing reliability-
based design (RBD) principles, were calibrated using a combination of reliability theory, fit-
ting to allowable stress design (ASD) (also called working stress design [WSD]), and engi-
neering judgment. The main challenges of the project were, therefore, the compilation of
large, high-quality databases of tested foundations to failure and the development of a pro-
cedural and data management framework that would enable Load and Resistance Factor
Design (LRFD) parameter evaluation for the strength limit state of shallow foundations. The
presented research is the first to introduce large-scale, RBD calibration of shallow founda-
tions utilizing databases.
The state of the art was examined via a critical literature review of design methodologies and
RBD and LRFD principles. The state of the practice was established via a questionnaire, dis-
tributed to and gathered from state and federal transportation officials and supplemented by
telephone interviews. The use of shallow foundations for bridge construction across the United
States was found to be about 17%, and a comparison to previous questionnaires showed that
this percentage had not changed much. The use varies widely, however, in regions and states
across the country: from about two-thirds of all bridge foundations in Pennsylvania, Tennessee,
and Connecticut to six states that do not use shallow foundations at all. About three-quarters
of all shallow foundations were reported to be built on rock or Intermediate Geomaterial
(IGM), and the rest were predominantly built on granular materials. The presented research
focuses on the analysis and RBD calibration of foundations on granular soil and rock only.
Large databases were gathered containing 549 load test cases related to the performance
of shallow foundations in/on granular materials (of which 269 cases were utilized in the cali-
bration), and 122 cases for foundations in/on rock (of which 119 were utilized in the cali-
bration). The database for the performance of shallow foundations on soils includes the test-
ing of models and large foundations under vertical, eccentric, and inclined loading
conditions, as well as combinations of these conditions. The database for the performance
of shallow foundations on rock includes the performance of models and large shallow foun-
dations as well as the tip area of rock sockets for which the load-displacement relations could
have been distinctly obtained. Failure criteria were identified and examined for establishing
the ultimate limit state of the tested foundations. The application of methods to the cases
provided the measured resistance of each load test case.
