LRFD Design and Construction of Shallow Foundations for Highway Bridge Structures (2010)

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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2010 www.TRB.org 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 Subscriber Categories Highways • Bridges and Other Structures • Geotechnology 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 Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the 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 cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. 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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. 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

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 F O R E W O R D By Waseem Dekelbab Staff Officer Transportation Research Board

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