Load and Resistance Factor Design (LRFD) for Deep Foundations (2004)

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T R A N S P O R T A T I O N R E S E A R C H B O A R D WASHINGTON, D.C. 2004 www.TRB.org NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 507 Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration SUBJECT AREAS Bridges, Other Structures, and Hydraulics and Hydrology • Soils, Geology and Foundations Load and Resistance Factor Design (LRFD) for Deep Foundations SAMUEL G. PAIKOWSKY Geotechnical Engineering Research Laboratory Department of Civil & Environmental Engineering University of Massachusetts Lowell, MA WITH CONTRIBUTIONS BY: BJORN BIRGISSON, MICHAEL MCVAY, THAI NGUYEN University of Florida Gainesville, FL CHING KUO Geostructures, Inc. Tampa, FL GREGORY BAECHER BILAL AYYUB University of Maryland College Park, MD KIRK STENERSEN KEVIN O’MALLEY University of Massachusetts Lowell, MA LES CHERNAUSKAS Geosciences Testing and Research, Inc. N. Chelmsford, MA MICHAEL O’NEILL University of Houston Houston, TX

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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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished schol- ars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and techni- cal matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Acad- emy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achieve- ments of engineers. Dr. William A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Acad- emy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both the Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is a division of the National Research Council, which serves the National Academy of Sciences and the National Academy of Engineering. The Board’s mission is to promote innovation and progress in transportation through research. In an objective and interdisciplinary setting, the Board facilitates the sharing of information on transportation practice and policy by researchers and practitioners; stimulates research and offers research management services that promote technical excellence; provides expert advice on transportation policy and programs; and disseminates research results broadly and encourages their implementation. The Board’s varied activities annually engage more than 5,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. www.TRB.org www.national-academies.org

COOPERATIVE RESEARCH PROGRAMS STAFF FOR NCHRP REPORT 507 ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Manager, NCHRP DAVID B. BEAL, Senior Program Officer EILEEN P. DELANEY, Managing Editor HILARY FREER, Associate Editor NCHRP PROJECT 24-17 PANEL Field of Design—Area of Bridges, Other Structures, and Hydraulics and Hydrology TERRY SHIKE, P.E., David Evans and Associates, Inc., Salem, Oregon (Chair) PAUL F. BAILEY, P.E., New York State DOT RICHARD BARKER, P.E., Blacksburg, Virginia JERRY A. DIMAGGIO, P.E., FHWA WILLIAM S. FULLERTON, P.E., Montana DOT ROBERT E. KIMMERLING, P.E., PanGeo, Inc., Seattle, Washington MARK J. MORVANT, P.E., Louisiana DOTD, Louisiana Transportation Research Center PAUL PASSE, P.E., PSI, Tampa, Florida JEFF SIZEMORE, P.E., South Carolina DOT CARL EALY, FHWA Liaison Representative G. P. JAYAPRAKASH, TRB Liaison Representative AUTHOR ACKNOWLEDGMENTS The presented research was sponsored by the American Associ- ation of State Highway and Transportation Officials (AASHTO), under project 24-17, in cooperation with the Federal Highway Administration (FHWA). The panel of the research project is acknowledged for their comments and suggestions. The interest, support, and suggestions of Mr. David Beal of the NCHRP are highly appreciated. Messrs. Jerry DiMaggio, Al DiMillio, and Carl Ealy of the FHWA are acknowledged for their concern and sup- port. Dr. Gregory Baecher and Dr. Bilal Ayyub from the Univer- sity of Maryland contributed to sections 1.3.1 through 1.3.4, sec- tion 1.4.3.4, sections 2.6.1 through 2.6.3, and section 3.3, and performed the calculations of the presented resistance factors based on FORM. Dr. Mike McVay, Dr. Bjorn Birgisson, and Mr. Thai Nguyen of the University of Florida, and Dr. Ching Kuo of Geostructures compiled the static analyses databases and carried out the analyses related to the material presented in sections 2.1.1, 2.1.2, 2.3.1, 2.5, 3.1.2, and 3.1.4. Dr. Frank Rausche of Goble, Rausche, Likins (GRL) and Associates provided the data pertain- ing to the evaluation of GRLWEAP as the WEAP method for dynamic pile capacity evaluation. Mr. Kirk Stenersen researched the performance of the dynamic analyses as part of his graduate studies at the University of Massachusetts Lowell. The help of Ms. Mary Canniff and Ms. Laural Stokes in the preparation of the man- uscript is appreciated.

This report contains the findings of a study to develop resistance factors for driven pile and drilled shaft foundations. These factors are recommended for inclusion in Sec- tion 10 of the AASHTO LRFD Bridge Design Specifications to reflect current best practice in geotechnical design and construction. The report also provides a detailed procedure for calibrating deep foundation resistance. The material in this report will be of immediate interest to bridge engineers and geotechnical engineers involved in the design of pile and drilled shaft foundations. Full implementation of the AASHTO LRFD Bridge Design Specifications for deep foundations is hampered by provisions that are inconsistent with current geotechnical engineering practice. Static pile-capacity analyses are typically used to estimate required pile lengths and quantities, whereas dynamic analyses are used to determine pile capacity during pile driving. Currently, the resistance factors for static and dynamic analysis are multiplied by each other, resulting in designs that are significantly more conservative than used in past practice, increasing foundation costs. Resistance factors for drilled shafts in sand or gravel are not provided in the LRFD Specifications, and many of the state departments of transportation do not have the data or the resources to do their own calibrations as recommended in the specification. The effect of various construction techniques on drilled shaft resistance factors also is not addressed in the LRFD Specifications. The resistance factors for deep foundations were not calibrated for the LRFD load factors. In addition, the resistance factors do not account for the variability of the site conditions and the number of load tests conducted. Another shortcoming is that many accepted design procedures, some of which are commonly recommended by FHWA, are not supported by the LRFD Specifications. The objective of this research was to address the aforementioned issues and to pro- vide resistance factors for the load and resistance factor design of deep foundations. Under NCHRP Project 24-17, the University of Massachusetts at Lowell with the assis- tance of D’Appolonia, the University of Maryland, the University of Florida, and the University of Houston assembled databases for static analysis of drilled shafts and driven piles and for dynamic analysis of driven piles. These databases were used for the statistical evaluation of resistance factors. Extensive appendices providing detailed information on the development and application of the resistance factors are included on NCHRP CD-39 bound with the report. FOREWORD By David B. Beal Staff Officer Transportation Research Board

1 SUMMARY 3 CHAPTER 1 Introduction and Research Approach 1.1 Background, 3 1.2 Stress Design Methodologies, 3 1.2.1 Working Stress Design, 3 1.2.2 Limit States Design, 3 1.3 Load and Resistance Factor Design (LRFD), 4 1.3.1 Principles, 4 1.3.2 Background Information, 5 1.3.3 LRFD Performance and Advantages, 5 1.3.4 LRFD in Geotechnical Engineering, 6 1.3.5 LRFD for Deep Foundations, 6 1.4 Research Approach, 8 1.4.1 Design and Construction Process of Deep Foundations, 8 1.4.2 Overview of the Research Approach, 8 1.4.3 Principles and Framework of the Calibration, 9 14 CHAPTER 2 Findings 2.1 State of Practice, 14 2.1.1 Questionnaire and Survey, 14 2.1.2 Major Findings, 14 2.2 Databases, 16 2.2.1 General, 16 2.2.2 Drilled Shaft Database—Static Analysis, 16 2.2.3 Driven Pile Database—Static Analysis, 16 2.2.4 Driven Pile Database—Dynamic Analysis, 16 2.3 Deep Foundations Nominal Strength, 16 2.3.1 Overview, 16 2.3.2 Failure Criterion for Statically Loaded Driven Piles, 16 2.3.3 Load Test Procedure for Statically Loaded Driven Piles, 18 2.3.4 Failure Criterion for Statically Loaded Drilled Shaft, 18 2.4 Driven Piles—Static Analysis Methods, 19 2.5 Driven Piles—Dynamic Analysis Methods, 19 2.5.1 Overview, 19 2.5.2 Methods of Analysis, 20 2.5.3 The Controlling Parameters, 22 2.6 Drilled Shafts—Static Analysis Methods, 27 2.7 Level of Target Reliability, 27 2.7.1 Target Reliability and Probability of Failure, 27 2.7.2 Concepts for Establishing Target Reliability, 27 2.7.3 Target Reliability for Structures, 28 2.7.4 Geotechnical Perspective, 29 2.7.5 Recommended Target Reliability, 29 2.8 Investigation of the Resistance Factors, 30 2.8.1 Initial Resistance Factors Calculations, 30 2.8.2 Parameter Study—The Limited Meaning of the Resistance Factor Value, 30 2.8.3 The Design Methods’ Efficiency, 31 33 CHAPTER 3 Interpretation, Appraisal, and Applications 3.1 Analysis Results and Resistance Factors, 33 3.1.1 Driven Piles—Static Analysis, 33 3.1.2 Driven Piles—Dynamic Analysis, 33 3.1.3 Drilled Shafts—Static Analysis, 35 3.2 Initial Examination of Results, 36 3.2.1 Overview, 36 3.2.2 FOSM vs. FORM, 37 3.2.3 Equivalent Factors of Safety, 37 3.2.4 Detailed Tables, 38 3.2.5 Resistance Factors for Pullout of Driven Piles, 39 3.3 Pile Testing, 39 3.3.1 Overview, 39 3.3.2 Resistance Factors for Static Pile Load Tests, 40 CONTENTS

3.3.3 Numbers of Dynamic Tests Performed on Production Piles, 41 3.3.4 Testing Drilled Shafts for Major Defects, 43 3.4. Recommended Resistance Factors, 47 3.4.1 Overview, 47 3.4.2 Static Analysis of Driven Piles, 47 3.4.3 Dynamic Analysis of Driven Piles, 48 3.4.4 Static Analysis for Drilled Shafts, 49 3.4.5 Static Load Test, 49 3.4.6 Pile Test Scheduling, 50 3.4.7 Design Considerations, 50 3.5 Evaluation of the Resistance Factors, 52 3.5.1 Overview, 52 3.5.2 Working Stress Design, 53 3.5.3 Sensitivity Analysis and Factors Evaluation, 55 3.5.4 Actual Probability of Failure, 55 71 CHAPTER 4 Conclusions and Suggested Research 4.1 Conclusions, 71 4.2 Suggested Research—Knowledge-Based Designs, 71 4.2.1 Statement of Problem, 71 4.2.2 Framework for LRFD Design for Deep Foundations, 71 73 BIBLIOGRAPHY A1 APPENDIXES