TRANSPORTATION RESEARCH BOARD 2024 EXECUTIVE COMMITTEE*

OFFICERS

CHAIR: Carol A. Lewis, Professor, Transportation Studies, Texas Southern University, Houston

VICE CHAIR: Leslie S. Richards, General Manager, Southeastern Pennsylvania Transportation Authority (SEPTA), Philadelphia

EXECUTIVE DIRECTOR: Victoria Sheehan, Transportation Research Board, Washington, DC

MEMBERS

Michael F. Ableson, CEO, Arrival Automotive–North America, Detroit, MI

James F. Albaugh, President and CEO, The Boeing Company (retired), Scottsdale, AZ

Carlos M. Braceras, Executive Director, Utah Department of Transportation, Salt Lake City

Douglas C. Ceva, Vice President, Customer Lead Solutions, Prologis, Inc., Jupiter, FL

Nancy Daubenberger, Commissioner of Transportation, Minnesota Department of Transportation, St. Paul

Marie Therese Dominguez, Commissioner, New York State Department of Transportation, Albany

Garrett Eucalitto, Commissioner, Connecticut Department of Transportation, Newington

Chris T. Hendrickson, Hamerschlag University Professor of Engineering Emeritus, Carnegie Mellon University, Pittsburgh, PA

Randell Iwasaki, President and CEO, Iwasaki Consulting Services, Walnut Creek, CA

Ashby Johnson, Executive Director, Capital Area Metropolitan Planning Organization (CAMPO), Austin, TX

Joel M. Jundt, Secretary of Transportation, South Dakota Department of Transportation, Pierre

Hani S. Mahmassani, W.A. Patterson Distinguished Chair in Transportation; Director, Transportation Center, Northwestern University, Evanston, IL

Scott C. Marler, Director, Iowa Department of Transportation, Ames

Ricardo Martinez, Adjunct Professor of Emergency Medicine, Emory University School of Medicine, Decatur, GA

Michael R. McClellan, Vice President, Strategic Planning, Norfolk Southern Corporation, Norfolk, VA

Russell McMurry, Commissioner, Georgia Department of Transportation, Atlanta

Craig E. Philip, Research Professor and Director, VECTOR, Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN

Steward T.A. Pickett, Distinguished Senior Scientist, Cary Institute of Ecosystem Studies, Millbrook, NY

Susan A. Shaheen, Professor and Co-director, Transportation Sustainability Research Center, University of California, Berkeley

Marc Williams, Executive Director, Texas Department of Transportation, Austin

EX OFFICIO MEMBERS

Michael R. Berube, Deputy Assistant Secretary for Sustainable Transportation, U.S. Department of Energy, Washington, DC

Shailen Bhatt, Administrator, Federal Highway Administration, U.S. Department of Transportation, Washington, DC

Amit Bose, Administrator, Federal Railroad Administration, Washington, DC

Tristan Brown, Deputy Administrator, Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation, Washington, DC

Steven Cliff, Executive Officer, California Air Resources Board, Sacramento

Rand Ghayad, Senior Vice President, Association of American Railroads, Washington, DC

LeRoy Gishi, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Germantown, MD

William H. Graham, Jr. (Major General, U.S. Army), Deputy Commanding General for Civil and Emergency Operations, U.S. Army Corps of Engineers, Washington, DC

Robert C. Hampshire, Deputy Assistant Secretary for Research and Technology, U.S. Department of Transportation, Washington, DC

Sue Lawless, Acting Deputy Administrator, Federal Motor Carrier Safety Administration, Washington, DC

Niloo Parvashtiani, Engineer, Mobility Consultant Solutions, Iteris Inc., Fairfax, VA, and Chair, TRB Young Members Coordinating Council

Sophie Shulman, Acting Administrator, National Highway Traffic Safety Administration, Washington, DC

Karl Simon, Director, Transportation and Climate Division, U.S. Environmental Protection Agency, Washington, DC

Paul P. Skoutelas, President and CEO, American Public Transportation Association, Washington, DC

Polly Trottenberg, Deputy Secretary of Transportation and Acting Administrator, Federal Aviation Administration, U.S. Department of Transportation, Washington, DC

Jim Tymon, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC

Veronica Vanterpool, Acting Administrator, Federal Transit Administration, Washington, DC

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation results in increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research.

Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 initiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agreement No. 693JJ31950003.

The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, universities, and industry; TRB’s relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of specialists in highway transportation matters to bring the findings of research directly to those in a position to use them.

The program is developed on the basis of research needs identified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s recommendations are proposed to the AASHTO Board of Directors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB.

The needs for highway research are many, and NCHRP can make significant contributions to solving 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.

NCHRP RESEARCH REPORT 1112

Project 12-116A
ISSN 2572-3766 (Print)
ISSN 2572-3774 (Online)
ISBN 978-0-309-70990-3
Library of Congress Control Number 2024939356

© 2024 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trademarks of the National Academy of Sciences. All rights reserved.

COPYRIGHT INFORMATION

Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein.

Cooperative Research Programs (CRP) grants permission to reproduce material in this 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, APTA, FAA, FHWA, FTA, GHSA, or NHTSA endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for 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 from CRP.

NOTICE

The research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine.

The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; the FHWA; or the program sponsors.

The Transportation Research Board does not develop, issue, or publish standards or specifications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications.

The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names or logos appear herein solely because they are considered essential to the object of the report.

Published research reports of the

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

are available from

National Academies Press
500 Fifth Street, NW, Keck 360
Washington, DC 20001

(800) 624-6242

and can be ordered through the Internet by going to https://nap.nationalacademies.org

Printed in the United States of America

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, nongovernmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president.

The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president.

The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president.

The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine.

Learn more about the National Academies of Sciences, Engineering, and Medicine at www.nationalacademies.org.

The Transportation Research Board is one of seven major program divisions of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to mobilize expertise, experience, and knowledge to anticipate and solve complex transportation-related challenges. The Board’s varied activities annually engage about 8,500 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.

Learn more about the Transportation Research Board at www.TRB.org.

COOPERATIVE RESEARCH PROGRAMS

CRP STAFF FOR NCHRP RESEARCH REPORT 1112

Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program

Ahmad Abu-Hawash, Senior Program Officer

Sheila A. Moore, Program Associate

Natalie Barnes, Director of Publications

Heather DiAngelis, Associate Director of Publications

NCHRP PROJECT 12-116A PANEL
Field of Design—Area of Bridges

Jon E. Bischoff, Utah Department of Transportation, Salt Lake City, UT (Chair)

Nathalia Rodriguez Chandler, South Carolina Department of Transportation, Columbia, SC

Scott Hidden, North Carolina Department of Transportation, Raleigh, NC

Tim E. Huff, Tennessee Technological University, Cookeville, TN

Nora Kyo, California Department of Transportation, Sacramento, CA

Richard Pratt, Alaska Department of Transportation, (retired), Juneau, AK

Ryan Snook, Michigan Department of Transportation, Lansing, MI

Derrick David Dasenbrock, FHWA Liaison

FOREWORD

By Ahmad Abu-Hawash

Staff Officer

Transportation Research Board

NCHRP Research Report 1112: Design of Piles for Downdrag presents procedures for determining downdrag loads used in the design of bridge piles. The procedures were developed based on an extensive review of the state of practice and a collection of existing field test data. The research findings will be used by geotechnical engineers responsible for designing bridge foundations for state departments of transportation.

The AASHTO LRFD [Load and Resistance Factor Design] Bridge Design Specifications (BDS) recognizes that piles in settling soil experience downdrag forces from negative skin friction and may also move downward with the adjacent soil. Many bridges are constructed in areas where there is compressible soil or liquefiable soil, which necessitates the consideration of downdrag forces and associated settlement. Downdrag for static and seismic conditions has increasingly placed greater demands on existing and new foundations and also led to higher construction costs. Therefore, there was an immediate need to review the fundamental behavior of piles subject to downdrag and propose design requirements for the implementation of the neutral plane method for the evaluation of downdrag and the static and seismic design of piles.

Under NCHRP Project 12-116A, “Proposed AASHTO Specifications for Design of Piles for Downdrag,” the University of Arkansas was asked to (1) propose modifications to the bridge design requirements for the static and seismic design of piles for downdrag and (2) develop design examples to demonstrate the application of the proposed design requirements. The research team proposed draft language for consideration by AASHTO in the next update of the LRFD BDS and provided analysis and design examples to illustrate the proposed updates.

In addition to this report, NCHRP Web-Only Document 398: Pile Design for Downdrag: Examples and Supporting Material is available on the National Academies Press website (nap.nationalacademies.org) by searching for NCHRP Web-Only Document 398.

CONTENTS

Summary

Section 1 Literature Review

1.1 NCHRP Project 12-116, Literature and Synthesis Report

1.2 Additional Investigations

1.3 Literature Review

1.4 Summary

Section 2 Execute Methodology

2.1 Introduction

2.2 Selection of Soil Correlations

2.3 Comparison of Existing Published t-z Relationships

2.4 Collected Database

2.5 Methodology

2.6 Comments on Seismically Induced Downdrag and Drag Load

Section 3 Develop Design Examples for Pile Downdrag

References

Appendices