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NATIONAL NCHRPREPORT 682 COOPERATIVE HIGHWAY RESEARCH PROGRAM Scour at Wide Piers and Long Skewed Piers

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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 Eugene A. Conti, Jr., Secretary of Transportation, North Carolina DOT, Raleigh 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 Paula J. Hammond, Secretary, Washington State DOT, Olympia Edward A. (Ned) Helme, President, Center for Clean Air Policy, Washington, DC 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 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 Kirk T. Steudle, Director, Michigan DOT, Lansing 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 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 Tara O'Toole, Under Secretary for Science and Technology, U.S. Department of Homeland Security, Washington, DC Robert J. Papp (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, U.S. Department of Homeland Security, 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 October 2010.

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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 682 Scour at Wide Piers and Long Skewed Piers D. Max Sheppard Huseyin Demir OCEAN ENGINEERING ASSOCIATES, INC. Gainesville, FL Bruce Melville CIVIL AND ENVIRONMENTAL ENGINEERING DEPARTMENT UNIVERSITY OF AUCKLAND Auckland, New Zealand Subscriber Categories Bridges and Other Structures Hydraulics and Hydrology Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2011 www.TRB.org

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NATIONAL COOPERATIVE HIGHWAY NCHRP REPORT 682 RESEARCH PROGRAM Systematic, well-designed research provides the most effective Project 24-32 approach to the solution of many problems facing highway ISSN 0077-5614 administrators and engineers. Often, highway problems are of local ISBN 978-0-309-15537-3 interest and can best be studied by highway departments individually Library of Congress Control Number 2011921036 or in cooperation with their state universities and others. However, the 2011 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 purpose as it maintains an extensive committee structure from which The project that is the subject of this report was a part of the National Cooperative Highway 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 needs to be included in the program are proposed to the National endorse products or manufacturers. Trade or manufacturers' names appear herein solely 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

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COOPERATIVE RESEARCH PROGRAMS CRP STAFF FOR NCHRP REPORT 682 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Amir N. Hanna, Senior Program Officer Eileen P. Delaney, Director of Publications Natalie Barnes, Editor NCHRP PROJECT 24-32 PANEL Field of Soils and Geology--Area of Mechanics and Foundations Rick Renna, Florida DOT, Tallahassee, FL (Chair) Jerry Beard, North Carolina DOT, Raleigh, NC Andrea C. H. Hendrickson, Minnesota DOT, Oakdale, MN Charles Ineichen, California DOT, Sacramento, CA George H. Long, New York State DOT, Albany, NY Arthur C. Miller, Pennsylvania State University, State College, PA (retired) Donna M. Newell, NTM Engineering, Inc., Dillsburg, PA Richard S. Olsen, US Army Corps of Engineers, Vicksburg, MS Kornel Kerenyi, FHWA Liaison G. P. Jayaprakash, TRB Liaison AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 24-32 by Ocean Engineering Associates, Inc. (OEA) and the Civil and Environmental Engineering Department at the University of Auckland. Dr. D. Max Sheppard, President of OEA, is the Principal Investigator. Co-investigators on the project were Dr. Bruce Melville, Professor and Chair of the Civil and Environmental Engineering Department at the University of Auckland in Auckland, New Zealand, and Dr. Huseyin Demir, Hydraulics and Coastal Engineer with OEA, Inc. The authors thank the NCHRP Project 24-32 panel for their helpful questions, comments, and suggestions and the many researchers and practitioners for their contributions to this study.

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FOREWORD By Amir N. Hanna Staff Officer Transportation Research Board This report presents recommendations for (1) a predictive equation for equilibrium local scour and (2) a potential equation for predicting scour evolution rates at wide piers and skewed piers. These equations provide better estimates of local scour and scour evolution rates than those predicted by currently available equations. Such estimates will reduce over- predictions and the unwarranted need for countermeasures. The material contained in the report should be of immediate interest to state hydraulic engineers and others involved in the design, operation, and maintenance of highway bridges. Current methods for predicting local scour at bridge piers, including those described in Hydraulic Engineering Circular No. 18 (Publication No. FHWA NHI 01-001, "Evalu- ating Scour at Bridges"), were developed on the basis of small-scale laboratory studies with limited consideration of the factors relevant to wide piers and long skewed piers. Because of these limitations, the current methods generally overpredict local scour at such piers, leading to the use of unwarranted and costly foundations or countermeasures. Therefore, research was needed to evaluate current methods for predicting local pier scour and their applicability to wide piers and long skewed piers and to develop improved methods for use by highway agencies in the design, operation, and mainte- nance of highway bridges. Under NCHRP Project 24-32, "Scour at Wide Piers and Long Skewed Piers," Ocean Engi- neering Associates, Inc. of Gainesville, Florida, worked with the objectives of developing methods and procedures for predicting time-dependent local scour at wide piers and at long skewed piers. The research was limited to noncohesive soils and steady flow. The research included a review of the existing laboratory and field data and predictive methods relevant to time-dependent and equilibrium local scour around piers. As part of this review, methods/equations that appeared applicable for predicting time-dependent local scour at wide piers and at long skewed piers were identified and subjected to an initial screening. This screening included an assessment of the laboratory and field data that were used in developing these methods/equations and the practicality of predictions. The methods/ equations that were found to be relevant to this research were identified for further analy- sis; others were excluded from further consideration. Following further analysis, the research recommended modified forms of existing equations for use in predicting equilib- rium local scour and scour evolution rates at wide and skewed piers as well as at piers of other widths. Using the recommended methods/equations will reduce local scour overpre- dictions that are often obtained using currently available equations and thus reduce unwar- ranted need for costly countermeasures.

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Appendixes A through E contained in the research agency's final report provide further elaboration on the work performed in this project. These appendixes are not published herein; they are available on the NCHRP Report 682 summary web page at http://www.trb.org/ Main/Blurbs/164161.aspx.

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CONTENTS 1 Summary 4 Chapter 1 Introduction 4 Background 4 Objectives 4 Project Description 5 Report Organization 6 Chapter 2 Research Approach 8 Chapter 3 Data Acquisition and Analyses 8 Equilibrium Local Scour Data 9 Assessment of Data Quality 14 Local Scour Evolution Data 16 Chapter 4 Equilibrium Local Scour Predictive Equations 16 Introduction 19 Initial Screening of Equilibrium Scour Predictive Equations 24 Modifications to Equilibrium Scour Predictive Methods 26 Evaluation of Equilibrium Scour Predictive Methods 37 Chapter 5 Local Scour Evolution Predictive Methods 37 Introduction 40 Initial Screening of Scour Evolution Predictive Methods 40 Modifications of Scour Evolution Predictive Methods 41 Final Evaluation of Scour Evolution Predictive Methods 45 Chapter 6 Scour at Piers Skewed to the Flow 48 Chapter 7 Summary and Recommendations for Future Research 48 Summary 50 Recommendations for Future Research 51 References 53 List of Symbols 55 Appendices Note: Many of the photographs, figures, and tables in this report have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions.