293 NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM REPORT 293 METHODS OF STRENGTHENING EXISTING HIGHWAY BRIDGES TRANSPORTATION RESEARCH BOARD NATIONAL RESEARCH COUNCIL TRANSPORTATION RESEARCH BOARD EXECUTIVE COMMITTEE 1987 Officers Chairman LOWELL B. JACKSON, Executive Director, Colorado Department of Highways Vice Chairman HERBERT H. RICHARDSON, Deputy Chancellor and Dean of Engineering, Texas A & M University Secretary THOMAS B. DEEN, Executive Director. Transportation Research Board Members RAY A. BARNHART, Federal Highway Administrator, U.S. Department of Transportation (ex officio) JOHN A. CLEMENTS, Vice President. Sverdrup Corporation (Es officio, Past Chairman, 1985) DONALD D. ENGEN, Federal Aviation Administrator. U.S. Department of Transportation (ex officio) FRANCIS B. FRANCOIS, Executive Director, American Association of State Highway and Transportation Officials (ex officio) E. R. (VALD) HEIBERG III, Chief of Engineers and Commander U.S. Army Corps of Engineers. Washington. D.C. (ex officio) LESTER A. 1-IOEL, Hamilton Professor and Chairman. Department of Civil Engineering. University of Virginia (ex officio, Past Chairman, 1986) RALPH STANLEY, Urban Mass Transportation Administrator, U.S. Department of Transportation (cii officio) DIANE STEED, National Highway Traffic Safety Administrator, U.S. Department of Transportation (ex officio) GEORGE H. WAY, Vice President for Research and Test Department, Association of American Railroads (ex officio) ALAN A. ALTSHULER, Dean, Graduate School of Public Administration. New York University JOHN R. BORCHERT, Regents Professor, Department of Geography. University of Minnesota ROBERT D. BUGHER, Executive Director. American Public Works Association DANA F. CONNORS, Commissioner, Maine Department of Transportation C. LESLIE DAWSON, Secretary, Kentucky Transportation Cabinet PAUL B. GAINES, Director of Aviation, Houston Department of Aviation LOUIS J. GAMBACCINI, Assistant Executive Director/Trans-Hudson Transportation of The Port Authority of New York and New Jersey JACK R. GILSTRAP, Executive Vice President, American Public Trons,t Association WILLIAM J. HARRIS, Snead Distinguished Professor of Transportation Engineering. Dept. of Civil Engineering, Texas A & M University WILLIAM K. HELLMAN, Secretary, Maryland Department of Tansportation RAYMOND H. HOGREFE, Director—State Engineer. Nebraska Department of Roads THOMAS L. MAIN WARING, Consultant to Trucking Industry Affairs for Ryder System. Inc. JAMES E. MARTIN, President and Chief Operting Officer. Illinois Central Gulf Railroad DENMAN K. McNEAR, Chairman, President and Chief Executive Officer. Southern Pacific Transportation Company LENO MENGHINI, Superintendent and Chief Engineer. Wyoming Highway Department WILLIAM W. MILLAR, Executive Director, Port Authority Allegheny County. Pittsburgh MILTON PIKARSKY, Distinguished Professor of Civil Engineering, City College of New York JAMES P. PITZ, Director, Michigan Department of Transportation JOE G. RIDEOUTrE, South Carolina Department of Highways and Public Transportation TED TEDESCO, Vice President, Resource Planning, American Airlines. Inc., Dallas/Fort Worth Airport CARL S. YOUNG, Broome Country Executive, New York NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Transportation Research Board Executive Committee Subcommittee for NCHRP LOWELL B. JACKSON, Colorado Department of Highways (Chairman) FRANCIS B. FRANCOIS, Amer. Assn. of State Hwy. & Transp. Officials HERBERT H. RICHARDSON, Texas A & M University RAY A. BARNHART, U.S. Dept. of Transp. LESTER A. HOEL, University of Virginia THOMAS B. DEEN, Transportation Research Board Field of Design Area of Bridges Project Panel, C12-28(4) FRED G. SUTHERLAND, Virginia Dept. of Highways and Transp. (Chairman) ALLAN HARWOOD, Oregon Dept. of Transportation JAMES W. BALDWIN, JR., University of Missouri PREDRAG L. POPOVIC, Wits, Janney, Elstner Assoc., Inc. ROBERT M. BARNOFF, R. M. Barnoff & Associates. Inc. ROBERT WOOD, Federal Highway Administration FREDRICK R. BECKMANN, American Institute of Steel Construction JOHN O'FALLON, FHWA Liaison Representative JIM DODSON, Nevada Dept. of Transportation WILLIAM G. GUNDERMAN, TRB Liaison Representative Program Staff ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Senior Program Officer ROBERT E. SPICHER, Associate Director DAN A. ROSEN, Senior Program Officer LOUIS M. MACGREGOR, Program Officer HARRY A. SMITH, Senior Program Officer IAN M. FRIEDLAND, Senior Program Officer HELEN MACK, Editor NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM REPORT 293 METHODS OF STRENGTHENING EXISTING HIGHWAY BRIDGES F. W. KLAIBER, K. F. DUNKER, T. J. WIPF and W. W. SANDERS, JR. Engineering Research Institute Iowa State University Ames, Iowa RESEARCH SPONSORED BY THE AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFFICIALS IN COOPERATION WITH THE FEDERAL HIGHWAY ADMINISTRATION AREAS OF INTEREST: Structures Design and Performance General Materials Maintenance (Highway Transportation) TRANSPORTATION RESEARCH BOARD NATIONAL RESEARCH COUNCIL WASHINGTON, D.C. SEPTEMBER 1987 NATIONAL COOPERATIVE HIGHWAY RESEARCH NCHRP REPORT 293 PROGRAM Project 12-28(4) FY'85 Systematic, well-designed research provides the most effec- ISSN 0077-5614 tive approach to the solution of many problems facing high- ISBN 0-309.04416-2 way administrators and engineers. Often, highway problems are of local interest and can best be studied by highway de- L. C. Catalog Card No. 87-51165 partments individually or in cooperation with their state universities and others. However, the accelerating growth Price $12.00 of highway transportation develops increasingly complex problems of wide interest to highway authorities. These NOTICE problems are best studied through a coordinated program of The project that is the subject of this report was a part of the National Co- operative Highway Research Program conducted by the Transportation Re- cooperative research. search Board with the approval of the Governing Board of the National Research Council. Such approval reflects the Governing Board's judgment In recognition of these needs, the highway administrators of that the program concerned is of national importance and appropriate with the American Association of State Highway and Transpor- respect to both the purposes and resources of the National Research Council. tation Officials initiated in 1962 an objective national high- The members of the technical committee selected to monitor this project and way research program employing modern scientific tech- to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the proj- niques. This program is supported on a continuing basis by ect. The opihions and conclusions expressed or implied are those of the re- funds from participating member states of the Association search agency that performed, the research, and, while they have been and it receives the full cooperation and support of the Fed- accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National Research Council, eral Highway Administration, United States Department of the American Association of State Highway and Transportation officials, or Transportation. the Federal Highway Administration, U.S. Department of Transportation. Each report is reviewed and accepted for publication by the technical com- The Transportation Research Board of the National Re- mittee according to procedures 'established and monitored by the Transpor- search Council was requested by the Association to admin- tation Research Board Executive Committee and the Governing Board of the ister the research program because of ihe Board's National Research Council. recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as: it maintains an extensive committee strUcture from which Special Notice authorities on any highway transportation subject may be The Transportation Research Board, the National Research Council, the Fed- eral Highway Administration, "the American Association of State Highway drawn; it possesses avenues of communications and cooper- and Transportation Officials, and the individual states participating in the ation with federal, state, and local governmental agencies, National Cooperative Highway Research Program do not endorse products or universities, and industry; its relationship to the National manufcturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of this report. Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in high- way transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and trans- portation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State High- way 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 pro- posals. Administration and surveillance of research contracts Published reports of the are the responsibilities of the National