National Cooperative Highway Research Program Synthesis of Flighway Practice 276 Geotechnical Related Development and Implementation of Load and Resistance Factor Desigt lI ff Efìl N,rfaflr.-ã o \I-¡.[\r u, IYt\.Lllarllr) GEORGE GOBLE Goble Rausche Likins & Assoc., lnc Boulder, Colorado Topic Panel R. SCOTT CHRISTIE, Pennsylvania Deparlment oÍ Transportation JAMES G. CUTHBERTSON, Wasfington State Department of TransporTat¡on JERRY A. DIMAGGIO, Federal Highway Administration CHRISTOP H ER DUMAS, Federal H ighway Adm inistratìon RICHARD ENDRES, Mìchigan Deparlment of Transportatìon ROGER GREEN, University of Wateloo, Ontario, Canada G. P. JAYAPRAKAS H, Iranspo rlation B e search Board PAUL PASSE, Florida Department of Transportation TERRY J. SHIKE, Oregon Deparfment of Transportat¡on (etired) JAMES L. WITHIAM, Monroeville, Pennsylvania ? L.i c.ï Transportation Research Board National Research Council Research Sponsored by the American Association of State Highway and Transportation Otficials ¡n Cooperation with the Federal Highway Administration Subject Areas Highway and Facility Design; Bridges, Other NATIONAL ACADEMY PRESS Structures and Hydraulics and Hydrology; Washington, D.C. 1999 Soils, Geologty, and Foundations NATIONAL COOPEBAÏIVE HIGHWAY RESEARCH PROGRAM NCHRP SYNTHESIS 276 Systematic. well-designed research provides the most effective Project 20-5 FY 1996 (topic 28-02) approach to the solution of many problems facing highway ad- ISSN 0547-5570 ministrators and engineers. Often, highway problems are of local ISBN 0-309-06854-1 interest and can best be studied by highway departmens indi- Library of Congress Catalog Ca¡d No.99-741 17 {O 1999 'Iransporta.tion Research Board vidually or in cooperation with their state universities and t'¡th- ers. However', the accelerating growth of highway transportation develops inc.reasingly complex problems of wide interest to Price $27.00 highway autho¡ities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the Ame¡ican Association of State Highway and Transportation Officials initiated 1962 an objective national highway re- Á NOTICE search program employing modem scientific techniques. This program suppolted a is on continuing basis by funds from par- 'fhe project that is the subject of this report was a part of the National Coop ticipating member states of the Association and it receives the erative l{igh'ilay Resea¡ch hogram conducted by the Transportation Re- full cooperation and support of the Federal Highway Admini- search Board with the approval ofthe Governing Boald ofthe National Re- shation, United States f)epartment of Transportation. search Council. Such approval reflects the Governing Board'sjudgment that the program concemed is of natioual import¿nce and appropriate wilh re- The Transportation Research Boa¡d of the National Resealch spect to both the purposes and resources ofthe National Resea¡ch Council. Council was requested by the Association tr¡ administer the re- The members of the technical conrmittee selected to monitor this project search program because of the Board's recognizecl objectivity and to review this report were chosen for recognized scholarly competeDce and unde¡standing of modem research practices. The Board is a¡d with due consideration for the balance of disciplines appropdate to the uniquely suited for this purpose as it maintains an extensive project. The opinions and conclusions expressed or implied a¡e those of the research agency that the research, and, while they have been ac' committee slructure from which authorities on àny highway ¡ærformed cepted as appropriate by the technical cornmittee, they are not necessarily fansportation subject may be drawn; it possesses avenues of those of the Transportation Research Board, the National Research Coutcil, communication ancl cooperation with federal, state, and local the Ame¡ican Assocration of State I-lighway and Transportation Offcials, or ttre goverumental agencies, universities, and indusn-y; its l'elation- F'ederal Highway Aclminist¡ation of the ti.S. Department of Transportation. Each repol is reviewed and accepted publicalion the ship to the National Rese¿rch Council is ¿n insurance of objec- for by technical co¡nniltee according to procedures established and monitored by the Trans- tivity; it maintains a full-time research correlation staff of spe- portation Resea¡ch Boa¡d Executive Committee and the Governing Board of cialists in highway transpr:rtation matters to bring the findings of the National Resea¡ch Council. research directly to those who are in a position to use them, The National Research Council was established by the National Acad- The program is developed on the basis of research needs enry of Sciences ill 1916 to associate the broad comrnunity of science and technology wittr ttre Academy's purposes of furthering knowledge and of identified by chief administrato¡s of the highway ancl h'ansporta- arlvisilg the F-ederal Government. The Council has become the principal op tion departmenls and committees year, by of AASHTO. Each erating agency of both the National Academy of Sciences a¡d the National specilÌc a¡eas of resea¡ch needs to be included in the program are Academy of Engrneer-ing in the conduct of their services to the govemment, proposed to the National Research Council and tl¡e Board by the the public, and the scientifc and engineering communities. It is administered 'fhe American Association of State Highway and Transportation Of- joiutly by both Ac¡demies and the Institute of Medicine. National Academy of Engineering and the Institute of Medici¡e were established in ñcials. Research pr<rjects to fulfill these needs are defined by the 1964 ancl 1970, respectively, under the charter ofthe National Academy of Board, and qualified resealch agencies are selected lìom those Sciences. that have submitted proposals. Administration and surveillance The'lÌarsportatior Research Boa¡d evolvet-l in 1974 from the Highway of research contracts are the responsibilities of the National Re- Research Board, which was established in L92O. The TRB incorporates all search Council and the Transportation Research Btl¿rd. fòrmer HRB activities and also perfbrms additional functions under a broader scope involving all modes of transportation and the interactions of The needs for highway research are many, and the National trausportatiou with society. Cooperative Higbway Research Pmgrnm can make significant contibutions to the solution of highway transpoltation problerns of mutual concern to many responsible groups. The program. however, is intended to complement rather than to substitute for PubLished reports <tf the or duplicate other highway researcll programs. NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM ' .;.. .1 are available from: Transportation Research Board National Research Council 2l0l Constitution Avenue, N.W. Washington, D.C. 20418 NOTE: The Transporfation Research Board, the National Research Council, the Federal High*y Administration, the American Associa- and <:an be ordered through the Internet at: tion of State Highr*ay and Transportation Oflicials, and the individr¡al states participating in the National Cooperative Highn"¿y Research http://www. nas.edu/trb/index.html Program do not endorse products or manufactu¡ers. Trade or manu- facturer:s'nâmes âppeâr herein solely because they âre considered essential to the object of this rcporL Printed in the tinited States of America PREFACE A vast storehouse ofinformation exists on nearly every subject of concern to highway administrâtors and engineers. Much of this information has resulted from both research and the successful application of solutions to the problems faced by practitioners in their daily work. Because previously there has been no systematic means for compiling such useful information and making it available to the entire community, the American As- sociaúon of State Highway and Transportation Offîcials has, tlrough the mechanism of the National Cooperative Highway Research Program, authorized the Transportation Þece¡r¡h Rnerrl rn rrn¡lerfqke a cnntinuino nrnienfr-'J--- tn search onf and sr¡nfhesize, llseñll knowledge from all available sources and to prepare documented reports on current practices in the subject areas of concem. This synthesis series reports on various practices, making specific recommendaúons where appropriate but without the detailed directions usually fourd in handbooks or de- sign manuals. Nonetheless, these documents cân serve similar purposes, for each is a compendium of the best knowledge available on those measures found to be the most successful in resolving specific problems. The extent to which these reports are useful will be tempered by tle user's knowledge and experience in tbe particular problem area. FOREWORD This synthesis report will be of interest úo geotechnical, structural, and bridge engi- By Staff neers, especially those involved in the development and implementation of the geotech- Transporlation nical a;pects of tle AASHTO Bridge Code. The synthesis documents a review of Resea.rch Board geotechnical related LRFD specifications and their development worldwide in order to compare them with the current AASIilO LRFD Bridge Code. Design procedures for foundations, earth retaining structures, and culverts are summarized and compared to methods specif,red by tle AASHTO code. Administrators, engineers, and researchers ile corìtinually faced with highway problems on which much