1、 i Seismic Response of Concrete Bridges Editor K. Krishnan o international SP- 187 Obb2999 0544951 235 H DISCUSSION of individual papers in this symposium may be submitted in accordance with general requirements of the AC1 Publication Policy to AC1 head- quarters at the address given below. Closing
2、date for submission of discussion is January, 2000. All discussion approved by the Technical Activities Committee along with closing remarks by the authors will be published in the May/June 2000 issue of either AC1 Structural Journal or AC1 Materials Journal depending on the subject emphasis of the
3、individual paper. The Institute is not responsible for the statements or opinions expressed in its publications. Institute publications are not able to, nor intended to, supplant indi- vidual training, responsibility, or judgment of the user, or the supplier, of the information presented. The papers
4、 in this volume have been reviewed under Institute publication proce- dures by individuals expert in the subject areas of the papers. Copyright O 1999 AMERICAN CONCRETE INSTITUTE P.O. Box 9094 Farmington Hills, Michigan 48333-9094 All rights reserved including rights of reproduction and use in any f
5、orm or by any means, including the making of copies by any photo process, or by any electronic or mechanical device, printed or written or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the
6、copyright proprietors. Printed in the United States of America Editorial production: Jane D. Carroll Library of Congress catalog card number: 99-63795 PREFACE This special publication contains papers presented during the following four AC1 convention sessions sponsored by Committee 34 1, Earthquake-
7、Resistant Concrete Bridges, during 1995 and 1996: Eflects of Recent Earthquakes on Concrete Bridges-Performance, Retrofit, and Design Response of Concrete Bridges during the Northridge Earthquake Seismic Retrojt and Design of Concrete Bridges State-of-Knowledge in Earthquake Response of Concrete Bri
8、dges Five Years aJer the Lorna Prieta Earthquake A total of 24 papers were presented at the sessions, of which 17 papers were received for this publication. The papers were reviewed in accordance with the policies of the American Concrete Institute. The papers presented cover a wide array of subject
9、s related to seismic behavior of concrete bridge structures. Topics include the impact of recent earthquakes on the seismic design process, results of recent experimental research on behavior of bridge components during earthquakes, case studies of bridge seismic upgrades, and the use of composite m
10、aterials and seismic isolation systems to enhance seismic performance. This special publication has been made possible by contributions from many individuals. M. Saiid Saiidi, the founding chairman of this committee, gave his early leadership and support to this project. The editor is grateful to al
11、l authors who have contributed to the publication as well as the reviewers of the papers for their suggestions and comments. The cooperation of the authors in accepting reviewers suggestions and revising their manuscripts accordingly is greatly appreciated. The editor acknowledges the support of Fre
12、deric R. Harris, Inc., without which this publication would not have been possible. Editor K. Krishnan I Obb2949 0544953 008 m CONTENTS J IMPACT OF LOMA PRIETA EARTHQUAKE ON SEISMIC DESIGN OF CONCRETE BRIDGES-CALIFORNIA PERSPECTIVE by J. E. Roberts 1 NORTHRIDGE EARTHQUAKE INFLUENCE ON BRIDGE DESIGN
13、CODE by R. Zelinski . 17 LESSONS LEARNED FROM BRIDGE PERFORMANCE DURING NORTHRIDGE EARTHQUAKE by F. Seible and M. J. N. Priestley . 29 PERFORMANCE OF REINFORCED CONCRETE BRIDGES IN JANUARY 1995 HYOGOKEN NANBU (KOBE) EARTHQUAKE by A. W. Taylor 57 INVESTIGATION OF PERFORMANCE OF BRIDGE ABUTMENT FILLS
14、IN 1994 NORTHRIDGE EARTHQUAKE by R. V. Siddharthan and M. El-Gama1 . 69 NEW DEVELOPMENTS IN CALTRANS SEISMIC ANALYSIS AND DESIGN PROCEDURES FOR BRIDGES by M. Yashinsky 89 SEISMIC PERFORMANCE OF BRIDGE FOOTINGS DESIGNED TO CURRENT STANDARDS by Y. Xiao, M. J. N. Priestley, and F. Seible 131 DESIGN AND
15、 SEISMIC RESPONSE OF UPGRADED OUTRIGGER KNEE JOINTS by B. StojadinoviC . 159 REPLACEABLE HINGE DETAILING FOR BRIDGE COLUMNS by J. B. Mander and C.-T. Cheng 185 1 SEISMIC RETROFIT OF EXISTING BRIDGE COLUMNS WITH HINGES by A. Griezic, W. D. Cook, and D. Mitchell 205 V SEISMIC RESPONSE OF REINFORCED CO
16、NCRETE DOUBLE-DECK BRIDGE STRUCTURES by S. Mazzoni, F. Zayati, J. P. Moehle, and S. A. Mahin 235 DRIFT CAPACITY OF REINFORCED CONCRETE COLUMNS SUBJECTED TO CYCLIC SHEAR REVERSALS by S. Pujol, J. A. Ramfrez, and M. A. Szen . 255 SEISMIC VULNERABILITY OF REINFORCED CONCRETE COLUMNS WITH STRUCTURAL FLA
17、RES by N. Wehbe and M. S. Saiidi 275 IMPLICATIONS OF SPATIAL VARIATION OF GROUND MOTION ON NORTHRIDGE EARTHQUAKE by G. Mylonakis, V. Simeonov, A. M. Reinhom, and I. G. Buckle 299 COLLAPSE OF SR-14/I-5 SOUTHBOUND AND OVERHEAD BRIDGE IN USE OF ENERGY DISSIPATING SYSTEMS FOR IMPROVING SEISMIC PERFORMAN
18、CE OF GAVIN CANYON UNDERCROSSING by M. Q. Feng 327 TWO-LEVEL DESIGN SPECTRUM FOR HIGHWAY BRIDGES by R. Mathur, H. Lee, and G. Orsolini . 345 EARTHQUAKE RETROFIT OF CALIFORNIA BRIDGE ROUTE 242/680 SEPARATION by R. C. Fish and G. L. Rowe 361 I , I r VI E IlbbZ999 05LiLi955 980 SP 187-1 Impact of Loma
19、Prieta Earthquake on Seismic Design of Concrete Bridges- California Perspective by J. E. Roberts Synopsis : Almost nine years have passed since the disastrous Loma Prieta earthquake of October 17, 1989 and eight years have passed since the Governors Board of Inquiry into the cause of highway structu
20、re failures during that earthquake issued its final report with the warning title “Competing Against Time“. The California Department of Transportation has developed improved Seismic Performance Criteria, Seismic Design Specifications, seismic design procedures, and construction details based on les
21、sons learned from the 1971 San Fernando earthquake and subsequent seismic events. The success of the Bridge Seismic Design and Retrofit program and the success of future seismic design for California bridges is based, to a large degree, on an unprecedented accelerated and “problem-focused“ seismic r
22、esearch program. The Department has spent over $40 million on this research and physical testing of details. This research has provided the bridge design community the assurance that the new specifications and design details perform reliably and meet the performance criteria. Caltrans staff engineer
23、s, consulting firms, independent Peer Review Teams, and university researchers have cooperated in this program of Bridge Seismic Design and Retrofit Strengthening to meet the challenge presented in the June, 1990 Board of Inquiry report. The eight year old Seismic Advisory Board has been an invaluab
24、le asset in reviewing the performance criteria, design specifications, design procedures, and construction details for both new design and retrofit strengthening of older, non-ductile bridges. Keywords: confinement; displacements; ductility; nonlinear analysis; retrofit; seismic design 1 2 Roberts D
25、irector-Engineering Services, Calif. Dept. of Transportation. BS in Civil Engineering, University of California, MS in Structural Engineering University of Southern California. Forty Five years experience including 1 O years Bridge Resident Engineer; 2 years Bridge Designer; 4 years Bridge Design Se
26、ction Supervisor, 5 years Chief Engineer-Equipment Division, 6 years Project Director- Major Light Rail Transit project, 2 years Chief-Structure Design Office,7 years Chief-Division of Structures; 1 year Deputy Director- Transportation Engineering. INTRODUCTION Prior to the 1933 Long Beach earthquak
27、e there was no special consideration for seismic design of buildings or bridges in California. The severe damage to schools that resulted from that seismic event resulted in creation of the Structural Engineer license and a requirement for speciaI consideration of seismic forces in the design of pub
28、lic schools in California. After the 1940 EI Centro earthquake the bridge design office of the California Division of Highways developed minimal seismic design factors for bridges. The 1940 El Centro record was digitized and used as the seismic design spectra for over 30 years before an earthquake o
29、f greater magnitude occurred in California. The 1971 San Fernando earthquake caused severe damage to hospitals, public utilities, and freeway bridges, recording a peak ground acceleration of 1.Og and large ground displacements. This earthquake caused both building and bridge designers to revise thei
30、r design criteria and structural details to provide better resistance to the forces and displacements of major seismic events. The American Association of State Highway and Transportation Officials (AASHTO) is the agency responsible for development of bridge design specifications for nationwide use.
31、 AASHTO has typically adopted seismic design criteria modeled after those developed in California, and the initial adoption is only as a guide specification. Until the 1989 Lorna Prieta earthquake most other states in the United States had not been concerned with seismic design for bridges, consider
32、ing it a California or West Coast problem. For example, the 1940 California seismic design specifications were not adopted by AASHTO until 1961, and the 1973 California seismic design specifications were not adopted nationally until 1983. In May, 1990, responding to the disastrous 1989 Loma Prieta e
33、arthquake in California, AASHTO finally adopted the 1983 “Guide Specifications For Seismic Design of Highway Bridges“ as a mandatory r nbb2q4q 05“q57 753 Seismic Response of Concrete Bridges 3 requirement for those states which have a seismic hazard. Interestingly, some 37 states in the US have some
34、 level of seismic hazard. Understandably, there are hundreds of bridges in these other states which have been designed to seismic criteria that are not adequate for seismic forces and displacements that we know today. The seismic retrofit details designed by the California bridge engineers can be of
35、 great benefit to those states who are faced with seismic threats of lesser magnitude, and with little financial support for seismic retrofitting, and much less for research and seismic detail development. The California State Department of Transportation (Caltrans) owns and maintains over 12,000 br
36、idges (spans over 20 feet). There are an equal number on the City and County system. The bridge office maintains the condition data for all these and some 6,000 other highway structures such as culverts (spans under 20 feet), pumping plants, tunnels, tubes, Highway Patrol inspection facilities, main
37、tenance stations, toll plazas and other transportation related structures. Structural details and the current condition data are maintained in the departments bridge maintenance files as part of the National Bridge Inventory System (NJ3IS) required by the US Congress and administered by the Federal
38、Highway Administration (FHWA). This data is updated and submitted annually to the FHWA and is the basis upon which some of the Federal gas tax funds are allocated and returned to the states. The maintenance, rehabilitation and replacement needs for bridges are prorated against the total national nee
39、ds. Seismic retrofit strengthening is eligible for use of those funds. The two most significant earthquakes in California in recent history that produced the best information for bridge designers were the 1989 Loma Prieta and the 1994 Northridge events. While the experts consider these to be only mo
40、derate earthquakes, it is important to note the good performance of the many bridges that had been designed for the improved seismic criteria or retrofitted with the early era seismic retrofit details. This reasonable performance of properly designed newer and retrofitted older bridges in a moderate
41、 earthquake is significant for the rest of the United States because that knowledge can assist engineers in designing new bridges and in designing an appropriate seismic retrofit program for their older structures. Although there is a necessary concern for the “Big One“ in California, especially for
42、 the performance of important structures, it must be noted that many structures which vehicle traffic can bypass need not be designed or retrofitted to the highest standards. It is also important to note that there will be many moderate earthquakes that will not produce the damageassociated with a m
43、aximumevent. These are the earthquake levels that should be addressed first in a multi phased retrofit strengthening program, given the limited resources that are available. Cost benefit analysis of retrofit details is essential to measure and insure the effectiveness of a program. It has been the C
44、alifornia experience that a great deal II Obb2947 05r14758 b7T 4 Roberts of insurance against collapse can be achieved for a reasonable cost, typically ten percent of replacement cost for normal highway bridges. It is also obvious that designing for a performance criteria that provides full service
45、immediately after a major earthquake may not be economically feasible. The expected condition of the bridge approach roadways after a major seismic event must be evaluated before large investments are made in seismic retrofitting the bridges to a full service criteria. There is little value to the i
46、nfrastructure in investing large sums to retrofit a bridge if the approaches are not functioning after a seismic event. Roadways in the soft muds around most harbors and rivers are potentially liquefiable and will require repair before the bridges can be used. Approximately 2,200 of Californias 12,0
47、00 bridges are located in the Los Angeles area so it is significant to examine the damage and performance of bridges in the Northridge earthquake of January 17, 1994. About 1,200 of these bridges were in an area that experienced ground accelerations greater than 0.25g and several hundred were in the
48、 area that experienced ground accelerations of 0.50g or greater. There were 132 bridges in this area with post San Fernando retrofit details completed (Hinge and Joint restrainer cables) and 63 with post Loma Prieta retrofit details completed (Additional joint restrainers and column strengthening).
49、Ail of these retrofitted bridges performed extremely well (not closed to public traffic) and most of the other bridges performed well during the earthquake; newer bridges designed and constructed to Caltrans current seismic specifications survived the earthquake with very little damage. Seven older bridges, designed for a smallerearthquake force or without the ductility of caltrans current design, sustained severe damage during the earthquake. Another 230 bridges suffered some damage ranging from serious problems of column and hinge damage to crac
