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8 caused by the integral connection as it also has been seismic response in the longitudinal and transverse directions. reported for conventional bridges. Many of the bridges Using simplified strut-and-tie models to represent the joint reported in the responses are new bridges and, hence, force conditions, these methods established efficient rein- long-term performance data were not available. forcement details suitable for integral box-girder concrete The difficulties faced during construction of integral bridge joints. The investigation of alternative design methods pier cap bridges included the congestion of reinforce- included large-scale experimental tests and detailed analytical ment at the columns-to-pier-cap joint and the need for a studies (410), which are summarized in Appendix B (pro- substantial temporary shoring system. vided on the accompanying CD-ROM). Despite common application in non-seismic regions and in See Appendix A for more detailed analyses of the question- some seismic regions such as in Washington State, precast con- naire responses. crete girders have seldom been used in California. The limited use of precast girders in California was attributed to the lack of design methods and past experimental research confirming sat- 2.1.2 Summary of Literature Review isfactory seismic behavior. Consequently, the Precast Concrete Manufacturers Association of California (PCMAC) and Cal- A comprehensive literature review was performed as part trans sponsored a research program at UCSD to investigate the of the NCHRP 12-54 Project. Over the course of the project, seismic response of precast spliced-girder bridges with integral other newer relevant articles and reports were reviewed and piers (11). Similar to the previous UCSD studies, cast-in-place added to the documentation. columns and cap beams as well as cast-in-place integral con- At the time of the literature study, some critical aspects of nections between the cap beam and column were used in this the prototype structure to be used in the NCHRP 12-54 Proj- research project. However, the soffit slab, which was assumed ect were not finalized. These included the type of cap beam to be assisting the joint force transfer in the previous box girder (i.e., steel versus concrete), type of concrete bent (i.e., single studies, did not exist in the precast, spliced-girder bridge. column versus multiple column), and the critical loading direc- Using both the bulb-tee and bathtub precast girders, the project tion (i.e., transverse, longitudinal, or both). In fact, informa- demonstrated that the integral precast splice-girder bridge sys- tion obtained from the literature review was used in deciding tem without soffit slab can be constructed cost-effectively to that the research of the NCHRP Project 12-54 should focus produce satisfactory seismic response. on the longitudinal direction seismic response of a prototype A logical next step in the seismic bridge design advance- bridge with a single-column concrete bent and a steel cap ment was the investigation of the integral bridge system with beam. Consequently, the literature review generally focused concrete columns and a steel superstructure, because the use on past research and past use of integral pier bridges in both of steel members in the superstructure can provide additional seismic and non-seismic regions. benefits over those realized with the precast concrete girder Most of the research materials relevant to seismic applica- tions of integral column bridges were found to be based on system (12). Although such a design is the subject of the research sponsored by the California Department of Trans- NCHRP 12-54 Project, Caltrans initiated a similar investiga- portation (Caltrans) following the 1989 Loma Prieta Earth- tion at UCSD around the same time that NCHRP 12-54 was quake. This event demonstrated that integral connections of approved for research. Using the prototype structure from the concrete bridges in California were not sufficiently designed precast spliced-girder research project, the UCSD study exam- and detailed to permit bridges to experience ductile seismic ined an integral steel girder bridge system with a concrete cap response. As a result of damage to the cap beam-to-column beam (13,14) whereas the NCHRP Project 12-54 has investi- integral connections, several bridges experienced significant gated the use of steel girders supported on, and connected inte- damage, including collapse, in the Loma Prieta Earthquake grally to, steel box-beam pier caps. The pier caps are assumed (3,4). Throughout the 1990s, researchers at the San Diego and to be supported on reinforced concrete columns. The con- Berkeley campuses of the University of California conducted nection between the columns and the pier cap is accomplished vigorous experimental seismic research on various aspects of by extending the column longitudinal reinforcement through concrete box-girder bridges with integral concrete columns. holes in the bottom flange of the box-beam pier cap. The com- This particular bridge type was singled out because of its wide- partment of the box-beam pier cap directly above a column is spread application in California. The research effort, which was then filled with concrete to anchor the column reinforcement. generally initiated to characterize the behavior of existing struc- The UCSD study included several component tests repre- tural members, investigated retrofit techniques, repair methods senting the integral connection region, which included a con- and improved design methods for columns, cap beams, foun- crete cap beam, two interior girders, and a support block mod- dations, and cap beam-to-column integral connections. eling the concrete column. The loads were applied directly to Of particular interest to the investigation undertaken in the the girders with the main objective of investigating the con- NCHRP 12-54 project were the alternative methods studied nection between the steel girder and the concrete cap beam. at the University of California at San Diego (UCSD) for Two girder parameters were investigated in the component designing cap beam-to-column concrete integral joints for tests, namely girders with web stiffeners in the cap-beam