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7 CHAPTER 2 FINDINGS 2.1 STATE-OF-THE-ART SUMMARY with the substructures). Among the responses from domestic practicing engineers, six indicated designing bridges with Two different approaches to collecting data on the state of integral pier caps in the past. Only one of the responses the art of integral connections were studied. First, the state of received from abroad indicated past use of integral pier caps. practice was studied through the questionnaire on past use of The analyses of the responses to the questionnaire are pro- integral connections. Second, the state of research was stud- vided in Appendix A. The main conclusions from the responses ied through the literature search. The summary of the results to the questionnaire were as follows: of these studies is presented below. The details of the state of practice and the literature search are presented in Appendixes The main reason for using integral pier caps in the past A and B, respectively (which are included on the accompa- has been to increase underclearance and to avoid placing nying CD-ROM). the pier caps at a sharp skew (94 percent of the cases). Enhancing seismic performance was cited in 33 percent of the cases. 2.1.1 State of Practice The total number of bridges with integral pier caps The questionnaire on past use of integral connections reported in the responses is 59 (i.e., 47 bridges reported was sent to all AASHTO voting and nonvoting members by state DOTs and 12 bridges reported by domestic prac- (i.e., DOTs in all states and Canadian provinces, and quasi- ticing engineers; however, some bridges may have been governmental authorities such as turnpike authorities). reported in both groups). In addition, the questionnaire was slightly modified and Plate girders were used in the superstructures of most sent to domestic researchers and bridge designers and inter- bridges with integral pier caps. national bridge designers. The modifications were intended Most integral pier caps (76 percent) are supported on to allow the person responding to comment on the perfor- single-column piers, 8 percent are supported on multi- mance of bridges he or she did not design but is familiar with, column piers, and the type of piers was not defined for provide contact information on the designer of bridges with the remaining bridges. integral pier caps, or forward the questionnaire to the bridge Most integral pier caps (90 percent) are made of con- designer. The modified questionnaire was sent to 30 domes- crete. The remaining pier caps are made of steel. tic bridge designers and 20 international bridge designers in No accurate cost data were available. The respondents 12 countries (i.e., Japan, France, the United Kingdom, Canada, estimated that the weight of the steel was decreased by Switzerland, Denmark, Poland, Portugal, Germany, Austria, 5 to 10 percent and the cost of fabrication and the cost Spain, and Egypt). of erection both increased 5 to 10 percent. However, in In addition to the questionnaire, information was solicited one case it was estimated that the use of integral pier from the American Iron and Steel Institute (AISI), the Amer- caps eliminated the need to raise the approach roadway ican Institute of Steel Construction (AISC), and the National elevation leading to an estimated savings of $250,000 Steel Bridge Alliance (NSBA). Also, the manufacturers of for each 305 mm (12 in.) difference in elevation. prestressing systems were asked to provide information on In most cases, the forces acting on the superstructure and the bridges where their systems were used to post-tension the substructures were calculated taking into account the concrete integral pier caps. frame action between the superstructure and substructure. In total, 111 copies of the questionnaire were sent out. A In a few cases the frame action was ignored in designing total of 67 responses were received. The breakdown of the the superstructure or in designing both the superstructure responses is given in Appendix A (provided on the accom- and the substructure. panying CD-ROM). Among the responses, 11 state DOTs In general, past performance of integral pier cap bridges indicated past use of integral pier caps. However, two of these appears to be satisfactory. Deck cracking transverse to responses indicated that the pier caps were integral with the the girders is the most cited problem. However, it was superstructure but were supported on bearings (not integral concluded that this type of cracking does not seem to be