Investigating seismic behavior of horizontally curved RC bridges with different types of irregularity in comparison with equivalent straight bridges

Abstract

In this paper, the seismic behavior of a total of 84 reinforced concrete bridges, including 12 straight and 72 curved bridges was studied. The bridges were designed and detailed according to the American Association of State Highway and Transportation Officials (AASHTO) regulations. To evaluate the accuracy of the seismic response predictions obtained using elastic analyses, as suggested by AASHTO, both linear and nonlinear time history analyses were performed and the results were compared. In addition, to investigate the accuracy of the code provisions regarding the limitations on the bridge subtended angle for the use of equivalent straight bridges, the results obtained for the curved bridges were compared with those obtained for the equivalent straight bridges. Furthermore, the effects of different types of irregularity on the predicted displacement demands from equivalent straight bridges were investigated. To study the effects of different types of irregularity on the results, different irregular arrangements of spans, various column heights, different abutment conditions, and different subtended angles were considered. Also the effect of combination of different types of irregularity was investigated by considering bridges with different configurations. The results indicated that the deviation of the results obtained from the linear and nonlinear analyses is significant, particularly in the transverse direction of the bridges with irregularity in columns height for different subtended angles. Also, it was shown that in bridges with restrained abutments, unlike the bridges with unrestrained (i.e., free) abutments, the equivalent straight bridges cannot be used in lieu of the curved bridges, since the differences between the results from the two models are significant and become larger with increasing the subtended angle of the bridges. It was shown that some modeling assumptions widely used for seismic analysis of bridge structures can be unrealistic and may lead to inaccurate predictions. It was shown that the AASHTO specifications regarding the use of elastic analysis for some irregular bridges and the limitations on the subtended angle for the use of equivalent straight bridges need to be reevaluated.