Pushover Analysis of Irregular Bridges

Pushover Analysis of Irregular Bridges

A rational seismic evaluation and design for a structure have to be based on the accurate prediction of its inelastic displacement demand and capacity. Therefore, displacement-based seismic evaluation and design has increasingly become the main stream for the design code of the next generation. Because nonlinear static pushover analysis can obtain failure mechanism and sequence of a structure which are both not easy to be obtained through strength-based design, and that two widespread-used commercial engineering softwares, ETABS and SAP2000, provide pushover analysis capacity, pushover analysis has become rapidly popular in the engineering community for seismic evaluation of various structures in recent years. However, the conventional single-mode pushover procedure provided by SAP2000 can only be applied reliably to a structure that is mainly controlled by first mode. For a complex structure where higher mode is important, single-mode pushover analysis cannot predict accurately the structure’s nonlinear displacement. Moreover, the results of conventional pushover analysis depend on the choices of the single monitored point. For an irregular bridge, it is not easy to select the proper point to be monitored. Different choices of monitored point from different evaluators may lead to different seismic evaluation results for the same structure. This phenomenon is not acceptable. Therefore, to establish a generally acceptable pushover procedure that can reasonably consider the effects of all important modes is needed. The purpose of this current study aimed to clarify the scope of applicability for the conventional single-mode pushover analysis on the multi-span continuous bridge with different degrees of irregularities. A simple pushover procedure, which is more suitable for irregular bridge, has been proposed.