Assessment of Current Pushover Analysis for Irregular Continuous Bridges

Assessment of Current Pushover Analysis for Irregular Continuous Bridges

Pushover analysis provides a simple process in studying the nonlinear behavior of structures, thus, it has rapidly become popular for the seismic evaluation of bridges in recent years. Before its comprehensive application in the earthquake engineering community, it has been an urgent issue to clarify quantitatively the limitation of this method in order that the erroneous results that might be produced by the direct application of current procedure to all types of bridges can be prevented. Pushover analysis which originally developed for building structures has two inherent drawbacks: that it is restricted with a single-mode response, and that the lateral force distribution during pushover process is invariant. As such, the procedure can be reliably applied only to regular structures and it can not account for the variation of inertial force pattern after structure yields. Several researchers in the past few years have proposed some improved methods to overcome this problem. However, again, most of these refined procedures were aimed at solving problems related to building structures. Due to the intrinsic difference of seismic responses between building structures and bridge structures, further clarification of the circumstances under which these improved methods can produce reliable estimates for bridges in the practice is needed. This research attempts to specify the scope of applicability for current pushover analysis on multi-span continuous bridge structures. Also discussed are the contributions of higher modes for bridges with different degrees of irregularities.