Development of a pseudostatic method for seismic performance evaluation of rocking bridge foundations

Pseudostatic analysis can be an efficient approach to evaluating the dynamic response of structures for a preliminary design. In this paper, we present a pseudostatic method based on a pushover analysis to assess the seismic performance of bridge piers supported by rocking-governed shallow foundations. The method has two stages. In the first stage, the capacity spectrum method (CSM) is applied to evaluate the maximum acceleration and displacement response of the bridge system. To have an appropriate system damping ratio in the CSM, we propose a method to consider various earthquake energy dissipation mechanisms for the pier and foundation. In the second stage, the footing settlement is evaluated based on the maximum footing rotation; an incrementally cyclic pushover analysis with a fixed footing rotation increment is performed to estimate the footing settlement. Examples are presented to demonstrate the applicability of the proposed method and the results of the proposed method are compared with the dynamic analysis results. Compared with the conventional CSM, the proposed method improves the estimation of system damping and can estimate the settlement after earthquakes.