Effect of Foundation Type and Compliance on Seismic Response of RC Bridges

Abstract

Foundation compliance appears to be one of the key features of the lateral load response of bridges, but it has not been seen so far as a possible solution to the problem of regularizing the response of bridges with piers of unequal height in such a way that a reasonably uniform ductility demand is achieved. The present study focuses on the effect of pile foundation stiffness on the lateral displacements and flexibility of the bridge as a whole as well as on the ductility demand of the pier itself. Conventional lumped plasticity beam models and 2D finite-element models are used for carrying out nonlinear static (pushover) analyses of alternative bridge superstructure systems. The results clearly indicate that the foundation type, the number of piles and their arrangement, and the adopted design approach affect the distribution of ductility demand. It is confirmed that control of the foundation stiffness may be a useful tool for improving the distribution of ductility demand and hence the overall performance of a bridge during strong ground motions.