SEISMIC ANALYSIS OF BRIDGES CONSIDERING FOUNDATION STRUCTURE INTERACTION

Abstract

The response of an embedded structure like pier well foundation of a bridge is greatly influenced by the dynamic soil properties of the surrounding medium. Therefore any analytical solution of the coupled problem of soil and structure demands due consideration of the interaction effect. In continuum approach of the soil-structure inter-action analysis the flexibility of foundation is replaced by horizontal and rotational spring-dashpot system called impe-dances. The impedance system may be either frequency dependent or frequency independent. In the present work, three frequency independent soil springs as forwarded by Fseredugo-Novak, Kausel and Parmelee are used in dynamic analysis following transfer-matrix approach. A comparative study among the three springs is made in view of time period, shear, moment, equivalent damping and deflection. For the numerical study purpose four bridges situated in seismic zone V in India are select- ed. Three of them are simply supported and the fourth is a cantilever hammer head bridge. The simply supported bridges are analysed in both loxgitudinal and transverse directions whereas the cantilever bridge is analysed in transverse direction only. For all the bridges different embedments are considered...