Seismic reliability assessment of base-isolated bridges in Quebec

Abstract

The aim of this work is to estimate the seismic reliability of a simple typical two-span lifeline base-isolated bridge designed to behave essentially elastic or as per the Canadian Highway Bridge Design Code, for seven localities in Quebec. Two limit states are considered for possible failure due to unacceptable damage: flexure at the pier-base and displacement within the seismic isolation systems (SIS). The main problem random variables considered and modeled are seismic hazard, temperature, pier base dimensions, and material mechanical properties. The Monte Carlo method was used to evaluate the probability of failure and the reliability of each limit state. Preliminary results reveal that notwithstanding the large temperature and seismic hazard variabilities between the seven sites in Quebec, the global bridge reliability indices are almost uniform, approximately 3.45 ± 0.02. Furthermore, the security factor (i.e., 1.25) on the SIS displacement capacity results in reliability indices for SIS displacement that are not levelled with the flexural reliability indices and requires further examination and consideration.