Probabilistic Displacement-based Seismic Design of Highway Bridges for Australia

Abstract

Despite the low seismicity of the Australian continent, it is acknowledged as not completely free from seismic hazard. Therefore, to mitigate the seismic risk to our society and environment, provisions are required for seismic design of structures and infrastructure. In regard to this, the Australian standard for the seismic design of bridges has recently been revised in which a new displacement-based method (DBM) was included in the 2014 version of this code. This DBM is anticipated to result in a cost effective solution for performance-based seismic design of structures in Australia. In this study, the efficiency of this DBM for the estimation of the seismic demand over bridge piers is investigated through comparison with a probabilistic method. For this purpose, an analytical model of a typical highway bridge was built in the OpenSees computer software. Subsequently, the earthquake loads were simulated by performing incremental dynamic analysis (IDA) based on a suite of synthetic accelerograms. The results revealed that practising the DBM suggested by the Australian standard would largely over-estimate the seismic demand, due to the prescribed deterministic displacement spectra, while the probabilistic approach which is suggested in this study will permit the designers to avoid this over-estimation.