Probabilistic seismic performance assessment of timber-steel hybrid structures subjected to mainshock-aftershock sequences

Abstract

Timber-steel hybrid structural system is an effective solution to expand the application of wood to mid-rise buildings. In this paper, the impact of mainshock-aftershock sequences is integrated into the probabilistic seismic demand analysis (PSDA) on timber-steel hybrid structures. A bilinear seismic demand model is adopted to develop the probabilistic seismic demand model (PSDM) for timber-steel hybrid structure considering the intensity levels of both mainshock and aftershock, and the seismic fragility surface is generated accordingly. The critical intensity is defined to quantify the condition when the aftershock damage leads to the increase of structural demand, which exhibits nonlinear trend with respect to the mainshock intensity. The PSDA result shows that choosing appropriate design parameters, such as larger wall-to-frame stiffness ratio, can reduce the seismic fragility of structures. Additionally, the joint probabilistic modeling is carried out using copula approach. It allows to predict the exceedance probability of a structure under mainshock-aftershock sequences conditioned on the mainshock damage. Results show that the Clayton copula is the best-fit copula to construct the joint probabilistic model, and larger wall-to-frame stiffness ratio is beneficial to reduce the exceedance probability of the timber-steel hybrid structures.