Effect of epsilon-based record selection on fragility curves of typical irregular steel frames with concrete shear walls in Mashhad city

In this paper, the seismic vulnerability of Mashhad city, as the second largest city in Iran, has been investigated using analytical fragility curves. Disaggregation analysis is first performed in order to identify the target epsilon at different hazard levels. The disaggregation results revealed different epsilon values at the first mode period of two representative structures, in the case of 72-, 475-, and 2,475-year return periods. Nonlinear incremental dynamic analyses are then performed for two representative models of a typical steel frame with a concrete shear wall, using independent suites of acceleration time histories that are selected based on the target epsilons. Structural limit states are defined on each incremental dynamic analysis curve, and the corresponding damage measures are estimated. The results show that if ϵ is neglected in the considered simulations, then the predicted median structural capacities is decreased by around 10%, 15%, and 18%, respectively, for the three abovementioned hazard levels.