A Keyhani - Assistant Professor, Civil Engineering Department, Shahroord University of Technology, I.R.Iran
M. Darbanian - Faculty of Civil Engineering, IAU, Shahrood Branch, Civil Department I.R.Iran
R. Darbanian - Graduated MSc, Civil Department, KNTU, I.R.Iran,
E Khojastehfar - Graduated PhD, Civil Department, KNTU, I.R.Iran

Evaluation of seismic performance of main-shock damaged structures, affected by aftershocks, leads to more accurate and reliable seismic loss estimation. Seismic fragility curves, as a measure of seismic performance, are estimated by nonlinear time history analysis of structural models against earthquake acceleration records. The modeling assumptions will affect the results of seismic performance measures. In this paper the effects of modeling assumptions on seismic fragility curves are investigated. Lumped plasticity of steel beams by deteriorating rotational springs as beam to column connections and distributed plasticity of steel beams by fiber elements are considered as modelling assumptions. Seismic fragility curves for two models, affected by main shocks and aftershocks are developed and compared for structural damage states defined by HAZUS. Aftershock fragility curves are achieved based on back-to-back dynamic analysis of two models.

Aftershock fragility curves, back-to- back dynamic analysis, Modelling assumptions, Modified Ibarra-Krawinkler connection model, Fiber element model, IDA