Seismic Fragility of Medium-Rise Soft Story SMRF Building Under Near Field, Fling Step, and Far Field Excitations

Medium-rise soft story special moment resisting frame (SMRF) buildings can be found in many active seismic regions worldwide. This paper assesses seismic vulnerability of medium rise soft story SMRF building from a highly active seismic region under near field, fling step, far field, and mixed strong motion excitations. Fragility functions are derived for peak ground acceleration (PGA), peak ground velocity (PGV), and spectral acceleration (Sa) as intensity measures (IM) to identify possible anomalies in the selection of IMs while performing seismic vulnerability analyses. The results highlight that the fragility functions derived using mixed strong motion yield conservative estimate of exceedance probability for higher damage states in the near field regions. Moreover, at the considered maximum PGA (0.4 g) for many cities in Nepal, a seismically very active region in the world, most of the medium-rise soft story SMRF buildings would be unoccupiable due to the occurrence of extensive or collapse damage states under near field or fling step excitations.