MSA-based seismic fragility analysis of RC structures considering soil nonlinearity effects and time histories compatible to uniform hazard spectra

In the present study, an updated ground motion simulation framework based on spectral compatible time histories is proposed for the evaluation of seismic performance of mid-rise reinforced concrete structures with multistripe analysis (MSA) based probabilistic seismic hazard analysis. The seismic fragility functions are generated for two numbers of three storied instrumented test buildings of which one is founded on individual flexible footings and other one is a base isolated building. The fragility analysis is carried out for different performance levels under a series of input ground motions (IGMs) by considering uncertainty in soil structure interaction and uncertainty in ground motion. IGMs are obtained from the uniform hazard response spectrum (UHRS) with different return period thus conserving the frequency content of input motion during the scaling of high intensity earthquakes. The UHRS compatible synthetic time histories are applied at rock level and amplified surface motion obtained from soil amplification studies considering soil nonlinearity are applied to the buildings supported on soil springs. Nonlinear time history analysis is performed by modelling hysteretic characteristic of columns using modified Takeda model. The fragility curves obtained from the proposed methodology are compared with that using simple scaling of accelerograms generally performed in literature. The proposed technique gives conservative result for structure with individual flexible footings while no marked differences are observed for base isolated structure.