Derivation of Displacement-Based Fragility Functions for Masonry Buildings

A nonlinear static procedure is presented for the derivation of displacement-based fragility functions for seismic performance assessment of masonry buildings on regional scale. The procedure makes use of the existing displacement-based method calibrated for masonry buildings in the present research work. For a specified performance level, the method compares the displacement capacity of the structural systems with the displacement demand at the secant vibration period of the systems taking into account the energy dissipation characteristics with the expected variability in geometrical and mechanical properties of the systems in order to assess their seismic vulnerability. The displacement demand on structures is defined using random 5 % damped linear displacement response spectrum. The probability of exceeding different specified performance limit states of buildings is accessed and presented in terms of displacement-based fragility functions, which gives the probability of exceedance of different specified damage states for a given median displacement demand which is obtained from each random displacement spectrum using the median capacity parameters of the buildings. The derived fragility functions also take into account the record-to-record variability explicitly in the building capacity parameters obtained from the nonlinear dynamic analyses. The derived fragility functions can be used for the intensity-based, scenario-based and time-based (annualized losses) assessment on regional scale. The method is applied to the urban masonry building stock of Pakistan