Fragility curves are useful tools for evaluating the probability of structural damage due to earthquakes as a function of ground motion indices. The force reduction factor (R) is one of the seismic design parameters that determine the nonlinear performance of building structures during strong earthquakes. R factor itself is mostly a function of displacement ductility (µ), natural period of a structure, and soil conditions. A statistical method (Path Analysis) is proposed for the first time to determine the effect of R, µ and T on the column fragility curve parameters of typical box girder, two spans reinforced concrete highway bridge class. An analytical approach was adopted to develop the fragility curves based on numerical simulation. The R, µ and fundamental period T have been used to characterize different bridge configurations. The total, direct, and indirect effects of the variables as having significant effect on fragility curve parameters were identified.
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