SENSITIVITY OF SEISMIC FRAGILITY OF REINFORCED CONCRETE GIRDER BRIDGES ON THE RESPONSE SPECTRUM MEAN AND VARIANCE OF EARTHQUAKE GROUND MOTIONS

Incremental dynamic analysis (IDA) is performed on a nonlinear model of the reinforced concrete girder bridge to investigate the vital effects of several key uncertainties, such as the mean and variance of ground motion response spectra and seismic capacities of bridge structures, on the probabilistic seismic demand assessment, engineering demand parameter (EDP) hazard curves and fragility curves of bridges in a performance-based earthquake engineering context. It is shown that response spectrum mean and variance can significantly affect the probability distributions of seismic demands and EDP hazard curves. The mean and variance of response spectra and seismic capacities both have remarkable influence on fragility curves and the significance of seismic capacities to fragility curves are more than response spectra in some situations because of larger variances than those of response spectra. Through sensitivity analysis above, some advices on the selection of ground motions for the PBEE methodology can be presented so as to more precisely evaluate seismic fragility of reinforced concrete girder bridges.