Seismic reliability analysis of isolated deck bridges using friction pendulum devices

In this study, the seismic reliability of multi-span continuous deck bridges equipped with isolation friction pendulum (FP) devices is investigated. The relevant aleatory uncertainties associated to the sliding friction coefficient of the FP isolators and to the seismic inputs are considered. A six-degree-of-freedom model is established to reproduce the elastic behavior of the reinforced concrete (RC) pier, the stiff response of the deck supported by the isolation devices and the non-linear response of the FPS bearings which depends on the sliding velocity. Moreover, the RC abutment is assumed as infinitely rigid. For what concerns the seismic inputs, a group of natural seismic records having various characteristics is adopted and properly scaled to increasing levels of intensity. The random variability of the friction coefficient is modelled by suitable probabilistic distribution. Then, considering several bridges and isolator configurations, the fragility curves of the RC pier and of the isolator devices (FP) are determined. Finally, in agreement with the hazard curve of the specific site, the convolution integral is adopted to determine the seismic reliability curves in the performance domain.