Safety assessment in reliability terms of bridges equipped with isolator devices

The study aims to determine the seismic reliability of bridges having multi-span continuous static scheme. The proposed modelling approach is able to account for vibrational modes of the reinforced concrete piers (supposed to be elastic) and assume an infinitely rigid deck supported by the isolator devices. The interaction between the piers and the abutment have been accounted for within the investigation. The randomness of the values assumed by friction coefficient on sliding surfaces is modelled adopting normal distribution. The non-linear dependence on the sliding velocity have been appropriately considered within the model adopted for friction coefficient. The seismic inputs adopted for the analysis have been selected in order to consider record-to-record variability selecting a set of natural accelerograms. Then, the fragility curves of both the pier and isolation system supporting the deck are determined. Finally, including the site information related to seismic hazard, the seismic reliability curves are derived and discussed.