Seismic fragility assessment of existing Italian overpass bridges

Abstract This study introduces a three-dimensional refined finite element model that is suitable for dynamic analysis of existing overpass bridges with Multi-Span Simply-Supported scheme. The proposed modeling approach allows to realistically reproduce the bridge behavior under seismic loadings via a proper simulation of the expected behavior and failure modes of each bridge component, as well as their mutual interaction. Two different Limit States, as well as a definition of system-level collapse, are introduced depending on the behavior of the bridge components and the interaction between the superstructure and the substructure. The proposed modeling approach is adopted to generate Limit State fragility curves adopting a stochastic approach based on cloud analysis which entails the use of real recorded ground motions for a reference bridge, designed and constructed in southern Italy in the 1970s. The results show that the proposed simulation approach is suitable to realistically reproduce the complex behavior of this type of bridge providing significant insights into their vulnerability.