An efficient finite element model for the seismic assessment of typical Italian overpass bridges

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 enables a realistic reproduction of the bridge behaviour under seismic loadings by accurately simulating the expected response and failure modes of each bridge component, as well as their mutual interaction. Two different Limit States and a system-level collapse definition are introduced based on the behaviour of the bridge components and the interaction between the superstructure and the substructure. The effectiveness of the proposed modeling approach is demonstrated through the generation of Limit State fragility curves via a stochastic framework based on cloud analysis, which entails the use of real recorded ground motions for the reference bridge, designed and constructed in southern Italy in the 1970s. The results indicate that the proposed simulation approach is suitable to realistically reproduce the complex behaviour of this type of bridge, providing valuable insights into their vulnerability and informing the selection of optimal retrofit strategies.