Assessment of the seismic vulnerability and modelling of existing bridge with different levels of accuracy: strengths and weaknesses

The assessment of the seismic vulnerability of existing bridges is a topic of primary relevance for the infrastructure field, as the knowledge of the vulnerability allows to design the management of the aftermath of the earthquake. To appreciate the vulnerability of the structure, different modelling approaches with different levels of accuracy are available and modern seismic design code provide recommendation about their use. The study aims at assessing the reliability of less complex methods, but with low computational cost and calibrate them against the results of nonlinear dynamic analyses in order to obtain an acceptable level of accuracy. The study will be developed considering a bridge prototype, representative of features such as the structural scheme (simply supported), the material of the piers (reinforced concrete), and the geometry of the piers (framed piers). The bridge will be analyzed first through nonlinear dynamic analyses, to define the benchmark solution. Then, the same bridges will be analyzed through linear dynamics analysis (Linear Time history and Response Spectrum) and nonlinear static analyses, such as MPA (Modal Pushover Analysis) and, in the end, through simplified Equivalent Static Analysis, and a comparison among the different modeling approaches will be proposed. Strengths and weaknesses of each model will be highlighted and discussed.