Bridges With Simply Supported Decks: a Simplified Vulnerability Assessment

Abstract eng:
The paper proposes a simplified procedure for the seismic vulnerability analysis of bridges with simply supported decks and single solid circular piers. The proposed method can be applied to the structural typology for which the seismic response of the whole bridge depends from the critical pier. For an assigned limit state, the procedure determines a general form of the capacity curve that is approximately calculated for equivalent system (SDoF) of the critical pier as a function of 3 parameters (elastic stiffness, displacement at yielding, displacement at collapse). Starting from the behaviour under combined axial and flexural stress, the method taking then into account the different possible collapse modes (shear failure; lap splice failure of the longitudinal bars; buckling) and the geometric non linearity. A N2-like procedure is then applied in order to identify the “Capacity Return Period”, which represents the performance level, to be compared with the design spectrum. A significant numerical example is presented in which the traditional FEM solution is compared with the proposed simplified procedure. The basic idea of the procedure is that, by only knowing few information usually contained in the regional archives (general geometry, sections, year of construction) it will be possible to assess the infrastructures of a vast territory, providing priority lists in terms of capacity level and cost of retrofitting.

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