Seismic assessment of isolated bridges with abutment transverse restraint

This paper proposes an analytical model and formulation for predicting the seismic response of isolated bridges with abutment transverse restraint. These are a particular class of multi span continuous bridges in which isolation bearings are provided only between the piers top and the deck whereas seismic stoppers restrain the transverse motion of the deck at the abutments. The bridges are modelled by two dimensional simply supported beams with intermediate visco elastic restraints, whose properties are calibrated to describe the substructures behaviour. First, the application of the complex mode superposition method to the specific class of bridges analyzed is illustrated, with the aim of deriving an exact benchmark solution to the seismic problem. Then, two simplified models useful for preliminary analysis and design are proposed. The reliability of the simplified models is assessed by comparing the approximate results of the seismic analysis of realistic PRSI bridges with the refined results involving the use of the complex mode superposition method.