A macro-element approach to analyse bridge abutments accounting for the dynamic behaviour of the superstructure

This paper describes an original approach to the study of the seismic behaviour of bridge abutments. The proposed method incorporates a simplified description of the dynamic response of the bridge structure into a finite-element model of the soil-abutment system. Specifically, the dynamic behaviour of the bridge structure is described by a macro-element that simulates the loads transferred to the abutment during the seismic event. The macro-element is identified using a structural model of the bridge as a reference. This approach improves the current analysis methods based on sub-structuring, limiting at the same time the computational demand needed for a complete study of the soil-structure interaction. In the paper, the validity of the procedure is demonstrated comparing the results of the simplified approach with the results obtained from full three-dimensional dynamic analyses of idealised soil-bridge systems, using nonlinear advanced constitutive models to describe the soil behaviour. Based on these results, a strategy is devised for the calibration of the bridge macro-element, making use of a limited number of input parameters.