An inertial macro-element of abutments for nonlinear analysis of bridges

With the aim to include the seismic response of the abutments into the global structural analysis of a bridge, this paper describes a new macro-element of the soil-abutment system. The model is conceived to reproduce the multi-axial force-displacement relationship at the deck-abutment contact, accounting for the frequency-dependent inertial effects and the nonlinear behaviour of the geotechnical system, keeping at the same time a high computational efficiency. The formulation of the macro-element was coded as a new finite element in the analysis framework OpenSEES. A calibration procedure of the proposed model was devised, based on the results of nonlinear static and dynamic analyses on a reference soilabutment system implemented in OpenSEES.