Numerical evaluation of the modal characteristics of a bridge abutment

The seismic analysis of bridges needs to account for the effects of soil-structure interaction with methods that strike a reasonable balance between completeness and reliability of the numerical soil-structure interaction models. In view of this, focusing on the marked influence that the behaviour of the abutments can have on the seismic performance of the whole bridge, this study presents an identification procedure of the dynamic response bridge abutments. Based on the results of dynamic simulations on a reference local model of a bridge abutment carried out in the analysis framework OpenSees, the modal characteristics of the soil-abutment system are computed and are used to evidence the role played by the soil interacting with the abutment in controlling the overall dynamic response of the system. This role is quantified through the definition of the mass participation factors for different directions of motion.