Seismic Retrofitting of Prestressed Concrete Bridges Through Friction Pendulum Isolation Bearings

This contribution presents the seismic retrofitting plan of an existing prestressed concrete bridge located in Messina, Italy. The conditions of the bridge are critical because of the insufficient lateral load resisting capacity of the existing bearings and malfunction of dampers located near the abutment. To overcome this structural deficiency, the bridge is retrofitted through the seismic isolation strategy, by placing friction pendulum bearings in place of the existing supports in between the reinforced concrete (RC) piers and the prestressed deck. Design of the isolation system and subsequent seismic assessment is performed with reference to the three-dimensional nonlinear finite element model of the bridge developed in SAP2000. Material nonlinearity is assumed in the pier behavior, by fiber hinge elements placed at the pier ends, while the bridge deck is modeled with linear elements. The analysis is carried out by means of nonlinear time-history analyses, considering natural records that are spectrum compatible with the design spectrum of the installation site. The seismic performance is assessed in terms of base shear and base moments of the RC piers, which are related to the displacements at the top of the piers.