Partially restrained seismic isolation system to retrofit a continuous girder RC bridge

Abstract

The present paper proposes a partially restrained seismic isolation (PRSI) system to retrofit existing continuous girder reinforced concrete (RC) bridges. It involves a pure-friction system with a self-centring force provided by the stiffness of the deck and the frictional forces generated at the area of contact acting as an energy dissipation mechanism. The advantage is that the very small height of the system allows its application to existing bridges. The dynamic response until the collapse of an existing bridge subjected to seismic accelerations was assessed through a detailed 3D numerical model. This numerical model employed an explicit integration scheme that avoids numerical convergence drawbacks as a result of the strength and stiffness degradation of concrete structures. It was able to identify collapse mechanisms such as the development of cracks in the concrete elements. The seismic response of the original bridge was compared with that resulting from structural rehabilitation through implementation of a P-F type isolator in combination with the PRSI technique, which provided the system with a restitutive mechanism minimizing residual deformations. In addition, a classic structural reinforcement was incorporated by means of steel jacketing of the column. Both structural rehabilitation strategies were compared under the same seismic actions, assessing their efficiency and highlighting their benefits.