Non-linear 3D seismic analysis of a RC bridge and retrofit alternatives with passive protective systems

Abstract

Abstract In this paper a proposal of a partially restrained seismic isolation (PRSI) system is presented for the retrofit of existing continuous girder RC bridges. A pure-friction system is used with auto centring force provided by the stiffness of the deck and the frictional forces generated at the contact acting as an energy dissipation mechanism. The proposal has the advantage that the very small height of the system allows its application to existing bridges. In order to study the proposed system, the dynamic response until collapse of an existing bridge subjected to seismic accelerations is assessed through a detailed 3D nonlinear numerical model. An explicit integration scheme is employed that avoids numerical convergence drawbacks due to strength and stiffness degradation of concrete structures. The numerical model identifies the collapse mechanisms, such as the development of cracks in the concrete elements. Two retrofit systems are studied: a) steel jacketing reinforcement and b) PRSI proposal. The efficiency of each alternative is evaluated in terms of displacements and shear forces.