Investigation of the Different Types of Seismic Base Isolators for a Continuous Box Girder Bridge

Bridges play a vital link role in surface transportation network, and their failures not only cause disruption of service but also jeopardize people’s life. Seismic base isolation is an important technique that is used for mitigating seismic vulnerability by decreasing the seismic demand instead of increasing the seismic capacity. Seismic isolation is essentially based on the idea of separating the support from the super-structure for the horizontal motions of the ground by placing flexible interfaces between the structure and its support. It decreases the lateral forces that act on the superstructure by shifting the fundamental period of the structure away from the predominant period of the ground motion and providing additional damping. In the base isolation strategy, at the same time it is possible to obtain a considerable reduction of large displacements attained at the base level as a consequence of the energy dissipation due to damping and hysteretic properties of isolation device. In this paper, various types of isolation devices, such as elastomeric bearings (lead rubber bearing), sliding systems (friction pendulum system) are evaluated for their performance in a continuous concrete box girder bridge. The response of the bridge system under earthquake has been compared with the corresponding bridge without the isolation system. The period and base shear of several base isolation systems are changed, it indicates that the period of a structure increases when base isolators are utilized in the structure.