Seismic Performance of Composite Rubber Bearings for Small-and-Medium-Span Bridges

Abstract:

Laminated rubber bearings are commonly used in small-and-medium-span girder bridges but they lack in displacement capacity and are likely to slide in earthquakes， which results in excessive relative displacements between piers and girders. Thus， a new type of composite rubber bearing， of which the cross section is composed of a laminated area and a sliding area， is proposed in this paper. Interior sliding is allowed to reduce the horizontal stiffness， improve the displacement capacity， and dissipate the seismic energy. Quasi-static tests were conducted for six bearing specimens to study the effects of pressures， rubber properties， and sliding area stiffness ratios on the bearing performances. Finite element analyses were performed based on a typical simply supported girder bridge. The seismic responses of composite rubber bearings and laminated rubber bearings were compared. The results show that the composite rubber bearings possess a small equivalent stiffness， strong displacement and energy dissipation capacities. Total sliding of bearings can be effectively avoided and both bearing displacements and pier moments can be significantly reduced in earthquakes.