Shake table studies of a highway bridge model by allowing the sliding of laminated-rubber bearings with and without restraining devices

One of the most significant damages for highway bridges during the 2008 Wenchuan earthquake was the sliding of laminated-rubber bearings. The bearing sliding during the earthquake caused excessive superstructure displacement, which subsequently led to the failure of concrete shear keys, damages of abutments and expansion joints, and even span collapse. The main objective of this study is to experimentally investigate the seismic performance of highway bridges considering the sliding of laminated-rubber bearings. Three transverse restraining systems, namely without restraining devices, with concrete shear keys and with yielding steel dampers were tested on the shake table. Test results validate that seismic forces transmitted from superstructure to substructure can be substantially reduced by allowing the bearing sliding. However, if no restraining devices are implemented, the maximum, as well as residual bearing displacements, will be excessively large, making the superstructure-to-substructure connections the most vulnerable components. As restraining devices, yielding steel dampers are more effective than concrete shear keys by withstanding larger earthquakes and dissipating more energy. The tested model equipped with steel dampers can achieve a reasonable balance between bearing displacements and substructure seismic demands. Further, the experimental results are captured and justified by the supplemental numerical simulations.