Seismic Performance of Highway Bridges with Different Transverse Unseating-Prevention Devices: Fid-Bau Portal

Seismic Performance of Highway Bridges with Different Transverse Unseating-Prevention Devices

Xiang, Nailiang / Li, Jianzhong

Typical small-to-medium–span highway bridges in China are often installed with economical laminated-rubber bearings that allow for thermal movement of girders and concrete shear keys that restrain transverse girder displacement. However, the damage investigation after the 2008 Wenchuan earthquake had shown that sliding between the girder and the laminated-rubber bearings was a common phenomenon that caused excessive girder displacement and damage to shear keys, expansion joints, and abutments. The bearing sliding can actually act as isolation for the piers, which suffered from a small amount of damage during the earthquake. Therefore, a new seismic design strategy for typical girder bridges has been proposed in which the bearing sliding acts as a fusing mechanism to mitigate the seismic demands of piers, and unseating-prevention devices are used to control the bearing displacement. This paper investigates the seismic performance of three transverse unseating-prevention devices (concrete shear keys, yielding steel dampers, and friction dampers) for a typical simply supported girder bridge. The results show that if the unseating-prevention devices are properly designed, the seismic demands of piers can be effectively reduced, and the bearing displacement can also be controlled to satisfy the performance objectives. Yielding steel dampers and friction dampers are suggested to be used in place of concrete shear keys to improve the bridge seismic performance.