Experimental evaluation of the seismic isolation effectiveness of friction pendulum bearings in bridges considering transverse poundings

Most previous studies investigating how transverse poundings at shear keys affect the seismic behavior of bridges were conducted numerically. Few laboratory investigations were reported, especially for isolated bridges. This study investigates the effect of transverse poundings on a bridge isolated by friction pendulum bearings (FPB) using 1:6 large-scale shake table tests. To evaluate the seismic isolation effectiveness of FPB in the cases of no pounding and pounding, bridges with ordinary spherical steel bearings (SSB) are also tested and regarded as reference cases. Results indicate that FPB has a better ability to reduce the acceleration of girder and the bending moment at pier base than SSB in the case of no pounding. However, poundings significantly increase the seismic forces developed in the bridge super- and substructure, especially for the bridge using FPB, which would considerably reduce the isolation effectiveness. The findings highlight the importance of considering transverse poundings when designing an isolated bridge.