Shaking Table Tests and Numerical Studies on the Seismic Behaviors of FPB in Railway Continuous Beam Bridges

Friction pendulum bearings (FPBs) were extensively used in recent years in railway beam bridges located in the earthquake-prone regions of China. While the efficiency of FPB and reliability of constitutive models have been demonstrated by many experimental studies, the seismic behaviors of FPB in continuous beam bridges in real earthquakes have rarely been investigated. Therefore, a 1/10-scale three-span railway beam bridge isolated by FPB was tested utilizing a 10.1 m x 8.1 m shaking table with six DOFs. The seismic responses of the bridge were analyzed in terms of phenomena, displacement, acceleration, and strain. Different sliding behaviors of the FPB at each pier cap appear because of the interaction with different damaged mid piers. Obvious uplift of the girder ends occurs due to the spherical surface of the FPB, which is evidenced by the measured vertical displacement of the bearings. Numerical simulation based on OpenSees indicates that the FPB element with the suggested friction coefficient model can well reproduce the peak and residual displacements of the FPB. A comparison of calculated and measured acceleration responses reveals that both damaged piers and FPB can filter out the higher fre-quencies of the input motion. The seismic responses of bridges isolated by the FPB and flat sliding bearing (FSB) were presented based on the validated model under PGAs from 0.2 g to 1.5 g. The FPB dissipates more earth-quake energy with small peak and residual displacements, embodying better performance than that of the FSB due to the restoring capacity.