Study on Residual Displacement of FPB bearing in Long-span Continuous Girder Bridge

Based on the principle of mechanical equilibrium, the theory of FPB with residual displacement is analyzed. This analysis derives the stiffness and equivalent damping ratio of FPB with residual displacement, and constructes the hysteretic model with residual displacement according to the existing hysteretic model of FPB. Through midas/civil modeling and analysis, the influence of different friction coefficients on the residual displacement of FPB is studied. When the friction coefficient is small, the distribution of residual displacement of FPB bearings is directional; the positive residual displacement is positively correlated with the friction coefficient, and the negative residual displacement gradually changes to the direction of seismic wave input with the increase of friction coefficient, first decreases and then increases. The positive and negative residual displacements after aftershocks are the same as those after main shocks, and their variation with friction coefficient is related to aftershocks intensity. By analyzing the hysteretic curves of different residual displacement bearings, the correctness of theoretical analysis is proved. At the same time, it is concluded that the larger the residual displacement, the more vulnerable the bearings are to instability, which leads to the failure of the main beam. The study of residual displacement can provide theoretical basis for selecting friction coefficient and controlling residual displacement in FPB design.