Effect of saddle–cable slippage on seismic performance of a multitower suspension bridge

Abstract

This study investigated the effects of saddle–cable slippage on the seismic performance of a three-tower suspension bridge. A refined friction interface was adopted to model the slippage behavior at the saddle and cable interface, which was implemented in nonlinear time-history analysis, incremental dynamic analysis, and fragility analysis. The results of the analysis indicate that compared with the fixed and single-element friction models, the refined model generates more reliable responses and captures the progressive slip propagation from the center of the saddle toward the edges. The parametric analysis shows that reducing the stiffness of the middle tower increases the displacement at the tower top and the saddle–cable slippage. Increasing the stiffness of the central buckle decreases the seismic demand of the middle tower foundation but increases the seismic demand of the side tower foundations. In addition, increasing the damping coefficient of the viscous dampers reduces the seismic responses of both the middle and side towers. The influence of traveling-wave effects cannot be ignored for long-span multitower suspension bridges because they increase the bending moment and curvature of the tower base. The fragility analysis indicates that refined saddle modeling predicts a lower damage probability for the side tower, whereas central buckles reduce the damage probability of the middle tower but increase that of the side towers, and viscous dampers reduce the damage probability of both the side and middle towers.