Damages of adjacent bridge girders due to pounding observed in Wenchuan earthquake are introduced in this paper. Based on Niulanjiang Bridge built in Yunnan province, nonlinear time history analyses are performed considering non-uniform seismic ground motion excitations, which are obtained by site seismic response analysis of the local canyon topography. And the effectiveness of cable restrainer device against unseating is studied through numerical simulations. The results show that pounding between adjacent segments of the bridge may obviously amplify the relative deformation of expansion joints, resulting in a higher probability of unseating. Cable restrainers can not only reduce the relative deformation of the expansion joints, but also mitigate the response of isolators. It also indicates that the cable restrainers can observably reduce the response of piers.