Abstract:To study the seismic response of long-span bridges under the rotational ground motion, based on OpenSees, fifteen finite element models was built for one cable-stayed bridge considering the uncertainty of earthquake intensity and material parameters by using normal distribution Latin hypercube sampling method. A total of 15 groups of near-fault pulse ground motions were selected from the PEER ground motion database. Then, the rotational components of the ground motions were obtained from the seismic translational components based on the elastic wave theory. The dynamic response of the bridge was obtained through nonlinear dynamic time -history analysis. The damage indexes for the bridge components were proposed. The seismic fragility curves for the key components of the bridge were drawn based on the probabilistic demand analysis method. The results showed that the damage probability of the key components of the bridge would be significantly changed when the rotational ground motion was considered. The increase of the bridge damage probability was closely related to the bridge component type and damage direction. When the rotational ground motion was considered, the middle section of the tower has the highest sensitivity to the torsion component of ground motion. The damage probability of the tower under the ground motions with rotational component would be increased as much as 22.12% compared with that without considering rotational ground motion. The rotational ground motion also had a higher destructive effect on the bottom section of the tower and the bottom section of the side pier (in bridge transverse direction), with a damage probability increase of 17.33% and 19.45%, respectively. However, for the deck and its longitudinal restraint members, the damage probability of these members would be slightly reduced when the rotational ground motion was considered.