地震动扭转分量对大跨度斜拉桥易损性影响

Because it is difficult to obtain the rotational component of ground motion by using existing methods, the influence of rotational component on the seismic response of long-span bridges is often neglected in current researches. However, due to the long period and large span of long-span Bridges, they are prone to torsion failure. The existing researches are very scarce in this respect. In order to study the seismic response of long-span bridges under the rotational ground motion. a finite element model for one cable-stayed bridge considering the uncertainty of material parameters by using normal distribution Latin hypercube sampling method was built. 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 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 show that the damage probability of the key components of the bridge would be significantly changeed when the rotational ground motion is considered. The increase of the damage probability for the bridge is closely related to the bridge component type and damage direction. When the rotational ground motion is considered, the tower is the most vulnerable component. 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 will be slightly reduced when the rotational ground motion is considered. However, for the deck and its longitudinal restraint members, the damage probability of these members will be slightly reduced when the rotational ground motion is considered.