强震下斜交桥地震反应与减隔震性能分析

针对斜交桥在破坏性地震中发生破坏和损伤的突出问题,采用铅芯橡胶支座(LRB)进行隔震和滞回耗能。基于OpenSees平台建立了不同斜度的传统非隔震和全桥采用LRB隔震的4跨斜交连续梁桥动力分析模型,沿2个水平方向输入远场地震动和具有向前方向性效应、滑冲效应以及无速度脉冲效应的近断层地震动,并进行非线性时程计算,研究桥墩和挡块的损伤状态、主梁旋转度、碰撞力与斜交桥斜度的关系以及LRB对斜交桥抗震性能的影响。结果表明:向前方向性效应和滑冲效应的脉冲型地震动作用下的斜交桥地震反应和损伤明显大于无速度脉冲近断层和远场地震动作用; 采用LRB隔震后,明显降低了固定墩的地震损伤,桥墩位移减震率可达到50%以上; LRB隔震桥主梁与挡块的间隙宜结合桥梁的地震风险和设计位移进行确定。

Analysis of seismic response and isolation performance of skew bridge under strong ground motions

According to the prominent problem that the skew bridge will be damaged under destructive earthquake. Selecte the lead-rubber bearing(LRB)as the isolation device to seismic isolation and hysteretic energy dissipation. Based on OpenSees platform, the dynamic analysis models of traditional non-isolated and LRB isolated 4-span skew continuous beam bridges with different slope are established. The far field ground motion and near fault ground motion with forward directivity effect, fling step effect and no velocity pulse effect are input along two horizontal directions. And then the dynamic time-history analysis is carried out to study the the relationship between damage state of skew bridge, the rotation of main girder, collision force and slope. The influence of LRB on the seismic performance of skew bridge is also studied. The results show that the seismic response and damage of skew continuous girder bridge under the action of near-fault ground motions with the effects of forward directivity or fling step are obviously larger than those under the action of near-fault ground motions without velocity pulse and far-field motions, the seismic damage of the fixed piers is obviously reduced if LRBs are adopted, and the pier displacement damping rate can reach more than 50%. The gap between the main girder and the shear keys of the LRB seismic isolation bridge should be determined in accordance with the seismic risk and design displacement of the bridge.