V形近似为均匀峡谷场地的体外PC桥梁多点地震分析
Multi-support seismic analysis of externally pre-stressed bridge over the V-shaped canyon with approximate homogeneity

摘要 针对某座跨越V形峡谷场地的体外预应力桥梁，利用波函数解析解模拟得到了均匀介质V形场地地下多点地震动激励，对体外预应力体系在该激励下的结构响应进行了分析.首先，利用模型转化技术建立了4种桥梁模型，分别探究了纤维梁单元、实体单元，桩-土相互作用和人工黏弹性边界等对体系响应的影响.其次，基于均匀介质假定的V形峡谷场地解析解，引入地下多点地震动模拟方法得到了V形峡谷场地地下多点地震动并将其作为结构输入,着重探究了V形场地地震输入和水平场地地震输入对体系地震响应的影响差异.计算结果表明：V形峡谷场地激励同水平场地激励相比对结构具有更强的空间差动作用，从而引发更大的差动内力，体外预应力体系从屈服到破坏退出工作的持续时间明显缩短；桩-土相互作用对体外预应力筋的地震响应影响显著，体外筋发生屈服和破坏的时间均大幅度提前.
Abstract：The seismic response of an externally pre-stressed bridge over a V-shaped canyon with approximate homogeneity is investigated on the externally pre-stressed system induced by inputs of the simulated V-shaped canyon multi-support seismic underground motions. Firstly, four types of bridge models are established using model transformation technology. The influences of fiber beam element, solid element, pile-soil interaction and artificial visco-elastic boundary on structural response are investigated, respectively. Secondly, based on the analytical solution of the V-shaped canyon site and the simulation method for multi-support seismic underground motions, an approach for simulating multi-support underground motions is proposed and improved to obtain the seismic inputs. The differences of seismic responses induced by inputs of the V-sha ped canyon and flat terrain are studied. Results show that the V-shaped canyon topography greatly changes the composition of scattering waves of the seismic wave field, having stronger spatial differential effect than that of flat terrain seismic excitation, which leads to shorter duration time from yielding to failure. The effect of pile-soil interaction on the seismic response of externally pre-stressed tendons is significant. The occurrence time of yielding and failure of the externally pre-stressed tendon is greatly advanced.