近断层地震方向脉冲效应对高速铁路桥梁弹塑性反应的影响

基于PEER-NAG强震数据库，采用ANSYS分析软件、ANSYS-APDL语言和弯矩曲率关系计算程序，以高速铁路多跨简支梁桥为研究对象，建立了近断层脉冲型地震作用下的高速铁路桥梁全桥模型，考虑了轨道不平顺的影响，分析了结构的自振特性，计算了近/远断层地震作用下桥梁的弹塑性地震响应。计算结果表明，近断层方向脉冲型地震作用下的墩底的荷载-变形曲线呈现中间加强的特点，此时需要桥墩有更强的能量释放能力和较好的延性要求，相比远断层地震而言，近断层方向脉冲型地震作用下墩底梁体位移、墩顶位移以及墩底弯矩增大，且导致更大的塑形变形；远断层地震趋向于能量的逐渐释放过程并与较少的滞回环损伤疲劳相联系；由于近断层地震动方向脉冲效应的影响，在一些地震动的某些时段内，对结构破坏起控制作用的因素是速度或位移而不是峰值加速度；由于近断层地震较大的竖向地震动，导致梁体竖向挠度比远断层地震增加较多，《铁路工程抗震设计规范》等取竖向地震为横向的2/3左右，会导致竖向动力响应偏小，建议取竖向地震动的合理范围进行计算较为妥当。

Effects of to Near-Fault Directivity Pulse -like Ground Motion on Elastic-Plastic Seismic Response of High-speed Railway Bridge

Based on the PEER-NAG Strong Ground Motion Database, the finite element model of the multi-span simply supported bridge is set up by means of ANSYS software, ANSYS-APDL language and moment-curvature program in the paper, the natural vibration properties of structure is analyzed, the elastic-plastic seismic responses of bridge subjected to the near/far-fault ground motions are calculated. The calculation results show that, for the hysteretic characteristics of the near-fault directivity pulse-like earthquake, the more just expression should be the moment-rotation relationship of pier bottom is characterized by the central strengthened hysteretic cycles at some point of the loading time-history curve corresponding to the time of the pulse, it require the bridge piers to dissipate considerable input energy in a single or relatively few plastic cycles, it is mean that the ductility capacity of the piers should be improved; the displacement of girder and pier top, moment of the pier bottom increase under near fault ground motion compared with far-fault ground motion; the energy dissipation on the bridge system subjected to a far-fault motion tends to gradually increase over a longer duration, causing an incremental build-up of input energy; as the greater vertical earthquake action of the near-fault earthquake, there are the large vertical deflection in the mid-span of girder; GB 50111-2006 Code for seismic design of railway engineering specify that the vertical earthquake force can be taken as 67% of the lateral earthquake, it's advisable that the reasonable value of vertical earthquake acceleration should be utilized to carried simulation calculation.