青藏铁路多年冻土区桥梁地基融化时的抗震安全性分析

采用弹簧单元模拟地基对桥梁基础的嵌固以及轨道桥面系对梁体的纵向约束作用,建立桥梁-轨道桥面-地基共同受力的全桥整体模型。分析了未来青藏高原由于气候变暖引起冻土退化、地基对桥梁桩基嵌固作用降低时桥梁结构的地震反应。结果表明,当冻土退化而导致地基嵌固作用降低时,桥梁墩身的地震弯矩减小,桩身弯矩和墩顶位移增大。轨道桥面系的约束作用使得边跨桥墩的地震反应降低,中间桥墩的地震反应增加。还探讨了桥墩高度、桥梁长度对地震反应的影响。

Effect of Climate Getting Warmer on the Seismic Safety Performance of Qinghai-Tibet Railway Bridges in the Perennial Frozen Soil Region

The spring elements are adopted to simulate the link between the bridge foundation and soil, and the longitudinal restraint of tracks on the superstructure of bridges. The tract-bridge-soil model is developed for the whole system analysis. The effect of such factors, as the frozen soil degradation, the soft effect of restraints of soil to bridge foundation, on the safety and seismic response of railway bridges are considered and simulated. The numerical results indicate that the frozen soil degradation can reduce the bending moment of the bridge piers, but this could magnify the bending moment of pile shafts and the deformation of the pier top; the track restraints on the bridge may decrease the seismic response of the piers of the edge-span, but increase the response of the piers of the mid-span. In addition, some key factors on the seismic response of bridges, such as the height of the piers and the total span number, are also discussed.