列车动荷载对下立交结构的影响分析

通过弹塑性动力有限元法对列车动荷载与轨下结构组成的系统进行了动力响应分析，研究了轨下有较大刚度结构存在时对路基内竖向动应力的变化规律的影响，并对不同埋深隧道的附加动应力进行了讨论。分析中采用轨枕-道床全支承模式，土体采用理想弹塑性动本构模型。结果表明轨下构筑物的存在将减弱列车动应力往深层传递的衰减。隧道埋深越大，路基内附加动应力整体水平越低，对轨下结构的影响越小。建议在设计时考虑长期列车动荷载对混凝土的疲劳破坏。

EFFECT ANALYSIS OF TRAIN-INDUCED DYNAMIC LOAD ON OVERHEAD CROSSING STRUCTURE UNDER RAILWAY

The dynamic response of the system composed of rail wheel,rail and tunnel under railway is analyzed with elastoplastic finite element method. The influence of the structure under rail with bigger stiffness on variation regularity of vertical dynamic stress in roadbed is studied. The additional dynamic stresses of tunnels with different depths are also discussed. The ideal touch model between tie and bed and the ideal elastoplastic dynamic model of soil are adopted for analysis. The analysis results indicate that the attenuation of additional dynamic stress along depth is reduced with existence of the structure under rail. The deeper the tunnel is,the lower the whole level of dynamic stresses in roadbed is and the smaller the influence on tunnel is. In addition,the fatigue failure of concrete due to long-term train-induced dynamic load should be considered in design.