高铁桥上线路约束作用对主梁地震响应的影响

Constraint Effect of Track Structure on Seismic Response of High Speed Railway Bridge Main Girder

目前国内高速铁路普遍采用无缝轨道,在地震作用下轨道的约束作用可能会对主梁的地震响应产生影响.本文以靠近路桥过渡端的5跨简支梁桥为依托工程,对比分析了是否设置轨道系统、是否考虑竖向地震动作用、轨道的约束程度变化等因素对主梁纵横向位移的影响.结果表明：轨道的约束作用对主梁纵横向位移有所改善,降低了主梁的位移值,其中横桥向位移的减小量达到了7%~22%,但远离路基时,这种改善作用有所减弱;轨道系统的存在不会增大竖向地震动对主梁纵横向位移的影响,在分析主梁纵横向地震响应时,依然可忽略竖向地震动,只考虑地震动沿纵、横向单向输入的工况即可;扣件刚度变化对主梁纵向位移影响很小,对横向位移会产生一定影响,随着扣件刚度的增大,横向位移有增大趋势,因此,扣件刚度的取值并非越大越好,在满足正常运营要求的前提下,应尽可能取较小值.

At present,high speed railways generally use seamless tracks in domestic. Under earthquake,track constraint may affect main girder seismic response. In this paper,research object is a 5-span simply supported girder bridge near bridge-subgrade transition. Effect of track system,vertical ground motion and constraint degree of track on longitudinal/lateral displacement of girders was analyzed. The results show that track constraint improves longitudinal/lateral displacement of main girders; especially,lateral displacement is reduced by 7% ~22% although the improvement is weakened at place away from roadbed. The existence of the rail system will not increase influence of vertical ground motion on longitudinal/lateral displacement of main girders. On the analysis of the main girder longitudinal/lateral seismic response,vertical ground motion may still be negligible,with only consideration of operation condition of ground motion along longitudinal/lateral one-way input. Fastener stiffness has little effect on main girder longitudinal displacement but somehow affects lateral displacement. With increase of fastener stiffness, lateral displacement has an increasing trend. Therefore,large value of fastener stiffness is not good. A lower value may be more desirable on the premise of requirements of normal operation.