大跨桥上无缝线路纵向地震响应研究

Research on Longitudinal Seismic Responses of Continuous Welded Rails on Large-span Bridges

地震作用下大跨桥上无缝线路纵向响应的研究具有重要意义。以一座大跨桥梁为例,研究了一致激励下桥上无缝线路纵向地震响应,并对小阻力扣件铺设、梁体温差及地震波频谱特性对钢轨最大纵向力的影响进行了分析。得出结论：轨道约束对大跨桥梁结构的低阶纵向自振频率有较大的影响;地震作用下梁缝处钢轨最大纵向力比根据现有规范计算的钢轨最大伸缩力大很多,铁路工程相关规范应增加钢轨地震力检算这一指标;大跨桥上铺设小阻力扣件后,地震时钢轨最大纵向力会降低约20%～30%;穿越震区的大跨桥上无缝线路设计应合理考虑梁体温差的影响,并使桥梁结构低阶纵向自振频率有效避开场地处地震波的主频率段,否则地震发生时桥上无缝线路工作状态将会受到较大考验。

Study on longitudinal seismic responses of CWRsCcontinuous welded rails） on large-span bridges is of great significance.Taking one large-span bridge as an example,longitudinal seismic responses of CWRs under uniform excitation were studied.Influence of laying of small resistance fasteners,beam temperature differences and seismic wave spectrum characteristics on the maximum CWRs longitudinal force was analysed.Results show as follows;Rail restraints have great influence on the low-order longitudinal natural frequencies of the large-span bridge structure;the maximum rail forces at beam joints under the action of earthquake motion are much larger than the maximum expansion forces calculated according to the current specifications,so the index of rail seismic force is suggested to be added to the related railway engineering specifications;in the case that small resistance fasteners are installed on large-span bridges,the maximum rail force will be decreased by 20%～30%in earthquake;CWRs design for large-span bridges located across earthquake zones should take beam temperature differences into rational consideration,and the low-order longitudinal natural frequencies of the bridge structures should be designed to avoid the main frequency bands of seismic waves on site,otherwise the working status of CWRs will be subjected to severe tests when in case of earthquake.