高频列车荷载作用下板式无砟轨道垂向应力衰减特性

Vertical Stress Attenuation Characteristics of Slab Ballastless Track Under High⁃frequency Train Load

为了优化无砟轨道结构设计并为确定动力系数取值提供参考,以CRTSⅠ型板式无砟轨道为研究对象,采用LS-DYNA软件建立车辆-轨道耦合动力学模型,分析了不同速度级时车轮扁疤和焊缝激励下的轮轨垂向力时频特征,阐明了轮轨垂向力随车速的变化规律;进而分析了轨道结构垂向应力沿深度的变化规律,计算了轨道结构动力系数并揭示了动力系数沿轨道结构深度的变化规律。结果表明:车速在400 km/h内,车轮扁疤不平顺作用下轮轨垂向力主频大于500 Hz,而焊缝不平顺作用下轮轨垂向力存在两个主频,较高的主频大于500 Hz,较低的主频处于(49.9±10)Hz内;高频列车荷载下的轨道垂向应力沿着轨道结构深度衰减明显,轨道板底部的垂向应力约为轨道板顶部的15%,底座板底部的垂向应力约为轨道板顶部的4%;轨道结构动力系数沿轨道结构深度显著降低,在钢轨至轨道板之间衰减约40%,底座板底部动力系数比钢轨上减小约50%。建议适当降低高频列车荷载作用下无砟轨道设计和检算动力系数。

In order to optimize the design of ballastless track structure and provide reference for determining the values of dynamic coefficients,CRTSⅠslab ballastless track was taken as the research object.LS-DYNA software was used to establish a vehicle-track coupling dynamic model,analyze the time-frequency characteristics of wheel-rail vertical force under wheel tread and weld seam excitation at different speed levels,and clarify the variation law of wheel-rail vertical force with vehicle speed.Furthermore,the variation law of vertical stress along the depth of the track structure was analyzed,and the dynamic coefficient of the track structure was calculated,revealing the variation laws of the dynamic coefficient along the depth of the track structure.The results show that within a speed of 400 km/h,the main frequency of the vertical force between the wheel and rail under the action of uneven wheel tread is greater than 500 Hz.While under the action of uneven weld seams,there are two main frequencies of the vertical force between the wheel and rail,where the higher main frequency is greater than 500 Hz,and the lower main frequency is within(49.9±10)Hz.The vertical stress of the track under high-frequency train load decays significantly along the depth of the track structure.The vertical stress at the bottom of the track slab is about 15%of that at the top of the track slab,and the vertical stress at the bottom of the base slab is about 4%of that at the top of the track slab.The dynamic coefficient of the track structure significantly decreases along the depth of the track structure,with a decay of about 40%between the steel rail and the track slab and a decrease of about 50%in the dynamic coefficient at the bottom of the base slab compared to the steel rail.It is suggested to appropriately reduce the design and calculation dynamic coefficients of ballastless tracks under high-frequency train loads.