CA砂浆脱空对桥上单元板式轨道动力特性的影响研究

Influence of CA Mortar Void on Dynamic Characteristics of Unit Slab Track on Bridge

砂浆脱空是单元板式无砟轨道主要伤损型式之一。基于轮轨系统动力学基本原理,采用有限元方法,建立列车—轨道—桥梁垂向非线性耦合振动平面模型,运用显式中心差分法,借助动力分析软件LS-DYNA编制求解系统动力响应的计算程序。用武广高铁试验数据对其可靠性进行验证后,应用该模型和程序计算和分析不同脱空情况条件下车辆和轨道结构的动力响应。结果表明:砂浆脱空对轨道结构振动的影响显著,砂浆垂向动压应力和扣件上拔力随着脱空长度的增长明显增大;当脱空长度超过0.8m时,由脱空引起的轨道动态不平顺对轮轨相互作用起主导作用,各种动力响应明显加剧;板缝两侧轨道板端部均脱空对轨道平顺性和砂浆压应力最不利,一块轨道板两端同时脱空对扣件受力最不利。可见砂浆脱空长度不宜超过0.8m。

Mortar void is one of the main damage types in unit slab track.Based on the basic principles of wheel-rail system dynamics,a vertical nonlinear coupling vibration plane model of vehicle-track-bridge system was built up by finite element method.The dynamic responses of the system were solved by explicit central difference method and the relational calculation programs were compiled by means of LS-DYNA.The correctness of the programs has been verified by the test data of Wuhan-Guangzhou high-speed railway,and the dynamic responses of vehicles and track structures under different void conditions were analyzed with these programs and the model.The results show that mortar void has a significant impact on the vibration of track structure.The vertical dynamic compressive stress of mortar and the uplift forces of fasteners increase obviously with the growth of void length.When void length exceeds 0.8 m,the rail dynamic irregularity caused by void plays the leading role in wheel-rail interaction,and all kinds of dynamic responses are significantly increased.The voids on both sides of the slab gap are the most unfavorable to track regularity and the dynamic compressive stress of mortar.The voids on both ends of one slab track at the same time are the most unfavorable to the uplift force of fastener.It is suggested that the void length of mortar should not exceed 0.8 m.