温度和列车动荷载作用下双块式无砟轨道道床板损伤特性研究

Research on the Damage Characteristics of Double-Block Ballastless Track Bed Slab under Temperature and Vehicle Dynamic Loads

采用混凝土损伤塑性模型描述双块式无砟轨道道床板的力学行为,以变温作用下道床板最大损伤状态作为初始条件、车辆—双块式轨道耦合动力分析得到的各钢轨支点压力作为轨道—路基的外部激励,进行变温和列车动荷载共同作用下道床板损伤的演变规律及道床板损伤对结构受力影响的研究。结果表明:在降温过程中道床板会发生横向弯曲变形,产生损伤,导致受拉承载力下降;在升温过程中由于降温导致的道床板拉伸损伤不可恢复,所以道床板损伤值不变,最终保持在0.23左右,但刚度出现恢复现象;车辆经过已损伤的道床板时,道床板内部裂纹交替张开与闭合,刚度出现短暂的部分恢复阶段,刚度退化系数最大幅值为0.057,而道床板损伤值不变,且道床板的位移和加速度幅值、支承层与基床表面的动应力幅值均比无损伤时增大,拉应力幅值减小;损伤塑性模型能很好地反映道床板混凝土的软化及刚度退化行为。

The concrete damaged plasticity model was adopted to describe the mechanical characteristics of double-block ballastless track bed slab.Setting the maximum damaged state of track bed slab under changing temperature as the initial condition and taking the rail supporting force obtained by vehicle-double-block ballastless track coupled dynamic simulation as an external excitation of track-subgrade structures,the damage evolution law of track bed slab and the influence of track bed slab on the mechanical behavior of structure were analyzed under the joint action of changing temperature and vehicle dynamic load.Results show that the track bed slab presents lateral bending deformation and produces damage which weakens the tensile capacity in temperature dropping process.While in the temperature rising process,the damage value of track bed slab remains unchanged and keeps around 0.23 due to the tension damage produced by temperature dropping is unrecoverable,but the elastic stiffness of track bed slab appears recovery phenomenon.As vehicle passes through the damaged track bed slab,the internal cracks of track bed slab take on open or closed alternatively.The elastic stiffness is partly recovered for a short time and the maximum amplitude of stiffness degradation factor is 0.057,while the damage value of track bed slab remains unchanged.The dynamic amplitude including displacement and acceleration of track bed slab,the dynamic stress of supporting layer and the surface of foundation bed are all increased,but the tensile stress is decreased,compared with the results of undamaged condition.The damaged plasticity model can well represent the softening and stiffness degradation behavior of concrete of track bed slab.