自密实混凝土性能劣化对CRTS Ⅲ型板式轨道荷载效应的影响

Influence of performance deterioration of self-compacting concrete on the load effect of CRTSⅢ slab track

充填层是CRTS Ⅲ型板式轨道的核心部件,由于板式轨道是典型的“三明治”结构,充填层易受环境的影响而出现性能劣化,从而对轨道结构不利。为探究充填层自密实混凝土性能劣化对板式轨道荷载效应的影响,采用ABAQUS软件并结合已有的充填层混凝土损伤研究结果,建立充填层整体损伤工况和更接近实际使用情况的充填层梯度损伤工况的轨道结构有限元模型,计算轨道结构在不同工况的列车荷载和温度荷载下,轨道板、充填层和底座板的应力与位移变化情况,分析充填层疲劳损伤对轨道结构整体性能的影响。结果表明,充填层混凝土的整体损伤将导致充填层刚度显著下降,在列车和温度荷载下,轨道板和充填层组成的复合板易出现各方向的位移,使轨道结构出现局部磨耗增加和轨道不平顺等现象;充填层受荷时各向应力均大幅减小,轨道板的总体应力上升且易出现应力集中,底座板应力相较于其上部结构受充填层性能变化的影响较小。充填层出现四周梯度损伤时,不同荷载作用下,从损伤区至未损伤区应力和位移表现为连续变化,未出现明显的应力集中和应力突变;不同荷载作用下,轨道结构出现损伤的区域应力明显下降,但未发生损伤的板中部区域应力上升,加速了板中部区域的动载疲劳效应,间接增加了轨道结构的疲劳损伤。

The filling layer is the key component of CRTS Ⅲ slab track structure.Due to the typicalsandwichstructure of the slab track structure,the filling layer is susceptible to environmental influences,leading to degradation of the track structure,which is unfavorable to the track structure.To explore the influence of filling layer self-compacting concrete performance deterioration on the load effects of the slab track structure,the finite element model of track structure with overall damage conditions and gradient damage conditions closer to the actual use of the filling layer were established by ABAQUS software combined with the existing experimental results of damage of filling layer concrete.The variations of stress and displacement of slab track,filling layer and base plate in the track structure under different train load and temperature load were calculated,and the influence of filling layer attack by fatigue damage on the performance of the track structure was analyzed.Results show that the overall damage of filling layer concrete leads to a significant decrease in its stiffness.Under train and temperature loads,the composite plate consisting of the track slab and filling layer experiences displacement in multiple directions,resulting in increasing local wear and unevenness in the track structure.When the filling layer is subjected to load,the stress in all directions decreases significantly.The overall stress of the slab track increases and is prone to stress concentration.Compared with its upper structure,the stress of the base plate is less affected by the change of the filling layer performance.When the gradient damage occurs around the filling layer,the changes of stress and displacement develop continuously change from the damaged area to the undamaged area under different loads,and there is no obvious stress concentration and stress mutation.Under different loads,the stressed region of the track structure affected by damage exhibits noticeable stress decrease,while the undamaged central region of the track structure experiences stress increase,accelerating the dynamic fatigue effects in that area and indirectly contributing to fatigue damage in the track structure.