新型BFRP桁架增强无砟轨道板及其盐冻-疲劳耦合作用机理研究

A mutual inductance is created between the steel truss reinforced ballastless track slabs and the signal currents in the track circuit, which significantly reduces the transmission length of the track circuit and the safety distance of train. To solve this problem, a new type of ballastless track slab reinforced with Basalt Fiber Reinforced Polymer (BFRP) truss is proposed. However, the working mechanism and design theory of this new structure under salt-freezing are not clear. The project focuses on the performance of BFRP truss reinforced ballastless track slab by conducting a series of studies from the construction stage to the use stage. Firstly, the static performance of BFRP truss sleepers will be investigated, the parameters considered in the test are BFRP diameter, truss height, web diameter and web spacing, the evaluation indexes (stiffness and stability) of the ballastless track slab in construction stage will be proposed. Furthermore, the static performance (mainly focused on capacity, deflection and crack) of BFRP truss reinforced ballastless track slab under salt-freezing will be studied, and the reasonable evaluation method on the key performance index will be proposed combined with the analysis of finite element model. Finally, the fatigue performance of BFRP truss reinforced ballastless track slab under the salt-freezing will be studied. The relationship between fatigue life and the performance index (such as deflection, stiffness and crack width) will be revealed, the fatigue damage mechanism will be studied and the fatigue life prediction model will also be established. The research results can provide certain theoretical basis and technical support for the application of such new type of ballastless track slab in high-speed railway.

钢筋桁架增强无砟轨道板与轨道电路的信号电流产生电磁感应，导致信号传输长度缩短，列车运行安全距离减小。本项目提出玄武岩纤维复合材料（BFRP）桁架增强无砟轨道板有望解决绝缘问题，但在盐冻环境下的工作机理与设计理论还不明确。聚焦这一问题，围绕BFRP桁架增强无砟轨道板，拟展开从施工阶段到使用阶段性能的研究。首先，通过BFRP桁架增强轨枕稳定性能研究，探明弦杆直径、桁高、腹杆直径/间距对性能的影响，提出承载力和稳定性的评价指标；其次，通过盐冻环境下BFRP桁架增强无砟轨道板静力性能研究，揭示承载力、挠度和裂缝的变化规律，结合有限元模型参数分析的结果，提出合理的计算方法；最后，通过盐冻环境下BFRP桁架增强无砟轨道板疲劳性能研究，明确挠度、刚度和裂缝与疲劳寿命的关系，揭示疲劳损伤演化机理，建立疲劳寿命预测模型。研究成果可为该新型无砟轨道板在高速铁路中的推广应用提供一定的理论基础和技术支持。

项目背景：在高速铁路系统中，无砟轨道板与轨道电路系统存在着不兼容问题，主要原因是钢筋形成的闭合回路与高频信号电流互感，使轨道电路的信号传输长度缩短，从而减少了列车运行的安全距离。本项目提出的BFRP桁架增强无砟轨道板有望解决闭合回路问题，但在长期的列车轮载作用下，其工作机理还需研究，相应的设计理论仍需探索。.主要研究内容：把握BFRP桁架增强轨枕稳定性的变化规律，探明对性能影响的关键因素；其次，明确BFRP桁架增强无砟轨道板静力性能的变化规律，在此基础上，结合精细化有限元模型分析参数对结构性能的影响，提出性能指标的计算方法。最后，在使用阶段，研究BFRP桁架增强无砟轨道板在疲劳作用下损伤规律，揭示疲劳损伤演化机理，建立疲劳寿命预测模型。.主要结果：四种新型纤维复合桁架增强双块式轨枕的堆放状态承载力可以满足实际要求。轨枕Sleeper-TB1的最大荷载较轨枕Sleeper-T0提高了7.5%，轨枕Sleeper-TS1最大荷载较轨枕Sleeper-T0提高了13.4%。.四块新型纤维复合桁架增强双块式轨道板均能满足承载力要求，且较钢筋桁架双块式轨道板均有所提高，轨道Slab-TB1、Slab-TS1、Slab-TB2和Slab-TS2的极限承载力较轨道板Slab-T0分别提高了27.3%、20.7%、28.5%和16.2%。可通过理论计算对轨道板极限承载力和裂缝宽度进行预测。.在确定疲劳上限值后，轨道板的破坏形态也各不相同，轨道板Slab-T0在满足200万次循环加载后静压破坏，破坏形态为下弦杆钢筋拉断，受压区混凝土压溃；依据部分试件的疲劳寿命与荷载水平的关系，拟合出P-N曲线并给出预测新型轨道板疲劳寿命的公式，结果表明二者较为吻合。.本项目研究结果，为新型BFRP桁架增强无砟轨道板的提供了一定的试验数据，为该类型无砟轨道的推广应用也提供了一定的理论基础。