锈蚀环境中开裂高速铁路混凝土桥梁动力刚度演化机制与对行车安全的影响

Based on the geometrical characteristic and mechanical behavior of cracks within the concrete structure, the evolution of the dynamic stiffness of the cracked high-speed railway concrete bridge affected by steel corrosion is proposed to access its influence on the safety of train running. Firstly, the effect of the axial force on the breathing of the primary cracks and interfacial microcracks will taken into account in order to model the dynamic stiffness of the prestressed reinforced beam and the reinforced concrete pier. Secondly, the influence of steel corrosion on the effective pre-compressive force, the effective steel area, and the bond between steel and concrete will be analyzed to model the dynamic stiffness of the cracked reinforced concrete beam with steel corrosion. Thirdly, the prestressed reinforced concrete specimens will be loaded to create pre-cracking by using static loading and restrained shrinkage, respectively. The dynamic responses of the specimens under free and forced vibrations will be meausred, respectively. The dynamic stiffness can be calibrated by using the dynamic response. Forthly, the comparison between the theory and experimental dynamic stiffness can reveal the effects of the pre-compressive load, dynamic loading level, steel corrosion and the spatial distribution of cracks on the breathing of primary cracks and interfacial microcracks, and on the dynamic stiffness. Finnally, based on the requirements of comfort and safety of high-speed railway, multi-level evaluation index of the cracked high-speed railway bridge affected by the steel corrosion will be suggested, using the dynamics.of coupled system in high-speed trains and fundamental structures.

项目从混凝土结构的裂缝几何特征与受力机理出发，探寻锈蚀环境中高速铁路混凝土桥梁开裂后的动力刚度演变机制，以期揭示其性能演变对高速铁路行车安全的影响。研究包括：分析轴向力对混凝土主裂缝与界面裂缝呼吸机制的影响，以建立预应力混凝土梁与钢筋混凝土桥墩的动力刚度模型；分析预应力筋的锈蚀对梁体有效预压力，钢筋有效面积以及钢筋—混凝土粘结机制的影响，从而得到考虑钢筋锈蚀的开裂钢筋混凝土梁动力刚度模型；利用静力加载与约束收缩两种方式制作带裂缝的预应力混凝土梁试件，并进行不同程度的锈蚀试验；利用锈蚀后梁体的自由振动与强迫振动试验，测试梁体的动力响应并推算动力刚度；利用实测与理论动力刚度对比结果，分析预应力，激励水平，钢筋锈蚀与裂缝空间分布对两类裂缝的呼吸机理以及动力刚度的影响；最后，利用高速列车——基础结构系统动力学方法，结合高速列车舒适性与安全性要求，制定多水准的高速铁路桥梁开裂劣化评价指标。

发展高速铁路作为我国最重要的战略之一，在以桥代路的背景下，预应力混凝土桥梁的性能劣化是高速铁路基础结构动态性能劣化的重要表现之一。实现高速铁路混凝土桥梁结构动态性能演化的列车运营安全评估，需要对锈蚀环境下开裂高速铁路混凝土桥梁的动力刚度演化机制进行研究。项目从混凝土结构的裂缝几何特征与受力机理出发，以揭示锈蚀环境中高速铁路混凝土桥梁开裂后的动力刚度演变机制为目标，分析了轴向力对混凝土主裂缝与界面裂缝呼吸机制的影响。基于粘结滑移理论，引入混凝土收缩徐变对钢筋混凝土粘结程度产生的影响，计算残余荷载作用下的损伤因子Dccc，给出了考虑钢筋与混凝土粘结损伤后的卸载残余裂缝宽度计算方法，建立了考虑轴向力作用的开裂钢筋混凝土梁动力刚度模型。通过对长期服役钢筋混凝土梁剩余承载能力进行研究，提出了长期服役钢筋混凝土梁剩余承载能力的分析方法；通过对开裂钢筋混凝土梁的自由振动试验，评估了钢筋锈蚀对开裂混凝土梁动力刚度的影响。通过冲击力的简化模拟方法与车-桥-防护结构耦合振动模型相结合，分析了公铁两用桥梁，铁路行车引发的车辆、桥梁、防护结构振动对行车舒适性与安全性的影响；并建议在南京长江大桥维修改造涉铁工程中的施工棚架中，采用增大木板厚度的优化方案。项目的研究成果将为制定多水准的高速铁路桥梁开裂劣化评价指标提供依据，为在役高速列车行车的舒适与安全提供保障。