基于石墨烯机敏传感技术的预应力混凝土梁高应力幅疲劳行为研究

With the rapid development of China's rail transit construction, the load of high speed railway has high frequency and the axle load of heavy haul railway increases gradually. And this phenomenon leads to change in the role of the fatigue characteristics of rail transport structure. Therefore, it is urgent to study the fatigue damage evolution and failure mechanism of prestressedconcrete beams under the effect of fatigue. In view of the fact that the fatigue testing method is difficult to capture the effective characterization of the rapid deterioration of prestressed concrete beam in the later stage, this project is based on graphene materials to develop a large number of highly sensitive graphene sensitive sensors. Based on the dynamic piezoelectric signal and modal test of the fatigue test of prestressed concrete beams under high stress conditions, the fatigue damage variables at different levels are constructed. At the same time, the key parameters of the finite element model are established, and an analysis method of fatigue damage history of prestressed concrete beams based on structural parameter matrix inversion is proposed. Then it is used to determine the fatigue stiffness degradation inflection point and the corresponding failure mode of the prestressed concrete beams under high stress. Thus, the life prediction model of prestressed concrete beam is established. In this paper, by taking the development of graphene smart composite materials in the field of civil engineering applications as a entry point, new ideas and methods for characterization, evaluation and engineering application of the full life service behavior of prestressed concrete beams are provided.

随着我国轨道交通建设的飞速发展，高速铁路的载荷呈现高频化、重载铁路的轴重逐渐增大，这种现象致使轨道交通结构的疲劳作用特征产生变化，亟需研究此种疲劳效应作用下预应力混凝土梁的疲劳损伤演变过程及其失效机理。鉴于现阶段疲劳测试手段难以捕捉预应力混凝土梁后期迅速劣化过程的有效表征量，本项目拟基于石墨烯材料制备开发大量程、高机敏的石墨烯机敏传感元件。通过高应力条件下预应力混凝土梁疲劳试验的动态压电信号和模态测试，构筑不同层次的疲劳损伤变量，并确立与有限元模型相呼应的关键参数。在此基础上，提出基于结构参数矩阵反演的预应力混凝土梁疲劳损伤历程的分析方法，分析确定高应力条件下预应力混凝土梁的疲劳刚度退化拐点及相应的失效模式，由此建立预应力混凝土梁的寿命预测模型。本研究以研发石墨烯机敏复合材料在土木工程领域应用为锲入点，为预应力混凝土梁的全寿命服役行为刻画、评估及其工程应用提供新思路、新手段和新方法。

我国轨道交通建设的飞速发展，高速铁路的高频载荷、重载铁路的大轴重趋势鲜明，这导致轨道交通结构的疲劳作用特征显著变化，亟需研究此种疲劳效应作用下预应力混凝土梁的疲劳损伤演变过程及其失效机理。鉴于现阶段疲劳测试手段难以捕捉预应力混凝土梁后期迅速劣化过程的有效表征量，本项目基于石墨烯材料制备开发了大量程、高机敏的石墨烯机敏传感元件。系统测试分析了研发的石墨烯感应元件的基本性能、工作性能及对应变和裂缝的感知能力，并通过理论及试验研究，明确了石墨烯感应元件输出信号与应变以及裂缝宽度之间的数学率定关系。基于研发的石墨烯传感元件，通过高应力条件下预应力混凝土梁疲劳试验的动态压电信号和模态测试，实现了预应力混凝土梁疲劳过程应变-裂缝的非连续变形监测；构建了基于石墨烯感应元件监测数据的预应力混凝土梁疲劳残余应变测试分析方法，形成了基于石墨烯感应的预应力混凝土梁疲劳变形长期监测方法；构筑了不同层次的疲劳损伤变量，并确立与有限元模型相呼应的关键参数。在此基础上，基于模态应变能和Bayes数据融合理论，通过对基于刚度和基频的疲劳损伤反演，以及针对变幅疲劳情况提出了“分块拟合法”理论模型，得到了等幅和变幅疲劳作用下PC梁的疲劳损伤演化函数。结合疲劳失效阈值的设定，提供一种疲劳损伤程度和失效状态评估方法，由此建立了预应力混凝土梁的寿命预测模型。本研究以研发石墨烯机敏复合材料在土木工程领域应用为锲入点，为预应力混凝土梁的全寿命服役行为刻画、评估及其工程应用提供了新思路、新手段和新方法。