荷载与侵蚀环境耦合作用下钢-混凝土组合梁桥剪力连接件腐蚀疲劳损伤机理与寿命预测

Stud shear connector is a key part of steel-concrete composite girder bridge. Fatigue damage of the stud shear connectors will weaken the combined effect of the composite girder bridge and affect the traffic safety and even the structural safety. The combined effect of environmental erosion, which leads to stud shear connectors corrosion and deterioration of fatigue resistance of stud shear connectors and vehicle load action which accelerates the corrosion process of the stud shear connectors would cause deterioration of the safety performance of in-service composite bridges. This project aims to study the fatigue damage mechanism and life prediction of the stud shear connectors under the combined effect of vehicle load and environmental erosion in terms of the main disease of in-service composite bridges. Firstly, the evolution mechanism of the stud shear connectors under vehicle load and environmental factors will be studied separately by the experimental and theoretical research. Then, the relationship and the difference between environmental effect and vehicle load effect will be analyzed. The influence of environmental effect and vehicle load effect on the fatigue performance of stud shear connectors will be measured by the fractal dimension of the surface characteristics of the corrosion stud shear connectors. Test method will be proposed for the combined effects. In addition, the fatigue damage evolution mechanism of stud shear connectors under vehicle load and environmental erosion will be studied by experimental and numerical analysis and fracture mechanics theories. The quantitative relationship between the fractal dimension of the surface characteristics of the corrosion stud shear connectors and the size of equivalent initial surface crack will be built. Finally, the residual fatigue life prediction model of the corrosion stud shear connectors will be proposed based on the size of equivalent initial surface crack.

栓钉剪力连接件是钢－混凝土组合梁桥的关键部件，栓钉的疲劳损伤会弱化组合梁桥的组合作用，影响行车安全性甚至结构安全。侵蚀环境作用将导致栓钉锈蚀，降低栓钉的疲劳性能，车辆荷载作用加速了栓钉的腐蚀进程，两者耦合作用将导致组合梁桥结构服役性能急剧退化。本课题拟针对既有组合梁桥结构的主要病害，进行车辆荷载与环境耦合作用下栓钉的腐蚀疲劳损伤机理与寿命预测研究。首先通过试验及理论分析研究车辆荷载及环境因素单独作用下栓钉的损伤演化机理；分析环境与车辆荷载作用效应的联系与区别，以栓钉表面特征的分形维数作为损伤指标来衡量环境与车辆荷载对栓钉疲劳性能的影响，提出两者耦合作用的试验方法；然后通过试验、数值分析与断裂力学理论研究荷载与侵蚀环境耦合作用下栓钉的疲劳损伤演化机理；最后建立锈蚀栓钉表面特征的分形维数与等效初始表面裂纹尺寸间的量化关系，提出基于等效初始表面裂纹尺寸的锈蚀栓钉的剩余疲劳寿命预测模型。

钢-混凝土组合梁桥具有良好的受力性能，兼有钢桥和混凝土桥的各自在经济性、施工性等方面的优点，在综合效益上具有强大的竞争力，具有广阔的应用和发展前景。栓钉剪力连接件是钢－混凝土组合梁桥的关键部件，栓钉的疲劳损伤会弱化组合梁桥的组合作用，影响行车安全性甚至结构安全。侵蚀环境作用将导致栓钉锈蚀，降低栓钉的疲劳性能，车辆荷载作用加速了栓钉的腐蚀进程，两者耦合作用将导致组合梁桥结构服役性能急剧退化。本课题拟针对既有组合梁桥结构的主要病害，进行车辆荷载与环境耦合作用下栓钉的腐蚀疲劳损伤机理与寿命预测研究。首先基于弹塑性地基中横向荷载作用下的单桩理论，提出了栓钉的抗剪承载力、剪切刚度、弹性阶段末端的滑移值等的计算公式；考虑栓钉锈蚀对栓钉抗拉强度和弹性模量力学性能的削弱和栓钉截面削弱，提出了锈蚀后栓钉的荷载-滑移本构关系。然后通过数据拟合，得到了锈蚀栓钉疲劳寿命预测模型中的关键参数的取值；综合考虑锈蚀率对栓钉极限强度、屈服强度、截面直径等的影响，对锈蚀栓钉组合梁的疲劳寿命进行了模拟计算。通过试验对栓钉的疲劳性能进行了系统地研究，结合栓钉的疲劳断面特征和裂纹尺寸，建立了栓钉的疲劳裂纹深度与剩余承载力关系表达式；通过ABAQUS和FRANC3D 软件联用的方式分析了栓钉的疲劳裂纹扩展全过程。基于分形理论对锈蚀后栓钉的表面特征进行了研究，通过试验研究了锈蚀栓钉的力学性能随表面特征值的变化规律。通过试验、数值分析与断裂力学理论研究了荷载与侵蚀环境耦合作用下栓钉的疲劳损伤演化机理。最后建立了锈蚀栓钉表面特征的分形维数与等效初始表面裂纹尺寸间的量化关系，提出了基于等效初始表面裂纹尺寸的锈蚀栓钉的剩余疲劳寿命预测模型。课题的研究成果可以为栓钉的设计提供理论依据，为钢-混凝土组合梁桥设计、状态评估和维护加固等提供技术支撑，对确保组合梁桥的安全运营，促进组合梁桥的应用与发展，具有重大的现实意义。