随机车流及空间温度耦合作用下钢-混组合桥面结构疲劳损伤机理研究

At the beginning of this century the steel-concrete composite bridge deck had been widely applied in the long-span bridges, and its theoretical fatigue life is still in the early stage up till now. However, the practical application indicates that the fatigue of the composite structure has become more and more serious, and it has become the most important and urgent problem to be solved urgently for the application. In the proposal, based on the monitoring of real bridge structure, the theoretical analysis, and the studying of model experiment, the basic theory on the damage mechanical of fatigue for the steel-concrete composite bridge deck will be carried out from the view of the effect of the structural form of shear connectors and the coupled effect of random vehicle load and 3D temperature gradient. The main research content includes the following parts. (1) The refine finite-element models and experimental models will be established to determine the internal relations between the structural form of shear connectors and the fatigue damage mechanical for the steel-concrete composite bridge deck. (2) The fatigue load model for the multiple random vehicle load will be set up to reveal the dynamic evolution law of the fatigue damage on the steel-concrete composite bridge deck. (3) A new fatigue research method considering the 3D temperature gradient will be proposed to explore the inner laws between the 3D temperature gradient and the fatigue damage mechanism for the steel-concrete composite bridge deck. (4)The theory and experimental method under coupled complex multiple factors will be developed to research the fatigue damage mechanical of the steel-concrete composite bridge deck under the coupled action of the random traffic load and the 3D temperature gradient. The research findings not only have great engineering value in promoting the application and development of the steel-concrete composite bridge deck system, but also have important significance to further enrich and develop the bridge structural calculation theory.

钢-混组合桥面结构的大规模应用始于本世纪初，理论疲劳寿命尚属早期；而实桥调研发现组合桥面结构疲劳已日益严重，当下已成亟待解决的关键问题。本课题拟采用现场监测、理论分析及模型试验相结合的方法，考虑剪力连接件构造形式的影响，从随机车流荷载及空间温度梯度的耦合作用入手，对钢-混组合桥面结构的疲劳损伤机理展开基础理论研究。主要内容包括：（1）构建精细化有限元模型及试验模型，探明剪力连接件构造与疲劳损伤之间的内在联系；（2）建立高维度随机车流疲劳荷载模型，揭示随机车流荷载对结构疲劳损伤影响的动态演化规律；（3）提出一种空间温度梯度的疲劳研究新模式，探求空间温度梯度与疲劳损伤之间的内在关系；（4）发展多因素耦合作用的分析理论及试验方法，揭示随机车流荷载与空间温度梯度耦合作用下组合桥面结构的疲劳损伤机理。研究成果对促进钢-混组合桥面的应用与发展具有重大工程价值，对丰富和发展桥梁结构计算理论具有重要意义。

钢-混组合桥面结构的疲劳问题是工程中较难解决的问题之一。本项目利用结构健康监测系统的空间温度梯度与随机车流荷载监测数据，系统地建立了运营状态下钢-混组合桥面结构疲劳评估方法，分析了空间温度梯度与随机车流荷载耦合作用下钢混组合桥面系的疲劳性能影响规律。主要研究内容包括：（1）剪力连接件构造与疲劳损伤之间的内在联系；（2）随机车流荷载下组合桥面结构疲劳损伤的动态演化规律研究；（3）空间温度梯度下组合桥面结构疲劳损伤的动态演化规律研究；（4）随机车流与空间温度梯度耦合作用下组合桥面结构的疲劳损伤机理研究。研究发现：（1）初始裂纹对栓钉的疲劳寿命影响较大，其中裂纹长径比影响最大，相对裂纹高度影响较小；直径越大的栓钉其裂纹对疲劳寿命的影响越大；（2）“结构特征、时间特征、环境特征—温度、 温度效应”映射具有高度非线性，单独BP网络或LSTM网络效果不佳，而BP-LSTM混合模型精度较高；（3）改进量子遗传算法相较于传统遗传算法、量子遗传算法具有更高的性能与精度，自动交互修正方法的效率较高，对材料弹性模量、厚度、车辆荷载等参数的修正与工程实际测试的情况基本吻合；（4）不同约束条件下的钢-混凝土桥面板均受竖向温度梯度影响明显，其应力效应不容忽视；（5）不同温度场分布下车辆荷载应力时程曲线峰值最大可相差一倍以上，不考虑温度作用对车辆疲劳荷载效应的放大作用可能使结构抗疲劳设计偏不安全。项目研究成果成功应用于盐坪坝长江大桥，也可为同类型桥梁的运营疲劳评估提供参考。