基于车-轨-桥耦合振动的钢桥面系疲劳机理分析与剩余寿命预测

The accurate computation of fatigue load effects in steel bridges is the foundation of effective fatigue assessment. Due to continuous increasing of train axle weight and speed, coupled dynamic effects between the train and bridge become more significant than before. These dynamic effects may not be well captured by traditional calculation methods intended for the fatigue load effects, and therefore, the resultant fatigue stress data can be lack of accuracies. Based on the multi-scale coupled vibration analysis of the train-track-bridge system, a fine and efficient approach to the computation of fatigue stresses in the deck system of railway steel bridges is proposed in the present project. By using the in-situ measured data, the proposed approach is validated. Subsequently, key factors in the train-track-bridge system are investigated to explore the roles they play in the initiation and propagation of fatigue cracks in the bridge deck system. Mechanisms of the fatigue damage in bridge decks are further clarified. Based on the linear elastic fracture mechanics, the propagation of fatigue cracks in fatigue-critical areas is simulated and remaining fatigue life is predicted. In addition, the influence of train axle load and composition, operation speed, track condition, and traffic evolution on the bridge service life is investigated. This project aims to propose a systematic approach, capable of considering coupled vibration effects of the train-track-bridge system, to the fatigue mechanism analysis and remaining life projection associated with steel bridge decks. It is anticipated that this project can contribute to the fatigue evaluation theories of the railway steel bridges and provide technical support for the bridge management, maintenance, repair, and reinforcement.

准确求解钢桥疲劳荷载效应是有效开展疲劳评估的基础，随着列车轴重和速度的不断提升，列车与桥梁之间的耦合动力效应较以往更为显著，传统的疲劳荷载效应计算方法难以真实反映上述动力效应，所得疲劳应力数据精度不足。本课题基于列车-轨道-桥梁多尺度耦合振动分析，建立铁路钢桥面系疲劳应力精细化高效计算方法，采用现场实测数据对所建立的方法进行验证。在此基础上，研究列车-轨道-桥梁系统关键因素对钢桥面系疲劳裂纹萌生与扩展的作用规律，阐明桥面系疲劳损伤发生机理。基于线弹性断裂力学理论，模拟关键部位疲劳裂纹扩展过程并预测其剩余疲劳寿命，研究列车轴重和编组、线路运营速度、轨道条件、交通运量演变等对桥梁使用寿命的影响。本课题旨在建立一套考虑列车-轨道-桥梁耦合振动效应的钢桥面系疲劳机理分析与剩余寿命预测方法，可为铁路钢桥的疲劳评估理论做出贡献，同时为钢桥管理养护、维修加固等提供科学依据和技术支撑。

疲劳作为金属结构的固有问题，是钢桥在寿命期内面临的主要服役安全威胁。随着我国铁路运输向着高速化、重载化方向发展，列车与钢桥之间的动力效应更为显著，进而产生更大的疲劳损伤累积。既有的疲劳荷载效应计算方法难以真实反映上述动力效应，可能导致不准确甚至无效的疲劳评估结果。本项目针对这一桥梁工程领域迫切需要解决的工程实际难题，基于列车-轨道-桥梁耦合振动分析，系统研究了钢桥面系在车致振动下的疲劳损伤机理分析及剩余寿命预测基础理论。建立了基于列车-轨道-桥梁耦合振动的钢桥面系疲劳应力精细化分析方法，将列车、轨道、桥梁作为一个耦合的动力系统考虑，实现了轨道结构对桥面系应力响应影响的真实模拟，通过钢桥实测数据对分析方法进行了验证。基于多尺度有限元分析方法，研究了列车与轨道、桥梁之间的多尺度耦合振动，研制了热点区域疲劳应力高效计算方法，解决了计算效率与计算精度难以兼顾的难题。基于列车-轨道-桥梁耦合动力仿真分析，研究了多种因素对桥面系疲劳应力的影响规律，解析了桥面系局部振动、面外振动、扭转变形等对疲劳荷载效应及疲劳裂纹萌生、扩展的影响机制，阐明了钢桥面系在列车动载作用下疲劳损伤发生机理。采用基于断裂力学理论，实现了钢桥面系关键部位从初始疲劳裂纹萌生至临界疲劳裂纹出现的全过程寿命预测。研究了运营车速、线路轨道条件、线路交通运量演变等对疲劳裂纹扩展寿命的影响规律，比较分析了所提出的方法与既有方法的评估结果。项目研究成果发展和完善了铁路钢桥的疲劳评估理论，为钢桥养护管理、维修加固等提供科学依据和技术支撑。