矩形板式刚性吊杆涡振与驰振耦合振动机理及幅值估算研究

Compared to flexible cables, plate rigid hangers with rectangular sections (rectangular rigid hangers) have obvious application advantages in railway arch bridges due to its large structural rigidity and no need to change during the whole operation period. While, for rectangular rigid hangers, a kind of large amplitude wind-induced vibration will occur at relatively low wind speed because of the coupling effects of aerodynamic forces when the onset velocities of vortex-induced vibration and galloping are close to each other. This kind of coupling oscillation can even control the overall design, the hangers whose aspect ratio ranges from 0.5 to 3.0 are suffering from risks, and it actually happened on several real bridges home and abroad. At present, the vibration mechanism of this coupling oscillation was lacking, the evaluation and controlling system need to be established. The combined research means as theoretical analysis, wind tunnel tests, numerical simulation and mathematical statistics will be taken in this project to study the coupling oscillation mechanism of vortex shedding and quasi-steady galloping aerodynamic force, build the mathematical model of coupling aerodynamic force and structural dynamic equation, establish the occurring evaluation criteria of this coupling oscillation, identify the key parameter of amplitude response of coupling oscillation, and finally perform the regression analysis on collected measure data. After that, the regulations of wake vortices during initial and developing stages of coupling oscillation will be discovered, the aerodynamic optimization measures to avoid coupling oscillation could be discussed, the prediction method on onset velocity and empirical formula on amplitude response of coupling oscillation for rectangular rigid hangers will be proposed, then the wind-resistant design and fatigue damage evaluation for this type of hangers could be well-founded.

矩形板式刚性吊杆结构刚度大、服役期间不需更换，相对于柔性吊索在高速铁路拱桥中具有明显的应用优势。当矩形板式刚性吊杆涡激共振与驰振临界风速相近时，气动力耦合作用将导致一种较低风速下的大幅风致振动，控制结构设计，截面宽高比在0.5~3.0范围内的吊杆均存在隐患，国内外已有多座桥梁发生了该类振动，目前对作用机理缺乏认识，预测和评估体系亟需建立。本项目拟采用理论分析、风洞试验、数值计算和数理统计相结合的研究手段，开展涡激力和准定常驰振力耦合作用机理研究、耦合气动力和结构动力学方程数学建模研究、耦合振动发振评判准则研究、振动幅值估算关键参数识别和实测数据回归分析等研究工作，得出耦合振动发生及发展的尾流涡迹变化规律，探讨规避耦合振动的气动优化措施，提出适用于矩形板式刚性吊杆涡振与驰振耦合振动的起振临界风速预测方法和幅值估算经验公式，为该类吊杆的抗风设计和疲劳累计损伤评估提供依据。

涡激共振与准定常驰振临界风速相近时，以大跨度拱桥矩形板式刚性吊杆为代表的一类钝体构件易发一种耦合风致振动，区别于发散性驰振，是一类响应幅值随风速的增加而线性增长的“软驰振”现象，影响结构使用性能甚至结构安全，是一种严重的工程病害，指导抗风设计研究成果缺乏。.基于经典涡激共振理论和准定常驰振理论建立了“软驰振”数学模型，通过数值分析明确了质量、阻尼是影响耦合程度、估算幅值响应的关键参数。结合大跨度拱桥矩形板式吊杆截面实际工程参数以及用于建立幅值估算经验公式现有实测数据库，选定一组宽高比1.2:1矩形截面设计制作风洞试验节段模型和气弹模型，通过调整模型系统等效刚度、等效质量和阻尼比，实现了Reynolds数一致情况下，相同质量不同阻尼比、相同阻尼比不同质量以及相同Scruton数不同质量、阻尼组合的对比试验工况，实测风振响应，开展对比风洞试验研究。.研究表明：在涡激共振与驰振非耦合状态下，相同Scruton数不同质量、阻尼量值组合对比工况中，实测涡振幅值大小各不相同，最大最小比值达到2.7，涡振幅值质量、阻尼敏感性不相同；质量、阻尼单参数对比研究工况中，实测涡振幅值随着质量、阻尼的增大而减小，权重系数不同，质量对于涡振幅值的影响程度大于阻尼；提高等效质量是降低结构涡振幅值更为有效的措施。在涡激共振与驰振耦合状态下，组成Scruton数的质量、阻尼参数对“软驰振”幅值响应的影响是独立的，权重相同；存在影响“软驰振”幅值响应Scruton数“锁定区间（12.4~30.6）”，“锁定区间”内，无量纲风速-幅值响应曲线线性斜率（Slope）不随Scruton数变化而变化，并存在一个使风致振动由耦合状态转变为非耦合状态的Scruton数“过渡区间（26.8~30.6）”；修正了“软驰振”响应幅值估算经验公式，可用于类似工程杆件设计风速范围内的幅值预测。