大跨悬索桥桥塔复杂绕流场影响区吊索大幅风致振动的机理与控制

Consider that the wind-induced vibrations of suspenders of long-span suspension bridges are very critical; this project will focus on the mechanism and control of the large amplitude wind-induced vibrations of the suspenders located in the complicated flow field around the bridge tower based on field monitoring. First, according to the feather of the flow field around the bridge tower, this project will study on the characteristics of the large span wind-induced vibrations of the suspenders located in the complicated flow field around the bridge tower and the interaction between the suspender vibrations with the flow field around the bridge tower. Second, this project will develop the numerical simulation method for the large amplitude wind-induced vibrations of the suspenders located in the complicated flow field around the bridge tower, and study on the vibration characteristics, aerodynamic force characteristics and the flow field characteristics and these characteristics changing with the feathers of the flow field around the bridge tower (flow field region, mean velocity, turbulence intensity, power spectrum, integral length scale, and so on). This project will set up the nonlinear aerodynamic force model and the nonlinear vibration equation, analyze the nonlinear dynamic characteristics of the suspenders and develop the analysis theory and method of the wind-induced vibration of the suspenders. Third, this project will develop a passive jet control method and for controlling the complicated flow field around the bridge tower and suppressing the large amplitude wind-induced vibrations of the suspenders and develop a damping control method to control the wind-induced vibrations of the suspenders, reveal the flow field characteristics of the flow control and the control mechanism of two control methods and present the optimization method for the control parameters. The project study will enrich and develop the wind engineering theory of super large-span bridges and provide the scientific and technical supports to protect performance and the service safety of large-span suspension bridges and have important scientific significance and practical value.

针对大跨度悬索桥桥塔复杂绕流场及其导致的吊索大幅风致振动，研究基于原型观测的大跨度悬索桥桥塔复杂绕流场中吊索大幅风致振动特性及其与桥塔绕流场之间耦合作用；发展大跨度悬索桥桥塔复杂绕流场中吊索大幅风致振动的数值计算方法，研究吊索风致振动特性、气动力特性与绕流场特性，以及上述特性随桥塔绕流场特性的变化规律，建立吊索大幅风致振动的非线性气动力模型和非线性振动方程，分析吊索的非线性动力效应和特性，研究吊索在桥塔复杂绕流场中大幅风致振动的机理和临界条件的判别准则，发展吊索在桥塔复杂绕流场中风致振动的分析理论和方法；发展桥塔绕流场与吊索风致振动的被动吹气流态控制方法和吊索风致振动的阻尼控制方法，揭示流态控制方法的流场特性与两种方法的控制原理，提出其参数优化方法。本项目研究将丰富和发展特大跨度桥梁结构风工程理论，为保障大跨度悬索桥服役性能和服役安全提供科学和技术支撑，具有重要的科学意义和实用价值。

针对大跨度悬索桥桥塔复杂绕流场中吊杆大幅风致振动问题，本项目采用数值模拟、风洞试验和理论分析等手段，研究大跨度悬索桥桥塔复杂绕流场特性及其影响区吊索大幅风致振动的特性、机理和控制方法。. 首先，基于风洞试验，研究了不同来流风偏角下典型大跨度悬索桥桥塔绕流场特征，分析得到了桥塔尾流速度场、湍流度场、脉动速度主导频率场分布规律。进一步进行了0度风偏角下桥塔尾流区吊索风致振动特性研究。研究得到了吊索尾流致振动主要由桥塔尾流旋涡脱落与高湍流度共同诱发。研究发现吊索振动存在“软锁定”机制，即吊索振动频率随风速变化，且存在明显频率锁定区间；在锁定区内，吊索频率被锁定到桥塔尾流频率。. 然后，基于数值模拟，考虑桥塔尾流、流固耦合效应及吊索间碰撞，建立了桥塔尾流区四根吊索风致振动的CFD数值模型。数值模拟得到了桥塔尾流场特征，吊索气动力特征与振动特征。结果表明，在桥塔尾流作用下，当桥塔尾流频率与吊索频率一致时，四根吊索发生大幅值振动并发生碰撞；并揭示了吊索发生碰撞的原因是各吊索气动力在顺流向存在巨大差异。进一步，基于理论分析，建立桥塔尾流致吊索振动的气动力模型和非线性运动方程，计算得到桥塔尾流区吊索大幅值风致振动特征。 . 最后，基于风洞试验与数值模拟，发展了拉吊索风致振动的被动吸吹气流动控制方法。研究了被动吸吹气套环的开孔数量，套环高度与厚度，套环间距以及雷诺数等对控制效果的影响规律，并得到了最优控制参数组合。同时，研究了桥塔尾流场的被动吸吹气套环控制效果，在被动吸吹气控制下，尾流区域内脉动风速具有主导频率的区域大幅减小，吊索振动幅值得到较大抑制。进一步，将吊索风振的被动吸吹气控制方法用于斜拉索的涡激振动和风雨激振的控制，控制效果非常明显。最后，该方法成功应用于实际工程，有效地降低了圆形结构的风致振动幅值