悬索桥吊索多索股气动干扰机理及其参数优化研究

In recent years, large amplitude oscillations of hangers on several suspension bridges took place under the action of wind. However, it is difficult to put forward effective counter measures to mitigate these kinds of oscillations in time for the lack of the mechanism explanation. It could be found from the field observations on the Xihoumen Bridge that the aerodynamic interference effects between the hangers play an important role for the hanger vibration. Theoretical analyses, wind tunnel tests and field observations are adopted to study the mechanism of aerodynamic interference of the hangers, and some key parameters are optimized. First, wind tunnel tests are carried out to measure the mean aerodynamic forces on the hangers by use of force balance, and these aerodynamic forces are fitted as a function of space coordinates. Second, 2-D and 3-D theoretical models for the interference effects of the hangers of suspension bridges are established to investigate the characteristics of aerodynamic stiffness and damping, the unstable spatial region and wind speed range, and the amplitude of the hangers. The mechanism of the interference effects of the hangers is carefully analyzed. Third, field observations and wind tunnel tests are conducted to verify the results of theoretical analyses. Finally, some key parameters, including the distance of the hangers, structural damping, the distance of spacers, are optimized to provide a reference for the structural design and mitigation of the hangers of the suspension bridges.

近年来多座悬索桥吊索发生大幅风致振动，由于对其机理缺乏深刻认识，难以及时提出有针对性的振动控制措施，严重影响吊索甚至悬索桥的结构安全。从西堠门大桥吊索的观测资料发现，索股间的气动干扰是吊索发生大幅振动的重要原因。本项目拟采用理论分析、风洞试验和现场观测相结合的方法，研究悬索桥吊索气动干扰机理，并对关键参数进行优化研究。首先，采用天平测力风洞试验方法，研究悬索桥吊索多索股相互影响下的索股平均气动力系数随空间位置的变化规律，并对其进行拟合；其次，采用准定常理论，建立悬索桥吊索多索股气动干扰的二维和三维理论模型，研究吊索气动干扰失稳时的气动刚度和阻尼特性、不稳定空间区域和风速范围、索股振幅等，对其机理进行解释；然后，采用现场实测和风洞试验两种方法，对理论分析结果进行验证；最后，对吊索的关键参数进行优化研究，包括索股间距、阻尼、分隔器间隔等，为悬索桥吊索的结构设计和振动控制措施的选择提供理论参考。

大跨度悬索桥吊索具有自重轻、柔度大、阻尼低的特点，极易发生各类风致振动。本项目采用理论分析、风洞试验及现场实测三种方法对悬索桥多索股吊索尾流致振机理进行研究。首先，对西侯门大桥吊索风致响应开展了现场实测研究。其次，采用天平测力方法，研究了吊索相互干扰情况下的平均气动力系数空间分布。然后，推导建立了吊索尾流致振准定常、非定常两自由度理论模型以及三维连续弹性索理论模型，研究了吊索尾流致振机理以及准定常理论在尾流致振中的适用性。最后，开展了二维、三维吊索气弹模型尾流致振风洞试验，研究了不同空间位置处吊索的振动响应以及螺旋线、分隔器减振效果。研究结果表明：(1)准定常理论可反应尾流致振的主要特征。(2)悬索桥吊索尾流致振由气动负刚度驱动。(3)相比于平行钢丝吊索，钢绞线吊索的气动稳定性更优。(4)索股间加装分隔器可有效抑制吊索尾流致振。本项目研究成果为悬索桥吊索结构设计和振动控制措施的选取提供了理论参考。