张志田　吴肖波　葛耀君　陈政清

摘要：基于现场观测，对特大跨度悬索桥吊杆风致振动现象进行了定性分析，排除了尾流驰振、涡激共振以及风雨激振的可能性.通过数值模拟和理论分析，表明这是一种主缆抖振引起的吊杆共振现象.随机风场激起主缆的随机抖振，而主缆的抖振含有丰富的模态成份，当吊杆的自振频率与具有一定抖振能量的主缆模态的频率充分接近时会激发吊杆的共振.因此，从来流紊流风场中获得能量的是主缆而非吊杆自身.由于与主缆的模态质量相比，一根或几根吊杆的模态质量很小，因此吊杆大幅振动吸收的能量并不会对主缆的振动带来实质性的影响，从而可形成一个相对稳定的能量供给机制.此外，在主缆上加设TMD抑制主缆在吊杆自然频率附近的振动，对吊杆风振有明显的抑制效果.

关键词：悬索桥；吊杆；主缆；抖振；共振；调质阻尼器

中图分类号：U448.25 文献标识码：A

Abstract：The mechanism of windinduced oscillation of hangers in a longspan suspension bridge was investigated qualitatively on the basis of field observations， and the possibility of wake galloping， or vortexinduced resonance， or windraininduced oscillation was excluded by reasoning. Numerical simulation and theoretical analysis reveal that this is a kind of resonance induced by the buffeting of main cables. Stochastic wind fields excite the stochastic responses of the main cables， which are abundant in a wide range of modal components， and the resonance occurs when the natural frequency of a hanger is adequately close to one of the main cables natural frequencies that possess enough energy. Hence， it is not the hangers themselves but the main cables that are responsible for the energy absorbing from the turbulence. Compared with the modal mass of a main cable， the mass of one hanger is too small to pose substantial effects on the oscillation of the main cable， and therefore， a steady supply of energy from the main cable to the hangers can be formed. Furthermore， TMD mounted on the main cables can suppress the windinduced vibration of cables at the natural frequency of hangers， which results in the significant reduction of the vibration of the hangers.

Key words：suspension bridge； hanger； main cable； buffeting； resonance； tuned mass damper

拉索体系桥梁是风敏感结构，其主要构件易发生各类风致振动.除加劲梁易发生的颤振以及涡激共振现象外，拉索以及吊杆的风致振动也是极易出现的问题.在桥梁缆索的风振方面，国内外的研究大多围绕在较易发生振动的斜拉索展开，原因是倾斜的拉索容易发生风雨激振及参数共振等振动现象[1-2].而关于竖直安装的圆形吊杆却仅限于单根索的涡激振动和多根并列索的尾流驰振问题[3-5].2012年8月，台风“海葵”登入我国东海岸，引起国内某特大跨悬索桥吊杆的大幅振动.如图1所示，该大桥管理部门的视频资料显示了吊杆的振动强度.部分重要特征总结如下：1）桥塔附近的长吊杆振动激烈，短吊杆振动不明显；……