大跨桥梁主梁涡振的转角抑振理念及伸臂阻尼实现  

Vortex-induced vibration mitigation of long-span bridges with rotational damping:concept and design of damped outriggers

作　　者：陈林 刘展行[1] 赵林 孙利民[1,2,3] Chen Lin;Liu Zhanhang;Zhao Lin;Sun Limin(College of Civil Engineering,Tongji University,Shanghai 200092,China;State Key Laboratory for Disaster Reduction in Civil Engineering,Tongji University,Shanghai 200092,China;Shanghai Qi Zhi Institute,Shanghai 200232,China)

机构地区：[1]同济大学土木工程学院,上海200092 [2]同济大学土木工程防灾全国重点实验室,上海200092 [3]上海期智研究院,上海200232

出　　处：《土木工程学报》2024年第7期22-36,共15页China Civil Engineering Journal

基　　金：国家自然科学基金(52278314);国家重点研发计划(2022YFC3005301)。

摘　　要：大跨桥梁频率低而密集且固有阻尼小,易出现风致振动,呈现出起振风速低、振动模态多和持续时间长的潜在风险。文章提出一种利用主梁转角变形附加旋转阻尼的大跨桥梁多阶模态减振方法,并提出伸臂阻尼系统的实现方式。首先,利用悬索桥的简化张拉梁模型研究伸臂阻尼系统对张拉梁多阶模态的阻尼效果,采用典型悬索桥的主缆索力和主梁抗弯刚度参数,分析表明单个伸臂阻尼系统能提升模态阻尼比达到0.8%;探究了主梁抗弯刚度与主缆索力比值、伸臂刚度和位置等对阻尼效果的影响规律。以舟山西堠门大桥为例,建立了带黏滞型伸臂阻尼系统桥梁的有限元模型。通过复特征值分析,研究了伸臂阻尼系统对多阶模态的阻尼效果、伸臂刚度和安装位置对阻尼的影响等。分析表明,大跨桥梁单侧塔梁设置刚性伸臂阻尼系统能够使大桥出现过涡激振动的7阶模态中的6阶模态阻尼比达到0.98%以上;双侧安装,上述6阶模态阻尼比能达到1.12%以上。实际设计伸臂抗弯刚度达到2倍主梁抗弯刚度时,可认为满足伸臂刚度需求。综上,文章提出的桥梁主梁转角抑振理念和伸臂阻尼系统的多模态阻尼减振控制效果良好。Long-span bridges are vulnerable to wind-induced vibrations due to their low-fre-quency and closely-spaced modes,small inherent damping,and the difficulty in damping improvement.The bridges can vibrate under low wind speed,in multiple modes,and for a long time,posing challenges in bridge design and operation.In this study,it is proposed to suppress vibrations of long-span bridges by supplementing rotational damping according to angular deflection of bridge girder.Furthermore,damped outriggers(DOs)are proposed to realize the concept.The multimode damping effects are first analyzed using a simplified ten-sioned beam model of a suspension bridge,considering main cable tension forces and girder bending stiffness of typical suspension bridges.It is found that one DO is capable of achie-ving a maximal modal damping of 0.8%.Influences of relative importance of girder bending stffness to main cable tension,outrigger stiffness,and outrigger location on the damping effects are investigated.With the Xihoumen Bridge in Zhoushan city taken as a study case,a finite element model(FEM)of the bridge with viscous DOs is established.Complex eigen-analysis is performed to appreciate damping,and parametric study is conducted using the FEM.It is shown that damping ratios of 6 out of 7 modes of the bridge suffering from vortex-induced vibrations can reach 0.98%when one rigid DO is installed between one tower and the bridge girder.When two DOs are installed respectively between two towers and the bridge girder,the damping ratios of the 6 modes can be overl.12%.It is suggested that to meet the requirements on the lateral stiffness of the outrigger at its lower end,the bending stiffness of outrigger shall be designed as twice the bending stiffness of girder in practical design.The results show that the proposed concept and the realization approach are effective for multimode vibration mitigation of long-span bridges.

关 键 词：大跨桥梁 伸臂阻尼系统 旋转阻尼 振动控制 阻尼比 

分 类 号：TU311.3[建筑科学—结构工程]