中央开槽箱梁颤振非线性特性和振动分叉现象及其机理  

Nonlinear characteristics of flutter and vibration bifurcation phenomenon of a centrally-slotted box deck and their mechanisms

作　　者：钱程 朱乐东[1,2,3] 朱青[1,2,3] QIAN Cheng;ZHU Ledong;ZHU Qing(State Key Laboratory of Disaster Reduction in Civil Engineering,Tongji University,Shanghai 200092,China;Department of Bridge Engineering,College of Civil Engineering,Tongji University,Shanghai 200092,China;Key Laboratory of Transport Industry of Bridge Wind Resistance Technology,Tongji University,Shanghai 200092,China)

机构地区：[1]同济大学土木工程防灾国家重点实验室,上海200092 [2]同济大学土木工程学院桥梁工程系,上海200092 [3]同济大学桥梁结构抗风技术交通行业重点实验室,上海200092

出　　处：《空气动力学学报》2023年第2期98-109,I0002,共13页Acta Aerodynamica Sinica

基　　金：国家自然科学基金重点项目(51938012);土木工程防灾国家重点实验室自主研究课题基金团队重点课题(SLDRCE19-A-15)。

摘　　要：为探究超大跨度缆索承重桥梁在大攻角范围内的颤振稳定性,通过节段模型风洞试验对中央开槽箱梁在风攻角±10°范围内的颤振非线性特性和振动分叉现象及其机理进行了研究。结果显示:当风攻角为-2°~10°时,节段模型系统未发生颤振;当风攻角为-3°和-4°时,观察到了含振动分叉的非线性颤振现象,且起振幅值随风速的增加而减小;当风攻角为-5°~-10°时,颤振无需人工激励就会自动发生。两种非线性颤振均为弯扭耦合颤振,并最终做极限环振动。非线性颤振的起振风速随着负攻角的增大而减小,耦合程度随着折减风速的增加而增加。系统等效阻尼比-振幅曲线可以很好地解释非线性颤振机理,曲线的零点为系统平衡点,其中斜率为正的零点为稳定平衡点,对应稳态振幅;斜率为负的零点为不稳定平衡点,对应起振振幅。对于含振动分叉的非线性颤振,系统存在一个稳定平衡点和一个不稳定平衡点;而对于无需人工初始激励的非线性颤振,系统只有一个稳定平衡点。In order to investigate the flutter stability of super-long-span cables supported bridges at large angles of attack(AoAs), the nonlinear flutter characteristics, vibration bifurcation phenomenon and mechanism of a centrally-slotted box deck with AoAs ranging between ±10° were investigated through wind tunnel tests of the sectional model. The results show that no flutter occurs for the sectional model system with AoAs between -2°~10°, nonlinear flutter with vibration bifurcation is observed with AoAs of -3° and -4°, and flutter appears automatically without any artificial initial excitation with AoAs between -5° ~-10°. Both kinds of flutter are coupled vertical bending and torsional motions and finally attain a stable state of the limit circle oscillation(LCO). The onset wind speed of such nonlinear flutter descends with the increasing absolute value of the negative AoA, and the coupling extent increases with the reduced wind speed. The mechanism of the nonlinear flutter can be well explained by the curve of the system damping ratio against the amplitude. With zero points of the curve representing equilibrium states of the system, a positive slope indicates the stable equilibrium,corresponding to the steady-state amplitude, and a negative slope for the unstable equilibrium and the onset amplitude. For the nonlinear flutter with vibration bifurcation, the system has one stable equilibrium point and one unstable equilibrium point, while for the flutter not requiring any artificial excitation, the system has only one stable equilibrium point.

关 键 词：中央开槽箱梁 节段模型风洞试验 非线性弯扭耦合颤振 平衡点与分叉 极限环振动 

分 类 号：U441.3[建筑科学—桥梁与隧道工程] V211.3[交通运输工程—道路与铁道工程]