中央稳定板对桁架梁断面颤振性能的影响及其作用机理

Influence of central stabilized plate on flutter performance of truss beam section and its action mechanism

桁架梁断面在大跨度悬索桥建设中具有广泛的应用,但其截面形式较钝而气动性能较差。中央稳定板是一种常用的气动措施,为研究其对桁架梁悬索桥颤振性能的影响与作用机理,以赤水河大桥为研究对象,通过自由振动风洞试验详细测试了在不同风攻角下节段模型有中央稳定板与没有中央稳定板时的颤振响应,并基于试验数据提取了振幅依存的模态阻尼与颤振导数A_(2)^(*)。试验结果表明:中央稳定板能显著提升断面的颤振性能,降低竖向自由度在颤振中的参与程度;加上中央稳定板之后,系统颤振性能的提升主要来源于模态阻尼中非耦合项气动正阻尼的增加,而非耦合项气动正阻尼的增加是因为中央稳定板改变了A_(2)^(*)的变化规律,使之不存在由负转正的情况,始终不能提供气动负阻尼,在正攻角下A_(2)^(*)的这种改变最为显著。

Truss beam section is widely used in the construction of long-span suspension bridges,but its section form is blunt and its aerodynamic performance is poor.Central stabilized plate is a kind of aerodynamic measure.In order to study the effect and mechanism of central stabilized plate on flutter performance of truss beam suspension bridges,free vibration wind tunnel tests were conducted on Chishui River Bridge in detail to test flutter response of segment models with and without central stabilized plate under different wind attack angles.The amplitudedependent modal damping and flutter derivative A_(2)^(*)were extracted based on the test data.The experimental results show that the central stabilized plate can significantly improve the flutter performance of the section and reduce the participation of vertical degrees of freedom in the flutter.After the central stabilized plate is added,the improvement of flutter performance of the system mainly comes from the increase of uncoupled positive aerodynamic damping of the modal damping.The reason of the increase of uncoupled positive aerodynamic damping is that the stabilized plate changes the change law of A_(2)^(*),so that it does not change from negative to positive and cannot provide negative aerodynamic damping all the time.The change of A_(2)^(*)is most significant under positive attack angle.