Scruton数对小宽高比H型断面典型攻角风致振动的影响

Influence of Scruton number on wind‑induced vibration of H‑section with a small side ratio under large wind angles of attack

驰振是一种易发于细长钝体构件的横风向气动失稳现象,质量阻尼参数是影响结构驰振特性的关键参数之一。为探究质量阻尼参数对小宽高比H型断面驰振的影响规律,本研究以曾家岩嘉陵江大桥H型吊杆为工程背景,针对宽高比B/D=1.91的H型断面进行节段模型风洞试验,得到典型风攻角下驰振响应特征,并分别研究了质量、阻尼参数变化所引起的Scruton数变化对大攻角驰振响应的影响规律,探讨了Scruton作为单一参数描述质量阻尼参数影响的可行性。试验结果表明:宽高比B/D=1.91的H型截面在风攻角0°和70°出现非定常大振幅驰振,当Scruton数增大,70°攻角的驰振振幅-风速曲线变化较0°攻角更显著;攻角0°和70°下的驰振临界风速均低于准定常理论值,采用经典准定常理论预测结果偏于危险,0°攻角相较70°攻角的起振风速更低,更容易发生风致振动,并且非定常驰振现象显著;阻尼比和质量比对不同风攻角下驰振的影响不同,在风攻角0°下,两者可近似由Scruton数统一表示,但在大攻角70°下,不能简单地由Scruton数表示。

Galloping is a kind of transverse aerodynamic instability phenomenon to which slender prismatic structures are prone un⁃der wind actions,and the mass damping parameter is a key factor in determining the galloping response.The present study aims to explore the influence of the mass damping parameter on the galloping of the H-shaped section with a small side ratio(width-todepth ratio as B/D=1.91).By taking the H-shaped hanger of the Zengjiayan Jialing River Bridge as the prototype,this study inves⁃tigates the galloping response under the typical wind attack angles,based on the wind tunnel segmental model test of an H-shaped section with a side ratio B/D=1.91.The effect of the change of Scruton number caused by the mass and damping parameters is then examined on the galloping response under large wind attack angles.Finally,the feasibility of Scruton as a single parameter is discussed to describe the influence of mass damping parameter.The results demonstrate that the H-shaped section with a side ratio B/D=1.91 shows unsteady galloping with large amplitude at the attack angles of 0°and 70°,and compared with 0°attack angle,the change of galloping response at the attack angle of 70°is more sensitive as the Scruton number increases.The onset wind speed of the galloping is,at the attack angles of 0°and 70°,lower than that calculated by the classical quasi-steady theory,which is high and dangerous.Compared with 70°attack angle,the wind-induced vibration at 0°attack angle is more likely to occur due to its low⁃er onset wind speed,and has significant unsteady galloping.The mass ratio and damping ratio have different effects on the gallop⁃ing at different wind angles of attack.At the attack angle of 0°,the two can be uniformly represented by the Scruton number,but at a large attack angle of 70°,they cannot be accurately represented by the Scruton number.At last,some topics deserving further re⁃search are highlighted.