宽幅双箱叠合梁涡振性能及抑振措施试验研究

叠合梁断面通常为气动外形较钝的半开放截面，为漩涡的产生和发展提供了条件，容易发生涡激振动现象。过大振幅的涡激振动会影响行车舒适性，严重时将引起结构疲劳破坏，危及桥梁结构安全。如何有效解决涡激振动问题成为叠合梁桥抗风设计的关键。为了抑制该类主梁断面的涡激振动，以宜宾盐坪坝长江大桥为背景，通过1：60的节段模型风洞试验，研究了风嘴、中央稳定板、封闭栏杆、裙板、内侧隔流板、箱梁下导流板等常见措施对双箱叠合梁断面涡激振动性能的影响。研究结果表明：封闭斜拉索防护栏杆、内侧隔流板、梁底稳定板等措施均可不同程度地降低主梁的涡振振幅，但仍无法满足桥梁的抗风设计要求；竖直裙板可以使-3°和0°攻角下主梁的涡激振动消失，但对3°攻角的减振效果有限；在叠合梁中应用广泛的传统整体式风嘴无法降低宽幅双箱叠合梁的涡振振幅；采用安装在箱梁侧下方的三角形风嘴可以减弱箱梁边缘的流动分离，优化梁体的气动外形，从而使断面在各个风攻角下的涡振振幅大幅降低。将三角形风嘴与封闭斜拉索防护栏杆的方案组合后，可进一步降低主梁的涡振振幅，满足抗风设计的要求。所提出的叠合梁涡振抑振措施具有较好的工程适用性，可为同类桥梁的抗风设计提供借鉴。

Experimental Study on Vortex-induced Vibration Performance and Aerodynamic Countermeasures for a Wide-width Double-box Composite Beam

A composite (edge-girder) beam is an open cross section with bluff body characteristics. This type of beam can aggravate the generation and development of vortices and is prone to vortex-induced vibrations (VIVs). Large amplitude VIVs can affect the comfort of users, more importantly, cause structural fatigue damage and even lead to eventual collapse. Therefore, mitigating VIVs is the most critical issue in the wind-resistant design of composite beam bridges. To suppress the VIVs of composite beams, a cable-stayed bridge with a wide-width double-box composite beam was taken as an engineering example. A series of section model tests with a scale of 1:60 were conducted in a wind tunnel. The effects of some wide used countermeasures such as the installation of wind fairings, guiders, baffle, edge, and horizontal flow-isolating (HFIPs) plates; and increased porosity of railing on the VIV performance of the composite beam were closely investigated. It was found that some countermeasures such as sealing the stay cable protective railing and installing HFIPs and baffle plates can reduce the VIV amplitude of the beam at varying angles of attack. However, the VIV amplitude still does not meet the requirements of Chinese bridge design codes. An edge plate can significantly improve the VIV performance at angles of -3° and 0°, whereas it is not functional at 3°. Triangular wind fairings installed on the sides of longitudinal boxes can reduce the flow separation at the edge of the box girder and optimize the aerodynamic shape of the section, and the VIV amplitude of the section under each angle of attack is considerably reduced. In addition, the VIV amplitude of the beam can be considerably reduced by simultaneously installing triangular wind fairings and sealing the stay-cable protective railing, thereby meeting the requirements of Chinese bridge design codes. These proposed countermeasures are effective for engineering practice and could provide a reference for the wind-resistance design of similar bridges.