类矩形双肢钝体涡致振动和气动抑振机理

针对具有类矩形双肢钝体断面拱肋的大跨度拱桥在风洞试验过程易出现大幅涡激振动问题，沿拱肋模型表面进行动态风压同步测量及基于POD算法的本征气动力荷载分布模式分解，获得了涡振发生时对于周期性涡激力具有最大贡献的气动力荷载作用位置，初步揭示出此类断面涡激动发生时的局部气动力荷载作用机制。以上海卢浦大桥和肇庆西江特大桥此类具有双肢钝体断面拱桥为工程实例，结合涡激气动力沿拱肋周向时空气分布特征，提出并以二维悬吊节段模型风洞试验验证了拱肋断面多种有针对性的气动控制措施；结合实际桥梁拱肋的三维空间效应，利用全桥气弹模型风洞试验再现了涡振发生效果的气动力特征、阻尼比效应、三维尺寸渐变效应和质量分布效应的综合影响，结果表明：对于类矩形钝体拱肋断面的上下悬板方案和全盖板方案能大幅度降低涡振振幅并使锁定风速区间向高风速段迁移，但实际涡振抑制效果仍需结合三维模型气弹试验最终判断。

Vortex Shedding-induced Vibration and its Mitigation of Two-rib Bluff Body with Rectangular Shape

In wind tunnel test, arch ribs with two-rib rectangular shape of long-span arch bridges are prone to large vortex-induced vibration （VIV）. Based on analyzing the distribution of the arch rib surface aerodynamic pressure, the relationship between the pressures distribution and the periodic vortex-induced force is gained by POD method and the mechanism of the local vortex excited aerodynamic loading is initially revealed. Taking Lupu arch bridge and Zhaoqing Xijiang grand arch bridge as technical examples, with the help of aerodynamic characteristics of pressures distribution around rib surface, especially the dominant vortex excited areas determined by surface pressure measurement tests about two-dimensional sectional model, this paper proposed control measures for the rib section significantly reducing amplitude of vortex-induced vibration, and mitigation effects were successfully re-illustrated. Finally, the vortex related aerodynamic vibration characteristics, damping effect, the three-dimensional gradient effect and the effect of the combined effects of mass distribution were further investigated utilizing full aero-elastic bridge model. Some conclusions are reached that the solution of suspension plate just at the place of upper and lower arch lib or fully covering plate can both sharply reduce amplitude of vortex-induced vibration and increase onset wind speed of lock-in region ; VIV suppression effects should be re-examined combined with three-dimensional full aero-elastic model.