宽高比4.3流线型箱梁的涡激振动机制

Study on the Vortex-induced Vibration Mechanism of Streamlined Box Girder with Aspect Ratio 4.3

通过节段模型风洞试验分析宽高比4.3流线型箱梁断面的涡激振动性能,基于数值模拟分析静止及振动断面周围的绕流结构,探讨流线型箱梁涡激振动机制。结果表明:+5°攻角时,宽高比4.3断面涡激振动竖向无量纲最大振幅为0.0135,是+3°攻角的2.2倍。涡激振动机制为:气流在桥面板处分离后,产生一定尺寸的上部漩涡,随着漩涡沿桥面板运动,其尺寸不断增大,并在桥面板背风侧发生分离脱落,振动断面周围的上部漩涡更加完整,且存在5个尺寸相对较大的漩涡,而下部漩涡在背风侧风嘴下斜腹板处的尺寸与数量有一定程度的增加;振动幅值增大后,主梁尾流宽度增大,脉动强度有一定程度增强。研究结果可供流线型箱梁抗风设计参考。

An investigation into the vortex-induced vibration(VIV)performance of a streamlined box beam section with an aspect ratio of 4.3 is conducted through a sectional model wind tunnel test.Based on numerical simulation analysis,the flow pattern around the stationary and oscillating girder section are examined to explore the inherent mechanism accountable for the VIV of streamlined box beam sections.The results show that at wind attack angle+5°,the maximum nondimensional vertical VIV amplitude is 0.0135,which is approximately 2.2 times greater than that at wind attack angle+3°.The mechanism of vortexinduced vibration is that the airflow separates at the windward edge of the bridge deck,producing upper vortices of specific dimensions,and as the vortices travel along the bridge deck,their dimensions continually increase,and then they separate and become detached at the leeward edge of the bridge deck.The upper vortices surrounding the vibrating section are more complete,with 5 relatively larger vortices present.The vortices on the leeward side of the inclined web plate demonstrate an increase in size and quantity.As the vibration amplitude increases,the width of the main girder’s wake enlarges,and the fluctuation intensity experiences a certain degree of enhancement.The research findings can serve as a reference for the wind resistance design of streamlined bridge main beams with similar characteristics.