风攻角对流线型主梁涡振特性影响的试验研究

EXPERIMENTAL STUDY ON THE INFLUENCE OF WIND ATTACK ANGLE ON VORTEX-INDUCED VIBRATION CHARACTERISTICS OF STREAMLINED GIRDERS

涡激振动是主梁在低风速下常发生的一种振动,可能造成主梁疲劳破坏或影响行车舒适性。为了研究风攻角对流线型箱梁涡激振动特性的影响和作用机理,采用节段模型同步测压、测振的方法,分析了风攻角对涡激振动响应、平均和脉动风压、局部气动力对涡振的贡献系数的影响。结果表明:涡振振幅随风攻角的增大呈增大趋势;不同风攻角的上表面平均压力系数不同,在-5°风攻角时最大,在+5°风攻角时最小;当风攻角为正时,主梁上表面下游区域和下表面迎风侧斜腹板前端脉动压力系数波动较大,风攻角在一定程度上影响主梁表面脉动压力系数的空间分布,这可能是涡振响应不同的原因之一;风攻角对局部气动力贡献系数有一定的影响,当风攻角为正时,主梁表面气动力对涡激力有增强作用。

Vortex-induced vibration(VIV)is a kind of vibration that often occurs in the main girder under low wind speed,which may cause fatigue damage to the main girder or affect driving comfort.In order to study the influence and mechanism of wind attack angle on the VIV characteristics of streamlined box girder,the influence of wind attack angle on the response of VIV,the average and fluctuating wind pressure and the contribution coefficient of local aerodynamic force to VIV were analyzed using the method of synchronous pressure and vibration measurement of segment model.The results show that the amplitude of vortex vibration increases with the increase of wind attack angle.The average pressure coefficient of the upper surface at different wind attack angles is different,which is the largest at an attack angle of-5°and the smallest at an attack angle of+5°.When the attack angle is positive,the fluctuating pressure coefficient varies greatly in the downstream area of the upper surface of the main girder and the front end of the inclined web on the windward side of the lower surface.The wind attack angle affects the spatial distribution of the fluctuating pressure coefficient on the surface of the main girder to a certain extent,which may be one of the reasons for the different vortex vibration responses.The wind attack angle has a certain influence on the local aerodynamic contribution coefficient.When the wind attack angle is positive,the aerodynamic force on the surface of the main beam has an enhancement effect on the vortex-induced force.