栏杆封闭气动措施对桥梁涡振特性的影响

Influence of Aerodynamic Measures for Railing Closure on Bridge Vortex-induced Vibration Characteristics

为了研究栏杆封闭气动措施对桥梁涡激振动特性的影响,通过改变外侧栏杆开敞、封闭型式,形成4个断面模型进行风洞试验,测量各断面风速与振幅的关系。对比分析4个断面涡振振幅最大试验风速时的响应,研究栏杆封闭气动措施对典型桥梁断面涡振特性影响的作用机理。结果表明:3种封闭栏杆的气动措施断面均能有效抑制主梁的涡激共振。竖弯涡振产生的根本原因是上表面下游及下表面的强烈脉动压力,局部气动力与总体气动力的高度相关性,各测点脉动压力具有相同的卓越频率,脉动压力功率谱较大,各测点竖弯频率上所携带的能量较大。封闭栏杆气动措施抑制竖向涡激振动的原因是上表面下游及下表面的脉动压力削弱,局部气动力和总气动力间相关性的降低以及局部气动力对涡振的贡献程度减小,各测点能量在卓越频率上的离散,脉动压力功率谱减小,携带的能量趋近于0。

To study the influence of aerodynamic measures for railing closure on the vortex-induced vibration characteristics of bridges,the wind tunnel tests were conducted by changing the opening and closing types of outer railings to form 4 section models.The relation between wind speed and amplitude of each section was measured.The response of 4 sections at the maximum test wind speed were compared.The mechanism of railing closure influence on the vortex characteristics of typical bridge sections was studied.The result indicates that the vortex-induced resonance of main beam can be effectively suppressed by 3 aerodynamic sections of closed railings.The root cause of vertical bending vortex vibration is the strong pulsating pressure on the downstream and lower surface of upper surface.There is a high correlation between local and total aerodynamic force.The pulsating pressure of each point has the same excellent frequency.The pulsating pressure power spectrum is large,and the energy carried by the vertical bending frequency of each point is large.The reason for suppression of vertical vortex-induced vibration with aerodynamic measures of closed railings is that the fluctuating pressure on the downstream and lower surfaces of upper surface is weakened.The correlation between local and total aerodynamic force is reduced.The contribution of local aerodynamic force to vortex-induced vibration is reduced.The energy of each point is discrete at the predominant frequency,the power spectrum of fluctuating pressure is reduced,and the energy carried is close to zero.