П型断面主梁软颤振特性及抑制措施研究

Characteristics and Suppression Neasures for Soft Flutter of Main Girder with П-Shaped Cross Section

П型断面主梁为气动钝体结构,在非线性自激力作用下,极易发生软颤振现象.以某П型断面叠合梁斜拉桥为研究对象,通过节段模型风洞试验,研究了各种气动措施对П型断面主梁软颤振性能的影响.研究结果表明:П型断面主梁软颤振表现为弯扭自由度耦合的单频振动特征,且随着风速的增加,竖向振动参与度系数先减小后增大;安装风嘴可以增大系数,其振幅服从正态分布,振幅波动范围随风速及攻角变化而变化;风攻角为负时,П型断面主梁最易发生软颤振;设置桥面附属设施会提高软颤振的临界风速、减小软颤振的扭转振幅及振幅增长速率;设置风嘴会显著降低软颤振的振动响应,采用尖风嘴可以改善主梁的软颤振性能,且随着风嘴变尖,软颤振的临界风速有提高的趋势,软颤振扭转振幅有下降的趋势;П型断面主梁底部设置中央稳定板对其软颤振性能的影响不明显.

Main girder with FI-shaped cross section has aerodynamic blunt body structure, and under the nonlinear self-excited force, it is vulnerable to soft flutter. To study the effects of various aerodynamic measures on soft flutter performance of this main girder, the aerodynamic performance of a cable-stayed bridge was used through wind tunnel test of sectional model. The results show that soft flutter of the main girder is a coupled two-degree-of-freedom torsional-bending vibration with single frequency. With the increase of wind speed, the degree of vertical vibration decreases first and then increases. Setting wind fairings can increase the value of R. The amplitude of soft flutter follows a normal distribution, and the amplitude range varies with wind speed and angle of attack. Soft flutter is most likely to occur when the angle of attack is negative. Setting auxiliary facilities on the bridge deck can enlarge the critical velocity, and reduce the soft flutter amplitude and the amplitude growth rate. Setting wind fairings can reduce the vibration response of soft flutter, and the soft flutter performance can be improved by sharpening wind fairings. With the wind fairing angle sharpening, the critical velocity of soft flutter tend to rise but the amplitude of soft flutter tend to fall. Setting the central stabilizer at the base of the bridge deck has a m unobvious effect on the soft flutter performance of the main girder.