风屏障对流线型箱梁涡振性能影响机理试验研究

为研究风屏障透风率对主梁涡振性能的影响,依托某主跨808 m大跨度钢箱梁悬索桥,通过风洞测振、测压试验得到模型风致振动响应和表面各测点压力时程数据.测试原桥断面在加设风屏障后±5°攻角范围内的涡振性能,对比分析原桥断面和3种不同透风率风屏障以及安装水平分流板5种工况下主梁涡振响应和桥面各测点脉动压力系数均值、根方差;同时分析局部气动力与总体气动力的相关性和贡献作用.研究结果表明,原断面在+5°攻角下发生了多区间竖弯涡激振动,且涡振振幅远超规范允许值.安装不同透风率的风屏障后对主梁的涡激共振产生了有利的影响,消除了主梁原断面在低风速区间的涡振,最大振幅也有一定的减小.根据测得的压力数据分析,带风屏障主梁上表面中后部压力脉动减弱及局部气动力与总体气动力贡献系数减小使得主梁振幅有了小幅减小;在主梁风嘴处添加水平分流板后,局部气动力与总体气动力的相关性被完全破坏,压力脉动减弱,从而有效地抑制了主梁在该情况下的涡振.

Experimental Study on Influence of Wind Barrier Permeability on Characteristics of Main Girder Vortex-induced Vibration

In order to study the influence of air permeability of wind barrier on vortex-induced vibration performance of the main girder, based on a long-span steel box girder suspension bridge with 808 m main span, wind-induced vibration response and pressure time history data of each measuring point on the surface were obtained by wind tunnel vibration measurement and pressure measurement test. The vortex vibration performance of the original section was measured within the range of ± 5 ° angle of attack after the wind barrier was added. The vortex vibration response performance of the main girder, the mean value and root variance of the fluctuating pressure coefficient of each measuring point on the bridge deck, the correlation and contribution coefficient between local aerodynamic force and overall aerodynamic force were compared and analyzed among the original section as well as three different ventilation rates and five conditions of water adding horizontal splitter plates. The results show that multi-interval vertical bending vortex-induced vibration occurs on the original section at + 5 °angle of attack, and the amplitude of vortex-induced vibration is far beyond the allowable value in the code. The vortex-induced resonance of the main girder is affected by the wind barrier with different air permeability, which eliminates the vortex-induced vibration of the original section of the main beam in the low wind speed range, and the maximum amplitude is also reduced to a certain extent. According to the analysis of the measured pressure data, the pressure fluctuation of the middle and rear part of the main beam is weakened, and the contribution coefficients of the local aerodynamic force and the overall aerodynamic force are reduced, which makes the amplitude of the main beam decrease slightly; after the horizontal splitter plate is added at the wind nozzle of the main beam, the correlation between the local aerodynamic force and the total aerodynamic force is completely destroyed, and the pressure fluctuation is weakened, which effectively suppresses the vortex induced virbration of the main beam in this case.