台风外围影响下的大跨度拱桥桥址区近地风特性实测研究

Field Measurement and Investigation of Wind Characteristics at the Site of a Long-span Arch Bridge in the Periphery of Typhoon Kujira

基于南广铁路肇庆西江特大桥风速风向监测子系统,对2015年6月台风"鲸鱼"气候条件下的平均风速、平均风向以及脉动参数(紊流强度、阵风因子、紊流积分尺度、脉动风速功率谱等)开展实测研究.结果表明:台风外围影响下1min平均风速波动幅度较大,呈现出跳跃性;实测紊流强度离散性较低,纵向紊流强度实测值0.253,紊流强度和阵风因子有随平均风速的增大而减小的趋势特征,且该趋势在低平均风速段更为明显;各方向上紊流积分尺度与规范相应推荐值差别较大,流场中主要以中小尺度涡旋为主,其离散度随平均风速的增加略有增大;规范推荐的Kaimal谱与实测水平向脉动功率谱函数并不能很好地符合,台风"鲸鱼"在低频段和高频段的谱值均偏高.实测表明台风外围风场具有一定相关性,采用Davenport假设会带来一定误差.

Based on the structural health monitoring system （SHMS） installed on Xijiang Bridge of Nanning-Guangzhou Railway, the whole-process data of the wind speeds and directions at the bridge site subjected to Typhoon Kujira in June 2015 were obtained. Utilizing the measured data, the mean wind speeds, mean wind directions, and fluctuating wind parameters including the turbulence intensity, gust factors, turbulence integral scales, power spectrum density （PSI）） of fluctuating wind and spatial correlation in different observing points were summarized and statistically analyzed. The analysis results showed that 1-minute mean wind speeds fluctuated in a large margin in the typhoon periphery, and the distribution of measured turbulence intensity exhibited a low discreteness with a longitudinal value of 0. 253. Both the turbulence intensity and gust factors decreased with the increase of the mean wind speed. Moreover, large differences between the measured turbulence integral scales and recommended ones in three principal directions were observed. Meso-micro scale vortexes dominated the flow field, whose dispersion slightly increased with the increase of the mean wind speed. Additionally, the Kaimal Spectrum obtained from the relative codes cannot match well the measured horizontal PSI） functions,and the measured spectrum value of Typhoon Kujira was greater than those of the codes in both high and low frequency domains. The spatial correlation was apparent in the periphery, and the error was caused when the Davenport assumption was adopted.