下击暴流作用下大跨度平屋盖结构的风荷载分布特性

Wind Load Distribution Characteristics of Long-span Flat Roof Structure Under Downburst

摘要:

应用一种下击暴流发生装置，在大气边界层风洞内模拟了适用于大跨度屋盖风洞试验的1∶300比例下击暴流风场。在此基础上，对下击暴流作用下大跨度平屋盖结构的风压分布特征进行了风洞试验，并与常规B类地貌的相应试验结果进行对比。结果表明：在模型区内，下击暴流发生的相对位置对风压系数的影响整体较小；下击暴流作用下平均风压分布与B类风场下的结果基本一致，但极小风压系数绝对值最大值9.85比B类风场的5.54超出77.8%，并且相应脉动风压的功率谱显著高于B类风场的试验结果；B类风场下平屋面的极大风压系数最大值均接近或小于0，但不同风向角的下击暴流风作用下高于0.15的极大风压系数所占的屋盖面积比例处于51%到75%的范围之间，极大风压系数局部最高可达0.35，大范围的较高正压会进一步影响结构的承载力。

关键词:下击暴流;风洞试验;大跨度平屋盖;风压分布;风场特性

Abstract:

Based on an experimental apparatus for downburst simulation， a 1∶300 downburst wind field suitable for the wind pressure distribution test of a long-span flat roof structure was simulated in the atmospheric boundary layer wind tunnel. On this basis， the wind pressure distribution characteristics of the long-span flat roof structure under downburst were studied， and were compared with the corresponding test results in exposure category B. The results show that in the model area， the relative position of downburst has little effect on the wind pressure coefficients； the average wind pressure distribution under downburst is basically the same as that in exposure category B， but the maximum absolute value of minimum wind pressure coefficient reaches 9.85， and is 77.8% higher than 5.54 in exposure category B； the corresponding power spectrum of fluctuating wind pressure is significantly higher than that in exposure category B； the maximum wind pressure coefficients of flat roof in exposure category B are close to or less than 0. However， in different wind directions under downburst， the ratios of the roof area with the maximum wind pressure coefficients over 0.15 are between 51% and 75%， and the local maximum wind pressure coefficient reaches 0.35； the high positive pressure in a large area will further affect the bearing capacity of the structure.

Key words:downburst;wind tunnel test;long-span flat roof;wind pressure distribution;wind field characteristics