塔冠对方形超高层建筑顺风向基底弯矩的影响研究

高层建筑顶部塔冠形状多样，其对建筑整体气动力的影响目前尚不明确。为此，利用高频测力天平技术，在大气边界层风场下对19种不同顶部塔冠的方形截面超高层建筑进行了风洞试验，分析塔冠形状对超高层建筑顺风向基底弯矩系数值及顺风向基底弯矩功率谱的影响。讨论坡面变化、顶部开洞、阶梯变化和锥形变化等四大类塔冠形状对结构整体顺风向气动力的影响规律。试验结果表明：将坡面置于迎风侧能够降低顺风向基底弯矩系数值；相同开洞形状和面积时，顶部敞口开洞对降低顺风向基底弯矩平均值的效果优于闭口开洞；斜坡面阶梯塔冠对降低顺风向弯矩系数值的效果优于直坡面阶梯塔冠；上棱椎下棱台的棱椎式塔冠能够大幅减小顺风向基底弯矩系数平均值。塔冠能够改变顺风向基底弯矩功率谱峰值大小，棱锥形塔冠对降低顺风向弯矩功率谱峰值最为明显。

Effects of tower crown on along-wind base moment for square super high-rise building

The effects of crown on aerodynamic forces for high-rise buildings are still unclear due to the variety of crowns on the top of the building. The wind tunnel tests using high-frequency balance force measurement were carried out on 19 kinds of crowns of the square-section high-rise buildings under atmospheric wind field condition. The influence of crown on the along-wind base moment coefficient and the corresponding power spectrum were analyzed. The effects of four types of crown, including the stepped crown, the top opening crown, the sloped crown, and the cone crown, on the along-wind aerodynamic force were discussed. The results show that the along-wind base moment can be reduced when the slope faces the approaching wind. For the top opening crowns, the average along-wind base moment on the crowns with closed opening is smaller than that on the non-closed opening in the same shape and area of the opening. The stepped tower crown on the slope surface is better than the straight slope in reducing the along-wind base moment. The prismatic tower crown with a combination of a pyramid on top and a frustum of pyramid at bottom can notably reduce the mean along-wind base moment coefficient. The crowns also change the peak value of spectrum of the along-wind base moment coefficient. The pyramidal crown can significantly reduce the peak value of the spectrum.