高层建筑顺风向脉动荷载相干性研究

Coherence analysis of along-wind fluctuating loads on high-rise buildings

在确定高层建筑顺风向风致响应及等效静力风荷载时,顺风向荷载的竖向相干函数是非常重要的因素之一。目前的大多数研究均是以风速的相干函数来代替风压的相干函数,导致计算结果的误差较大。根据多个高层建筑模型表面测压风洞试验结果,详细分析高层建筑脉动阻力在B、D两类风场中的竖向相干特性,给出顺风向阻力竖向相干函数衰减指数CDz的公式,并与有关文献中提出的Davenport、Shiotani、ECCS等三种风速相干函数的表达公式进行比较,指出阻力相干性要明显大于风速相干性。结合准定常理论,计算一栋实际高层建筑的顺风向风致响应。结果表明:利用给出的阻力竖向相干函数得到的结果与根据风洞试验数据计算的结果相吻合,而其他几种表达公式导致的响应误差则较大,最大可达30%。

The vertical coherence function of windward loads on high-rise buildings is one of the pivotal factors for calculating the wind-induced response of the equivalent static wind load on high-rise buildings. Up to date the coherence function of wind pressure is often replaced by that of wind velocity, which however could introduce significant errors. In this study, several high-rise building models are tested in a wind tunnel to get the wind pressures on the buildings. The drag force coherence in the vertical direction of high-rise buildings in terrain category B and D is analyzed in details and a rational formula for CDz is proposed. It is shown that the wind pressure coherence is larger than the wind velocity coherence. With the quasi-steady theory, the coherence function proposed here and the coherence formulae by Davenport, Shiotani, and the ECCS formula are used to calculate the windward response of a high-rise building. It is shown that the responses using the present coherence function agree with those from the wind tunnel experiments, while the other wind velocity coherence formulae result in larger errors as high as 30%.