地表粗糙度对高层建筑下击暴流风荷载特性影响的试验研究

Tests for effects of terrain roughness on wind load characteristics of a high-rise building under downburst

地表粗糙度对近地层的风场影响很大。为研究下击暴流风场中不同粗糙度地貌上的高层建筑表面风压变化规律,基于冲击射流试验,讨论了地表粗糙度与径向距离不同情况下高层建筑表面风压特性。试验结果表明:建筑迎风面风压极值区的高度随地表粗糙度的增大而逐渐抬升,迎风面正风压系数也随之增大,背风面负风压绝对值随之减小,侧面风压系数受粗糙度影响变化不明显;建筑侧面脉动风压系数随地表粗糙度的增大而增大,而迎风面和背风面的脉动风压系数受粗糙度影响较小。随着径向距离及地表粗糙度的增大,出流强度衰减明显加快,建筑迎风面中下部区域风压系数衰减较大,背风面及侧面风压系数逐渐减小,且背风面呈线性衰减趋势。

Terrain roughness has a great influence on wind field in near-surface layer. Here, to investigate variation laws of wind pressure on surfaces of a high-rise building on different roughness landforms in downburst wind field, based on impact jet tests, the wind pressure characteristics on the high-rise building’s surface were discussed under conditions of different terrain roughness and radial distances. The test results showed that with increase in terrain roughness, the height of the wind pressure extreme value area on the building’s windward side gradually rises, and the positive wind pressure coefficient on the windward side also increases, while the absolute value of negative wind pressure on the leeward side decreases;terrain roughness affects lateral wind pressure coefficient not obviously;the building’s lateral fluctuating wind pressure coefficient increases with increase in terrain roughness, while terrain roughness affects fluctuating wind pressure coefficients on the windward and leeward sides weakly;with increase in radial distance and terrain roughness, outflow intensity attenuation is accelerated apparently, wind pressure coefficient on middle and lower parts of the windward side decays largely, wind pressure coefficients on the leeward side and lateral side gradually decrease, and the former has a linear attenuation trend.