Study on unsteady air force on low-rise buildings and numerical methods for prediction of wind load for wind resistant design

本文针对低层建筑的风特性和风荷载的数值计算方法进行了研究，首先利用现场实测资料对低层建筑的风特性进行了研究。在较强的风中，2.4米立方体周围的湍流统计的空间变化进行了评估，并在墙壁和屋顶上的相关风压进行了调查。结果表明，在高度H、立方体高度和水平距离0.9H处，流向分量的迎风速度脉动与迎风壁面和屋顶迎风部分的压力有较强的相关性。在研究期间袭击了日本。研究了2001年几次台风袭击、2004年冲绳县宫古岛0314号台风和2004年广岛县宫古岛0418号台风造成的灾害。极端的破坏，如完全倒塌的房屋，正在减少，但屋顶或覆层的破坏并没有减少。本文通过对城市低层建筑物的研究，认为正确预测近地面风场和城市近地面风场特性，对低层建筑物的抗风设计具有重要意义。介绍了一些引入表面粗糙度影响的湍流模型的数值方法，例如k-ε方法和LES，用于预测强风条件下城市地区的风场。并采用PSU/NCAR MM 5数值预报方法对台风引起的大风进行了预报。

We studied the wind characteristics of surface layer and the numerical methods for the prediction of wind load for wind resistant design of low-rise buildings.For the beginning, the wind characteristics of surface layer was studied using field experimental data. The spatial variations of turbulence statistics around the 2.4m cube were evaluated during rather strong winds and the correlated wind pressures on the wall and the roof was investigated. The results show that the upwind velocity fluctuations of streamwise component at a point with the height H, height of the cube, and the horizontal distance 0.9H from the cube have a rather strong correlation with the pressures on the upwind wall and the upwind portion of the roof.On the other hand, we also conducted field investigations of strong wind damage caused by typhoons and tatsumaki, tornado, struck Japan during the period of this study. The damages caused by some tatsumakis in 2001, by Typhoon 0314 struck on Miyakojima Island Okinawa prefecture in 2004 and by Typhoon 0418 struck on Miyajima Island Hiroshima prefecture in 2004 were studied. The extreme damage, such as completely failed houses, is decreasing but the damage on the roof or claddings is not decreasing. The secondary damage by flying debris, such as piece of broken roof tile or glass or gravels and so on, and the human damage are still large in number.Following above mentioned studies, it was resulted that the proper prediction of approaching wind and of wind characteristics in the urban areas near the ground is important for the wind resistant design of low-rise buildings. We showed some numerical methods using turbulent models introducing the effect of surface roughness, such as k-ε method and LES, for predicting the wind flow in the city areas for strong wind condition. Also the numerical method using PSU/NCAR MM5 was adopted to predict the strong wind caused by typhoon.