Mechanism and reduction for wind induced damage of buildings

本课题的研究目的是寻求一种合理的抗风设计措施，以减少建筑物及其围护结构在强风作用下的破坏。本课题主要进行了以下几个方面的研究：第一，研究自然风作用下高层建筑的风压脉动特性;通常认为，在台风作用下，绝大多数的复合材料损伤都是由阵风引起的，而阵风的非平稳特性是很难在风洞中模拟的。在京都大学盐之崎风效应研究室的野外试验场中设置了一个大比例尺的高层建筑模型，测量了在季节性强风和台风中的墙体压力脉动。分析表明，压力系数应在与建筑物周围流态形成有关的适当时间尺度内进行评估，而不是在分析建筑物周围流态时通常使用的10分钟平均周期。 关于我们 气象记录这种短时风压可以结合风洞试验中获得的台风等非平稳风场的实测资料，用于计算建筑物的峰值风荷载。第二项研究是关于屋面瓦在强风中的飞散。80%以上的风致破坏发生在屋顶。特别是，屋顶瓦片很容易被强风吹散。在自然风中，使用设置在实验室场地中的实验房屋测量屋顶瓦片的表面上的压力和瓦片背面的板条空间中的压力。当垂直于根部的风袭击时，由于瓦的外部和内部的压力大的不平衡，导致瓦上的最大峰值升力。另一方面，在侧屋顶和背风屋顶上的瓦片的升力不是那么大，即使当大的局部峰值吸力作用在瓦片的表面上时，因为大的峰值吸力与瓦片的背压平衡。这一发现与强风破坏观测报告中迎风面屋顶的许多瓦片在强风中散落的情况相吻合。第三个调查是台风中强风破坏的观测。一栋建筑物的大屋顶被吹掉，挂在新东海道线的架空电线上，新干线停运7小时。屋顶是一个修复的屋顶覆盖在旧屋顶上。可以看出，风险和损失的类型相当高。失败的原因是对细节的投资。另一种类型的损坏是屋顶上的长钢板散落。这种损坏与面板的内压和固定电压的疲劳有关。历史建筑再次受到台风的严重破坏，特别是来自山谷的下流。这种强烈的下沉气流在台风中经常出现，造成严重的损失。其中一个原因是拓扑效应，数值模拟证实了这一点。少

The aim of the research project is to find a rational wind resistant design measure for a reduction of damage of buildings and their claddings induced by strong winds. The several investigations were carried out for the project.The first research is to investigate characteristics of wind induced pressure fluctuation on a tall buildings in natural winds. It is often pointed that most of severe damages of claddings in typhoon winds were caused by a strong gust, of which characteristics is very non-stationary and can not be simulated in a wind tunnel. A large scale tall building model was set in the field in Shionomisaki Wind Effect Laboratory of Kyoto University and pressure fluctuations on walls were measured both in seasonal strong winds and typhoon winds. The analysis shows that the pressure coefficient should be evaluated in a proper time scale related with formation of a pattern of flow around the building instead of the ordinary 10 minute averaging period used in the analysis of a … More meteorological record. This short time pressure can be used for the evaluation of the peak wind loads combined with the non stationary wind data like in a typhoon wind, which can be obtained in wind tunnel experiment in the same time scale.The second research is related with the scattering of the roof tiles in strong wind. More than 80% of wind induced damages occurs at roofs. Particularly, the roof tiles can be easily scatted by strong winds. Pressures on a surface of a roof tile and in a batten space back of the tile were measured in natural winds, using an experimental house set in the field of the laboratory. The maximum peak lift force on the tile induced when wind attacks normal to the root, because of the large unbalance of pressures on the outside and the inside of the tile. On the other hands, the lift forces of the tile on the side and leeward roofs were not so large even when the large local peak suction acted on the surface of the tiles, because the large peak suction balanced to the back pressure of the tile. This findings agrees well with reports of damage observation by strong wind in which many tiles on the windward roof were scatted in strong winds.The third investigation is observations of damages by strong wind in typhoons. A large roof was blown off from a building and hanged on the overhead wire of New Tokaidou Line and Sinkansen stopped for 7 hours. The roof was a repaired roof covered on the old roof. It can be noticed that the type of the risk and the loss is fairly high. The cause of the blown off was investment in details. The other type of damage is the scattering of the long steel panel on the roof. This type of the damage is related with the internal pressure back the panel and the fatigue of the fixed volt. The historical structure were again suffered severe damages by typhoon wind, particularly the down flow from the valley. This type of the strong down flow were often observed in typhoons, and causes severe damage. One of the cause is a topological effect, which is convinced by the numerical simulation. Less