Mechanism and reduction for wind induced damage of buildings

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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