Reponse of a building induced by an abrupt gust

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Buildings and houses are often damaged by an abrupt gust during a typhoon wind. Wind speed suddenly increase to double or three times of the mean wind speed and then decrease gradually in several seconds in such a gust. However, wind load induced by such a abrupt gust is not described in codes of practice in which it is assumed that wind blows stationary in a relatively long time. ln this research, characteristics of the wind load induced by the abrupt gust are investigated by wind tunnel tests and responses of buildings during the gust are investigated by numerical analysis in time series mainly from the following two points of view, 1) To simulate an abrupt gust in a wind tunnel, 2) To clarify a mechanism of a wind loading due to the gust, 3) To make model gust gust loads, 4) And to calculate the response of building induced by the model gust load.In order to simulate the gust, we set a fence at a position far from a building model. By adjusting a height of the fence and the distance from the model, an abrupt gust can be produced, which is very similar to the gust in a natural wind. The flow around the building and wind loads are influenced significantly by the characteristics of the approaching gust, so peak wind load do not correspond with the approaching gust speed.The response of a building induced by the gust are influenced by the gust shape and the duration of the gust. The rectangular gust induces a large over shoot response and the maximum displacement is about twice of the static displacement. When the duration of the gust is as same as the natural frequency of the building, the resonance effect are observed and the effect increases with number of successive gusts. When the gust passes away a building, the response shows a free vibration behavior. The amplitude of the free vibration is very much effected by a shape and a duration of the gust. When the gust duration equals the natural period of a building, the amplitude tends to null in a sinusoidal gust.