Instantaneous wind pressures on the wall of structures by the sudden change of wind direction

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A lot of dispersions and dropouts of claddings of the pane and the roof cladding subject, etc. have been generated though it is not possible to destroy with the large structure. In many cases, the wind loading for the design of these claddings is evaluated based on the experiment and the analytical result when the wind direction is constant. However, the wind force when the change in a rapid wind direction is accompanied is not necessarily included by the experimental result when the wind direction is constant. This research aimed to examine the spatial structure in the strong wind with a wind direction change, and to clarify properties of the local wind pressure on the large models.The wind direction variation character of natural wind was examined, and it proposed the idea of "Wind direction change section". By using this idea, "Rapid wind direction change" was shown as the phenomenon that the wind run in the "Wind direction change section" was small. Moreover, the wind pressure characteristics of the building exterior material by a momentary wind direction change were examined by the field measurement. As a result, when the instantaneousness of the wind direction change was high, it was confirmed might cause a big negative pressure. In addition, it proposed the method of evaluating the stability index of the wind direction in natural wind by the linearity of natural wind. It was shown to be able to select data with high generality by using this technique according to the wind direction stability. From the field measurement data concerning the surface wind pressure of the cylinder structure with high wind direction stability, it was shown that there was a possibility that the turbulence of the approach wind causes making of the decrease in the critical Reynolds number.