Study of wind loads on pipe-framed greenhouses: External wind pressure coefficients on enclosed structures
2008
Uematsu, Y.(Tohoku Univ., Sendai (Japan)) | Nakahara, K. | Moriyama, H. | Sase, S.
Wind loads for designing the structural frames of pipe-framed greenhouses have been studied based on a series of wind-tunnel experiments with two kinds of pipe-framed greenhouse models. The present paper focuses on enclosed greenhouses with no openings. Wind pressure distributions on two or three typical cross-sections were measured in a turbulent boundary layer simulating natural winds over typical open-country exposure for various wind directions. The measurements were made in two different wind tunnels, which are quite different in size from each other. The LRC (Load Response Correlation) method is employed for estimating the design wind pressures, expressed as equivalent static pressures, with consideration for the time-space correlations of wind pressures. The bending moment at the windward column base is taken into account as the most important load effect. The results of the LRC method are compared with those of a time-history analysis as well as with those predicted from a conventional gust effect factor approach from the viewpoint of load effect. It is found that the largest load effect is induced in a frame near the windward gable wall in an oblique wind not in a central frame in a normal wind. The wind force coefficients for gable and circular arc roofs, which are specified in the current standards, are not necessarily appropriate for pipe-framed greenhouses often used in Japan. The effects of turbulence intensity and scale on the wind pressure distributions are also investigated.
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