Abstract
An atmospheric boundary layer wind tunnel study was performed to determine the overall horizontal wind load on multi-span duo-pitch greenhouses. The results of this study are intended for the stability design of inflexible Gladding system greenhouses (designated as Class A in EN 13031-1) with roof pitch angles of 23-24' and ridge heights of 7.5-8 m. Both static force and fluctuating pressure measurements were performed to determine the overall horizontal wind force. The results obtained with the static force measurements show that the overall horizontal wind force increases linearly with increasing number of spans. The overall horizontal wind load determined with the mean pressure coefficients derived from the fluctuating pressure measurements was found to be in good agreement with the static force measurements. An investigation into the correlation of the roof pressures showed that these pressures are relatively little correlated. The overall horizontal force on the roof of multi-span buildings reduces significantly because of this lack of correlation. Accounting for the lack of correlation between the roof pressures on a 30span model resulted in a 65% reduction of the peak horizontal wind force on the roof. A comparison was made of the overall horizontal wind forces determined in the current study and calculated with European codes for wind load assessment on greenhouses. EN 13031-1 provides non-conservative outcomes for the overall horizontal wind force on the investigated duo-pitch greenhouse type with more than 30 spans. On the other hand, EN 1991-1-4 is increasingly conservative with larger number of spans.
Highlights
Greenhouses in Europe have grown in size over the last decades
This study investigates the overall wind load on a typical multi-span duo-pitch greenhouse
The pressure measurements performed in this study show that the mean pressure coefficient on the windfacing roof faces are near 0
Summary
Greenhouses in Europe have grown in size over the last decades. For example, in the Netherlands between 2000 and 2014, the surface area of greenhouses per company has more than doubled, with an increase from 0.95 to 2.15 ha (LEI Wageningen UR, 2015). Wells and Hoxey (1980) suggest that, some roof pressures can be slightly more severe for wind directions other than perpendicular to one of the walls, the oblique wind directions are unlikely to justify consideration in design. This suggestion simplifies codification of results, as it limits relevant results to the main axes of the greenhouse. Force coefficient notation applied for experimental results cfr Surface friction coefficient cfr,eq
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