Net Cladding Pressures on Industrial Building Roofs

Abstract

The net wind pressure on roof cladding of metal clad buildings are critical for structural design. Large openings on the windward wall generate large positive internal pressure, which in combination with high external suction pressure produces large net negative pressure on the roof. Wind tunnel studies conducted on a 1:200 scale industrial building model and analytical methods were used to analyze combination effects of internal and external pressures on roof cladding. AS/NZS 1170.2 gives conservative net pressures on the windward roof edge of buildings, for quartering approach wind. The combination factor \(\left( {f_{C} = C_{{\check{p},net}} /\left( {C_{{\check{p}e}} - C_{{\hat{p}i}} } \right)} \right)\) varies depending on location of the cladding element and position and type of opening(s) in the envelope. The calculated \(f_{C}\) factors are 5% less than the combination factor in the AS/NZS 1170.2 for roof cladding of nominally sealed buildings while it is 5–10% less than the building with the large opening. Helmholtz resonance occurs in the building with large opening and internal pressure influences energy contained in the net pressure at the Helmholtz frequency. External suction pressures on windward roof edge and positive internal pressures in the building with large windward wall opening are negatively correlated whilst of external and internal pressures are positively correlated, in the nominally sealed building.