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Hi All, I am designing a greenhouse that has steel as main supporting members and polythene sheet as cladding. Have a look at this image. My Client wants a minimal design. The governing loading is wind load. We all know that polythene sheet has significantly less strength as compared to steel and designing the steel frame assuming that the wind pressures are fully resisted by polythene cladding is not wise and would lead to a over design. I have following 2 questions: 1. Am I right that I should reduce the wind intensity/ wind forces on the steel members by a coefficient due to the presence of polythene sheet vs Steel, as it will burst/ puncture far earlier before resisting all the design wind pressures. 2. How to measure wind pressure sustaining capability of a polythene sheet. I knows its thickness (200 micron) and I know its tensile yield strength (20MPa). I know the spans across which its supported on the steel (300mm and 500mm). Is the method for calculating tensile stress similar to method used to determine tensile stress in steel sheet supported on all four sides (the coefficient method). or is there another method. Please guide. Thanks Usman