How Changes in Distance Between Rafter or SheetSupport Influence Sheet Resistance to Bending
If we increase the width of the sheet (which is connected to the constructionon all four sides), the result will be that the load required to reach the samedeflection will decrease incrementally as the sheet width increases.After a certain, critical width, the load will not need to change at all in orderto reach the original deflection level, and the rafters along the length of thesheets will not contribute to the sheet's support
How Changes in Distance Between Purlins Influence Sheet Resistance to Bending
If, for example, we take a square sheet (equal in length and width), which issupported at all four sides by a steel frame, and apply a load of a certain type, this will cause the sheet to deflect. Now, let's keep those same connection parameters and increase the length of the sheet, then apply load to get thesame deflection as before. We'll find that, up to a specific, asymptotic sheetlength, the load required to reach the same deflection will gradually decrease.
Once this asymptotic sheet length is exceeded, no changes in the load level will be required to reach the original deflection level. Thus, we can conclude that,when exceeding a certain sheet length, the purlins that support the sheets alongtheir width do not contribute to the sheet's resistance to bending, and as such,are unnecessary. Under these circumstances, we can say that the sheets performas if they were connected to the construction in a Side/Side Configuration.
Installation of Polygal Sheets Onto a Structure
In architectural applications, Polygal sheets are normally installed withinaluminum or Polycarbonate profiles, which are supported along their lengthand width by the Rafters and Purlins of the construction. In greenhouseapplications, the sheets are connected directly to the greenhouse constructionusing screws.
Polygal sheets are asymmetrical in their geometry of length and width, and as such, their performance under loads differs according to changesin these dimensions .
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