Proper selection of sheets and fasteners

As a result of attaching the folded sheet to the shelves of purlins or transoms, its thermal expansion from sunlight causes the occurrence of very high shear forces of fasteners. This shear is greatest in the area of the supports of purlins or transoms, where the bolts are sufficiently rigid, resistant to deformation and displacement in the plane of sheet metal. An additional influence on the size of the cutting forces in the fasteners exert:
a) skeleton displacement,
b) span deflections of sheets,
c) changes in the support angles of sheets.

For the above reasons, fasteners must be specially selected and made of a material with greater strength than sheet metal. Means, that as a result of mutual pressure of the sheet and fastener, it is the sheet that will undergo faster deformation. The maximum permissible sheet thicknesses for individual types are included in the table’ fasteners give a guarantee, unanimously, that during the formation of thermal stresses, the resulting shear of the fasteners will not lead to their destruction.

The fastest and easiest installation of a roof made of corrugated sheets is achieved by using continuous, uninterrupted sheets from the ridge to the eaves, based on large spacing purlins. However, their use may negatively affect the construction of the steel frame due to thermal elongations of the sheets caused by the radiation of the sun..

The above-mentioned construction recommendations, concerning the rules for the selection of impassable length of sheets, and mutual selection of the thickness of these sheets and the diameters of the fasteners protects the roof structure against damage caused by stresses and thermal deformations as a result of climatic interactions.