Experimental testing of stressed skin effect of sandwich panel roof diaphragms – Test result evaluation considering diaphragm rigidity

The current research paper presents the experimental investigation on stressed skin effect of sandwich panel roof claddings, which is part of an ongoing research program carried out at the Technical University of Cluj-Napoca. The objective of the study was to quantify the influence on the diaphragm rigidity of certain cladding configurational parameters. This was achieved by a series of 14 two-side fastened sandwich panel roof diaphragm experimental tests, involving sandwich panels connected to Z shaped purlins. The tested cladding configurations allowed to quantify the influence on diaphragm rigidity and shear capacity of nine individual parameters. An automated experimental diaphragm rigidity evaluation method is also presented, which was used to ensure an objective comparison of the experimental data. The results of the study highlight that the diaphragm rigidity can be increased by increasing the sandwich panel rib number, the number of panel-to-purlin fasteners or the number of seam fasteners (up to a certain point), as well as by switching from continuous purlins to overlapped purlins or changing the purlin cleat orientation. Experimental diaphragm rigidities are compared to analytical predictions and commented.