Experimental Investigation of Torsional Restraint Provided to Thin-walled Purlins by Sandwich Panels under Uplift Load

AbstractSandwich panels, usually used as members of wall or roof cladding, can provide lateral and torsional restraint to metal members of the substructure along their spans. They can positively influence the buckling resistance of the metal members. Lateral restraint given by sandwich panels can be considered for downward as well as uplift load applied on the surface of the panels. Torsional restraint can normally be utilized in case of downward load only. The uplift load causes the reduction of the contact area between the panels and metal members which is assumed to result in small (or conservatively zero) values of rotational stiffness which corresponds to the torsional restraint. There is a lack of data regarding torsional restraint under uplift load. Certain values of torsional stiffness can be considered when metal members of cold-formed cross-sections are utilized.The paper focuses on experimental verification of torsional restraint given to steel purlins of thin-walled cold-formed cross-sections by sandwich panels under uplift load. As the test setup for verification of the torsional restraint provided to metal members by planar members according to the actual standard for design of steel structures does not cover the influence of external load applied on the surface of the panels, a special test setup taking the external load into account had to be used. The paper describes the specimens, the test setup and the procedure of testing and summarizes selected relevant results of the series of performed tests