Local buckling behaviour and design of sandwich panels in buildings

Abstract

Sandwich construction is increasingly used as wall and roof claddings for building structures. Typically, a cladding panel may consist of two plane or profiled metal faces with a plastic foam core. The core may be polystyrene or polyurethane. When such a panel subject to static loading due, for instance, to wind uplift or temperature gradient, one face is compressed and becomes liable to local buckling. If this face has a trapezoidal or similar profile the failure mode is similar to that for profiled steel sheeting, but the failure stress is enhanced by the presence of the core. The compressed face element first forms a series of buckling waves which increase in amplitude in the postbuckling phase. Failure take place when one buckle in the region of maximum bending moment cripples. This thesis extends the European design recommendations to validate their research for Australian sandwich panels made of high strength steel and polystyrene foam core. European design recommendations for foam filled steel members are based on polyurethane foam core and low tensile steel. In order to verify the European design recommendations for high tensile steel and polystyrene foam core, experimental tests and finite element analysis were conducted. Steel plate elements with and without foam core were used in the investigation, with varying width to thickness (b/t) ratio (105 to 513) and grade (G250 and G550) of steel. Buckling stress and buckling shape as well as ultimate stress and the associated stress versus out-of-plane deflection curves were produced. Finite element analyses and experiments illustrated the inherent benefits of composite foam filled steel members. The improvement of the buckling coefficient, K, for thin-walled steel plate elements was demonstrated. Each width to thickness (bit) ratio had a specific K value that increased with increasing width to thickness (b/t) ratio. Results obtained from this investigation showed that the European buckling and ultimate strength design equations can be satisfactorily used for the Australian sandwich panels