Sandwich construction is increasingly used as wall and roof cladding for building structures. Typically, a cladding panel may consist of two plane or profiled metal faces with a foamed plastic core. The core may be polyurethane, polyisocyanurate, polystyrene or phenolic resin. When such a panel is subject to static loading due, for instance, to wind, snow 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, though 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 takes place when one buckle in the region of maximum bending moment cripples. In light gauge steel applications, the conventional design treatment for this phenomenon utilises the concept of effective width. In order to investigate the extension of the effective width concept to plate elements supported by plastic foam material, a series of tests were undertaken on foam-filled steel beams. This paper describes these tests and their interpretation in terms of an enhanced effective width formula.
