Experiments and design of edge-stiffened plates under stress gradient

The behaviour of thin steel plates fall into three general classes, unstiffened (no edge-stiffener), stiffened (adequate sized edge-stiffener) and partially stiffened (inadequate sized edge-stiffener). When used in cold-formed steel sections they may elastically buckle when subjected to either uniform compression or stress gradient. There are thus six possible combinations of element class and loading condition. All except the class of partially stiffened elements under stress gradient has been investigated experimentally, and design equations developed. This paper presents experiments of edge-stiffened plates under stress gradient, where the edge-stiffener size was increased from zero to a size sufficient to create a stiffened element. Edge-stiffener types investigated are simple lips and complex lips. Design solutions for partially stiffened elements under stress gradient using the effective width concept are presented. A generalised effective width design model is developed to account for all classes of elements under any loading condition.