Semi-compact steel plates with unilateral restraint subjected to bending, compression and shear

The buckling of thin-walled steel plates which are juxtaposed with a rigid medium must be treated as a contact problem, since the local buckles may only form away from the rigid medium in a unilateral mode. One particular example is the bolting of plates to the sides of reinforced concrete beams in order to stiffen and strengthen the original concrete beam. Plates which experience first yield before local buckling are referred to as semi-compact, and this paper uses an energy method developed elsewhere by the authors to study the unilateral local buckling of restrained plates, so that limiting depth to thickness ratios may be obtained that delineate the semi-compact section classification when the plate is subjected to a combination of bending, compressive and shearing actions. The application to retrofitting concrete beams is discussed.