A simple rolled steel section used as an isolated structural element, as a support of other structural elements, or as part of other structural elements. When isolated plates are extremely thick, their design is controlled by shear; plates of moderate thickness are controlled by bending (with some torsion), and very thin plates carry their loads principally by tensile membrane action. Although stresses of all types exist in all plates, it is usually sufficient to deal with only the most significant. Bending is the most common design criterion.
Plates are commonly used as cover plates on wide-flange beams, as the flanges and webs of plate girders, and as the sides of tube-shaped beams and columns. In all these cases, serious consideration must be given to the fact that the plate may buckle when compressed. Fortunately, the plates have edge supports in the direction of the stress, so they function as panels rather than as beams. Their ratios of length to width are large enough that the resistance to local buckling of the plate element depends upon its width-thickness ratio, practically independent of its length. (The length of the overall section is still significant in determining the member's capacity.) See Beam, Column, Joint (structures), Loads, transverse, Structural steel