Abstract
The effective width theory is introduced from post-buckling strength of the uniformly compressed stiffened plates. In the ultimate strength of the plates for other load and other boundary condition, it seems that it has been given a broad interpretation of this effective width theory. The effective width is reexamined from the viewpoint of post-buckling strength. The main results are as follows.
(1) The effective width of unstiffened plates should be evaluated not by post-buckling strength by buckling strength.
(2) The effective width of stiffened plates under bending moment or shear load can be evaluated by post-buckling strength.
(3) The bending strength of the plates is calculated by the effective plastic section modulus evaluated with the effective width.
