On the Plastic Buckling of Stiffened Panels under Axial Compression

Abstract

The general instability of a stiffened flat plate under axial compression is a problem of primary buckling of a bending type of deformation of the stiffener about an axis parallel to the plane of the sheet and a twisting type of deformation in which the stiffener rotates about an axis in the plane of the sheet. The paper treats the primary buckling of stiffened plates in the strain-hardening range as well as in the elastic range. The secondary or local buckling of the stiffener or plate such as crippling of the stiffener or interfastener buckling of plate are excluded.From consideration of the yielding process of structural steel it has been shown that the material becomes anisotropic when strained into the strain-hardening range. Introducing appropriate moduli the problem may then be treated as buckling of an orthotropic plate.Buckling in the elastic range, then, is a particular case of the orthotropic solution with the elastic moduli of steel. The application of the integral equation to the buckling of a stiffened plate simplifies the problem and saves labor and time for computation. The single basic integral equation covers the whole domain of the plate. The stiffener reactions enter as transverse or twisting loads but do not introduce new boundary conditions.The required minimum bending rigidity of a stiffener is obtained in both elastic and strainhardening range. The effect of torsional resistance of a stiffener on buckling strength is investigated for the stifener with a symmetric type of thin-walled open cross-section.