Finite Element Structural Analysis of Local Instability

A finite element analysis is presented for predicting local buckling stresses in plates, stiffened panels, and thin-walled columns for which the cross section is made up of thin flat plates. The analysis leads to the formulation of the elastic and geometrical stiffness matrices appearing in an eigenvalue equation used to determine the buckling stress. The stiffness matrices are derived from the exact sinusoidal lengthwise variation of displacements. The resulting sinusoidal stiffness matrices depend on the wavelength of the buckled pattern, but this dependence is of a very simple form, since all stiffness coefficients contain the buckling wavelength as a common factor. Examples are given to illustrate application of the method to several typical aircraft structural components.