Antisymmetric Post-Buckling Localization of an Infinite Column on a Nonlinear Foundation with Softening

Field observations reveal that very long members such as railway tracks and pipelines which are subjected to axial compression, induced usually by temperature and/or pressure increases, experience localized buckling. This paper presents a solution for the antisymmetric post-buckling of such members when restrained by a nonlinear foundation that includes softening effects. The principle of minimum total potential is invoked in order to develop the governing differential equations of buckling, as well as the non-linear equations of equilibrium in the post-buckled range of structural response. In order to solve these equations, a semi-analytical solution is proposed based on a perturbation technique, as well as a numerical technique based on a single shooting procedure for the solution of boundary value problems. The results of the analysis show that the post-buckling configuration of the column changes from a lengthwise periodic mode at the initial stages of loading to an isolated sinusoidal mode at the later stages of post-buckling, which represents a localization in the post-buckling range. This response is typical of that observed often in practice. Comparisons between the results of the perturbation technique and those of the numerical approach indicate that the semi-analytical perturbation solution predicts the initial post-buckling response of a column on a nonlinear foundation quite accurately.