Elastic postbuckling stiffness of biaxially compressed rectangular plates

The elastic buckling and postbuckling response of biaxially compressed plates is analysed with main focus on change of in-plane postbuckling stiffness under prescribed plate shortenings rather than the more normal load control. An analytical closed-form single-degree-of-freedom solution is derived and compared with an analytical multi-degree-of-freedom model. Results for the analytical multi-degree-of-freedom-model are obtained by solving numerically the equilibrium equations using the perturbation expansion technique with arc length control in an incremental scheme. Both models are applied to specific plate examples and comparisons with results obtained using a commercial nonlinear finite element program are included.