Explicit analysis and design equations for buckling loads and minimum stiffener requirements of orthotropic and isotropic plates under compressive load braced by longitudinal stiffeners

In the framework of lightweight engineering, especially in the conceptual phase of a structural analysis, closed-form analysis methods are of high practical importance since these usually work with negligible computational effort when compared to purely numerical approaches. In this paper, simple closed-form analytical formulas for the buckling loads N110 of compressively loaded orthotropic composite and isotropic plates braced by longitudinal stiffeners are derived. Furthermore, closed-form expressions for the minimum bending stiffness EIminEImin of the stiffeners are presented. The derived methods lead to a very satisfying accuracy when compared to the exact transcendental elasticity solution, to accompanying purely numerical analyses and to reference results from the literature, which makes the introduced analysis equations very suitable for the preliminary analysis and design of stiffened isotropic and orthotropic composite plates. Furthermore, due to their very simple nature, the introduced closed-form approaches can be recommended for direct use in an industrial environment for any practical engineering purpose.