Reduced stress design of plates under biaxial compression

European standard EN 1993-1-5 provides the effective width method and the reduced stress method as calculation methods for plate buckling assessment. This article focuses on the reduced stress method, for which the global slenderness concept was introduced into EN 1993-1-5. The concept offers advantages associated with today’s numerical procedures which allow the elastic critical load factor of the full stress field to be determined in a single step, thus taking interaction into account in a very elaborate way. However, this article shows that the interaction verification in its pure format based on the von Mises yield criterion is not able to represent the actual mechanical behaviour of biaxially compressed plates. A simple modification is proposed which leads to appropriate and plausible results.