Practical estimation method for extreme value distribution of von Mises stress in ship structure

Abstract

This study presents a practical method for estimating the extreme value distribution of von Mises stress for ship structural strength evaluations. The previous methods of calculating this distribution require somewhat complicated numerical calculations, such as multi-dimensional integration. In contrast, the proposed method is based on an asymptotic approximation and can be easily calculated in a similar way to the conventional linear statistical prediction. A closed expression was derived in the case of stress components which have non-zero mean value. The formula is derived under approximations that reflect realistic stress conditions when ships are under severe sea states. Through a structural analysis of a whole ship, it was comprehensively verified that the proposed method has sufficiently high accuracy for structural strength evaluation. Furthermore, a parametric analysis was conducted to clarify its limit of applicability.