Cost minimization of a ring-stiffened conical shell loaded by external pressure

A ring-stiffened slightly conical shell is optimized for external pressure according to the design rules of Det Norske Veritas. The whole length and the different two end radii are given. The shell is divided into n equidistant segments with one stiffener in each segment. Each segment has a different shell thickness determined using a buckling constraint, and each ring-stiffener of welded square box section is designed by means of the required moment of inertia. The optimal number of shell segments (nopt) is determined by means of costs calculated for a series of n. The cost function includes the material, fabrication and painting costs. The shell normal stresses are determined also by finite element method.