Optimum design of circular tubes loaded in compression in preand post-buckling ranges

Abstract

Based on Kuhn-Tucker optimality criteria, using a grapho-analytical method, simple closed formulae are given for optimal diameter and thickness of centrally compressed struts of circular hollow section. These dimensions minimize the crosssectional area and fulfill the design constraints. In the prebuckling range overall and local elastic buckling constraints are defined. In the post-buckling range the optimal sizes can be calculated using the formulae valid for the prebuckling range, but instead of the limiting D/t-ratio, valid for semi-compact tubes, the plastic limiting D/t-ratio should be used to avoid local buckling. The comparative calculations show the mass savings achievable by using a higher-strength steel as well as the larger axial shortening of struts made of higher-strength steel.