An Integral Equation Solution for Limit Loads Applied to Lugs on Cylindrical Shells

A lower-bound limit analysis of loaded integral lugs on cylindrical shells is presented. Normal force and circumferential and longitudinal moment loadings on the lug are considered. The equilibrium solution, necessary for a lower bound, is obtained as a convolution integral of the concentrated load solutions of linear shallow shell theory. The load distribution is chosen to satisfy the yield condition everywhere, while maximizing the load. A simplified yield condition in terms of the shell stress resultants is used. Failure is assumed to occur in the shell, not the lug. Encouraging comparisons with available experimental results for moment-loaded rectangular lugs on pipes are presented. The use of shallow shell theory enables the problem geometry to be described by one less parameter than complete shell theory.