Effect of internal pressure and shape imperfections on plastic loads of pipe bends under in-plane closing moment

The influence of internal pressure and shape imperfections of pipe bends on collapse load was investigated under in-plane closing bending moment using finite element limit analysis based on elastic-perfectly plastic material considering geometric nonlinearity. Twice-elastic-slope method was used to obtain the collapse load. For each model, at a certain internal pressure, the collapse moment was found to be the same for the pipe bends with oval and circular cross sections, at any other pressure the effect of ovality is significant. The thinning produces negligible effect on collapse load. Closed-form solutions are proposed to determine the collapse moment of pipe bend.