Determination of collapse loads in pipe bends with ovality and variable wall thickness under internal pressure and in-plane opening moment

• Shape imperfect pipe bends subject to in-plane bending and internal pressure is studied.
• Ovality produces significant effect on collapse moments of pipe bends while thinning has negligible effect.
• Based on the FE results, a mathematical expression is proposed to determine collapse load of the pipe bends with ovality.

The combined effect of ovality and variable wall thickness on collapse load of pipe bends under in-plane opening bending moment with internal pressure was investigated using finite element limit analysis considering large geometric change effect. The material was assumed to be elastic–perfectly plastic. The collapse moments were obtained from moment-rotation curves drawn for each bend using twice-elastic-slope method. Thickening/thinning effect on collapse load is very minimal and can be neglected. The effect of ovality is significant with the reduction of collapse load by a maximum of 39.1% for the maximum internal pressure and ovality considered. Based on the finite element results, a mathematical expression is proposed to determine collapse load of the pipe bends with ovality and this equation has been verified with experimental collapse loads.