Effect of ovality and variable wall thickness on collapse loads in pipe bends subjected to in-plane bending closing moment

The effect of ovality and variable wall thickness (thickening at intrados and thinning at extrados) on the collapse loads in pipe bends subjected to in-plane bending moment that tend to close the bend was investigated using finite element limit analyses based on elastic-perfectly plastic material with large geometry change option. The collapse moments were obtained from load–deflection curves of the models with circular (uniform wall thickness) and irregular cross sections and compared. The presence of ovality in the pipe bends significantly affects the collapse loads while thinning produce very less effect. Based on finite element collapse load (twice-elastic-slope) results, a mathematical equation is proposed to include the effect of ovality.

► Ovality produces significant effect on collapse moments of pipe bends.
► The effect of ovality must be considered for the design of pipe bends.
► A mathematical equation is proposed to determine collapse moment for pipe bends.
► Thinning produces negligible effect on collapse load.
► It is found that the collapse moments increase with thickness and bend radius.