Comparison of plastic limit and collapse loads in pipe bends with shape imperfections under in-plane bending and an internal pressure

The comparison of limit load based on small displacement limit analysis and collapse load based on large displacement analysis for shape-imperfect pipe bends, under combined in-plane closing bending and an internal pressure, were carried out using finite element method. The limit and collapse moments were obtained from moment–rotation curves drawn for each model. Twice-elastic-slope method was used to obtain collapse load. The effect of thinning on limit and collapse moments are minimal and hence thinning need not be considered for the analysis of pipe bends. The influence of ovality on both limit and collapse loads for most of the cases considered are significant. Comparison of effect of ovality on limit and collapse loads reveals that the determination of collapse load is preferable when ovality is included in the analysis of pipe bend. A closed-form solution is presented to include ovality in the determination of the collapse load of pipe bends.

► Comparison of limit and collapse loads for shape-imperfect pipe bends is performed.
► Shape imperfections considered are ovality and thinning.
► Finite element limit analyses use small and large geometry change effects.
► Twice-elastic-slope method was used to obtain plastic loads.
► Determination of collapse load is preferable when ovality is included in the analysis.