Burst capacity analysis of thin-walled pipe elbows under combined internal pressure and bending moment

Highlights: • Employ FEA to investigate the bending effect on burst capacity of pipe elbows. • Consider three bending modes: in-plane closing and opening, and out-of-plane. • Consider wide ranges of elbow dimensions and steel grade for defect-free elbows. • Consider various sizes and locations of local-wall thinning (LWT) defects on elbows. Structural integrity analysis of pipe elbows is of critical significance because they not only withstand the internal or external pressure but also absorb the bending moment in a pipeline system. While the burst capacity of pipe elbows under internal pressure only have been extensively investigated in the literature, the study on the burst capacity of pipe elbows under combined internal pressure and bending moment is still limited. In this paper, the effect of bending on the burst capacity of thin-walled defect-free and local wall-thinning (LWT) elbows subjected to combined internal pressure and bending moment is systematically investigated. A correction factor is defined to quantify the bending effect on the burst capacity; extensive parametric finite element analysis (FEA) is carried out to analyze the dependence of the correction factor on the bending mode and magnitude, elbow size and steel grade, and LWT size and location. The results indicate that as the magnitude of the bending increases, the burst capacity of both the defect-free and LWT elbows generally deceases. For the defect-free elbows, the elbow steel grade has a significant influence on the correction factor while the influence of the elbow geometry is marginal. For the LWT elbows, the correction factor depends markedly on the LWT location and bending mode.