Investigation on the influence of strength mismatch on the local buckling behavior of large diameter pipelines

As a critical connecting structure in large diameter pipeline for long distance natural gas transmission, girth weld strength mismatch characteristics may significantly affect pipeline global structure stability, for pipelines subjected to combined internal pressure and bending loads. For this concern, a three-dimensional numerical model is developed to investigate the buckling behavior of girth-welded pipelines under combined loading, considering the girth weld strength mismatch and misalignment. Results reveal that higher internal pressure significantly suppresses buckling instability by enhancing the cross-section stiffness of pipelines. The diameter-wall thickness ratio ( D / t ) also influence the buckling behavior, and pipeline with large D / t yields lower bending bearing capacity. Strength mismatch significantly affects the buckling behavior under lower internal pressures and larger D / t . Compared with even-match, over-match and under-match reduce the limit bending curvature. The effect of strength mismatch is significantly weakened when misalignment exists. • Buckling behavior of girth-welded pipelines under combined loading is studied. • Pipelines with large D / t suppress bending bearing capacity. • Strength mismatch markedly affects buckling at lower pressure and larger D / t . • Misalignment considerably weakens the influence of strength mismatch on buckling.