Local buckling responses of large-diameter pipelines with girth weld misalignment

• Buckling behavior of girth-welded pipelines under combined loading is studied. • Buckling mode shifts from inward diamond to outward bulging as pressure increases. • Strain hardening affects the limit curvature more than the limit moment. • Misalignment significantly reduces both the limit moment and critical curvature. As a key connection component of large-diameter transmission pipelines, the geometric configuration of girth welds can markedly influence the overall stability. However, frequently encountered misalignment can reduce the buckling capacity of pipelines. A finite element model is established to examine the pipelines buckling response under combined loading, incorporating the misalignment, strain hardening behavior and boundary nonlinearities. The results reveal a nonlinear influence of internal pressure on the limit moment. As the internal pressure increases, the local buckling mode near the girth weld changes from inward diamond mode to outward bulging. D / t exerts a negligible influence on the limit curvature, whereas it significantly impacts both the limit moment and the critical curvature. When the strain hardening exponent increasing from 8 to 18, the limit moment and curvature decrease by 20.8% and 48.4%, respectively. Misalignment significantly reduces bending capacity of the pipeline. For unpressurized pipelines, large misalignment significantly reduces the limit bending moment and curvature, whereas full pressurization renders these parameters nearly unaffected. The effect of misalignment on buckling behavior becomes increasingly evident as the internal pressure decreases.