Local Buckling of Steel Pipelines with Multiple Internal Corrosion Defects

A finite element analysis parametric study has been carried out to investigate the critical buckling response of line pipe subjected to combined loading with single and two corrosion defects of equal and unequal depth. Effects of material properties, D/t ratio, internal pressure ratio, axial load ratio, defect axial length ratio, defect hoop length ratio and defect depth ratio on the pipe local buckling response have been evaluated. The defect depth ratio and defect hoop length ratio appear to be the most influential parameters on the critical buckling limit ratios (corroded to plain pipe ratio). Non-dimensional equations for critical local moment, critical compressive strain and critical local curvature ratios have been developed from the parametric study results through multi-variable non-linear regression analyses. A good agreement has been achieved between the predicted results through the developed equations and FEA critical buckling limit ratios.