Residual bending capacity for pipelines with corrosion defects

Residual bending capacity for corroded pipelines in the presence of axial force and internal pressure can be determined analytically assuming a full plastic failure mode for the pipeline. In this paper, a set of closed-form analytical solutions for residual bending capacity are developed for pipelines with idealized corrosion geometries, namely, constant-depth, elliptical, and parabolic corrosions. It is shown that pipelines with idealized elliptical or parabolic corrosion yield higher bending resistance than that of constant-depth, with the difference between elliptical or parabolic corrosion particularly significant for the case of deep and wide corrosion. It is further pointed out that the simplification of the actual corrosion geometry by constant-depth, as commonly assumed in current code assessment of corroded pipelines, will inevitably underestimate the residual strength of the pipe, especially for the case of deep and wide corrosion. Finally, the experimentally measured bending moment is adopted to validate the proposed analytical solutions in this paper.