Theoretical Analysis of the Collapse Performance of Thick-Walled Pipes With Corrosion Defect Under External Pressure and Bending

Abstract Subsea pipelines operating in harsh marine environments are subjected to complex loading conditions, with the combined effects of external hydrostatic pressure and bending being common in deep-water pipeline service. Such loading interactions can induce severe ovalization, leading to local buckling and potential buckling propagation, particularly in the presence of corrosion. This paper investigates the collapse behavior of corroded steel pipes under the combined actions of external pressure and bending through both theoretical analysis and numerical simulations. An analytical model was established to predict the collapse moment and failure mode of steel pipes with corrosion defects under the combined external pressure and bending. The reliability of this model is validated through a numerical framework. A parametric study is then conducted to evaluate the influence of key factors, including geometric properties, material characteristics, and defect sizes, on the collapse performance. The results show that the bending affects the growth of ovalization, and the influencing extent depends on the magnitude of the initial external pressure. Furthermore, the collapse moment exhibits a characteristic of a “slight decrease followed by a sharp drop” as the initial external pressure increases.