Evaluation on collapse behaviour of thick-walled pipes with corrosion defect under combined external pressure, axial tension and bending moment

In the deep-water environment, the steel pipe is prone to collapse under the combined effect of corrosion defects and complex loadings. In this present study, the ultimate bearing capacity of corroded pipes under external pressure, axial tension, and bending was studied through theoretical and numerical efforts. An extended theoretical model was proposed to examine the bending capacity for pipes with rectangular defects under combined loadings. Meanwhile, finite element models were also developed to simulate the collapse event, which was then verified by theoretical predictions and existing experimental results. Subsequently, sensitivity studies on the bending capacity of corroded pipes under combined external pressure and axial tension were carried out, and the results indicated that in addition to the significant influence of defect sizes and initial loadings, the effect of the pipe's geometric parameters and material properties cannot simply be ignored. Afterward, based on the comprehensive numerical predictions, a multi-layer perceptron (MLP) model was developed to evaluate the ultimate bending capacity of corroded pipes under combined loadings.