Analytical and Numerical Study of Collapse of Pipelines With Interacting Corrosion Areas Under External Pressure

Abstract Corrosion poses a severe threat to the integrity of offshore pipeline systems and the external pressure may cause collapse-type failure. The effects of interactions involving multiple corroded regions have been rarely studied analytically. This paper presents a combined analytical and numerical study of the collapse of subsea pipelines under external pressure with two interacting corroded regions. Corrosion asymmetry is introduced as the misalignment of middle axes to account for the co-existing internal and external corrosions. Governing differential equations for elastic collapse are formulated. A finite element analysis (FEA) is performed by automatically generating a series of models using a Python script in Abaqus, and the FEA collapse path agrees well with the analytical results. An extensive parametric analysis is done by perturbative analysis technique to formulate a criterion for determining the collapse modes. FEA study has been conducted by automatically generating a series of models by python script in Abaqus and FEA collapse path agrees well with the analytical result. Parametric analyses are conducted for parameters such as distance between corroded regions, misalignment, corrosion extent angle. The active yielding zone analysis clearly reveals the evolution of plastic hinges for elastic-perfectly plastic materials. The formulated collapse mode criterion accurately predicts the collapse mode and is suitably applicable even when material exhibits plastic behavior. For cases where the corrosion region has nonuniform thickness, an analytical Lyapunov artificial small parameter method is introduced. Additionally an optimal truncation number estimation method based on Hölder’s inequality predicts well the necessary truncation number for power series convergence. This paper should enhance the understanding of the impact of corrosion on pipeline’s integrity under external pressure in offshore industry.