Analytical study of subsea pipeline behaviour subjected to axial load in free-span location

摘要

Installation of un-trenched marine pipelines on an uneven seafloor usually leads to many free-span formations along the pipeline. Also, offshore pipelines may be subjected to high longitudinal forces that can change pipeline behaviour in diverse loading states. In this paper, the effect of axial force on pipeline deformation at the free-span location and associated hazards are assessed. The excessive compressive force which can result in global buckling is evaluated. Pipeline behaviour over a depression in response to axial force variations is investigated using an analytical method presented in this research. MATLAB software is utilised for the numerical solution based on the case study data. Allowable loading state so as to avoid buckling of the pipe under a compressive load together with maximum allowable stress on pipe section based on the Von-Mises yield criterion are the two limitations considered for the pipe subjected to combined loading conditions. The results revealed in this paper specify free-span allowable lengths for several longitudinal load situations to avoid buckling failure and over stress on the pipe's section.