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.

在不平坦的海底安装未挖沟的海洋管道通常会导致沿管道形成许多自由跨度地层。此外，海上管道可能会受到高纵向力的影响，这会改变管道在不同负载状态下的行为。在本文中，评估了轴向力对自由跨位置的管道变形和相关危害的影响。评估可能导致整体屈曲的过度压缩力。使用本研究中介绍的分析方法研究了响应轴向力变化的凹陷上的管道行为。MATLAB 软件用于基于案例研究数据的数值求解。允许加载状态以避免管道在压缩载荷下屈曲以及基于 Von-Mises 屈服准则的管道截面上的最大允许应力是对承受组合加载条件的管道考虑的两个限制。本文揭示的结果指定了几种纵向载荷情况下的自由跨度允许长度，以避免屈曲失效和管道截面上的过度应力。