Prop-imperfection subsea pipeline buckling

Abstract

In-service buckling of subsea pipelines can occur due to the introduction of axial compressive forces caused by the constrained expansions set up by thermal and internal pressure actions. Proposed herein is a mathematical model relating to a pipeline, the otherwise horizontal and straight idealised lie of which is interrupted by an encounter with an isolated prop or point irregularity. The overbend produced can serve, in the presence of enhanced topologies involving trenching, burial, discrete or continuous, and fixed anchor points, to trigger vertical or upheaval buckling of the pipeline under in-service conditions. The results of a series of case studies are contrasted with data appertaining to alternative models available in the literature: experimental support is additionally noted. By questioning the implicit stress-free-when-straight assumption present in these alternative models, it is considered that a consistent, imperfection-prone isolated prop formulation is hereby provided, suitable for design application.