Parametric solution of lateral buckling of submarine pipelines

Abstract

Lateral buckling analysis of on-bottom submarine pipelines is of particular interest in the offshore industry due to the complexities involved in the analysis, and the potential design efficiencies that can be unlocked. Classical buckling theories by previous researchers and recent joint industry projects provide a basis for estimation of the critical buckling load of a straight, or in some cases imperfect, pipe on either a rigid or elastic seabed. However, systematic solutions for the combined effects of nonlinear soil properties and the as-laid geometry – specifically the out-of-straightness – on the buckle initiation behaviour have not been developed previously. This paper reports an investigation of the buckling problem of an imperfect (non-straight) on-bottom pipeline subjected to axial compressive loading. The seabed was modelled with lateral and axial nonlinear, springs to idealise the load-displacement behaviour of the soil and the pipe was modelled with pipe elements. Buckling was performed by a displacement controlled finite element method with the modified Riks algorithm that is available in the commercial software ABAQUS. This numerical tool was used to develop a parametric solution for the present problem in terms of the various pipe material and geometry parameters and the lateral and axial pipe-soil interaction parameters. In particular, the influence of the magnitude and stiffness of the lateral pipe-soil response was investigated, highlighting the sensitivity of the pipeline response to the geotechnical inputs. The results have been synthesised in a generic non-dimensionalised design chart to estimate the buckling load, valid for the range of inputs covered by the parametric study.