Study on symmetric buckling mode triggered by dual distributed buoyancy sections for subsea pipelines

Abstract

In order to control lateral buckling, buckle initiation techniques, such as distributed buoyancy section (DBS) are employed to trigger lateral buckles at planned locations. Dual DBSs with a gap between are sometimes employed as a buckled initiation method, which may trigger either a symmetric or antisymmetric mode. In this study, analytical models for symmetric mode triggered by dual DBSs are proposed, which are validated by comparing with test data. First, the buckled configuration and the post-buckling behaviour are analysed. Then, a detailed analysis is carried out to present the effect of dual DBSs on the characteristics of the buckling behaviour. Comparisons between symmetric and antisymmetric buckling mode triggered by the same dual DBSs are discussed. The results show that when dual DBSs are utilised as the buckle initiation technique, both the symmetric and antisymmetric mode can be triggered. Symmetric mode is prone to be triggered for relative small spacing between dual DBSs. The symmetric mode is more dangerous than antisymmetric mode except that the weight ratio coefficient is small enough. Therefore, during the design process, it's better to check the maximum stress of both symmetric and antisymmetric mode to ensure the integrity of the buckled pipeline.