Analysis of Buckle Initiation in Damaged Subsea Pipelines

A rigid, perfectly plastic mechanism analysis, embodying interactive uniaxial membrane and bending plasticity, is used to predict the form of localized impact damage for tubulars. An extension of the model allows the pressure response of a pipe containing damage, and in particular the pressure at which buckling is initiated in a damaged pipeline. Test results are shown to confirm the validity of the mechanistic approach employed in predicting the damage process, while initiation tests based on a different initial imperfection configuration are shown to reproduce the trend of predicted initiation pressures. An attempt to improve the buckle performance through the use of spirally rib-reinforced pipelines is also described. Although propagation pressure buckle resistance is considerably enhanced, use of rib-reinforced pipelines is shown to have a less dramatic beneficial influence upon buckle initiation pressures.