Load and Resistance Modelling of the Penguins Pipe-in-Pipe Flowline Under Lateral Buckling

The Penguins pipeline is a 60 km PIP system design to buckle laterally on the seabed. For a PIP system, a key failure mode is wrinkling of the outer pipe at the field joint due to excessive bending. For the Penguins PIP it was decided to use a moment-based approach to this failure mode, but to reduce the uncertainties on the load and capacity so that higher design factors could be justified. A structural reliability assessment (SRA) was employed in order to confirm suitable safety factors. This paper describes the development of the capacity and response functions required to undertake the SRA for the pipeline. The response function defines the maximum bending moment as a function of key uncertain parameters. The required relationships were based on an extensive series of lateral buckling analyses of the PIP system. The resulting response function can also be used to assess to what extent the loading is moment-controlled or curvature-controlled. To define the capacity function full-scale testing of the PIP field joint configuration was undertaken and was supported by extensive FEA modelling.