Development of a Pipeline Wrinkle Material Ultimate Limit State: Full Scale Modeling

While the formation of a wrinkle in an onshore pipeline is an undesirable event, in many instances this event does not have immediate pipeline integrity implications. The magnitude or severity of a wrinkle formed due to displacement controlled loading processes (e.g. slope movement, fault displacement, frost heave and thaw settlement) may increase with time, eventually causing serviceability concerns (e.g. fluid flow or inspection restrictions). Pipe wall cracking and eventually a loss of containment involves contributions from the wrinkle formation process, as well as wrinkle deformations caused by in-service line pressure, temperature and seasonal soil displacements. The objective of this paper is to provide an overview of the ongoing research efforts, sponsored by TransCanada PipeLines Ltd, towards the development of a mechanics based wrinkle ultimate limit state that may be used in future to evaluate the long term integrity of wrinkled pipeline segments. The research efforts include testing and non-linear finite element modeling of a full scale wrinkled pipeline segment. This paper outlines the development of the full scale finite element model, including the detailed material model development, used to estimate the fatigue life of the experimental full scale fatigue test specimen. A comparison is then carried out between the experimental results and the results from the finite element analysis.