Development and Validation of a Pipeline Buckle and Wrinkle Assessment Model

Inspection has revealed pipeline buckles and wrinkles promoted by thermal loads, differential settlement, slope movement and other pipe-soil interaction modes, as well as, cold field bends during construction. While all agree that pipeline wrinkles are undesirable, the urgency of their repair is not commonly understood. In general, it is accepted that the onset of wrinkling does not result in a loss of integrity because pipeline steels are adequately ductile to support large monotonic strains. It is also known that loading is displacement-controlled, thus applied load relief occurs during wrinkle formation. Although failure can occur with only a few strain reversals, the low loading frequency provides time to react. This paper will describe the steps and tools required to define the maintenance requirements for a pipeline wrinkle or to evaluate the effectiveness of remediation techniques. The paper will focus on the results of a preliminary wrinkle model development project aimed at assembling a practical technique capable of predicting the service life of a buckled or wrinkled pipe segment. The LS-DYNA non-linear finite element (FE)-based numerical wrinkle and buckle formation and growth model, developed at BMT Fleet Technology Limited, will be described along with its validation through comparison with full-scale trials and existing design criteria. The paper also discusses the use of the FE model predicted through-life wrinkle behavior to estimate the wrinkle service life and describe the way forward for the further development and implementation of this approach.