Compressive strain limits of composite repaired pipelines under combined loading states

Recent literature and the industry have widely accepted the benefits of strain-based design in regards to steel pipelines. In accordance with the recent increase in the use of strain-based design for pipelines, in this paper, the authors investigate composite repaired pipelines and its applicability in reference to the strain-based design. In an earlier work, the authors found that under combined loading conditions, a repaired pipe would tend to buckle locally in a location adjacent to the composite repaired wrap. In an attempt to limit the initiation of local buckling response in composite repaired pipelines, the compressive strain limit was investigated. For that, a finite element study was conducted. The results clearly showed that the maximum strains would not occur in the post-repaired defect region. The local buckling would however occur in the unrepaired (undamaged) section of the steel pipelines. An experimental study was also conducted on Fibre Reinforced Polymers (FRP) repaired pipelines to verify the finite element results. A parametric computational investigation was also conducted to understand the limits of composite repair wraps.