Onshore and offshore pipelines may be subjected to mechanical damage during installation and operation due to environmental loads, external forces and third party interference. Pipelines in offshore environment may be prone to mechanical damage from events such as ice gouging, frost heave, and seismic fault movement. For conventional pipelines, the assessment of mechanical damage plays an important role in the development of integrity management programs that may be of greater significance for pipeline systems located in remote harsh environments and that are more prone to anchor drag, seismic loading and ice gouging.
This study examines the effect of dents and corrosion loss on pipe mechanical response using continuum finite element methods. ABAQUS/Standard (6.10-1) environment was used to simulate damage events and pipe response. Modelling procedures developed and calibrated against physical and numerical data sets available in public domain were reported previously in Hanif & Kenny 2012, 2013. Once confidence in numerical procedures was established, an analysis model matrix was established to account for a range of influential parameters including pipe/indenter geometry and pressure factor. A nonlinear multivariate regression analysis was conducted to develop strain based empirical tools that characterize the effects of local damage and applied loads on pipeline mechanical response for unconstrained dent conditions. Coupled affect of dent and artificial corrosion loss (in terms of wall thickness reduction in the damage zone) was also analyzed and a sensitivity study was conducted to see the effect of percentage wall loss on pipe response. Finally, operational parameters were varied and resulting stress concentration factors were calculated, that took into account indentations and wall loss, to predict fatigue life of dented pipe segments for both constrained and unconstrained dent conditions.