The majority of pipeline design codes are based on stress-based design methods. Although conventional stress-based design covers most pipeline applications, it does not cover the design of pipelines that may experience high strains like those of the deepwater GOM and Arctic regions. Similarly, high strains can occur to most any offshore pipeline due to ground movement, unsupported spanning, and seismic loading therefore an exacting site-specific analysis including loading conditions and material mechanical properties is needed to maintain the acceptable level of pipeline safety needed. This research project investigated the use of strain-based design of pipelines and provide a guidance document to better assure safe and pollution free operations.
Phase I was completed in 2003 and developed a best practice Guidance Document on Strain Based Design of pipelines to cover design, assessment, and testing guidelines for designers of pipelines that may experience high strains in service. See Phase I final reports AA and AB below.
Phase II, which began on July 28, 2004 and was completed in January 2007, refined the Phase I Guidance Document by providing further analysis and guidance in the areas of pipeline material specifications, welding specifications, as well as determining local stress-strain curves, provide material and welding guidance for strain based design, and develop realistic choices in finite element models to check the effects of combinations of soft regions, internal pressure, and axial strain. Collaboration between EWI and Engineering Mechanics Corporation (Emc2) of Columbus, OH was highly effective in assessing the effects of both softened HAZs and internal pressure on fracture resistance for high-strain applications since Emc2 is conducting a parallel project on fracture assessment of pipe girth welds.See Phase II final reports AC and AD below.