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Recent Results
Understanding of Pipe Material Properties Including the Stress-Strain Curve Shape on Strain Demand
This recently completed research project is a key component in the PRCI Strain Based Design Program. The project team is currently completing its review of the final report of the work.
The research determined that the shape of the pipe steel stress-strain relationship can have a significant effect on the pipe strains computed using pipeline deformation analyses. A pipe steel stress-strain curve with a relatively abrupt or “sharp” elastic-to-plastic transition will lead to larger strain demands than a stress-strain curve with a relatively rounded elastic-to-plastic transition. For high strength UOE pipe material, the shape and strength levels of the stress-strain curves for material tests in the longitudinal tension, hoop tension, longitudinal compression and hoop compression directions are known to be significantly different i.e., the material is anisotropic.
Key Results
A key finding of this research is that anisotropy alone does not have a negative impact on strain demand. It is the shape rather than the degree of anisotropy of the stress-strain curves that is the most important factor influencing pipe strain demands. An important goal of this research is to apply the findings to guidance for supplemental pipe material specifications aimed at minimizing undesirable effects of anisotropy and stress-strain curve shape on pipe deformations under displacement-controlled loads.
When planning for the purchase of pipe for strain-based design applications, operators should consider obtaining representative digital stress-strain curves to compute various measures of anisotropy as well as various measures of the curve sharpness.