Advancements Regarding Capacity Prediction of Strain-Based Pipelines

摘要

In areas of large ground movements, pipelines may be subjected tolarge longitudinal strains. It is imperative that strain-based designmethods are developed to aid in the design and construction of suchpipelines. As reported previously, a comprehensive experimental andnumerical program to characterize the tensile strain capacity of weldedpipelines was undertaken. Models were developed that are capable ofpredicting strain capacity based on input parameters such as pipegeometry and properties, internal pressure, weld flaw geometry, weldproperties, and high-low misalignment. These models (equations) havebeen validated against a data base of about 50 full-scale pipe strain teststhat included a broad range of geometries and pipe grades (X60-X80).In the current paper, further developments are described. A pressurefactor has been incorporated into the models. Whereas the previousmodels assumed that the circumferential stress from internal pressurewas 80% of the specified minimum yield strength (SMYS) of the pipe,the pressure factor allows the calculation of strain capacity as afunction of pressure that results in hoop stresses from zero to 80% ofSMYS. Additionally, ranges for pipe yield-to-tensile ratio and weldtearing resistance curves (R-curves) have been expanded. Newequations and associated flaw assessment diagrams for example casesare provided.