Tensile and Compressive Strain Capacity of Pipelines With Corrosion Anomalies

Abstract

Strain-based design and assessment (SBDA) methods have been developed to address integrity issues for pipelines subjected to ground movement hazards. The current practice of strain capacity assessment focuses on the tensile rupture of girth welds and compressive buckling of pipes. The integrity management of in-service pipelines often involves assessing pipe segments with anomalies, such as mechanical damage and corrosion. The existing strain capacity models do not yet include the impact of those anomalies. This paper covers a part of the outcome from a comprehensive research effort aimed at developing assessment procedures for pipelines containing corrosion anomalies and simultaneously subjected to large longitudinal strains. The resistance to tensile rupture and compressive buckling are the focus of the paper. Recommendations for the assessment of strain capacities were provided based on numerical analysis which identified key influencing parameters and controlling mechanisms. Full-scale experimental tests were also conducted to demonstrate the identified mechanisms and evaluate the assessment methods. Both numerical analysis and experimental test results demonstrate that: (1) corrosion anomalies can significantly reduce the tensile strain capacity (TSC) and compressive strain capacity (CSC) of pipes, (2) in addition to the depth and longitudinal length, the circumferential width of the corrosion anomalies has a significant impact on the TSC and CSC of pipes, (3) circumferential-groove corrosion anomalies reduce the tensile strain capacity more than general corrosion anomalies of the same depth and circumferential width, and (4) general corrosion anomalies reduce the compressive strain capacity more than the circumferential-groove anomalies of the same depth and circumferential width. The analysis and experimental test results shown in this paper can support development of SBDA procedures and guidelines of pipelines subjected to large longitudinal strains.