L52193 Guidelines on Tensile Strain Limits

There are no generally accepted industry standards that allow the determination of the maximum tensile strain limits of girth welds. Most ECA (Engineering Critical Assessment) codes are stress-based and cannot be used if the longitudinal strain is greater 0.5%. The objective of this project was to develop guidelines on tensile strain limits of pipeline girth welds as a part of the overall development of seismic design guidelines. The loading on pipelines from seismic events is largely displacement-controlled. Such loading can impose high longitudinal tensile strains on the girth welds of pipelines. Therefore, it is necessary to define tensile strain limits of girth welds in the seismic design guidelines. This work represents a systematic investigation of various factors affecting the tensile strain limits of pipeline girth welds. By using the concept of crack driving and apparent toughness, baseline tensile strain limits have been established for a wide range of pipe grade, wall thickness, defect size, and material toughness.