Load-Carrying Capacity of Welded Slip Joints

Abstract

Welded slip joints, which are used in many high-pressure water transmission pipelines, are vulnerable during earthquakes to axial compressive loads generated by ground movements. This paper analyzes two failure modes associated with: 1) yielding in the vicinity of welded connections, and 2) plastic flow in the curvilinear, belled ends of the joints. The analyses indicate that the axial load causing plastic deformation is from three to five times smaller than that causing yield in straight sections of pipe. Typical slip-joint dimensions are studied, and recommendations are made for improving the axial load-carrying capacity by 50 to 100 percent.