Stress Concentrations Factors in Welded Tubular Sections and Pipelines

In this paper analytical expressions for stress concentration factors in pipes subjected to internal pressure and axial forces are presented based on classical theory. This includes longitudinal butt welds in pipes made during production of the pipes and circumferential welds that can be made during pipe lying. It also includes pipes welded together from sections with different thicknesses. The effect of fabrication tolerances in simple butt welds is assessed. Analyses based on classical mechanics are compared with results from axisymmetric finite element analyses for verification of the presented methodology. Larger pipes are fabricated from plates with a longitudinal weld. This fabrication process introduces cross-sectional out-of-roundness in the pipes. An analytical expression for the bending stress in the pipe wall due to this out-of-roundness is presented.