Joint Strength or "Efficiency" Factors of Steel Lap Welded Joints for Use in Water Conveyance

Abstract

Joint "efficiency" factors are proposed for pressure vessels, piping, and pipelines by ASME standards. For the particular case of non-radiographically-tested lap-welded joints, a low value of joint "efficiency" is proposed. This low value has raised some concerns regarding the use of welded lap joints in geohazard or seismic areas, where significant axial stresses and strains are developed, as a result of ground movement. The paper discusses the joint efficiency concept, mainly in relation with the corresponding failure mode of the pipeline, based on recent experimental observations and numerical simulations. The conservativeness of the ASME "joint efficiency" values for lap-welded joints is demonstrated. Furthermore, based on experimental evidence, it is shown that lap welded joints can sustain significant deformation, without loss of pressure containment. The conclusions from this paper support the argument that lap welded joints constitute a simple, efficient, and economical solution for pipeline joints in seismic areas. © 2019 American Society of Civil Engineers.