Strain-Based Design of a Large-Diameter Steel Water Pipeline Crossing Ground Settlement Areas

This paper describes the structural design of a large-diameter buried steel pipeline crossing two areas of substantial soil settlement, which impose fault-type actions in the pipeline. Those ground-induced deformations are associated with the development of high levels of strain, well beyond the elastic limit of the pipe material. The present paper describes the application of “strain-based” design approach, towards economically efficient solution, while increasing pipeline safety and reducing risk. Strain demand is calculated first, using a global analysis, through finite element models, developed for the purposes of the present design. The numerical models employ “pipe elements” to simulate the pipeline and “soil springs” to describe the soil and its interaction with the pipeline. Subsequently, the ground-induced strains are calculated and compared with the allowable values. The design makes use of a newly developed concept, the “projection” concept, which increases pipeline resilience and improves lap welded joint performance. The effects of soil conditions on pipeline performance are also discussed.