Pipeline Design for Predetermined Levels of Seismically Induced Differential Settlement

A series of analyses were completed to evaluate the maximum stress and strain in a pipeline as it experienced an increasing amount of seismically induced differential settlement. These analyses allowed the development of tables for use by pipeline designers that specify the pipe wall thickness and joint type required to accommodate the anticipated differential settlement over a specified length without completing location specific analyses. The finite element software Abaqus was used to evaluate the stress and strain levels in the pipeline as the magnitude of seismically induced differential settlement increased. The maximum stress and strain reported in the pipeline model was compared with allowable limits for butt-welded and lap-joints for a range of pipe wall thicknesses. This analysis was completed for 48- and 60-in. diameter pipes and considered pipelines bearing directly on liquefiable soil and pipeline embedded in a non-liquefiable soil “crust” overlaying a liquefiable soil.