This paper proposes a systematic approach to design a buried cross-country steel pipeline for oil transportation,based on limit states of the pipeline in operation.Yield and buckling due to primary loads and secondary loads are considered in the limit state design.A procedure to evaluate limit states in accordance with stress and strain criteria is proposed when the pipeline is applied with factored loads.The evaluated limits include the maximum stress limit for FEA with beam-elements and the equivalent stress and strain limit for FEA with 3D solid elements.The soil conditions along the pipeline are classified into three different types.Soil is represented by discrete bilinear springs for the beam-element pipeline model and represented by extended Drucker-Prager model for the 3D solid element model.The sensitivities of the limit states to the soil conditions and pipeline bend parameters were studied.Mitigation measures are taken to make the pipeline meet the proposed limit state evaluation criteria.The cost and constructibility are taken into account to expand the beam-element model to the 3D solid element model.
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