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Following is a simple example illustrating the effects of P-delta with large displacements which users can easily reproduce with their own piping stress program. Pipe section OD 6.65625" wall thickness .188", A106-B, fluid contents specific gravity 1.0 (water), no insulation. 80 ft. span of unsupported pipeline divided into 5 ft. segments. Anchors on each end have moment releases with rigid fixity in all 3 translational directions. That is, anchors are rigid in global X, Y, and Z direction with no rotational restraint stiffness.
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The CSiPlant model we used can be downloaded here P-Delta Large Displacement Catenary Example.cpdb
We would welcome challenges from any and all users of Caesar II , AutoPipe, Rohr 2, Caepipe,, Triflex, and Pass-Start Prof, to compare and contrast their results with results from CSiPlant. If your piping stress program is incapable of properly considering second order P-delta results, then results will not be realistic in some (many?) designs, particularly with analysis of buried and subsea pipelines.