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After importing the SAP2000 structural model, go to Define>Load cases to modify the GR weight case to specify the Mass source, and also add gravity-direction load patterns imported from SAP2000 which can potentially effect affect piping vertical displacements. Equipment loads, for example, are assigned to the structure, not piping, but they can nonetheless cause vertical (and lateral) displacements on the support structure which affects supported piping and therefore can affect piping code stress calculations and end reactions.
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Structural analysis models typically include preliminary piping weight and friction loads. Smaller diameter piping (<12" NPS) is modeled using distributed gravity-direction loads on the beams based on tributary area, and larger diameter pipe loads are usually assigned as concentrated point loads or equivalent frame point loads. Structural models treat pipe friction as an assigned load, typically 10% of the weight load. Friction is not treated as a load in piping stress models, but as a nonlinear boundary condition which is a more rigorous approach. All of these preliminary piping loads in the structural model ignore load redistribution due to thermal displacement and other applied loads. That's why structural engineers need realistic pipe support loads from the piping stress team which account for thermal displacements and nonlinear pipe support behavior.
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