To answer your question accurately, I really need to get a copy of your job - please feel free to e-mail it to me at ray@coade.com.

In the mean time, assuming the load cases you are questioning are:

1) W + P1 (SUS)
2) W (SUS)

I would expect to see pretty much identical results for displacements and restraint loads. There are a couple of things that could cause (large) differences though:

• If you have an untied expansion joint, the pressure thrust could cause significant displacements and resulting loads when pressure is included, but not in the weight only case.
• As mentioned in the previous post, if Bourdon pressure effects are turned on, the pipe will experience displacements when pressure is included, but not in the weight case.
• Depending on the magnitude of the pressure, the "pressure stiffening effect" on the stiffness matrix could affect the results.

There may be something else I just haven't thought of, which is why I'd really like to look at your job.

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Regards,
Richard Ay (COADE, Inc.)