Does anyone have advice for modeling piping that "rolls" over hills without fittings over long distances? I have been told that this is called "roping" pipe over the topography of the land.

The piping will be properly supported to stay within code deflection limitations. But over large horizontal distances, the piping will actually be rising or falling gradually (bending). Would this affect stress/loads in any way? Or can an assumption be made that the pipe bend angle is so small (over the large distance) that the small bend is negligible?

If this cannot be ignored, then this seems to be more of a modeling issue that I am not capable of at this time. Maybe someone has come across a COADE/Intergraph document that explains something like this?

If you know the geometry you can figure out the radius of curvature for the pipe, roped bends have a very large radius. From there statics textbook will give formula for bending stress, this can be manually added to the Caesar calculated stresses, keeping in mind roped vertical bends will create max bending stresses at 12 and 6 o'clock, while bending stresses in a flat layout with horizontal changes in direction max at 3 and 9 o'clock positions.

Thank you Dave. I appreciate your response and explanation.

Calculating the stress shouldn't be a problem. I guess where I am confusing myself is whether or not these large bends need to be graphically modeled in the Caesar input.

(My thinking:)
On the one hand, if I DO graphically model the large bends(which would be very time-consuming and a headache), then Caesar would already calculate the stress for me since it knows the piping geometry. Making the hand calcs unneccesary?
On the other hand, if I do NOT graphically model the large bends, then this would justify manually entering the calculated stress at the max stress locations?

Any advice?
-Thanks

If you just graphically model them as large bends in Caesar, then Caesar will assume these are effectively just very very large radius fittings, ie. pre-bent pipe. The roped bends are elastically bent, the pipe would try to straighten out if you dug it up. To really model them in Caesar, I think you would have to model the piping as straight, then impose displacements on it to get it to the roped shape you want, then the bending stresses due to roping would appear in the modelled pipe results.

Is this worth the effort? I don't think so. Unless you are going over a mountain range, I would model the pipeline layout as flat and just manually add on the roping bending stresses to the Caesar results after.

What diameter pipe are we talking about? Would have to be significant OD for lay of the land roping to have much effect.

If the pipe is not pre-bent (pulled), then if you know the relative elevations of the supports then you could put cnode displacements at each support. I have not modelled this type of pipe before, would this be an appropriate technique?

Thank you for the help. It is much appreciated and I will take this into consideration for future projects.
(By the way, the nominal pipe diameters I have been dealing with typically range from 2" to 8")

-Thanks