my query for modelling of above grade pipelines. For one of our projects under implementation, we need to model above grade pipelines lying on sand without any additional supports i.e. bottom of pipeline is touching sand ground througout the pipeline length. Please answer my following queries:

1. Since Soil modeller available in Caesar can not be used for above mentioned scenario, what is the alternate method for modelling these pipelines.

2. In case we have to use supports at uniform distance, what shall be the maximum distance to match continuous support requirements as per above mentioned scenario.

3. How shall we define soil stiffness in your proposed alternative?

Your early reply on above queries will be highly appreciated.

Hi,
First thing that comes into my mind is
Is it required to be considered as stress critical?
Presuming it to be required as per your norms/client requirement, you can do the following things…

1. Yes, your model may not fall into buried piping category itself.
2.Defining spacing for using supports with stiffness is complex.
While calculating manually, these keypoint depends on alpha, pipe dia , soil stiffness etc…
Since your case will not fall under buried piping, above calc option is ruled out.
3.This is my opinion only (Approximate method)…
Calculate downward stiffness & ultimate downward load (manually, there are several methods available for this) and impose as “user defined downward stif” / “ultimate downward load” in buried modeler
Soil spacing is a function of horizontal stiffness (which is zero is your case), hence your spacing can be on the higher side.
Spacing actually is required to capture variation of strain VS length in that axis, which is almost nil in downward movement.

If your point restraints to model continuous soil support are not close to one another, be sure to zero out all density. This will be OK if you assume the soil will support deadweight and your interest lies in structural response due to pipe strain.