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Buried pipeline (Beam embedded in solid)

Posted Nov 16, 2018, 3:29 a.m. EST Structural & Acoustics, General, Geometry Version 5.3a 3 Replies

Daniel Fjæstad
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Hi,

I am trying to model a pipeline buried in sand. Elastic properties of the sand is assumed.

I was able to do this succesfully using shell-solid as shown in the attached file "Buried pipe (solid-shell).mph". This is exactly what I want to model and the results are good. However, I want the pipeline to behave like an Euler-Bernoulli beam.

I have tried to make a buried beam in the file "Buried pipe (solid-beam).mph" but the simulation fails. I think the connection between the beam and the soil is not properly defined. I want continous contact between the beam and the solid.

On a side note, I would like to make the connection between the solid and the shell smooth in the first model. Is this possible? I see no such option in the Solid-Shell Connection tab.

Best regards,

Daniel

3 Replies Last Post Nov 16, 2018, 10:37 a.m. EST
Henrik Sönnerlind COMSOL Employee

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Posted: 5 years ago Nov 16, 2018, 7:05 a.m. EST
Updated: 5 years ago Nov 16, 2018, 7:05 a.m. EST

Hi Daniel,

You need to use the same technique as is used for the reinforcment bars in

https://www.comsol.com/model/concrete-beam-with-reinforcement-bars-10440

(The example is also available in Application Libraries for the Geomechanics module.)

There is no geometrical object in the solid block to which you can couple the beams using a multiphysics coupling (which does not contain an option for edge-to-edge connection anyway, even if you were to build your geometry differently).

What do you mean more in detail by "make the connection between the solid and the shell smooth"?

Regards,
Henrik

-------------------
Henrik Sönnerlind
COMSOL
Hi Daniel, You need to use the same technique as is used for the reinforcment bars in (The example is also available in Application Libraries for the Geomechanics module.) There is no geometrical object in the solid block to which you can couple the beams using a multiphysics coupling (which does not contain an option for edge-to-edge connection anyway, even if you were to build your geometry differently). What do you mean more in detail by "make the connection between the solid and the shell smooth"? Regards, Henrik
Daniel Fjæstad
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Posted: 5 years ago Nov 16, 2018, 7:19 a.m. EST

Hi Henrik,

Thank you for your reply.

My model is actually a modification of the Concrete Beam With Reinforcement Bars file. I will look at it again, but it sounds like I might need a different approach.

If the pipe is smooth, it allows the soil to ‘‘slide” against the pipe. As far as I understand, my model is based on full compatibility between the pipe(the shell) and the soil(the solid) and does not capture this behavior.

Best regards,

Daniel

Hi Henrik, Thank you for your reply. My model is actually a modification of the Concrete Beam With Reinforcement Bars file. I will look at it again, but it sounds like I might need a different approach. If the pipe is smooth, it allows the soil to ‘‘slide” against the pipe. As far as I understand, my model is based on full compatibility between the pipe(the shell) and the soil(the solid) and does not capture this behavior. Best regards, Daniel
Henrik Sönnerlind COMSOL Employee

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Posted: 5 years ago Nov 16, 2018, 10:37 a.m. EST

Hi Daniel,

You can choose to connect only the transversal displacements, and not the axial displacement. In the context of the Concrete Beam With Reinforcement Bars, that would mean deselecting the x-translation degree of freedom constraint (which of course would make that model meaningless, since it is the only importance coupling).

Regards,
Henrik

-------------------
Henrik Sönnerlind
COMSOL
Hi Daniel, You can choose to connect only the transversal displacements, and not the axial displacement. In the context of the Concrete Beam With Reinforcement Bars, that would mean deselecting the x-translation degree of freedom constraint (which of course would make that model meaningless, since it is the only importance coupling). Regards, Henrik

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