# Abaqus like 1D Internal Pipe Pressure

I was looking at the documentation for pipe (beam) elements, and I found out there is no similar implementation to Abaques Pipe Element which can have internal/external pressure.

I am calculating the displacement and stress in the pipe network subjected to internal and external pressure. Is there a way this can be done by changing the implementation?

CalculiX doesn’t have pipe elements. What’s more, its beam elements don’t use true beam finite element formulation - they are internally expanded to solid elements. Thus, likely the easiest way would be to model the structure with shell elements.

pipe section defined by outer radius and thickness, however only accepted element load along it’s strong/minor axes direction.

``````*beam section, section=pipe, elset=setname, material=matname
10.0, 1.0
``````

even the expanded result available still shown as rectangle section by bounding box.

maybe is possible, someone need to user customized the section and load (positive/negative sign).

it’s interesting me to try.

I’m curious too if hallow beam element could be useful to model piping stress.

I have tried. Pressure load on axe direction could be replaced by pressure on a “blind disc”.

Displacements and stresses don’t show peak values but certainly the square section is not pretty.

Would be nice if we could have some known result to compare.

Yes. This is the most basic use case but strangely not implemented.

However, if the 1D element is expanded internally to 3D I am worried the speed benefit PF using simplified elements is lost (?).

What do you think?

ah, i forgot to point out the capabilities of beam element faces were previously succeed in contact analysis. thanks for remembering

but eight integration points may not enough for internal/external pressure of pipe. also, i’m thinking in a different ways, seeking the possibilities using composed approach.

1D classical beam element formulation has many limitation and assumptions made. even for simple case of linear static, still questioned for curved and tapered members.

expanded beam element seems to try break the limit over classical beams. took the advantages of all nonlinearity (material, geometry and boundary) so it can be capable to do perform plasticity, contact and stability analysis.

it’s fairly common, number of equation become large and consequently in computational times of the user must concern for all these advancement.

Code aster seems to do it for 1D as well as commercial packages.

Maybe we can get inspiration from that technology:-
https://code-aster.org/V2/doc/v14/en/man_r/r3/r3.08.06.pdf

even it capable to take into account of nonlinear material (plasticity) still it seems many limitation and assumptions as mentioned before,

• small deformation
• plane of section remain plane
• shear, flexure and torsion interaction
• nonlinear boundary or contact
• local/global buckling

above limitation can be directly compared with shell/solid models.

and i did not expected the developer does rolling back any advancement of CalculiX achieved

except someone interest to extended the capabilities of user beam element (classical) were currently available. these are for completeness purpose only.

I agree. Well I am interested to extend the capabilities, but I am new to the codebase. Anyone with experience in the codebase? If I get point in right direction!

Not much experience here, but I would start with downloading the codebase and looking for the routines used for expanding 1D and 2D elements into 3D. You must trace those and the corresponding lines in the main ccx file. Also, I would look into the provided 1D beam as a user element so you can see what it needs to be functional.

I too am interested. It would be nice if Calculix had true pipe elements. I see you already mentioned that Code Aster has both the tangent and elbow/bend elements. Ansys has pipe elements. I think (but am not sure) that Nastran has both elements. Stardyne had both and of course the old code SAP-IV had both. The source code for SAP-IV is still floating around (it’s written in Fortran).

One of the critical things about the bend element is that ovaling should be taken into account.