[aharri]

Hi
Yes but if anything the eccentricity should decrease the buckling factor, not multiply it by a factor of 10. Also, it is very little (4 mm) off center.

For the next stage of my thesis work the solid model could be more useful. Could you please suggest how it should be modeled in NextFEM? Will it be enough to just make the element proportions closer together?

Best regards

[aharri]

Hi

Model attached. The restraints differ a bit in comparison to the surface models, as the solid model has some eccentricity. Should this be modeled with two layers of solids and then the supports will be in the middle nodes? Although I don’t believe this is the reason for such high difference in buckling factors.

Best regards

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[aharri]

Hi

I will upload them a bit later. If you are interested, here are the results of my analysis with plates/surfaces in various programs. Nextfem is now very consistent with RFEM, when using quads (50×50). Only interesting thing I noticed based on the analysis, is that Staad calculates buckling differently with very narrow models, please see “1000.png” that is attached.

Best regards

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[aharri]

Hi
I tried it and verified it now gives the same result on quad at least for one case. But there seems to be some occasional errors when solving the model, and I can’t pin-point why. Sometimes re-running the solver works. Another example: I took one model that had 1000×1000 elements and I kept dividing them, and at smaller size the solver refused to work (I think it was 50×50 or 100×100).

Unfortunately my license doesn’t allow parametric solving and I do not have python extension installed.

What about 3d solids? With them I get very high buckling factors. Maybe verify those work too, after the quad and tris are sorted.

PS. Could the download-page say which sub version it is, too?

Best regards

[aharri]

Hello

Thank you and I’m glad that my feedback resulted in finding a bug.

Yes, I have the same mesh size and loading, although in RFEM the supports have the type of “line support”, which propably translate to mesh nodes having node support.

Would I be able to use just one quad element and have fine mesh for calculation? When I was trying it with this method, it calculated strentgh from the element and mesh -> intersection capacity was doubled. Then I ended up doing one quad element, dividing it, meshing it so that triangles were used and I deleted the original quads. This way I could have visually pleasing mesh created.

Best regards

[aharri]

Hi

Yeah sure, I attached one of the models.

The quad elements gave very low buckling factors such as 0.200.

Best regards

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[aharri]

Hello
Thank you for the quick reply.

When I visually examine the buckling shapes they match. Every program does things a bit differently, but I tried to model them all as closely as possible.

When I use the query tool, there is no type currently set for the triangles. After I rotated the model -90° around global X and changed the element types to plane stress I get the solver error below:

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
NextFEM Designer v.2.30
Model name: panel-3000x2000_grid-1000×1000-test
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Number of nodes: 18
Number of elements: 24
Problem size: 144
Number of restraints: 12
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Starting analysis for case Wind +X
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Collecting model data… Done.
Launching…
Solving …
Real time consumed: 000h:00m:00s
User time consumed: 000h:00m:00s

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
End of execution for load case Wind +X
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Starting analysis for case Buckling
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Collecting model data… Done.
Launching…
Assembling stiffness matrix
Assembling variable loading
Solving linear static problem
Assembling initial stress matrix for variable loading

Error:Method computeInitialStressMatrix is not implemented

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Execution finished at 01/16/2024 19:55:20
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

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