thschrader wrote: ↑Mon Feb 11, 2019 2:51 pm Use mesh refinement at the cracking zones.

how can I do?

The problem is that the structure always yields in the 3 points indicated in green.
And I do not know if increasing the thickness of the tubular I can solve the problem.

in fact, the meshing phase lasted less than 30 minutes and did not give me any errors.
I will try however to simplify the structure to try to make the analysis work.
But I have a doubt: when I import a file step the software sees a solid or only sees the surfaces that compose it?

ok, I try to eliminate everything that is not needed for analysis and I close all the holes.
But the problem remains that for the analysis this structure has no volume.
Can there be an import problem with step files?

the problem is that this structure does not bear the load.
My task is to evaluate if 50x5 square tubulars can solve the problem or if you need something else.

what do you mean?
I don't know the fem analysis well..

the freecad file is 117 mb, perhaps because of the mesh.
I attach the step file from which I start.

how can I do a FEM 3D analysis ??

I attach mesh info..