beam resultant forces

hi guys,

I don't know why, but when I connect a cross section to assemble model, the resultant forces and bending moments change..

I've tried it with a single beam and they don't change but with my model they do.

I attach my example model so that you can test it by yourselves.

Thanks again!

Attachments:

example.3dm, 155 KB
example.gh, 18 KB

Replies to This Discussion

Permalink Reply by Karamba3D on May 27, 2014 at 10:17am

hi Pablo,

your system is internally and externally statically indeterminate. When you change the cross section you also change the relation between bending-, torsional- and axial stiffness of the members. This results in new relations between the bending-moments, torsional-moments and normal forces in your structure.

Best,

Clemens

Permalink Reply by Nenad P. on May 24, 2022 at 4:23am

I would imagine that these changes could be small, but I am getting massive changes in normal forces (which shouldn't change if it is an ideal truss) when changing cross-sections.

Any ideas on how to get actual axial forces like you would when calculating by hand before determining the cross-sections?

Permalink Reply by Karamba3D on May 30, 2022 at 4:57am

Hi, if gravity is activated, then the normal forces will adapt to your cross section sizes.

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