I have modelled a shell and I want to retrieve the Principle normal force on a given set of points(light blue in screenshot). Later I compare this values with values from another source(physical model testing)
The shell is oriented according the coordinate system on the sketch(red circled)
I am asking me, which one is correct in this case? Why is there such a big differnce? Shouldn’t they be similiarer? And: Is that the way to go, or am I completly on the wrong path?
Hello @Baris,
The principal and local normal forces can differ when the principal directions do not align with the local element directions.
In the attached definition, I’ve added the principal stress lines at the points you’re analyzing. These directions, taken at the mid-surface, correspond to the directions of the principal normal forces.
In your case, the local x- and y-directions are aligned with the global x- and y-directions (you can verify this by enabling “Local axes” in the ModelView component). However, you can see that the tangents of the principal stress lines deviate from these directions. 250331_ShellAnalysisForum_cp.gh (623.2 KB).
– Clemens
thank you for clarifying and grafically explaining that behaviour!
That’s why I rotated the model to this direction. Now I see, why it still differs. Thanks for taking the time!
Yesterday night I found out, there was a second drawing of the analysed model, which had a different edge beam. Now the output of the Principle Stress from the Shell Focres component aligns qualitatevly with the other two values sets. That the values closer to the edge beam differ is something I can imagine, why the value 1(463.8 kN/m) seems a bit off, even being quite away from the edgebeam is somehing I do not understand by now, but I may digging a bit deeper.
