Node constraints and secondary group

Hello. Is there a way to put node constraints in a secondary group?

NODE 10 FIX KF NR1 10110 DX 0.919971 -0.391987 0

I decided to perform a construction stage analysis with secondary groups and the only thing that I cannot put there is the node constraints.


Don’t think so (correct me if I am wrong).
You could however create a (very stiff) spring connection between nodes and put that in a secondary group.

On another note:
CSM and secondary groups can be a bit shaky.
Certain elements can be in several secondary groups at the same time.
Thus activating/deactivating and applying creep/shrinkage on a group is not necessarily unambiguous.

So be sure to check that your input is interpreted correctly

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Hi, thanks for the reply! Unfortunately, if I understand correctly how the springs work, I need to replace each rigid body with 3 springs in three degrees of freedom, because when the master rotates, the spring transfers the rotation to the slave, and not a linear displacement (as a rigid body does) when there is only one spring. (see picture)

Yet another possibility is the named “rigid body”: a beam with a special (rigid) cross section (for instance only a SVAL-section) and with a special material (without weight) and/or beam-hinges if necessary.

Yes, exactly.
A rigid body connection suppresses movement in translations (PX/PYPZ) and rotations (MX/MY/MZ)
Thus you need 3 springs that all have a linear (translations) and rotational stiffness.

Or you coluld use a dummy/rigid body element as ragl suggested.
This has the advantage that for a maximum force (e.g. Pz), you also receive accompanying forces when using maxima.

Looking at your picture though it seems that your top flange and is not connected to the web, which is normally not what you want.
In case you need to fix this -> quads/beams must meet in system lines (normally center unless otherwise defined)

ragl, thanks for the idea, but I’m not 100% sure that a super stiff beam will not introduce errors into the stiffness matrix (numericaly not safe method)
sfr, The picture I attached is not my real construction, but only a demonstration of the idea. To enter elements, I use SOFIMSHA, that is, nothing “intersects” actually, I create nodes and elements directly.
Anyway, I’m glad you answered :slight_smile: