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Hi, I built a model of a frame filled with a buffer modeled through two double struts. I created a main geometry (frame) and then connected the two uprights to the frame through equaldofs. The frame is constrained to the base while at the top the nodes are constrained in the Y direction (out of plane). The problem is that in the deformation, at the top of the beam-column and strut node, the latter detaches and does not follow the deformation of the beam-column node of the frame. At that point I have a condition of continuity through the equaldof and the constraint condition given to the beam-column node of the frame. I can't understand the reason and I tried to rebuild the model several times but without solving the problem. I'm sending you some images of the vertical analysis that make the problem clearer. How can I do it? Thank you.

It seems the transformation handler cannot handle the equalDOF on top with the Fix in Uy DOF only (even if that fix is on the master node, which is what OpenSees wants...).

When you see strange behaviour with your constraints, try to use the Penalty (or the new Auto handler).

Anyways, if you remove the fix in Dy at the top nodes it will work.
Otherwise use Penalty (but you have to calibrate the penalty value).
Or the Auto handler that automatically computes the penalty values (this will be the topic of our next webinar)