I have some nodal instability issues which I can solve by fixing the base of the column. However, I'm trying to capture a "girt" reaction applied to the column (out-of-plane of the frame(. Therefore fixing the base produces a moment at the base, but in reality the column is supported top and bottom (pinned connection).
I could put a diaphragm at the roof, but I actually don't want this reaction to go into the diaphragm and then to other frames. I really just want to restrain the top of the column. I thought about putting in a "dummy frame" outside of the structure that could support the column out of plane, but not sure that I want to do that either.