I don't know about other users; I use a German FEM program Sofistik. I can select a portion of a Revit model and export it to Sofistik. It creates a mesh and applies loads. The only problem is the boundary conditions: if I have, for example, a three story concrete moment frame, and I select the top story columns and beams, I would like the selection to behave as a moment frame on its own...to retain the boundary conditions it has in the whole structure.

For steel braced frames, columns are usually pinned. For concrete it's usually moment connections and so on...

I think this feature is enabled in Robot Millennium, but I don't know about other FEM packages. Do any of you have experience with this?