If I have a square of four beams modelled - which has a plate sat on the top of the beams - how do I model the plate sat on the beams?
The important thing to do is add more nodes along the beams where the plate elements can connect to the beam elements and segment those beams at the same nodes. Wherever the plate and beam share a node they will be linked. The more nodes you have, the more continuous the behavior.
Above is a snippet.