We design a lot of hall buildings with just unbraced cantilever concrete columns with light steel construction of the roof on top of it. Sometimes there must be a fire resistant wall to isolate the new building from existing one, so we use mineral wool panels attached to these concrete columns and that's it.

The only problem is that I can't find a way to calculate what thickness of cover I need for design fire resistance of 120-240 minutes - there is no word about it in my native books. It's a matter of people safety and not a competition, so engineers should share their knowledge in science enivronment.

There are tables for non-sway, mainly compressed columns, when my cantilever is mainly bent and unbraced, so I thought if maybe I should use tables for beams.

If you have any thoughts on this subject and want to share them, it would be much appreciated!