Interior mezzanine structural design

I'm designing a 22' x 8' x 8'6" high mezzanine, and want a steel 4 post frame to support it --
flooring material will be 1 1/4" wood decking. The 4 posts (I'm assuming either 3" SQ or 4" SQ) will be approximately in a 14'x 8' grid (flush on the 8' dimension and recessed to create 4' cantilevers in the 22' dimension)

so what size beams will I need to span the 22'? I'm thinking this needs to be a "bolt together" structure (with a few welded components) so we can assemble easily in my existing building.

Suggestions? I know the columns will need plate bases to sit on the existing 5-6" slab.

Dan, not uncommonly for first time posters, you have omitted some of the really important stuff. What are you putting on the mezzanine floor? Machinery, desks, people? How many or how much? What is the load? Static or live loads? Fork lift loading pallets of stuff on it?

Too many unknowns for me.

Pink. this is a "balcony" if you will in a "great room" of a weekend place -- loading will be some furniture and people --
I'd say no more than 6-10 people ever (live load), and chairs and maybe a bed or cot (static)

so the steel frame will provide rigidity, and will bolt to some existing purlins