Tom:
I'm in the eastern panhandle of WV and am about to embark on the same thing. Building a 24 X 24 Garage monolithic slab on grade.
At this point, I know that the building code calls for a minimum of 4 inches of crushed stone under the slab. I can't recall if the code has specs for the...
The American Wood Council has a document that has all the information you should need to determine the correct sizing for your beams and joists.
Follow this link: http://www.awc.org/pdf/STJR_2005.pdf