concrete plank or other alternatives for small residential parking deck over workshop

I have a small hillside lot site that I would like to put a 30x30' building on, with machine tools on the (walkout) 1st floor and parking for 2-3 cars in an enclosed garage ABOVE. There is not room for a larger footprint. The lower level is level to the street on one side of the lot, and the upper level is level with another street on the opposite side of the lot, so it would be well suited with regards to the grading, but I would like to have as few support columns as possible. It looks like 30' span concrete planks with a center steel beam and a single center column would be one solution; would that be possible and what other alternatives are available for this application?