Quonset huts are deprecated. I did a GIS on
https://www.google.com/search?q=us+s...ns+and+garages and scanning the thumbnails, I see brands like ussteel, steelmaster, steelarchbuildings and lots of distributors. The technology is a single sheet of steel—corrugated, then folded, then arched. The result is rigidity that obviates the need for any framing.
My favorite:
http://www.steelmasterusa.com/find-local-buildings/steel-buildings-in-north-carolina/
Harbor Freight has a 10x20ft canopy for $149, recently on sale for $109. In '95 (20yrs ago, yikes!) I got one and replaced the six 6' legs with 10' lengths of Cyclone fence top rail. And tarped the sides. It had more space than a shipping container for less than $200.
I still have half of it (5x20) recovered in corrugated metal as a cover between my trailer and carport. I laid the corrugations lengthwise because it was easy; but it would shed rain water better if the corrugations ran the short way.