This is a question regarding my own house.  I am designing an outdoor deck, and am considering using steel understructure instead of traditional wood.  I want to minimize the physical thickness of the structure to enhance visibility from the lower level.  The decking surface will be traditional natural cedar.

Is there a rule of thumb which approximates properties of steel beam with dimension lumber?  eg what size ibeam performs similar to, say a 2x8 joist?

(I am a retired "swiss army" engineer. I do twenty things, none of them well.  Actually, my background is in papermaking and more process oriented)

Thanks for any help!

Bill