On a free standing carport with an 8 inch, 22 foot long aluminum i-beam, would a steel 8-inch i-beam be just as strong? I am looking into it since they are cheaper.
steel is definitely cheaper than aluminum. for the same size, steel is stronger. and much heavier. it may/will require stronger support posts. you'll want to be careful not to set up a galvanic reaction where you have steel and aluminum meet. stainless steel is much more expensive. you just want to make sure your steel beams have a good rustproof coating. either zinc plate or paint.
Yield strength of aluminum vs steel beams may be a little bit higher depending on the alloy. However due to the widespread use of steel I-beams you should be able to get them for a much better price. Are you sure the existing beam is not stainless steel rather than aluminum this seems a lot more likely.
Structural steel is stronger than structural aluminum. If the structural design is adequate for using an 8 structural aluminum I beam, you can certainly use an 8 structural steel I- beam and if the price is better, you can also use a 10 structural steel light weight channel. If it is on the coast, prime it well and keep it painted. Potential corrosion trouble spots and fasteners can be sprayed with automotive undercoating.
Yes-- just make sure that your connection to the beam is secure. Since you call it an I beam -- I assume that it is steel. Don't do any drilling -- use two heavy duty c-clamps to hang your bar from.
