I want to replace 6" X 6" engineered wood beams (hollow core) with 6"X6"X1/4" mild steel square tubing to support the existing deck and roof. the over all length of each support post is approx. 17 feet vertical. The deck measures
10'X18'. Support brackets will be welded to each post for the joists etc.11ga would probably be thick enough.
Euler buckling, if you want to do are real analysis.
Figure between 3x and 10x the wood you are replacing. But you have little in the way of dampening for straight lengths, where wood will internally dampen vibrations. May need some light x-bracing, say 1.5 x 1.5 inch to within a foot or so of each end.
Should last until about the end of time, or until you forget to put drain holes near the bottom to let water (condensation, rainfall, spilled beer) flow out easily.
I am not a structural PE in any state.
David A. Smith
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