SteveB wrote:
I want to put up eight three inch square by .120" thick posts twenty feet
long, about two foot into concrete piers. Four of them would form a 7'
square in the center, the other four would form a larger square of about
15". I want to stand them on end. This is for a hot tub/observation
platform.

Where can I find the compression strength of that tubing? I'm sure this is
going to be way strong enough, as the spa is about 300 gallons. So, that's
a little under 3,000# for spa and water. There would be multiple bracing on
the posts, both to each other, on the horizontal and on the diagonal. I
believe a simple box with an X in the middle would give it sufficient
strength to keep any lateral movement to a minimum. 1/4" would be over
double the price, and overkill, IMHO.

Steve



Have a look in Machinery's Handbook, Steve.

If you haven't bought your steel yet, I'd consider bumping it up to .180"
wall (3/16").

The issue won't be strength, it will be buckling and also corrosion. If it
were my design, I'd plan it to bolt together and take all the pieces to be
hot dip galvanized, and then build it with galvanized parts. But steel
columns fail by buckling, and the way to avoid buckling is by reinforcing
in your design.

GWE

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