On Tue, 17 Jun 2014 16:22:19 -0400, Ned Simmons wrote:

On Tue, 17 Jun 2014 18:18:02 +0000, Jim
wrote:

I'm erecting a shade sail over a patio and planning to use 4"x4"x1/4"
steel tubing on the four posts that will carry the fabric. The fabric
will be tensioned so that it barely flaps in anything but a very strong
wind. I'm told there will be between 2000 & 3000 # pull at the
connection points.
The tube steel will be embedded in concrete 3' or more below grade
depending on the height out of the ground. Two of the tubes will be 9'
above grade and opposite from one another. Another will be at 10' above
grade and the opposite one, the highest, at 11' above grade.
Can anyone tell me if A500 B grade 4"x4"x1/4" tubing will do the job?

If I'm interpreting your description properly (that's a big if), the
tubing is nowhere close to strong enough, even if the footings are
adequate.

Come to think of it, the tension on the tube walls at the base of the 11'
section is something over 100,000 psi. Even if it didn't buckle on the
compression side, it'd bend right over.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com