Wind loads with STAAD PRO

[Polecat]

I am using STAAD PRO V8i to model an awning consisting of an aluminum sqr tube frame covered with a canvass membrane. It measures about 7.5 x 9 ft and is supported by a post on one corner and two adjacent walls. Since there was no awning type material listed by STAAD, I used an aluminum membrane 0.03" thick to cover the frame.
My problem occurred when I tried to apply a wind pressure to the membrane --- STAAD keeps giving me an error message when I try, no matter how I approach it. I need to apply a 29 psf wind as uplift to the underside of the membrane.
Are there any STAAD Gurus out there who might be able to enlighten me? I can provide the STAAD *.std file if that would help.

Polecat (Structural)

http://www.spiraleng.com

 

[JedClampett]

From my limited experience with STAAD, but I've never had much success with very thin members loaded perpendicular to their thickness. STAAD didn't recognize the second order large deflection analysis of the member (where it goes into tension) and I ended up with huge deflections and stresses. I tried fooling around with some alternate analysis options, but none of them worked out.
You might have to make some educated assumptions on the load distribution and go from there. Or call a fabric engineering firm and see how they do it.

 

[JedClampett]

Also see thread507-362452.

 

[Polecat]

Jed
Thanks so much for guiding me to the other thread. The answers helped immensely. Since my awning is srapped down only at the perimeter of the frame, I think I will just divide the load into 4 triangular wedges and apply one to each of the four sides. That way STAAD won't have to go into an internal fit about excessive deflections and 2nd order analyzes.

http://www.spiraleng.com