Stainless Steel Grill

[drm4444]

I have been asked to design a 7'w x 6'h decorative grill composed of 3/4"x3/4" stainless steel tubes (36 ksi) designed for a wind pressure of 85 psf. The horizontal 7'-0" long tubing is rotated 45 degrees, spaced at 2.35" o/c & welded to a angle metal frame at the perimeter. Some grills will be placed in front of louvers while just in front of a false louver (wall) at other locations. Does anyone have any thoughts on design criteria including how the wind load acts against the angle at 45 degrees, deflection criteria, vibrations concerns? I have the options of using 1/16" or 1/8" thick tubes and possibly interrupting the horizontal members with slender vertical bars that are only one inch deep but the architect would rather not. Thanks!

 

[JAE]

I think ASCE7 has a table for various shapes (rectangular, circular, and rectangular at 45 degrees).

The thing with screens like yours is that the wind pressure is tough to determine with all the little holes in it - is it the ASCE 7 loading on the projected area?

I'm not so sure - seems like the turbulence would almost make for a pseudo-solid screen behavior with wind pressure. Plus someone somewhere will put a solid tarp or banner across it and then what do you have? A sail.

 

[Ron]

I agree with JAE on the turbulence issue. I would apply solid loading for the structural loading in the horizontal pickets.

Be careful about sound and vibration. You might have to foam-fill the pickets to cut down resonant vibration and the wind, and low wind speeds might cause "whistling".

Do a mock-up and put it in front of a large fan to check whistling effect.

 

[Bobber1]

I suggest designing it as a solid surface if there is any likelyhood that someone may erect a sign or similar on it.