Wind Pressure Calculation 1

[brut3]

I am currently designing an Aluminum framed panel that will contain an aluminum mesh screen and have been asked to provide calculations to verify that the panel can adequately resist the applied wind pressures of the building as well as the dead load of the frame itself. The real question is involving the aluminum mesh that will infill between all the framing members. For the wind pressure calculations would it be accurate to assume that the the effective wind area will come from the mesh manufacturers data of the effective free area for this particular product? I don't want to kill myself by assuming that the panel is assumed to be solid unless this is common practice or completely necessary. Any input will be helpful, thanks in advance.

 

[ron9876]

Depends which code you are in. FBC has detailed info.

 

[brut3]

What Chapter in the FBC?

 

[par060]

naa use the area of the whole mesh...it will get full of ice or some other nonsense

 

[dhengr]

tbruton3:
That’s a wind tunnel problem. Depending upon the shape and open area ratio of the mesh, I’ll bet you could get a wind loading pressure multiplier much greater than one. What with the positive pressure on the face, the suction through and on the back face, and the negative pressures curling around the edge of the panel and framing. Mind you, this is not intended to scare you.

 

[JAE]

What happens when someones canvas sign blows off and hits your mesh - you have a sail!

 

[racookpe1978]

As above, use the whole (not "hole" area!!!) of the mesh.

The mesh, to a wind approaching it, looks like a solid because each bar (mesh piece) entraps a substantially larger area than its apparent surface area. Put small pieces next to each other and the "corners" trap even more, so the effective hole becomes much, much smaller than the "apparent" hole.

Worse, mesh screens are not "aerodynamic" (wing-shaped) so each interaction is even more enhanced,

 

[dhengr]

Robt>> Exactly, and testing would probably lead to a multiplier great than one on the face area. You are trolling around here about one step and 30 seconds ahead of me. Look back at the thread on 1" foam insulation.

 

[Ron]

Use Fig. 6-22 in ASCE 7, with the solid area to gross area ratio as the wind loaded area.

If you are using any solid panels, make sure they are removable and must be removed when winds approach 75 mph or whatever solid area wind load you design to.

Analyze for the screen condition then backcalculate the wind load at which any solid panels must be removed.

The provisions of the Florida Building Code that ron9876 noted applies only to the High Velocity Hurricane Zone (HVHZ), which is for Dade and Broward Counties.

Note also that the FBC has a minimum thickness requirement for any aluminum extrusion of 0.040", without regard to the analyzed loads.

Check with the Florida Department of Building Codes and Standards. At one time they produced a design guide document for screen enclosures. I looked for it online but didn't find it. I might have a copy in my library...I'll check and post if I have it.