Horizontal wire grid - wind load 1

[vmirat]

I'm designing a structure to support WWR 4x4-W4xW4 wire grid over a 42'x 85' mechanical yard which has 15' tall solid screen walls on three sides and the building on the fourth side (85-foot dimension). The steel structure to support the wire grid includes moment frames for both directions. I'm trying to determine the wind loading on the moment frames.

Since the wire grid is level with the top of the vertical screen walls, my first thought was that the wire grid would not have a wind component since it's open. However, because it is open, and the fact that wind doesn't really travel perfectly horizontal, I'm inclined to add something for wind drag on the wire grid. ASCE 7 doesn't address this situation, so I'm looking for some recommendations.

My first idea was to assume that the wind vector was at a 10 degree angle from the horizontal and then figure out the projected area of the grid.

As a side note, you're probably wondering why I'm doing moment frames. The existing screen walls are only 10 feet high right now. The wire grid has to be at a 15-foot height to avoid the equipment in the yard, so I'm having to add screen panels to the existing, which means the existing columns of the screen walls are no longer sufficient and I have to get creative to support the additional wind load without replacing all of the existing columns. Plus, this mech yard is chocked full of equipment, so column placement is very limited, and I can't support anything off of the building.

 

[dhengr]

Vmirat:
Wow… those must be big mosquitos you are trying to keep out.

 

[JAE]

I think your concept of a slight angle to the mesh is really the only rational thing I can come up with and your best bet to get some level of wind force derived.

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[SAIL3]

for uplift on the horiz screen.....I would probably assume 30deg angle because of the material and equipment in the yard that may alter the wind direction vector and to account for any future change in the parked equipment and this is just an engineering judgement call...the boundary layer on the earth's surface can range from 15 to 30 ft, if I remember correctly, but do not recall the affect this has on the wind direction vector in the boundary layer..
for horiz drag on the horiz screen I would assume 10deg....I have never seen any drag coefficient for this case and it should be interesting to see what the OP digs up on it....

 

[SAIL3]

on further thought, if I use the 30deg angle, maybe I could assume the wind resultant force is also @ 30deg and then break that force up into horiz and vert components...but not real certain that the resultant wind force would also be @ 30deg....maybe some others can weigh in on this.....

 

[racookpe1978]

But what is the live load, and wind load when kudzu, tomatoes, or zuchinni's begin growing across the opening?

 

[vmirat]

I decided to go with TIA-222. It has provisions for guy wires. Each wire of the grid will experience a horizontal wind load.