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# ground anchors....

#1
02-10-09, 07:32 PM
Member
Join Date: Jan 2008
Posts: 35
ground anchors....

anyone familiar with these duckbill ground anchors that you drive into the ground then connect via the cable to the structure you need to anchor? how effective are they? i've got a 12x20' building i need to anchor. will they work? thanks...

#2
02-10-09, 08:16 PM
Member
Join Date: Apr 2008
Location: Oklahoma
Posts: 1,602
if you get them in at least 24in they will work quite well, although i favor the screw in anchors. best bet is to figure the force from avarage winds in your area and divide by the holding force of the anchors to come up with the number of anchors needed.

life begins when the kids leave home and the dog dies

#3
02-11-09, 08:39 AM
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Join Date: Jan 2008
Posts: 35
thanks. second question, do i need to buy the driving rod they sell for the anchors (\$50 or so) or can i just get a length of rebar and use that?
and how do i figure the force from average wind?

#4
02-11-09, 09:16 AM
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 19,281
The wind pressure, q = .00256V^2 (V is in mph)
Got this from another board...not sure if its correct...but it gives you the force per SF.

So...say you have a 50mph wind against a 20' x 8' flat wall (160SF)

.00256 x (50 x 50) x 160

.00256 x 2500 x 160 = 1024 lbs of force against the structure.

Can't guarantee this is correct...Its not taking into account roofs or quartering winds or anything else.

#5
02-11-09, 12:57 PM
Member
Join Date: Jan 2008
Posts: 35
thanks gunguy.
another question. if an anchor is rated for 1100lbs and i have say 6 of them around the building, does this mean i have 6600lbs protection? or maybe 3300 since it would be 3 on each side of the building?

#6
02-11-09, 01:12 PM
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Join Date: Dec 2007
Location: USA
Posts: 19,281
I would say you have 3300...since the wind really only can blow one way at a time.
As I said..I'm sure theres more to the calculations than that.

I would check with your local Codes office and see what they would require for your structure.