Fw: [TowerTalk] Concrete anchors

[Keith Dutson]

I agree that elevated guys should be extra strong to avoid movement during
high winds.  I chose 8 foot steel pipe with three feet in the concrete.  The
pipe is 4.5 inches OD with .25 inch wall.  The three poles were hot dip
galvanized before installation.  Each is set in 4 yards of concrete
(overkill) and the pipe is filled with concrete to increase bending
resistance.  I was able to observe the windward pole during a squall that
had 70 MPH gusts at the top of the tower.  There was no apparent flex at the
top.  The guys are pre-loaded at 600 PSI.  The tower is 150 feet of Rohn
45G.

Here are a few shots of one of the poles.  One of the snapshots shows an
apparent bend, but this is just an aberration of the camera lens.

http://www.dutson.net/transfer/HamRadio/TowerGuys/

Keith NM5G


-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Tower (K8RI)
Sent: Friday, September 17, 2004 6:51 PM
To: Bryan; towertalk at contesting.com
Subject: Re: Fw: [TowerTalk] Concrete anchors

Something to remember about elevated guy anchors. They really need to be
massive and strong. The elevated part needs to be heavy structural steel
capable of holding the guy tension and load without give.  I use 5" steel
pipe that is reinforced and it sets in a bit over 2 yards of concrete.  Were
I to do it again I'd use at least 3 yards and my tower is only 100 feet with
the anchors out 80% or 80 feet.

I'm a bit short on ambition to run the calcs for stress and anchor points on
the tower. Besides I haven't had to do any of that math since I graduated
from college.

However with the anchors in close and of unequal lengths I'd expect to see
some twisting moment added in addition to the side load with wind.

Roger Halstead (K8RI, EN73 & ARRL Life Member) N833R, World's Oldest
Debonair (S# CD-2) www.rogerhalstead.com
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