[TowerTalk] Tower base "challenge"

[Pete Smith N4ZR]

If anyone wants to be serious about this, the formula for the pull-out 
resistance of lag screws is on page 8-10 of this document 
<http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_08.pdf>. 
Compare whatever numbers you get to the ultimate strength of 3/16 EHS 
guy wire, factor in an appropriate safety factor, and I bet you'll 
abandon the idea.  We have an old sugar maple that has 7 cables holding 
its canopy together, and the cable anchors use long through bolts, big 
nuts, and bigger washers on the back side of each.  I certainly would 
not climb anything guyed that way that has been subjected to severe stress.

73, Pete N4ZR
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On 3/12/2014 4:45 PM, Steve Oksala wrote:
> I have a problem, and hopefully the experts on this forum will be able to
> help.
>
> My tower is 50 feet of Rohn 25, with a Force  12 C-3 on top. The tower has
> been up for around 30 years. It has been guyed at 25 and 45 feet with
> standard steel cable. The guys were anchored as follows: Guys A were into a
> pine tree at about six feet; some years ago the tree died, and the stump was
> left to hold the anchors. Guys B were also into a pine tree at about six
> feet, and like Guy A the tree died and the stump was left with the anchors.
> Guys C were about six feet into a large maple tree.
>
> At the end of fall, I disconnect the lower guys as I planned to replace
> them. However time was limited, and the tower was guyed only at the 45 foot
> level. Earlier this winter, we in the Philly area had a severe ice storm.
> The result was that - I think - that the ice load on the guys was very high.
> The result was that the screw-in for Guy A pulled completely out of the
> stump; the stump which contained Guy B pulled completely out of the ground,
> with the screw-in still attached; and Guy C was still connected. However the
> tower now has a distinct tilt. Just recently I was able to examine it, and
> the cement base in which the tower was set has actually tipped somewhat, so
> one side is about an inch up above the ground and the other side is a little
> bit below. The base is tilted toward the maple tree where Guy C remained
> intact, and I can only assume that the weight of the ice on the guy wire
> pulled it into this new position. (The antenna held up fine.)
>
> The question I have now is what to do next. I do need to climb the tower to
> replace the rotor cable (unrelated issue) and install an inverted V around
> 40 feet. But I don't know if I should simple reguy it as is, or fix it - and
> if I fix it, what does that mean? Do I need to dig up all around the base,
> straighten it out (by pulling on the top guy wire, which is still attached
> to the tower), and then filling in around it with new concrete?  Demolish
> all that concrete and replace (a huge job, I would think)? What other
> options exist? I should also note that when I put it up I did not use any
> rebar, just the hole and concrete I mixed and poured.
>
> Any advice would be appreciated. If there is a consensus that this should be
> left to an expert (I am 70 years old and used my brain for a living; no
> construction skills)?  If so, any recommendations?
>
> Thanks in advance for your expertise.
>
>   
>
> Steve Oksala
>
> NI3P
>
> Ni3p at comcast.net
>
>   
>
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