Hello- I have some questions regarding the effects seen on anchor rods when
installing first level of guys on a 130' 45G tower: The tower is
installed per Rohn 130 MPH specs, using same spacing, dimensions and angle of
anchor rod (38 deg). The anchor rod is made identical to the Rohn GAC5655TOP
being 10' long, 1.25" high strength rod, 1/2" 50 KSI plate at top end of rod
but with only 3 drilled 13/16" holes for turnbuckles, hole spacing same as Rohn
(5655 anchor has 5 turnbuckle holes) and concreted in a concrete anchor built
per Rohn AB3 dimensions. I have the tower free-standing at 41' right
now using a 5' concrete base section. A guy bracket was installed at 35' per
Rohn spec and I attached the guy/turnbuckle to bottom hole in anchor rod plate
and tensioned to around 600#. I am seeing the anchor rods bend downward to an
angle of around 30 deg as I increase the tension on guy wire. It appears the
rods have a very slight, just barely perceptible bow in them, possibly from the
wrenching action of the pull being from several inches below the rod center (as
plates are welded to rod and not pivoting). I left the "slots" cut
in ground (where anchor rod angles upward from top of concrete to surface of
ground) unfilled as I wanted to be able to observe the effects on them and to
install protective sheaths on them, where they exit the ground, when tower is
finished plus to backfill these with clean sand. The rods were tarred and
wrapped for corrosion protection. I backed the turnbuckles off to a
much less guy wire tension in order to reduce the downward pressure on anchor
rods and to allow me to install cribbing under the turnbuckle plates to restore
my anchor rod angle back to 38 deg. This is the first tower that I
have installed with fixed turnbuckle plates welded on an anchor rod. It seems
that all of the ones in past had the pivoting turnbuckle plates and I did not
notice these effects as the plates pivoted way upward with only bottom guy wire
attached. So my questions are --1. Has anyone else observed these
things in installing a similar tower? Possibly if I had backfilled the anchor
rods these effects would not have been as easy to detect.2. Would anyone have
an opinion regarding using strong cribbing under the turnbuckle plates in order
to maintain original installed rod angle of 38 deg. as I restore tension to
around 600# on bottom set of guy wires? I imaging that when I get the
second level of guys installed, of which turnbuckle holes are centered on ends
of anchor rods themselves, the rods will be pulled upward, closer to the
installed angle of 38 deg, and with installation of top set of guys all will
balance out for rod angle of 38 deg. My first experience with fixed
turnbuckle plates on anchor rods. Thanks for any comments or advice.Byron W5FH
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