I am supervising the installation of a 60 foot Rohn 25 tower. (This
means finding the people with knowledge and muscle.)
It will be placed next to a 50 foot building with concrete walls, a flat
roof, and a 5 foot parapet (wall) around the roof. (Top of the parapet
is 50 feet above the ground.)
It will have one wall bracket for each section of Rohn 25 along the
wall. I know this is probably overkill, but that is what they want, and
they have the money for it.
The proposed plan is to bolt a tilt-over base to the large 6" concrete
driveway/parking lot by using butterfly expanders.
Then they want to assemble it on the ground, and tie a couple of ropes
to it at 50 ft and have 6-8 people pull it up from the flat roof. (With
the same number on the ground to help get it started.)
First question is this a good plan?
Do we need to also pull from the middle (25 feet) so there is not a
bow?
Second part. The ground is all 6" concrete driveway. They are worried
that we can not just drill a 5/8" or 3/4" hole through the concrete and
put ground rods in because we have to have a certain amount of air gap
between the ground rod and the concrete, or the concrete will explode
when lightning hits.
That does not sound right to me, because the even though concrete is
somewhat conductive, the ground rod is going 10 feet into the earth. And
if I have three ground rods the lightning will be spread into the ground
and not as much through the concrete and the unknown places of rebar in
the concrete. And we already have the tilt over plate bolted to the
concrete driveway. So it is not like there is a point connection to the
concrete.
Do we really need an large air gap between the ground rods and the
concrete driveway? If so how much?
Kip
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