[TowerTalk] Adjustments to Tower Base Pier J-Bolts
jim.thom at telus.net
Mon Jul 24 12:49:40 EDT 2017
Date: Mon, 24 Jul 2017 08:47:01 -0700
From: "Richard (Rick) Karlquist" <richard at karlquist.com>
To: Jim Thomson <jim.thom at telus.net>, towertalk at contesting.com
Subject: Re: [TowerTalk] Adjustments to Tower Base Pier J-Bolts
On 7/24/2017 7:20 AM, Jim Thomson wrote:
> ## Those J bolts he is using, are massive... at 1.875 inchs across, with
> 12 inches sticking above the concrete. Paul did not say how many are used on
> each corner, probably at least 4. They are not gonna budge, whether a sledge hammer, or
> hydruaulic jack used...or trying to crank up on the lower nuts, trying to raise the template...
> and then trying to bend the J bolts, not gonna happen.
Please explain why the J bolt fabricator can bend the end of the
J bolts into the shape of a "J", but OTOH, the installer cannot put
a very slight bend into them. With 12 inches above the concrete,
there is something like 12:1 leverage. Even with 100,000 PSI J
bolts, a 20 ton jack should be able to easily exceed the yield
strength. I know my jack simultaneously bent 4 one inch braces
without any trouble. I also had about 12 inches of leverage.
## My understanding is they are formed into the.. J at the bottom
of the rod... while still in the semi molten state....which is well before
the threads on top are cut....which is well before the heat treating process.
## portland bolt does not offer J bolt anchor rods these days.
J bolts were originally used to increase the uplift capacity of the
anchor rod assy. J bolts for the most part, are out of vogue these days,
and banned in most construction.
They still offer L rods, for some applications, which have a 90 deg bend
at the base of the rod... for several inches, then another 90 deg bend
upwards, but only for an inch on that last upwards bend.
## They suggest, to increase uplift capacity, to use a steel plate, at the
base of the threaded rod. To do that of course requires that the bottom of the
anchor rod be threaded. Portland bolt sells and fabricates the mating plates.
## On my HDX-689, 4 x 1.125 anchor rods are used on each corner. The newer
version HDX-689 uses 4 x 1.250 anchor rods. I had the local metal fabricator
make 3 x identical 9 inch x 9 inch x .375 thick plates, with the punched 4 x 1.25 holes
with the correct 5 inch c to c spacings. A 9 inch square plate in that application will increase the
uplift capacity by a huge amount. And a better method than USTs method of using washers,
welded to a non threaded anchor rod.
The plate concept also offers other advantages. None of the 4 x rods can rotate on their axis,
even if concrete has not set. Also a lot less likely to bend if a single template was used.
You would have to bend all 4 of em, or none at all.
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