All:
J-bolts are an archaic anchor rod concept. The use of straight anchor rods has
be going on for over 20 years. The design codes (ACI) and building codes (IBC)
have allowed straight anchor rods for quite awhile now. Note that the correct
terminology is anchor rod not anchor bolt. The change over came as it was
notice that the crook of the J-bolt style would actually crush the concrete
locally and could cause premature failure.
Anchor rods are be design to develop the full tensile strength of the anchor
before the surrounding concrete fails, typically a cone type pull out failure.
I have designed, seen and used both welded nuts, double nuts, nut and washer at
the base of the anchor rod. All that is really needed is a nut.
Drilled-in chemical and mechanical anchor systems are manufactured to behave
the same, i.e., fail the anchor not the concrete around it. For those who crave
or need more information, google "Hilti" and read about "post-installed"
chemical and mechanical anchors.
Installed per manufacturer's criteria they will develop their designated
strength and most are ICBO approved.
Regards
Lonberg Design Group, Ltd.
H. Lonberg, P.E.,S.E. / KR7X
President
-------------- Original message --------------
From: "Dan Kovatch" <w8car@buckeye-express.com>
> My US tower anchor bolts which were installed about a year ago had two nots
> locked against each other threaded onto the bottom of the straight rod and
> the thread end was 'peaned' over. No welding in effect.
>
> FWIW
> Dan W8CAR
>
> ----- Original Message -----
> From: "darrel"
> To:
> Cc:
> Sent: Wednesday, February 01, 2006 12:37 PM
> Subject: Re: [TowerTalk] LOOKING FOR A USED CRANK UP
> SELFSUPPORTINGTUBULARTOWER
>
>
> > It also shows straight bolts on their foundation drawings.
> >
> > But they DO have a nut and washer welded? on the end to keep it embedded.
> >
> > I have no idea whether epoxying a straight rod into a drilled hole has the
> > same pullout resistance as a J-bolt or nut and washer (it's not enough
> > that
> > the epoxy is stronger than concrete - it's adhesion to the bolt is
> > critical -
> > rebar is bumpy so that the concrete gets a good grip), but a couple of
> > these
> > bolts do take the entire uplift force on the upwind side with a 70 foot
> > long
> > lever arm (rough estimate 20,000 pounds per bolt, a good fraction of it's
> > breaking strength).
> > My guess (but I have no structural qualifications), is that the J bolt
> > (or
> > washered straight bolt) snaps long before you could pulverize enough
> > concrete
> > to pull it out.
> > As to the change - I'd guess the found the price of J bolts higher than
> > the
> > current choice and either way pullout wasn't the first failure.
> > Darrel AK6I
> >
> > --- "Richard M. Gillingham" wrote:
> >> They're shipping straight bolts now. I just received mine a couple of
> >> weeks
> >> ago.
> >>
> >> 73
> >> Gil, W1RG
> >> ----- Original Message -----
> >> From: "Jim McDonald"
> >> To:
> >> Sent: Wednesday, February 01, 2006 11:31 AM
> >> Subject: Re: [TowerTalk] LOOKING FOR A USED CRANK UP SELF
> >> SUPPORTINGTUBULARTOWER
> >>
> >>
> >> > Doesn't US Tower require J-bolts, rather than straight bolts?
> >> >
> >> >
> >> > Jim N7US
> >> >
> >
> > _______________________________________________
> >
> >
> >
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> >
> >
> >
> > __________________________________________________________
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> > 1:30:53 PM ET - 2/1/2006
>
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