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
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.
--- "Richard M. Gillingham" <email@example.com> wrote:
> They're shipping straight bolts now. I just received mine a couple of
> Gil, W1RG
> ----- Original Message -----
> From: "Jim McDonald" <firstname.lastname@example.org>
> To: <email@example.com>
> Sent: Wednesday, February 01, 2006 11:31 AM
> Subject: Re: [TowerTalk] LOOKING FOR A USED CRANK UP SELF
> > Doesn't US Tower require J-bolts, rather than straight bolts?
> > Jim N7US
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