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Re: Embedded Anchor Bolts In Compression

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Just because it is not in fashion anymore to design anchor bolt embedment
based upon bond.......

Look back at mid 60's vintage ACI manual for bond strengths at various f'c
and bolt diameters. Let me know if you can't find it.

Mark

----- Original Message -----
From: Bill Polhemus <bpolhem(--nospam--at)swbell.net>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, October 23, 2000 3:26 PM
Subject: Embedded Anchor Bolts In Compression


> I know we talked a little about this a few months back, but now that I
have a
> little more knowledge (a "little knowledge" being, of course, a dangerous
thing)
> about the topic, I'd like to recast the question I asked before.
>
> In some instances there are advantages to NOT grouting structural column
base
> plates. For example, our stated DOT does not allow grouting of column base
> plates for overhead traffic sign structures, which are typically hollow
sections
> and have cables or conduit running up into them from the bottom (the base
plates
> have concentric openings to allow this). They are afraid that condensed
moisture
> will build up inside the columns and cause accelerated corrosion.
>
> Thus, no grout under the base plates, and the compression AND tension
forces are
> carried by the anchor bolts, the plate resting on the levelling nuts.
>
> An embedded anchor bolt in compression would tranfer the column forces
into the
> concrete pedestal by bearing on the nut at the bottom of the bolt. But
these
> forces are bound to be large, and using the ACI code-calculated bearing
strength
> of the concrete under the nut (ACI 318-10.17.1) is not going to be
sufficient
> for such a force.
>
> Does anyone have any experience with this? What did you use to determine
> adequacy?
>
> I seem to recall that research into anchor bolt failure mechanism showed
that,
> because of localized confinement, the bearing at the nut allowed was
typically
> on the order of many times the ACI 318 code calculation, when the bolt is
in
> tension. Not sure if the same would apply here.
>
> Look forward to your input.
>
>