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Re: Embedded Anchor Bolts In Compression

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Hi Harold,

I do not deny the validity of cone failure and its application to designing
embedded anchors. But the fact remains that such an animal as bond does
exist. Yes, scale on a bolt, oil, rust, zinc, roughness (or lack there of)
etc. will impact the bond performance of an embedded bolt. And I am sure
those who came before us who relied upon bond were competent engineers aware
of this fact who specified "clean and free of deleterious material".

When faced with a problem, such as that in Bill's initial post, where the
numbers aren't working, I step out of my blissful little engineers world and
ask myself "what else could be going on here that I am not accounting for".
This point of view was the spirit in which my post was sent and I hope that
is the way it was received.

How green, by the way, was the concrete in which the bolt pulled out :0)

Mark

----- Original Message -----
From: Sprague, Harold O. <SpragueHO(--nospam--at)bv.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, October 24, 2000 9:42 AM
Subject: RE: Embedded Anchor Bolts In Compression


> Mark,
>
> The reason that bond for plain bars went out of fashion was due to the
> variability, and the potential for catastrophic failures.  The original
bond
> strengths were predicated on very limited testing of hot rolled mild steel
> which had a lot of porosity at the surface.  Cold rolled shapes did not
have
> this surface porosity.  More modern rolling mills had much less surface
> irregularities than older mills even for mild steel.  Bond strength
testing
> to plain steel could not be validated.
>
> Personally I saw an iron worker back out an unheaded anchor bolt that was
> embedded 4 feet into a drilled shaft.  It backed out just due to the
tension
> from tightening with a plain spud wrench.  According to ACI 318-63, the
> embedment was enough to fully develop the bolt.  ACI 318-63 was the last
318
> that allowed for bond to plain steel.
>
> Regards,
> Harold Sprague
>
>
> > -----Original Message-----
> > From: Mark Baker [SMTP:shake4bake(--nospam--at)earthlink.net]
> > Sent: Monday, October 23, 2000 9:41 PM
> > To: seaint(--nospam--at)seaint.org
> > Subject: Re: Embedded Anchor Bolts In Compression
> >
> > 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.
> > >
> > >
> >
> >
>
>