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Re: Embedded Anchor Bolts In Compression[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: Re: Embedded Anchor Bolts In Compression
- From: "Mark Baker" <shake4bake(--nospam--at)earthlink.net>
- Date: Tue, 24 Oct 2000 22:41:26 -0700
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. > > > > > > > > > > > >
- RE: Embedded Anchor Bolts In Compression
- From: Sprague, Harold O.
- RE: Embedded Anchor Bolts In Compression
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