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Re: Embedded Anchor Bolts In Compression

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Bill:

You might contact Hilti.  I seem to recall a detail in an article in one
of the more recent Structural Engineer magazines similar to what you
describe.  If I recall correctly, the article was written by someone from
Hilti.  If my memory is correct, then they might have some research that
resulted in some design methods.  I will try to remember to look up that
article tomorrow at work.

Scott


On Mon, 23 Oct 2000, Bill Polhemus wrote:

> 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.
> 
>