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ACI APP. D

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John:

Regarding bolt pullout values, we have had the same discussions in our
office regarding the seemingly negative effect of increased embedment in
certain situations.

If you closely look at the formula, (D-5), especially Ano, you can see why.
If you have a pedestal, the An value is controlled by edge distance. In a
situation like yours, in a pedestal, the edge distance is quickly limited no
matter how much you increase your embed (as edge distance is a function of
embed). So as your An term is held constant, and you increase your embed,
and the Ano term increases, then the An/Ano term decreases. Thus your
pullout decreases with increased embed. Obviously this is an unfair penalty.
This is addressed in the COMMENTARY RD.5.2.3, where they constrain hef.

What we do here is when we have a situation where edge distance controls, we
do iterative solutions to achieve the maximum Ncbg value, even if the embed
is like 5". We use that value for design, but we increase the embed to loop
around reinforcement or to give us a comfortable embed. This way we know we
have the design pullout correct value, which is conservative, and we all
know very well increased embed will not actually DECREASE the allowable
pullout, so this is a comfortable method.

I hope this was fairly clear and I hope we have interpreted this the correct
way.

Andrew Kester, EI
Longwood, FL



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