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Re: Anchoring to Concrete

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Michael,
 
Thanks for your reply. But let me pose my standpoint not matching with yours.
I see, there are several concerns arising from this Appendix D, as I have read
from other mails, like some one from Nels Roselund.
First of all, it is said that most of the information is based upon tests with an upper
range of some 25 in. for the effective anchor embedment depth. For much larger
anchors, ( as they are in my case ) how reasonable is it, to extrapolate these
code provisions ? Which would be the larger anchor size, where this extrapolation
could be safely done ?
The additional requirements for design, when seismic loads are included ( as they are
in my case ), are correctly calling for a ductile steel element, for the anchors themselves.
But, AFAIK, the failure in tension of concrete, which is the basis of the Nb capacity, is 
by no means a ductile way of failure. Therefore, it is much more reasonable ( for seismic
loadings ) to hold down all of the forces, from the theoretical rupture cone, through well
proportioned reinforcing bars ( ductile steel ), than relying in the concrete breakout strength.
I also, would like opinions of our seismic and/or ACI related listers, like Bill Sherman.
 
Best Regards,
 
Raul Labbé  S.E.
M. ASCE.

 
 
 
 
    
----- Original Message -----
From: "Michael Bryson" <mbryson(--nospam--at)NYASE.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Saturday, October 16, 2004 7:26 PM
Subject: RE: Anchoring to Concrete

> I think the intent of the code here is that the addition of reinforcement is only meant to control cracking, not to increase the capacity of the anchorage in tension. Once a crack forms, the stresses in the concrete (hoop stresses) change and the anchorage capacity is reduced.
>
> Now having said that, if more reinforcing means you have smaller cracks, and since there is a correlation between crack size and anchor capacity, then technically additional reinforcing does increase the capacity. But I don't think the code allows for this.
>
> -----Original Message-----
> From: Rlabbe [mailto:rlabbe(--nospam--at)cadeidepe.cl]
> Sent: Saturday, October 16, 2004 6:49 AM
> To:
seaint(--nospam--at)seaint.org
> Subject: Anchoring to Concrete
>
> List,
>
> I will require some help to see if we are correctly interpreting the codes
> in the
> referenced matter.
> ACI 318-02, ( App. D ) is determinig the achoring capacities in concrete,
> based
> on the concrete breakout strenght in tension ( failure cone of the concrete
> mass ).
> It also allows to increase this capacity, when there is no cracking in the
> anchoring
> region.
> The question is, since this capacity is based only in the concrete failure,
> can it be
> increased with the addition of adequate reinforcement ? i.e. enough rebar,
> and properly
> placed, in the ( would be ) failure cone mass, as to take the full pull-out
> load.
> Appreciate your opinions.
>
> Best Regards,
>
> Raul Labbé  S.E.
> M. ASCE.
>
>
>
>
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