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RE: aci 318-02 appendix d

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Jack, this problem has been driving me nuts since you called me up to talk
about it this morning.

We are talking about the breakout strength of an anchor in shear. This is
taken as a basic value Vb times a series of reduction factors, Av/Avo, psi6,
and psi7 (leave psi5 out of the discussion for now, since it's an adjuster
for group action). Psi7 is just a constant, so it is not relevant to the
discussion either, which centers around the equations that include edge
distances c1 and c2 in them.

The Vb value is proportional to c1^1.5, with no apparent limit other than
the fact that at some point Vs will control capacity.

The Av/Avo value cannot exceed 1.0 and is intended to adjust for the ratio
of the actual thickness of the concrete to the maximum of 1.5c1, and for the
actual width of the breakout surface versus the maximum of 3c1. Another way
to express this is (h/1.5c1)*(width/3c1). As c1 gets bigger and bigger,
Av/Avo reduces to zero pretty quickly irrespective of the other variables,
which seems a little counterintuitive to me. You would think that you should
only get penalized if c1 gets smaller, not the other way around.   

Something about this methodology does not add up. 




-----Original Message-----
From: Shapton & Partners [mailto:shapton(--nospam--at)nwlink.com]
Sent: Wednesday, May 18, 2005 1:13 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: aci 318-02 appendix d


David, a little while ago I spoke with Basile Rabbat on this issue.  
Basically, if c1 = infinity, how can c2 = infinity x 1.5 (which would 
yield Av/Avo <1)?  This is not the intent.  B. Rabbat recognized the 
issue and thought clarification would be coming.  It is my understanding 
that Hilti has figured this out.  I believe the solution relates to a 
concrete thickness of 1.5 x the embedment depth as this is thier 
standard with Re-500 anchors. Looking at their tables, you can see that 
if c1and , c2 are greater than 1.5 x the embedment, Av does not enter 
into the pixcture. Sorry for the disorganized response, I am just going 
out to a meeting, saw your subject, and wanted to send something that 
might initiate further discussion.

Jack Shapton

David Adie wrote:

> shear force parallel to an edge
>
> D.6.2.1 - footnote c - recognizes the fact that c1 in psi 6 doesn't 
> make sense but equation D-21 includes Vb which still has c1 embedded 
> in it.  what value to use when c1 = infinity?
>
> tia
> da
>

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