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Re: aci 318-02 appendix d

[Subject Prev][Subject Next][Thread Prev][Thread Next] D-21. Avo is a function of c1 and c2 where c2 is equal to 1.5 c1. Say c1 = 5' and c2 = 7.5'. Forget about h for a minute, Avo is equal to 3c1x1.5c1 and Av would be the same yielding a Av/Avo ratio of 1.0. Now increase c1 to 7.5'. Avo =2c1x1.5c1 but now Avo is still = 3c1x1.5c1 and the Av/Avo ratio is now less than 1.

Padmanabhan Rajendran wrote:

I did not say that psi6 has anything to do with
thickness.

Which formula implies capacity reduction with
increasing c1?

Rajendran
--- "Lutz, James" <James.Lutz(--nospam--at)earthtech.com> wrote:

I didn't say "h" wasn't the thickness of the
concrete, all I was saying is
that there is something odd about the way capacity
is reduced when you
increase c1, when in fact it should be the other way
around. Psi6 is an
adjustment factor for a corner condition and has
nothing to do with
adjustment for thickness.

-----Original Message-----
From: Padmanabhan Rajendran
[mailto:rakamaka(--nospam--at)yahoo.com]
Sent: Thursday, May 19, 2005 1:19 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: aci 318-02 appendix d


'h' is not the embedment depth. It is the thickness
of
concrete. Edge effect is embedded in psi6. If
c2>1.5c1
then psi6=1. psi5 accounts for the the eccentricity
of
bolt CG in relation to the CG of the foundation
footprint. If h >=1.5c1 and c2>=1.5c1 Vb is
proportional to (c1)^1.5. If c1 is large, Vb will be
large too, meaning that the breakout strength in
shear
will not control design.

I don't see any confusion in using the referenced
section.

Rajendran


--- "Lutz, James" <James.Lutz(--nospam--at)earthtech.com> wrote:

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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