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Re: aci 318-02 appendix d

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• To: seaint(--nospam--at)seaint.org
• Subject: Re: aci 318-02 appendix d
• From: Padmanabhan Rajendran <rakamaka(--nospam--at)yahoo.com>
• Date: Thu, 19 May 2005 18:41:49 -0700 (PDT)
• Comment: DomainKeys? See http://antispam.yahoo.com/domainkeys
```In the second case, Avo=(c2+1.5c1)*1.5c1, because
c2<1.5c1. A reduction in Av/Av0 is to be expected
because a smaller edge distance (c2<1.5c1) prevents
the full development of the shear failure edge.
However, the increased c1 yields a higher value for
Vb.

Rewriting the equation for Vb as: Vb=constant*c1^1.5,
the two cases yield the following result

case 1: Vb=11.18*Constant
case 2: Vb=24.65*Constant

This shows that the shear capacity in this mode of
failure does not decrease with increasing c1.

Rajendran

--- Shapton & Partners <shapton(--nospam--at)nwlink.com> wrote:

> 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
>
=== message truncated ===

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