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Re: aci 318-02 appendix d
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- 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 === __________________________________ Yahoo! Mail Mobile Take Yahoo! Mail with you! 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- From: Shapton & Partners
- Re: aci 318-02 appendix d
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