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RE: Anchor Bolts in Masonry

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Matthew:

Yes...it is a case of the masonry provisions of the WSD not the "Same" as
the Strength provisions.  This is what I was refering to as "harmonizing"
as this was the phrase that my contact on the committee used (see my
original post).  The standard "difference" in values between WSD and
Strength is more of a "conversion" issue rather than "harmonization"
issue (i.e. WSD is a "different language" than strength, so to really
compare you have to "convert" them).  At this point the WSD method is
"phyically" differnt than the Strength method, so that is why you are not
getting your standard 1.5 to 1.7 difference...the committee has not done
this "harmonizing" part yet.

HTH,

Scott
Adrian, MI


On Thu, 18 Nov 2004, Hood, Matthew O. wrote:

> Scott,
>
> I realize that the strength answer should be higher. But typically this
> would be on the order of 1.4-1.6 times higher. The results I'm getting
> indicate that the strength capacity for an anchor bolt in masonry is 4x
> that of the same bolt checked with ASD. Even when you "harmonize" the
> results this doesn't jive.
>
> If you compare apples to apples (maybe Granny smith to Fuji), the
> capacity of an anchor bolt in concrete checked using strength methods is
> much lower than that same bolt if it is in masonry. Now do the same
> comparison using ASD. The bolt in concrete (IBC section 1912) will have
> a capacity that is greater than that of the one in Masonry! I'm looking
> specifically at holdown bolts in foundation walls to make this
> comparison.
>
> Is this really just a case of the Masonry ASD code not having caught up
> with the Strength code?
>
> Matthew O. Hood, E.I.T.
> Plan Review Engineer
> Municipality of Anchorage
> 907-343-8451
>
> -----Original Message-----
> From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
> Sent: Thursday, November 18, 2004 1:25 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Anchor Bolts in Masonry
>
> Matthew:
>
> Now remember that you are comparing "apples and oranges".  The Strength
> Design "answer" _SHOULD_ be greater than the Working Stess Design
> "answer".  The point that Joe discovered is that the WSD equations have
> not been "harmonized" with the Strength Design equations.  This means
> that
> they are not really using the same "method" but in rather in different
> forms...in otherwords, after they have been harmonized they SHOULD
> produce
> the same answer, when you make the adjustment for Strength vs. Working
> Stress methods.  As a parallel, if you computer the "allowable" moment
> for
> a steel wide flange using ASD, that value should be less than the
> "allowable" moment for LRFD...but in the same token, the "applied" loads
> for ASD should be less than the LRFD "applied" loads (i.e. ASD loads are
> NOT factored).
>
> HTH,
>
> Scott
> Adrian, MI
>
>
>
> On Thu, 18 Nov 2004, Hood, Matthew O. wrote:
>
> > Scott and Joe,
> >
> > Thanks for your help. I was unable to locate the thread in the
> archives
> > but it sounds like that's just the way it is. It doesn't make sense to
> > me that the provisions for anchor bolts in concrete are so much more
> > conservative (using ACI 318-02 appendix D) than those for masonry. My
> > gut says it should be the other way around...
> >
> >
> > Matthew O. Hood, E.I.T.
> > Plan Review Engineer
> > Municipality of Anchorage
> > 907-343-8451
> >
> > -----Original Message-----
> > From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
> > Sent: Thursday, November 18, 2004 10:00 AM
> > To: seaint(--nospam--at)seaint.org
> > Subject: RE: Anchor Bolts in Masonry
> >
> > Joe (& Mathew):
> >
> > The quote was:
> >
> > "In my personal opinion, Eq. 2-4 is too conservative.  If augmented by
> > minimum cover requirements, Eq. 2-3 is enough.  That's the way the
> > strength
> > provisions are written, and I would use those for anchor design.  We
> > didn't
> > have time to fix this for the 2005 provisions.  We hope to finish
> > harmonizing the ASD and SD provisions for the 2008 document."
> >
> > HTH,
> >
> > Scott
> > Adrian, MI
> >
> >
> >
> > On Thu, 18 Nov 2004, Joe Grill wrote:
> >
> > > Mathew,
> > > I posted a question on this subject just a couple of weeks ago.  You
> > might
> > > check the archives for some of the replies.  Basically, yes you are
> > right.
> > > It gets even worse if you look at the separate definitions for Ap
> and
> > Apt.
> > > Scott Maxwell quoted an acquaintance of his who is on the committee
> > that
> > > agreed that the equation 2-4 is conservative, and if I remember
> > correctly
> > > 2-4 could be ignored if minimum cover requirements are met that 2-3
> > would be
> > > enough.  I won't try to remember the full quote word for word here,
> > but
> > > check the archives.  You are not the only one that has noticed this.
> > > J. Grill
> > >
> > > Joseph R. Grill, P.E. (Structural)
> > > Shephard - Wesnitzer, Inc.
> > > Civil Engineering and Surveying
> > > 1146 W. Hwy 89A Suite B
> > > Sedona, AZ  86340
> > > PHONE (928) 282-1061
> > > FAX (928) 282-2058
> > > jgrill(--nospam--at)swiaz.com
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Hood, Matthew O. [mailto:HoodMO(--nospam--at)ci.anchorage.ak.us]
> > > Sent: Wednesday, November 17, 2004 12:04 PM
> > > To: seaint(--nospam--at)seaint.org
> > > Subject: Anchor Bolts in Masonry
> > >
> > > I'm comparing the values for breakout of anchor bolts in tension
> using
> > > ASD and LRFD and I'm coming up with a pretty large discrepancy. I'm
> > > using ACI 530-02 which has
> > >
> > > Ba=0.5*Ap*(f'm)^0.5 for ASD
> > > and
> > > Ban=4*phi*Apt*(f'm)^0.5 for LRFD with phi = 0.5
> > >
> > > This would mean that the strength values are 4 times greater than
> the
> > > ASD values. Am I missing something? Does anyone know why the
> > difference
> > > is so large?
> > >
> > > Thanks for any input,
> > > Matt
> > >
> > > Matthew O. Hood, E.I.T.
> > > Plan Review Engineer
> > > Municipality of Anchorage
> > > 907-343-8451
> > >
> > >
> > >
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