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Re: Flexural reinforcement "Ad Libitum"

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The older versions of the code did not have this exemption. I was trained in
school on ACI-318-77 when the seismic provisions were in Appendix A. I was
taught that this omission is intentional, as ductile frames cannot be made
from plain concrete, even if the member is 1/3 stronger.

I think the exemptional finally crept in the 95 code. I distinctly remember
designing a building in early 90's on ACI in zone 4 (I usually design in
zones 1 and 2) and I was made to provide 200/fy in oversized beams. Maybe
the checker was also an old guy.

Any ACI guru on the list?

Masroor



----- Original Message -----
From: "Scott Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
To: <seaint(--nospam--at)seaint.org>
Sent: Friday, May 19, 2006 10:20 PM
Subject: Re: Flexural reinforcement "Ad Libitum"


> Likely because of the maximum reinforcement ratio (the 0.025 value) plus
> the requirement of at least two continuity bars top and bottom.  Both at
> "additions" to the requirements of 10.5.3 that are there cause of the
> seismic "situation".
>
> Regards,
>
> Scott
> Adrian, MI
>
>
> On Fri, 19 May 2006, Syed A Masroor wrote:
>
> > This is what I had in mind when I wrote this. Somehow, I had always
thought
> > it to be this way but when I looked up 21.3.2.1, the 10.5.3 exception
was
> > there. So apologies.
> >
> >
> > Any idea why was this limit put in this section again?
> >
> > Masroor
> >
> > ----- Original Message -----
> > From: "Scott Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
> > To: <seaint(--nospam--at)seaint.org>
> > Sent: Friday, May 19, 2006 2:01 PM
> > Subject: Re: Flexural reinforcement "Ad Libitum"
> >
> >
> > If it is the section that I think he is thinking about then it would be
> > section 21.3.2.1 of ACI 318-05, which is basically the same as section
> > 1921.3.2.1 of the 1997 UBC.  If that is what he is thinking about, then
I
> > am not sure why he thinks that the 1/3 provision does not apply to high
> > seismic zones as that section clearly states that section 10.5.3 (or
> > 1910.5.3 of the 1997 UBC), which is the 1/3 provision section, still
> > applies.  Not to mention that that section is only for special concrete
> > moment frames, which is likely NOT what Joe was dealing with (an
> > assumption on my part).
> >
> > Regards,
> >
> > Scott
> > Adrian, MI
> >
> >
> > On Fri, 19 May 2006 Rhkratzse(--nospam--at)aol.com wrote:
> >
> > > Could you save me (us?) some time and give us the code reference?
> > Thanks.
> > > Ralph
> > >
> > > In a message dated 5/18/06 9:35:23 PM, masroor(--nospam--at)eaworld.com writes:
> > > > This is not allowed if you are in seismic zones 3 or 4 as per ACI
> > chapter
> > > > 21. Were you? Otherwise, the code is quite clear on this issue.
> > > >
> > > > Masroor
> > > >
> > > > ----- Original Message -----
> > > > From: "Jesus Gomez" <jgomez(--nospam--at)schnabel-eng.com>
> > > > To: <seaint(--nospam--at)seaint.org>
> > > > Sent: Friday, May 19, 2006 2:47 AM
> > > > Subject: RE: Flexural reinforcement "Ad Libitum"
> > > >
> > > >
> > > > Thank you Joe. That is exactly what I have always used. My submittal
got
> > > > rejected by a reviewer on this basis. Go figure!
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Joe Grill [mailto:jgrill(--nospam--at)swiaz.com]
> > > > Sent: Thursday, May 18, 2006 5:41 PM
> > > > To: seaint(--nospam--at)seaint.org
> > > > Subject: RE: Flexural reinforcement "Ad Libitum"
> > > >
> > > > Doesn't the code allow a 1.33 factor over what steel is required by
> > > > analysis in lieu of the minimum percentage steel requirements?
> > > > Joe
> > > >
> > > > Joseph R. Grill, P.E. (Structural)
> > > > Shephard - Wesnitzer, Inc.
> > > > Civil Engineering and Surveying
> > > > P.O. Box 3924
> > > > Sedona, AZ 86340
> > > > PHONE (928) 282-1061
> > > > FAX (928) 282-2058
> > > > jgrill(--nospam--at)swiaz.com
> > > >
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Jesus Gomez [mailto:jgomez(--nospam--at)schnabel-eng.com]
> > > > Sent: Thursday, May 18, 2006 2:36 PM
> > > > To: seaint(--nospam--at)seaint.org
> > > > Subject: Flexural reinforcement "Ad Libitum"
> > > >
> > > > I have a "philosophical" question of important implication in a
current
> > > > project.
> > > >
> > > > I will not use real quantities. Also, I will not describe the
problem
> > > > entirely and focus on a particular aspect of it. Say a beam of given
> > > > dimensions requires minimum reinforcement to handle a given bending
> > > > moment. Say that the beam is 100 in (d) by 10 in (b) and that the
> > > > minimum reinforcement is thus 3.33 in2.
> > > >
> > > > For constructability, the contractor would need (not prefer) to make
the
> > > > beam with d=150 in instead of 100 in
> > > >
> > > > Do I need to provide now 4.95 in2 instead of 3.33 in2 ?
> > > >
> > > > The typical answer is "yes". However, how can the cracks become
larger
> > > > for the same moment, same steel, and a larger section? Also, if I
keep
> > > > increasing the size of the section, I would need unrealistically
large
> > > > amounts of reinforcement.
> > > >
> > > > Just for information, I am retrofitting an existing pile cap with
> > > > additional piles (micropiles). I am providing a new "pile cap" on
each
> > > > side of the existing pile cap connected by dowels, which would work
as
> > > > flexural and shear reinforcement at the interface. The dimensions of
the
> > > > added pile cap are pretty much defined by external factors and I
only
> > > > have a limited space available for dowels.
> > > >
> > > > Thank you
> > > >
> > > >
> > > >
> > > >
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