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RE: Foundation Min. reinforcement

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Ed,

The 1/3 more steel than required by analysis exception DOES apply to beams
in high seismic zones in the ACI code.  And since the the UBC basically
adopts and reprints the ACI provisions (with some modifications), the same
exception should be permitted for high seismic areas in the UBC code.  I
say should because in my neck of the woods we don't use the UBC so I can
not verify if that is one of the provisions that the UBC may have modified
when adopting and reprinting the ACI 318 provisions.

HTH,

Scott
Ypsilanti, MI


On Mon, 18 Mar 2002, Ed Najjarine wrote:

> Syed,
>
> Since the governing code here is the UBC not the ACI, where is it specified
> in the UBC section 1910.5.3 that the 1/3 more steel than required by
> analysis then the minimum steel for flexural, is not applicable to HIGH
> SEISMIC AREAS?
>
> Ed
>
> -----Original Message-----
> From: Syed A Masroor [mailto:sam2000(--nospam--at)cyber.net.pk]
> Sent: Thursday, March 14, 2002 11:07 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Foundation Min. reinforcement
>
>
> Ed,
> Scott is absolutely right however, 33% higher is not applicable to:
> Beams in  high seismic category
> In slabs/footings, where temp. reinforcement (0.0018bh) governs
> IMHO, minimum temperature reinforcement should also be required in beams
> where
> 33% higher value will still fall short of 0.0018bh. Such conditions are
> often
> encountered when architecture dictates larger beam sizes.
>
> S A Masroor
> Consulting Structural Engineer
> Karachi, Pakistan
>
>
> Scott Maxwell wrote:
>
> > Ed,
> >
> > You are correct in that if you provide 1/3 more steel than required by
> > analysis then the minimum steel for flexural contained in 10.5.1 of ACI
> > 318-99 (the greater of 3sqrt(f'c)*bw*d/fy or 200*bw*d/fy) or 10.5.2 of ACI
> > 318-99 (similar to 10.5.2) need be provided.  This is provision is contain
> > in section 10.5.3 of ACI 318-99.
> >
> > Additionally, as others have pointed out, there is section 10.5.4 of ACI
> > 318-99.  This basically states that for structural slabs (i.e. supported
> > slabs not slabs-on-grade) and footings (i.e. spread footings) only need to
> > have minimum steel as specified in section 7.12 of the ACI code
> > (temperature steel).  This would not include slabs-on-grade since ACI 318
> > does not apply to slabs-on-grade except for a few special seismic
> > conditions (see section 1.1.6 of the ACI 318-99).  This also would not
> > include a grade beam, IMHO (but not a strip footing).  As others have
> > pointed out, a grade beam will either be to laterally tie footings
> > together for lateral loads, which would means that it is basically going
> > to be acting like a column, or it will be a flexural beam (i.e. loaded
> > flexurally and maybe axially) that happens to be sitting on the soil.
> > OTOH, a strip footing should have next to nothing in bending along its
> > length unless you have wide variations in soils conditions, but
> > potentially some serious bending perpendicular to its length depending on
> > its width.
> >
> > HTH,
> >
> > Scott
> > Ypsilanti, MI
> >
> > On Thu, 14 Mar 2002, Ed Najjarine wrote:
> >
> > > First, thank you all for your informative response, For Flexural
> Members,
> > > it's stated in the 97 UBC page 2-117, Sec. 1910.5.3 that as long as you
> > > provide 30% more Tensile reinforcement than required( which in my case a
> > > whole lot less than the minimum 200/Fy), the minimum reinforcement
> > > requirement does not apply. Any comments?
> > >
> > > Ed Najjarine, P.E.
> > >
> > >
> > >
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