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RE: Foundation Min. reinforcement

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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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