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Re: Concrete Load Brg Wall with Conc Beams

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James,

One simple solution is to allow the end of the beam at the wall to be an
"unrestrained" end (i.e. "pin" connection).  This would mean that you
would not need to develop any negaitve moment steel since there would be
no negative moment.  The down side is that the positive moment in the beam
will increase.  Under section 8.3.3 of ACI 318-99, the positive moment
would become wu*ln^2/11 instead of wu*ln^2/14 (this assumes that you meet
the general requirements of 8.3.3...two or more spans; spans approximately
equal, etc).

This solution is primarily there for your type of situation...that is when
the support condition really does not support a restrained connection that
would require a significant negative moment.

HTH,

Scott
Ypsilanti, MI


On Fri, 19 Jul 2002, James Lane, P.E. wrote:

> 
> 
> A 12 inch thick load bearing wall multiple stories. Heavily reinforced 
> concrete beams on grid coming into bearing wall. Is it ok not to develop the 
> beam bars (not enough wall thickness. Wall must satisfy ACI 14.4.
> 
> I say negative steel should be developed by a haunch or something similar 
> and design wall for additional haunch moment. Looking for other engineers 
> comments regarding development of beam steel in exterior walls.
> 
> I have heard one response that does not develop the beam steel and treats it 
> as a partial fixity letting the negative steel yield and redistributing beam 
> moments. If you do not develop the beam steel how can you be sure that the 
> end moment does not pull out the partial developed bars causing failure?
> 
> 
> 
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