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Re: Torsion in Masonry Beam

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A precast lintel wouldn't work here.  It needs to be cast in place.  The
CMU wall is on a radius.  I was trying to eliminate a trade by keeping it
masonry.  If I make the mason build to lintel height, wait for a concrete
crew to form and pour a lintel and then come back, it seems to me to be
added cost.  if I can get the CMU to take the torsion then the one trade
can just go wild on the wall until it's done.

Rich

On Thu, 15 Apr 2004 12:20:14 -0400 "Eric Ober" <eober(--nospam--at)holbertapple.com>
writes:
> Rather than 'pushing the envelope' of the masonry code, why not use 
> a
> precast lintel here, reinforced as appropriate, and figure out an
> appropriate bearing anchorage at the ends to resist the torsion?
> 
> Eric Ober
> 
> -----Original Message-----
> From: richard lewis [mailto:rlewistx(--nospam--at)juno.com] 
> Sent: Thursday, April 15, 2004 10:01 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Torsion in Masonry Beam
> 
> I am designing a CMU lintel across an opening.  The opening is about 
> 11
> feet wide.  The wall is curved, putting the lintel into torsion 
> along
> with the typical bending and shear stress.  I am looking through the 
> ACI
> 530.1 code and they don't address torsion specifically.  I know 
> torsion
> is just shear stress so I was thinking of calculating the shear 
> stress
> from torsion and adding it to the beam shear and designing it that 
> way. 
> I pulled out my old "Beers and Johnston" strength text and looked 
> up
> torsion on a noncircular section.  The shear stress equation is
> stress=T/(C1*a*b^2).
> 
> My question is how to address this with the ACI code.  I am going to 
> put
> in stirrups for shear.  The above noted equation is for the maximum
> stress at the outer fiber.  The code equation is an average stress 
> over
> the shear area.  It states that Fv shall be less than 3*sqrt(f'm).  
> 
> 
> 1. Since the shear stress in torsion calculated above is for the 
> maximum
> stress, how should I apply it with the ACI maximum limit?  In order 
> to
> size the stirrups?
> 
> 2.  ACI states As=V*s/(Fs*d).  How should I combine the shear stress 
> and
> the beam shear to get a total 'V' for the shear stirrup equation?
> 
> Thanks for your insight!
> 
> Rich
> 
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