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# RE: Torsion in Masonry Beam

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: Torsion in Masonry Beam
• From: "Eric Ober" <eober(--nospam--at)holbertapple.com>
• Date: Thu, 15 Apr 2004 12:20:14 -0400

```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?

Rich

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