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RE: Deflection criteria for veneer support

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When I have long span like 30 feet, rather than design for 0.3 inches I
put in several crack control joints and design the lintel to carry all
the brick load, no arching action.  I usually start with a joint up the
jambs and then add joints at about 10 feet on center, depending on the
span.  I then try to keep my deflection more in line with l/500 to
l/600.

Rich Lewis
Lewis Engineering
 
 

-----Original Message-----
From: mredling(--nospam--at)degenkolb.com [mailto:mredling(--nospam--at)degenkolb.com] 
Sent: Tuesday, January 18, 2005 3:05 PM
To: seaint(--nospam--at)seaint.org
Subject: Deflection criteria for veneer support





Hello all,

The 2003 IBC references the ACI 530, which states in 1.10.1: "Deflection
of
beams and lintels due to dead plus live loads shall not exceed the
lesser
of l/600 or 0.3 inches when providing vertical support to masonry
designed
in accordance with Section 2.2 or Chapter 5."

This is a significant departure from the previous UBC requirements of
designing to l/600.

I have discussed this issue with people very knowledgeable about masonry
and they said that there have been some cases recently where veneer has
cracked due to deflection.

Still, the deflection criteria of 0.3 inches seems excessively strict
for
long beams.  (For a 30' long beam, the you would be required to design
for
less than l/1200.)

Has anyone had any experience with the new deflection criteria in the
2003
IBC for the support of brick veneer?  Has this "0.3 inch" requirement
been
enforced?

Thanks,
Mark J. Redlinger, SE


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