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RE: Allowable Out-of-Plane Lateral Deflections of Masonry Veneers

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Here is what I have found out on my own:

Section 6.1.2 (Design of Anchored Veneer) in the commentary of the
masonry code (ACI 530-02) references the BIA recommendations ranging
between h/600 and h/720. 

In the Masonry Designer's Guide published by The Masonry Society there
is a discussion regarding out-of-plane deflection. While it does note
that the masonry code requires the out-of-plane deflection of the
backing be limited, it does not provide a numerical limit. It further
states that building codes have limited the out-of-plane deflection of
structural walls to h/360, however this amount of deflection will
typically result in the veneer cracking and may cause serviceability
problems. 

Given the code commentary reference to the BIA recommendations and the
BIA recommendations themselves, I would say that the standard of care
should be h/600 for out-of-plane deflections.

Matthew Stuart 
Structural Department
Manalapan
Extension 1283


-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu] 
Sent: Thursday, March 01, 2007 12:44 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Allowable Out-of-Plane Lateral Deflections of Masonry
Veneers

Matthew,

My best guess is that the lateral deflection of the veneer is considered
a
servicability issues and not a life safety issue and as such the code
does
not address it.  This does not completely make sense to me because in
reality the vertical deflection limit of L/600 or .3" is basically also
a
servicability issue with little impact on life safety (not to mention
that
there are other areas in general were the codes have gone beyond life
safety).

I will see if someone I know has a better answer for you.

Regards,

Scott
Adrian, MI


On Wed, 28 Feb 2007, Stuart, Matthew wrote:

> Back in the early 1980's I believe, when Architect's started to go
with
> gage metal stud back up walls in lieu of CMU, the resulting
flexibility
> of the metal studs resulted in a number of problems with masonry
veneers
> primarily as a result of water infiltration through the mortar joints
as
> the brick flexed to a point in which there was actual separation
between
> the brick and the mortar at the joint interface. The metal stud
industry
> and brick industry began pointing fingers at one another with the BIA
> responding with an H/600 criterion. Most design engineers at the time
> had trouble accepting this criterion because after all L/360 had
worked
> for stucco finishes for some time. Never the less the H/600 got
codified
> into ACI 530 which adopted the criteria for vertical deflection only.
>
>
>
> Does anyone have any insight into the current lack of connection
between
> ACI 530 vertical deflection limitations and the current BIA
> recommendations for H/600 out-of-plane lateral deflection limitations?
> This is an issue because the ACI is a Code and the BIA provides
> recommendations only.
>
>
>
> D. Matthew Stuart, P.E., S.E., F.ASCE, SECB
>
> Senior Project Manager
>
> Structural Department
>
> Associate
>
> Schoor DePalma Engineers and Consultants
>
> 200 State Highway Nine
>
> Manalapan, NJ 07726
>
> 732-577-9000 (Ext. 1283)
>
> 908-309-8657 (Cell)
>
> 732-298-9441 (Fax)
>
> mstuart(--nospam--at)schoordepalma.com
>
>
>
>

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