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RE: Hold downs with "Perforated Shear Wall Method" and "Force Transfer Method"

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Scott,

You wrote: "I agree that if, for some reason, you = check the wall
seperately for uplift and for overturning, then the same dead = load
should not be used in both check...but I would think you should be =
checking both uplift and overturning in the same check.
Am I missing something?"

Response: In the Wood Frame Construction Manual, we do check the wall
separately for uplift and overturning (because we provide those values
in 2 separate tables), so I wanted to make that distinction.

Thanks

Buddy

John "Buddy" Showalter, P.E. 
Director, Technical Media 
AF&PA/American Wood Council 
1111 19th Street, NW, Suite 800 
Washington, DC 20036 
P: 202-463-2769 
F: 202-463-2791 
http://www.awc.org 

The American Wood Council (AWC) is the wood products division of the
American Forest & Paper Association (AF&PA). AWC develops
internationally recognized standards for wood design and construction.
Its efforts with building codes and standards, engineering and research,
and technology transfer ensure proper application for engineered and
traditional wood products.

********************* 
The guidance provided herein is not a formal interpretation of any AF&PA
standard.  Interpretations of AF&PA standards are only available through
a formal process outlined in AF&PA's standards development procedures.

********************* 


From: "Scott Maxwell" <smaxwell(--nospam--at)umich.edu>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Hold downs with "Perforated Shear Wall Method" and "Force
Transfer Method"
I think I understand the intent of what you are saying, but wording does
bother me.
With wind or seismic in one direction so that the shearwall is not =
loaded, but there is overall uplift on that wall, there would be no
possible "double-dipping" as the wall would not be subjected to
overturning = (assuming a simple diaphragm, thus no torsional effects).
With the wind or seismic in the other direction, the wall (if a =
shearwall)
should be exposed to both overturning and potentially net uplift (due to
wind uplift or the vertical component of a seismic force...overall, more
logical to think about it in terms of net wind uplift) AT THE SAME TIME.
Thus, the same dead load should be resisting both the uplift AND the
overturning. In other words, your FBD of the shearwall will have the =
wind overturning force, the net uplift, and the 60% of the dead load
that = would work to resist both...all as loads applied to the
shearwall. I don't consider that "double-dipping". I agree that if, for
some reason, you = check the wall seperately for uplift and for
overturning, then the same dead = load should not be used in both
check...but I would think you should be = checking both uplift and
overturning in the same check.
Am I missing something?
Regards,
Scott
Adrian, MI
-----Original Message-----
From: Showalter, Buddy [mailto:Buddy_Showalter(--nospam--at)afandpa.org] On Behalf Of
= AWC Info
Sent: Friday, May 23, 2008 9:47 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Hold downs with "Perforated Shear Wall Method" and "Force
Transfer Method"

One caveat however, the WFCM does not use dead load to offset uplift and
= use the same dead load again to offset overturning (double-dipping).
So in = the WFCM tables, we only show dead load offsetting uplift loads.

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