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RE: Blocking around small holes in plywood shear walls?

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SBCCI Standard for Hurricane Resistant Construction SSTD 10-99 is the only
place I'm aware of that has prescriptive criteria for holes.  For shear
walls designed per the segmented approach, a opening of 144 sq in (with no
side greater than 12") does not require blocking.

Mr. Watson's recommendations below have also been used for a series of small
holes.  Since I am familiar with our recommendations, I'll restate them.
The shear strength of 15/32" plywood per APA N375B is about 740 plf per
Table 2.4.  This number can be adjusted by a load duration factor of 1.6 (or
1.33, check your jurisdiction).  If one uses Str. I plywood or OSB, this
value can be further increased by a factor of  l.7 or 3.1, respectively.
So, the design shear strength of the panels are generally much greater than
the shear force one can transfer into the panel with fasteners.  The
conventional shear wall table has no design value greater than 870 plf....
So, the strength of the panel is generally not an issue.

Finally, for very narrow wall segments (say approaching maximum aspect ratio
of 3-1/2:1), one may want to put some additional thought into the size of
the hole.

http://www.apawood.org/pdfs/managed/N375B.pdf

Tom

-----------------------------------------------------------------------
Thomas D. Skaggs, Ph.D., P.E.
Senior Engineer
APA - The Engineered Wood Association
7011 S. 19th Street
Tacoma, WA 98466
ph: 253/565-6600
fx: 253/620-7235
-----------------------------------------------------------------------


> -----Original Message-----
> From: Jake Watson [mailto:jwatson(--nospam--at)utahisp.com]
> Sent: Friday, August 01, 2003 9:30
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Blocking around small holes in plywood shear walls?
> 
> 
> Just a thought, and I have never done this myself.  Plywood 
> has a shear
> value, we just normally check the nailing.  Could you check the shear
> capacity of the plywood to determine how much would have to 
> be intact?  You
> will probably have to look at where the holes occur.  If they 
> are close to a
> joint, that may give you some trouble.
> 
> Not much help, but hopefully a little.
> 
> Jake Watson, P.E.
> Salt Lake City, UT
> 
> -----Original Message-----
> From: Bill Allen [mailto:T.W.Allen(--nospam--at)cox.net]
> Sent: Wednesday, July 30, 2003 2:31 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Blocking around small holes in plywood shear walls?
> 
> 
> Is anyone aware of a requirement for blocking around small holes in
> plywood shear walls such that holes smaller than the 
> specification would
> not need to be blocked? Sorry, but I'm working with that antequated
> building code known as the UBC. If someone who knows the dividing line
> (6"x6"? 8"x8"?) and can cite a code reference, I would be most
> appreciative. I've got a building inspector wanting the contractor to
> block around EVERY little penetration. The contractor seems 
> to recall a
> "schedule" he once saw on a set of drawings (obviously not mine) which
> would help him out.
> 
> TIA,
> 
> T. William (Bill) Allen, S.E. (CA #2607)
> V/F (949) 248-8588
> San Juan Capistrano, CA
> 
> 
> 
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