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RE: Related: shear values using staples and nails

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Section R602.3 requires "Structural sheathing shall be fastened directly to structural framing members".  Although I'd interpret table R602.3(2) as permitting staples in lieu of nails for Method 3 bracing, the panels still have to bear directly on the studs.
 
The APA Technical Note you are citing (APA Rated Siding Panels Over Rigid Foam Insulation Sheathing, Form Number C465), was based on tested assemblies.  Any deviations from these assemblies would require either additional testing or engineering judgment.  I have absolutely no test experience with staples, so I do not have an informed opinion.
 
Tom
 


From: Jim Wilson [mailto:wilsonengineers(--nospam--at)yahoo.com]
Sent: Wednesday, March 29, 2006 9:01
To: seaint(--nospam--at)seaint.org
Subject: Related: shear values using staples and nails

How would a similar condition apply to the IRC, specifically, wall bracing method 3 per R602.10?  IRC Table R602.3(2) lists staple patterns for various sheathing thicknesses, but I am unclear from other sections if this is an available option for wall bracing.
 
To make it more questionable, the sheathing is T1-11 applied over 1/2" of foam insulation.  I found the APA documents that permit this construction with nails.  But I am inclined to discount the staples because the connection is through the flexible foam layer.
 
Jim Wilson

Tom Skaggs <tom.skaggs(--nospam--at)apawood.org> wrote:
The (1-(0.5-SG)) adjustment factor was based on a study we conducted on
nails. The underlying basis of this adjustment factor are the yield
equations in the National Design Specification, which were introduced in
1991. Based on this study, we determined that the old adjustment
factors (pre 1991, which are currently being used for staples) were very
conservative for nails. We never considered the use of staples in our
study. When staples were added to the shear wall table (2000 IBC), the
proponent of this code change was "fine" with the old adjustment
factors.

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
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-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
Sent: Tuesday, March 28, 2006 21:30
To: SEAINT
Subject: Re: shear values using staples and nails

Drew:

I am not sure I see what you are seeing. To me, the footnote definitely
has you "correct" for framing members of difference specific gravities
than DougFir or Southern Pine, but has you do it in different manners
for staples than for nails. The note has you adjust the Struct I panels
capacities for staples whether the plywood/OSB is Struct I sheathing or
not and using a flat adjustment of 0.82 for most framing species (SG of
0.42 or greater) or 0.65 for others. The note then has you adjust the
shearvalues for the framing with nails based upon the actual sheathing
used and adjusting those values based upon the formula of (1-(0.5-SG))
but not more than 1. Thus, you effectively would "adjust" the nail
shear values of the appropriate sheathing by a factor of 0.81 (lowest SG
in the NDS is 0.31) to 1.0 (any SG of 0.5 or greater would result in the
equatione resulting in 1 or greater).

My guess is the difference is likely due to the failure mode. I would
guess that the failure of the nail based shearwalls is your typical
shear wall failure of the perimeter fastners failing by deformation of
the plywood/OSB at the nail and/or deformation (bending) of the nails.
On the other hand, my guess is that the staple based shear walls fail
purely due to the staples and are not really effected by the sheathing
or framing wood...at least as much.

Just my thoughts.

Regards,

Scott
Adrian, MI

On Tue, 28 Mar 2006, Drew Morris wrote:

> For determining the allowable shear for OSB/plywood shearwalls, IBC
> Table 2306 (varies by edition), footnote a allows you to use the
> values for Structural 1 after correcting for the actual specific
> gravity when using staples, but not for nails. Anyone know why this
is?
>
>
>
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