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# Re: Wood: 'en' and Plywood question.

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Wood: 'en' and Plywood question.
• Date: Thu, 15 Jul 1999 23:04:41 -0700

Dennis, I agree with your interpretation below.  What isn't stated is that with
sheathing on both sides of the wall, nailed with the same schedule, the shear
capacity doubles.  The extra capacity is not utilized since the shear demand
(load) is the same in your example.  Thus, the wall will be stiffer when
sheathed both sides instead of one side, for a given shear demand.  This also
was pointed out in one of the other responses.
You guys are going to force me to bring my APA lit. and UBC home, so I can
John Rose/APA

Seaintonln(--nospam--at)aol.com wrote:

> Al, you misunderstood the question. This has nothing to do with the capacity
> of the nail. It is related to the calculation for deflection which assumes
> that the actual shear in the panel is distributed uniformly to each nail at
> the edge of the panel. Therefore if you had 240 pounds of shear per foot and
> the panel was nailed one one side at 6" o.c. you would have two nails per
> foot and each would take 120 pounds of the shear. My questions was then if
> you sheathed both sides of the wall, you would end up with 4 nails per foot
> (two per each side). I asked if it was appropriate in the deflection formula
> to then consider the load to each nail as 60 pounds per nail.
>
> I think that this is the correct interpretation of the problems.
>
> Dennis Wish PE
>
> In a message dated 7/15/99 8:35:19 AM Pacific Daylight Time,
> AGrathwol(--nospam--at)BoyleEngineering.com writes:
>
> <<
>  > 1) I know this is an elementary, but I want to make sure I
>  > have it right. If
>  > you sheath both sides of the wall using the same nail pattern
>  > (who wouldn't?)
>  > do you reduce the nail capacity in half?
>
>  I don't know why you would do that.
>
>  > For example if you have 8d at 6" on the edge on one side, the
>  > capacity per
>  > nail is v*(6/12) per nail. However, if both sides are
>  > sheathed with 8d at 6"
>  > o.c. is the capacity per nail v*(6/24) ?
>
>  I see no reason to reduce the strength.  The nails on one side of the wall
>  don't know that there are nails on the other side!
>
>  >
>  > 2) What thicknesses of plywood and OSB are commonly used for
>  > shearwalls. I
>  > always specify 15/32" 5-ply (struct I) panels but understand
>  > that some use
>  > 3/8 or 1/2". With all of the choices for plywood's to determine wall
>  > deflections, which panels should I be considering for common
>  > use in all of
>  > the area's of the US (since the program calculates wind loads
>  > as well).
>
>  The UBC tables specify an allowable shear for various plywood thicknesses.
>   >>
>