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Re: Plywood shear wall definition

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On 26 Jan 2005, at 10:33, Mark Schroeder wrote:

> Does anyone have any input to the following?
> Question number 1:  Is it possible to have plywood occur on one face of a wall for the upper portion
> of a shearwall and the other face for the lower portion of a shearwall if all required blocking,
> etc. is present?

This seems like it should work.  You will probably want to use a Simpson Coil Strap or similar
at the blocking location to help with the shear transfer through the blocking into the plywood on
the other side of the wall.  If you strap both sides of the wall, you should get the needed shear

> Question number 2:  Can a setback of 2" occur in the plane of a plywood shearwall?  For example, if
> there is a transition from 2x6 studs to 2x4 studs that are properly connected together to transfer
> all shear, etc., would such an assembly be considered one wall or two different walls to determine
> aspect ratio, holdown requirements, etc.

This, too, seems to work.  The problem that I see is the shear transfer from the 2x4 section to
the 2x6 section.  If you can make the face of each stud size coplaner and sheath over both stud
sizes then you get good shear transfer through the plywood.  I would prefer to see the 2x6
section to be below the 2x4 section.

In terms of the aspect ratio, holdowns, etc., you would need to use the combined height of
the two sections.  I'm basically thinking of this system as one in which the blocking is one
continuous member and not the 14.5" members that we usually see for blocking.  We wouldn't
use blocking height for calculating the aspect ratio, holdowns, etc.  Unless we were using the
'97 UBC Force Transfer Around Openings methodology. (Fig 23-II-1, p 2-290, '97 UBC)  For
that methodology, you might be able to justify the use of the shift, if it occurs at an opening,
and you are providing for the force transfer.  So, it seems that the full, combined height should
be used.

> Any input would be greatly appreciated.  Thanks,
> Mark E. Schroeder, S.E.
> Ficcadenti & Waggoner, Inc.
> 16969 Von Karman, Suite 240
> Irvine, California 92614
> (949) 474-0502 Phone
> (949) 474-1801 Fax

Hope This Helps,

Take care,
Lloyd Pack, P.E.

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