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Re: Plywood shearwall in Plumbing Wall

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Joe-
First I'll stipulate that my drawings have a standard detail for the repair of plates (top or bottom) with holes cut in them. The code also requires an anchor bolt within a foot of each end. That said, Rand is essentially correct.

When an earthquake moves the foundation, the anchor bolts move the sill, the sill nails move the plywood, the top plate nails move the top plate, and the framing clips drag the eave blocks, etc. Most of the time interruptions in either the top or bottom sills would have no significant effect on capacity or failure mode. Now, if either sill is being used as a drag/collector, it could be a problem depending on where the interruption occurs.

None of this has anything to do with the vertical framing members. As each sheet of plywood rotates, the vertical nails lift up on the stud and the adjacent sheet's nails push down. Everything balances until you get to a free edge & may need to add a tie down.

Well distributed, modestly loaded shearwalls aren't going to mind an occasional discontinuity. It happens a lot when inspection is lax.

Chuck Utzman, P.E.
Jnapd(--nospam--at)aol.com wrote:

Rand:

We agree the top plate needs to be continuous in a wood shear wall; therefore uniformly distributing the load to the plywood. I and several others I am sure would not waste time and money to determine the load to each smaller section of bottom plate. Would you use rigidity analysis to distribute the load to each section or section length? Should there be a post and holdown at each break in the bottom plate. By using the methodology that the bottom plate can be segmented how does that effect the plywood. Will this possibly induce a tear in the plywood at the end of a bottom plate segment if you don't use a post and holdown ?

Most contractors and Architects we have dealt with understand that cutting up a shear wall is not a responsible thing to do from a city inspection and a liability point of view.


Joe Venuti
Johnson & Nielsen Associates
Palm Springs,  CA




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