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Re: Out of Plane Wall Anchorage

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>
>In a message dated 12/2/99 6:42:36 PM, jwatson(--nospam--at)inconnect.com writes:
>
><< Why increase the member size while decreasing the force????
>
>Jake Watson E.I.T.
>Salt Lake City, UT >>
>
>The 3x requirement really came from use in panelized roof diaphragms, not 
>trusses.  The idea is that heavy double nailing on top of the diaphragm at 
>the plywood sheathing joint is already pushing the use of a 2x4 subpurlin 
>(for example).  Now drill a few holes in it for a HD or a CT at your wall 
>connection and you have Swiss Cheese.
>
>Howard Silverman
>Covert Operations, Inc.

What is the code definition of thickness?  I assume that the reasoning
behind this requirement is the typical 2x subpurlin used in California
(2x6, 2x8, etc.) has all of the nailing in the 1-1/2" wide piece (panel
edge nailing, anchors, etc.) and caused the splitting and failures.  Does
anyone know if the failure modes or reasoning was meant to include the
3-1/2" wide (thick?) by 1-1/2" deep flanges of a TJI type of purlin or say
a 2x4 flat blocking at the panel edges.  I don't see this as an issue that
would cause the same problems as seen with the 2x8 purlins.  I would think
that the 2x members should of been okay if the out-of-plane anchor is
attached to the side of the member and the nailing at the panel edges is 3"
or greater spacing.  This is one item that the local building departments
enforced and they read this requirement as the least dimension to be 2-1/2"
thick although we have been able to get TJI's approved during plan check.
We typically comply with the plan check comments and life goes on but I
don't always agree.  When will Simpson start making Z-clips for 3x members?

Peder Golberg, P.E.
Portland, OR