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Re: shear wall blocking

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Well, here is another opinion based on $0.02 worth of knowledge.

Technically, if green lumber is used which subsequently seasons (dries),
the NDS
seasoning factor of 0.70 should be applied to fastener lateral loads.
However, it
is my opinion that the seasoning affects only fastener slip, not lateral
load
capacity (e.g., strength limit state). Thus it may not have a real
affect on load
capacity of shear walls or diaphragms. This issue is on the agenda for
the CUREe
Woodframe Project as one of the subtasks.\

A second issue regards the blocking for shear walls or diaphragms. The
fastener
loads are generally along the length of the blocking for either
application, thus
fastener loads perpendicular to grain which cause cross-grain tension
are not
present in these applications. The splitting potential mentioned in my
earlier
posting relates to the tendency of the flat grain wood (side faces of
blocking when
oriented flatwise) to split if a lot of fasteners (nails) are driven at
close
spacing into the blocking.

Hope this helps.

John Rose/APA, Tacoma, WA

chuckuc wrote:

> George-
> A better question is does anyone apply the reduction to shearwall capacity when
> the studs and sills are green?  I've heard both Dan Dolan (a notorious
> "liberalizer" from Virginia Tech) and Buddy Showalter opine that we should, but
> I've never seen anyone do it.
>
> As to flat blocking, visualize the sheathing as a diagonal tension field.  The
> blocks don't rotate so they don't need a tight fit, but they are in cross grain
> tension.  The deeper the section the less the tendency to split.
>
> Unfortunately, I haven't seen any test data on either issue.
> Chuck Utzman
>