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RE: Hold downs with "Perforated Shear Wall Method" and "Force Transfer Method"

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Joe Grill wrote:

"I am getting a lot of hold downs using the traditional segmented
design. I am
going to get some real comments from the number of hold downs for this
small
structure.  Therefore, I started looking at the other two methods to cut
down on the number of hold downs."



I use the force transfer method most of the time, and detail openings
that do not have enough plywood around the opening to transfer the load
with CS16 strapping over the plywood at header and sill, 3' onto the
hdr/sill & 3' blocked back into the diaphragm.  Once you know that the
header won't pop off the trimmers you can expect the wall to behave as a
longer unit including the opening.  But...you have to know that the load
can really be transferred at the boundary of each pier.  If there's too
much, you need to anchor it.

Look at the uplift or OT at the end of the pier (including -60% of the
DL (max)), and subtract your plywood capacity from Table 2306.1 (180plf
if unblocked, run vertically--you can increase this based on your
specified blocking/nailing/ply direction, but I always use Case 2, 8d
@6,12, 7/16" ply, 2x framing members for this analysis b/c it's the
worst case, and quite often what I end up seeing in the field) x length
of shearwall above & below the opening.  What's left is what you have to
hold down, but quite often this quick analysis will obviate the need for
holdowns at many piers.


regards,
Gordon



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