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RE: ACI 318 App D, and wedge anchors

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Jared Keyser wrote:

<< I have wondered about presenting the case that in wood construction,
if the anchors are sized such that the shear chord nailing fails prior
to developing the concrete breakout force in the anchor, you have
essentially provided a ductile yielding connected element.  As such, you
have met the ACI provisions.  This assumes that nail pullout is a
ductile failure mechanism, which in the case of cyclical seismic forces,
I believe this argument is valid, at least based on the high R-value
permitted to be used in design.  The problem with this is QA/QC and
making sure the contractor does not over-nail the chord and force the
weak link back to the anchor.>>  



This is the theory I use...it defaults you to D.3.3.5.  For an 8"-wide
stemwall, You can make an HTT16 work w/ Simpson spec'd nailing, but not
an HTT22.  I would not count on (nor encourage) a contractor to
under-nail an anchor. 

The real problem, though, is that post-installed anchors work better, by
taking a bunch of slack out of the system.  It's the only way I see the
anchor aligned w/ the shearwall chord.  Often the cast in place anchors
are out by inches.  Nobody wants to see the contractor torque the HD
strap over to the stud, although many do.  So is the epoxy AB that
doesn't meet ACI 318 D.3.3.4 worse than the dynamic increase in load due
to poorly installed SSTBs?  I don't think so, but it's a good question
you raise.


regards,
Gordon Goodell





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