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RE: moment frame achorage

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Thanks Mark, I appreciate that.  What you say makes sense.
I would then think that the grade beam could be modeled a beam, with the
moment of the column resolved in to two point loads.  The load from the
compression flange would be one support.  The tension in the anchor bolts
would be a point load very close to the support.  The other support would be
at the other end of the grade beam.  Stirrups could be provided to resist
the shear induced in the grade beam by the point load due to the anchor
bolts (neglecting the idea that it is within the depth of the beam to the
support).
Does that sound reasonable?

Thanks

-----Original Message-----
From: Mark Gilligan [mailto:m_k_gilligan(--nospam--at)yahoo.com] 
Sent: Friday, June 13, 2008 9:24 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: moment frame achorage

The secret to dealing with Appendix D is to realize that the provisions were
developed to deal with anchors in essentially unreinforced concrete.  This
is not the case with a grade beam.
Think of the connection as a D region that is resolved using a system of
struts and ties.  The tension in the anchor rods is a tie that is resolved
by one or more struts that in turn engage the stirrups in the grade beam.
I believe that the ACI 318-08 implicitly recognizes this approach.
Regarding the plates at the bottom of the anchor rod.  They should be sized
so that relatively little force is transfered by bending in the plates.  The
forces want to be resolved close to the rod.
Mark Gilligan

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