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RE: Grade @ Anchor Bolts

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Nels-
I guess my word picture was a little obscure.  What I meant was the tension
reinforcement yielding would act to redistribute the load to the various
nuts on the all-thread.  It would seem that the ductility you would get from
this would approximately balance the loads to each of the nuts you spaced at
8" o.c.  The all-thread would need to be sized to remain elastic at yield of
the rebar.  Strain compatibility would mean that the actual yield
deformation would be small in the rebar since the all-thread remains elastic
and the vertical strains would need to be nearly the same.  Also, it is
desirable if the yield strength of the all-thread is above the yield of the
rebar (may not be easily achievable with Grade 60 rebar). I agree that it is
not a good idea to yield the all-thread if you can yield a more ductile
element first.  However, I would consider yielding the all-threaded in
preference to developing a shear cone failure in the block and grout.
Regards,
Bill Cain,  S.E.
Oakland CA

	-----Original Message-----
	From:	Nels Roselund [SMTP:n.roselund(--nospam--at)worldnet.att.net]
	Sent:	Monday, August 21, 2000 9:42 AM
	To:	seaint(--nospam--at)seaint.org
	Subject:	Re: Grade @ Anchor Bolts

	Bill,

	Yes, the detail I used was an all-thread rod with spaced nuts (8"
spacing).
	The rod was extended vertically into the wall with the intention of
	developing its tension load into the adjacent tension reinforcement.
My
	thought was to make the load transfer relatively local and direct
rather
	than from a single zone at the bottom of the rod.

	I'm not picturing what you mean about yielding of the vertical steel
with
	multiple bolt installations.  I don't like the idea of designing a
threaded
	rod to yield.  Yield in a threaded rod can only occur at the bases
of the
	threads -- it can't be uniformly distributed over a length of the
rod --
	that seems likely to be a brittle condition.

	Nels Roselund
	Structural Engineer

	-----Original Message-----
	From: Cain, William <bcain(--nospam--at)ebmud.com>

	>Unless you are relying on yielding of the vertical steel with
multiple bolt
	>installations, I would be careful of a multiple nut configuration
(assuming
	>you mean they are spaced so that the cones don't overlap
vertically) since
	>the failure of a grouted concrete block wall shear cone would be a
brittle
	>failure.  If there is sufficient vertical steel, such a detail
might be
	o.k.
	>
	>Regards,
	>Bill Cain, S.E.
	>Oakland CA
	>
	>



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