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RE: Broken Tendons

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Hi Mark,

	Thanks for your concern.  I had to put this job aside for a while, but just
got back to it today.  To the best of my knowledge, it is not a
slab-on-grade.  I'm still trying to find out what happened, where, how, and
why, but, as it is a large parking lot, and the slab-on-grade has been
poured for several months (probably over a year, by now), I don't believe
that it's an s-o-g.

	After checking ACI (a most helpful tip, by the way; I had checked PCI and
PTI without result, and I didn't think that ACI 318 would have anything
useful.), and thinking about everything, I've come to the conclusion that
the procedure for checking the adequacy of the slab is OK, but that (per
ACI) too many tendons were used to check adequacy: all of the tendons in the
bay were used, instead of the tendons in a particular strip.  Right now, I'm
still trying to get the exact location identified.  (Getting info is like
pulling teeth, sometimes.)

	I'll let you know what I find out, and what ultimately happens.  Thanks
again.

John



-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
Sent: Wednesday, June 13, 2001 11:22 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Broken Tendons


John,

Is this a slab-on-grade?  In your most recent post, you indicate that it is
a
"parking lot slab."

Unless a slab-on-grade has been designed like a ship, for a hogging
condition
and for a sagging condition, the post tensioning is more likely just for
crack control.  Locally, post tensioning is being used for slab-on-grade
residences but, unfortunately, just as crack control mechanisms.  (Tendons
put in so that calculations will show 150 psi compression in the slab, and
nothing else is considered.  Concrete strengths as low as 2,000 psi have
been
specified.)  [N.B. I do not advocate or approve of this "design" method,
but merely stating what is being done locally.]  Regardless of how/if it has
been designed, post tensioning is being used as a marketing tool by the home
builders.

HTH

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

John Dreger wrote:

. > Hi Mark, Hi Syed,

. >         I just got notification that this reply didn't go through the
. > first time, so, I'm going to try again.

. > Original message:

. >         I'm going to reply to both of your responses together, so that
. > anybody reading this won't have to go through the same stuff twice. I'd
. > like to start by thanking both of you for your responses.  You both
. > covered a great deal of material, and clearly spent quite a bit of time
. > on it.  I really appreciate your time and effort.

. >         The slab is a solid slab for a parking lot that is currently
under
. > construction.  I assumed that the tendons were prestressed, since that
was
. > the only situation that made sense to me: if it's post-tensioned on
site,
. > then all they had to do is replace the tendon and start over.  Other
than
. > that, I don't have much information.  Part of this is my fault: having
. > several jobs going on, I didn't spend the time that I should have
getting
. > answers.  I did send a fax to the contractor for more info, but have yet
. > to have any of my questions answered; I don't even know which tendon
. > broke or under what circumstances.  All that I've been told is that the
. > tendon supplier did some calcs, and that that was the procedure

[Remainder snipped]

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