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RE: Broken Tendons

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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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