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RE: Post-tensioned slab on grade

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One method of adding a new opening to unbonded PT construction:

1) Snap lines on slab locating the new opening.
2) Determine and mark tendon locations on slab.
3) Demo small openings in slab to expose each tendon about 6"-12" outside of
new opening.
4) Install slotted bearing plate and split donut anchor onto strand.
5) Hand seat wedges into split donut anchor.
6) Grout small openings used to access strands.
7) Cut out slab after grout reaches 3000 psi.

If you have a bonded system - just cut the opening.

Brent Koch, P.E.
Livermore, CA

-----Original Message-----
From: Juan C. Gray [mailto:juangray(--nospam--at)]
Sent: Thursday, November 05, 1998 10:55 AM
To: seaint(--nospam--at)
Subject: Re: Post-tensioned slab on grade

We recently built an 8" thick post-tensioned slab on grade , with
overall dimensions 120 by 90 feet. The active reinforcement is 1 strand
with 1/2" dia. every 2 feet, in both directions and placed in the middle
depth of the slab.
Now the owner needs two openings of 3 by 8 feet along the edges of the
I am worried  about cutting the tendons to make room for these openings,
because I'm not sure if the release of energy when I cut them may damage
the slab. Does anyone have any suggestion ?

Juan Carlos Gray