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Cutting into post-tension slabs in a high rise

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Two types; from a currently Registered Structural Engineer,
who is familiar with PT designs: (1) bore completely
underneath the slab to the point(s) where the electrical or
water lines will penetrate the slab vertically, or (2) have the
electrical \ water lines installed to right up against the slab,
and then, ...enter through a wall penetration.

Essentially, ...IMO, do not cut \ "channel out" the slab.
Too much potential for cracking \ damaging the existing
slab.

I know that in some places, they DO "channel out" cuts,
but is usually done very selectively to minimize the effects
of the cuts.

& = & = &
 
I haven’t encountered a successful channel cut in a post tensioned slab. Mostly because they didn’t know that it was a post tensioned slab. I might have pictures of the repair. There’s supposed to be a sign stamped in the garage slab that warns of the tendons.
 
If by channeling our a post tensioned concrete slab you mean cutting a horizontal slot in the slab my response is that you don't. Even if you can avoid cutting the tendons you run a real risk of reducing the strength of the slab. Post tensioned slabs are less tolerant of structural modifications than are other structural systems.

Any cutting of a post tensioned slab should only be undertaken after a review by a structural engineer. When cutting is contemplated they should use x-ray or ground penetrating radar to determine tendon locations.
 
Mark K said:
If by channeling our a post tensioned concrete slab you mean cutting a horizontal slot in the slab my response is that you don't. Even if you can avoid cutting the tendons you run a real risk of reducing the strength of the slab. Post tensioned slabs are less tolerant of structural modifications than are other structural systems.

Any cutting of a post tensioned slab should only be undertaken after a review by a structural engineer. When cutting is contemplated they should use x-ray or ground penetrating radar to determine tendon locations.
Click to expand...

That is what we require. A structural engineer and an xray of the area marking out the tendons. This is a critical part of plan review. We need to know whether or not any modifications are planned that would involve cutting or boring into the slab. It limits the amount of work that can be done such as installing an island for a kitchen or moving a bathroom.
 
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