PT Slab Cutting

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PT Slab Cutting
PBL Group Ltd.
8/11 Soi Viphavadi 44, Viphavadi-Rangsit Road,
Lardyao, Jatujak, Bangkok 10900,Thailand.
Presentation by Mr. Prapat Boonlualoah CEO, PBL
Group Ltd., Bangkok
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General Considerations
In a typical post tensioned floor it is possible
to locate penetrations of up to 1000 by 3000 mm
(3 by 9ft) between post tensioned tendons and to
require no other modification to the floor.
Penetrations that require cutting of the post
tensioned tendons will need to be checked and
designed as would any large penetration in any
floor using bonded tendons is as follows
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Slab Cutting Procedures Bonded Tendon
1. Design the modified floor structure in the
vicinity of the penetration assuming that any cut
post tensioned tendons are dead-ended at the
penetration. 2. Install any strengthening
required. 3. Locate tendons and inspect
grouting. 4. If there is no doubt as to the
quality of the grouting, proceed to step5.
Otherwise strip off ducting, clean out grout,
and epoxy grout the strands over length of 500 mm
(20 in) immediately adjacent to the penetration.
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Slab Cutting Procedures Bonded Tendon
5. Install props. 6. Core drill the corners of
the penetration to eliminate the need for over
cutting, and then cut the perimeter using a
diamond saw. 7. Cut up the slab and remove. 8.
Paint an epoxy-protective coating over the ends
of the strands to prevent corrosion. 9. Remove
props.
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If a large penetration through a floor cannot be
locate within the slab area but must intersect a
primary support beam, then substantial
strengthening of adjacent beans will usually be
necessary.
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Slab Cutting Unbonded Tendon
When cutting openings into floors built using
unbonded post tensioned tendons the procedures
used for bonded post tensioned tendons cannot be
applied. The preferred procedure that has been
developed to permit controlled cutting of
unbonded strands is to use a special
detensioning jack, The jack grips the strand and
the strand is then cut, with the force in the
strands being released slowly. New anchorages are
then installed at each side of the new opening
and the strands re-stressed.
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Demolition of PT Slab
Extensive experience has been gained in
demolition procedures for post tensioned floors,
and some general comments are made. In bonded
systems the procedures for demolition are the
same as for reinforced concrete. The individual
strands will not dislodge at stressing
anchorages. In unbonded systems the strand
capacity is lost over its entire length when cut
therefore the floor will require back propping
during demolition. The individual cut strands
will dislodge at stressing anchorages, but will
move generally less than 450 mm(18 in). However,
precautions should always be taken in case the
strands move more than this.
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Project References

• The Emporium (Tower Zone) Bonded
• 2. Fortune Complex Bonded
  and Unbonded
• 3. The Emerald Hotel -
  Unbonded
• 4. Exim Bank
  Unbonded
• 5. Riverside Garden Marina Bonded
• 6. Atthenee Residence Bonded
• 7. Atthenee Tower
  Bonded
• 8. Empire Place
  Bonded
• 9. Riverine Place
  Bonded
• 10. CP Tower
  Unbonded
• 11. Manhattan Chidlom - Bonded

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Thank You!