Final ct aa slides

Technology
TAN KAI XUAN 0325077 | TEE WAN NEE 0325074 | TANG LAM YU 0324966 | YAP CHOE HOONG 0323161
Construction Technology III

POST-TENSIONING STRUCUTRAL ELEMENT
WHAT IS PRESTRESSED CONCRETE ?
The tendons are tensioned prior to
the concrete being cast.
A method in which compression
force is applied to the reinforced
concrete station.

PRE-STRESSED = PRE-TENSIONED POST -TENSIONED
• Concrete is pre-stressed with
tendons before placing in
position.
• Preference : structural element is
small and easy to transport.
• Pre-stressing is done only after
the concrete attains sufficient
strength in other way after the
concrete has been casted.
• Preference: Structural element is
heavy.

Primary function to place concrete
structure under compression in regions
where loads causes tensile stress.
Applies compressive stresses on the
material, balancing off tensile stress on
the concrete.
All construction joints and
crack control joints could
be eliminated because the
slab was poured
monolithically.
Provide sufficient pre-
compression on the slab.
Introduction + Function )

Slabs on grade (office
buildings, multi-storey car
parks, warehouses etc.)
Floor slabs Bridge
Main beams
Cantilevered
Structures
Foundation Slabs
(rafts)

Single Strand
Bonded Post-Tensioning
Unbonded Post- Tensioning
Single Strand
Multi Strand Flat Duct
Multi Strands Round Duct

End
Cap
Grout
Valve
Pocket
Former
Strands
Grout Pipe
Wedges
Strands
Anchor
Head
Bearing Plate
Duct
Flat Duct Round Duct

Floor System Reinforced with
Grouted Post-Tensioning System
Flat Duct
Post- Tensioned Mat Foundation
using grouted Tendons
Flat Duct

Anchorage Assembly
Details of unbonded
post - tensioning
Stressing Jack
Tendon Tail
(Additional length will be cut off)
Wedges
Stressing
Anchor
Split Pocket Former with
Intermediate Anchor
Pocket Former

Example of a Floor System using the
Unbonded Post-tensioning System
Fortaleza, Brazil.
MAT FOUNDATION USING UNBONDED
TENDONS

BONDED POST-TENSIONING UNBONDED POST-TENSIONING
 Develops higher flexural strength. Provides greater available level arm
Does not depend on anchorage after
grouting.
Simplifies pre-fabrications of tendons
Localize the effects of damages. Grouting not required
Simple technique for demolishing or
providing future opening in slab.
Can be constructed faster

2. Casting of concrete
Pouring of concrete. The
concrete must achieve
proper strength before the
tendons are tensioned.
There is grout valve
for it to fill the ducts
are filled with grout.
Ducts not grouted and
tendon is held by the
end anchorages.
BONDED
UNBONDED
3. Tensioning of tendons
Tensioning of tendons is applied by
a jack. The tensioning of tendons
and pre-compression of concrete
occur simultaneously .
4.Seating of wedges
After tensioning is done, they
will put on the wedges to hold
the tendons whereby the extra
length of tendons.
5. Cutting of tendons
Tendon tails will be cut off using
either oxyacetylene touch ,
hydraulic shear, plasma cutter,
abrasive wheel.
1. Placing of ducts
The ducts for the
tendons are placed
along with the
reinforcement before
the casting of concrete. Placing
of
tendons

Materials Savings
Increase in
Performance
Flexible in design
Quicker
Construction
Reduce lifetime
cost
Durable / Strong

Accuracy
Poor workmanship
lead to accidents
Complexity of
work
Corrosion

Honeycomb in
Concrete
Cracking WedgesSplicing of tendons

A glance of the project
Project Name: Morocco Mall
Project Value: US$253 million
Size: 165 000 𝑚2
Location: Casablanca, Africa
Timeline: Mid 2008 – October 2011
Large amounts of concrete were to
be used in the construction, which
would necessitate a large number
of expansion joints, and a large
numbers of precast slabs were to
be manufactured, at odds with the
tight construction timeless of
project.
CHALLENGE
SOLUTION
Replace the reinforced concrete
floor slabs and the precast panels
with post tensioned wall.

Real Life Projects ( Oversea)
Process
1. Construction Site 2. Anchor Assembly 3. Stressing the strand 4. Grouting

Real Life Projects (Local)
A glance at the project
Project Name: Klang Valley MRTV7
Project Value: RM800 million
Location: Kuala Lumpur, Malaysia
Developer: SPAD
 Comprise supply and installation of the external
post tension tendons to the erected segmental
boxed girders by using a 15.2 m multi-strand
system.
 HDPE smooth round ducts are used to house
tendons comprising of 19 strands each for piers
spanning from 30.00 to 39.50 Metres.
 Multi-strand tendons are then stressed with a
hydraulic jack that applies forces equivalent of
up to 400 tonnes.
The project comprises :

Thank You

Final ct aa slides

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Final ct aa slides