CT3 Group Assignment Report

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CONTENTS
NO. CONTENT PAGE
1. 1.1INTRODUCTION TO POST-TENSIONED
1.2 TYPICAL APPLICATIONS OF POST TENSIONING
1.3 TYPES OF POST TENSIONING
1.3.1 BONDED POST-TENSIONING
1.3.2 UNBONDED POST-TENSIONING
2-5
2. 2.0 ADVANTAGES AND DISADVANTAGES OF POST-
TENSIONING
6
3. 3.0 MANUFACTURING PROCESS OF POST-TENSIONING 7
4. 4.0 PROBLEMS & SOLUTIONS IN POST TENSIONING
STRUCTURAL ELEMENT
8
6. 5.0 REAL LIFE PROJECT [LOCAL & OVERSEA]
5.1 Morocco Mall ,Africa
5.2 Klang Valley, Malaysia
9-11
7. 6.0 REFERENCES 12

2
1.1 POST-TENSIONED
Post-tensioning is simply a method of producing prestressed concrete,masonry,and
other structural elements. The term prestressing is used to describe the process of
introducing internal forces (or stress) into a concrete ormasonryelementduring the
construction process in orderto counteractthe external loads applied when the structure
is put into use (known as service loads).These internal forces are applied by tensioning
high-strength steel, which can be done either before or after the concrete is placed.
When the steel is tensioned after concrete placement, the process is called post-
tensioning.
Post-tensioned means that the concrete is poured and then the tension is applied-butit
is still stressed before the loads are applied so it is still prestressed.Post-tensioned
concrete which is also called as “active reinforcement“, with the primary function to
place concrete structure undercompression in regions where loads causes tensile
stress. Post-tensioning applies compressive stresses on the material, balancing off
tensile stress on the concrete. The tension is applied by the use of a tensioning member
known as “tendons”.
It is a technique for reinforcing concrete. Post-tensioning tendons,which are
prestressing steel cables inside plastic ducts or sleeves,are positioned in the forms
before the concrete is placed.Afterwards, once the concrete has gained strength but
before the service loads are applied,the cables are pulled tight, or tensioned,and
anchored againstthe outer edges of the concrete.
The use of post-tensioning contributes to very demanding geometryrequirements,
including complex shapes andcurvature and variable superelevation.It allows long clear
spans and this result in aestheicaland architectural approach.Also,it would be column-
free and creates more space.In addition, it allows thinner concrete sections, stiffer walls
resisting lateral loads,and stiffer foundations.
Additionally, all construction joints and crack control joints could be eliminated because
the slab was poured monolithically (in one whole single piece)and the post-tensioning
system could provide sufficient pre-compression on the slab.
Tendo
ns
Photo Source : https://static.concretenetwork.com/photo-gallery/images/550x412Exact_0x4/site_26/concretenetwork-com_12578.jpg

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1.2 TYPICAL APPLICATIONS OF POST TENSIONING
- Suspended slabs like floor slabs and terrace slabs
- Foundation slabs (rafts)
- Slabs on grade (office buildings,multistorey car parks,warehousesetc.)
- Cantilevered structures, such as overhanging building parts.
- Facade elements oflarge area;here light post-tensioning is a simple method of
preventing cracks.
- Main beams in the form of beams,transfer girders,lattice girders or north-light roofs.
1.3 TYPES OF POST TENSIONING
There are mainly (2) types of posttensioning system, bonded orunbonded.
 Bonded -The prestressing steel is installed at the site after the formwork is
erected and typically after concrete is poured.It is housed in a sheating or ductto
preventit from bonding to the surrounding concrete.After the concrete has
hardenered orcured,the prestressing steel is gripped at both ends and then
pulled and anchored to prestress the concrete.The ductwould then be filled with
cementitious grout.
 3 main purposes : protecttendons againstcorrosion,permanently
“ lock-in” the tendon pre-tension ( thereby removing the long-term
reliance upon the end-anchorage systems),improve certain structural
behaviorof the final concrete structure
 Unbonded -It differs by providing each individualcable permanentfreedom of
movement relative to concrete.By so, each individual tendon is coated with a
grease (generallyuse lithium-base)and covered by a plastic sheating formed in
an extrusion process.The transfer of tension to concrete is achieved by the steel
cable acting againststeel anchors embdded in the perimeter of the structural
element.
Single Strand
POST
TENSIONING
a. B o nd e d P o st -
b. Unbonded Post- Tensioning
Single Strand
Multi Strand Flat Duct
Multi Strands Round Duct

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1.3.1 Bonded Post-Tensioning
BONDED POST-TENSIONING UNBONDED POST-TENSIONING
Develops higher flexural strength Provides greater available level arm
Does notdepend 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
End
Cap
Grout
Valve
Pocket
Former
Strands
Examples:
Photo Source: http://pt-structures.com/wp-content/uploads/2010/08/10-
Steps_PT_Floor_Design_US_version1.pdf
[Flat Duct] [Round Duct]
Grout Pipe
Wedges
Strands
Anchor
Head
BearingPlate
Duct
Photo Source: http://ptsindia.net/pt-system.html

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1.3.2 Unbonded Post- Tensioning
Single Strand
Floor System Reinforced with Grouted
Post-Tensioning System
Post- Tensioned MatFoundation
Using grouted Tendons
Flat Duct
KSA, Photo Source: http://pt-structures.com/wp-content/uploads/2010/08/10-
Photo Source: https://lh3.googleusercontent.com/1TjXhdpEiQKGVCeuIpMKZ9DkfOqLi9QyAFQ5GdmOuG9f8CVl2dz-
tN2KughnoLUM6rRCaQ=s160
Photo Source:
https://lh3.googleusercontent.com/x9OONHF854Tjd7z1oDB9rKJbxqXncS5KQJSVXlxzyGICELIpggq
UuBH_qrSgbPgBnF7BVGw=s113

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2.0 ADVANTAGES AND DISADVANTAGES OF POST-
TENSIONING
ADVANTAGES DISADVANTAGES
MaterialSavings
- Decreased dead load reduces rebar
(60%-75%) and concrete (20%) in
columns and foundation
Accuracy
- Placementof tendon profiles has to be
accurate
Quicker Construction
- Potential pourcycle of 3-4 days
- Reducing re-shoring requirements
Corrosion
- Since there are a numberoftendons
and
Stressing
Jack
Tendon Tail
(Additional lengthwill be cutoff)
Wedges
Stressing
Anchor
Split Pocket Former with
Intermediate AnchorPocket
Former
Anchorage
Assembly
Photo Source: http://www.amsyscoinc.com/2010/09/14/diagram-of-post-tensioning-slab/
Example of a Floor System using
the Unbonded Post-tensioning
System
Fortaleza, Brazil.
MAT FOUNDATION USING
UNBONDED TENDONS
Steps_PT_Floor_Design_US_version1.p
FloorSystem
Reinforcedwith
GroutedPost-
TensioningSystem

7
wire spread inside the posttension slab,
corrosion mayoccur.Tendencyof
corrode depends on the quality of the
material
Increased Performance
- Improve seismic performance and
reduced deflection and vibration
- Improved crack control and
waterproofing
properties
Complexity ofwork
- Post tension can be made only by skilful
professionals.
Reduced Lifetime Costs
- Loweroverall maintenance and lifecycle
costs of the structure
- Reduced building heightalso results in
energysavings,
Poor workmanship leads to accidents
- Main problem ofusing post tension is
that if care is nottaken while making it,
it can lead to future mishaps.If gaps of
tendons and wiring, corrosion mayoccur
which will lead to some untoward events.
Flexible in design
- Designs made are sleek,requires lesser
space and give way to dynamic
contours.
Durability
- Lasts longer,strong substitude of the
normalconcrete
Stronger/More Efficient
- Less concrete and steel are needed for
the same structural capacity that might
form tight.
- Prevents entry of insects and reducing
possible water penetration which can
damage flooring and cause mold
problems
3.0 CONSTRUCTION PROCESS OF POST-TENSIONING SLAB
[Bonded+Unbonded]

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5. After anchoring a tendon atone end,the
tension is applied at the other end by a
jack. The tensioning of tendons and pre-
compression ofconcrete occur
simultaneously. A system of self-
equilibrating forces develops after the
stretching ofthe tendons.
BONDED POST-TENSIONING UNONDED POST-TENSIONING
Placing ofducts in the reinforcement
1. The ducts for the tendons are placed along with the reinforcement before the casting of concrete. The duct S
are used to prevent contactbetween concrete and the tendons during the tensioning operation. The tendons
are placed in the ducts after the casting ofconcrete.
Casting ofconcrete
1. Concrete is casted and must achieve proper strength before the tendons are tensioned. This is typically 75% of
the concrete's 28-day design strength, and is specified in the projectdocuments.
Grouting the duct
2. Bonded post-tensioning - If the ducts are filled with
grout. The grout is a neat cementpaste or a sand-
cementmortar containing suitable admixture.
The ductis notgrouted
4. Unbonded post-tensioning - Ducts not
grouted and tendon is held by the end
anchorages. The profile ofthe duct depends
on the supportconditions. For a simply
supported member, the ducthas a sagging
profile between the ends. For a continuous
member, the ductsags in the span and hogs
over the support.
Photo Source:https://www.vsl.net/what-post-tensioning
Jacking oftendon
5. After anchoring a tendon at one end, the tension is
applied at the other end by a jack .The tensioning of
tendons and pre-compression ofconcrete occur
simultaneously. A system pfself-equilibrating forces
develops after the stretching oftendons.
Putting on wedges and cut off tendon tail
6. After tensioning is done, they will puton the wedges to
hold the tendons whereby the extra length of tendons,
tendon tails will be cutoff using either oxyacetylene
touch , hydraulic shear, plasma cutter, or abrasive wheel.

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4.0 PROBLEMS & SOLUTIONS IN POST TENSIONING STRUCTURAL
ELEMENT
Honeycomb in Concrete
Solution: Patching with non-shrink concrete groutmix with an epoxy binder. Grout
strength should equal or exceed specified concrete strength. Do notuse grouts that
contains calcium chloride or other materials containing chloride and whenever patch
has attained proper strength, stressing process may proceed.
Splicing of Tendons
Solution: Tendons are sometimes too shortto reach an edge because of
misplacementor misfabrication. Thus, making tendon couplers are necessary, the
engineer ofrecord and the post-tensioning material supplier should be notified. The
coupler location should be determined by post-tensioning material supplier in such
that the coupler is centered in the member and nota pointof tendon curvature.
Cracking Wedges
Solution: Hairline cracks may appear in the case-hardened surface ofwedges due
to deformation ofthe wedges around the strand at the time of seating. These cracks
do notaffect the integrity of posttensioning system.
Photo Source :
https://lh3.googleusercontent.com/aotgRs0GAdyNUI9
AK5J_HVwG3r35me5yjy8-
PxBMqnOqwMWuWhM9xOthy6gXMr_h84Z2aA=s85
Photo Source :
https://lh3.googleusercontent.com/cHpL8k76
bpBOUhc3Nt3mUt508ADvWHYzNnQLG908Gr
hSZIH4e93weyMk0S1OAfusio37MSI=s90
Photo Source :
https://lh3.googleusercontent.com/A6LxuPDQ1Y0QRnAF
FYGhdPfCKb-
0jyukxWpRV5h38or6iitlyu0vF1EDIMWfp1vm0IArFg=s85

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5.0 REAL LIFE PROJECT [Overseas]
5.1Morocco Mall ,Africa
Introduction
Project The Morocco Mall
Location ofthe
project
City of Casablanca,Morocco
Cost Approximately US$253-million
Construction
company
SGTM Construction
Size of the project 165,000 m², 650m long structure
Timeline Mid of 2008 – October 2011
CHALLENGE
Large amounts of concrete were to be used in the construction, which would necessitate a large
Photo Source : https://i.ytimg.com/vi/XcS24xN6c0k/maxresdefault.jpgPhoto Source :
https://khamsat.hsoubcdn.com/images/services/755020/5385609b9e808442e509004c
9193ff2a.jpg

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number of expansion joints, and a large numbers ofprecastslabs were to be manufactured, at odds
with the tight construction timeless ofproject.
SOLUTION
Replace the reinforced concrete floor slabs and
the precast panels with posttensioned wal
Further challenges faced
Building would need to contain a large number
of expansion joints because the site is located
less than 20 m from the Atlantic Ocean and the
basementlevel is below sea level.Leaks would
therefore not only pose a major inconvenience,
but severely hamper progress.
Also, the parking garage at the base ofbuilding
contained too many supporting column which
severely reduced the number ofparking bays.
The building therefore need redesigned to
accommodate new solution.
Installation
1. Construction Site
2. Anchor Assembly
3. Stressing the
strand
The process being applied to the second floor ofthe
Morocco Mall in the earlier stages ofconstruction. (The
roofof the basementlevel)
The anchor assembly graphically depicted. During the
process, a tendon will have anchors on each end to
transmit the force into the structure. Longer tendons, as
used in the mall, also have intermediate anchors along
their length.
Tension is applied by using a hydraulic stressing jack
which bears against anchors embedded in the concrete,
pulling steel to a predetermined force or stress.
Photo Source :
https://lh3.googleusercontent.com/V2Uo7dfIloE9Dc8ZVubnUb4yD5vGDML86sRvTP5zDB
vZpgLPYcb7_KkkrByFGzqpr4AZ0w=s89
Photo Source :
https://lh3.googleusercontent.com/V2Uo7dfIloE9Dc8ZVubnUb4yD5vGDML86sRvTP5zDB
vZpgLPYcb7_KkkrByFGzqpr4AZ0w=s89
Photo Source : https://lh3.googleusercontent.com/nToIY1SVWS0OSsohns_n29V5nu4-
oDfQJx9eH72MUY8zAiEfb1B7z0xNfaFhJdgvqZlQKw=s152

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5.0 REAL LIFE PROJECT (Local)
5.2 Klang Valley, Malaysia
Introduction
PROJECT PROFILE
 Construction of rail-based public transportnetwork
 Light rail transit (LRT)
 Monorail
 KTM Komuter
 KLIA Express
 KLIA Transit System
 Aim : Form backbone ofpublic transportfor the Greater KL/ Klang Valley region
It compromise of:
 The external post tension tendons to the erected segmental boxed griders by using a
15.2 m multi-strand system
 HDPE smooth round ducts – house tendons comprising of19 strands each for piers
spanning of 30.00 – 39.50M
in length
 Multi strand tendons – stressed with a hydraulic jack that applies forces equivalentofup to
400 tonnes
Project Klang Valley MRTV 7
Location Kuala Lumpur, Malaysia
Developer GovernmentofMalaysia and Public Transport Commission (SPAD)
Builder Alloy MTD Construction Sdn Bhd.
Value RM 800 Million
Photo Source : https://lh3.googleusercontent.com/XKRKS2agu6gUCTJg_hqxdEoK2_rQ4BRlKup-TBI2F4b3KzzmoeknmxYnOVWdC4fApsb2JA=s148

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 Total projecthas 106 piers providing structural support
-Light rail frame – spanning 3.6km in length
- 900 tonnes ofposttension strand to be installed by StrongForce

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6.0 REFERENCES
Robert Sward, a. (2017).Prescribinga Bonded Post-tensioning System. STRUCTURAL TECHNOLOGIES
VSL. Retrieved 20 October 2017,from https://www.vsl.net/article/prescribing-bonded-post- tensioning-
system
Unbonded Monostrand Post-Tensioning.(2017).STRUCTURAL TECHNOLOGIES VSL. Retrieved 20
October 2017, from https://www.vsl.net/product/unbonded-monostrand-post-tensioning
Bonded Post Tensioning - noorps.com. (2017).Noorps.com. Retrieved 20 October 2017,from
http://noorps.com/page.php?6
BBR | What is post-tensioning?.(2017).Bbrnetwork.com. Retrieved 20 October 2017, from
http://www.bbrnetwork.com/technologies/what-is-pt.html
The problem with reinforced concrete. (2017).The Conversation.Retrieved 20 October 2017,
from http://theconversation.com/the-problem-with-reinforced-concrete-56078
Alkhrdaji, T. and Thomas, J. (2017). Structural Strengthening Using External Post-Tensioning Systems. [online]
STRUCTURAL. Available at: https://www.structural.net/article/structural-strengthening-using-external-
post-tensioning-systems
Author,N. (2017). Difference Between Pre-tensioning And Post-tensioning.[online] Daily Civil. Available at:
http://www.dailycivil.com/difference-pre-tensioning-post-tensioning/
Author,N. (2017). POST TENSION SERVICES INDIA PVT. LTD.. [online] Ptsindia.net. Available at:
http://ptsindia.net/pt-system.html
Author,N. (2017). Post-Tension Basics- How Post-Tensioned Slabs Are Built - The Concrete Network.[online]
Concretenetwork.com. Available at: https://www.concretenetwork.com/post-tension/basics.html
Author,N. (2017). What is Post-Tensioning.[online] STRUCTURAL TECHNOLOGIES VSL. Available at:
https://www.vsl.net/what-post-tensioning
Author,N. (2017). What is Post-Tensioning.[online] Available at:
https://buildersshow.com/Documents/course_handouts/Post-
Tensioned%20Concrete%20in%20Residential%20Construction.pdf
Bešta, J. (2017). Post-Tensioning - Post-tensioning system | VSL. [online] En.vsl.cz. Available at:
http://en.vsl.cz/post-tensioning/
Corven, J. and Moreton, A. (2017). Post-Tensioning Tendon Installation and Grouting Manual.[online]
Available at: https://www.fhwa.dot.gov/bridge/construction/pubs/hif13026.pdf
K Sengupta,D. and Menon, D. (2017). Post-tensioning Systems and Devices. [online] Available at:
http://ebooks.bharathuniv.ac.in/gdlc3/ThirdYear/SecondSem/Civil/Prestres sed%20Concrete%20Structures
/Notes/Post%20Tensioning%20Systems%20and%20Devices.pdf
Khosa, N. (2017). Cite a Website - Cite This For Me. [online] Amsyscoinc.com. Available at:
http://www.amsyscoinc.com/2010/09/14/diagram-of-post-tensioning-slab/
O Aalami, D. (2017). 10 - Step Design of Post-Tensioned Floors. [online] Available at: http://pt-
structures.com/wp-content/uploads/2010/08/10-Steps_PT_Floor_Design_US_version1.pdf
Rogers, J. (2017). Cite a Website - Cite This For Me. [online] Concreteconstruction.net.Available at:
http://www.concreteconstruction.net/how-to/construction/post-tensioned-slabs_o
Rogowsky, D. and Marti, P. (2017). DETAILING FOR POST-TENSIONED. [online] Available at:
https://www.ethz.ch/content/dam/ethz/special-interest/baug/ibk/concrete-and-bridge-design-
dam/lehre/masterstudium/Stahlbeton/Unterlagen/Detailing_for_post-tensioning.pdf

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