This ppt give you idea about basic prestressing work.

1. PRESTRESSED CONCRETE
AND ITS USES
SITE VISIT
GROUP PRESENTATION BY SUDHANVA SATHE &TEAM

2. CONTENT
 INTRODUCTION
 PRINCIPLE OF PRESTRESSING
 COMPARISION BETWEEN R.C.C. AND P.S.C
 METHODS OF PRESTRESSING
 PRE-TENSIONING
 POST-TENSIONING
 PRESTRESSED CONCRETE STRUCTURE.
 LOSSES
 ADVANTAGES
 DISADVANTAGE
 CONCLUSION
 REFERENCE

3. INTRODUCTION
 Prestressed concrete is method for
overcoming natural weakness in
tension .It can be used to produce
beams floors or bridges with a longer
span than is practical with ordinary
reinforced concrete .It is often to use
in commercial and residential
construction as a beam and slab

4. PRINCIPLE OF PRESTRESSED
 The principle behind Prestressed concrete is that
compressive stresses induced by high strength steel
tendons in a concrete member before loads are applied
will balance the tensile stresses imposed in the member
during services.
 Prestressed concrete is basically concrete in which internal
stresses of a suitable magnitude and distribution are
introduced so that the stresses resulting from the external
loads are counteracted to a desired degree.

5. Comparison between R.C.C. and P.S.C.:-
R.C.C P.S.C.
1)30%-40% of total cross section is
used.
1)100% cross section is used.
2)Economical upto 12m 2)Economical from 12-30m
3)Self weight of section is more. 3)Self weight of section is less.
4)Cracking and corrosion problems
are more.
4)No cracking or corrosion
problem.
5)Reinforcement is straight. 5)Tendons can be bent or parabolic.
6)Tension is developed below
neutral axis.
6)Whole cross section is in
compression.
7)Stresses develop after loading. 7)Stresses develop before loading.

8. METHODS OF PRESTRESSING
Prestressing system basically classified in two types …..
1)Pre-tensioning
2)Post-tensioning

9. PRE-TENSIONING
 Pre-tensioning is a method where
prestressing steels are prestressed,prior
to concreting against two rigid
abutments .This method is most widely
use for mass production of short span
structures, where prestressing is also a
prerequisite, such as railway slippers,
electric poles, fencing poles,
pretensioned slab and I-section bridge
gurders etc.

10. PRESTRESSED CONCRETE MEMBER

11. POST-TENSIONING
 Post-tensioning is method where prestressing steels are stressed
after concrete attains its preliminary strength. Two extreme ends
of the structures are considered as a reaction face, against which
force is applied. Ducts are placed inside the formwork along with
reinforcement and the concreting is completed. After achieving
required concrete strength, stipulated
numbers of prestrssing steel is then inserted in each duct for
stressing purpose. After achieving elongation
and stresses they are blocked at two ends with the help of anchor
plates and grip.

12. CONSTRUCION PROCESS OF POST-TENSIONED CONCRETE

13. POST-TENSIONED MEMBER

14. PRESTRESSED CONCRETE
STRUCURE
Nowadays nearly all
construction
components are available
in the prestressed form.
Such as
1)Beams
2)Girders
3)Bridge deck
4)Slabs
5)Columns
6)Piers

15. PRESTRESSED CONCRETE MEMBERS IN BUILDING

16. PRESTRESSED CONCRETE MEMBER IN THE CONSTRUCTION
OB BRIDGES AND FLYOVERS

17. ADAM VIADUCT
This is one of the first
prestressed bridge.Itt is
situated in WALGATE
,UK.
It is a concrete railway
bridge.
Total length=37m
Width= 9.07m
Year= 1946
No. of spans=4

27. ADVANTAGES OF
PRESTRESSED STRUCTURE
• The size or dimensions of structural members are reduced, which may increase the
clearances or reduce storey heights.
• It permits the use of large spans (greater than 30 m) with shallow members, even when
heavy load are encountered.
• In addition to general advantages, such as excellent fire resistance, low maintenance costs,
elegance, high corrosion-resistance, adaptability etc, the prestressed concrete is found to
sustain the effects of impact or shock and vibrations.
• Because of smaller loads due to smaller dimensions being used, there is considerable saving
cost of supporting members and foundations.
• The prestressing technique has eliminated the weakness of concrete in tension and hence
crack free members of structure are obtained.
• Because of better material (i.e. controlled concrete and high tension steel) being used and
nullifying the effect of dead loads, smaller deflections are caused.

28. DISADVANTAGES
• The unit cost of high strength materials being used is
higher.
• Extra initial cost is incurred due to use of
prestressing equipment and its installation.
• Extra labour cost for prestressing is also there.
• Prestressing is uneconomical for short spans and
light loads

29. CONCLUSION
 This Technical Seminar program was an excellent
opportunity to get to the knowledge of particular a topic
and experience the things that we would have never
gained through going straight into a job. I am very much
grateful to my college for giving us this wonderful
opportunity.
 I have learnt various concept of prestressed concrete and
its applications.
 Future scope of it is very large and it will surely help to
build a world with safe use of concrete.

30. REFERENCES
Websites
• www.civilinfo.com
• www.quora.com
• www.wikipedia.com
•
Books
• NEW TECHNIQUES IN CIVIL STRUCTURES
• PRESTRESSED CONCRETE
• DESIGN OF CONCRETE STRUCTURES
• REINFORCEMENT AND PRESTRESSED CONCRETE

31. THANK YOU