This presentation defines the construction of prestressed concrete structures

2. Title :
Presented by: Major Adviser:
HARPREET KAUR Dr. Jaspal Singh
L-2015- AE- 187 M -Tech Prof. cum Head

4.  Management functions of construction comprises of some
following activities
1. Tendering and winning the contract
2. Contract negotiations
3. Mobilizing the financial resources for the work
4. Maintaining proper accounts
5. Work planning
6. Work supervision
7. Project control and monitoring
8. Maintenance of good labour relation
9. Completion of the work

5. Mainly following two methods are widely used in ‘
PROJECT MANAGEMENT’
1.CPM- (Critical Path Method)
2.PERT-(Project Evaluation And Review Technique)

6.  This method of const. first developed in
western Europe particularly in France &
Germany during 1950’s.
 Over 70 bridges of this type under const.
during 1971-75 in France.
 In India during 1960-61,@ 250m long Barak
bridge was constructed.

7.  There are the two basic materials for the construction
of prestressed concrete structures
1. High-strength concrete
2. High-tensile steel

8. According to Indian standard code IS:1343
1. The minimum grade for post tensioning is M-30.
2. The minimum grade for pretensioning is M-40.
Recent advances in concrete technology include the
development of
1.Rheodynamic concrete
2.High performance concrete
3.Nano concrete
4.Ultra high strength concrete
….are suitable for prestressed concrete structures.

9. These joints are necessary due to following reasons ….
1. Thermal contraction and expansion in structure
2. Shrinkage of concrete
3. Creep or inelastic deformation of structure
4. Elastic shortening under prestress
5. Displacement of the structure under load or any
other action

11. Construction techniques includes the following….
1.General aspects
2.Cantilever construction
3.Choice of spans and the method of construction
4.Prestressing cables
5.Epoxy bonding of precast segmental box girders
6.Innovative construction techniques

12. 1. Rapid developments in construction
techniques.
2. Advances in materials of construction.
3. Prestressed concrete is ideally suited for
large spans, its application is much less for
substructures than for superstructures.

13. This method …
1. Eliminates the use of expensive formwork
2. Scaffolding
Especially for bridges in deep valleys and
rivers with large depth of water.
It is mainly includes following two methods
1. Cast insitu construction.
2. Construction using precast segment.

14.  In this method bridge is cast in situ with
section 3 to 6 m long, cantilevering on both
sides of pier.
 Formwork is cast by steel frame work
 The operations of this method are as follows
1. Fabrication and shuttering
2. Placing of reinforcement and duct tubes for
high tensile cables
3. Concentering
4. Curing of concrete

15. 1. Threading ,anchoring and grounting of the
cables.
2. Releasing the formwork and moving on to
next section.
Prestress can be applied only after the
concrete developed the desired strength
after one week.
For e.g. the Bessein creek bridge by Gammon
India company at Bombay

16.  This method is used for the long bridges. It
is economical when there is large no of span.
This method involves the following steps.
 Casting of Precast segments in casting yard.
 Transporting the precast segments at the
site.
 Erection of the precast segment using
launcher or crane.
 External Prestressing.
 Grouting.

18.  A Segmental Bridge is a bridge built in short
sections (called segments), that is one piece
at a time. And then segments are erected to
make the bridge. The bridge is either cast-in-
place or precast.

19.  It is economical for large project, due to
investment req. for casting, handling &
erection of precast segments.
 The construction of a flyover in an urban
environment is not always welcomed by the
society because of traffic disturbance &
construction delays, nuisance caused during
concreting & erecting the formwork at site and
noise & visual pollution.

21. Selection of method of construction is mainly
based on following
1. Size of the bridge
2. Length of the span
3. Precasting facilities available at site
4. Equipments available
 Cantilever method is used in range of 50 to
200 m .
 For small spans of less than 50 m ,precast
segmental method is preferred

22.  The following points are important for
cantilever construction technique
1. After erection of each modular section
cables should be threaded into the ducts.
2. The voids must be enough large for proper
grouting.
3. The commonly used cables comprise 12
wires of 13 dia. And 12wires of 8mm
diameter cables (Freyssient system).

24.  Following re the techniques used for the
construction of prestressed concrete bridges
are listed below……
1. The staging method
2. Incremental launching or push out technique
3. Progressive placement construction method
4. Cantilever construction method

25.  This technique is adopted when
1. Low clearance is required below the deck
2. Supporting formwork does not interface with the traffic
This method facilitates rapid construction by maintaining
correct geometry of the structure with low cost.
This technique has been used in the construction of Rhine river
at Maxau,Japan

27. 1. Segments of the Bridge superstructure are cast
at site in length of 10 to 30 m in stationary
forms located behind the abutment.
2. Each unit is cast directly against the previous
unit.
3. After the concrete attains the desired strength,
the new unit is joined to the previous unit by
post tensioning.
4. The assembly of units is pushed forward in
stepwise for casting and succeeding segments

29.  In this case construction starts at one end of
the structure and proceeds continuously to
the other end (cantilever end)
1. This method have found to be practicable
and economical in range of 30 to 90 m.
2. This method has been used for ‘Linn cove
viaduct in north Carolina’ USA .

31. Basic information related to ‘ Linn cove
viaduct in north Carolina’USA.
1. Total length1,243 feet (379 m)
2. Width39.5 feet (12.0 m)
3. Construction begin1979
4. Construction end1987

32.  During the last decades, construction
techniques developed have shown major
progress towards simplification.
 The collective experience and knowledge
gained through research and practice during
the last fifty years will help in involving
innovative applications in the construction of
prestressed concrete structures

33. 1. N Krishna raju Prestressed concrete
,Tata McGraw –Hill publishing Co.
Ltd, New Delhi,2007,pp 715-729
2. Internet