1. Cable-Stayed Bridges
-JIGAR .S.SHAH(CP1712)
-ADNAN SHAIKH(CP1812)
-MEGHA SINGH(CP1912)

2. DIFFERENCE BETWEEN CABLE STAYED
BRIDGE AND CABLE SUSPENSION BRIDGE
 A multiple-tower cable-stayed bridge may appear similar to
a suspension bridge, but in fact is very different in principle and in
the method of construction.
 In the suspension bridge, a large cable hangs between two towers,
and is fastened at each end to anchorages in the ground or to a
massive structure.
 These cables form the primary load-bearing structure for the bridge
deck. Before the deck is installed, the cables are under tension from
only their own weight.
 Smaller cables or rods are then suspended from the main cable, and
used to support the load of the bridge deck, which is lifted in
sections and attached to the suspender cables.
 The tension on the cables must be transferred to the earth by the
anchorages, which are sometimes difficult to construct owing to
poor soil conditions.

3. ADVANTAGES OF CABLE STAYED BRIDGES
 much greater stiffness than the suspension bridge, so that
deformations of the deck under live loads are reduced
 can be constructed by cantilevering out from the tower -
the cables act both as temporary and permanent supports
to the bridge deck
 for a symmetrical bridge (i.e. spans on either side of the
tower are the same), the horizontal forces balance and
large ground anchorages are not required.

4. INTRODUCTION
 A cable-stayed bridge, one of the most modern bridges,
consists of a continuous strong beam (girder) with one or
more pillars or towers in the middle
 Cables stretch diagonally between these pillars or towers
and the beam .These cables support the beam
 The cables are anchored in the tower rather than at the
end

5. LOAD TRANSMISSION
slab
Tension
Cables
pylons
Pile cap Compression
piles
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soil

6. COMPONENTS OF CABLE STAYED BRIDGE
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7. CLASSIFICATIONS
 Based on arrangements of the cables
• Radiating
• Harp
• Fan
• star
 Based on the shape of pylon
• A-type
• H-type
• Y-type
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8. CLASSIFICATIONS
radial : cables connect evenly throughout the deck, but all
converge on the top of the pier
harp : cables are parallel, and evenly spaced along the
deck and the pier
fan : a combination of radial and harp types
star-shaped : cables are connected to two opposite
points on the pier

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SHAPES OF PYLON

10. CABLE
 A cable may be composed of one or more structural ropes,
structural strands, locked coil strands or parallel wire strands.
 A strand is an assembly of wires formed helically around centre
wire in one or more symmetrical layers.
 A strand can be used either as an individual load-carrying member,
where radius or curvature is not a major requirement, or as a
component in the manufacture of the structural rope.
 A rope is composed of a plurality of strands helically laid around a
core. In contrast to the strand, a rope provides increased curvature
capability and is used where curvature of the cable becomes an
important consideration.
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11. TYPES OF CABLE
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12. Cables are made of high-strength steel, usually encased in a
plastic or steel covering that is filled with grout , a fine grained
form of concrete, for protection against corrosion.

13. SELECTION OF CABLE CONFIGURATION
 The selection of cable configuration and number of
cables is dependent mainly on length of the span, type of
loadings, number of roadway lanes, height of towers, and
the designer’s individual sense of proportion and
aesthetics.
 Cost also plays important role in deciding the selection.
 Using less number of cables increases concentrated load
at a single point thereby requiring additional
reinforcement for the deck slab as well as pylon .
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14. POSITIONS OF THE CABLES IN SPACE
 Two plane system
 Two Vertical Planes System
 Two Inclined Planes System
 The Single Plane System
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15. Two Vertical Planes System
 In this type of system there are two parallel sets of cables and the tower
on the either sides of the bridge, which lie in the same vertical plane.
1. The cable anchorages may be situated outside the deck structure,
which is better than the other in terms of space as no deck area of
the deck surface is obstructed by the presence of the cables and the
towers.
2. but this requires substantial cantilevers to be constructed in order
to transfer the shear and the bending moment into the deck
structure.
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16.  When the cables and tower lie within the cross-section of the
bridge, the area taken up cannot be utilized as a part of the
roadway and may be only partly used for the sidewalk. Thus as
area of the deck surface is made non-effective and has to be
compensated for by increasing overall width of the deck.
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17. TWO INCLINED PLANES SYSTEM
 In this system the cables run from the edges of the bridge deck to a
point above the centreline of the bridge on an A-shaped tower or λ-
shaped or diamond shaped pylon.
 This arrangement can be recommended for very long spans where the
tower has to be very high and needs the lateral stiffness given by the
triangle and the frame junction.
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18. THE SINGLE PLANE SYSTEM
 This type of system consists of bridges with only one vertical
plane of stay cables along the middle longitudinal axis of the
superstructure
 As the cables are located in a single centre vertical strip thus all
the space is utilized by the traffic.
 This system also creates a lane separation as a natural
continuation of the highway approaches to the bridge.
 longitudinal arrangements of the cables used with two planes
bridges are also applied to single centre girder bridges.
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19. CASE STUDY:
BANDRA WORLI SEA LINK

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22. BRIDGE DETAILS:
 LENGTH OF SEA LINK: 5600 m
 LENGTH OF CABLE STAY PORTION: 600 m
 HEIGHT OF PYLON/TOWER : 123 m
 NO. OF PIERS : 620
 LONGEST SPAN : 2x250 m
 LOCATION : A CLOVERLEAF INTERCHANGE AT MAHIM
INTERSECTION AND A FLYOVER AT THE LOVEGROVE
INTERSECTION HAVE BEEN PROPOSED AS PART OF THIS
PROJECT TO ENHANCE THE FASTER AND SAFE TRAFFIC
DISPERSAL.
 CLIENT : MSRDC
 MAIN CONTRACTOR : HCC
 TOTAL PROJECT COST : Rs 850 CRORE
 SCHEDULED INITIALIZATION & COMPLETION:
MAY, 1999 & MAY, 2002
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 ACTUAL COMPLETION : AUGUST, 2009
 AMOUNT OF CONC. USED : 0.2 million cum.

23. SUB SURFACE EXPLORATION
 INITIAL GEOTECHNICAL INVESTIGATION

 25 BORE HOLES
 ALONG THE LENGTH
 TO OBTAIN THE SOIL
 PROFILE.
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24. SUB STRUCTURE CONSTRUCTION
 PILING:
 TYPE OF PILES : COMBINED END EARING AND
FRICTION PILES
 DIA OF PILES USED : 1.5 – 2 m
 DEPTH OF PILES : 5.15 – 663.4 m
 PILE GROUP UNDER THE PYLON : 40 NOS.
 CONST. TYPE : BORED CAST IN SITU
 TECHNOLOGY USED : REVERSE CIRCULATION
DRILL
 SUPPORT STRUCTURES : COFFERDAM & SHEET
PILING
 PILE CAP THK – 3.5 m
 CONCRETE USED – M60, HPC
 PIER LENGTH – 4-6 m DEPENDING UPON THE 24
GRADIENT OF BED

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26. COFFER DAM CONSTRUCTION
 A TEMPORARY WATER
TIGHT STRUCTURE TO
FACILITATE CONST. OF
PROJECT WHICH ARE
SUBMERGED IN WATER.
 IT CONSIST OF CASINGS OF
1.5 m DIA AND SHEET PILES
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27. PILING
 ONCE THE COFFER DAM IS
CONSTRUCTED, WATER IS
PUMPED OUT .
 DEWATERING TECHNIQUE
ADOPTED WAS WELL
POINT SYSTEM.
 PILING TECHNIQUE USED
WAS REVERSE
CIRCULATION DRILL.
 IN THIS METHOD, PRECAST
SEGMENT IS PLACED ON
SOIL & DRILLING IS DONE
WITH DRILL BIT
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28. RCD DRILL BIT
 DRILL BIT CONSISTS OF
PNEUMATIC PISTON
 DEPTH ACHIEVABLE : 500
m
 BIT DIA : 13 – 20 cm
 MATERIAL : TUNGSTEN
STEEL
 OUTPUT : 900 – 1150 cfm
 @ 350
RPM
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32.  PYLON CONSTRUCTION
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33. LOWER PLYON CONSTRUCTION
LOWER PYLON CONSISTS OF :
1. PIER TABLE
2. LOWER PIER LEGS
CONST. METHOD USED :
SELF CLIMBING FORM
CONST.
CONST. IS DONE IN LIFTS.
6 LIFTS REQUIRED FOR
CONST OF LOWER PYLON.
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35. UPPER PYLON
WHILE CONSTRUCTING
THE UPPER TOWER LEG,
THE CARE WAS TO BE
TAKEN THAT THE
REINFOCEMENT
DOESNOT FALL DUE TO
ITS SELF WEIGHT, THAT IS
WHY EMBEDDED TUBES
WERE FIT IN JUMP FORM
TO PROVIDE EXTRA
SUPPORT IN LEGS.
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41. CABLE STAYED BRIDGE
SUPERSTRUCTURE
CONSTRUCTION
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42. SUPERSTRUCTURE CONSTRUCTION
 Precast Segmental Construction involving
 Match Casting
 Span by Span Erection for approach spans
 Parameters for segment casting
 Alignment of the individual span to which segment
belong.
 Precamber necessary to take care of deformations of
the girder due to self weight, prestress and other
permanent loads.
 Necessary corrections for errors in the casting of
adjacent segment cast earlier, while match casting. 42

43. CASTING YARD
PLAN of Casting Yard 43

44. CASTING YARD
 Total number of segments – 2500 & more.
 Three types of segment
 Approach Span Segment
 Main Cable stayed segment
 Segment on Piers
 Size of Approach Segment –18.1m x 3.2m x 3.0m
 Size of Main Cable Stay Segment – 20.8m x 3.2m x 3m
 Weight of each Segment – 150 tonnes
 Total length of Casting Yard- 350m
 Capacity – 300 segments at a time
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Segments placed in Casting Yard

46. ERECTION OF SEGMENTS
 The Erection Gantry does the erection of span.
 A typical 50m span comprises of 15 numbers of
precast segments
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47.  The segments are transported to the site with the help of
barges.
 Each segment is lifted and all the segments in a single
span are aligned together and brought about at the same
level.
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48.  At the time of match casting High Tensile Steel Rods are
passed through the ducts provided in the segments and
tightened with the help of a Winch machine.
 Neutobond BC solution is used so that the two segments
can be aligned together.
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49. I
Asian Hercules used to displace Erection Gantry
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50. ERECTION OF STAY CABLES

51.  The cable - stayed portion is 600 meters in overall length.
 It consists of two 250 meters cable supported main spans flanked by 50
meters conventional approach spans.
 A centre tower with an overall height of 128 meters above pile cap
level supports the superstructure by means of four planes of stay cables
in a semi - fan arrangement.
 Cable spacing is 6.0 meters along the bridge deck and are tied up to
every alternate girder.
 Big tower -264 stay cables
Length- Min- 85m
Max- 250m
 Small tower -160 stay cables
Length- Min- 30m
Max- 80m
 In each there are approx. 135
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strands stressed with the help
of a hydraulic jack.

52. DESCRIPTION OF SHAPES
Triangles are one of the In this bridge, the distance
shapes used by the attachment of the cable up the tower
of the cables and the beam – is equal to the distance
this shape is used because of from the tower to
its ability to transfer the tension connection point on the
as the moving load goes across beam and is a 90 degree
the bridge angle
A rectangle is
Triangulated bracing between the attached at the
cables reduces the amplitude of convergence
oscillations point of the
beam and tower
for stability

53. CONTINUITY PT AND GROUTING
 Once the Deck is complete Post Tensioning of all the
segments is done so as to bring them to a specific
predetermined geometry.
 The grouting of the bridge includes a major task of fill up
the space left in the holes for the PT cables.

54. CABLE FORCE ADJUSTMENT AND FINE
TUNING
 Iterative process
 Last stage
 Rechecking of tension forces in each cable so as to
confirm that it equals the forces.
 1 to 2% of variation.

55. BENEFITS OF BANDRA-WORLI SEA LINK
1) It is estimated that the sea link will help saving Rs. 10
million annually due to congestion in traffic and length
of the previous route and shorter new route.
2) While earlier it used to take 40 minutes for drive
between Bandra and Worli, now the distance can be
covered in mere 8 minutes resulting in large savings in
time.
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