Cable-Stayed Bridge Design Analysis

ANALYSIS & DESIGN OF
CABLE STAYED
BRIDGE
Supervisor :
Dr /Maher Moustafa El-abd1

INTRODUCTION
 Cables stretch diagonally between these pillars or towers
and the beam .These cables support the beam
 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
 The cables are anchored in the tower rather than at the
end
2

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.
3

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. 4

COMPONENTS OF CABLE STAYED BRIDGE
5

LOAD TRANSMISSION
soil
piles
Pile cap
pylons
Cables
Deck
Tension
Compression
6

CLASSIFICATIONS
 Based on arrangements of the cables
• Radiating
• Harp
• Fan
• star
 Based on the shape of pylon
• A-type
• H-type
• Y-type
7

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
8

TYPES OF DECK
1. Twin I Girder
2. Truss girder
10

TYPES OF DECK
3. box girder
4. Orthotropic girder
11

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.
12

TYPES OF CABLE
13
PROPERTIES OF CABLES

14
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.

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 .
15

POSITIONS OF THE CABLES IN SPACE
 Two plane system
 Two Vertical Planes System
 Two Inclined Planes System
 The Single Plane System
16

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.
 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.
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.
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.
19

CABLE ANCHORAGE
20
 Anchorage at concrete

CABLE ANCHORAGE
 Anchorage at concrete
21

22
CABLE ANCHORAGE
 Anchorage at steel

23
CABLE ANCHORAGE

24
CABLE ANCHORAGE

25
CABLE ANCHORAGE

26
INSTALLATION OF CABLES ANCHORAGE
1. Unreeling on carriages
2. Connecting the tensioning rod
3. Pulling into anchorage
4. Fixing the anchorage at the tower head
5. Installation at girder
6. Cable tensioning
7. Final anchorage
8. Delivery of strands
9. Supply PE pipes
10. Scaffolding at tower head
11. Anchor heads at the tower
12. Aligning PE pipes on bridge deck
13. Fusion welding of PE pipes
14. PE pipe with lifting collar

27
1. Strand pulled through the stay pipe

28
2. Temporary connection of the stay pipe at tower

29
3. Deformations influencing cable lengths

30
4. Mono jack for stressing individual strands

31
5. Stressing of individual strands

32
6. Stay cable without deviator and anti-vandalism pipe

33
7. Protruding strands for re-stressing

34
8. Multi-strand jack for stressing complete cable

35
9. Stressing of complete cable

36
10. Power seating of the wedges

37
11. Dampers inside boots
and anti-vandalism pipes

38
12. Corrosion-protection paint and strand cap

FUNCTION OF BEARINGS
 Bridge bearings are used to transfer forces from the
superstructure to the substructure, allowing the following
types of movements of the superstructure:
 Translational movements; and
 Rotational movements
Until the middle of this century, the bearings used consisted
of following types:
 Pin
 Roller
 Rocker
 Metal sliding bearings
40

PIN BEARING
 A pin bearing is a type of fixed bearings that
accommodates rotations through the use of a steel
 Translational movements are not allowed.
 The pin at the top is composed of upper and lower
semicircularly recessed surfaces with a solid circular pin
placed between.
 Usually, there are caps at both ends of the pin to keep
the pin from sliding off the seats and to resist uplift loads
if required.
 The upper plate is connected to the sole plate by either
bolting or welding. The lower curved plate sits on the
masonry plate.
41

PIN BEARING
42
Steel Pin
• Rotational Movement is allowed
• Lateral and Translational Movements are Restricted

ROLLER TYPE BEARINGS
43
Multiple Roller BearingSingle Roller Bearing
o AASHTO requires that expansion rollers be equipped with “substantial
side bars” and be guided by gearing or other means to prevent lateral
movement, skewing, and creeping (AASHTO 10.29.3).
o A general drawback to this type of bearing is its tendency to collect dust
and debris.

ROCKER TYPE BEARING
44
• A rocker bearing is a type of expansion bearing that comes in a great
variety.
• It typically consists of a pin at the top that facilitates rotations, and a
curved surface at the bottom that accommodates the translational
movements
• Rocker and pin bearings are primarily used in steel bridges.

SLIDING BEARINGS
45
• A sliding bearing utilizes one plane
metal plate sliding against another
to accommodate translations.
• The sliding bearing surface
produces a frictional force that is
applied to the superstructure,
substructure, and the bearing
itself.
• To reduce this friction force, PTFE
(polytetrafluoroethylene) is often
used as a sliding lubricating
material. PTFE is sometimes
referred to as Teflon, named after
a widely used brand of PTFE

SLIDING BEARINGS
46
• Sliding Bearings be used alone
or more often used as a
component in other types of
bearings
• Pure sliding bearings can only
be used when the rotations
caused by the deflection at the
supports are negligible. They
are therefore limited to a span
length of 15 m or less by
ASHTTO [10.29.1.1]

KNUCKLE PINNED BEARING
47
• It is special form of Roller Bearing in which the
Knuckle pin is provided for easy rocking. A
knuckle pin is inserted between the top and
bottom casting. The top casting is attached to
the Bridge superstructure, while the bottom
casting rests on a series of rollers
• Knuckle pin bearing can accommodate large
movements and can accommodate sliding as
well as rotational movement

POT BEARINGS
 A POT BEARING consists of a shallow steel cylinder, or
pot, on a vertical axis with a neoprene disk which is
slightly thinner than the cylinder and fitted tightly inside.
 A steel piston fits inside the cylinder and bears on the
neoprene.
 Flat brass rings are used to seal the rubber between the
piston and the pot.
 The rubber behaves like a viscous fluid flowing as
rotation may occur.
 Since the bearing will not resist bending moments, it
must be provided with an even bridge seat.
49

LAMINATED ELASTOMERIC BEARINGS
51
Elastomeric material interspersed with steel
plates

LAMINATED ELASTOMERIC BEARINGS
52
o consist of a laminated
elastomeric bearing equipped
with a lead cylinder at the
center of the bearing.
o The function of the rubber-steel
laminated portion of the
bearing is to carry the weight of
the structure and provide post-
yield elasticity.
o The lead core is designed to
deform plastically, thereby
providing damping energy
dissipation.
o Lead rubber bearings are used
in seismically active areas
because of their performance
under earthquake loads.

SELECTION OF BEARING TYPE
ACCORDING TO AASHTO
53
Long Trans Long Trans Vert Long Trans Vert S L R U
L L S S L L L L 2 6 0 0 18
S S S S L L L L 4 4 0 0 20
U U U U U L L S 1 2 0 5 7
S S S S L L L S 5 3 0 0 21
S S U U S R R S 4 0 2 2 14
R R S S S R R S 4 0 4 0 16
R R U S U R R S 2 0 4 2 10
R R S S L S R S 4 1 3 0 17
R R S S U R R S 3 0 4 1 13
R R S S L S S S 5 1 2 0 19
S U U S U U R S 3 0 1 4 10
U U U S U S R S 3 0 1 4 10
S U U S U U R S 3 0 1 4 10
S U U U U U U S 2 0 0 6 6
Score Rank
Type of Bearing
S = suitable, U = unsuitable, L = suitable for limited applications, R = may be suitable, but requires special considerations or additional
elements such as slider or guideways.
Bearing Suitability:
Disk bearing
Pot bearing
Rocker bearing
AASHTO Table 14.6.2-1
Axis indicated
Single roller bearing
Multiple roller bearing
Rotation about bridge
Resistance to Loads
Curved sliding spherical
bearing
Curved sliding cylindrical
bearing
Double cylindrical bearing
Knuckle pinned bearing
Fiberglass reinforced pad
Cotton duck reinforced pad
Steel-reinforced elastomeric
bearing
Plane sliding bearing
Movement
Plain elastomeric pad

TESTS ON CABLE STAYED BRIDGE MODEL
54
1. Wind Tunnel Test
2. FatigueTest
3. TENSILE LOAD TEST OF THE STRAND
4. INSPECTION OF ANCHORAGES
5. CHECKING HARDNESS OF WEDGES
6. ROTATIVE FLEXION TEST

OUR PROJECT DEFINITION
 We have three spans (120+250+120) m
 The deck at the height of (50) m clearance
 We have (80) Cables are arranged in a double
plane over the bridge length with (12) m spacing.
55

COMPONENTS
1. Pylon
We have two non-prismatic pylons ,each one
have (130 m) height.
56

COMPONENTS
2. Deck
 Width = 28 m
 Consists of (6) lanes
 (3) lanes in each direction With width (3.6)m
 An intermediate island (1)m width
 (2) side walk each one (2.7)m width
57

COMPONENTS
2. Deck
 Consists of
 2 Main I girder 2.8 depth of thickness 2 cm and 2 flanges
60 cm width with thickness 5 cm.
 X-girders 2.8 depth of thickness 2 cm and 2 flanges 50 cm
width with thickness 5 cm.
 Stringers with IPE#600 section.
 Concrete Slab of thickness 20 cm Fcu=400 kg/cm2 and
7cm Bitumious asphalt. 58

COMPONENTS
3. Cables
 We have (10) cables in each side of the pylon.
 The cables have initial diameter (12)cm.
 The distance between cables in the deck plan equals to (12) m.
 The distance between them at its links to the pylon equals to (1.5) m
59

MODELING STEPS
(USING CSI SAP2000 PROGRAM )
60

Cable-Stayed Bridge Design Analysis

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Cable-Stayed Bridge Design Analysis

Similar to Cable-Stayed Bridge Design Analysis (20)

Recently uploaded

Recently uploaded (20)

Cable-Stayed Bridge Design Analysis