Cable and suspension bridge

1. Created by :- Nishant patel

2. Index
•Introduction
•Function of bridge
•Main element
•Forces exceed on the bridge
•Examples

3.  A suspension bridge is a type of bridge in which the
deck (the load-bearing portion) is hung below
suspension cables on vertical suspenders. The first
modern examples of this type of bridge were built in
the early 19th century. Simple suspension bridges,
which lack vertical suspenders, have a long history in
many mountainous parts of the world.
 This type of bridge has cables suspended
between towers, plus vertical suspender cables that
carry the weight of the deck below, upon which traffic
crosses. This arrangement allows the deck to be level
or to arc upward for additional clearance. Like other
suspension bridge types, this type often is
constructed without false work.

5. FUNCTION OF A BRIDGE
To connect two
communities which are
separated by streams,
valley, railroads, etc.
•Suspension bridges are
used for highways , where
the span of a bridge is more
than 200m.

6. i. Main cable
ii. Suspenders
iii. Decking and stiffening girder
iv. Supporting tower
v. Anchor cable

7. A
VA VB
B
T T
HH
W KN/m

8. reactionHorizontal
8
8
48
228
2
2
2
22
2





d
wL
dH
wL
dH
wLwL
dH
LwLwL
dH
wL
VV BA
Equation of horizontal reaction
Taking moments
about c, on the right
side of c

9. ß
p
B
H
T
T w kN/m
?

10.  The cable tension T at any end is the
resultant of vertical and horizontal reaction at
the end.
2
2
2
42
2
2
2
16
1
2
64
)
2
(
)
8
()
2
(
d
LwL
T
d
LwwL
T
d
wLwL
TTT BA




11.  T= Tension at any point p of the cable
 Ɵ=Inclination of the tangent at p with
horizontal consider equilibrium of part PB
 Resolving the forces on this part horizontally.
 Minimum tension in cable will occur at c
cosTH 
HTT c  min

12.  Maximum tension in cable will occur at ends
 The inclination β of T with vertical is given by,
2
2
max
16
1
2 d
LwL
T 
d
LwL
d
wL
42
/
8V
H
tan
2


13.  Under the uniformly distributed load the
cable takes the from of a parabola
 The equation of cable , with either support as
origin will be,
)(
4
2
xLx
L
d
y 

14.  The equation of parabola, with c as the origin
can be written as ,
 Consider an element of length ds of the
curve, having coordinates x and y.
2
2
2
8
4
L
xd
dx
dy
x
L
d
y




15. dx
L
xd
ds
L
xd
L
xd
dx
ds
L
xd
L
xd
dx
ds
dx
dy
dxds
dydxds





 



























4
22
4
22
4
22
2
1
4
22
4
22
2
22
321
ofpowershighernegleting
andtheorembinominalbyExpanding
64
2
1
1
64
1
64
1
1


16.  Total length of the cable,
cable.theoflengthTotal
3
8
3
4
2
2
3
32
2
32
12
2
4
3
2
2
0
3
4
2
2
0 4
22





















 
L
d
LS
L
L
d
L
S
x
L
d
xS
dx
L
xd
S
L
L

17.  the main cables attach to the ends of the
deck, rather than to the ground via large
anchorages. The design is well-suited for
construction atop elevated piers, or in areas
of unstable soils where anchorages would be
difficult to construct.
 There are generally two arrangement used
1. The suspension cable can be passed over
the guide pulley for anchoring it to the
other side
2. The suspension cable and anchor cable can
be attached to a saddle mounted on rollers.

18. ß1 ß2
suspension
cable
Anchor
cable
ß2 ß1
Anchor
cable suspencion
cable
Guide pulley
arrangement
Saddle on roller
arrangement

19.  21 coscos  TVp
 21 sinsin  THp
1
2

20.  In case of saddle on roller arrangement, rollers
do not have any horizontal reaction. Therefore,
the horizontal components of the tensions in
the suspension cable and the anchor cable will
be equal.
 The vertical pressure on the top of the pier is,
HTT  2211 sinsin 
2211 coscos  TTVp 

21. SUNSHINE SKYWAY BRIDGE, USA
Completion Date: 1987 Cost: $244 Million
Length: 29,040 feet Type: Cable
Stayed
Materials: Steel, Concrete Span: 1200
feet

22. AKASHI KAIKYO BRIDGE, JAPAN
Completion Date: 1998 Cost: $4.3 billion
Length: 12,828 feet Type: Suspension
Materials: Steel Span: 6,527 feet