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Seminar
On
 Suspension
Bridge

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 CONTENTS
 What???
 Types of Bridges
 Arch Bridge
 Beam Bridge
 Cable-stayed Bridge
 Cantilever Bridge
 Truss Bridge
 Suspension Bridge – An Introduction
 Terms related to Suspension Bridge
 Structural Analysis
 Structural Failure
 Quality Control in Suspension Cable
 Advantages & Limitations
 Load Distribution in Different Types of Bridges
 Conclusion
 References
 BRIDGE
 A bridge is a structure built to span a valley,
road, body of water, or other physical
obstacle, for the purpose of providing
passage over the obstacle.
 Designs of bridges vary depending on the
function of the bridge and the nature of the
terrain where the bridge is constructed.
 TYPES OF BRIDGE
 There are six main types of bridges:-
 Arch Bridge

 Beam Bridge

 Cable-stayed Bridge

 Cantilever Bridge

 Truss Bridge

 Suspension Bridge
ARCH BRIDGE
 Arch bridges are arch-shaped and have abutments at
each end.
 An arch bridge doesn't need additional supports or
cables. In fact it’s the shape of the structure that gives
it its strength.
 Arch bridges are designed to be constantly under
compression.
 The weight of the bridge is thrust into the abutments
at either side.
 Usually they are made for short span range but often
set end-to-end to form a large total length.
BEAM BRIDGE
 Beam bridges are the simplest kind of bridge today.
 Bridges consist of one horizontal beam with 2
supports usually on either ends.
 It is frequently used in pedestrian bridges and for
highway overpasses & flyovers.
 They are constructed for short span requirements.
 The weight of the bridge and any traffic on it is
directly supported by the piers.
 The top side of the deck is under compression while
the bottom side of the deck is under tension.
 To increase the bridge’s strength designers introduce
truss to the bridge’s beam.
CABLE-STAYED BRIDGE
 A bridge that consists of one or more pylons with cables.
 There are two major classes of cable-stayed bridges such as
a harp design & a fan design.
harp
fan design
design

 The cable-stay design is best suited for a medium span

range.
 The towers form the primary load-bearing structure.
 It has greater stiffness.
 The cables act as both temporary & permanent supports to
the bridge-deck.
 The tower in a cable-stayed bridge is responsible for
absorbing and dealing with the compression forces while the
cables are under tension.
CANTILEVER BRIDGE
 A bridge built using cantilevers, structures that project
horizontally into space, supported on only one end.
 For small footbridges, the cantilevers may be simple
beams; however, large cantilever bridges are
designed using trusses.
 These are constructed for short to medium span
ranges.
 Cantilevers support loads by tension of the upper
members & compression of the lower ones.
TRUSS BRIDGE
 A bridge composed of straight connected elements
which may be stressed from tension, compression, or
sometimes both in response to dynamic loads.
 A truss bridge is economical to construct owing to its
efficient use of materials.
 These are usually constructed for short to medium
span range.
 In India truss bridges are generally constructed for rail
traffic.
 Vertical members are in tension, lower horizontal
members in tension, shear, and bending, outer
diagonal and top members are in compression, while
the inner diagonals are in tension.
SUSPENSION BRIDGE
 Nowadays these are the pioneers in bridge
technology.
 Of all the bridge types in use today, the suspension
bridge allows for the longest span ranging from 2,000
to 7,000 feet.
 This type of bridge has cables suspended between
towers & the cables support vertical suspender cables
that carry the weight of the deck below. This
arrangement allows the deck to be level or to arc
upward for additional clearance.
 The suspension cables are anchored at each end of
the bridge.
 They are ideal for covering busy waterways.
 TERMS RELATED TO SUSPENSION BRIDGE
 Side span: segment between two pylons at the ends of a
bridge.
 Centre span: segment between two pylons at the centre of
a bridge.
 Side pylon: tower-like vertical construction situated at the
side. usually supporting the cables of a suspension bridge.
 Foundation of a pylon: very durable lower part of a tower.
 Suspender: support cable.
 Suspension cable: set of braided wire that supports a
bridge.
 Pylon: tower-like vertical support that usually supports the
cables of a suspension bridge or a cable-stayed bridge.
 Stiffening girder: tightener beam.
 STRUCTURAL
ANALYSIS
 The main forces in a suspension bridge are tension in the
main cables and compression in the pillars. Since almost
all the force on the pillars is vertically downwards and they
are also stabilized by the main cables, they can be made
quite slender.
 In a suspended deck bridge, cables suspended via towers
hold up the road deck. The weight is transferred by the
cables to the towers, which in turn transfer the weight to
the ground.
 Most of the weight or load of the bridge is transferred by
the cables to the anchorage systems. These are imbedded
in either solid rock or huge concrete blocks. Inside the
anchorages, the cables are spread over a large area to
evenly distribute the load and to prevent the cables from
breaking free.
STRUCTURAL ANALYSIS
STRUCTURAL FAILURE
 Some bridges have in the past suffered from structural
failure due to combination of poor design and severe
weather conditions.
 Collapse of the bridge also depends upon a
phenomenon called resonance. It is the phenomenon
when a body vibrates at its natural frequency & it
shatters.
 To avoid these types of failures today all new bridges
prototypes have to be tested in a wind tunnel before
being constructed.
 QUALITY CONTROL IN
SUSPENSION CABLE
 The main suspension cable in older bridges was often made
from chain or linked bars, but modern bridge cables are made
from multiple strands of wire. This contributes greater
redundancy; a few flawed strands in the hundreds used pose
very little threat, whereas a single bad link or eyebar can cause
failure of the entire bridge.
 Another reason is that as spans increased, engineers were
unable to lift larger chains into position, whereas wire strand
cables can be largely prepared in mid-air from a temporary
walkway.
 The cables are made of thousands of individual steel wires
bound tightly together. Steel, which is very strong under
tension, is an ideal material for cables; a single steel wire, only
0.1 inch thick, can support over half a ton without breaking.
QUALITY CONTROL IN
SUSPENSION CABLE
 ADVANTAGES OVER OTHER
BRIDGE TYPES
 Longer main spans are achievable than with any other
type of bridge.
 May be better able to withstand earthquake
movements than can heavier and more rigid bridges.
 The center span may be made very long in proportion
to the amount of materials required, allowing the
bridge to economically span a very wide canyon or
waterway.
 It can be built high over water to allow the passage of
very tall ships.
 LIMITATIONS COMPARED TO
OTHER BRIDGE TYPES
 Considerable stiffness or aerodynamic profiling may
be required to prevent the bridge deck vibrating under
high winds.
 The relatively low deck stiffness compared to other
types of bridges makes it more difficult to carry heavy
rail traffic where high concentrated live loads occur.
 Under severe wind loading, the towers exert a large
torque force in the ground, and thus require very
expensive foundation work when building on soft
ground.
LOAD DISTRIBUTION IN DIFFERENT TYPES OF
BRIDGES

Cable-stayed Beam bridge

bridge tension

compression

Cantilever bridge
 CONCLUSION
 These are the pinnacles in modern days bridge
technology.
 Longer spans of up to 2000 ft-7000 ft is possible.
 They are ideal for covering busy waterways such as
Gulf, Strait, Lake, etc.
 These bridges are mainly meant for light & heavy
roadways rather than railways.
 The main forces in a suspension bridge are tension in
the main cables and compression in the pillars.
REFERENCES

 www.google.com
 www.wikipedia.com

 www.studymafia.org

 www.pptplanet.com
THANKS