Suspension bridge

CABLE SUSPENSION BRIDGE
PRESENTATION BY : HEMANT KUMAR

CONTENTS
01- INTRODUCTION
02- TYPES OF SUSPENSION BRIDGE
03- COMPONENTS OF SUSPENSION BRIDGE
04- USE OF ANCHORAGE
05- EVOLUTION OF SUSPENSION BRIDGE
06- STRUCTURAL ANALYSIS LOADS
07- CONSTRUCTION SEQUENCE
08- SOFTWARE CAN BE USED TO DESIGN

09- STRUCTURAL FAILURE
10- SUSPENSION BRIDGE THROUGH OUT THE INDIA
11- ADVANTAGES AND DISADVANTAGES

INTRODUCTION
A suspension bridge consist of two cables, which are stretched over the span to be
bridged. Each cable passing over two towers anchored by backstays to a firm foundation.
As the cable is flexible throughout, therefore it cannot resist any moment and can adopt
any shape under the load, that is why the bending moment at every point of the cable is
taken zero.
The central sag or dip of the cable generally varies from 1/10 to 1/15 of the span. It may be
noted that, since the cable is in tension throughout, this type of construction is most
economical.
DIP

SUSPENDERS
ANCHORAGE
DIP/SAG
MAIN SPANDECK
PINNED
SUPPORT
PYLON
PAVEMENT
FIXED
SUPPORT
SUSPENSION
CABLE

TYPICAL SUSPENSION BRIDGE
The deck (trafficway) of a suspension bridge is hung by suspender cables which hang from
master cables (resisting on the tower). The cables transfer the weight to the towers, which
transfer the weight to the good
TYPES OF SUSPENSION BRIDGE

CABLE STAYED BRIDGES:
Cable-stayed bridges have towers, but cables from the tower go directly to the road deck,
instead of spanning from tower to tower.

COMPONENTS OF SUSPENSION BRIDGE
A suspension bridge is a type of bridge in which the deck (the load-bearing portion) is
hung below suspension cables on vertical suspenders.
 COMPONENTS
 Cables-suspend the roadway(deck) via hangers
 Towers- stabilize wire cables (offer little support)
 Anchorages- key to the structure, mass that keeps cables tight, gives the bridge
structure

WITHOUT ANCHORAGE
WITH ANCHORAGE
ANCHORAGE
Anchorages are the structures to which the
ends of the bridge's cables are secured. They
are massive concrete blocks securely
Attached to strong rock formations.
During construction of the
anchorages, strong eye bars (steel
Bars with a circular hole at one
end) are embedded in the concrete.—each
wire bundle will be secured to one of the
anchorage's eye bars.

EVOLUTION OF SUSPENSION BRIDGES
 The first design for a bridge resembling the modern suspension
bridge is attributed to venetion engineer Fausto Veranzio whose
1595 book Machinae Novae included drawings both for a timber
and rope suspension bridge cable-stayed bridge using iron chains.
 However, the first suspension bridge actually build was by James
Finely(American engineer) at Jacob’s creek, in 1801. Finely bridge
was the first to incorporate all of the necessary components of a
suspension bridge.

CABLE STAYED BRIDGES
Cable-stayed bridges have towers, but cables from the tower go
directly to the road deck, instead of spanning from tower to
tower.
STRUCTURAL ANALYSIS
LOADS
DEAD LOAD
Dead load refers to the weight
of the bridge itself. Like any
other structure, a bridge has a
tendency to collapse simply
because of the gravitational
force acting on the materials of
which the bridge is made.
LIVE LOAD
Live loads refers to traffic that
moves across the bridge as
well as normal environment
factors such as changes in
temperature, precipitation and
winds.
DYNAMIC LOAD
Dynamic load refers to
environment factors that go
beyond normal weather
conditions, factor such as sudden
gusts of wind and earthquake. All
three factors must be taken into
consideration when into
consideration when building a
bridge.

BEHAVIOUR:
THE MAIN FORCES IN A SUSPENSION BRIDGE OF ANY TYPE ARE TENSION IN THE CABLES AND
COMPRESSIONS IN THE PILLARS.

CONSTRUCTION SEQUENCE
TOWERS
Tower foundation are prepared by dagging down to a sufficient
firm rock formation.
Some bridges are designed so that their towers are built on dry
land, which makes construction easier.
If a tower will stand in water, its construction begins with
lowering a caisson (a steel and concrete cylinder that acts as
a circular damn) to the ground beneath the water; removing
the water from the caisson's interior allows workers to
excavate a foundation without actually working in water.

CONSTRUCTION SEQUENCE`
2. SADDLES
Large devices called saddles, which will carry the main suspension cables, are
positioned atop the towers. Typically of cast steel, they can also be manufactured
using riveted forms, and are equipped with rollers to allow the main cables to shift
under construction and normal loads.
3.ANCHORAGE
Anchorages are the structures to which the ends of the bridge's cables are secured. They are massive concrete blocks
securely attached to strong rock formations. During construction of the anchorages, strong eye bars (steel bars with a circular
hole at one end) are embedded in the concrete.—each wire bundle will be secured to one of the anchorage's eye bars.
• CABLE SUSPENSION BRIDGE

4.CATWALKS
Temporary suspended walkways, called catwalks, are then erected using a set of guide wires
hoisted into place via winches positioned atop the towers. These catwalks follow the curve set by
bridge designers for the main cables. Typical catwalks are usually between eight and ten feet
wide, and are constructed using wire grate and wood slats.
Gantries are placed upon the catwalks, which will support the main cable spinning reels.

5.CABLE SPINNING
High strength wire (typically 4 or 6 gauge galvanized steel wire), is
pulled in a loop by pulleys on the traveler, with one end affixed at an
anchorage. When the traveler reaches the opposite anchorage the
loop is placed over an open anchor eye bar. Along the catwalk,
workers also pull the cable wires to their desired tension. This
continues until a bundle, called a "cable strand" is completed, and
temporarily bundled using stainless steel wire.
Then it is brought to shape with compactor
SPINNING
BUNDLE COMPACTION

6.HANGERS / VERTICAL CABLES
At specific points along the main cable devices called "cable bands“(clamps) are installed to carry steel wire ropes called Suspender cables.
Each suspender cable is engineered and cut to precise lengths, and are looped over the cable bands. In some bridges, where the towers are
close to or on the shore, the suspender cables may be applied only to the central span.

7.DECK
After vertical cables are attached to the main support cable, the deck structure can be started. The structure must be built in both directions
from the support towers at the correct rate in order to keep the forces on the towers balanced at all times. In one technique, a moving crane
that rolls atop the main suspension cable lifts deck sections into place, where workers attach them to previously placed sections and to the
vertical cables that hang from the main suspension cables, extending the completed length. Alternatively, the crane may rest directly on the
deck and move forward as each section is placed.
Upon completion of the deck the added load will pull the main cables into an arc mathematically described as a parabola, while the arc of the
deck will be as the designer intended

Structural engineering is usually considered a specialty within
civil engineering, but it ccan also be studied in its own right.
Strucctural engineers are responsible for engineering design
and analysis. Entry-level structural engineers may design the
individual structural elements of a structure, or example- the
beams, columns, and floor of a building.
SOFTWARE USED
STAAD.Pro is the leading Structural Analysis and Design software rom Bentley. STAAD.Pro is
the proessional’s choice ffor steel, concrete, timber, aluminium and cold formed steel
design virtually any structure including culverts, petrochemical plants, tunnes bridges, piles
and much more.

Structural Failure
Some bridges have in the past suffered from structural failure. This may be combination of poor
design and severe weather conditions.
When it was opened in 1940, the Tacoma Narrows Bridge was the third longest suspension
bridge in the world. It later become known as "Galloping Gertie," due to the fact that it moved
not only from side to side but up and down in the wind. Attempts were made to stabilize the
structure with cables and hydraulic buffers, but they were unsuccessful.
Eventually on November 7, 1940, only four months after it was built the bridge collapsed in a
wind of 42 mph. The bridge was designed to withstand winds of up to 120 mph. Some experts
have blamed the collapse of the bridge upon a phenomenon called resonance. When a body
vibrates at its natural frequency it can shatter. Resonance is the same force that can shatter a
glass when exposed to sound vibrations from an opera singers voice.

Nivedita Setu
SUSPENSION BRIDGE THROUGH OUT THE INDIA
Bandra–Worli Sea Link LAKSHMAN JHOOLA
india-arunachal-pradesh-tenga-western kallada river bridge vidyasagar setu bridge

ADVANTAGE
 Longer main spans are achievable than with any other type of bridge.
 Less material may be required than other bridge types, even at spans they can achieve,
leading to a reduced construction cost.
 May be better to withstand earthquake movements than heavier and more rigid bridges.
 Bridges decks can have deck sections replaced in order to widen traffic lanes for larger
vehicles or add additions width for separated cycling/pedestrian path.

DISADVANTAGES
 Considering stiffness or aerodynamic profiling may be required to prevent the bridge deck
vibrating under high winds.
 The relatively low decks stiffness compared to other(non-suspension) types of bridges make it
more difficult to carry heavy rail traffic where high concentrated live load occur.
 Some access below may be required during construction, to lift the initial cables or to lift deck
units. This access can often be avoided in cable stayed bridge construction.

ANY QUERY?

THANK YOU!

Suspension bridge

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