2. INTRODUCTION
•A suspension bridge is a type of bridge where the deck is
hung below suspension cables on vertical suspenders.
• Aesthetic, light, and strong, suspension bridges can span distances
from 2,000 to 7,000 feet - far longer than any other kind of bridge.
• It suspends the roadway from huge main cables, which extend from
one end of the bridge to the other.
• These cables rest on top of high towers and are secured at each
end by anchorages.
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3. A suspension bridge usually has two towers that hold up
the main cables
From these main cables hang vertical cables that are attached tothe
deck of the bridge.
First iron chain suspension bridge was opened in 1801 in
Westmoreland County, Pennsylvania designed by James Finley.
• The towers enable the main cables to be draped over long distances.
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4. COMPONENTS
•Cables- the central design element to a suspension bridge are
the cables.
They are strong steel strands and fixed to an anchor then
threaded over the towers and attached to the anchor on the
other side.
•Anchors- anchors are placed into the shoreline material at
both ends of the bridge. The cables are attached into the
anchorsto maintain tension in the cables.
•Towers- These towers supports the massive cables that hold
the entire bridge in the air
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5. •Tower foundations-the weight of the bridge resting on cables
which in turn rest on the towers, it must have a solid foundation.
The depth of the foundation depends on the depth of weight-bearing
soil.
•Deck- the final component of a suspension bridge is the deck,
or the roadway upon which vehicles move and pedestrians
walk.
•Hangers- these are the vertical suspender cables which support
the roadway.
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7. STRUCTURALANALYSIS
•Dead load- It refers to the weight of the bridge itself.
•Live load- refers to traffic that moves across the
bridge as well as normal environmental factors such as
changes in temperature etc.
•In a suspension bridge, the weight of the road deckis
transferred by the cables to the towers , which in turn
transfer it to the ground.
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8. The main forces are tension in cables and compression in
towers.
The main cables of a suspension bridge forms a
parabolicshape if their weight is assumed negligible
as compared to thedeck.
The suspension cables must be anchored at each end of the
bridge to maintain tension in these cables.
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10. CONSTRUCTION SEQUENCE
Towers
• Tower foundations are prepared by digging down to a
sufficiently firm rock formation.
• Some bridges are designed so that their towers are built on dry
land, which makes construction easier.
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12. • 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.
• If the bedrock is too deep to be exposed by excavation or the
sinking of a caisson, pilings are driven to the bedrock or into
overlying hard soil, or a large concrete pad to distribute the weight
over less resistant soil may be constructed, first preparing the
surface with a bed of compacted gravel.
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13. Saddles
• A block at the top of the tower of a suspension
bridge over which pass the suspension cables or
chains.
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14. ANCHORAGES
• These 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.
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16. • Temporary suspended walkways are 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 8-10 feet wide and are
constructed using wire grate and wood slats.
• Gantries are placed upon the catwalks will support the main cable
spinning reels.
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17. 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.
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18. DECK
• A bridge deck or road bed is one of the structural element of the
superstructure of a bridge
• A moving crane that rolls on the top of 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.
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20. The Golden Gate Bridge is a suspension bridge. It is one mile
wide (1.6 km) strait surrounded by San Francisco Bay and the
Pacific Ocean.
The structure links the American city of San Francisco to
Marin County
It has been declared one of the Wonders of the Modern World by the
American Society of Civil Engineers.
INTRODUCTION
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22. PURPOSE
The main purpose is to connect San Francisco to Marin
county.
Before the bridge opened in 1937, the only practical route
between them was by ferry across San Francisco Bay.At
the time, San Francisco was the reached primarily by
ferry.
An elevation or clearance of 67m was given to allow the
passage of massive and huge ships under the bridge.
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23. GENERAL INFORMATION OF THE BRIDGE
• Chief engineer
• Architect
-Joseph Strauss
-Foster Morrow
• Beginning of Project -(5 January 1933)
• Completion
• Cost
• Status
- 28 May 1937)
- $ 35 million)
(in use)
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24. PROJECT TYPE
• Structure - Suspension bridge
It opened in 1937 and until 1964, it was the longest
suspension bridge in the world.
• Function - Motorway bridge
• Material – Steel bridge
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25. MATERIAL USED IN CONSTRUCTION
• Cables: They are entirely made up of steel.
• Deck truss: Made up of steel using rivets.
• Pylons: Made up of steels and sections are
joined together by using rivets.
• Color: International orange
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26. LOADING ON BRIDGE
The most important types of loadings considered on the
bridge construction are:
• Dead load
• Live Traffic
• Wind
• Temperature
This bridge is designed constructed in a way that it can
bear:
• 90 mph of wind.
• 8.0 intensity earthquake.
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27. ADVANTAGES
They can span longer distances than any other type of
bridge.
Bridge decks have widen traffic lanes for
larger vehicles or width for cycling paths
They can withstand earthquakes better
than stiff conventional bridges.
Built over waterways, it can be built high,
allowing the passage of tall ships
unhindered by the bridge
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28. LIMITATIONS
Road deck can vibrate and even twist in high winds
• 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.
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29. INFERENCE
• These are pioneers in modern day bridge technology
• These type of bridges are meant for light and heavy
roadways rather than railways.
• Longer spans up to 2000-7000ft is possible
• The main forces are tension in cables and compression
in towers.
• The weight of the road deck is transferred by the cables
to the towers , which in turn transfer it to the ground.
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30. REFRENCES
• Yau and Fryba (2007) “Response of suspended beams due to moving
loads and vertical seismic ground excitations”, Engineering Structures,
ASCE
• John A. Ochsendorf and David P. Billington(2001),”Self-anchored
suspension bridges”, Journal of bridge engineering, ASCE
• Z. W. Chen. M and Y. L. Xu(2011),”Dynamic stress analysis of long
suspension bridges under wind and highway loadings”, Journal of
Bridge Engineering, ASCE
• Kei Fung Sameul and kwan “The study on san francisco golden gate
bridge” University of Bath, Bridge Engineering, Conference,7 April
2007
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