The suspension bridge can be defined as the type of bridge in which the load-bearing part of the bridge(deck) is hung below the suspension cables on the vertical suspenders.
~ It is one of the earliest forms of bridge used worldwide since the 1800s.
~ It consists of the cables that are suspended between the towers.
~ The vertical suspender cables transfer the imposed live and dead loads from the deck below to the main cables.
~ The deck in the suspension bridge is constructed to be level or arc upwards form. This is done to provide additional clearance.
~ The bridge’s main cables are essentially anchored to each end of the bridge because any load imposed on the bridge is transformed into tension in these main cables.
1. Components of Suspension Bridge
i. Main Cables:
The main cables refer to the cable that runs along the top part of the suspension bridge and is anchored at the ends.
It can be made up of clusters of either chains or steel.
In some bridges, the leading cable comprises more than ten thousand wires.
ii. Suspender Cables:
The suspender cables are similar to the main cables but are less thick.
The primary function of the suspender cables is to help in the suspension of the deck.
Mostly, the suspender cables are made up of steel.
iii. Deck:
The deck refers to the roadway or the walkway of the suspension bridge, i.e., the part of the bridge through which the vehicles and people travel.
It is mainly constructed using multiple steel trusses.
The span of the deck is the same as that of the bridge.
iv. Towers:
The towers are part of the suspension bridge where the cables are attached.
The arrangement of towers and cables is made to form a parabolic shape with the next tower, thereby creating a solid connection.
v. Foundation of the Tower (or Piers):
The foundation of the tower is the part on which the tower rests.
The tower foundation can be provided above the ground or below the water.
vi. Anchors:
The anchors are the part where the main cables are attached to the ends of the bridges.
Primarily, the rock anchors and the concrete anchors are commonly used.
2. Examples of Suspension Bridge
Some of the famous suspension bridges around the world have been listed as
follows:
i. Akashi Kaikyo Bridge:
Akashi Kaikyo Bridge is the longest suspension bridge in the world, located in Japan.
It is used as a motorway bridge and is made up of steel. It has a total length of 3911 m.
ii. Xihoumen Bridge:
The Xihoumen Bridge is a suspension bridge located in Zhejiang, China.
It has a total length of 2588 m.
3. Advantages
i. Low Cost of Construction:
The cost of construction of the suspension bridge is relatively lower.
The construction materials required are also less expensive.
ii. Flexibility in Span:
It offers excellent flexibility in terms of the span.
It can be constructed in lengths varying from 2,000 to 13,000 feet.
Thus, this bridge is highly suitable for connecting long-distance places.
iii. Ease of Maintenance:
The suspension bridge, once constructed, does not require frequent maintenance and repair.
Only minimal maintenance may be required at meager costs.
iv. Flexibility in the location:
It offers excellent flexibility in terms of the location of construction.
It is also considered suitable for seismic areas.
v. Aesthetic Appearance:
It can also be constructed with aesthetically appealing designs.
Some suspension bridges worldwide are famous and attract thousands of tourists annually. For example, the Brooklyn Bridge in America.
4. Disadvantages
i. Longer Construction Time:
The time required for the construction of this bridge is longer.
ii. Lesser Wind Resistance:
It does not offer much resistance to powerful wind loads and hurricanes. It is not desirable for windy areas.
iii. Limitations of Cables:
The cables of the suspension bridge have limitations in load resistance.
The cables are primarily capable of bearing the minimal weight of the traffic and other loads but may break when subjected to extreme loadings for an extended period.
5. Reasons To Use Suspension Bridge
a. The suspension bridge is less rigid, making it flexible to take external loads like seismic loads, wind loads, etc. Thus, it is also aerodynamically stable with low torsional natural frequencies.
b. Its aesthetic appearance shows the beauty of construction.
c. The bridge supports the cable’s tension and compression in the towers. It is suitable for long-span roadway transport of about (300-2300) m.
d. These days, to reduce active corrosion and stress corrosion cracking in wires, it also has been installed with a dehumidification system that decreases the possibility of bridge failure.
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