Suspension Bridge | ADVANTAGES | HOW DOES IT WORK?

Suspension Bridge | ADVANTAGES | HOW DOES IT WORK?

A bridge which is supported by cables and suspended by the tower is known as a suspension bridge. Here I discussed advantages and how does suspension bridge work? 


suspension bridges


What is a suspension bridge?

When the deck of a bridge is supported by cables which are further suspended by towers and anchored at the ends, this type of bridges are called 'Suspension bridges'.

From the definition of the suspension bridge, you might have questions about its concept, advantages etc.

Don't worry, all of your confusion will be well explained here. STAY TUNED!

The total load from the deck of the bridge travels up the cables or ropes to transfer compressive loads to the towers.

Hence, the majority of the compressive loads(coming from the deck of the bridge) is carried by the towers.

This type of bridge is normally built to span across water or valley.

suspension bridges



The suspension bridge design is simple but the load distribution is a little tricky.

The major forces in a suspension bridge are compressive and tensile forces. 

The tensile forces are carried by the supporting cables and the anchorages, where the towers carry a huge amount of compressive forces.

The suspension bridge allows the longest span range from 2000 - 7000 feet, which allows the engineer to make the longest bridge in the world.

The longest bridge in the world, Akashi Kaiky┼Ź Bridge is an example of a Suspension bridge.


Components of Suspension bridge


I think now you got point about basics of Suspension Bridge. Now, I will discuss two major components which you should know about.

First, Suspension bridge design and the second one is Material & construction of the suspension bridge.

1. Suspension Bridge Design


The suspension bridge design process begins with the topographical survey and the survey about the geology of the site.

Normally suspension bridge is built for a long span and the designing process depends upon some factors like site locations, budget, soil conditions, seismic-zone, availability of raw materials etc.

To make a bridge or any structure more durable it is necessary to consider seismic activities into the account.


When the span of the bridge is very long, it is necessary that the curvature of the earth must be taken into the account.




2. Suspension bridge materials and construction


Choosing the right and superior quality of material is what makes the bridge more durable and weather resisting.

Steel is the primary raw materials in this bridge construction process.

First steel is stretched and formed into wires which is the basics of cables. 

Cables made with stretched wires increases the strength.

consequently, A flexible bundle of steel wires is stronger than a solid steel bar of the same diameter.

That's why cable is being used in this kind of bridge.

If we separate the components of the suspension bridge, we will get three primary components.

  1. Deck of the bridge
  2. Supporting cables
  3. Anchorages and the towers
Tower foundation is one of the most important components of all as it is required to strong enough to carry the huge amount of load.

Suspension bridge built on soil having a low bearing capacity, allow us to choose pile foundation for better stability.

But Sometimes finding bedrock or hard soil beneath the water is quite challenging.

Well, in that case, the caisson foundation is the best solution considered by the engineers.

First, a steel and concrete cylinder are drilled into the ground, then water is removed from the interior which makes easier to work on the foundation.

From the foundation, towers are constructed/erected using HPC(high-performance concrete).

After the construction of towers and cables, it's time for the huge anchorage blocks.

Anchorage is basically made with concrete and is huge in shape.

All of the supporting cables(end of the bridge's cables) are connected to the anchorages

It is necessary to make the foundation and the anchorage block strong enough to resist that huge amount of load coming from cables.


Advantages of the Suspension bridges

suspension bridges facts

1. The first and unique advantage of choosing a suspension bridge is that it allows you to built a bridge of very long span.

2. It is possible to built high over the water which allows the passage of a large ship.

3. This type of bridge can withstand the high magnitude of earthquake and even strong wind load.

4. One of the major factors in advantages of the suspension bridge is cost effective. It can be built on a relatively low cost than other rigid bridges and the required amount of raw materials is also less.


Disadvantages of the suspension bridges


1. As flexibility is it's plus point simultaneously it becomes a negative point when strong wind loads exert pressure on the bridge, and the bridge starts to vibrate.

To prevent this extra safety should be taken into account.

Stiffness and aerodynamic design is the best way to deal with it.

2. Since the whole bridge is supported only on cables which restrict us to high traffic or heavy traffic load.


Conclusion

Sometimes it is quite impossible to build a bridge covering waterbodies, then suspension bridge makes thing easy.
It can be built with less trouble.
In civil engineering, the advantages of suspension bridge are simply unavoidable.
In the future, engineers will push their limit to enhance the feature of the suspension bridge.


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