Suspension bridges are iconic structures that have captured the imagination of engineers and the general public for centuries. They are one of the oldest and most widespread types of bridges and can be seen across rivers, straits and other obstacles around the world. In this article, we provide civil engineers with an overview of the different types of suspension bridges and explain the features and characteristics of their various designs.
There are two main types of suspension bridges: cable-stayed bridges and suspension bridges.
Cable-stayed bridges are relatively new compared to suspension bridges. The first were built at the beginning of the 19th century. In this type of bridge, the deck (road surface) is supported by a series of cables fixed to supports. The cables are arranged in a fan shape and serve as struts or supports for the bridge deck.
The main advantage of cable-stayed bridges is that they can span greater distances than suspension bridges of comparable size. This is because the cables support the deck more directly, resulting in more efficient load transfer. For this reason, cable-stayed bridges are often used to cover distances between 2,000 and 4,000 meters.
Suspension bridges, on the other hand, have been used for thousands of years and are among the oldest bridge types still in use today. In a suspension bridge, the deck is suspended from a series of cables attached to towers at each end of the bridge. The cables are arranged in parallel and transfer the weight of the deck and all loads.
Suspension bridges are typically used to span distances between 1,000 and 2,000 meters, but the record-breaking bridge, the Akashi Kaikyō Bridge in Japan, has a main span of just over 3,000 meters.
The main advantage of suspension bridges is that they are very flexible and can therefore withstand strong winds and earthquakes. Furthermore, suspension bridges can be built from different materials, such as steel, concrete and even wood.
Although cable-stayed and suspension bridges are incredible feats of engineering, they each have their own advantages and disadvantages. The type of bridge used for a given project ultimately depends on a series of factors, such as the span of the crossing, the geological conditions of the site, the loads to be supported and the construction materials available.
What is a suspension bridge?
Suspension bridges are the most common type of bridge in the world. They are characterized by using steel cables anchored at each end of the bridge to support it. Suspension bridges have always been built by hand and are not considered particularly complex structures. However, due to their aesthetics, many suspension bridges were built for public entertainment rather than as a means of transportation.
Types of suspension bridges
There are different types of suspension bridges depending on the construction, scale, type of load transmission, etc. Some of the common types are as follows.
- Simple suspension bridges
- Undertensioned suspension bridges
- Voltage Band Bridges
- Suspension bridge with suspended deck
- Self-anchored suspension bridges
Let's discuss each type of suspension bridge in detail.
Simple suspension bridges
Simple suspension bridges are also called rope bridges, swing bridges, suspension bridges, and century-old bridges (Wikipedia). They are the simplest type of suspension bridges.
It is often used as a pedestrian bridge and is very important for traffic. Furthermore, it can be built with minimal costs and does not have a complicated bridge deck. The bridge consists of two cables and a bridge deck.
There are no anchor blocks or towers supporting the bridge. The cable is anchored to the main bridge structure at both ends. Due to its simple construction, construction costs are lower. Furthermore, these types of bridges are more useful in rural areas to cross rivers, canals, etc.
Undertensioned suspension bridges
It is not a common type of bridge across the world and only a few of this type are built across the world. The load transfer mechanism would be the main reason why these types of bridges are not built.
In traditional suspension bridges, the bridge deck is supported by a suspended cable. In this type of bridge, the deck is elevated on the post built on top. Unlike the deck resting on overhead cables, maintaining the stability of the deck when stored on the cable is a challenge.
Most of the pedestrian bridges used are suspension bridges.
Voltage Band Bridges
Voltage band bridges are also called current line bridges.
This is a special type of bridge in which the suspension cable or cables pass through the bridge deck. The cable layout is the same as other types of bridges, but they may not be as visible as other types of suspension bridges.
Due to the nature of stress band bridges, the structure is under tension. This type of bridge is also used for vehicle access.
Suspension bridge with suspended deck
The most common type of bridge in the world. We also recognize this type of bridge as the Suspension bridges . The bridge deck is supported by suspension cables. Very large spans can be built with suspension bridges.
The main components of suspension bridges are towers, anchor blocks, bridge deck and cables.
The construction of the first suspension bridges began in the 19th century.
Self-anchored suspension bridges
Self-anchored suspension bridges are the same as suspended deck suspension bridges. The main difference is that the end of the main cable is attached to the bridge deck while it is attached to the ground.
These types of bridges are erected when it is difficult to lift anchors into the ground due to weak soil conditions. Internal forces, particularly in the main cable, are internally balanced without external supports.
Construction of suspension bridges is not as easy as other types of bridges as it requires a lot of skill in planning and construction. Furthermore, the manufacturing of elements such as the main cable on which the board is suspended is very demanding.
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