Mind-Boggling Facts About Suspension Bridges That You Didn't Know

What exactly makes a bridge?

Bridges, in simple words, are structures that span over valleys, roads, water bodies, and more, to overcome them as obstacles without changing the obstacles or blocking their way. It makes it easier to cross such obstacles, which would otherwise be difficult or sometimes even impossible to do!

Over the years, humans have made multiple designs and structures that provide the same purpose in different and more efficient manners.

Each design can solve different issues, provide a different function, and give the bridge an aesthetic look.

The look of the entire bridge depends on many factors, such as the function, topography of the area where we want to build a bridge, the availability of material and cost for construction, and so on. The bridges built in the beginning were most likely made of trees that had fallen and with stepping stones found around.

One of the oldest bridges in existence is the Arkadiko Bridge which dates back to the 13th century BC in the Peloponnese; this bridge has an arch and people still use this arch bridge today!

Do you like reading about suspensions bridges and their types? To know more about this type of bridge, read on! 

The History Of Suspension Bridges

Suspension brides are types of bridges that have been suspended using roadway cables, chains, and ropes from two tall towers. These towers are helpful in supporting the majority of the weight the bridge exerts.

The heaviness of the bridges compresses on the deck of the suspension bridge, and after that, it travels through the cables and the ropes to finally reach the top of the towers that are suspending the bridge. Finally, the two towers dissipate the compression into the earth directly.

The cables that support the bridge can retain the tension forces of the bridge. The cables and ropes are hanging horizontally between the two tall anchorages. The massive concrete blocks or rock-solid anchorages help in the grounding of the bridge.

The tension forces which are held by the cables pass to these anchorages and then go into the ground. On the other side, the supporting cables receive the bridge's tension forces.

Between the two far-flung anchorages, these cables run horizontally. The bridge is grounded in solid rock or enormous concrete blocks called bridge anchorages. The tensional force is transmitted to the anchorages and the ground.

These bridges are estimated to be around 6000 years old. The olden bridges were made out of cable or ropes that hung from the chasms horizontally with a deck at the same or a level below the ropes in a catenary shape.

The Tibetan bridge-builder and Siddha started using chains while building suspension bridges. Gyalpo had built eight bridges on the east side of Bhutan in the year 1433.

In 2004, the last surviving bridge built by Gyalpo, which was a chain-linked bridge, finally washed away. This bridge was used to connect Duksum to Trashi Yangtse.

These chain-linked bridges didn't have a deck that was suspended like we can see today. Most of the portion of these bridges was made out of wires, including the walking layer and the railing.

Iron chains carry most of the weight in that case. Before using iron chains, he used to use ropes made from willows that were twisted or yak skins or even tightly bound clothes!

The first iron chain suspension bridge known is in Westmoreland County in Pennsylvania, called Jacob's Creek Bridge. This bridge was made by the inventor James Finley.

This bridge is one of the first bridges to have all the main bridge components used today, including the deck, which is hung using the trusses. His findings were published in the Philadelphia journal, and he also filed a patent in the year 1808.

The first known wire-cable suspension bridge was built in 1816, called the Spider Bridge at Falls of Schuylkill, a temporary bridge built when the Chain Bridge at Falls of Schuylkill had collapsed in the year 1808. The main span of this footbridge was around 124 m (406.82 ft), and the deck was just 0.45 m (1.47 ft) wide.

Materials Used In Suspension Bridges

The term bridges can be classified into different types based on compression, torsion, bending, tension, and shear, which are distributed through the entire structure of the bridge. 

The majority of the bridges will have most of the above features. However, only some of them will have these as predominant.

The separation of moments and forces might be clear. Such elements are in a very distinct form and shape in the cable-stayed or suspension bridge. In the remaining cases, the forces can be distributed into huge amounts of members like in the truss.

One common material used in suspension bridges is steel. The plate girders, which are the main component of the deck of the bridge, are usually made out of steel.

Further, steel is also used to build other components such as open channels or saddles where the ropes are resting on the top of the towers, which are holding onto the weight.

The steel, when stretched, becomes stronger and also increases flexibility as the relatively flexible bundle of steel wires is stronger than a solid steel bar of a similar diameter.

This is the main reason steel is used in building suspension bridges.

Special new alloy steel, which was strengthened with silicon, was made to make the Akashi Kaikyo Bridge. The tensile strength, which is the resistance it has against the pulling forces, is 12% greater than any other steel wire formulas used before.

Sometimes the steel used to make the suspension bridge wires and cables are galvanized, i.e., coated with zinc. Even though steel is the most used material in suspension bridges, some have been constructed using reinforced concrete.

Different Types Of Bridges

Most of the bridges we see outside are known as fixed bridges. This means that the bridge has parts that are fixed and immovable. They remain in a single place without swaying. Some bridges are even temporary, like the Bailey bridges.

They are manufactured in a way that they can be put together piece by piece and removed later whenever required. They can even be transported from one place to another to reuse them. One of their important application is during bridge reconstructions or in the military.

There are various different types of bridges, like the simple suspension bridge. This is one of the earliest known bridges, which was generally known as a footbridge.

The main ropes or cables are anchored to the ground, and the deck structure of the bridge is flexible too! The under-spanned suspension bridge is a 19th-century bridge that can be said to be a descendent of the simple suspension bridge.

The difference in this bridge is that the bridge deck is raised above the ground with the help of posts that are above the main cables. The most commonly seen types of suspension bridges include the suspended-deck suspension bridge.

This bridge is most suitable for traffic and roads which are used by bigger vehicles or heavy vehicles as well as lightweight railways. The main cables suspend the stiff deck, which is anchored to the earth just like any suspension bridge.

Another type is known as the self-anchored suspension bride. This is a modern bridge type.

It incorporates some design aspects of the cable-styled bridges. The main cables of the deck units are anchored to the earth.

There are a few suspension bridges that are not very commonly seen. They are usually the hybrid bridge types, and these have an intermediate deck. Some portions of these bridges resembles the under-spanned suspension bridges.

Interesting Facts About Suspension Bridges

The earliest known suspension bridges were probably made by the Neolithic people who built a boardwalk to walk across the marshes. The Post Track and Sweet Track in England are some famous old examples of suspension bridges we can see today.

The suspension bridge has cables, also known as suspension cables, which are hanging from the two tall towers which are then attached to the vertical cables, also called suspender cables or hangers which hold the deck.

The cables used on the bridge are anchored at the end from each side of the bridge, which carries most of the bridge weight.

The largest suspension bridge ever made is the Akashi Kaikyō Bridge. Some main parts of the suspension bridge include the main towers, anchorages, cables, and trusses!

Using these components, the Golden Gate Bridge can stay up.

Suspension bridges have a long life span. Some bridges, like the Brooklyn Bridge in New York City, have lasted over 100 years!

A fun fact about suspension bridges is that the design we use for suspension bridges today was first developed in the early 19th century! Between Stalker, Pennsylvania, and Hankins, New York, the Kellams Bridge is a suspension bridge across the Delaware River.

Suspension bridges are beautiful, light, and robust, and they can span distances of 2,000-7,000 ft (609.6-2133.6 m), far longer than any other type of bridge. They are also the most expensive to construct.

In the year 1940, Tacoma Narrows Bridge was known for being the third-longest suspension bridge. It was also nicknamed the Galloping Gertie because it used to behave differently in the high winds.

The bridge used to move and sway during windy conditions. The drivers, on multiple occasions, had raised concerns regarding driving on the bridge and its unusual activities.

The engineers had made attempts to make the suspension bridge stable. However, they were unsuccessful even after trying hydraulic buffers and cables. Eventually, in 1940, on November 7, the suspension bridge collapsed just four months after its opening.

At the time of the collapse, the wind speeds were just 42 mph (67.59 kph) even though the bridge was made to withstand wind speeds up to 120mph (193.12 kph)! The Golden Gate Bridge is a renowned suspension bridge.

This bridge is located in San Francisco, a big city in California. It is also a big tourist attraction as it looks majestic over the sea!