Cantilever Bridge Facts: You Must Read This Mind-Blowing Blog!

Cantilevers are structures that project horizontally into space and are supported at only one end, and these structures are used to make cantilever bridges.

If the right materials and proper engineering are applied, there can be over 1,500 ft (458 m) of length in a steel truss cantilever bridge. This kind of cantilever bridge has been always been used for trains, pedestrians, and motor vehicles and is quite popular all over the world.

While making small footbridges, cantilevers can even be simple beams, but as the cantilever bridges get bigger to accommodate road or rail traffic, it uses trusses made from structural steel.

These large cantilever bridges sometimes also use box girders made from prestressed concrete. The first major engineering breakthrough was the steel truss cantilever bridge that can be made in long lengths and can even be made at difficult crossings by using little or even no falsework.

For those who don't know what falsework is, it uses temporary structures in construction to support the main structure until the main structure is able to sustain and take care of itself.

The first modern cantilever bridge was the Hassfurt bridge located over Germany's Main River. Hassfurt bridge has a span of 124.6 ft (38 m) and was constructed in 1867.

There were many earlier uses of cantilever designs which were important throughout the time they were constructed.

Some of them are High Bridge of Kentucky by C. Shaler Smith made in 1877, the Niagara Cantilever Bridge made by Charles Conrad Schneider in 1883, and the Poughkeepsie Bridge made by Pomeroy P. Dickinson and John Francis O'Rourke in 1889.

The Kentucky River Bridge spanned a gorge of a depth of 275 ft (83.8 m) and this cantilever bridge proved that falsework is not required for the main span.

A balanced cantilever is also considered another technique to make long-distance bridges. Here are some popular ones all over the world - Quebec bridge, Forth bridge, Minato Bridge, Commodore Barry Bridge, Crescent City Connection, Howrah Bridge, Gramercy bridge, Tokyo Gate Bridge, J. C. Van Horne bridge, Horace Wilkinson bridge, Tappan Zee Bridge, Lewis and Clark Bridge.

Go on to read some more facts about cantilever bridges all over the world.

Foundations Of A Cantilever Bridge

Cantilever bridges are one of the most famous ones used all over the world due to their practicality and easy usability.

To make a cantilever bridge, you need materials that can include steel, cables, and concrete. The base of a cantilever bridge is made using steel beams and these are attached to the deck of the bridge using screws.

Even reinforced concrete can be used in place of steel to make the cantilever beams that hang from the deck. The location and the type of bridge determine the materials used.

To design a cantilever bridge, there are a few design aspects needed that contribute to the durability and strength of the cantilever bridge. The main vertical supports of a bridge can be either made of steel or concrete. It is called a superstructure.

Steel is more commonly used as the beams are longer and require less maintenance. The deck of cantilever bridges can be made of steel or concrete and it is then covered with asphalt to make the surface less slippery.

Cantilever beams are also supported by the deck of the cantilever bridges. Rods and cantilever beams are the main components.

Rods are actually steel cables seen along the bridge from pylon to pylon. Cantilever beams are connected by cross beams or struts.

These are made with steel and consist of two support bars. To allow access to the central span of the bridge, pivots are used.

They are vertical columns that raise and lower the deck of the cantilever bridges. Pivots can also be used as guardrails in areas where traffic is heavier.

Supports are other add-ons that help in supporting the deck and are made of steel. The supports also help the deck move a little up and down which helps in reducing wind loads and also protects the cables and rods from dust. Cables are used from one end to the other across each of the main supporting beams.

Stringers help in creating the appearance of a uniform base and are horizontal timbers. Deck plates are important elements of cantilever bridges and are made of reinforced cement or steel.

These deck plates fill between the supports for the vehicles to pass swiftly. Pylons are pillars permanently standing on either side of cantilever bridges.

Deck of cantilever bridges sits directly on the ground without crossbeams, however, truss bridges have a deck base similar to that of a base plate. A truss bridge is made of the same base components as a cantilever bridge.

A truss bridge is actually pieces of small parts that lead up to the main components of a simple cantilever bridge (the deck and supporting beams). A truss bridge is built in sections.

Usage Of A Cantilever Bridge

Most bridges take up a lot of space and create traffic jams, whereas, cantilever bridges allow the traffic to move on. It helps to make cantilever bridges in areas where there's not much space like between valleys and rivers where floods are common.

Even to carry large weights, cantilever bridges are helpful. The cantilever decks are denser and box girders are made of prestressed concrete. They are simple and cheap, so even when building large cantilever bridges, the cost will be much less than other kinds of bridges.

Trucks, buses, trains, and anything smaller can be accommodated on steel truss cantilevers. Even other early cantilever bridges could hold their own in these circumstances.

Quebec bridge or Pont de Québec is the longest cantilever bridge from 1917 until today with a length of around 1,800 ft (548.6 m). Forth Bridge was the longest until the construction of the Quebec bridge and has a length of 1,710 ft (521.2 m).

Other popular cantilever bridges include Minato Bridge, Commodore Barry Bridge, Crescent City Connection, Veterans Memorial Bridge, Howrah Bridge, San Francisco–Oakland Bay Bridge (east bay span), Tokyo Gate Bridge, J. C. Van Horne Bridge, Horace Wilkinson Bridge, and Astoria–Megler Bridge.

All of these are made of structural steel and some allow both or sometimes road or rail traffic. Minato Bridge is a double-decker bridge built in 1973.

Building Methods For A Cantilever Bridge

There are various building methods for a cantilever bridge. Engineer Heinrich Gerber used a hinged girder to make the first cantilever bridge in 1867 to cross the Main River in Germany. The longest single cantilever span record is now held by the Quebec Bridge of Canada.

The most popular and effective method is the balanced cantilever technique to span long distances. There are many steel arch bridges that employ pure cantilever spans from each side with no cables or falsework.

These are joined together with a pin. Cable-stayed bridges also employ the cantilever technique to attain the best results. A simple cantilever bridge has two cantilever arms coming from the opposite direction of the thing that needs to be spanned and then they converge at the middle.

The first thing in building this bridge is to connect the cantilever arms to the shore. River piers should not be built until the cantilever arms touch the surface. River piers can be subsequently built after that.

You might also see a suspended span bridge sometimes. A suspended span bridge is built when a bean bridge or truss bridge needs to be placed between two cantilever arms to connect them to a single bridge.

You will often see towers above the foundation piers. This bridge superstructure is made for more strength at the supports of a balanced cantilever.

History Of The Cantilever Bridge

Bridge engineering has evolved a lot and cantilever bridges are the perfect example of that.

The first cantilever bridge was made in 1867 by Heinrich Gerber and there has been no looking back. Many years back, bridges were not like the ones we see today.

Only in the 19th century, did engineers start to understand that if a bridge is constructed using multiple supports, it would distribute the load evenly on all sides. Continuous bridges were patented by 19th-century engineers with hinge points in the middle.

The advantages of a statically determinate system were seen by the use of a hinge in the multi-span system.

A hinged girder helped engineers understand the forces and stresses better and calculate them easily. Heinrich Garber is recognized as the first engineer to build a hinged girder in 1866 and he was the first one to obtain a patent for the first cantilever bridge.

Quebec Bridge In Quebec, Canada is now the longest cantilever bridge with its span of 1,800 ft (548.6 m). Even the Forth Bridge, a cantilever bridge located over the Firth of Forth near the Edinburgh City Centre has a span of 1,710 ft (521.2 m).

Minato Bridge located in Osaka in Japan has a span of 1,673 ft (509.3 m). Forth Bridge, a railway bridge is a famous cantilever bridge in the world. The bridge has three great four-tower cantilever structures.