What are Cantilever Bridges?

Cantilever Bridge

Pont de Quebec Bridge, Canada

The bridges that have span which is supported at only one end. On a small scale, they are used as footbridge which is simple beams. For heavy traffic load operation, we see large trusses or box girders which are mainly prestressed concrete. 

A cantilever bridge is constructed using cantilever which is horizontal structures only supported from one end. Cantilever must be firmly anchored on one side in order to hold up the necessary weight on free-standing and avoid shear stress. A balanced cantilever is another technique for spanning long distances. Here a pier is constructed over which one side of the cantilever is built and the same on the other side and then connected in between.

Side span is the length of the cantilever, not overall length.

Great Example of such bridge is Pont de Quebec Bridge, Canada ( 549 m side span)

Some other examples are:

• Minato Bridge, Japan (235 m side to span)
• Commodore Barry Bridge, United States (250.55 m side span)
• Crescent City Connection, United States ( 480 m side span)
• Howrah Bridge, India ( 457.20 m side span)
• Gramercy Veterans Memorial Bridge, United States ( 445.01 m side span)
• Horace Wilkinson Bridge, United States ( 376.43 m side span)
• Tappan Zee Bridge, United States ( 369 m side span)
• Lewis and Clark Longview Bridge, United States ( 365.76 m side span)
• Ed Koch Queensboro Bridge, United States ( 360 m side span)

Forth Rail Bridge, Scotland

The first cantilever bridge was seen in the 19th century when a need for longer bridges increased.

Here, a simple cantilever bridge has to cantilever arms extending from opposite sides of an obstacle that has to be spanned and they meet at the center. They are also of very rigid construction so they can carry large loads without threat for construction.

The Fourth Bridge is a cantilever bridge which is the symbol of Scotland which is also a UNESCO World Heritage Site. This bridge construction started in 1882 and when it opened in 1890 it was Worlds Longest Single Cantilever Bridge Span and hold this record till 1919 when Quebec Bridge in Canada opened.