How to Build a Suspension Bridge

There are many types of bridges, but if you have a really long river to cross you will need to build a suspension bridge.  Suspension bridges are some of the greatest constructions of civil engineering with many spectacular examples worldwide.

Building a suspension bridge

The name offers a strong clue to the construction.  A suspension bridge is so called because the main roadway section of the bridge is suspended from enormous steel cables running down from a pair of towers and fixed into massive reinforced concrete blocks (called “anchorages”) at each end of the bridge.  This is a hugely complicated civil engineering process but (very basically) this is what happens.

The towers (which may be founded on dry land or underwater) are built up from reinforced concrete or steel, with a gap for the main roadway. Then the anchorages are installed to hold the cables.  Very thin steel cable is “spun” from between the anchorages, shuttling to and fro, until it can be gathered together to form two large cables of enormous strength.  Other cables are then dropped down from the main cables and the sections of prefabricated roadway are attached to them. The finishing touches such as paint and lighting are then added.

Famous suspension bridges

The Akashi-Kaikyo Bridge crosses the Akashi Strait in Japan. Its center span is over 6,500 ft, making it the longest bridge in the world. Until 1998, the longest suspension bridge was the Humber Bridge in England (4,626 ft). 

 The most famous suspension bridge in the USA is the Golden Gate Bridge in San Francisco, with a main span of 4,200 feet. This was the world’s longest bridge up to 1964 when it was overtaken by the Verrazano-Narrows Bridge (main span 4,260 ft) which connects Staten Island and Brooklyn.

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