Although we know different types of bridges exist, we probably couldn’t name them. Recognising bridge types is helped by knowing a little about bridge construction and its evolution.
The first bridges of earth, stone and logs could only cross short spans. Examples include the beam bridge, stepping stones and primitive log suspension bridges. Once mortar was made by the Greeks and Romans much stronger bridges could be built with much larger spans. The most popular of these was the arch bridge and its variants, the earliest example being the Arkadiko bridge built in Greece around 1300 B.C. The arch bridge is made up of one or several spans with abutments or piers at the ends of the spans. One variation was the aqueduct which was made with two or more stories, each made up of many arches. Pont de Gard is a famous example. A more modern variant is the truss arch bridge which combines a truss bridge, one whose superstructure is in the form of a truss, with an arch bridge. This lightens the bridge’s weight. Iron Bridge is of this type. The Sydney Harbour Bridge is an example of a steel through arch bridge in which the deck carrying the road and railway passes through the arch rather than lying on top of it. China, known for its moon bridges, now has the world’s longest arch bridge, the Chaotianmen Bridge in Chongqing.
Arch bridges are labour intensive to build so suspension bridges, where the load-bearing part is held beneath suspension cables, were constructed including the Clifton suspension bridge. These could not carry heavy weights so cantilever bridges, using a cantilever supported at one end, were built to carry trains in the nineteenth century. Various movable bridges were built to allow ships to pass including, most famously Tower Bridge, and the Middlesborough transporter bridge that could transport vehicles above the water. Box girder bridges were built for flyovers and segmental bridges in which pre-cast segments are slotted together and a superstructure added above have been built to carry, for example, the elevated section of the Delhi metro. Other self-descriptive bridge types include the bowstring arch bridge, the covered bridge, the trestle bridge and the tubular bridge.
Many bridges give their location an identity giving impetus to architects to come up with innovative designs such as that of Maldonado bridge in Uruguay, an example of a stressed ribbon bridge.