A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. There are many different designs that all serve unique purposes and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed, the material used to make it and the funds available to build it.
The first bridges were made by nature itself — as simple as a log fallen across a stream or stones in the river. The first bridges made by humans were probably spans of cut wooden logs or planks and eventually stones, using a simple support and cross beam arrangement. Some early Americans used trees or bamboo poles to cross small caverns or wells to get from one place to another. A common form of lashing sticks, logs, and deciduous branches together involved the use of long reeds or other harvested fibers woven together to form a connective rope capable of binding and holding together the materials used in early bridges.
Bridges can be categorized in several different ways. Common categories include the type of structural elements used, by what they carry, whether they are fixed or movable, and by the materials used.
Bridges of Spain
The Bridges of Spain 2013 issue by Spanish Correos is made up of two stamps depicting a modern suspension bridge, Puente de Sancho el Mayor (Navarra), and another of Roman origin, the Puente de Puentecillas (Palencia).
The Bridge of Sancho el Mayor, in Navarra, crosses the river Ebro and is part of the A-15 highway. It was built in 1978 by civil engineers Javier Manterola and Leonardo Fernandez Toyano and as a cable-stayed bridge. It has a total length of 204 meters, a width of 29 m and a main light span of 142 m, to which are added two side openings on the left bank of the river. It was built with precast keystones using the “cantilever” technique (the bridge is constructed in outward projections that are added on). This suspension bridge is supported on a single pier located on the axis of the road with 35 pairs of twin cables. At the time it was built it was one of the most innovative bridges in design and materials.
A typical cable-stayed bridge is a continuous girder with one or two towers erected above piers in the middle of the span. From these piers, cables are attached diagonally to the girder to provide additional support. Engineering wise they stand in between counter steel bridges and suspension bridges. This type of bridge began to be built in the late 19th century and its use was widespread after World War II, thanks to the technical development of the construction materials and the structural empowerment via computers.
Over the river Carrion in the city of Palencia stands the historic Puente de Puentecillas, the oldest bridge in town. Its original layout dates back to Roman times and it has undergone many changes since the 11th century, the most important of which took place in the 16th century when the current outline of the bridge was set and the remains of the Roman bridge disappeared. It stands in the city center close to the Cathedral and other monuments and has become a popular walking area with plenty of green spaces.
At the entrance of the bridge is the famous Bolo de la Paciencia, where washerwomen leaned their baskets of clothes while chatting. For years it has been a town’s meeting place.
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