Expo 92 suspended bridge
The cable-stayed El Alamillo Bridge in Seville is a landmark job in its conception.
The principle on which it works is a balance in which equilibrium is attained by inclining the 132-metre-tall mast at an angle of 58º to the horizontal. The design is by Santiago Calatrava. In its execution the following objectives were reached:
- To cross the basin without any support whatsoever in the middle, so as to integrate the right bank more fully in Seville and leave a vast surface of water unmarred by any obstacle of any kind. The bridge's span is 200 metres, which enters the technical domain of cable-stayed bridges.
- To establish a thoroughly urban connection to mark the stage of technological development that has been reached and to testify as to the state of the art in Spanish construction.
- To build a bridge that would be a symbol of Expo Seville and a new monument worthy of the city.
The mast to which the cables are anchored is a compound structure made of concrete and steel. Its cross section varies, from four metres in diameter from the ground to a height of 76 metres, to two metres in diameter from 76 to 132 metres. The mast's inclination enables the cables' pull to be balanced without using guy cables.
The deck is made up of a metal casing of varying width and 13.20-metre-wide lateral overhangs. The metal casing measures 4.40 metres along its edge, and its cross-section forms a hexagon whose upper and lower wings vary in width from 3.75 metres to 6.394 metres in the upper frame and from 3.246 metres to 5.89 metres in the lower frame. The overhangs are built with metal ribs set four metres apart holding a reinforced concrete slab on top, built with prefabricated 10-cm-thick plates with 13 centimetres of concrete laid on site on top of the plates. The deck is anchored to the mast by 13 pairs of parallel cables that spring from the edges of the central metal casing.