Santiago Calatrava has always thought of a bridge as an artistic endeavor. His initial attempt to construct a single pylon bridge fell through, but he was afforded the opportunity to try again. This time he met with success, his bridge at Alamillo in Seville, Spain has become the forerunner of a series of similar bridges.
Unlike the Caballeros footbridge, in which the pylon leaned forward in the direction of the bridge, and which was supported by a system of cable stays at the rear of the pylon, Calatrava opted to reverse the direction of the pylon.
It only makes good sense to have the weight of the pylon face in the opposite direction from the load, as that puts the whole assembly into balance. If you will refer to any number of Mr. Calatrava's sculptures, you will note that he has placed very considerable importance on balance. So, why should a bridge be any different?
The pylon for the Alamillo bridge is inclinated at an angle of precisely 58 degrees. Coincidentally, this just happens to be the same angle as that of the great pyramid of Cheops. The height of this pylon is 142 meters. This great height combined with the angle, would need to have a new and different method of construction devised.
The solution was to manufacture the pylon in manageable sections, which were welded up from steel. As one section was lifted onto the next via a crane, reinforced concrete was added to stabilize the assembly as it rose. At the same time the cable places were added as the pylon grown, balancing itself off with the bridge deck.
The 200 meter span length, combined with the angle of the pylon, just happens to make the cable angles identical at both ends.
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