Overview
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Cable-stayed bridges may look similar to suspensions bridges -- both have roadways that hang from cables and both have towers. But the two bridges support the load of the roadway in very different ways. The difference lies in how the cables are connected to the towers. In suspension bridges, the cables ride freely across the towers, transmitting the load to the anchorages at either end. In cable-stayeded bridges, the cables are attached to the towers, which alone bear the load.
The cables can be attached to the roadway in a variety of ways. In a radial pattern, cables extend from several points on the road to a single point at the top of the tower. In a parallel pattern, cables are attached at different heights along the tower, running parallel to one other.
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Cable-stayed bridges are proving popular for spans up to about 800 in and when coupled with approach roads very broad crossings are bridgeable. Precast or in situ concrete or steel box segments may be used for the deck, which is supported by cables and staved to a tower. There are four principle configurations, known as radiating, harp, fan and star systems. These arrangements provide compression in the deck by utilising self-weight. In this way the deck can be made up of individual segments and made to act like a prestressed beam.
Clearly cables can be spaced such that the horizontal component of force cancels out any tensile force in either the top or bottom flange, individual segments can then be assembled one-by-one and left unconnected. In the case of a concrete deck, shear forces would be resisted by shear keys and/or epoxy resin glued joints, whereas steel would normally be welded.
Where the cables are much further apart, then the tensile stresses would have to be removed by prestressing or carried in the flange of a continuous steel box girder. Vertical force components in each cable are transferred to the pylon and carried through to a foundation.
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Cable-stayed
bridge
Parallel
attachment pattern 
Radial attachment pattern