Cable-stayed bridge different from suspension bridge
A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge deck. A distinctive feature are the cables or stays, which run directly from the tower to the deck, normally forming a fan-like pattern or a series of parallel lines. This is in contrast to the modern suspension bridge, where the cables supporting the deck are suspended vertically from the main cable, anchored at both ends of the bridge and running between the towers. The cable-stayed bridge is optimal for spans longer than cantilever bridges and shorter than suspension bridges. This is the range within which cantilever bridges would rapidly grow heavier, and suspension bridge cabling would be more costly.
Cable-stayed bridges were being designed and constructed by the late 16th century, and the form found wide use in the late 19th century. Early examples, including the Brooklyn Bridge, often combined features from both the cable-stayed and suspension designs. Cable-stayed designs fell from favor in the early 20th century as larger gaps were bridged using pure suspension designs, and shorter ones using various systems built of reinforced concrete. It returned to prominence in the later 20th century when the combination of new materials, larger construction machinery, and the need to replace older bridges all lowered the relative price of these designs.Comparison with suspension bridge
Cable-stayed bridges may appear to be similar to suspension bridges, but they are quite different in principle and construction. In suspension bridges, large main cables (normally two) hang between the towers and are anchored at each end to the ground. This can be difficult to implement when ground conditions are poor. The main cables, which are free to move on bearings in the towers, bear the load of the bridge deck. Before the deck is installed, the cables are under tension from their own weight. Along the main cables smaller cables or rods connect to the bridge deck, which is lifted in sections. As this is done, the tension in the cables increases, as it does with the live load of traffic crossing the bridge. The tension on the main cables is transferred to the ground at the anchorages and by downwards compression on the towers.Difference between types of bridges
		
			
			
		
		
			
			
		
In cable-stayed bridges, the towers are the primary load-bearing structures that transmit the bridge loads to the ground. A cantilever approach is often used to support the bridge deck near the towers, but lengths further from them are supported by cables running directly to the towers. That has the disadvantage, unlike for the suspension bridge, that the cables pull to the sides as opposed to directly up, which requires the bridge deck to be stronger to resist the resulting horizontal compression loads, but it has the advantage of not requiring firm anchorages to resist the horizontal pull of the main cables of the suspension bridge. By design, all static horizontal forces of the cable-stayed bridge are balanced so that the supporting towers do not tend to tilt or slide and so must only resist horizontal forces from the live loads.
The following are key advantages of the cable-stayed form:Related bridge types
Self-anchored suspension bridge
A self-anchored suspension bridge has some similarity in principle to the cable-stayed type in that tension forces that prevent the deck from dropping are converted into compression forces vertically in the tower and horizontally along the deck structure. It is also related to the suspension bridge in having arcuate main cables with suspender cables, although the self-anchored type lacks the heavy cable anchorages of the ordinary suspension bridge. Unlike either a cable-stayed bridge or a suspension bridge, the self-anchored suspension bridge must be supported by falsework during construction and so it is more expensive to construct.