Cable-stayed bridges may resemble suspension bridges in appearance; both feature highways suspended from cables and towers. However, the two bridges sustain the highway load in completely different ways. The distinction is in how the cables are attached to the towers. On a suspension bridge, the force of the wind or other loading on the cables is transferred through mechanical links or rods to vertical posts called hangers. The ends of these posts rest on top of the trusses that support the deck of the bridge. By contrast, in a cable-stayed bridge, the force of the wind or other loading is taken directly by the tower itself. There are no hangers under the bridge deck.
In conclusion, suspension bridges and cable-stayed bridges are very similar structures used for roadways, but they use different methods of support. While both types of bridges transfer loads from the roadway to the surrounding structure, they do so using different mechanisms. If you were to compare every single feature of these bridges, you would find many similarities as well as differences. For example, both suspension bridges and cable-stayed bridges are usually long enough to carry traffic across large bodies of water. They also have similar design requirements such as strength and stability. Finally, both types of bridges require extensive engineering studies before they can be built.
Cable-stayed bridges use less cable than suspension bridges, may be built using equivalent pre-cast concrete sections, and are faster to build. The end product is a low-cost bridge that is unquestionably gorgeous. Cable-stayed bridges can be more expensive than suspension bridges of comparable size because they require more material and labor for construction.
Suspension bridges are the most common type of bridge. They work by suspending an arch of wire or steel between the ends of the towers that support it. The force of gravity keeps the bridge up. Suspension bridges are very stable, but they cannot cross large bodies of water. This is why people often call them "dry bridges".
Truss bridges are another kind of bridge that uses triangles instead of arches to support its load. Each triangle is made up of three pieces of wood or metal connected with hinges so that they can move independently from one another. When weight is put on any one point on the side of the truss opposite the hinge, the other two points spread the load out evenly over a larger area. This prevents the bridge from bending in one place.
Toll bridges and tunnels are similar to each other in that both charge a fee for traffic to pass through them. Toll bridges take advantage of existing overpasses and underpasses while tunnels require their own set of supports.
The fundamental distinction between the two types of bridges is the method through which the weight of the road deck is borne. The cables that hold the road deck of suspension bridges, such as the Golden Gate Bridge, are joined to main cables that drape over the towers and are anchored at both ends of the bridge. As traffic passes over the cables, the movement of the vehicles causes the cable to stretch or compress, which in turn changes the distance between its two anchors at each end of the bridge.
Suspension bridges like this one use hydraulic rams to maintain the tension in the cables when there is no load being carried by the bridge. This allows the bridge to remain in a horizontal position even when traffic crosses it.
When a vehicle crosses a suspension bridge, its weight will cause the cables to stretch or compress depending on the weight of the vehicle. If the weight of the vehicle is great enough, it will pull the cables down further, causing the ram on the opposite side of the tower to push up against those cables with enough force to keep them taut. This mechanism permits the road surface under the bridge deck to be kept perfectly level even when heavy vehicles pass over it.
Mechanical bridges, such as beam bridges and truss bridges, use girders or beams that span between towers or poles and carry the weight of the road bed and any passengers crossing it.