A cantilever bridge is one of the five basic types of bridges, along with arch, beam, cable-stayed and suspension bridges. The cantilevers support both the compression and tension forces of the bridge through their strong internal skeleton and hinges. The main advantages of a cantilever bridge are that it does not need a support beam in the middle and it can be constructed without falsework (temporary structures to hold the bridge in place during construction).
Suspended Span Cantilever Bridge
A suspended span bridge has two cantilever arms that do not meet, but instead support a truss bridge located in the centre. The cantilever arms distribute the tension force evenly along the span. They are also connected with specialised hinged girders to two support beams at either end of the bridge, which distribute the compression force to the ground.
Balanced Cantilever Bridge
A balanced cantilever bridge has arms projecting in both directions from the support beams. The cantilever arms meet in the centre and support the main span. They are counterbalanced by anchor arms that project in the opposite direction and are attached to a solid foundation. The foundation absorbs the tension and compression forces.
Truss Arch Bridge
Steel bridges can be built without the use of anchor arms in places where the surrounding rock can be used to support the tension during construction. Two pure cantilever spans are joined in the centre with a pin. When decking is added the bridge becomes a combination truss and arch bridge. The Navajo Bridge is an example of a truss arch bridge built with cantilevers.