Balanced Cantilever Bridge
Cantilever bridge is a bridge where two cantilevers arms projecting in their opposite direction are Connected while attached to solid foundation, that is by counterbalancing each arms. The counterbalance arms are called Anchor Arms.Balanced Cantilever Bridge is so named due to its method of construction.
In nineteenth century , engineers discovered that providing supports for a continuous bridge would distribute the load among them by creating low stresses in Girder which eventually lead to construction of long span bridges. To have a statically determinate structure hinges were used in a multi-span bridge, which had also had the advantage to handle differential Settlement of foundation.
If a bridge is constructed with a continuous span bending moments will be reduced, so longer individual spans can be constructed. But for this the supports should be unyielding, if not(they settle) net moments get altered in magnitude creating distress within the the structure. This is when the bridge with the superstructure known as Balanced Cantilever comes into play with the combination of Cantilevers and suspended spans.
It is one of the most efficient methods of building bridges without the need of false work.. This method has great advantages over other forms of construction in urban areas where temporary shoring would disrupt traffic and services below, in deep gorges, and over waterways where false-work would not only be expensive but also a hazard. Construction commences from the permanent piers and proceeds in a “balanced” manner to midspan as shown.
These bridges are built in sections ,ie section by section.
Howrah Bridge
Qubec bridge
Minatoa bridge
Forth Bridge
Tokyo gate bridge. are few cantilever bridges in the world.
*images from US marines
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