A cantilever bridge has the same function of any other bridge; to span obstacles to provide passage over it for pedestrians, vehicles or railways.
This type of bridge is selected when necessity supports cannot be provided at specific positions, due to the great straining actions.
Here we will learn about cantilever bridge, types of cantilever bridges, advantages and disadvantages of cantilever bridge.
Types of Cantilever Bridge:
Balanced cantilever bridges:
The balanced cantilever bridge is one of the most efficient methods of building bridges without the need for falsework.
This method has great advantages as compared to other forms of construction in urban areas, where temporary shoring will disrupt traffic and services in the deep valleys below and on waterways where falsework are not only costly but also a hazard.
Construction begins at the permanent piers and proceeds mid-term in a balanced manner.
Continuous cantilever bridges:
The continuous cantilever bridge is a truss bridge that extends across three or more supports without hinges or joints.
It is highly simplified but it will explain the basic concepts, similar to a normal beam.
Analysis of a cantilever span with a back span is illustrated to expose the load distribution.
Cantilever Bridge Advantages and Disadvantages:
- Falsework is not required other than the required for pier.
- Assembled sections of suspended bridges can only be elevated and attached between two cantilever spans.
- Support are required on only one side of each cantilever.
- The bridge floor might be simply formed into sections, which preserve uniformity and ensure high quality.
- These bridges have multiple cantilever spans, construction can be started immediately from all its columns reducing the time required.
- Navigation under the bridge is not interrupted during its construction.
- In areas with a strong rock structure, anchor arms might be connected to the surrounding rock, without the necessity for synthetic support.
- The span of those bridges is longer than conventional beams since the cantilever are attached at the ends of the bridge.
- These bridges can higher withstand the effects of thermal expansion and floor speed than others.
- The lack of supporting piers provides extra flexibility to the styles and geometry of the highway supported by this bridge.
- These bridges are chosen for deep rocky valleys and flood-prone areas, where falsework might be dangerous or difficult.
- Cantilever bridge has to take care of their stability by creating stability between compressive and tensile forces, which requires a heavier structure.
- These bridges experience a high level of tension during their construction known as negative moments.
- These kinds of bridges usually are not appropriate for the areas with excessive climate conditions as a result of lack of multiple seasons.
- Extensive analysis to prevent fatigue failure of elements and welds.
- Disability of the RC floor as part of a composite section.
- These are large-scale structures, which are complex to construct and maintain.
- These bridges are heavy, cantilevers require must be bigger and stronger support columns.
- Large bridges have truss bridges between the two cantilevers to reduce their weight.
- They will not be suited for earthquake-prone areas or areas with low-rock stability.
The cantilever bridge is different from simply supported structures.
Simply supported structures are directly supported at each end, whereas cantilevered structures are directly supported at one end and free at the other end.