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A cantilever beam is an inflexible structural component held at one end and free at the other end.
The cantilever beams can be either prepared of concrete or steel whose one end is bound or tied up to a vertical support. It is a horizontal beam structure whose free end is opened to vertical loads.
1. Cantilever Beam
In a building, a cantilever is built as an addition to a continuous beam, and in bridges, it is part of a cantilever girder. It can be built either cast-in-situ or by dividing construction by pre-stressing methods.
Cantilever construction permits overhanging structures without extra supports and bracing. This structural component is majorly utilized in the construction of bridges, towers, and buildings, and can attach a special appearance to the structure.
This article describes a few main structural actions and basic concepts of a cantilever beam in construction.
2. Structural Behaviour of Cantilever Beam
A cantilever beam moves downwards when it is loaded to vertical loads. A cantilever beam can be put through a point load, uniform load, or varying load.
Ignoring the type of load, it moves downwards by making a convexity upwards. This movement makes tension in the upper fiber and compression in the lower fibers. Hence major reinforcement is given to the upper fiber of the concrete beam, as there is high tensile stress.
3. Design of Cantilever Beam
A cantilever beam under the action of the structural load is put through the moment and shear stresses. The aim of any design process is to transfer these stresses safely to the support.
The bending moment of a cantilever beam differs from zero at the free end to the highest value at the fixed-end support. Hence during the preparation of cantilever beams, the major reinforcement is given to the upper fiber of the concrete beam to resist the tensile stress safely.
The major span of a cantilever beam is reliable on the following factors noted below:
a. The depth of the cantilever
b. The magnitude, type, and location of the load
c. The quality and type of material used
For cantilever beams, having a small span is limited to 2 to 3 m. But the span can be extended either by extending the depth or using a steel or pre-stressed structural unit.
The span can be prepared long, given that the structure can prevent the moments produced by the cantilever and safely transmit it to the ground.
The detailed investigation and design of the structure can be useful for studying the feasibility of long-spanned cantilever beams. The cantilever beam should be properly connected to the wall or support to decrease the effect of overturning.
4. Applications of Cantilever Beam in Construction
Cantilever beam structures are used in the following applications:
a. Construction of cantilever beams and balconies
2. Temporary cantilever support structures
3. Freestanding radio towers without guy wires
4. Construction of cantilever beam for pergolas
5. Lintel construction in buildings.
5. Formula of Cantilever Beam
The formula used in the analysis of the beam for the cantilever:
6. Advantages of Cantilever Beams
The important advantages of cantilever beams are:
a. Cantilever beams do not need any support on the other end.
b. The negative bending moment raised in cantilever beams use to prevent the positive bending moment raised.
c. Cantilever beams can be easily built.
7. Disadvantages of Cantilever Beams
The disadvantages of cantilever beams are:
a. Cantilever beams are put through huge deflections.
b. Cantilever beams are put through larger moments.
c. Strong fixed support or a back span is needed to make the structure balance.
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