What Is Cantilever?
Cantilever is basically a structural element that extends horizontally and has supported at only one end. The cantilever is the structures that are fixed at one end and free at another end. Cantilever structures are widely used in the construction of cantilever bridges, cantilever slab, and balconies.
The best example of the cantilever is the chajja in our home. It is supported at only one corner and free at another corner. This types of footings is generally used in the construction of reinforced cement concrete.
Cantilever footing is comprised of more individual columns that are interconnected by a beam known as a strap. In the Strap footing, the strap beam is not in contact with the soil. The Strap beam does not directly transfer the load to the soil. The main function of the strap beam is to transfer the load of the heavily loaded outer column of the Structure to the inner one.
The Strap beam in the Cantilever footing is subjected to the bending moment and shear force. It is very important to design the strap beam in such a way that it will withstand the Bending moment and shear force.
What Is Cantilever Footing?
Cantilever footing is one of the components of the foundation of the building. Cantilever footing is one of the types of the combined footing which consists of two or more column footing which is connected by a concrete beam.
Cantilever footing is also known as Strap footing. In this article, you will get to know about the cantilever footing, its designing, and the situations where the cantilever footings are used. Cantilever footings are constructed with the Reinforced Cement Concrete (R.C.C)
There are two types of Cantilever Footings with the strap.
- Cantilever footings with uniform strap.
- Cantilever footings with non-uniform strap.
Cantilever Footing
A cantilever footing is a component of a building’s foundation. It is a type of combined footing, consisting of two or more column footings connected by a concrete beam. It is used to help distribute the weight of either heavily or eccentrically loaded column footings to adjacent footings
[/su_box]Design of Cantilever Footings
Cantilever footings are the special type of footings which is used for or two columns. The design of the cantilever footing is done by balancing load coming on the footing from the building.
In the case of the cantilever footing, the strap beam connects `two footing designs base bending moments due to external and internal loads of the column
The assumptions which are made while designing Strap or cantilever footing.
- Strap is considered as the pure flexural member, and it does not take any soil reaction.
- Strap is an infinitely rigid member.
Strap beam function is to tie the two different footings with each other. The strap beam transfers the loads by means of the cantilever action. The column of the building, which is located at the boundary of the property line, has an eccentricity loaded footing.
The houses are very adjacent to each other, and there are very less, and congested space is available. Due to which the outer walls are very close to each other. In this case, there is very limited space available due to which isolated footing cannot be provided.
The column which is located at the end of the property line is eccentrically loaded. In such a situation, the cantilever footings are best suitable, which gives Structural stability to the structures without compromising with the aesthetical view of the structures. The main aim of providing the cantilever footings is to counterbalance the asymmetrical loads on the Structure.
Cantilever Action in the Structures
The structural components of the buildings are supported at both ends for proper support to the loads coming on the Structure. But in some situations, the overhanging Structures like sunshade and balconies are needed to construct.
The cantilever structural elements are used, which are supported at one end and free at another end. The load transferred in the cantilever footings from one footing to another one by means of the cantilever action. In the Cantilever footings and Structures, the load is transferred to the end. It is designed in such a way that it will resist the bending moment and shear stress.
When a particular column is located near the boundary of the property line, then it is essential that square or rectangular footing concentrically located under the column, which extends into the adjoining property. In the case of the Cantilever footings, it is necessary that the center of gravity of loads and foundation should coincide with each other in order to transfer the loads uniformly.
Situations Where Cantilever Footing Are Used
When the sufficient area is not available for the foundation to transfer the loads to the underground strata, in such case, the cantilever footings are preferred. Cantilever footings are also used when the soil does not has the good bearing capacity to transfer the loads coming from the structure to the ground, and the size of the footings can be increased beyond the limit.
Cantilever footings are used when the column is constructed near the boundary of the plot, and it cannot be extended further. When the distance between two consecutive columns are very large, and it is not possible to provide combined footing. In that case, Cantilever footing is used.
FAQ: Cantilevers and Cantilever Footings
What is a cantilever?
A cantilever is a structural element that extends horizontally and is supported at only one end. It is commonly used in structures such as bridges, slabs, and balconies, providing support without requiring additional support at the free end.
How does a cantilever work?
A cantilever works by transferring loads from the free end to the supported end, creating a bending moment and shear forces within the structure. The fixed end must be designed to withstand these forces to ensure stability.
What is a cantilever footing?
A cantilever footing, also known as a strap footing, is a type of combined footing that consists of two or more column footings connected by a concrete beam. This design helps distribute the weight of heavily or eccentrically loaded columns to adjacent footings.
When are cantilever footings used?
Cantilever footings are used in situations where:
- Sufficient area for the foundation is not available.
- The soil has a low bearing capacity.
- A column is located near the boundary of the plot and cannot extend further.
- The distance between consecutive columns is large, making combined footings impractical.
What are the types of cantilever footings?
There are two main types of cantilever footings:
- Cantilever footings with a uniform strap.
- Cantilever footings with a non-uniform strap.
How are cantilever footings designed?
Cantilever footings are designed by balancing the loads coming from the building. The strap beam, connecting the footings, is designed to withstand bending moments and shear forces, ensuring structural stability.
What assumptions are made in designing cantilever footings?
The primary assumptions in designing cantilever footings include:
- The strap is considered a pure flexural member that does not take any soil reaction.
- The strap is infinitely rigid.
- The strap beam’s function is to tie different footings together, transferring loads via cantilever action.
What is the role of the strap beam in cantilever footings?
The strap beam in cantilever footings connects individual footings, transferring loads from the heavily loaded outer column to the inner one. It is crucial for counterbalancing asymmetrical loads and maintaining structural stability.
Can cantilever footings be used in congested spaces?
Yes, cantilever footings are ideal for congested spaces where isolated footings cannot be provided. They offer structural stability without compromising the aesthetic view of the structure.
What are the benefits of using cantilever footings?
The benefits of using cantilever footings include:
- Efficient load distribution in limited space.
- Structural stability in cases of eccentrically loaded columns.
- Suitability for low bearing capacity soils.
- Flexibility in design for complex structural requirements.
What is the difference between cantilever action and cantilever footings?
Cantilever action refers to the behavior of a structural element that is supported at one end and free at the other, transferring loads to the supported end. Cantilever footings, on the other hand, are a type of foundation that utilizes cantilever action to distribute loads from columns to footings.
How do cantilever footings handle eccentric loads?
Cantilever footings handle eccentric loads by using the strap beam to transfer the load from the eccentrically loaded column to an adjacent footing, ensuring balanced load distribution and structural stability.
