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 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 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.
Design of Cantilever Footings
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.