How is a cantilever foundation constructed? | 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. This type of beam is called a strap beam. It is used to help distribute the weight of either heavily or eccentrically loaded column footings to adjacent footings.
Essentially, a cantilever footing is used to connect an eccentrically loaded column footing close to the property line to an interior column
Strap or cantilever footings are designed on the basis of the following assumptions:
The assumption that is made for the design are:-
- The strap is infinitely rigid
- The strap is a pure flexural member and does not take the soil reaction. (To conform with this, the strap is constructed slightly above soil or soil under strap is loosened.).
It should be noted that the actual bearing pressures under the footings should not very different from each other in order to minimize differential settlement.
Determine and draw shear force and bending moment diagrams along the length of the footings.
Select depths of footings for shear reinforcement.
Select steel reinforcement for bending requirement.
In short direction, the footings analyzed as spread footing subject to uniform soil pressure.
Design strap as flexural member for the shear and moment obtained above.
- The strap is infinitely stiff. It serves to transfer the column loads to the soil with equal and uniform soil pressure under both the footings.
- The strap is a pure flexural member and does not take the soil reaction. To avoid bearing on the bottom of the strap a few centimeters of the underlying soil may be loosened prior to the placement of concrete.
This is how cantilever footing or cantilever foundation is constructed