Cantilever beam can be defined as a beam which is supported on only one end. That means one end is fixed and the other end is exposed beyond the support. The beam transfers the load to the support where it can manage the moment of force and shear stress. Moment of force is the tendency of a force to twist or rotate an object. Shear stress is defined as stress which is applied parallel to the face of a material.
In other words, the beam carries a specific weight on its open end as a result of the support on its enclosed end, in addition, to preventing breaking down as a result of the shear stress, the weight would generate on the beam structure. Cantilever construction allows for overhanging structures without external bracing/support pillars. Cantilever beams can also be constructed with trusses or slabs.
Advantages of a cantilever beam
1- Very simple to construct.
2- Only one fixed support is required, support on the opposite side is not required.
3- This types of beams create a negative bending moment, which can help to counteract a positive bending moment created elsewhere. This is particularly helpful in cantilevers with a back span where a uniform load on the back span creates positive bending, but a uniform load on the cantilever creates negative bending
4- The span can be greater than that of a simple beam because a beam can be added to the cantilever arms.
5- Because the beam is resting simply on the arms, thermal expansion and ground movement are fairly simple to sustain.
6- Cantilever beams are very rigid, due to their depth.
Disadvantages of a cantilever beam
1- Large deflections.
2- Generally results in larger moments.
3- You either need to have fixed support or have a back span and check for the uplift of the far support.
4- when the beam is loaded at one end, the moment at the fixed end is higher, if more load is applied, it can break free from the support.