We shall build up a small size structure by RR masonry at a certain height but the multi-story building cannot be constructed by RR masonry because the structure can able to transmit the heavy load to the foundation. So in this circumstance, we have to place column which can distribute the load to the foundation.
The foundation has received the all loads like dead load, live load, seismic load, etc., which is distributed to column & it transfer to the ground. The entire pressure of the structure should not greater than the safe bearing capacity of soil (SBC).
The capacity of the soil that supports the structural load to the ground without any shear failure or settlement is called safe bearing capacity of the soil.
Unit weight of the material is simply defined as Mass per Volume (M/V) and also it is called as Unit Weight of material. For better understanding, If a Steel weight 100 Kg (M) then the steel was immersed in water & weighed again (V). Another name of unit weight is called Density.
The minimum depth of shallow foundation formula has invented by Rankine. We shall see some of the building was constructed by the Shallow foundation (Isolated footing, Combined footing or RR Masonry) & some other deep foundation (Mat foundation, Pile foundation) Why?.