Basics in Building Construction

Basics in Building Construction 4(2+2)

Lesson 02 : Shallow Foundations

Functions Of Foundation

Safety and stability of a building depends upon the quality of foundation. It should transmit the dead and imposed loads to the sub-soil uniformly so that the pressure on it will not cause settlement that can weaken the stability of the building. The foundation should be located in such a way that its performance will not be affected in long run due to any unexpected internal and external influences and factors. In order to safeguard the building against damage or distress that can be caused by various factors; the foundation serves the following purposes.

1. Reduction of Load Intensity
   Foundations distribute the loads of the super structure, to a larger area so that the intensity of the load at its base (i.e. total load divided by the total area) does not exceed the safe bearing capacity of the sub-soil.
2. Even distribution of load
   Foundation distributes the non-uniform load of super structure evenly to the sub-soil. For example, two columns carrying unequal loads can have a combined footing which may transmit the load to sub-soil evenly with uniform soil pressure. Due to this, unequal differential settlements are minimized.
3. Provision of level surface
   Foundation provide leveled and hard surface over which the super-structure can be built.
4. Lateral stability Foundation anchors the super-structure to the ground, thus imparting lateral stability to the super-structure. The stability of the building, against sliding and overturning due to horizontal forces (such as wind, earthquake etc.) is increased due to foundation.
5. Safety against undermining
   Foundation provides the structural safety against undermining or scouring due to burrowing animals and flood water.
6. Protection against soil movements
   Special foundation measures prevent or minimize the distress or cracks in the super-structure due to expansion or contraction of the sub-soil because of moisture movements in some problematic soils.