WHICH TYPE OF LOAD ARE AFFECTIVE TO FOUNDATIONS

There are three types of loads on the foundations: 
1. Dead load
2. Live load
3. Wind load

1. Dead load : 
This is the load of the material used for the various components of a building such as walls, floors, roofs etc. All permanent loads are thus included in the dead load. Sometimes, the provision for the future construction of a partition wall is made by allowing a dead load of 10 kg/sqm of the floor area. It should be seen that the dead load of partitions constructed in future under this provision does not exceed the allowance made. 

2. Live load : 
This is the movable load on the floor and hence it is variable. It is also sometimes known as superimposed load. It includes the load of persons standing on the floor, weight of snow on a roof etc. For the purpose of Design. The Live load is converted into equivalent dead load. Following table 1 gives the values of equivalent dead loads for floors of different types of buildings. Further, a percentage reduction is applied in the Design of piers, columns, walls and foundations of the multistorey building as shown in table 2. This reduction is not applied for factories, warehouses, garages, stores, etc. Which are designed for a live load less than 500 Kg/ sqm.

3. Wind load : 
In case of tall buildings, the effect due to wind should be considered. The exposed sides and roofs of such buildings are subjected to wind pressure and its effect is to reduce the pressure on the foundation on the windward side and to increase the pressure on the foundation on the leeward side. Following points should be noted in this connection: 

  1. The pressure will depend on the velocity of the wind. The relation between wind pressure and wind velocity is generally expressed by the formula.                                            P = 0.0075 v2.                                      Where, P = wind pressure in kg/sqm.                       V = velocity of wind in km p.h.    Thus, For the wind of velocity 80 km p.h    P= 0.0075 x (80 x 80). =  48 kg/sqm.            It may noted that the formula will be of no use at places where velocity of wind is uncertain.
  2. If the height of the building is less than twice of its effective width, the wind pressure may be neglected in certain situations.
  3. If the amount of bearing pressure due to wind only is less than 25 percent of that due to dead loads and live loads, the wind pressure may be neglected in the design. 
  4. The effect of wind pressure on a pitched roof depends on the angle of inclination. Usually, the maximum wind pressure bis taken as equal to 3.66 kg/sqm per degree of inclination of roof to the horizontal.

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