CLASSIFICATION OF THE FOUNDATIONS AND FACTORS AFFECTING THE SITUATION FOR USE OF THE TYPICAL ARRANGEMENTS ADVISED BY THE IS :1080--1962

DESIGN OF FOUNDATION:--The choice is usually made from experience but it is advisable to carry out a comparative study of the different designs required to determine the most suitable and economical foundation, as the foundations are structural elements that transfer loads from the building or individual column to the earth . If these loads are to be properly transmitted , foundations must be designed to prevent excessive settlement or rotation , to minimise differential settlement and to provide adequate safety against the sliding and overturning effect.Most foundations may be classified as follows :-- (1) Isolated footing under individual column,these may be square , rectangular or circular in plan .(2) Strip foundation and the wall footings.(3) Combined footings supporting two or more column loads .These may be rectangular or trapezoidal in plan or they may be isolated bases joined by a beam .The latter case is referred to as a strap footing.(4) Raft or mat foundation is a large continues foundation supporting all the columns of a structure.This is normally used when soil conditions are poor or differential settlement is to be avoided .(5) In pile foundations pile caps are used to tie a group of piles together .These may support isolated columns, or groups of several columns or load bearing walls .As for as the choice of the type of foundation to be used for the structure in a given situation and position of the structural elements required for transfer of loads it depends on the number of factors for example (a) bearing capacity of the soil (b) type of structure (c) type of loads (d) permissible differential settlement,and (e) economy .