The compressive stresses at supports, for example, at the base of column, must be transferred by bearing. Clause 34.4 of IS 456 stipulates that the permissible bearing stresses on full area of concrete in the working stress method can be taken as 0.25fck, and for limit state method it may be taken as 0.45fck.
Clause 34.4 – Transfer of load at column base.
The compressive stress in concrete at the base of a column or pedestal shall be considered as being transferred by bearing to the top of the supporting pedestal or footing. The bearing pressure on the loaded area shall not exceed the permissible bearing stress in direct compression multiplied by a value equal to ,
A1 = supporting area for bearing of footing, which in sloped or .stepped footing may be taken as the area of the lower base of the largest frustum of a pyramid or cone contained wholly within the footing and having for its upper base, the area actually loaded and having side slope of one vertical to two horizontal.
A2 = loaded area at the column base.