Stepped Pad Footing.

If the column load is more, or if the safe bearing pressure of the soil is less, the base area found by Eq 3.5 will be large (much greater than b + 2a). In that case, it is necessary to provide masonry offsets, to achieve larger spread, before the load is transferred to the concrete base. The height and width of each offset shold be so proportioned that rate of spread does the stepped footing, in which the rate of spread is n : 1 for masonry an n1 : 1 for concrete, where n = 1/2 for masonry, and n1 = 2/3 for lime concrete an 1 for cement concrete.

In the case of brick pillar, the offsets should not exceed 5 cm. In the case of masonry pillar, the offset may vary between 10 to 15 cm corresponding to the step height of 15 to 22.5 respectively.

FIG. 3.5 STEPPED PAD FOOTING.

The depth of concrete block is given by

where q and m are in the same units (i.e. in kg/cm^2 or t/m^2 or kN/m^2), and d and a are in the same units
(i.e. in cm or m ro mm).