Answer by Rakshita Nagayach:
Case I : One way Shear
In this case, the dispersion angle of load is 45° as shown. According to IS 456:2000, 'the critical section for this condition shall be assumed as a vertical section located from the face of the column,pedestal or wall at a distance equal to the effective depth (d) of footing for footings on piles.'
X-X is the Critical Section.
Case II: Two way Shear
If footing depth is less, the column may punch through the footing. For this tendency, IS 456:2000 recommends that critical section is at a distance d/2 from the column face.
Hope this helps! Sorry for the low quality pictures.
Thanks for the A2A .