Consider the following statements:

The design depth of the footing for an isolated column is governed by

1. Maximum bending moment

2. Maximum shear force

3. punching shear

Which of the above statement are correct?This question was previously asked in

ESE Civil 2014 Paper 1: Official Paper

Option 3 : 1, 2 and 3

ST 1: Building Material and Concrete Technology

18425

20 Questions
20 Marks
12 Mins

The design depth of footing is based on the following three criteria:

1. **Depth based on maximum BM at the face of column**

For illustration consider square footing of width B resting on uniform soil pressure ‘p’. The maximum BM is

\(M = \frac{{pB{{\left( {B - b} \right)}^2}}}{8}\)

Where b is column size.

The depth is given as

\(d = \sqrt {M/Rb} \)

Where R is designed constant.

2. **Maximum shear at a distance of d from the face of the column, where d is the effective depth of footing.**

\(Nominal\;shear\;stress = \frac{V}{{Bd}}\) < permissible one way shear in footing

Using the above equation we can calculate d.

3. **Based on punching shear stress at a distance of d/2 from face of column, where d is the effective depth **

\({\rm{Punchings\;shear\;stress}} = \frac{{{\rm{Net\;punching\;force}}}}{{{\rm{perimeter}} \times {\rm{d}}}} < {\rm{permissible\;puhing\;shear\;stress}}\)

Using the above equation, we can calculate d.