The depth of footing for an isolated column is governed by i) maximum bending moment ii) shear force iii) punching shear The correct answer is A. Only (i) B. (i) and (ii) C. (i) and (iii) D. (i), (ii) and (iii)

The correct answer is (i), (ii), and (iii).

The depth of footing for an isolated column is governed by the following factors:

• Maximum bending moment: The bending moment at the base of the column is the most critical factor in determining the depth of the footing. The bending moment is caused by the load from the column and the weight of the footing itself.
• Shear force: The shear force at the base of the column is also a critical factor in determining the depth of the footing. The shear force is caused by the load from the column and the weight of the footing itself.
• Punching shear: Punching shear is a type of shear failure that can occur in footings. It is caused by the load from the column being concentrated at a small area on the base of the footing.

The depth of the footing must be sufficient to resist the maximum bending moment, shear force, and punching shear. The depth of the footing is typically determined by the following equation:

$d = \frac{M}{f_c’ b}$

where:

• $d$ is the depth of the footing
• $M$ is the maximum bending moment
• $f_c’$ is the compressive strength of the concrete
• $b$ is the width of the footing

The depth of the footing must also be greater than the following:

• The depth of frost penetration in cold climates
• The depth of the water table in wet climates
• The depth of any existing foundations