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A concrete column caries an axial laod of 450 kN and a bending moment of 60 kM m at its base. An isolated footing of size 2m by 3m, with 3m side along the plane of the bending moment, is provided under the column. Centres of gravity of column and footing coincide. The net maximum and the minimum pressures in kN/m2 on soil under the footing are respectively.
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- 95 and 55
- 95 and 75
- 75 and 55
- 75 and 75
Correct Option: A
Pressure due to load
| = | = | = 75 kN/m2 | ||
| A | 2 × 3 |
Stress at extreme fibre (due to moment) = M/z
| = | × y | I |
= 20 kN/m2
σmax = 75 + 20 = 95 kN/m2
σmin = 75 – 20 = 55 kN/m2
