Design of Shallow Foundation (Isolated Footings)

Design a square footing for a column size of 400x400. The compression axial load for the load combination of (1.5 DL + 1.5 LL) is 2000 KN. The safe soil bearing capacity is 150 KN/m2 at a depth of 2 metres below E.G.L. Participants are free to go for either a tapered or stepped footing. Besides the total axial load, also account for the self-weight of the footing and soil above it. Assume M25 concrete grade. Do the following checks:

If the gross bearing pressure under the footing is within safe bearing capacity

Provide sufficient depth and longitudinal steel for resisting bending and shear

Sufficient anchorage for column steel into the footing

If the bearing pressure at column-footing joint is within 0.45 times the maximum concrete compressive strength

Provide a simple sketch showing the size of the footing, maximum and minimum depth of the section, flexural reinforcement in both directions and anchorage of column steel.

Please do go through the solved examples in the document provided with the challenge.

Aim- designing a footing for a column size of 400x400.

Given Data-

Column size = 400x400

Compression axial load P = 2000 KN.

Fck = M25

Fy = Fe500

Soil bearing capacity = 150 kn/m²

Procedure –

Gross Soil Pressure And Footing area

Unfactored load with surcharge + self weight of the footing / allowable soil pressure

10% of the load is taken for self weight.

= (2000/1.5 x 1.1)/150 = 9.77m²

We assume a square footing.

Therefore,

Square root of 9.77m² = 3.12m each side.

Net soil pressure and depth of the footing.

Factored load / actual area of footing.

2000 / (3.2 x3.2)

= P_n = 195.3 kN/m²

Assume the depth of the footing 500 mm.

Check it for bearing stress as per IS 456-2000 clause 34.4.

Answer.