Design of Shallow Foundation (Isolated Footings)
Design of Shallow Foundation (Isolated Footings)
Jagadeep.M.M
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.
AIM:
To design a square footing for a column size of 400 x 400 and to provide a sketch showing the size of the footing.
PROCEDURE:
Given data:
Column size = 400 x 400 mm
Soil bearing capacity = 150 KN/mmsq
Compression axial load = 2000 KN
Compressive strength = M25
Size of the footing
- Assume self weight of footing equal to 10% of super imposed load.
Net upward pressure
Depth of footing on the basis of B.M
- By thumb rule we take 2.5 times higher value of d for shear check
Area of reinforcement
Check for one way shear
For one way shear, critical section is located at a distance ‘d’ from the face of the column.
Hence OK for one way shear
Check for two way shear (punching shear)
For two way shear, The section lies at a distance d/2 from the column face all around.
Result:
The desing and size of the footing is designed successfully by using the given details.
