Design of Shallow Foundation (Isolated Footings)

DESIGN OF SHALLOW FOUNDATION (isolated footing)

AIM:-

To create a square footer with the following checks and a 400x400 column dimension under the specified constraints:

• If the safe bearing capacity is met by the gross bearing pressure beneath the footing.
• Adequate anchorage for column steel into the footing; enough depth and longitudinal steel to withstand bending and shearing.
• If the maximum concrete compressive strength is not more than 0.45 times the bearing pressure at the column-footing joint. Further to offer a sketch that illustrates the specific geometric and structural characteristics of the footing.

ITRODUCTION:-

• As the base for the floor walls and columns, footing is a component of the foundation made of concrete or brickwork masonry.
• Transferring vertical loads straight to the soil is the primary purpose of footings.
• Strip/wall footing, spread footing, combination footing, and raft footing are the four primary forms of footing.
• A wall footing, also known as a strip footing, is a continuous concrete strip used to distribute a load-bearing wall's weight over a patch of ground.
• Spread footing is a type of pad that disperses the load of a column to a surrounding region of soil in two directions. It could be tapered, stepped, etc.
• When two columns are positioned near together or when a column is at the edge of the land, combined footing is given.
• When the area of the whole column to the area of the site footprint surpasses 50%, raft footing is supplied for exceptionally weak soil.
• A single footing that shifts the weight to the subsurface soil is known as an isolated footing. When only one column is needed, it is supplied.

PROCEDURE (for given task):-

• Given data:
• Column size 400mmx400mm
• Compression axial load combination of (1.5 DL + 1.5 LL) is 2000KN
• Safe soil bearing capacity at a depth of 2 meters below E.G.L is 150kN/m^2
• Assuming the self-weight of the footing and soil above it as a 10% load
• Grade of concrete=25 kN/m^2
• Assuming fy=415 n/mm^2

Here a slope footing is designed.

• Gross bearing capacity
• Assuming the unit weight of the soil to be 18kN/m^3
• Load on the footing=1333.3kN
• Weight of the footing, g=3.5x3.5x25x0.8=245kN
• Weight of the soil= 3.5x3.5x(2-0.8)=261.6KN
• Total load=1852KN
• Gross bearing capacity= 1852/3.5x3.5=257KN/m^2
• As 257kN/m^2>150KN/m^2, hence we need to increase the size of footing to 3.8mx3.8m
• Now total load=1934KN
• Gross bearing capacity=1934/3.8x3.8=133.9Kn/mm^2
• 133.9KN/m^2<150KN/m^2, hence safe
• Corrected net soil pressure=2000/3.8x3.8=138.5Kn

Placement Plan for Reinforcement Bars

Section of the footing

Result:

Sloped isolated footing for the square column is designed for the given conditions and also checked