Process for isolated footing design for foundation

Given below the step-by-step process for structural design of isolated footing.

As for example, take an isolated footing for an RCC column having size 450mm x 450mm. Loads delivered from this column to the foundation are Vertical Load: 1000 kN and Uniaxial Moment: 100 kNm

The safe bearing capacity (SBC) of soil is 300 kN/m2. The grade of concrete should be M30 and grade of steel should be Fe415.

Step -1: Defining size of footing: Loads on footing comprise load from column, self weight of footing and weight of soil above footing. For easiness, self weight of footing and weight of soil on footing is taken as 10 to 15% concerning the vertical load.

Load on column = 1000 kN

Extra load at 10% of load because of self weight of soil = 1000 x 10% = 100kN

So, total load P = 1100 kN.

Size of footing is square, rectangular or circular in plan for designing purpose. Here square isolated footing is taken.

So, length of footing (L) = Width of footing (B)

Consequently, area of footing needed = 1100/300 = 3.67 m2

Provide Length and width of footing = 2m

Download Isolated Footing Design Excel Calculation

Area of footing = 2 x 2 = 4m2

Now the pressure on isolated footing is measured as

Ref.: theconstructor.org

When computed, pmax = 325 kN/m2

pmin = 175 kN/m2