TUTORIALS

How to Design of Single Column Footing

This will instruct you with the comprehensive procedures for forming or designing a single square column footing.

In this tutorial, an appropriate solution is offered to the subsequent problem:

Form a single column footing by using the subsequent measures:

1. Steel grade is equal to fy is equal to 60 Ksi
2. Column is equal to 14’’ x 14’’
3. fc’ is equal to 4 ksi (for column)
4. fc’ is equal to 3 ksi (for footing)
5. (service dead load) sD.L is equal to 390 Kips
6. (service live load) sL.L is equal to 260 Kips
7. Allowable Bearing capacity is equal to q_a is equal to 6 ksf 5’ below the grade
8. Unit weight of soil = 0.127 k/ft³

A footing refers to an extension of the bottom of a wall or column with the objective to spread the load on the upholding soil at a pressure fulfilling its characteristics.

Footings are set for keeping the forces, functional loads, moments and the stimulated reactions and to ensure that any settlement which could occur should be fully alike and the safe bearing capacity of soil must not exceed.

Calculate effective bearing capacity = q_e = q_a (allowable bearing capacity) – soil fill pressure =
q_e = 6 – (5 x 0.127) [soil unit weight = 0.127 k/ft³] = 5.365 k/ft²
The footing dimension = footing area = service dead load + live load/effective bearing capacity = sD.L + sL.L/q_e = 390 + 260/5.365 = 121.155 ft²

A = 11 ft
Also for strength design, the ascending pressure due to the factored column load is -
q_u = factored load/footing area = 1.6 L.L + 1.2D.L +/footing area
q_u = 1.6(260) + 1.2(390) /11 x 11 = 7.3 k/ft²

The thickness or depth is usually computed according to punching shear or two way on the critical perimeter.
Suppose d = 30’’
Critical perimeter, b_o = 4 x (14’’ + d) = 4(14’’ + 30)
Critical perimeter, b_o = 176 inches

Shear force, V_u = Ascending pressure – that performing in the critical perimeter
1 critical square side = 14’’ + d = 14’’ + 30’’ = 44’’ = 3.667 ft
Shear force, V_u = 7.3(11² – 3.667²) = 785 kips
Then we’ll verify in case d = 30’’ is all right or not?

We’ll verify for punching shear,
Shear strength > Shear force

To learn the design a single column footing, go through the following video tutorial.

Lecturer: SL Khan