**Footing Design Calculations – Shallow Foundation**

**Determination,**

- Area of Footing (a)
- Depth of Footing (d)
- Short form of Footing Designs

## Footing Designs Calculation – Shallow Foundation:

Footing Designs Calculation

#### Bearing Capacities of the Shallow Foundation from SPT:

Allowable bearing capacities of various foundation beds, (tsf) |

Remark:Soils unable to carry 2000 psf generally requires pilling.

### Design procedure of Isometric Footing:

- Step 1:
*Determination of area of the Footing*

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**P**= 225

^{k};

**q**=

_{u}**2.5**ksf

**Total Load**)/(

**Bearing Capacity**).

**P**+

**Load of footing**)/(

**Bearing Capacity**).

**P***

**1.1**)/

**q**.

_{u}**225***

**1.1**)/(

**2.5**)

**99**ft

**≈ 100 ft.**

**[Assuming, self-wt. of the footing 10%]**

*Total load = P+(10/100)*P = P(1+0.1)*

**B**=

**√100**=

**10**

**ft.**

**“10 ft X 10 ft”**

**100 Sq Ft.**

- Step 2:
*Determination of Depth of the footing*

* ***Punching Shear Check**

Area of punching shear (Elevation) |

Perimeter, ** P_{0}**(for square footing) =

**{(d +b) + (d +b)} * 2**

**= 2 (d +b) * 2**

**=4 (d +b) **

** P_{0}** (for rectangular footing) =

**2(b_1 +b_2) + 4d**

So the resisting punching load = *P*_{0}.d. 100⁄1000

= **4 (d +b) * d * 100⁄1000**

= **4 (18 +15) * d * 100⁄1000**

= **237.6 ^{k} > 225^{k}**

Some loads can be deducted from the actual load to reduce the depth of the footing which brings economy by ensuring safety.

^{2}+ 2.75

^{2})} * 2.25 = 208 ksf

**Assuming**,

**d = 18**inch;

**(18+15)**=

**33**inch =

**2.75**ft]

^{k}

**80<(Modified Load)/(P’ * d)<90 = 80 <(205 * 1000)/( 4(b+d) * d)<90**

## Short form for designing the footing:

**80 <(225 * 1000 * 0.9)/( 4(b+d) * d)<90**

**80 <(225 * 1000 * 0.9)/({2(b_1 + b_2 )+ 4d}* d)<90**

#### Determination of Moments:

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Land Surveying & Architects

Land Surveying & Architects