**BBS of footing and estimation of Steel quantity,Footing bar bending schedule BBS and Steel quantity required for footing**

● **introduction** :- in this topic we know about BBS of footing and estimation of Steel quantity reinforcement used in footing. We know that footing is very important work for foundation which transfer load acting on column safely to the bed of soil.

When we start our project first starting and most important work to make design of footing and how to make BBS of footing and estimation of Steel quantity and how much quantity of reinforcement required.

If you calculate quantity of steel required for footing you will give order and purchase Steel quantity according to requirement, as you know extra amount of Steel get corrosion when laying in open environment that is damage of reinforcement so we should buy steel according to requirement and BBS of footing help you to know how much quantity of steel required for your footing work and for your project. in this topic we discuss about BBS of isolated footing.

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**1) calculate self load of column**

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**3) calculate slab load per square metre**

**4) calculate dead load of brick wall per metre**

**5) ultimate load carrying capacity of column**

● **isolated footing :**– isolated footing is defined as the footing which are applied beneath the column in the soil to redistribute the load coming on the columns safely to the bed of soil. Isolated footing is of single column, it will be in various shape like rectangular shape, square Shape, trapezoidal shape. But in this topic we discuss about trapezoidal shape of isolated footing.

**BBS ( bar bending schedule) of footing**

In given diagram there is cross sectional area containing x axis along the horizontal direction and the y axis along the vertical direction.

There is two types of Steel provided in footing work first is main bar which will be provided along Y axis and second one is distribution bar which will be provided along X axis.

**● in this topic we have to determined following**

1) number of main bar used along y axis

2) number of distribution bar used along x axis

3) cutting length or effective length of single main bar used along y axis

4) cutting length or effective length of single distribution bar used along x axis

5) estimation of reinforcement requirement in BBS of footing

**Suppose we have given following data**

Length of footing (X)= 1500 mm ( x-axis)

Width of footing (Y)= 1200 mm ( y -axis)

Diameter of main bar Dm = 12mm

Diameter of distribution bar Dd=12mm

Clear cover at all side C = 50mm

Thickness of footing H= 300 mm

Spacing between main bar Sm = 150 mm

Spacing between distribution bar Sd= 150 mm

**●1) number of main bar used toward y axis**

Nm= number of main bar ?

Sm = spacing = 150 mm

Width along Y = 1200 mm

We have formula to calculate number of main bar

Nm =( width/spacing)+1

Nm =( Y/Sm) +1

Nm = (1200mm/150mm)+1

Nm = 8 +1 = 9 nos

**●2)number of distribution bar used toward X axis**

Nd= number of distribution bar ?

Sd = spacing = 150 mm

Width along X = 1500 mm

We have formula to calculate number of distribution bar

Nd =( length/spacing)+1

Nd =( X/Sd) +1

Nd = (1500mm/150mm)+1

Nd = 10 +1 = 11 nos

**calculate cutting length of single piece of main bar for footing**

Cm1 = cutting length of single piece of main bar

We have formula for calculating cutting length of single piece of main bar

Cm1= (length of footing _ 2 cover) + 2(H _2 cover) _ 2( bend)

Where we have

Length of footing y = 1500 mm

Cover = 50 mm

Thickness H = 300 mm

Bend = 2dm if bend is given at the 90 degree angle dm means diameter of main bar

Cm1 = (1500 _2×50) + 2(300_2×50) _2(2×12)

Cm1 = (1500_100) +(600_200)_48 mm

Cm1 = 1400 +400_48 mm

Cm1 = 1800 _48 mm

Cm1 = 1752 mm = 1.752 mm

**calculate total cutting length of main bar in footing**

Cm = total cutting length of main bar

Cm = No.of nos × cutting length of one main bar

Cm = Nm × Cm1

Cm = 9 × 1.752 meter = 15.768 meter

**weight calculation of main bar in footing**

We have formula for the weight calculation of main bar in Kilogram per metre

Weight = (D^2/162)×L

We have Dm = diameter of main bar is 12 mm and length is 15. 768 meter

Weight =[ (12×12)/162]×15.768 kg/m

Weight of main bar Wm = 14.016 kg

** calculate cutting length of single piece of distribution bar in footing**

Cd1 = cutting length of single piece of distribution bar

We have formula for calculating cutting length of single piece of distribution bar

Cd1= (width of footing _ 2 cover) + 2(H _2 cover) _ 2( bend)

Where we have

Width of footing y = 1200 mm

Cover = 50 mm

Thickness H = 300 mm

Bend = 2Dd if bend is given at the 90 degree angle dm means diameter of distribution bar

Cd1 = (1200 _2×50) + 2(300_2×50) _2(2×12)

Cd1 = (1200_100) +(600_200)_48 mm

Cd1 = 1100 +400_48 mm

Cd1 = 1500 _48 mm

Cd1 = 1452 mm = 1.452 mm

** calculate total cutting length of distribution bar in footing**

Cd = total cutting length of distribution bar

Cd = No.of nos × cutting length of one piece distribution bar

Cd = Nd × Cd1

Cd = 11 × 1.452 meter = 15.972 meter

**weight calculation of distribution bar in footing**

We have formula for the weight calculation of distribution bar in Kilogram per metre

Weight = (D^2/162)×L

We have Dd = diameter of distribution bar is 12 mm and length is 15. 972 meter

Weight =[ (12×12)/162]×15.972 kg/m

Weight of distribution bar Wd = 14.2 kg

**calculate total requirement of reinforcement (steel) for the BBS of footing**

Total weight = Wm + Wd

Total weight = 14.016 kg + 14.2 kg

Total weight = 28.216 kg