# Bar Bending Schedule of Column | Rectangular and Circular Column

The column is a verticle structural member which takes loads from the beam and slab and transfers it to the foundation and finally to the soil. Bar bending schedule of column means simply to calculate the quantity of steel rod used in the column with withstand safely.

I have also written an article on Complete RCC column design Guide – Numerical Example as per IS Code. Now let us move toward the calculation of reinforcement of column.

## A) Bar Bending Schedule of Rectangular Column

#### Before the Bar Bending schedule of the column, I would like to tell you some points to be remembered.

1. We know the standard size of the steel bars is 12 meters. So, after that, we have to add other rods if required more height of length.
2. Keep in mind that the steel rod should not be tied at the place where the bending moment is high. Its means at the top or bottom of the column. We should always prefer to lap the steel rod at the mid-span or nearly mid-span of the column or any structure.
3. The lapping should be done in an alternate way of the steel rod.
4. Sufficient lapping should be provided as per IS code to maintain safe as well as economical.

From the diagram,

Thickness of Slab = 125 mm

Thickness of Footing = 350 mm

Clear Height of floor = 3000 mm

Let, Column has 6 numbers of 20 mm dia bars

Development Length =  50d =50 x 20 = 1000 mm

8mm stirrups @ 150 mm C/C

Footing Clear Cover = 40 mm

#### Step 1 – Find the length of Vertical Bar

Formula,

Length of Vertical bar = Development length (Ld) + Depth of Footing + 2 x Clear Floor Heights + 2 x Slab Thicknesses + Overlap Length – Bend Length

= (50×20) + 350 + (2×3000) + (2×125) – (2×20)

= 7560 mm = 7.560 meter

Here, Overlapping Length should not considered because the standard size of steel rod is found to be 12 meter. But we require only 7.56 meter.

So,

Cutting length is equal to the total length of vertical bars calculated above.

If the steel rod were more than 12 meter then, overlapping length would be added.

By the way lets see how to calculate the over lapping length of steel rod of column.

#### Step 2 – Find out lapping

As we know that lapping length required is taken 50d = 50 * Diameter of the bar = 50×20 = 1000 mm.

Keep in Mind

1. Never overlap bars in a column at the top & bottom.
2. Lapping should be done at alternate bars.
3. Top bars should be always lapped with bottom bars.

#### Step 3 – Cutting Length of Stirrups

Formula,

Cutting length of Stirrup = Perimeter of stirrup + Length of Hooks – Length of Bends

Perimeter = 2 x {Length of Column – Clear Cover) + (Width of Column – Clear)}

P = 2 x  {(500– 25) + (300 – 25)}

P = 1500 mm

Length of Bends = 3 x (2 x 20) + 2 x (3 x 20) = 240 mm

Length of One Hook = 9d = 9 x 20 = 180 mm (As per IS)

Therefore,

Cutting length of Stirrup (L) = Perimeter of stirrup + Length of Hooks – Length of Bends

(L) = 1500 mm + 180 mm – 240 mm

(L) = 1440 mm

Cutting length of Stirrup = 1440 mm

#### Step 4 – Number of Stirrups

Number of stirrups required = Total Length of Vertical bars/Spacing of stirrups+ 1

Number of stirrups required = (7560/150) + 1

= 51.4 Number of stirrups    Say, 52 Nos.

#### Step 5 – Bar Bending ScheduleTable

Use the formula to calculate the weight of the steel rod as I have told you in Part-1 of the Bar Bending Schedule.

## B) Bar Bending Schedule for Circular Column

#### Step 1 – Find the length of Vertical Bar

Given,

Diameter of column = 300 mm

Diameter of Main Rods = 20 mm

Diameter of stirrups = 8 mm

C/C of stirrups = 150 mm

Clear Span or Height of column above foundation = 3000 mm

Depth of Foundation = 350 mm Clear Cover of Footing = 40 mm

Formula,

Length of Vertical bar = Development length (Ld) + Depth of Footing + Height of column + Overlap Length – Bend Length

= 50d + 350 + 3000 + 0 – 2d

= (50×20) + 350 + (3000) – (2×20)

= 4310 mm = 4.310 meter

Here, Overlapping Length should not considered because the standard size of steel rod is found to be 12 meter. But we require only 4.310 meter.

So,

Cutting length is equal to the total length of vertical bars calculated above.

If the steel rod were more than 12 meter then, overlapping length would be added.

By the way let’s see how to calculate the over lapping length of steel rod of column.

So,

Weight of main rods = d2/162.25 x Length of Main bars

W1 = 3.14 x 202/162.25 x 4.310

W1 = 33.36 kg

#### Step 2 – Find out lapping

As we know that lapping length required is taken 50d = 50 * Diameter of the bar = 50×20 = 1000 mm.

#### Step 3 – Find out no. of Stirrups.

Number of stirrups required = (Total length of verticle bar/Spacing of stirrups) + 1

Number of stirrups required = (350+3000)/150 + 1

= 23.33 Number of stirrups    Say, 24 Nos.

#### Step 4 – Calculate Cutting Length of Circular Stirrups

Formula,

Cutting length of one Circular Stirrup or Ring (L) = Circumference of Circular Stirrup + Total Hook length – Total Bend Length

L =  πD + (2 x 9d) – (2 x 3d)

Where, D = Diameter of Column – Clear cover – Clear cover = 300 – 25 – 25 = 250 mm, and d is diameter of stirrups.

So,

L = 3.14 x 250 + (2 x 9 x 8) – (2 x 3 x 8) = 881 mm

Hence,

Total Cutting length of Circular Stirrup or Ring = L x No. of Stirrups = 881 x 24 = 21144 mm = 21.144 meter

#### Step 5 – Calculate Cutting Length of Circular Stirrups

Total Weight of Stirrups = d2/162.25 x Length of Main bars

W2 = 3.14 x 82/162.25 x 21.144

W2 = 26.18 kg

Total weight of steel rod used in circular column = 33.36 + 26.18 = 59.54 kg

Happy Learning – Civil Concept

Contributed by,

Civil Engineer – Ranjeet Sahani