How to Make Bar Bending Schedule of Circular Slab | BBS of Circular Slab

 In this article today we will cover How to Make Bar Bending Schedule of Circular Slab | BBS of Circular Slab | How to Calculate Circular Slab Reinforcement | Steel Quantity of RCC Circular Slab | Cutting Length of Circular Slab | How do you Calculate Steel in a Circular Slab | Circular Slab Steel Calculation formula | Unit Weight | Steel Calculation for Circular RCC Slab | Quantity of Steel in Circular Slab

BBS Calculation for a Circular Slab:

Unlike other rectangular slabs, circular slabs are not frequently used. Basic uses of the circular slabs are mostly in water tanks, manhole covers, towers, soak pit chambers, swimming pools, etc. To calculate the steel quantity for a circular slab, BBS needs to be prepared.

Bar Bending Schedule of Circular Slab | Due to the change of length of reinforcement bar according to the diameter of circle, the calculation is slight difficult unlike other RCC members.

Here, L is the diameter of Circular slab reinforcement.

Pythagoras theorem is required to find:

L1- √(R2-  h1^2) * 2

L2- √(R^2 –  h2^2) * 2

L3- √(R^2 –  h3^2) * 2

The length of the reinforcement bar is L- Radius of circular slab reinforcement(clear cover on both sides excluded) is R- Distance between two bars is h.

Circular Slab Reinforcement Calculation:

Let’s assume-

Diameter of circular slab = 3m = 3000mm

Diameter of main bars = 12mm

Diameter of distribution bars = 8mm

Main Bars Calculation:

Required evaluation-

No. of rods for circular slabs= (Diameter of circular slab- Clear cover on both sides)/centre to centre distance

{(3000)-(2*25)}/200 = 15no.s

Separate calculation of length of no. 8 rods- 

As L= (Diameter of circular slab- Clear cover on both sides)= 2.95m,

We need to calculate length of  L1-L7,

Using Pythagoras theorem-

L1- √(R^2 –  h1^2) * 2

R= 2.95/2= 1.475

Thus,

L1- √(R^2 –  h1^2) * 2 = √(1.475^2 –  0.2^2) * 2=2.92m

L2- √(R^2 –  h2^2) * 2 = √(1.475^2 –  0.4^2) * 2=2.84m

L3- √(R^2 –  h3^2) * 2 = √(1.475^2 –  0.6^2) * 2=2.70m

L4- √(R^2 –  h4^2) * 2 = √(1.475^2 –  0.8^2) * 2=2.48m

L5- √(R^2 –  h5^2) * 2 = √(1.475^2 –  1^2) * 2=2.16m

L6- √(R^2 –  h6^2) * 2 = √(1.475^2 –  1.2^2) * 2=1.72m

L7- √(R^2 –  h7^2) * 2 = √(1.475^2 –  1.4^2) * 2=0.93m

Total Length of main bars Lx = L+2(L1) +2(L2) +2(L3) +2(L4) +2(L5) +2(L6) +2(L7) 

= L+ 2(L1) + 2(L2) + 2(L3) + 2(L4) + 2(L5) + 2(L6) +2(L7)

=2.95+2(2.92) +2(L2.84) +2(2.70) +2(2.48) +2(2.16) + 2(1.72) +2(0.93)

=34.45m

Weight of main bars = 12^2 * 34.45/162 =3 0.62kg

Distribution Bars Calculation:

This calculation is same as that of main reinforcement.

Total Length of distribution bars Ly = L+2(L1) +2(L2) +2(L3) +2(L4) +2(L5) +2(L6) +2(L7) 

= 2.95+2(2.92) +2(L2.84) +2(2.70) +2(2.48) +2(2.16) +2(1.72) +2(0.93)

= 34.45m

Weight of distribution bars = 8^2 * 34.45/162 = 13.60kg

Total Weight of steel reinforcement= 30.62kg + 13.60kg = 44.22kg

BBS Calculation of Circular Slab:

For Main Reinforcement:

Bars	Numbers	Cutting Length(m)	Diameter(mm)	Weight(kg)
L	1	2.95	12	2.62
L1	2	2.92	12	2.59
L2	2	2.84	12	2.52
L3	2	2.70	12	2.39
L4	2	2.48	12	2.20
L5	2	2.16	12	1.91
L6	2	1.72	12	1.52
L7	2	0.93	12	0.82
TOTAL	15	34.45		30.62

For Distribution Bars:

Bars	Numbers	Cutting Length(m)	Diameter(mm)	Weight(kg)
L	1	2.95	8	1.16
L1	2	2.92	8	1.15
L2	2	2.84	8	1.13
L3	2	2.70	8	1.12
L4	2	2.48	8	1.08
L5	2	2.16	8	1.06
L6	2	1.72	8	0.67
L7	2	0.93	8	0.36
TOTAL	15	34.45		13.60

We have explained how to calculate a weight of a steel bar?

Note – If you are not sure about how many rods by dividing, keep on doing L formula if you have a negative value then that is the end of your calculation. 

Hope you have enjoyed the content.

Conclusion:

Full article on How to Make Bar Bending Schedule of Circular Slab | BBS of Circular Slab | How to Calculate Circular Slab Reinforcement | Steel Quantity of RCC Circular Slab | Cutting Length of Circular Slab | How do you Calculate Steel in a Circular Slab | Circular Slab Steel Calculation formula | Unit Weight | Steel Calculation for Circular RCC Slab | Quantity of Steel in Circular Slab. Thank you for the full reading of this article in "QA QC Civil Engineering" platform in English. If you find this post helpful, then help others by sharing it on social media.