We have discussed Bar Bending Schedule for different structural members such as

**Contents of the Article**show

Here we are going to discuss the **Bar Bending Schedule for Circular Slab**

**Circular Slab**

Circular slabs are not usually common like flat rectangular slabs that we use almost every floor. Circular slabs are used in the following areas

- Water tank cover
- Manhole covers
- A room specifically designed for circular slab
- Towers
- Pump houses constructed above tube wells
- Soak Pit Design

Unlike one way slabs, circular slabs are subjected to bending moments in both directions.

Letâ€™s discuss with an example calculation. Note here we are dealing with a simple manhole cover for calculation purposes; we have taken greater value as the diameter of the slab.Â

In practice, the circular slab of 3m diameter may have detailed reinforcement.

**Circular Slab Reinforcement Detailing**

**Circular Slab Reinforcement Calculation**

Assume you have to prepare a bar bending schedule for a circular slab of 3 metre diameter with 12mm main & distribution bars with 200mm spacing; concrete cover of 25mm.

Splitting the slab into two parts for easy calculation.

**Step 1 â€“ Find the Value of L**

The only formula you need to remember for the entire calculation is

L = âˆš(R^{2}â€“ h^{2}) x 2 where

L = Length of the reinforcement

R â€“ Radius of the slab

h â€“ Distance between the reinforcement

From the above diagram, We can calculate the value of L

L = Diameter of Circular Slab â€“ Concrete Cover on both sides = 3000-(2*25) = 2950 mm or 2.95 m

Radius of the slab = (Diameter of the slab â€“ concrete cover on both sides ) / 2 = 2950/2 = 1475 mm or 1.475m

**Step 2 â€“ Find the Number of (L) Bars required**

Number of L Bars = (Diameter of the slab â€“ concrete cover on both sides)/Spacing = 1475/200 = 7.375 or 7 Nos

Apart from the Centre Rod (L), we need 3 more bars on both sides such as L1, L2, L3

**Step 3 â€“ Find the Consecutive Bar Length**

For L = âˆš(R^{2} â€“ h1^{2}) x 2 where h1 = distance between L & L1 or spacing of bars â€“ 200 mm

Therefore, L1 = âˆš(R^{2} â€“ h1^{2}) x 2 =Â âˆš((1475)^{2} â€“ (200)^{2})x2 = 2066.7 mm

L2 = âˆš(R^{2} â€“ h2^{2}) x 2= âˆš((1475)^{2} â€“ (400)^{2}) x 2 = 2007.8 mm

L3 = âˆš(R^{2} â€“ h3^{2}) x 2= âˆš((1475)^{2} â€“ (600)^{2}) x 2 = 1905.58 mm

Note â€“ The circular slab has reinforcement on both sides, so the value will be multiplied by 2 to get the reinforcement length on the perpendicular side.

**Step 4 â€“ Bar Bending Schedule Format â€“ Circular Slab**

Description |
Dia of bar (mm) |
Number of Bars |
Cutting Length (m) |
Total Cutting Length (m) |
Weight Per Metre (Kg/m) |
Total Weight (Kg) |

L | 12 | 2 | 2.95 | 5.9 | 0.89 | 5.251 |

L1 | 12 | 4 | 2.07 | 8.28 | 0.89 | 7.369 |

L2 | 12 | 4 | 2.01 | 8.04 | 0.89 | 7.155 |

L3 | 12 | 4 | 1.91 | 7.64 | 0.89 | 6.799 |

TOTAL |
26.57 Kg |

Happy Learning ðŸ™‚