Bar Bending Schedule of Circular Column
How to calculate the quantity of steel
in a circular column (BBS)
In this article, we
explained about Bar Bending Schedule of
Circular Column
Given data:
Height
Ground Floor height – 3000
mm or 3 m
1st Floor height - 3000 mm
or 3 m
2^{nd} Floor height
- 3000 mm or 3 m
Height of Ground Level – 3600
mm
Footing Height – 300 mm
Slab Thickness – 125 mm
Footing Height – 300 mm
Diameter of column - 450mm
A column has 8 numbers of 20
mm dia bars @150mm
Stirrups center to center
spacing = 8mm stirrups @ 150 mm C/C
Footing Clear Cover – 50 mm
Column Clear Cover – 25 mm
Development
Length – 50d
SOLUTION:
The calculation was to
proceed into two steps.
·
Longitudinal bars – vertical
bars calculation
·
Cutting length of
stirrups
STEP 1: Longitudinal bars –
vertical bars calculation
Length of 1 Vertical Rod = Total height of the column + Development
length (Ld) + Overlap Length + Extension rod (Ld)
H = Total height of the column =
Height of Ground Level + Floor Heights (1,2,3) + Slab Thicknesses + Footing – (footing
clear cover) = 3600 + 3000 + 3000 + 3000 + (4x125) + 300 – 50 = 13050 = 13.35m
Development length = Ld = 50d
Dia of steel bar = 20mm
Ld = 50 x 20 = 1000mm = 1m
Overlap Length
Column = Vertical Member = Compressive
member = 40d
Must read:
BBS
Basics: Lapping, bend, development and hook length calculation
Over-lap length Length of
steel bar = 40d
Diameter = 20mm
Over-lap length Length of
steel bar = 40 x 20 = 800mm = 0.8m
Note: we will pour slab
concrete after column concrete so, we have to give overlap extension rod for
each slab
As we know, 4 slab
Over-lap length Length of steel bar = 4 x 0.8 = 3.2m
Extension Length
Extension Length = 1 over-lap length
Extension length rod has given in roof slab for
future column extension. This extension rod will be covered by concrete to avoid corrosion
Extension length = 0.8m
Length of 1 Vertical Rod = Total height of the column + Development
length (Ld) + Overlap Length + Extension rod (Ld)
Length of 1 Vertical Rod = 13.35m + 1m + 3.2m + 0.8m = 18.35m
The length one vertical bar is 18.35m. As we have eight vertical bars =
8 x 18.35 = 146.8m
Total length of vertical
rod = 146.8m
STEP 2: Cutting length of
stirrups
Diameter of column - 450mm
Stirrups center to center spacing = 8mm stirrups @ 150 mm C/C
No of Stirrups Required = Length / spacing
bar + 1
Length = 18.35m
Spacing stirrups = 150mm = 0.15m
No of Stirrups Required = (18.35/0.15)+1 = 122.33 + 1 = 123.33 = 124nos
No of Stirrups Required = 124nos
Cutting length of stirrups
Diameter = 450mm
Deducting the concrete cover 25mm from all sides
Diameter = 450 – 25 – 5 (half dia of bar) = 395mm
Radius = d/2 = 395/2 = 197.5
Total Length of the hook:
There are 2 hooks which mean 9d+9d = 18d
Total length of Bends:
There 2 bends at an angle of 135^{0}. (3d)
Total Cutting Length of Square Stirrup = 2Ï€r + 2 numbers of
hooks – 2 numbers of 135° bends
= (2 x Ï€ x r) + (18d) – (2 x 3d)
(Ï€ = 3. 14)
(d=10mm as we mention step -2)
= (2 x 3.14 x 197.5) + (18 x 8) – (2 x 3 x 8)
= 1240.3 + (18 x 8) – (2 x 3 x 8)
= 1240.3 + (144) – (48)
= 1336.3mm = 1.33m
Total Cutting Length of Square Stirrup 1.33m
Bar Bending Schedule of Circular Column
S.no |
Bar Mark |
Bar dia |
No of bars |
Length (m) |
unit weight of steel rod (m/kg) |
weight of steel (Kg) |
1 |
Vertical
Bar |
20 |
8 |
18.35 |
2.4666 |
164.76 |
2 |
Stirrups
Bar |
8 |
124 |
1.33 |
0.395 |
65.143 |
Total Weight of
Reinforced Concrete Circular Column |
229.903 |
Must Read: How
To Calculate Cutting Length Of Circle Stirrups In Beam And Column
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