Bar Bending Schedule of Circular Column | Circular Column BBS

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 135⁰. (3d)

 

Total Cutting Length of Square Stirrup = 2πr + 2 numbers of hooks – 2 numbers of 135° bends

= (2 x π x r) + (18d) – (2 x 3d)

(π = 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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