BBS Of Beam – Bar Bending Schedule For Beam [Steel Quantity]
In this article I will discuss how to prepare BBS for beam.
Bar Bending Schedule For Beam:
This beam has more technical design implementation than the above simple beam. Let’s get started.
The beam has a clear span of 5 meters consisting of two bottom layers (2 no.s of 20 mm dia and 2 no.s of 16 mm dia) and one top layer (2 no.s of 12 mm dia).
It consists of 3 zones where zone 1 and zone 3 have 8 mm dia stirrups with a spacing of 150 mm & Zone 2 has 8 mm dia stirrups with a spacing of 200 mm.
Clear Span of Beam = 5000 mm
Development Length Ld = 50d (assumption)
Clear Cover on any ends = 25 mm
Bottom – 2 no.s 20Ø and 2 no.s of 16Ø
Top – 2 no.s of 12Ø
Stirrups
Zone 1,3 = 8Ø @ 150mm clear cover
Zone 2 = 8Ø @ 200mm clear cover
Step 1 – Calculate Cutting Length Of Top Bar
Cutting length of top bar = Clear Span of Beam + Development length – Bend
Where bend for 45deg=1d, 90deg=2d, 135deg=3d
Cutting length = L + (2 x Ld) – (2 x 2d)
= 5000 + (2 x 50 x 12) – (2 x 2 x 12)
= 5000 + (2 x 50 x 12) – 50
= 6152 mm
Step 2 – Calculate Cutting Length Of Bottom Bar
For First Layer (20Ø):
Cutting length of bottom bar = Clear Span of Beam + Development length – Bend
Where bend for 45deg=1d, 90deg=2d, 135deg=3d
Cutting length = L + (2 x Ld) – (2 x 2d)
= 5000 + (2 x 50 x 20) – (2 x 2 x 20)
= 6920 mm
For Second Layer (16Φ):
Cutting length of bottom bar = Clear Span of Beam + Development length – Bend
Cutting length = L + (2 x Ld) – (2 x 2d)
= 5000 + (2 x 50 x 16) – (2 x 2 x 16)
= 6536 mm
Step 3 – Calculate Number of Stirrups
This beam has three zones where Zone 1 & 3 consist of 8 mm dia stirrups of 150 mm spacing and Zone 3 has 8 mm dia stirrups of 200 mm spacing.
First we need to calculate the length of each zone = L/3 = 5000/3 = 1666 mm
Number of stirrups required for Zone 1 = (Clear Span of beam/ Spacing of stirrups) + 1
= (1666/150)+1 = 12.10 ♎ 12 no.s
Number of stirrups required for Zone 3 = Same as Zone 1 = 12 no.s
Number of stirrups required for Zone 2 = (Clear Span of beam/ spacing Stirrups) – 1 = (1666/200) – 1 = 7 no.s
The reason for the “minus 1 “ is already zone 1 has end stirrup so we don’t need to again start from the new one. we just continue the stirrups already existing with extra spacing.
Cutting length of stirrups:
Cross section of stirrups is
Width = 300 mm
Height = 500 mm
a is horizontal length of stirrup
= 300 – (2 x clear cover) – (2 x half of bar dia )
= 300 – (2 x 25) – ( 2 x 4)
= 242 mm
b is vertical length of stirrup
= 500 – (2 x clear cover) – (2 x half of bar dia)
= 500 – (2 x 25) – (2 x 4)
=442
Now calculate cutting length of stirrup
Cutting length = 2 x (a+b) + hook – bend
= 2 x ( 242 + 442) + (9d x 2) – (3d x2) – (2d x 3) [For 2 no. 135 bend (3dx2) & for 3 no. 90 bend (2dx3)]
= 2 x 684 + (9 x 8 x2) – (3 x 8 x 2) – (2 x 8 x3)
= 926 + 144 – 48 – 48
= 974 mm = 0.97 m
Calculate Weight Of Stirrups:
Total no. of stirrups = 12 + 12 + 7 = 31
Total length of stirrups = 0.97 x 31 = 30.19 m
Total weight of stirrups = d2xL/162 = 8 x8 x 30.19/162 = 12 kg
BBS Of Beam:
| Diameter of Bar (mm) | Numbers | Cutting Length m | Total Length m | Total Weight kg | |
|---|---|---|---|---|---|
| Top Bar | 12 | 2 | 6.152 | 12.30 | 10.93 |
| Bottom Bar | 20 | 2 | 6.920 | 13.84 | 34.6 |
| Bottom Bar | 16 | 2 | 6.536 | 13.07 | 20.91 |
| Stirrup | 8 | 31 | 0.974 | 30.19 | 12 |
I hope you can now prepare bbs of beam easily. Keep learning.
Also Read –
Bar Bending Schedule Of Lintel
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