In this article, we are going to look at how to make a bar bending schedule for beam or BBS for Beam.
Some helpful posts related to this article,
1. How Many Numbers Of Rods Per Bundle? How To Calculate It
2. How To Calculate Cutting Length For Square Stirrups
Now we are going to make BBS for a beam of two example datas.
Lets start,
CONSIDER GIVEN DATA AS
Bar Bending Schedule for Beam
EXAMPLE – 2
At the bottom of the figure, the beam has a clear span of 5.5 m, which has 3 numbers and 12 mm dia bars on top and bottom consists of two layers of the bottom layer (2 numbers of 16mm dia) and one layer of the top (2 numbers of 20mm dia). with 8 mm dia stirrups on 3 Zones where Zone A, C has stirrups of 150 mm spacing & Zone B has stirrups of 200 mm spacing. and clear cover with 25 mm clear cover on both ends and sides of the beam
ALSO READ: EXAMPLE -1
As you can see that this data has more detailed and technical implementation of design aspects. So click to read this article
GIVEN DATA
Clear Span of Beam = 5500 mm
Development Length Ld = 41d (assumption)
Clear Cover on any ends = 25 mm
Bottom – 2 numbers of 16⌀ (DIA) - 2 numbers of 20⌀ (DIA)
Top – 2 numbers of 12⌀ (DIA)
Stirrups zone A,C = 8⌀ (DIA) @ 150mm clear cover zone B = 8⌀ (DIA) @ 200mm clear cover
CUTTING LENGTH OF TOP BAR
Length of 1 Rod Cutting length of top bar = l + (Ld x 2) – (2 x c.c)
l = Clear Span of Beam
Ld = Development length (Anchorage) Ld on 2 sides (41d)
d = dia of bar
c.c = clear cover (2 ends)
Length of 1 Rod Cutting length of top bar = 5.5 + (41d x 2) – (2 x 25) = 3.5 + (41(12) x 2) – (2 x 25)
= 5500+(2 x 41d) – 2 x 25 = 5500 + (41(12) X2) – 50
Length of 1 Rod Cutting length of top bar = 6434
The length of one Rod Cutting length of top bar is 6.434. we have a total bar three bars
= 3 x 6.434 = 19.30m
The total length of top bar = 19.30m bar – 2bar of 12 mm needed
FIND CUTTING LENGTH OF BOTTOM BAR
2 numbers of 16mm dia
Length of 1 Rod Cutting length of bottom bar = l + (Ld x 2) – (2 x c.c) Clear Cover on 2 ends
= 5500+(2 x 41d) – 2 x 25 = 5500 + (41(16) X2) – 50
Length of 1 Rod Cutting length of top bar = 6762
2 numbers of 20mm dia
Length of 1 Rod Cutting length of bottom bar = l + (Ld x 2) – (2 x c.c) Clear Cover on 2 ends
= 5500+(2 x 41d) – 2 x 25 = 5500 + (41(20) X2) – 50
Length of 1 Rod Cutting length of top bar = 7090
Total length of the bottom bar
2 numbers of 16mm dia = 2 x 6.762 = 13.52mm
2 numbers of 20mm dia = 2 x 7.090 = 14.18mm
CUTTING THE LENGTH OF STIRRUPS
The cross-sectional area of the beam is 300 mm x 400 mm
Take it has,
500mm is side A
300mm is side B
Minimum clear cover to the reinforcement: 15 mm to the bars in slabs, 25 mm to bars in beams and columns. In large columns, say 450 mm in thickness, the cover should be 40 mm.
Also Read: know about cover blocks used in construction
SIDE A | SIDE B |
A =500 – 2 Side clear cover
A = 500 – 2 x clear cover
A = 500 – 2 x 40
A = 500 – 80
A = 420 mm | B =300 – 2 x Top & Bottom cover
B = 300 – 2 x clear cover
B = 300 – 2 x 40
B = 300 – 80
B = 220 mm |
NO OF STIRRUPS REQUIRED
As mentioned Stirrups spacing with 8 mm dia stirrups on 3 Zones where Zone A, C has stirrups of 150 mm spacing & Zone B has stirrups of 200 mm spacing
Formula = L/3 +1
NO OF STIRRUPS NEEDED IN ZONE A & C
=1800 / 150 + 1
= 13 nos
NO OF STIRRUPS NEEDED IN ZONE B
=1900 / 200 + 1
= 10.5 nos say 11 nos
Also Read: How to calculate the quantity of steel in column (BBS)
CUTTING LENGTH OF ONE STIRRUP
Formula:
Cutting Length of Stirrups = Perimeter of Shape + Total hook length – Total Bend Length
= 2(a+b) + 2(9d) – 3(2d) – 2 (3d)
= 2(500+300) + 2(9x8) – 3(2x8) – 2(3x8)
= 2(800) + 2(72) – 3(16) – 2(24)
= 1600 + 144 – 48 – 48
= 1648mm say as 1.64m
We have a total of (11 +13) 24 nos of stirrups, which are going to use,
Total length
= 25 x 1.64 = 39.36m
CUTTING THE LENGTH OF RECTANGULAR STIRRUPS = 40 m
RESULT:
| Diameter of Bar | Numbers | Cutting Length | Total Length | No of bar |
Top Bar | 12mm | 3 | 6.434m | 19.30 m | 2 |
Bottom Bar | 16mm | 2 | 6.762 m | 13.52 m | 2 |
Bottom Bar | 25mm | 2 | 7.090 m | 14.18 m | 2 |
Stirrups | 8mm | 24 | 1.44 m | 40 m | 1 |
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