WHAT IS BAR BENDING SCHEDULE? SOME USEFUL FORMULAS IN BBS WORK.

Bar Bending Schedule is the important part of Estimation chart. In the Bar Bending schedule provides the reinforcement (steel) calculation for reinforcement of concrete footing, column, beam and slab cutting length and also use to find the types of bends of length which we provide in steel structures.

BBS is used in finding cutting length of steel and total weight of steel per unit area. and we can make the bar bending schedule in Ms office Excel software.

Standard length of bar is 12 meter or 40 feet.

Weight of bar per meter is calculated by  D/ 162 per meter length or D/ 533 per feet length.

1. No. of bars :-

Opposite length    + 1
      Spacing

2. No. of stirrups :-  

Actual length of column or beam   + 1
                 Spacing

3. Bend deduction :-
For 45° = 1d
For 90° = 2d
For 135° = 3d

4.Cutting Length for Bent up or Crank Bar with Bends:-

For 45°,
Crank bar is bent up at an angle of 45 degree with the length of 0.42H

H = Depth of Slab - Top Cover-Bottom cover - d

Cutting length for bent up bar = Clear span + 2 x 0.42 H + 2 x Development length - 1d x no of 45° bends - 2d x no of 90° bends.


5. Hook Length:-

The hook length is commonly provided for stirrups


Hook Length = 9D [D is Diameter of the Bar]

Total Length of stirrup = Total length of Bar + 2 x Hook Length (Two hooks)

Total Length = L+2(9D)


Therefore Total length = L+18D (D is Diameter of bar)


6. Length of Straight Bar with Bends:-

Total Length = Length of Straight Portion + 2(Hook Length)



7. Bend Length Formula for Column in footing:-
Bend Length is usually provided in columns at ends to tie the columns to the footings.

Bend Length = 16D  [D is Diameter of the Bar]


8. Overlap Length / Lap Length in Reinforcement (Bar Bending Schedule) :-
Suppose the length of building is 20 m. The standard length of Rebar is 12m. We have to join two Re-bars for the total length of building. In order to Join the two bars (overlap). Overlap length is adopted.

For M 25 concrete and Fe 500 steel,
Overlap Length for compression members = 39D
Overlap Length for tension members = 49D

[D is the Diameter of the bar]


9. Cutting Length Formula for Stirrups:-
Hook’s Length for Stirrups are mostly equal to 10d, Where d is dia of bar.


Rectangular Stirrups  
Length of Stirrups = 2A + 2B + (2 x 10d)
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Triangular Stirrups | Length of Stirrups = 3H + (2 x 10d)
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Circular Stirrups | Length of Stirrups = (3.142 x Dia of Steel Ring) + (2 x 10d)
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Diamond Stirrups | Length of Stirrups = 4H + (2 x 10d)
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10. Cutting length for helix or spiral stirrups 
Length of Stirrups = Length of Spiral or Helix Bar = n x (C2 + P2)^0.5
where,
n = No. of Pitches = n = H/p + 1
C = 3.142 or Pi x d
P = Pitch or Spacing between spirals
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11. Cutting length of chair :
Chair = 2A + 2D + B
Where, A = ( 2 x Spacinf between bars + 50 mm)
            B = 50 d
            D = Slab or footing height - (uuper & lower clear cover) - Upper main bar - Lower main bar.

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