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Important Concepts And Formulas for Bar Bending Schedule (BBS)

The BBS provides a clear understanding total quantity of bars required, the size of the bars, the cutting and bending length of the bars, the angle of bending, the number of bars for a member, the shape of the bars used, and the total cost of all the bars used, etc.

With the help of this accurate planning and scheduling, we can easily monitor the cost, quality, and safety of the structure.

-The total length of the main bar depends upon the distance between the members and the hook length provided at the end of the member.

Total length of the main bar = Straight length + Hook length + Other

i) Straight length of the bar

Length of straight bar = Total length – (2 x Side cover)

ii) Hook length of the bar

The hook length of the main bar refers to the length of the bar that is bent at the end to form a hook.

A hook is provided at the end to develop the anchorage between the steel and concrete.

Necessary Basics
  • Unit weight (or) Density of steel = 7850 kg/m3.

  • The standard length of the steel bar available at the market is 12m or 40ft.

  • Weight of steel bar of 1m length = D2/162 kg, Where, D = Diameter of the bar.

  • Diameter of bars (in mm) – 6, 8, 10, 12, 16, 20, 25, 28, 32, 36, 40 mm

  • The standard length of reinforcement bar – 12 meter or 40 feet

  • Weight of bar (Kg) per meter formula – D2/162

Extension Length Formulas
  • Footing lap length formula – 40d

  • Column Lap length formula – 50d

  • Development length for dowel bars – 16d

  • Hook Length – 9d

Concrete Cover
  • Footing – 75 mm

  • Column & Beam – 25-50 mm

Bend Deduction
  • 45° – 1d

  • 90° – 2d

  • 135° – 3d

Crank Length Formula
  • 45° – 0.42d

  • 30° – 0.27d

  • 60° – 0.58d

Extra Bars Length
  • L/4 or L/5

Cutting length of stirrup
  • For 45-degree bend = Add 1D

  • For 90-degree bend = Add 2D

  • For 135-degree bend = Add 3D

Cutting length of bent-up bar / cranked bar
  • For 30-degree crank = Add 0.27D

  • For 40-degree crank = Add 0.42D

  • For 60-degree crank = Add 0.58D

Lap length of the bar
  • For Columns – 45D to 50D

  • For Beams – 60D

  • For Slabs – 60D

Remember these are general values when HYSD bars are used. When you are using different types of bars such as Cold Twisted Deformed bars, these values may vary. Kindly refer to IS 2502: 1963 for more information.

Hope you understand everything you need to know about the Bar Bending Schedule (BBS).


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