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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