Bar Bending Schedule [BBS]

Bar Bending is the process of cutting, bending, and fixing the reinforcement bars as per drawing. But what about the bar bending schedule? Why do we need it? 

Take the below diagram of reinforcement details of a beam that lists all the details in comprehensive mode. It is the end result of the structural design.

The responsibility of the structural engineer has been completed by suggesting the right reinforcement bars to the structure. But at the site, many people need to understand the reinforcement details in a simple manner for their responsibilities.

What is a Bar Bending Schedule?

Bar Bending Schedule is a definitive list of reinforcement bars for any structural element that includes a mark, shape, size, location, length, and bending details of the reinforcement. It is often referred to as BBS.

Tabular view representation of each reinforcement bar used in any structural element is known as BBS.

Guidelines to Follow

Before preparing, make sure to follow the below guidelines

• Every RCC structural element should have a separate BBS. Do not group them as one.
• Ensure to follow the IS guidelines for bending, hook length, lap length & development length calculations.
• It would be handy if you memorize the unit weight of steel bars.
• Ensure the estimation by thumb rule calculations of steel reinforcement for different structural members.
• Keep Bar Bending Shape Codes handy for easy reference. 

BBS Basics & Formulas to be remembered

• Diameter of bars (in mm) – 6, 8, 10, 12, 16, 20, 25, 28, 32, 36, 40 mm
• The standard length of reinforcement bar – 12 metre or 40 feet
• Weight of bar (Kg) per metre 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

Preparation of Bar Bending Schedule

As said earlier, bbs is a definitive list of reinforcement requirements. 

• It suggests how much steel to be procured?
• It instructs the contractor to plan the week’s steel purchase.
• It instructs the bar bender to fabricate the reinforcement into the desired shape as per the structural drawing.
• It instructs the quantity surveyor for the proper estimation of the material.

How do you make a bar bending schedule?

Each structural element will be prepared separately either for each floor or for the entire building. We have discussed the bar bending schedule for different structural elements such as 

• Bar Bending Schedule for slab
• Bar Bending Schedule for beam
• Bar Bending Schedule for column

Any BBS has only five steps of calculation such as 

• Find the number of reinforcement bars to be used
• Find the cutting length of each bar
• Find the number of stirrups calculation or number of distribution bars calculation if it is a slab
• Find the cutting length of stirrups or extra bars (top rods)
• List down all the bars into the table and find out the quantity of steel.

As simple as that.

Example Bar Bending Schedule

Step 1 – Find Cutting Length of Bars

Cutting Length of Bottom Bar = Lclear – (2x concrete cover) + (2×500)

= 3000 – (2×40) + (2×500) = 3920 mm

Cutting Length of top bar =  Lclear – (2x concrete cover) = 3000 – (2×40) = 2920 mm

Step 2 – Number of Stirrups

Number of Stirrups = (Length of Beam / Spacing) + 1 = (3000/200) + 1 = 16 numbers

Step 3 – Cutting Length of Stirrups

Cutting Length of stirrup = Perimeter of stirrup + (3 x 90° bend) + (2 x hook length)

= 2 ( 520+220 ) + (3 x 2d) + (2x1d) = 1480+(3x2x10)+(2×10) = 1560 mm

Bar Bending Schedule Format

 

Bar Shape	Dia of Bar	Cutting Length	Number of Bar	Length of Bar (mm)
				8	10	12	16	20
	10	3920	2	–	7840	–	–	–
	10	2920	2	–	5840	–	–	–
	8	1560	16	24960	–	–	–	–
Total Length (m)				24.96	13.68	–	–	–
Weight Per Metre (Kg/m)				0.4	0.62	0.89	1.58	2.47
Total Weight in Kg				9.984	8.482	–	–	–

Happy Learning 🙂