Bar Bending Schedule Calculator
What is a Bar Bending Schedule Calculator?
What is Bar Bending Schedule?
The Bar Bending Schedule (BBS) Calculator determines net cutting length of steel bars incorporating concrete cover, end hooks, crank bends, and bend deductions.
Formula
Cutting Length (Straight) = Clear Span - 2(Concrete Cover) + 2(Hook Length 9d) - 2(Bend Deduction 2d for 90°)
Stirrup Length = 2(A + B) + 2(Hook 10d) - 5(Bend Deductions)
Variables Explanation
- Clear Span: Structural member length.
- Concrete Cover: Protective cover (25mm slab, 40mm beam, 50mm footing).
- d: Rebar diameter in mm.
- Hooks: 9d for 180° standard end hook, 10d/12d for stirrup hooks.
- Bend Deductions: 45° = 1d, 90° = 2d, 135° = 3d.
How to Calculate
1. Select bar shape (Straight, Cranked, Rectangular Stirrup).
2. Input member dimensions and bar diameter (d).
3. Input concrete cover and number of bars.
4. View net cutting length per bar and total steel weight (kg).
Worked Example
Beam Span: 4,000mm (4m). 20mm rebar diameter. Cover = 40mm.
Straight Bar with 90° Hooks at ends (2 × 12d hooks):
Cutting Length = 4,000 - 2(40) + 2(12 × 20) - 2(2 × 20) = 3,920 + 480 - 80 = 4,320 mm (4.32m).
Total Weight (10 bars) = 4.32m × (20² / 162) × 10 = 106.6 kg.
Practical Construction & Project Controls Use
Issue exact cutting orders to steel benders on site, eliminate rebar off-cut scrap waste, and prepare BBS client billing statements.
Understanding the Result
Outputs precise fabrication shop cut length, preventing rebar undersizing or steel waste.
Limitations & Assumptions
Calculates standard shapes according to IS 2502 / BS 8666 code norms. Complex 3D spatial reinforcement requires CAD detail exports.
Frequently Asked Questions
What is a Bar Bending Schedule (BBS)?
BBS is a comprehensive list indicating the location, mark, diameter, shape, cutting length, and quantity of steel rebar.
Why are bend deductions subtracted in cutting length calculations?
Steel elongates when bent cold; subtracting 1d for 45° or 2d for 90° ensures the bent bar matches drawing dimensions.
What is the standard hook length for rebar ends?
Standard 180° hook length is 9d (9 times bar diameter); 90° L-bend anchoring is typically 12d.
What concrete cover is recommended for different RCC structural members?
Standard cover: Slabs = 15-20mm, Beams = 25-40mm, Columns = 40mm, Footings in contact with soil = 50-75mm.
How is crank length (bent-up bar) calculated in slabs?
Cranked length addition = 0.42 × D (where D is net depth = slab thickness - top & bottom cover).