Mastering Rebar Bending: A Comprehensive Guide
The Rebar Bending Calculator computes accurate cut lengths for straight bars, standard hooks, and closed stirrups using ACI 318 and CRSI bend deductions. It accounts for hook extensions, cover, and bend radius to minimize waste and ensure constructability. This guide covers ACI requirements, bend types, calculation steps, and field practices for error-free detailing.
What is Rebar Bending?
Cut length = developed length − bend deductions + hook extensions. Deductions account for the loss in straight length due to the radius of the bend.
Standard deduction = 2 × (bend radius + db/2) for 90°, 4 × for 180°.
Why Accurate Bending Matters?
Precise lengths ensure:
- Proper Anchorage: Full development length.
- Fit-Up: Bars fit without field cutting.
- Cost Control: Reduce scrap and rework.
- Safety: Avoid congestion and placement issues.
Use with our Reinforcement Ratio Calculator for design.
ACI 318 Standard Hooks (Table 25.3.1)
| Bar # | 90° Hook (in) | 180° Hook (in) |
|---|---|---|
| 3–8 | 6 db | 4 db + 4 in |
| 9–11 | 8 db | 5 db + 5 in |
| 14–18 | 10 db | 6 db + 6 in |
How to Calculate Cut Length
Step-by-step:
- Draw Bar Shape: Mark straight segments and bends.
- Measure Centerline: Along bar axis.
- Apply Deductions: 2 db per 90° bend.
- Add Hook Extensions: Per ACI table.
- Round Up: To nearest 1 in.
Our calculator automates CRSI standard deductions.
Practical Applications
Used for:
- Beam Bottom Bars: 90° hooks at supports.
- Column Ties: 135° closed stirrups.
- Footing Dowels: 180° hooks.
- Slab Top Bars: Straight with lap splices.
Pair with our Steel Weight Calculator for ordering.
Tips for Accurate Detailing
Best practices:
- Use Standard Bends: Types 1–5 per CRSI.
- Check Clearance: Min 2 in between bars.
- Label Clearly: Bar mark, size, length, quantity.
- Verify Lap Splices: Class A/B per ACI.
Common Mistakes to Avoid
Avoid:
- Forgetting Deductions: Overlong bars.
- Wrong Hook Length: Insufficient anchorage.
- Ignoring Cover: Reduced durability.
- No Tolerance: ±1 in for cut length.
Advanced Considerations
For complex cases:
- Spirals and circular ties.
- Mechanical couplers instead of laps.
- Epoxy-coated bars: larger bend radius.
- Seismic hooks: 135° with 6 db extension.
Conclusion
Rebar bending accuracy prevents delays and ensures structural integrity. Our Rebar Bending Calculator delivers instant, code-compliant cut lengths for any bar shape. Combine with our Concrete Mix Design Calculator for complete RC projects. Explore our full suite of Construction Calculators for professional detailing.