| Primary value | 47 × bar diameter (≈ 750 mm for 16 mm bar (Fe500 / M25)) |
| Applies to | Fe500 deformed bars in tension at point of cut-off · Embedment of bars in supports, columns, and beams · Anchorage of bottom bars at end supports |
| Exceptions | Fe500 / M20 → 56 d |
| Fe500 / M25 → 47 d | |
| Fe500 / M30 → 40 d | |
| Fe415 / M25 → 40 d | |
| Compression bars → Use 0.8 × Ld | |
| Bar with standard hook → Reduce by 16 d for the hook | |
| Measured as | Straight embedment from the section where the bar is fully stressed to the end of the bar (or to a hook point). Hooks count as anchorage value: 90° bend = 8d, 135° bend = 12d, U-bend = 16d. |
| Source | IS 456 — Clause 26.2.1 ✓ Verified |
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Development length is the bond-stress equivalent of bar yield strength. If you cut a bar without enough Ld behind it, the bar can pull out of the concrete before yielding — the failure is brittle and unannounced. 47d for Fe500/M25 is the floor below which any cut-off needs hooks or anchor plates.
Designers use 50d for Fe500/M25 as a conservative default that also covers tension lap splices. End-supports of beams add a standard 90° hook to bottom bars — the 8d hook reduces required straight embedment to ~40d, fitting comfortably inside a 230 × 600 mm beam.