---
title: "Define development length (short)"
subject: "Design of RCC Structure"
chapter: 6
key: "semester_7/design_of_rcc_structure:define-development-length-short"
source: https://www.bctengineer.com/q/semester_7/design_of_rcc_structure/define-development-length-short
site: BCT Engineering
---

# Define development length (short)

Design of RCC Structure · Chapter 6: Design for bond and development length

- Asked in: 2076 Chaitra, 1 marks
- Video: [Development Length of Rebar in RC members](https://www.youtube.com/watch?v=tT9Kpxj41yw) — Dremph
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/design_of_rcc_structure/define-development-length-short
- Whole chapter: https://www.bctengineer.com/md/semester_7/design_of_rcc_structure/chapter-6

## Question

Define development length.

## Short answer

Development length is the embedded length needed to develop the design stress (0.87 f_y) in a reinforcing bar by bond, given by L_d = 0.87 f_y φ/(4 τ_bd) (IS 456).

## Answer

**Development length** is the length of a reinforcing bar, embedded in concrete, that is required to transfer the design stress in the bar to the surrounding concrete by bond, so that the bar will not pull out. It is given by $L_d=\dfrac{0.87f_y\,\phi}{4\,\tau_{bd}}$ (IS 456 cl. 26.2.1), where $\phi$ is the bar diameter and $\tau_{bd}$ the design bond stress.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Development length is best defined as
   A. The spacing between stirrups
   B. Clear cover to the bar
   C. Embedded bar length required to transfer its design stress to concrete by bond so it does not pull out
   D. The hook length at bar ends
   Answer: C. Ld is the embedded length needed to transfer the bar's design stress by bond. (Key point: Definition)

2. Which formula gives development length?
   A. Ld = 0.87 fy φ² / τbd
   B. Ld = 0.87 fy φ / (4 τbd)
   C. Ld = 4 τbd φ / (0.87 fy)
   D. Ld = fy φ / τbd
   Answer: B. From equating bar tension to bond force. (Key point: Formula)

3. If the design bond stress τbd increases, Ld
   A. Becomes zero
   B. Decreases, since Ld is inversely proportional to τbd
   C. Remains the same
   D. Increases
   Answer: B. Ld = 0.87 fy φ/(4 τbd), so higher bond strength means a shorter length. (Key point: Effect of bond stress)

## Related in Design of RCC Structure

- [Derive development length expression](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Aderive-development-length-expression) — Design of RCC Structure, chapter 6, asked 6×
- [Bond and development length with derivation](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Abond-and-development-length-with-derivation) — Design of RCC Structure, chapter 6, asked 3×
- [Define development length and lap splice](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Adefine-development-length-and-lap-splice) — Design of RCC Structure, chapter 6
- [Development length and need of splices](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Adevelopment-length-and-need-of-splices) — Design of RCC Structure, chapter 6