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

# Define development length and lap splice

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

- Asked in: 2075 Chaitra, 2 marks
- Video: [Bond Development Length, Hooks, and Lap Splicing Explained | Part 1 | NSCP/ACI Reinforcement Design](https://www.youtube.com/watch?v=ioskxtwDxDQ) — MD Structural Engineer
- 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-and-lap-splice
- Whole chapter: https://www.bctengineer.com/md/semester_7/design_of_rcc_structure/chapter-6

## Question

Define development length and lap splice.

## Short answer

Development length is the embedded length to develop full bar stress through bond, L_d = 0.87 f_y φ/(4 τ_bd). Lap splice: overlapping bars for force transfer; lap length ≥ L_d (≥30φ in flexural tension, 2L_d in direct tension, 24φ in compression), placed staggered away from high-stress sections.

## Answer

- **Development length ($L_d$):** the length of reinforcing bar that must be embedded in concrete beyond a section so that the bar can develop its full design stress ($0.87f_y$) through bond without slipping. $L_d=\dfrac{0.87f_y\,\phi}{4\tau_{bd}}$, e.g. about $47\phi$ for Fe415 deformed bars in M20.
- **Lap splice:** a joint between two reinforcing bars made by placing them side by side and overlapping them for a specified length, so that the force passes from one bar to the other through the concrete by bond. The lap length is not less than $L_d$ or $30\phi$ (whichever is greater) for bars in flexural tension, $2L_d$ or $30\phi$ in direct tension, and $L_d$ (in compression) or $24\phi$ for bars in compression. Laps should be staggered and kept away from sections of maximum stress.

## Check yourself

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

1. What does development length ensure?
   A. The bar will not corrode
   B. The bar has enough cover
   C. The bar can develop its full design stress 0.87 fy through bond without slipping
   D. The concrete reaches 28-day strength
   Answer: C. Ld is the embedded length required to develop the design stress by bond. (Key point: Development length)

2. Which minimum lap lengths are correct?
   A. Ld/2 in flexure; 2Ld in compression
   B. 12φ in tension; 8φ in compression
   C. 50φ everywhere
   D. Ld or 30φ in flexural tension; 24φ in compression
   Answer: D. Flexural tension: not less than Ld and 30φ; compression: 24φ (Ld in compression). (Key point: Lap length rules)

3. Where should lap splices be placed?
   A. Only at mid-span
   B. All at the section of maximum moment
   C. All at one section
   D. Staggered, and away from sections of maximum stress
   Answer: D. Laps are staggered and avoided at maximum stress sections. (Key point: Lap placement)

## Related in Design of RCC Structure

- [Define Ld and lap splice, derive Ld](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Adefine-ld-and-lap-splice-derive) — Design of RCC Structure, chapter 6, asked 6×
- [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 (short)](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Adefine-development-length-short) — 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

## Related in other subjects

- [Riveted lap joint strength and efficiency](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Ariveted-joint-strength-efficiency) — Workshop Technology, chapter 10