---
title: "Shear strength and bond strength"
subject: "Concrete Technology and Masonry Structure"
chapter: 5
key: "semester_5/concrete_technology_and_masonry_structure:shear-bond-strength"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/shear-bond-strength
site: BCT Engineering
---

# Shear strength and bond strength

Concrete Technology and Masonry Structure · Chapter 5: Testing of concrete and quality control

- Asked in: 2082 Baisakh, 4 marks
- Video: [Bond Strength between Concrete and Reinforcement](https://www.youtube.com/watch?v=wDZGPepLHmM) — Civil Engineering
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/shear-bond-strength
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-5

## Question

Describe in short the shear strength and bond strength of concrete.

## Short answer

Shear strength: resistance to sliding; in beams, diagonal tension governs (τ_v = V_u/bd, τ_c from Table 19). Bond strength: grip between steel and concrete from adhesion, friction, and rib interlock; design bond stress for M20 plain bars is 1.2 N/mm² (1.92 for deformed), and development length L_d = φσ_s/(4τ_bd).

## Answer

#### Shear strength
Resistance of concrete to sliding of one part over another. Pure shear is about 20 to 30% of $f_c$; in beams the failure is by diagonal tension. IS 456 (Cl. 40) uses the nominal shear stress $\tau_v = V_u/bd$, compared with the permitted $\tau_c$ (Table 19, depends on grade and tension steel %) and $\tau_{c,max}$ (Table 20); stirrups carry the excess.

#### Bond strength
Bond is the adhesion and friction between the reinforcement and concrete, and mechanical interlock with the ribs of deformed bars, which transfers force between the two materials.

- **Design bond stress** $\tau_{bd}$ (IS 456, Cl. 26.2.1.1): 1.2 N/mm$^2$ for M20 plain bars in tension; increased by 60% for deformed bars (1.92 N/mm$^2$), and by 25% in compression.
- **Development length:** $L_d = \dfrac{\phi\,\sigma_s}{4\,\tau_{bd}}$ (Cl. 26.2.1).
- Bond is increased by higher concrete strength, ribs on bars, adequate cover, lower position of the bar (better compaction), hooks and anchorage; it is reduced by rust scale, oil, and top-cast bars with bleeding.

## Check yourself

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

1. How do beams commonly fail in shear?
   A. Direct sliding
   B. Crushing
   C. Diagonal tension
   D. Bond slip only
   Answer: C. Shear in beams occurs with flexure and causes diagonal tension failure. (Key point: Beam failure)

2. What does bond do?
   A. Increases concrete strength
   B. Prevents corrosion only
   C. Reduces shrinkage
   D. Transfers force between steel and concrete through adhesion, friction and interlock
   Answer: D. Bond transfers force so the two materials act together. (Key point: Bond)

3. What is the design bond stress for deformed bars in M20 tension?
   A. 1.92 N/mm2
   B. 1.2 N/mm2
   C. 0.75 N/mm2
   D. 3.0 N/mm2
   Answer: A. Plain bars 1.2 increased by 60% gives 1.92. (Key point: Deformed bar bond)

4. Which gives the development length?
   A. Ld = 4 phi tau_bd/sigma_s
   B. Ld = phi sigma_s/(4 tau_bd)
   C. Ld = phi tau_bd/sigma_s
   D. Ld = sigma_s/(phi tau_bd)
   Answer: B. Ld = phi sigma_s/(4 tau_bd). (Key point: Development length)

## Related in Concrete Technology and Masonry Structure

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- [Bond between steel and concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Abond-steel-concrete) — Concrete Technology and Masonry Structure, chapter 5
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