---
title: "Diagonal shear test of masonry wall"
subject: "Concrete Technology and Masonry Structure"
chapter: 10
key: "semester_5/concrete_technology_and_masonry_structure:diagonal-shear-test"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/diagonal-shear-test
site: BCT Engineering
---

# Diagonal shear test of masonry wall

Concrete Technology and Masonry Structure · Chapter 10: Testing of masonry elements

- Asked in: 2081 Baisakh, 2 marks; 2073 Shrawan, 6 marks; 2072 Chaitra, 6 marks; 2072 Kartik, 6 marks; 2070 Chaitra, 6 marks (asked 5 times)
- Video: [Diagonal Compression Tests on Unreinforced Masonry (URM) Walls](https://www.youtube.com/watch?v=T7OZSUNwZTQ) — Enea Mustafaraj
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/diagonal-shear-test
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-10

## Question

Describe the diagonal shear test for masonry wall.

## Short answer

A square masonry panel (≈1.2 m) is loaded in compression along one diagonal until diagonal cracking occurs. The maximum load P gives shear strength τ = 0.707P/Aₙ and diagonal tensile strength fₜ = 0.5P/Aₙ, where Aₙ is the average cross‑sectional area. Shear modulus G is computed from diagonal deformations.

## Answer

#### Diagonal shear (diagonal compression) test

**Purpose:** to find the shear strength (diagonal tensile strength) and shear modulus of masonry; used for in-plane shear design (ASTM E519, RILEM TC 76).

**Specimen:** a square wall panel about 1.2 m $\times$ 1.2 m (or the actual wall in situ), built with the same unit, mortar, bond and workmanship as the structure, cured 28 days.

**Set-up and procedure**

1. The panel is turned so that one diagonal is vertical. Steel loading shoes are fixed with plaster or mortar at the two opposite corners on that diagonal.
2. A hydraulic jack and load cell apply a compressive load $P$ along the diagonal, at a uniform rate.
3. Displacement gauges (LVDTs) on both diagonals measure shortening and elongation to get shear strain.
4. The load is increased until the first diagonal crack and failure; the maximum load $P$ is recorded.

```text
        P (jack)
         |
      +--v-----+
      |\       |
      |  \     |   diagonal crack
      |    \   |   parallel to the load
      |      \ |
      +-------^+
           reaction
```

**Calculation**

$$
\tau = \frac{0.707\,P}{A_n},\qquad f_t = \frac{0.5\,P}{A_n},\qquad A_n = \frac{w+h}{2}\,t
$$

where $\tau$ is the shear strength, $f_t$ the principal (diagonal) tensile strength, $w$, $h$ and $t$ the width, height and thickness of the panel. Shear modulus $G = \tau/\gamma$, with $\gamma=(\Delta_v+\Delta_h)/g$ from the diagonal deformation.

**Failure:** diagonal cracking through the joints and units, giving the diagonal tension capacity used in design of shear walls.

## Check yourself

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

1. What does the diagonal shear test determine?
   A. Compressive strength and modulus
   B. Shear strength (diagonal tensile strength) and shear modulus
   C. Flexural bond strength
   D. In-situ vertical stress
   Answer: B. The test gives the in-plane shear strength and shear modulus of masonry. (Key point: Purpose)

2. How is the panel loaded?
   A. Uniform vertical compression on the top face
   B. Compression along one diagonal through steel shoes at opposite corners
   C. Horizontal push on one brick
   D. Hydraulic bag in a mortar slot
   Answer: B. The panel is turned so a diagonal is vertical and a jack loads it through shoes at the two corners. (Key point: Loading arrangement)

3. Which expression gives the shear strength?
   A. tau = 0.5 P / A_n
   B. tau = P / A_n
   C. tau = 0.707 P / A_n, with A_n = (w+h)t/2
   D. tau = F / (2A_b)
   Answer: C. Shear strength is 0.707P/A_n; the diagonal tensile strength is 0.5P/A_n. (Key point: Formula)

4. What is the failure mode?
   A. Vertical splitting of units
   B. Diagonal crack through joints and units along the loaded diagonal
   C. Sliding of one brick
   D. Crushing at the platen
   Answer: B. Diagonal tension cracking parallel to the load gives the capacity used for shear wall design. (Key point: Failure mode)

## Close variants set in other exams

- [Diagonal shear and push shear tests](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Adiagonal-shear-push-shear) — Concrete Technology and Masonry Structure, chapter 10, asked 6×

## Related in Concrete Technology and Masonry Structure

- [Compressive and diagonal shear tests of masonry](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Acompressive-diagonal-shear-tests) — Concrete Technology and Masonry Structure, chapter 10, asked 2×
- [Flat-jack test for brick masonry wall](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aflat-jack-test) — Concrete Technology and Masonry Structure, chapter 10, asked 2×
- [Push shear test of masonry](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Apush-shear-test) — Concrete Technology and Masonry Structure, chapter 10, asked 2×
- [Compressive strength test of brick wall](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Acompressive-test-masonry-wall) — Concrete Technology and Masonry Structure, chapter 10, asked 4×
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- [Compressive strength test of masonry prism](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Acompressive-test-masonry-prism) — Concrete Technology and Masonry Structure, chapter 10, asked 2×

## Related in other subjects

- [Diagonal shear test and flat-jack test calculations](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Adiagonal-shear-flat-jack-numerical) — Design of Timber and Masonry Structures, chapter 8
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- [Out-of-plane bending of a masonry wall](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Aout-of-plane-wall-flexure-check) — Design of Timber and Masonry Structures, chapter 6