---
title: "Define strength and ductility"
subject: "Civil Engineering Materials"
chapter: 1
key: "semester_3/civil_engineering_materials:property-strength-ductility"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/property-strength-ductility
site: BCT Engineering
---

# Define strength and ductility

Civil Engineering Materials · Chapter 1: Introduction to Civil Engineering Material

- Asked in: 2081 Bhadra, 2 marks
- Video: [Understanding Material Strength, Ductility and Toughness](https://www.youtube.com/watch?v=WSRqJdT2COE) — The Efficient Engineer
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/property-strength-ductility
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-1

## Question

Explain briefly the properties: Strength and Ductility.

## Short answer

Strength is the ability to resist applied load without failure, measured as stress (e.g., steel has high tensile strength). Ductility is the capacity for large plastic deformation under tension, measured by elongation and reduction in area, providing warning before failure.

## Answer

#### Strength
**Strength** is the ability of a material to resist the applied load without failure or excessive deformation. It is expressed as stress (force per unit area) and may be compressive, tensile, shear or flexural strength. Steel has high tensile strength, while concrete and stone have high compressive strength.

#### Ductility
**Ductility** is the ability of a material to undergo large plastic deformation under tension, so that it can be drawn into wires before fracture. It is measured by percentage elongation and percentage reduction in area.

$$
\text{Elongation \%} = \frac{L_f - L_0}{L_0}\times 100
$$

Mild steel, copper and aluminium are ductile. Ductility gives warning before failure and is very important for earthquake-resistant structures.

## Check yourself

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

1. Strength is expressed as
   A. energy per volume
   B. stress (force per unit area)
   C. percentage elongation
   D. temperature
   Answer: B. Strength is stress. (Key point: Strength)

2. Ductility is measured by
   A. Brinell number
   B. endurance limit
   C. percentage elongation and reduction in area
   D. specific heat
   Answer: C. These measure plastic stretch. (Key point: Ductility measure)

3. Ductility is important for earthquake-resistant structures because it
   A. makes material brittle
   B. reduces strength
   C. increases weight
   D. gives warning before failure
   Answer: D. Ductile members deform visibly before failing. (Key point: Importance)

## Related in other subjects

- [Earthquake design philosophy, strength and ductility](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Aearthquake-design-philosophy-strength-and-ductility) — Design of RCC Structure, chapter 12
- [Internal hinge properties; point of contraflexure](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Ainternal-hinge-contraflexure) — Strength of Materials, chapter 1