---
title: "Fatigue effect in concrete"
subject: "Concrete Technology and Masonry Structure"
chapter: 4
key: "semester_5/concrete_technology_and_masonry_structure:fatigue-effect"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/fatigue-effect
site: BCT Engineering
---

# Fatigue effect in concrete

Concrete Technology and Masonry Structure · Chapter 4: Properties of hardened concrete

- Asked in: 2071 Shrawan, 2 marks
- Video: [Experimental Study of Structural Concrete’s Fatigue Capacity](https://www.youtube.com/watch?v=Hr1ftlZ4Sf0) — American Concrete Institute
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/fatigue-effect
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-4

## Question

What is fatigue effect in concrete?

## Short answer

Fatigue effect is the loss of strength and eventual failure under repeated or fluctuating loads even below static strength, due to cyclic microcrack growth. For 10 million cycles, fatigue strength is about 50–55% of static strength, shown by S-N curves, critical in structures like bridges, pavements, and machine foundations.

## Answer

Fatigue effect is the loss of strength and eventual failure of concrete under repeated or fluctuating loads, even though the maximum stress is lower than the static strength. Microcracks at the aggregate-paste interface grow with each cycle until they join and cause rupture.

The fatigue strength of concrete for 10 million cycles is about 50 to 55% of its static strength (compressive or flexural). It is shown by an S-N curve and is important in bridges, pavements, crane girders and machine foundations.

## Check yourself

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

1. Fatigue effect is:
   A. failure under a single overload
   B. strength loss and failure under repeated loads below static strength
   C. shrinkage under drying
   D. time-dependent strain under constant load
   Answer: B. Repeated loading causes progressive damage. (Key point: Fatigue effect)

2. Fatigue failure occurs because:
   A. microcracks at the aggregate-paste interface grow each cycle and join
   B. aggregate melts
   C. cement hydrates faster
   D. water freezes
   Answer: A. Cycle-by-cycle crack growth leads to rupture. (Key point: Mechanism)

3. Fatigue strength at 10 million cycles is about:
   A. 90%
   B. 5%
   C. 50 to 55% of static strength
   D. 120%
   Answer: C. Shown on an S-N curve. (Key point: 10 million cycle strength)

## Related in Concrete Technology and Masonry Structure

- [Fatigue and impact strength of concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Afatigue-impact-strength) — Concrete Technology and Masonry Structure, chapter 4
- [Shrinkage and creep of concrete](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Ashrinkage-and-creep) — Concrete Technology and Masonry Structure, chapter 4, asked 6×
- [Effect of water cement ratio on strength](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Awc-ratio-effect-strength) — Concrete Technology and Masonry Structure, chapter 3, asked 4×
- [Transition phase and its effect](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Atransition-zone-effect) — Concrete Technology and Masonry Structure, chapter 2
- [Effect of gel/space ratio on strength](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Agel-space-ratio-effect) — Concrete Technology and Masonry Structure, chapter 4
- [Platen restraint effect and failure modes](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aplaten-restraint-effect) — Concrete Technology and Masonry Structure, chapter 5