Ultrasonic fatigue testing of concrete

Michael Fitzka,Ulrike Karr,Maximilian Granzner,Tomáš Melichar,Martin Rödhammer,Alfred Strauss,Herwig Mayer

doi:10.1016/j.ultras.2021.106521

Abstract

Cyclic compression fatigue properties of concrete are studied with the ultrasonic fatigue testing method with cycling frequency 19 kHz and are compared to servo-hydraulic tests performed at 60 Hz. Ultrasonic testing was found applicable for rapid generation of very high cycle fatigue (VHCF) data of concrete. Fatigue cracks can be initiated, however specimens do not rupture, since cyclic stresses decrease with increase of compliance in displacement controlled ultrasonic tests. Observation of resonance frequency, analysis of higher order harmonics of vibration, and computed tomography of specimens are successful methods to analyse fatigue damage. Calorimetric evaluations can be used to calculate the cyclic irreversible strain, which is about 1% of the elastic strain in the ultrasonic VHCF test.

Highlights

Concrete is increasingly used in structures, where cyclically varying loads besides static stresses are present
Numerous repetitive loads are imposed on concrete structures e.g. by engine vibrations applying forces on fundaments, gravitational and acceleration forces of motor vehicles stressing pavements and bridges, forces caused by gusts of wind or pe riodic impact forces of sea waves
Concrete specimens with a diameter of 21 mm and a length of 35 mm (Fig. 3, right) were cycled sinusoidally between a minimum compression stress, σmin, of 5 MPa and a maximum compression stress, σmax, during a load cycle between 37 % and 75 % of the compressive strength σdB

Summary

Introduction

Concrete is increasingly used in structures, where cyclically varying loads besides static stresses are present. Numerous repetitive loads are imposed on concrete structures e.g. by engine vibrations applying forces on fundaments, gravitational and acceleration forces of motor vehicles stressing pavements and bridges, forces caused by gusts of wind or pe riodic impact forces of sea waves. The number of load cycles acting on concrete structures can be very high. Concrete bridges [5], offshore structures [6], and foundations of wind turbines [8] can accumulate more than 108 load cycles during their lifetimes. Understanding of the fatigue properties of concrete in the very high cycle fatigue (VHCF) regime (i.e. above 107 cycles) is necessary for safe design of components

Methods

Results

Conclusion