NDT parameters for fatigue damage identification in structural elements

The focus of this test is to establish correlations of NDT parameters (e.g. ultrasonic velocity, attenuation) to fatigue related phenomena and parameters to identify any fatigue damaging process (i.e. the formation of microcracks in concrete, slow microcrack progagation in steel elements) in structural elements and components at the earliest possible stage. This includes lab investigations using ultrasonic, acoustic emission methods and fibre optic in the laboratory to measure microcrack formation in materials due to fatigue, numerical simulation of observed phenomena on the micro level of material behaviour to investigate the existence of a fatigue endurance limit and application of the developed technology on an existing wind turbine tower and bridge deck slab at the most fatigue prone zones.

Host Institution

EPFL – Swiss Federal Institute of Technology Lausanne, Switzerland

ESR4

Imane Bayane

Local academic supervisor

Prof. Dr. Eugen Brühwiler (EPFL)
eugen.bruehwiler(at)epfl.ch 
Tel: +41 21 693 2882  

Industrial co-supervisor

Piotr Klikowicz (NeoStrain)
piotr.klikowicz@neostrain.pl
Tel: +48 506 175 545   

PhD enrolment

EPFL – Swiss Federal Institute of Technology Lausanne, Switzerland
PhD Director: Eugen Brühwiler

Start date: 1st February 2017
Duration: 36 months

Synopsis

The service duration of structures like reinforced concrete bridges and wind turbines depends on the fatigue of structural components due to respectively traffic loading and wind action. In order to realistically evaluate fatigue damage, Non-Destructive Testing methods would be a real asset. In this project, ultrasonic sensor networks shall be used to detect and monitor fatigue damage in reinforced concrete of bridges subjected to traffic induced fatigue loading. Fatigue damage may be identified and analysed from microcracking in the bulk concrete material due to fatigue cracking in steel reinforcing bars that are usually the determinant fatigue vulnerable element in reinforced concrete. Fatigue damage determined from NDT shall be related to fatigue action effects.  

Objectives

The general objective is to correlate NDT parameters (e.g. ultrasonic velocity, attenuation, fibre optic) to fatigue related phenomena and parameters to identify any fatigue damaging process (i.e. the formation of microcracks in concrete, slow microcrack propagation in steel elements) in structural elements and components at the earliest possible stage. Novel ways to analyse ultrasonic data in terms of damage shall be developed and imaging techniques shall be extended to structural field applications.

Tasks and methodology

  • Laboratory testing using ultrasonic, acoustic emission and fibre optic methods to measure microcrack formation in materials (concrete, steel rebars) due to fatigue.
  • Numerical simulation of observed phenomena on the micro level of material behaviour to investigate the existence of a fatigue endurance limit.
  • Application of the developed technology on an existing wind turbine tower and bridge deck slab at the most fatigue prone zones.

Results

  • Novel NDT methodology validated and applicable for the fatigue damage monitoring on structural elements and components of bridges and wind turbine towers.
  • Implementation at a real structure.
  • 3 (accepted) peer-reviewed papers.
  • Successfully defended PhD thesis.

Dissemination

  • Three peer reviewed papers.
  • Two presentations at national/international conferences.
  • Presentations at workshops and for potential end-users.

Secondments

  • BAM (Berlin, Germany)
    August & September 2017
    NDT: ultrasound and acoustic emission methods
  • IFSTTAR (Marne-la-Vallée, France)
    December 2017 & January 2018
    Fibre optics NDT method
  • NeoStrain (Krakow, Poland)
    April 2018
    Structural Health Monitoring

Research field

Non-Destructive Testing, wave methods, fatigue of reinforced concrete, structural health monitoring

Keywords

Non-Destructive Testing, ultrasonic methods, monitoring, reinforced concrete, fatigue

Key publications

There are no single key publications but a series of easy to access papers on:

  • The fatigue behaviour of concrete and steel rebars
  • Ultrasonic testing methods to detect microcracking