Local bending stiffness identification of beams using simultaneous Fourier-series fitting and shearography

Filip Zastavnik, Rik Pintelon, Mathias Kersemans, Wim Van Paepegem, Lincy Pyl

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1 Citation (Scopus)
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In this paper, we present a novel method for the identification of the local bending stiffness of beams. We use shearography to capture measurements of vibrating beams, so the input data for the identification is the modal slope – the differential of the modal shape. The modal slope is fitted by two Fourier-series functions, one of which is derived from a thin-beam model. The local bending stiffness is identified as the one corresponding with the best match between the measured and the two fitted modal slopes. This identification method, which we call simultaneous Fourier-series fitting, is demonstrated on numerically-generated inputs, as well as on experimental measurements. We use a flat, concave and convex beam, as well as beams with locally varying bending stiffness mimicking local damage to verify the method. It is shown that the method gives accurate results and is robust to noise. Additionally, it has advantageous properties that make it useful and practical: using this method, it is possible to perform the identification from only a sub-region of a beam and even without specifying the boundary conditions.
Original languageEnglish
Article number443
Pages (from-to)764-787
Number of pages24
Early online date17 Dec 2018
Publication statusPublished - 17 Mar 2019


  • Fourier-series fitting
  • Local bending stiffness identification
  • Shearography


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