1 / 17

Using Wavelets for Detection of Damage in a Beam from a Calibrated Vehicle

This presentation discusses the rational behind using wavelets for damage detection in bridges. It covers the technique of wavelet transform and its performance with different wavelets.

omerj
Download Presentation

Using Wavelets for Detection of Damage in a Beam from a Calibrated Vehicle

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. USING WAVELETS ON THE RESPONSE OF A BEAM TO A CALIBRATED VEHICLE FOR DAMAGE DETECTION David Hester Arturo Gonzalez Nantes, 2nd July 2009

  2. Overview of presentation • Rational behind research / Introduction to technique • Computer models used • Description of Continuous Wavelet Transform (CWT) • Performance of different wavelets • Approach for detecting small damage 01

  3. Rational behind study • Research in Structural Health Monitoring (SHM) increasing, typically requires Non Destructive Testing • Bridges are a particularly interesting set of structures, in service for long period, traffic loads are steadily increasing • Financially beneficial if service life of existing bridges can be maximised • Reliable early damage detection technique significant step toward achieving this 02

  4. Introduction to technique • Ultimately would like to be able to detect damage in a bridge by monitoring it’s dynamic response • Fundamental principal: Damage causes change in mechanical properties of structure • Potential to use Wavelets to detect damage in a beam by performing a wavelet transform on the deflection signal of the beam Wavelet Coefficient Wavelet Transform Deflection 03 Time Damage Deflection gauge Normalised Position of Load

  5. 2 3 1 4 Modelling of the Structural Response to a Moving Load • Discretized model of a simply supported beam L [Kg], [Mg] 04

  6. Crack Modelling • Crack = Loss of Stiffness 05

  7. Sinha’s method • Sinha approximates the exponential curve of Christides and Barr with a straight line. • lc= 1.5d Load Modelling Vehicle modelled as a constant moving Load [Mg]{d2y/dt2}+[Kg]{y}={F} 06

  8. Introduction to wavelets • Wavelet transform was developed to extract Time-Frequency information from a signal • A wavelet is a waveform of limited duration Mexican hat Db 5 Gauss 2 Morlet 07 Figures taken from MATLAB

  9. Outline of Wavelet Transform • Wavelet compared to a section at start of the original signal • Calculate wavelet coefficient ‘C’, which represents how closely correlated the wavelet is with this section of the signal. • Shift the wavelet to the right and repeat steps 1 & 2 • Scale (stretch) the wavelet and repeat steps 1 through 3 • Repeat steps 1-4 for all scales. Result of the WT are many wavelet coefficients ‘C’ 08 Figures taken from MATLAB

  10. Using wavelets to detect damage • Wavelets can detect local discontinuities in a signal • Discontinuity in deflection-time response of a bridge as load passes over cracked section • Basic principal is to use wavelet to detect the discontinuity in the signal and thereby locate damage 09

  11. Mid-span deflection response of a beam cracked at the 1/3 point subject to moving P-Load (1st beam freq=0.9Hz) 10 Deflection sensor Crack

  12. WT applied to the midspan deflection signal of a beam subject to P-Load. Beam has a crack at 1/3rd point, Wavelet Transform Deflection Signal Scale=27 ≈ 0.9Hz Increase in wavelet coefficients at 0.33L →There is a localised discontinuity in deflection signal at 0.33L →There is damage at 0.33L 11

  13. Performance of different wavelets in detecting damage 12 Gauss 2 Mex hat

  14. Coefficient line plot Delta= Crack height / Beam depth Delta=0.2 Delta=0.4 Delta=0.6 Damage at 1/3 point 13

  15. Improvement by using multiple measurements • Use of one single measurement, delta=0.2 • Use of multiple measurements Min not at damage location Deflection Sensors Average Crack Min at damage location 14

  16. Conclusions • Possible to use a moving load as a form of non destructive testing to detect damage • Wavelet transform applied to Deflection-Time response can identify and locate damage • In presence of noise detects large cracks relatively easily • Multiple measuring locations give better results when detecting small cracks Locate Damage Wavelet Transform 15 Deflection Signal Deflection Gauge Crack

  17. Acknowledgements • This investigation has been carried out as part of work program 7 of the ASSET project, Sustainable Surface Transport ASSET(Advanced Safety and Driver Support in Efficient Road Transport), 16

More Related