Hostname: page-component-78c5997874-j824f Total loading time: 0 Render date: 2024-11-08T08:35:28.384Z Has data issue: false hasContentIssue false
  • English
  • Français

Detecting Rebars and Tubes Inside Concrete Slabs Using Continuous Wavelet Transform of Elastic Waves

Published online by Cambridge University Press:  05 May 2011

C. H. Chiang  and
C. C. Cheng
C. H. Chiang*
Affiliation:
Department of Construction Engineering, Chaoyang University of Technology, Wufong, Taichung, Taiwan 413, R.O.C.
C. C. Cheng*
Affiliation:
Department of Construction Engineering, Chaoyang University of Technology, Wufong, Taichung, Taiwan 413, R.O.C.
*
* Associate Professor
* Associate Professor
Get access

Abstract

A typical problem of elastic wave methods, such as the impact echo method, is due to peak detection based solely on amplitude spectrum. Current study aims to improve the feature identification of impact-echo signals obtained from buried objects in concrete slabs. Steel rebar, steel tubes, and PVC tubes embedded in a concrete slab are tested. Numerical simulations are carried out based on models constructed using the finite element method. The received signals, both experimental and simulated, are analyzed using both fast Fourier transform and continuous wavelet transform (CWT). The amplitude spectra can only provide global information and lose some important local effects of frequency components. This can be resolved by continuous wavelet transform for preserving the transient effects in the frequency domain. Localized spectral contents are analyzed and thus better understanding is achieved for the impulse responses due to different objects below the surface of the concrete slab. Features related to steel rebar, PVC and steel tubes are readily identified in the coefficient plot of wavelet coefficients. Multiple reflections and vibration modes related to various characteristics of wave propagation in the concrete slab can now be decomposed into distinctive frequency bands with different time durations. The result of CWT provides more information and is easier to interpret than that of the spectral analysis. The same peak frequency found in the amplitude spectrum is now distinguishable between PVC and steel tubes at a resolution of 0.1kHz or better. Such findings provide a more effective way to pick up true rebar signals using the impact-echo method.

Keywords

lmpact echoWaveletConcrete.
Type
Technical Note
Information
Journal of Mechanics , Volume 20 , Issue 4 , December 2004 , pp. 297 - 302
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2004

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1.Newland, D. E., “Ridge and Phase Identification in the Frequency Analysis of Transient Signals by Harmonic Wavelets,” J. Vibration and Acoustics, 121, pp. 149–155 (1999).CrossRefGoogle Scholar
2.Mallat, S., A Wavelet Tour of Signal Processing, 2nd Ed., Academic Press, San Diego (1999).Google Scholar
3.Cheng, C. C. and Sansalone, M., “Effects on Impact-Echo Signals Caused by Steel Reinforcing Bars and Voids around Bars,” ACIMaterials Journal, 90, pp. 421–423 (1993).Google Scholar
4.Teolis, A., Computational Signal Processing with Wavelets, Birkhuser, Boston, pp. 65–67 (1998).CrossRefGoogle Scholar
5.Zhang, G-M., Hou, C-G., Wang, Y-W., and Zhang, S-Y., “Optimal Frequency-to-Bandwidth Ratio of Wavelet in Ultrasonic Non-Destructive Evaluation,” Ultrasonics, 39, pp.13–17 (2001).CrossRefGoogle Scholar
6.Chiang, C-H., Gi, Y-F., Pan, C-L., and Cheng, C.C., “Elastic Wave Propagation in Concrete and Continuous Wavelet Transform,” 31st Annual Review of Progress in Quantitative Nondestructive Evaluation, July 25–30, Golden, Colorado, U.S.A.Google Scholar