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- Impact-Echo (7)
- Radar (6)
- Impact-echo (4)
- EFIT (3)
- Geometry Effects (3)
- Nondestructive Testing (3)
- Ultrasonic echo (3)
- Automatisierte ZfPBau-Verfahren (2)
- Concrete (2)
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Identification of short transient signals within impact-echo data using the Hilbert-Huang-Transform
(2005)
Automated NDE of post-tensioned concrete bridges using radar, ultrasonic echo and impact-echo
(2006)
Impact echo is an acoustic method based on the use of transient stress waves generated by an elastic impact; it is used for nondestructive testing of concrete structures. In practical applications, the signals obtained often are superimposed by further mechanical vibrations and the so-called geometry effects, which are caused mainly by surface waves. Because of attenuation in the concrete as well as the divergence of the acoustical waves, impact echo signals are transient. As a result, the frequency content changes over time. Normally the analysis is carried out on the Fourier power spectrum of the signal. However, the Fourier spectrum is still affected by the mentioned effects and has well-known deficiencies for short transient signals within longer time sweeps. Application of the Hilbert-Huang transform is presented as a refined method for the time-frequency analysis of nonstationary impact echo data. The basic properties of the method and its practical application for time-frequency analysis of impact echo data, signal filtering, and pattern identification are presented.
The European infrastructure asset has developed historically and is characterized by nation-specific construction processes. Inspection, condition assessment, and maintenance procedures differ from country to country. Because of historical and political circumstances, national infrastructure assets are maintained at different levels, too. Since the budget for maintaining the bridge infrastructure less and less meets the demands of a growing bridge stock, bridge inspection, maintenance, and life-cycle considerations gain higher importance. The need exists to develop effective diagnosis tools for early detection of construction faults, defects, and deterioration processes during inspection, to keep the bridge infrastructure at an acceptable level, from structural safety and economic viewpoints. An overview on the latest research projects and integrated bridge management systems in Europe is given. The potentials of nondestructive testing (NDT) are presented, with special focus on technical advances of NDT applications to reinforced concrete (RC) and posttensioned concrete bridges. Although NDT is not regularly integrated in these processes, the application brings valuable information on the current condition of the inner structure in called-in special inspections. NDT-automation and the application of imaging echo methods, combined with advanced data processing, produce a surprising level of information about the inner structure of massive RC slabs up to a depth of about 60 cm. Detected inhomogeneity and scatterers of acoustic or electromagnetic waves can be visualized in vertical or horizontal slices through the structure or animations. The fusion of different three-dimensional data sets of processed data improves the interpretability and accuracy of the results.