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- 2002 (17) (entfernen)
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- Englisch (17) (entfernen)
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- Impact-Echo (3)
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Eingeladener Vortrag
- nein (7)
NDT of Concrete Structures
(2002)
NDT-CE in Civil Engineering
(2002)
Rapid and accurate non-destructive evaluation (NDE) techniques are needed to assess the in-place condition of concrete structures. However the time and effort required to perform NDE tests using conventional surface-mounted contact sensors hinder rapid evaluation of full-scale structures. The authors are cooperating in research to develop rapid and robust methods that collect mechanical wave signals from concrete structures and to characterize defects in concrete
using that signal data. The suitability of surface waves and laser-based, non-contact wave detection techniques for this purpose are examined here. After a brief introduction to non-contact sensing, an experimental set-up is described and results from experimental tests are presented. Mechanical surface waves in a concrete slab specimen are generated with several different conventional sources. The ability of a laser vibrometer to detect wave propagation from concrete that does not have any reflective treatment (normal concrete surface) is demonstrated, allowing the generation of ultrasonic images. Test results from a concrete specimen containing a subsurface defect are then presented. The obtained ultrasonic images illustrate some limitations of using surface waves to detect subsurface defects in concrete, although approaches to improve the results are proposed.
Improved Detection of Tendon Ducts and Defects in Concrete Structures Using Ultrasonic Imaging
(2002)
At the beginning of the 90s the general opinion was, that ultrasonic inspection methods using pulse-echo technique were not suitable for the inspection of concrete because of the inhomogeneity and the strong scattering behavior of the embedded aggregates. In the meantime the progress in the development of new equipment and inspection strategies in connection with ultrasonic imaging techniques turns the pulse-echo technique into a powerful tool to solve problems related to concrete materials. These imaging techniques - developed for the inspection of homogenous materials like steel of aluminum - could be adopted to the very low frequencies needed for concrete inspections.
NDT of Concrete Structures
(2002)