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Non-destructive testing (NDT) of concrete structures is performed using pulse-echo methods. According to the type of the applied waves it can be classified as acoustic (Impact-Echo, Ultrasonics) and electromagnetic methods (Radar). The results are visualised through different imaging processes. This work is performed in the frame of a research project promoted by Deutsche Forschungsgemeinschaft (FOR384).The objective of data fusion is to use the complementary information of the different methods. Radar can detect metallic reflectors in concrete (metallic ducts and concrete reinforcement) very well. This method is not able to locate defects behind these reflectors (injecting defects, defects behind close concrete reinforcement), because the electromagnetic waves are completely reflected at metals. The acoustic methods are able to compensate this deficit i.e. acoustic waves can penetrate through metal. But acoustic waves in the ultrasonic range are completely reflected by air layers. Air layers have smaller influence on radar propagation, so that both methods complement each other.In order to be able to combine the NDT-data from several methods records at the same volume, the different data setsmodes of signals must be adapted. The ultrasonic and radar data have to be reconstructed with programs based on the Synthetic Aperture Focusing Technique (SAFT) before data fusion. Subsequently, a conversion of the data into a uniform format has to be carried out. This is a prerequisite in order to keep the data exchange between the project partners as simple as possible. After the data sets are imported and transferred into a common reference system, they can be processed with operations according to the purpose of the investigation. Results, which have been achieved in concrete test specimen with radar and ultrasonics, will be presented and will show the feasibility of the data fusion method.
NDT of Concrete Structures
(2002)
Assessment of post tensioned concrete bridges applying automated non-destructive testing systems
(2005)
Zusammenfassung:
Die zerstörungsfreie Untersuchung von Spannbetonbauwerken mit Radar, Impact-Echo und Ultraschallecho konzentriert sich auf die Ortung von Bewehrung und, wegen der damit verbundenen Korrosionsgefahr, auf
die Lokalisierung von Verpressfehlern in Spannkanälen. Für die automatisierte Untersuchung großer Flächen wurden in der BAM Bundesanstalt für Materialforschung und prüfung Scannersysteme entwickelt und an mehreren Brückenbauwerken erprobt. Die Messdaten der drei angewendeten Verfahren werden eingehend bearbeitet und miteinander kombiniert. Durch die Kombination der Verfahren kann sowohl die schlaffe Bewehrung als auch Spannbewehrung geortet und können Hinweise auf Verpressfehler gegeben werden.