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Mit Radar, Impact-Echo und Ultraschallecho wurden 2004/2005 zwei Spannbetonbrücken der stark befahrenen A 23 Südosttangente in Wien zerstörungsfrei untersucht. Bei den Bauwerken handelt es sich um Hohlkastenbrücken, die 1975/76 unter Verwendung unterschiedlicher Spannsysteme errichtet wurden. Durch Messungen mit den zerstörungsfreien Prüfverfahren an den Außenseiten zweier Hohlkastenstege wurde sowohl die schlaffe Bewehrung als auch Längsspannglieder in den Stegen geortet. Darüber hinaus sollte der Verpresszustand der Spannglieder mit Hilfe der akustischen Verfahren Impact-Echo und Ultraschallecho ermittelt werden.
Zusammenfassung
Die Laser Induced Breakdown Spectroscopy (LIBS) ist eine analytische Methode mit der die Elementverteilung auf der Oberfläche von Proben orts- und tiefenaufgelöst ermittelt werden kann. Ein intensiver, infraroter Laserstrahl wird auf die Oberfläche fokussiert. Durch die hohe Energiedichte werden einige Mikrogramm Material verdampft und ein Plasma gebildet. Bei der Ausdehnung und Abkühlung des Plasmas wird die charakteristische Fluoreszenz der verdampften Elemente abgestrahlt und mit spektroskopischen Mitteln analysiert. Die Empfindlichkeit der Methode liegt im ppm-Bereich, die typische Messgenauigkeit beträgt einige Prozent. Die Ergebnisse liegen quasi on-line vor, es ist keine Probenpräparation notwendig und die Apparatur ist vor Ort einsetzbar.
Im Artikel werden Anwendungen der LIBS zur Untersuchung von Baustoffen beschrieben. Die Ergebnisse der Ermittlung der Salzverteilung in Baustoffen, der Untersuchung der Betonzusammensetzung und dem Nachweis von hydrophobierten Schichten auf unterschiedlichen Baustoffen werden vorgestellt.
For the investigation of the complex inner structure of historic buildings, the application of radar has been increased during the last ten years. Although historic masonry in general is very inhomogeneous and although in some cases high absorption occurs due to enhanced moisture, radar has been successfully applied to get information on geometry, position of inclusions and about kind and size of existing damages. In this paper case studies will be presented concerning the localisation of metallic inclusions and the investigations of the structure of an exterior wall with a multiple leaf structure.
Ortung von Hohlstellen und Ablösungen in Betonkonstruktionen mit Radar und Impuls-Thermografie
(2003)
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.
Im Rahmen eines FE-Projektes “Inspektion Fester Fahrbahnen“ der BAM und der Deutschen Bahn AG geht es um die Anwendung und weitere Entwicklung zerstörungsfreier Messverfahren zur Beurteilung des Zustandes Fester Fahrbahnen.
Nach ersten Versuchsreihen direkt im Gleis wurden für verschiedene Bauarten die charakteristischen Herstellungsbedingungen simuliert und systematisch untersucht. Die kombinierte Anwendung der drei Messverfahren Ultraschall-Array-, Impakt-Echo- und Impuls-Radar-Verfahren wird hier an dem Beispiel “Betonschwelle in Betoneinbettung” dargestellt.
Application of laser induced breakdown spectroscopy for the detection of hydrophobic coatings
(2001)
Im Rahmen von Ertüchtigungsmaßnahmen an Spannbetonbrücken werden häufig Kernbohrungen durchgeführt, die die vorhandenen Spannbewehrungen nicht beschädigen dürfen. Die Zerstörungsfreie Prüfung (ZfP) kann einen wesentlichen Beitrag leisten, das Risiko einer Beschädigung zu minimieren und somit eine bessere Planungssicherheit für die Ertüchtigungsmaßnahmen zu schaffen. Typische ZfP-Verfahren für das Auffinden von vorgespannter Bewehrung sind das Radar- und das Ultraschallverfahren. Am Beispiel der Ertüchtigung einer Brücke in Bremen wird die Vorgehensweise beschrieben, und es werden die Grenzen der Verfahren aufgezeigt.
The delamination of concrete slabs is the separation along a plane roughly parallel to, and generally near, the surface. Corrosion-induced delamination is a common problem in old concrete bridge decks. If undetected, delaminations could expand, reach the surface, and result in spalling. Early detection of delamination is necessary for planning timely repairs that prevent costly deck replacement projects. Most bridge owners rely on routine visual and traditional surveys of bridge deck conditions. These surveys are highly subjective and can locate only large shallow delaminated zones. Several nondestructive testing (NDT) techniques have recently been employed for bridge deck evaluation to obtain more objective and comprehensive assessment. The reliability of applicable methods needs to be established before a greater role for NDT in routine inspections can be encouraged. This paper presents a validation study aimed at evaluating the effectiveness of three NDT techniques, namely impact echo, ultrasound (US) echo, and US linear array, in detection of delamination. This study is unique because the subject test specimens were deteriorated bridge deck segments preserved from the demolition of a prestressed box girder bridge. The results of the tests conducted on one of the specimens are presented and discussed here: impact echo provided satisfactory overall assessment, but the individual results were often difficult to interpret; US echo detected deep delaminations but not shallow ones; and US linear array located the extent of deep delaminations and provided indications of shallow ones.
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.
Complex resistivity (CR) behavior of building material - first results of field scale measurements
(2008)
Radar und Datenfusion
(2007)