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- Radar (19)
- Impact-Echo (11)
- Ultraschallecho (11)
- Spannbetonbrücken (9)
- Automatisierte ZfPBau-Verfahren (7)
- Data fusion (6)
- Impact-echo (6)
- Ultrasonic echo (6)
- Non-destructive testing (5)
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Eingeladener Vortrag
- nein (4)
Die Kenntnis der Leistungsfähigkeit von zerstörungsfreien Prüfverfahren
im Bauwesen (ZfPBau-Verfahren) ist eine wichtige Grundlage für deren
zunehmende Akzeptanz in der Baupraxis. Insbesondere bei Radar wird von Anwendern
immer wieder nachgefragt, bis in welche Tiefe, bei welchem Betonalter und
mit welcher Antennenfrequenz schlaffe Bewehrung zuverlässig geortet werden
kann. Die Frage nach der Eindringtiefe in Bezug zum Betonalter ist insofern von
Bedeutung, dass eine erfolgreiche Anwendung an Bestandsbauwerken an vergleichbaren
Bauteilen aus jungem Beton misslingen kann, wenn die Anwendungsgrenzen
von Radar an jungem Beton nicht richtig eingeschätzt werden. Da in realen
Bauteilen der Bewehrungsgehalt stark differiert, ist für den Anwender auch von
Interesse, wie sich die Zuverlässigkeit des Verfahrens mit zunehmender Verlegedichte
der oberflachennahen Bewehrung ändert.
In diesem Beitrag werden systematische Untersuchungen an Stahlbetonbauteilen mit
Bewehrungsstäben in variierender Verlegetiefe bei zunehmendem Betonalter und
zunehmender Verlegedichte der oberflächennahen Bewehrung vorgestellt. Die
Untersuchungen erfolgten unter Verwendung von Radarantennen mit Signalmittenfrequenzen
von 1,2 GHz-, 1,6 GHz- und 2,3 GHz. Die Dielektrizitätszahl εr
wird bezüglich ihrer Streuung im Bauteil quantifiziert. Daraus ergeben sich ebenso
Kenntnisse über die Streuung der Wellenausbreitungsgeschwindigkeit, die beim
Einsatz von Migrationsalgorithmen von großer Bedeutung sind.
Die Ergebnisse zum Eindringverhalten von Radar werden dem Anwender quantitativ
in Abhängigkeit vom Betonalter und der Signalmittenfrequenz der Radarantennen
zur Verfügung gestellt. In tabellarischer Form bieten die Ergebnisse so eine
wichtige Orientierungshilfe für Untersuchungen an neu errichteten Stahl- und
Spannbetonbauteilen und können als Ergänzung des DGZfP-Merkblatts B10 dienen.
The introduction of an innovative process for non-destructive testing is described in terms of its different phases and how the process is controlled in the Fraunhofer IZFP in order to obtain optimal results. Examples are discussed of applications by IZFP in various important and safety-relevant industrial sectors where the automated inspection systems were introduced. These case studies include the inspection of railway components such as the wheel sets of the German high-speed train and in-line pipe inspection by using intelligent pipeline inspection gauges. Complex inspection systems, both hardware and software, developed in partnership with the Federal Institute for Materials Research and Inspection (BAM), were applied to inspection tasks in civil engineering. Two automated systems based on a robot and on a flexible manipulation are presented. Both systems can be applied to diverse inspection technologies and to the data fusion of various types of non-destructive testing (NDT) data.
This paper presents the progress of successful location of grouting faults in tendon ducts with ultrasonic imaging. The examples were obtained in the research group FOR 384 funded by DFG (German Research Foundation). The co-operation of experimental research and modeling allowed imaging and identification of grouted and ungrouted areas of tendon ducts (including strands) in a large test specimen (40 m²). In addition to the criteria for indicating grouting faults in post-tensioned ducts known until now the phase evaluation of reflected ultrasonic pulses is described. Experiments and modeling of wave propagation are presented for reflections at metal plates in concrete (thickness range 0.5 mm to 40 mm) and for tendon ducts including strands.
The main part of the progress was achieved by automated measurements using dry contact transducers, 3D-SAFT reconstruction including phase evaluation and modeling considering wave propagation for typical elastic parameters and exact experimental site conditions. The results for shear waves as well as for pressure waves are compared in the frequency range from 50 kHz to 120 kHz.
Influence of concret properties on the calibration of radar, ultrasonics and active thermography
(2008)
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.