TY - JOUR A1 - Grohmann, Maria A1 - Müller, Sabine A1 - Niederleithinger, Ernst A1 - Sieber, S. T1 - Reverse time migration: introducing a new imaging technique for ultrasonic measurements in civil engineering JF - Near Surface Geophysics N2 - Ultrasonic echo testing is widely used in non-destructive testing in civil engineering to investigate concrete structures, to measure thickness, and to locate and characterise built-in components or inhomogeneities. Currently, synthetic aperture focusing techniques are mostly used for imaging. These algorithms are highly developed but have some limitations. For example, it is not possible to image the lower boundary of built-in components like tendon ducts or vertical reflectors. We adopted reverse time migration for non-destructive testing in civil engineering in order to improve the imaging of complicated structures in concrete. By using the entire wavefield, including waves reflected more than once, there are fewer limitations compared to synthetic aperture focusing technique algorithms. As a drawback, the required computation is significantly higher than that for the techniques currently used. Simulations for polyamide and concrete structures showed the potential for non-destructive testing. The simulations were followed by experiments at a polyamide specimen. Here, having acquired almost noise-free measurement data to test the algorithm, we were able to determine the shape and size of boreholes with sufficient accuracy. After these successful tests, we performed experiments at a reinforced concrete foundation slab. We obtained information from the data by reverse time migration, which was not accessible by traditional imaging. The imaging of the location and structure of the lower boundary of the concrete foundation slab was improved. Furthermore, vertical reflectors inside the slab were imaged clearly, and more flaws were found. It has been shown that reverse time migration is a step forward in ultrasonic testing in civil engineering. KW - Ultrasonic echo technique KW - Reverse time migration PY - 2017 DO - https://doi.org/10.3997/1873-0604.2017006 SN - 1569-4445 SN - 1873-0604 VL - 15 IS - 3 SP - 242 EP - 258 PB - Wiley AN - OPUS4-41921 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Katzenbach, R. A1 - Klingmüller, O. A1 - Hillmann, S. A1 - Willmes, Michael T1 - REFUND: Untersuchung von Bestandsgründungen für eine Entscheidung zur Wiedernutzung T1 - REFUND: Investigation of existing foundations and decision making before re-use JF - Bautechnik N2 - Vor einer geplanten Weiter- oder Wiedernutzung von Bestandsgründungen stellt sich die Frage nach deren Lage, Geometrie und Zustand im Untergrund. Hierfür gibt es verschiedene Prüfverfahren. Die Abläufe bei Planung und Prüfung sind jedoch bisher nicht standardisiert und die Möglichkeiten bzw. Grenzen der Prüfverfahren den Planern wenig bekannt. Im Forschungsprojekt REFUND (2014–2016) wurden unter Berücksichtigung der aktuellen Normen und des Stands der Technik Ablaufdiagramme für die Planung der Wiedernutzung sowie die Untersuchung des Bestands entwickelt. Dies geschah getrennt für Einzel- und Streifenfundamente, Platten und Pfähle. An zwei Praxisbeispielen wurden die Abläufe getestet und optimiert. Die Ergebnisse wurden in einem Handbuch zusammengefasst. Es soll Planer und andere Verantwortliche bei der wirtschaftlich und technisch optimierten Durchführung von Wiedernutzungsprojekten unterstützen. N2 - Before re-using existing foundations they have to be investigated for position, geometry and condition in the subsurface. The procedures and protocols haven't been standardized yet. Capabilities and limitations of appropriate testing methods are not known to all stakeholders. In the frame of the research project REFUND (2014-2016) we have developed decision trees for the planning and the investigation process, separately for single and strip foundations, slabs and piles. The protocols were tested in line with two actual projects. The results have been compiled in a handbook, which will support planners and other participants in a technical and economical optimized way to perform re-use of foundations. KW - Fundament KW - Wiedernutzung KW - Entscheidung KW - Zerstörungsfrei PY - 2017 DO - https://doi.org/10.1002/bate.201700038 SN - 1437-0999 VL - 94 IS - 10 SP - 676 EP - 681 PB - Ernst & Sohn CY - Berlin AN - OPUS4-42615 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -