TY - JOUR A1 - Dackermann, U. A1 - Yu, Y. A1 - Niederleithinger, Ernst A1 - Li, J. A1 - Wiggenhauser, Herbert T1 - Condition Assessment of Foundation Piles and Utility Poles Based on Guided Wave Propagation Using a Network of Tactile Transducers and Support Vector Machines N2 - This paper presents a novel non-destructive testing and health monitoring system using a network of tactile transducers and accelerometers for the condition assessment and damage classification of foundation piles and utility poles. While in traditional pile integrity testing an impact hammer with broadband frequency excitation is typically used, the proposed testing system utilizes an innovative excitation system based on a network of tactile transducers to induce controlled narrow-band frequency stress waves. Thereby, the simultaneous excitation of multiple stress wave types and modes is avoided (or at least reduced), and targeted wave forms can be generated. The new testing system enables the testing and monitoring of foundation piles and utility poles where the top is inaccessible, making the new testing system suitable, for example, for the condition assessment of pile structures with obstructed heads and of poles with live wires. For system validation, the new system was experimentally tested on nine timber and concrete poles that were inflicted with several types of damage. The tactile transducers were excited with continuous sine wave signals of 1 kHz frequency. Support vector machines were employed together with advanced signal processing algorithms to distinguish recorded stress wave signals from pole structures with different types of damage. The results show that using fast Fourier transform signals, combined with principal component analysis as the input feature vector for support vector machine (SVM) classifiers with different kernel functions, can achieve damage classification with accuracies of 92.5% ± 7.5%. KW - Structural Health Monitoring KW - Non-Destructive Testing KW - Sensor network KW - Support vector machine KW - Utility poles PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-434868 UR - http://www.mdpi.com/1424-8220/17/12/2938 DO - https://doi.org/10.3390/s17122938 SN - 1424-8220 VL - 17 IS - 12 SP - Article 2938, 1 EP - 16 PB - MDPI CY - Basel, Schweiz AN - OPUS4-43486 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Abraham, O. A1 - Mooney, M. T1 - Geophysical methods in civil engineering: Overview and new concepts N2 - Geophysical methods have been used in civil engineering for decades. The main field of application is - to no surprise – in geotechnical projects from site characterization to foundation quality assurance. For more than 25 years, ground penetrating radar (GPR) and seismic methods have found applications in structural engineering. Recently introduced geophysical methods have been adopted to ultrasonic investigations in various fields. They help to improve the quality of structural imaging and to detect small changes in concrete. An overview of the history and current use of geophysics in civil engineering is given. Selected examples of new concepts include advances in wave based imaging, quality assurance for foundations, detecting small changes in concrete as well as moisture and corrosion detection are discussed. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - Nondestructive testing KW - Civil engineering KW - Geophysics PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-344666 UR - https://www.ndt.net/?id=18260 SN - 1435-4934 VL - 20 IS - 11 SP - 1 EP - 6 PB - NDT.net CY - Kirchwald AN - OPUS4-34466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Wolf, Julia A1 - Mielentz, Frank A1 - Wiggenhauser, Herbert T1 - Using embedded ultrasonic sensors for active and passive concrete monitoring N2 - Challenging new constructions and ageing infrastructure are increasing the demand for permanent monitoring of loads and condition. Various methods and sensors are used for this purpose. But the technologies available today have difficulties in detecting slowly progressing locally confined damages. Extensive investigations or instrumentations are required so far for this purpose. In this study we present new sensors and data processing methods for ultrasonic transmission, which can be used for non-destructive long term monitoring of concrete. They can be mounted during construction or thereafter. Larger volumes can be monitored by a limited number of sensors for changes of material properties. The principles of ultrasonic transmission and influencing factors are presented. This latter include load, damages as well as environmental parameters as temperature or moisture. Various methods for data processing, e. g. coda wave interferometry are introduced. They allow the detection of very small changes in the medium. The embedded sensors are shown including mounting and operation. Application examples so far include small scale laboratory freeze-thaw experiments, localizing loads in larger concrete models, monitoring load effects on real structures as well as detecting acoustic events. Some sensors are operating already for several years. The sensors can be used as transmitter or receivers or switched between both roles. While most of the previous experiments have been active (at least one sensor serving as transmitter), new studies show that the sensors are useful as well for passive measurements, e. g. in acoustic emission or time reversal experiments. Besides application in civil engineering our setups can also be used for model studies in geosciences. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - SHM KW - Monitoring KW - Ultrasound concrete KW - Embedded sensors PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-344652 UR - http://www.ndt.net/?id=18408 SN - 1435-4934 VL - 20 IS - 11 SP - 1 EP - 4 PB - NDT.net CY - Kirchwald AN - OPUS4-34465 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Galindo Guerreros, Julio Cesar A1 - Niederleithinger, Ernst A1 - Mackens, S. A1 - Fechner, T. T1 - Quality assurance of jet grout columns with borehole seismic measurements N2 - Sealing and strengthening of the subsoil by injection is a major issue in the field of geotechnical engineering. One commonly applied method is jet grouting, which allows creating columns of grouted soil by eroding and mixing the in-situ soil with a thin cement suspension. A general difficulty linked with this method is to predict the resulting column diameter and its material strength. In this paper we illustrate the application of a newly developed non-destructive quality assurance testing tool used to determine the diameter of jet grout columns. This approach incorporates standard crosshole and downhole seismic measurements. To demonstrate its effectiveness, we tested the new approach within two-dimensional finite-difference numerical simulations. Additional field tests showed that this tool is also applicable in real site conditions. For this purpose, three jet grout columns were produced with different process parameters in a depth between 3.0 and 10 m. The evaluated diameters were within 1.0 and 1.5 m, slightly deviating from the previously predicted range by the jet grouting contractor. Moreover, we were able to detect the base of the columns at 10 m depth with no significant difficulties. On the other hand, unsaturated, partly unconsolidated sands between ground water level and surface considerably affected the seismic data, hence complicating the detection of the top of the columns. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - Jet grout KW - Seismics KW - Crosshole KW - Downhole PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-346753 UR - https://www.ndt.net/?id=18277 SN - 1435-4934 VL - 20 IS - 11 SP - 1 EP - 7 PB - NDT.net CY - Kirchwald AN - OPUS4-34675 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liao, Chun-Man A1 - Bernauer, F. A1 - Niederleithinger, Ernst A1 - Igel, H. A1 - Hadziioannou, C. T1 - Assessment of prestress loss in a large-scale concrete bridge model under outdoor condition N2 - Environmental conditions affect the accuracy of field measurements used to monitor civil structures. Previous studies have shown that measured dynamic responses often lack the sensitivity needed for effective localized damage detection. To address this issue, our study focuses on distinguishing environmental effects from damage related effects in measured data to enhance vibration-based damage identification methods. Experimentally, the problem of prestress loss in a prestressed concrete bridge model was examined. By adjusting the pre-stressing force in a large-scale concrete bridge model, cracking phenomena were observed. To demonstrate field monitoring of a large-scale prestressed structure, noise recording was performed and the measurement data was analyzed with operational modal analysis. Additionally, ultrasonic testing, known for its high sensitivity in damage localization, was used to cross-check the structural damage. Seismic and coda wave interferometry were also employed to estimate wave velocities, providing insights into the level of prestress loss and temperature sensitivity. Ultimately, these measurable wave properties help to overcome the uncertainties associated with traditional vibration-based damage detection methods. T2 - EVACES 2025 CY - Porto, Portugal DA - 02.07.2025 KW - Prestress Loss KW - NDT KW - Ambient Vibration KW - Ultrasonic Testing KW - Coda Wave Interferometry KW - Seismic Interferometry PY - 2025 SN - 978-3-031-96105-2 DO - https://doi.org/10.1007/978-3-031-96106-9_20 VL - 675 SP - 181 EP - 189 PB - Springer Nature CY - Cham AN - OPUS4-64212 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grohmann, Maria A1 - Niederleithinger, Ernst A1 - Buske, S. T1 - Bestimmung der Geometrie einer Fundamentplatte mit dem Ultraschall-Echo-Verfahren unter Anwendung geophysikalischer Migrationsmethoden N2 - Das Ultraschall-Echo-Verfahren ist ein klassisches Verfahren in der zerstörungsfreien Prüfung zur Bestimmung der Geometrie von Bauteilen. Die Prüfaufgaben beinhalten unter anderem die korrekte Dickenbestimmung der Baukörper sowie die Lokalisierung von Einbauteilen und Fehlstellen. Stand der Technik bei den Abbildungsverfahren ist die SAFT–Rekonstruktion (Synthetic Aperture Focusing Technique). Diese Verfahrensfamilie hat Schwierigkeiten bei der Darstellung von steilen Grenzflächen und komplizierten Strukturen, wie beispielsweise Stufen oder Unterkanten von Hohlräumen und Hüllrohren. Als Alternative werden seit einiger Zeit geophysikalische Migrationsmethoden evaluiert. Am Beispiel eines Stahlbetonfundamentes mit verschiedenen Bewehrungsgehalten, unterschiedlichen Dicken sowie zwei Pfahlköpfen wurden die Kirchhoff-Migration und die Reverse-Time Migration (RTM) getestet. Die strahlenbasierte Kirchhoff-Migration arbeitet ähnlich wie die SAFT-Rekonstruktion. Die RTM basiert auf der vollständigen Wellengleichung. In einem ersten Schritt wurden die Methoden an einem synthetischen, auf der akustischen Wellengleichung basierenden zweidimensionalem Modell getestet. Im zweiten Schritt wurden reale Messdaten, die mit Scherwellenprüfköpfen an der Fundamentplatte aufgenommen wurden, bearbeitet. Der Einsatz eines Scannersystems vereinfachte die Messungen. Die Experimente, die in diesem Manuskript vorgestellt werden, sind von bedeutendem Interesse für die Evaluierung geophysikalischer Migrationsmethoden an analogen Modellen. Ein Vergleich der Migrationsergebnisse mit den bisherigen SAFT-Ergebnissen zeigt insbesondere für die RTM eine deutliche Verbesserung in der Abbildung der Bauteilgeometrie. Vertikale Kanten konnten dargestellt sowie die Lage und Struktur der Rückwände exakter reproduziert werden. Grenzen bestehen noch bei der Darstellung der Pfahlköpfe, da die von dem zylinderförmigen Pfahl kommenden Signale verrauscht sind. Ursachen dafür sind u.a. die Bewehrung, Randeffekte sowie Mehrfachreflexionen an dem Pfahlschaft. T2 - DGZfP-Jahrestagung 2014 CY - Potsdam, Germany DA - 26.05.2014 PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-320249 SN - 978-3-940283-61-0 IS - DGZfP-BB 148 SP - Poster 10, 1 EP - 8 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) AN - OPUS4-32024 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - Neue Ideen für die zerstörungsfreie Prüfung von Beton: Seismische Interferometrie und mehr N2 - Ultraschallverfahren haben sich im Bauwesen in den letzten Jahren immer mehr in der Praxis etabliert. Echomessungen zur Geometriebestimmung sind Stand der Technik. In der Wissenschaft gibt es zahlreiche Ideen, die Messmethodik und die Auswertung weiter zu verbessern sowie den Einsatzbereich zu erweitern. Erste eingebettete Ultraschallsysteme zum Langzeitmonitoring sind installiert, Mehrkanalgeräte ermöglichen immer größere Aperturen und Eindringtiefen, verbesserte Abbildungsverfahren zeigen immer mehr Details. Zusätzlich lassen sich Verfahren aus der Geophysik adaptieren, die weiteren Fortschritt versprechen. Die Seismische Interferometrie dient klassisch dazu, Materialeigenschaften des Erduntergrundes mittels seismischer Wellen zu bestimmen. Derzeitige Anwendungsbereiche sind die Verbesserung seismischer Abbildungsverfahren, Interpolation seismischer Spuren (A-Scans), Bestimmung von Quellparametern oder die Eliminierung unerwünschter Signale in passiven und aktiven Experimenten, hauptsächlich durch Kreuzkorrelation und Bestimmung Greenscher Funktionen. Diese Techniken können auch auf Ultraschalldaten, die an Betonkonstruktionen erfasst wurden, angewendet werden. Moderne Abbildungsverfahren benötigen eine möglichst hohe A-Scan-Dichte und eine genaue Kenntnis des Quellsignals. Beides ist nicht unbedingt gegeben, z. B. wegen der physischen Größe der Sensoren und wechselnder Ankopplungsbedingungen. In simulierten und realen Experimenten wurden interferometrische Methoden zur Lösung dieser Aufgabenstellungen evaluiert. Es zeigt sich, dass fehlende A-Scans kinematisch korrekt interpoliert werden können, wenn ausreichend viele Sender- und Empfängerpositionen genutzt wurden. Amplituden und Signalform sind verändert, können aber durch adaptive Filterung angepasst werden. Die Quellsignalform kann mit hoher Genauigkeit rekonstruiert werden. Die Ergebnisse können potentiell zu einer Verbesserung der Abbildung des Inneren der untersuchten Objekte genutzt werden. T2 - DGZfP-Jahrestagung 2014 CY - Potsdam, Germany DA - 26.05.2014 KW - Zerstörungsfreie Prüfung KW - Geophysik PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-337967 UR - http://www.ndt.net/article/dgzfp2014/papers/di1c1.pdf SN - 978-3-940283-61-0 IS - DGZfP-BB 148 SP - Di.1.C.1, 1 EP - 8 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) CY - Berlin AN - OPUS4-33796 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zheng, H. A1 - Kappatos, V. A1 - Niederleithinger, Ernst A1 - Ertel, Jens-Peter A1 - Grohmann, Maria A1 - Selcuk, C. A1 - Gan, T.-H. T1 - Defect detection in concrete pile using impulse response measurements with sine sweep excitations N2 - For pile integrity inspection, a low cost and portable shaker was used to create the sine sweep signal for pile excitation. The impulse response function, calculated by the deconvolution of pile response from the sine sweep excitation, was proposed to identify the echoes in the piles due to the pile’s impedance changes. The proposed methodology has been evaluated and validated both numerically and experimentally. Based on the results from the simulations and experiments, it was found that the impulse response measurement with sine sweep excitation could be an effective tool to detect the echoes of the pile toe and the defects in the pile. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - Impulse response function KW - Sine sweep excitation KW - Pile integrity KW - Damage detection PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-347157 SN - 1435-4934 SP - 1 EP - 4 PB - Technische Universität Berlin / Bundesanstalt für Materialforschung und -prüfung AN - OPUS4-34715 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grohmann, Maria A1 - Müller, Sabine A1 - Niederleithinger, Ernst T1 - Reverse time migration: Introduction of a new imaging technique for ultrasonic measurements in civil engineering 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. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - Ultrasound KW - Imaging KW - Reverse time migration KW - Reflection seismics KW - Concrete PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-345406 SN - 1435-4934 SP - 1 EP - 10 PB - Technische Universität Berlin / Bundesanstalt für Materialforschung und -prüfung AN - OPUS4-34540 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Douma, J. A1 - Niederleithinger, Ernst A1 - Snieder, R. T1 - Improved focusing using deconvolution within a concrete block N2 - Time reversal techniques are used in ocean acoustics, medical imaging and non-destructive evaluation to backpropagate recorded signals to the source of origin. We demonstrate experimentally a technique which improves the temporal focus achieved at the source location. The experiment consists of propagating a signal from a transducer within a concrete block to a single receiver on the surface, and then applying time reversal or deconvolution to focus the energy back at the source location. The results show that we are able to generate a focus in time at the correct location. The proposed method is simple and proven to be robust. Additionally, its costs are negligible due to deconvolution being a preprocessing step to the recorded data. The technique can be applied for detailed investigation of the source mechanisms (e. g. cracks) but also for monitoring purposes. T2 - DGZfP-Jahrestagung 2014 CY - Potsdam, Germany DA - 26.05.2014 KW - Ultrasonics KW - Acoustic emission KW - Time reversal KW - Deconvolution PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-337953 UR - http://www.ndt.net/article/dgzfp2014/papers/di2c2.pdf SN - 978-3-940283-61-0 IS - DGZfP-BB 148 SP - Di.2.C.2, 1 EP - 8 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) CY - Berlin AN - OPUS4-33795 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -