TY - CONF A1 - Brandes, K. A1 - Kubowitz, P. A1 - Daum, Werner A1 - Hofmann, Detlef A1 - Basedau, Frank T1 - Lagrange Multiplikator-Test zur Detektierung von zunehmender Strukturschädigung N2 - Mit einem auf Lagrange-Multipiikator-Tests basierenden Monitoring von Brücken ist es gelungen, in Belastungsversuchen an einer Holzbrücke (7,25 m Spannweite), an der relativ kleine Schädigungen künstlich herbeigeführt worden waren, die Zuverlässigkeit dieser Art des Monitorings zu bestätigen. Ausgangspunkte waren Messung von Durchbiegungen sowie Krümmungen und die Zusammenführung der jeweiligen Regression mit Nebenbedingungen, die den mechanischen Bedingungen gehorchen, unter Einschluss von Lagrange-Multiplikatoren, die sich als brauchbare Testparameter erwiesen. T2 - 8. Symposium Experimentelle Untersuchungen von Baukonstruktionen CY - Dresden, Germany DA - 24.09.2015 KW - Schadensfrüherkennung KW - Strukturschädigung KW - Monitoring PY - 2015 SN - 1613-6934 N1 - Serientitel: Schriftenreihe Konstruktiver Ingenieurbau Dresden – Series title: Schriftenreihe Konstruktiver Ingenieurbau Dresden IS - 40 SP - 147 EP - 157 CY - Dresden AN - OPUS4-34793 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Köppe, Enrico A1 - Bartholmai, Matthias A1 - Daum, Werner A1 - Gong, Xin A1 - Hofmann, Detlef A1 - Basedau, Frank A1 - Schukar, Vivien A1 - Westphal, Anja A1 - Sahre, Mario A1 - Beck, Uwe T1 - New self diagnostic fiber optical sensor technique for structural health monitoring N2 - Fiber optic sensors have gained increasing importance in recent years and are well established in many areas of industrial applications. In this paper, we introduce a concept of a self-diagnostic fiber optic sensor. The presented sensor is to resolve the problems of embedded fiber optic sensors in complex structures and to enable the validation under operational conditions. For this purpose, different magnetostrictive coated fiber optic sensors were developed and various experiments were performed to verify their mode of operation and to determine the respective reproducibility. The measuring principle is illustrated by obtained experimental results, which showed a change in wavelength from 1 pm at a magnetic field strength change of 0.25 mT. In addition, the temperature characteristics of the implemented magnetostrictive sensor were analyzed and an experimental factor of 1.5 compared to a reference fiber optic sensor was determined. T2 - 32nd Danubia-Adria Symposium on advances in experimental mechanics CY - Starý Smokovec, Slovakia DA - 22.09.2015 PY - 2015 SN - 978-80-554-1094-4 SP - 1 EP - 2 CY - Zilina AN - OPUS4-35173 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schukar, Vivien A1 - Gong, Xin A1 - Hofmann, Detlef A1 - Basedau, Frank A1 - Köppe, Enrico A1 - Bartholmai, Matthias A1 - Westphal, Anja A1 - Sahre, Mario A1 - Beck, Uwe ED - Berghmans, F. ED - Mignani, A. G. T1 - Modelling and simulation of a fibre Bragg grating strain sensor based on a magnetostrictive actuator principle N2 - A new concept for the self-diagnosis of embedded fiber Bragg grating (FBG) strain sensors was developed, simulated and experimentally tested. This concept is based on a magnetostrictive metallic layer directly coated on the fibre cladding over the grating segment of the FBG sensor, so that an on-demand external magnetic field in a millitesla scale can produce a controllable artificial strain as an indication signal for the remote optical interrogator. The relationship between the pre-defined magnetic field and its induced Bragg wavelength shift characterizes this validation concept. Any deviation of the local bonding state of the interfaces from the initial or/and any change of shear strain transferring mechanism from composite matrix to the optical fibre core will result in alterations in this sensitive relationship, and thus triggers an immediate alert for a further inspection. The finite element method is used to simulate the strain of this configuration as result of different values of the magnetic field in order to optimize the geometrical sensor parameters. The simulations are verified by experiments results. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. T2 - Optical Sensing and Detection IV CY - Brüssel, Belgium DA - 03.04.2016 KW - Fiber Bragg gratings KW - Actuators KW - Modeling and simulation KW - Finite element methods PY - 2016 SN - 9781510601444 DO - https://doi.org/10.1117/12.2224728 SN - 0277-786X SN - 1996-756X VL - 9899 SP - 9899-39 PB - SPIE Digital Library AN - OPUS4-38634 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schukar, Vivien A1 - Köppe, Enrico A1 - Hofmann, Detlef A1 - Westphal, Anja A1 - Sahre, Mario A1 - Beck, Uwe A1 - Gong, Xing A1 - Bartholmai, Matthias ED - Aulova, Alexandra ED - Rogelj Ritonja, A. ED - Emri, I. T1 - A contribution to intelligent automatic validation of structure-integrated fibre optic strain sensors N2 - Sensors integrated into devices and structures provide essential data to control, optimize or manage machines and structural components. In the last years, processes, applications and machine parts became more and more intelligent. Consequently, the need for sensor validation increased significantly in order to rely on sensor data and measurement results. Structure-integrated fibre optic strain sensors, such as fiber Bragg gratings (FBG), are of special interest in the composite manufacturing industry. This type of sensor makes it possible to gain information and to collect measurement data about entire production processes and whole life-time cycles of composite-made machine parts and structures. However, validation concepts and approaches for this type of sensors are barely reported in literature. Furthermore, all the reported activities have the drawback that the sensor diagnosis strategy is implemented as limited mathematical models and/or complex time-consuming spectral analysis tools which are applied in data post-processing loops. However, to automate sensor validation and to apply real-time and in-field sensor fault detection, it is necessary to acquire measurement data and information about the measurement reliability at the same time. T2 - 33rd Danubia- Adria Symposium on Advances in Experimental Mechanics CY - Portorož, Slovenia DA - 20.09.2016 KW - Fiber bragg grating KW - Magnetic field KW - Magnetostrictive metal coating KW - Self-diagnostic fiber optical sensor PY - 2016 SN - 978-961-94081-0-0 SP - 180 EP - 181 CY - Ljubljana AN - OPUS4-37645 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brandes, K. A1 - Daum, Werner A1 - Hofmann, Detlef A1 - Basedau, Frank A1 - Kubowitz, P. T1 - Innovative structural damage detection of bridges by least squares adjustment with constraints N2 - Long-term monitoring of bridges requires the early detection of spreading damage because very often the damage is not really visible. For many decades engineers and scientists relayed on dynamic methods especially modal ones. However, after fundamental tests by the U.S. FHWA in 1993, it became evident that more successful methods should be developed, but no innovation really happened. A substantial innovative detection method started four years ago from Lagrange Multiplier Testing which eventually resulted in experimental verification based on measurement of deflection and curvature of the bridge beam and together the methodological combination of both. T2 - 32nd DANUBIA ADRIA SYMPOSIUM on Advances in Experimental Mechanics CY - Starý Smokovec – High Tatras, Slovakia DA - 22.09.2015 KW - Damage detection of bridges KW - Monitoring KW - Lagrange multiplier test PY - 2016 DO - https://doi.org/10.1016/j.matpr.2016.03.025 SN - 2214-7853 VL - 3 IS - 4 SP - 942 EP - 946 PB - Elsevier AN - OPUS4-36667 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Beck, Uwe A1 - Mitzkus, Anja A1 - Sahre, Mario A1 - Weise, Matthias A1 - Köppe, Enrico A1 - Bartholmai, Matthias A1 - Basedau, Frank A1 - Hofmann, Detlef A1 - Schukar, Vivien T1 - Faser-basierter magneto-optischer Schicht-Sensor zum Monitoring von Bauteilen N2 - In Glasfasern eingeschriebene Bragg-Gitter (FBG: fibre-based Bragg gratings) sind über die Verschiebung der Bragg-Wellenlänge in der Lage, Stauchungen und Dehnungen von Glasfasern hochgenau zu erfassen. In Kompositwerkstoffe eingebettete faseroptische Sensoren können Bauteile bezüglich ihrer mechanischen Integrität überwachen und früh-zeitig Informationen über Materialveränderungen gewinnen. Um die Zuverlässigkeit eines solchen Sensors zu gewährleisten, ist es wichtig, die korrekte Funktion des Sensors im Verbund mit der Werkstoff-Matrix on-line und in-situ sicherzu-stellen. Im Rahmen des DFG-Projekts FAMOS² (FAser-basierter Magneto-Optischer SchichtSensor) wurde ein selbstdiagnosefähiger Schichtsensor entwickelt, der mit Hilfe von magnetostriktiven Aktorschichten aus Nickel bzw. Eisen-Nickel validiert werden kann. Der FAMOS²-Schichtsensor wird durch ein PVD (physical vapour deposition)/ECD (electro-chemical deposition) Hybridschichtsystem realisiert, das auf dem Fasermantel im Bereich des FBG haftfest, homogen und langzeitfunktional abzuscheiden ist. Dabei wird in einem ersten Schritt ein etwa 100 Nanometer dünnes PVD-Schichtsystem aus Chrom und Kupfer als Haftvermittler auf der Glasfaser bzw. als leitfähige Startschicht für den nachfolgenden ECD-Prozess abgeschieden. Um eine rotationssymmetrische Schich-tabscheidung zu gewährleisten, erfolgt während der PVD-Beschichtung eine Rotation der Glasfasern. In einem zweiten Schritt wird dann unter Verwendung eines klassischen Watts-Elektrolyten in einer speziell entwickelten ebenfalls rotationssymmetrisch aufgebau-ten ECD-Durchströmungszelle dann die etwa 30 Mikrometer dicke, magnetostriktive Ak-torschicht auf dem PVD-Schichtsystem abgeschieden, im Vergleich sowohl reine Nickel-Schichten als auch Nickel-Eisen-Schichten. Ein äußeres Magnetfeld dehnt die magnetostriktive Aktorschicht und damit auch die Faser reversibel. Diese Dehnung führt zu einer Verschiebung der Bragg-Wellenlänge, welche direkt mit der Stärke eines zu messenden oder zu Validierungszwecken vorgegebenen Magnetfeldes korreliert. Die Anpassung der Beschichtungsverfahren an die Fasergeome-trie und die mechanischen Eigenschaften der Hybridschichten werden hinsichtlich der me-chanischen Integrität des faseroptischen Sensors diskutiert und der Nachweis der Selbst-diagnosefähigkeit erbracht. T2 - 13. ThGOT Thementage Grenz- und Oberflächentechnik und 11. Thüringer Biomaterial-Kolloquium CY - Zeulenroda, Germany DA - 13.03.2018 KW - Magneto-optischer Sensor KW - Faser-Bragg Gitter KW - Magnetostriktive Beschichtung KW - Selbstkalibrierung KW - Bauteilmonitoring PY - 2018 SN - 978-3-00-058187-8 SP - 1 EP - 5 CY - Jena AN - OPUS4-44599 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hofmann, Detlef T1 - Neue Aspekte zum Einsatz faseroptischer Sensoren in Ingenieurbauwerken N2 - Die Anwendung faseroptischer Sensoren, insbesondere von Faser-Bragg-Sensoren, an Holztragwerken wird vorgestellt und an Beispielen Möglichkeiten des Einsatzes verteilter faseroptischer Messverfahren gezeigt. T2 - Angewandte Forschung im Bauwesen - Anwenderkonferenz CY - Berlin, Germany DA - 22.09.2017 KW - Fasersensorik KW - Faser-Bragg-Gitter KW - Diskrete Messtechnik KW - Ortsaufgelöste Messung KW - Ortsverteilte Messtechnik PY - 2017 AN - OPUS4-42587 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hüsken, Götz A1 - Pirskawetz, Stephan A1 - Hofmann, Detlef A1 - Basedau, Frank A1 - Gründer, Klaus-Peter A1 - Kadoke, Daniel T1 - The load-bearing behaviour of a reinforced concrete beam investigated by optical measuring techniques N2 - Bending beams and slabs are typical examples for structural elements used for reinforced concrete structures such as bridge girders, T-beams and bridge decks. Their strength related failure modes at maximum loading can be divided into bending and shear failure. The failure of beams loaded in bending can occur with or without indication. Therefore, conventional design concepts aim on failure modes with sufficient indication (e.g. large deflections or cracks), as it occurs in the case of secondary flexural compression failure. These indicating factors can also be used for Structural Health Monitoring (SHM) of civil infrastructure systems (e.g. bridges) to identify structural changes. In this context, non-destructive testing (NDT) methods offer different techniques for measuring deflections or crack formation and opening. However, profound knowledge on the determining failure modes of bending beams and their detection by NDT methods is required for the reliable application of SHM. Different NDT methods have been used in this study for analysing the load-bearing behaviour of a reinforced concrete beam in bending. The different measuring techniques are briefly described and their applicability is discussed by means of experimental results. For this purpose, the load-bearing behaviour of a reinforced concrete beam having a span of 2.75 m was investigated in a four-point bending flexural test at laboratory scale. The focus is on the characterization of determining failure modes by optical NDT and the comparison with classical measuring techniques (e.g. deformation measurements by displacement transducers). The bending beam was equipped with two single-mode (SM) sensor fibres. One fibre served as Distributed Optical Fibre Sensor (DOFS), whereas the other fibre contained Fibre Bragg Grating (FBG) sensors. In addition, optical deformation measurements using Digital Image Correlation (DIC) and Stereophotogrammetry (SP) were conducted. KW - Concrete beam KW - Bending KW - Digital image correlation KW - Stereophotogrammetry KW - Distributed fibre optic sensor KW - Fibre bragg grating PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524762 DO - https://doi.org/10.1617/s11527-021-01699-6 VL - 54 IS - 3 SP - Article 102 PB - Springer AN - OPUS4-52476 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pirskawetz, Stephan A1 - Steinbock, O. A1 - Hille, Falk A1 - Schmidt, S. A1 - Hofmann, Detlef T1 - Erfahrungen aus dem Rückbau der Brücke am Altstädter Bahnhof in der Stadt Brandenburg - Teil 2: Schadensmonitoring bei zerstörenden Versuchen N2 - Im Dezember 2019 wurden bei einer turnusmäßigen Inspektion der B 1-Brücke am Altstädter Bahnhof in Brandenburg an der Havel massive und schnell voranschreitende Schäden festgestellt. Als Ursache für die Risse entlang der Längsträger wurde das Versagen eines signifikanten Anteils der Spanndrähte der konzentrierten Spannglieder vermutet. Die Brücke wurde umgehend für den Verkehr gesperrt und im Mai 2021 gesprengt. Im Vorfeld der Sprengung wurden durch das Bundesministerium für Digitales und Verkehr (BMDV) weiterführende Untersuchungen zum Schadensbild veranlasst, welche vom Landesbetrieb Straßenwesen Brandenburg koordiniert und in den Bauablauf integriert wurden. Das von der Hochschule für Technik und Wirtschaft (HTW) Dresden erstellte Versuchskonzept ist Bestandteil des vorangestellten ersten Teils des Beitrags [1]. Hier im zweiten Teil werden ausgewählte Ergebnisse der umfangreichen versuchsbegleitenden Mess- und Monitoringmaßnahmen beschrieben, welche in Kooperation der HTW Dresden, der Bilfinger Noell GmbH sowie der Bundesanstalt für Materialforschung und -prüfung (BAM) durchgeführt wurden. N2 - A routine inspection of the B1 bridge at the Altstädter Bahnhof in Brandenburg an der Havel in December 2019 revealed massive and rapidly progressing damage. The cause of the cracks along the longitudinal girders was suspected to be the failure of a significant portion of the prestressing wires of the concentrated tendons. The bridge was immediately closed to traffic and demolished in May 2021. Prior to the demolition, the Federal Ministry for Digital and Transport (BMDV) initiated further investigations into the damage pattern, which were coordinated and integrated into the deconstruction process by the Landesbetrieb Straßenwesen Brandenburg. The test concept was developed by the Hochschule für Technik und Wirtschaft Dresden (HTW) and is described in the previous article (Part 1). The article at present (Part 2) describes selected results of the extensive measurement and monitoring measures accompanying the tests. The Tests were carried out in cooperation with the HTW Dresden, Bilfinger Noell GmbH and the Bundesanstalt für Materialforschung und -prüfung (BAM). KW - Spannbetonbrücke KW - Spannstahlbruch KW - Schallemission KW - Fotogrammetrie KW - Faseroptik KW - Stochastische Subspacebasierte Schadensdetektion PY - 2022 DO - https://doi.org/10.1002/best.202200052 SN - 1437-1006 VL - 117 IS - 8 SP - 581 EP - 589 PB - Ernst & Sohn CY - Berlin AN - OPUS4-55513 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hofmann, Detlef T1 - Strukturüberwachung mit lokaler und verteilter faseroptischer Sensorik N2 - Der Vortrag gibt einen Überblick über die Einsatzmöglichkeiten faseroptischer Sensorik (FOS) als ZfP-Verfahren. Dabei werden an Beispielen lokale und verteilte faseroptische Verfahren zur Dehnungs-, Temperatur- und Risserfassung sowie zur akustischen Messung vorgestellt. Weiterhin werden Möglichkeiten zur Selbstdiagnose von FOS aufgezeigt. T2 - InnoTesting2020 "Innovative Ideen - neue Testmethoden" CY - Wildau, Germany DA - 27.02.2020 KW - Faseroptische Sensorik KW - Strukturüberwachung KW - Lichtwellenleiter KW - Zerstörungsfreie Prüfung KW - Selbstdiagnose PY - 2020 AN - OPUS4-51688 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hofmann, Detlef A1 - Basedau, Frank A1 - Heidenreich, F. A1 - Herten, M. T1 - Verwendung faseroptischer Messtechnik im Zuge wiederholter Eignungsprüfungen an Verpressankern N2 - Im Rahmen des Ausbaus des Dortmund-Ems-Kanals wurden an der Schleuse Gleesen Forschungsanker installiert, die Rückschlüsse auf das Tragverhalten in Folge des chemischen Angriffs kalklösender Kohlensäure geben sollen. Die Forschungsanker werden seit der Erstellung im Jahr 2017 mit verteilter faseroptischer Sensorik während der jährlichen Eignungsprüfungen untersucht. Die Ergebnisse der Jahre 2017 bis 2019 werden im Folgenden dargestellt. T2 - Messen in der Geotechnik 2020 CY - Braunschweig, Germany DA - 20.02.2020 KW - Faseroptische Sensorik KW - Rayleigh Rückstreuung KW - Verpressanker KW - Chemischer Angriff KW - Rissbildung PY - 2020 SN - 978-3-948141-02-8 DO - https://doi.org/10.24355/dbbs.084-201912181435-0 IS - 110 SP - 297 EP - 323 AN - OPUS4-51687 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Köppe, Enrico A1 - Hofmann, Detlef A1 - Daum, Werner T1 - Absolut messendes EFPI-Messsystem N2 - In diesem Paper wird ein absolut messendes faseroptisches Messsystem zur Bestimmung des Gap-Abstandes von niedrig reflektierenden losen und festen extrinsischer Fabry-Pérot Interferometer (EFPI) vorgestellt. Die häufigste Methode zur Bestimmung von Dehnungen oder Bewegungen durch EFPI-Sensoren ist eine kontinuierliche relative Ermittlung einer Veränderung mit einer nachträglichen Auswertung. Unterbrechungen in der Datenerfassung oder Fehler bei der Interferenzstreifen-Auswertung führen zu einer nicht abschätzbaren Messunsicherheit. Damit war es bis dato nicht möglich, eine absolute Veränderung von eingesetzten EFPI-Sensoren zu bestimmen. Mit dem an der BAM entwickelten Verfahren, ist dies jetzt möglich, die absolute Veränderung zu bestimmen. Dieses System namens 'EFPI-Scan' wird in dem Papier dargestellt werden. T2 - Sensoren und Messsysteme 2014 - 17. ITG/GMA-Fachtagung CY - Nürnberg, Germany DA - 03.06.2014 PY - 2014 SN - 978-3-8007-3622-5 SN - 0932-6022 N1 - Serientitel: ITG-Fachbericht – Series title: ITG-Fachbericht VL - 250 SP - P16.2, 1 EP - 3 PB - VDE Verlag GmbH AN - OPUS4-32644 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Schukar, Vivien A1 - Hofmann, Detlef T1 - Requirements to establish fibre-optic sensors for monitoring of structures N2 - Fibre-optic sensors need to be more established in the sensor market. Their advantages have unquestionably been verified by numerous demonstrations. However, there are some open questions leading now and then to restraints in the user's community. The paper dicusses examples where fibre-optic sensors provide outstanding knowledge about the structure's behaviour, but application is often challenging. Requirements are listed and open questions to be solved are discussed. Short outlook to standards useful for better design, characterization and application is given. Standards are the basis for establiching SHM systems, especially for safety-critical structural diagnostics. T2 - EWSHM 2014 - 7th European workshop on structural health monitoring CY - Nantes, France DA - 08.07.2014 KW - Monitoring KW - Fibre-optic sensor KW - Reliability KW - Application PY - 2014 SP - 2330 EP - 2337 AN - OPUS4-32662 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Hofmann, Detlef A1 - Döring, H. A1 - Jentsch, H. A1 - Senze, A. A1 - Kowalle, G. ED - Shi, B. T1 - Detection of a slipping soil area in an open coal pit by embedded fibre-optic sensing rods N2 - Movements in geological areas are mostly concentrated on faults or slipping zones. Detection of movements reaching critical values is of crucial importance to avoid losses and harms. The paper presents a new technology of detecting deformations and movements in soil or rock massifs. The core part of the sensing system is a tiny rod with embedded optical sensor fibres. This deformation measurement system was developed and the sensing rod can be installed in a borehole and enables the detection of beginning soil movements. The amount of deformation in soil or rock formations can then be estimated. The sensing rod has an outer diameter of 3 mm to 6 mm and contains several optical fibres. One fibre is used as online measurement system and provides integral strain information along the whole length of the rod. In case of a safety-relevant deformation (warning signal), the second sensing system based on fibre Bragg grating sensors positioned close to the expected shear zone will be activated and records then resulting deformations in detail. T2 - OSMG-2014 - 5th International forum on opto-electronic sensor-based monitoring in geo-engineering CY - Nanjing, China DA - 12.10.2014 KW - Fibre-optic strain sensor KW - Structural health monitoring KW - Soil stability monitoring KW - Early warning PY - 2014 SP - 1 EP - 7 AN - OPUS4-32664 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Brandes, K. A1 - Daum, Werner A1 - Hofmann, Detlef A1 - Kubowitz, P. T1 - Lagrange multiplier test for structural damage of bridges N2 - Detecting spreading damage in bridges is a demanding task for engineers today when the ageing infrastracture of industriaiized countries is degradating more and more. To successfully deal with tbis problem, a really advanced method has been elaborated basing on Langrange Multiplier (LM) tests and following the principle of simplicity by Hilbert and extending comments by Helmholtz refering to a combination of measurement and analytical treatment. Finally, an easy mathematical fonnation has been created. T2 - 31st Danubia-Adria Symposium on advances in experimental mechanics CY - Kempten, Germany DA - 24.09.2014 PY - 2014 SN - 978-3-00-046740-0 SP - 213 EP - 214 AN - OPUS4-31725 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Köppe, Enrico A1 - Hofmann, Detlef A1 - Daum, Werner T1 - Absolute measuring EFPI-measurement system N2 - The absolute detection of a gap distance of loose and ftxed extrinsic Fabry-Perot interferometer (EFPI) sensors with conventional measurement Systems is not possible. Due to this EFPI-sensors were deemed to be unfit for distance determination in comparision with FBG sensors. With the conventional measurement method a continous measurement of the EFPIsensors was necessary. Otherwise data about the distance change was lost. Additional it is necessary to detect the tumaround points in the interference signal with 100%. This made it worse for the analysis and the use of the sensor. At BAM Federal Institute for Materials Research and Testing a measurement System called “EFPI-Scan” is developed which can measure the absolute gap distance of four connected EFPI-sensors synchronous. Every measurement channel is temperature independetn and long term stable. Test measurements showed a deviation of maximum ±1 gm per hour. Furthermore it is possible to measure with different measurement modes (abolute, relative and a combination of both). Special emphasis should be placed to the absolute measurement accuracy of ± 5 pm at a gap distance determination ftom 40 up to 4000 pm. T2 - 31st Danubia-Adria Symposium on advances in experimental mechanics CY - Kempten, Germany DA - 24.09.2014 PY - 2014 SN - 978-3-00-046740-0 SP - 120 EP - 121 AN - OPUS4-31729 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jentsch, H. A1 - Schwartz, A. A1 - Basedau, Frank A1 - Bazrafshan, K. A1 - Döring, H. A1 - Großwig, S. A1 - Hofmann, Detlef A1 - Kowalle, G. A1 - Kusche, Nadine A1 - Lorenz, R. A1 - Pfeiffer, T. A1 - Sadaghiani, M.R.S. A1 - Scholz, E. A1 - Senze, A. A1 - Tkachenko, Viktoriya A1 - Witt, K. J. ED - Xu, Y. L. ED - Zhu, S. ED - Xia, Y. ED - Ni, Y.Q. ED - Law, S.S. ED - Yin, J. H. ED - Su, Z.Q. T1 - Detection of slipping soil areas with embedded tiny vertical sensing rods N2 - Critical soil zones where large areas along a shear joint might begin to slip should be recognized. In order to avoid damage, monitoring of such unstable zones is necessary. First, soil movements must be detected as early as possible, second, the amount of deformation should be estimated. Because geodetical methods do not provide information about deformation in the underground in different depths, the only way to come to information from possible shear zones is the installation of deformation measurement systems. A special installation method was developed to bring a long-gauge length measurement system into a borehole and transfer data of soil deformations into an installed sensing rod. The mostly vertically installed sensing rod has an outer diameter of 3 mm to 6 mm and contains several optical fibres. One fibre provides integral strain information along the whole length of the rod. To get this information, the phase difference between the fibre input and output is measured and the change of the total length of the fibre can be derived. This easy and cheap online sensing system delivers an early warning of soil deformations respectively possible slip as well as landslides. In case of warning, the second sensing system based on Fibre Bragg Grating sensors located close to the expected shear zone purposefully. It records resulting deformations in detail. In this study, three main objectives were achieved: a) development of tiny pultruded sensing rods with integrated optical sensor fibres, b) installation technology which enables the integration of the sensing rod during drilling and pile driving, and c) development of a stiff but elastic racking material to fix the rod in the soil and to transfer soil deformation into the stiffer sensing rod. These three aspects including the fibre optical measurement systems are described; results from Press Deformation Test (PDT) are presented. Test results of the fibre optical online system are compared and evaluated with the results of conventional inclinometer measurements as well as numerical modelling. An outlook for further possibilities of usage of this monitoring system is given. T2 - SHMII-6 - 6th International conference on structural health monitoring of intelligent infrastructure CY - Hong Kong, China DA - 09.12.2013 KW - Structural health monitoring KW - Soil stability monitoring KW - Optical fibre strain-sensor KW - Geotechnical soil stability KW - Soil deformation modelling PY - 2013 SN - 978-962-367-768-4 SP - 1 EP - 9 AN - OPUS4-29915 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Habel, Wolfgang A1 - Schukar, Vivien A1 - Tkachenko, Viktoriya A1 - Hofmann, Detlef A1 - Basedau, Frank ED - Xu, Y. L. ED - Zhu, S. ED - Xia, Y. ED - Ni, Y.Q. ED - Law, S.S. ED - Yin, J. H. ED - Su, Z.Q. T1 - Values gained from composite-embedded sensor fibres - trustworthy results or vague estimations; possibilities and limitations of getting reliable measurement results T2 - SHMII-6 - 6th International conference on structural health monitoring of intelligent infrastructure CY - Hong Kong, China DA - 2013-12-09 KW - Composite materials KW - Embedded sensors KW - Monitoring KW - Early damage detection KW - Validation KW - Reliability KW - Maintenance KW - Repair PY - 2013 SN - 978-962-367-768-4 SP - 1 EP - 11(?) AN - OPUS4-29912 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hamann, M. A1 - Kubowitz, P. A1 - Hofmann, Detlef ED - Xu, Y. L. ED - Zhu, S. ED - Xia, Y. ED - Ni, Y.Q. ED - Law, S.S. ED - Yin, J. H. ED - Su, Z.Q. T1 - Scale of intelligence in hybrid bridge structures - new aspects of monitoring by using fibre-optic sensors in timber elements N2 - In structural engineering timber is appreciated due to its low weight, its high aesthetic quality and because it is a renewable resource. The market share of timber structures and wood based hybrid structures will clearly increase over the next few years due to greater environmental awareness and a higher demand for sustainability. However, building with timber is marked by characteristics which lead to significant disadvantages in comparison wifh technical materials. For example, in outdoor areas Chemical and structural approaches offen lead to unsatisfactory and expensive Solutions with respect to durability. An idea is to make natural lumber a high-performance material which can be designed to meet the engineers’ demands conceming strength, stiffness, durability, shape, safety etc. These changes can affect the material itself, new technologies or a new approach to monitoring. Especially hybrids made of common timber products and technical textiles or enhanced timber products are high-capacitive and reach high bearing strengths with low material input and good durability. These hybrids are particularly qualified to use the advantages of wood and minimize the disadvantages. They can be used in different ways for load bearing structures, i.e. bridges. New construction types need monitoring to observe the stress and strains for which they were designed, and the structures’ behaviour as well as to guarantee required safety levels. The aim of successful usage of fibre optic measurement technology in timber elements was the development of a technology for measuring the lengthening in timber elements and wood based hybrid elements by using fibre optic sensors. The scientific and technical challenge was to develop an applicationtechnology for optical glass fibres in timber and densified veneer wood. In laboratory tests as well as with the erection of a footbridge and during in-situ tests it could be shown that the structurally integrated fibre optic sensor technology used is suitable for short and long term measurement. The developed embedment technology tums out to be practical and fit for good transfer of strain-values from timber to the modified sensor fibres. T2 - SHMII-6 - 6th International conference on structural health monitoring of intelligent infrastructure CY - Hong Kong, China DA - 09.12.2013 KW - Structural health monitoring KW - Structural engineering KW - Timber KW - Composites KW - Hybrid construction types KW - Fibre optic sensor technology KW - Sensor fibres PY - 2013 SN - 978-962-367-768-4 SP - 1 EP - 10 AN - OPUS4-29913 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mitzkus, Anja A1 - Sahre, Mario A1 - Reinstädt, Philipp A1 - Griepentrog, Michael A1 - Beck, Uwe A1 - Köppe, Enrico A1 - Bartholmai, Matthias A1 - Basedau, Frank A1 - Hofmann, Detlef A1 - Gong, Xin A1 - Schukar, Vivien T1 - Altbekannter Watts-Elektrolyt, junge Hightech-Anwendung, Nickel- und Nickel-Eisen-Schichten als magnetostriktive Aktorschicht auf faseroptischen Sensoren N2 - Durch faseroptische Sensoren können Bauteile im Einsatz kontinuierlich überwacht und frühzeitig Informationen über Materialveränderungen gewonnen werden. Mittels einer magnetostriktiven Aktorschicht, welche den Sensor umhüllt, kann nun auch die korrekte Sensorfunktion jederzeit kontrolliert werden. Als Aktorschicht eignet sich galvanisch abgeschiedenes reines Nickel oder Nickel-Eisen in der Zusammensetzung 50:50. Um diese haftfest mit dem Sensor zu verbinden wurde ein ECD/PVD-Kombinationsschichtsystem entwickelt. Die mechanischen Eigenschaften der ECD-Schicht können sowohl mit einer auf die Fasergeometrie angepassten instrumentierten Eindringprüfung als auch einem 2-Punkt-Biegeversuch bestimmt werden. KW - Faseroptik-Sensoren KW - ECD-Aktorschicht KW - PVD-Haftfestigkeit KW - Nickel-/Nickel-Eisen- Magnetostriktion PY - 2016 SN - 2195-5891 SN - 2195-5905 VL - 12 SP - 1 EP - 4 AN - OPUS4-39129 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Köppe, Enrico A1 - Bartholmai, Matthias A1 - Daum, Werner A1 - Gong, Xing A1 - Hofmann, Detlef A1 - Basedau, Frank A1 - Schukar, Vivien A1 - Westphal, Anja A1 - Sahre, Mario A1 - Beck, Uwe T1 - New self - diagnostic fiber optical sensor technique for structural health monitoring N2 - Fiber optic sensors have gained increasing importance in recent years and are well established in many areas of industrial applications. In this paper, we introduce a concept of a self-diagnostic fiber optic sensor. The presented sensor is to resolve the problems of embedded fiber optic sensors in complex structures and to enable the validation under operational conditions. For this purpose, different magnetostrictive coated fiber optic sensors were developed and various experiments were performed to verify their mode of Operation and to determine the respective reproducibility. The measuring principle is illustrated by obtained experimental results, which showed a change in wavelength from 1 pm at a magnetic field strength change of 0.25 mT. In addition, the temperature characteristics of the implemented magnetostrictive sensor were analyzed and an experimental factor of 1.5 compared to a reference fiber optic sensor was determined. T2 - 32nd DANUBIA ADRIA SYMPOSIUM on Advances in Experimental Mechanics CY - Starý Smokovec, Slovakia DA - 22.09.2015 KW - Self-diagnostic fiber optical sensor KW - Magnetostrictive metal coating KW - Magnetic field KW - Fiber bragg grating PY - 2016 DO - https://doi.org/10.1016/j.matpr.2016.03.038 SN - 2214-7853 VL - 3 IS - 4 SP - 1009 EP - 1013 AN - OPUS4-37131 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hofmann, Detlef A1 - Krebber, Katerina ED - Lutz, B. ED - Möller, G. ED - Rücker, Werner ED - Schiefelbein, N. T1 - Herausforderungen bei der Nutzung faseroptischer Sensoren für spezielle geotechnische Fragestellungen N2 - Geotechnische Tätigkeitsfelder und Forschungsaufgaben haben sich immer an den modernen Herausforderungen orientiert und umfassen z. B. die Beschreibung und Quantifizierung der Interaktion zwischen Baugrund und Bauwerk, die Untersuchung des Untergrunds besonders hinsichtlich der technischen und sozialen Infrastrukturen und die Beeinflussung der Umwelt. Fragen der zivilen Sicherheit stellen steigende Anforderungen an die Tragfähigkeit und Dauerhaftigkeit von Bauwerken. Zur Lösung dieser Aufgaben entstehen vielfältige interessante Methoden und Verfahren zur Strukturbewertung, die neben der Erfassung des allgemeinen Zustands auch neue Erkenntnisse zum Bauwerksverhalten im Hinblick auf moderne Bautechnologien und auf die Lebensdauer von Bauwerken liefern. Die systematische, zuverlässige und langzeitstabile Erfassung von geotechnischen Messgrößen und Parametern bei der Strukturbewertung sowie die Beobachtung und Bewertung der geologischen Gegebenheiten mit technischen Hilfsmitteln ist dafür unerlässlich und lässt sich mit den Begriffen Zustandsanalyse und Bauwerksmonitoring zusammenfassen. Das Ziel dabei ist, mögliche Schädigungsmechanismen frühzeitig zu erkennen, um rechtzeitig Gegenmaßnahmen ergreifen zu können. T2 - Messen im Bauwesen 2014 - Neue Messtechniken und Anwendungsfälle CY - Berlin, Germany DA - 04.03.2014 KW - Faseroptische Sensorik KW - Optische Messverfahren KW - Fabry-Perot-Interferometer KW - Faser-Bragg-Gitter KW - Applikation KW - Anwendungen KW - Geomatten KW - Raman KW - Brillouin PY - 2014 SN - 978-3-9815944-7-8 SP - 7 EP - 26 AN - OPUS4-33812 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hofmann, Detlef T1 - Zuverlässigkeit von optischen Fasern zur Dehnungsmessung in Offshore-Anwendungen T2 - 4. Zukunftskonferenz: Wind & Maritim CY - Rostock, Germany DA - 2015-05-06 PY - 2015 AN - OPUS4-33742 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hofmann, Detlef T1 - Embedding of Fibre-Optic Sensors in High-Performance Timber Structures T2 - 31th Danubia-Adria Symposium CY - Kempten, Germany DA - 2015-09-24 PY - 2015 AN - OPUS4-33743 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -