TY - JOUR A1 - Farhan, Muhammad A1 - Schneider, Ronald A1 - Thöns, Sebastian T1 - Predictive information and maintenance optimization based on decision theory: a case study considering a welded joint in an offshore wind turbine support structure N2 - Predictive information and maintenance optimization for deteriorating structures is concerned with scheduling (a) the collection of information by inspection and monitoring and (b) maintenance actions such as repair, replacement, and retrofitting based on updated predictions of the future condition of the structural system. In this article, we consider the problem of jointly identifying—at the beginning of the service life—the optimal inspection time and repair strategy for a generic welded joint in a generic offshore wind turbine structure subject to fatigue. The optimization is performed based on different types of decision analyses including value of information analyses to quantify the expected service life cost encompassing inspection, repair, and fatigue damage for all relevant combinations of inspection time, repair method, and repair time. Based on the analysis of the expected service life cost, the optimal inspection time, repair method, and repair time are identified. Possible repair methods for a welded joint in an offshore environment include welding and grinding, for which detailed models are formulated and utilized to update the joint’s fatigue performance. The decision analyses reveal that an inspection should be scheduled approximately at mid-service life of the welded joint. A repair should be performed in the same year after an indication and measurement of a fatigue crack given an optimal inspection scheduling. This article concludes with a discussion on the results obtained from the decision and value of information analyses. KW - Integrity management KW - Value of information KW - Decision theory KW - Structural reliability KW - Fracture mechanics KW - Fatigue KW - Predictive maintenance KW - Wind turbine support structure PY - 2021 DO - https://doi.org/10.1177/1475921720981833 SN - 1475-9217 SN - 1741-3168 PB - Sage Publications CY - London AN - OPUS4-52771 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thöns, Sebastian A1 - Faber, M. H. A1 - Rücker, Werner T1 - Optimierung des Managements der Tragwerksintegrität für Offshore-Windenergieanlagen N2 - Dieser Artikel enthält aktuelle Forschungsergebnisse im Bereich des überwachungsgestützten Managements der Tragwerksintegrität. Das Management der Tragwerksintegrität hat zum Ziel, die Funktionalität eines Tragwerks während des gesamten Lebenszyklus durch Einhaltung der Zielzuverlässigkeiten sicherzustellen. Ausgehend von Forschungsergebnissen über die Charakteristik von Überwachungsverfahren und -daten im Rahmen von Zuverlässigkeitsanalysen, wird ein Ansatz vorgestellt, wie die erwarteten Kosten für das Management der Tragwerksintegrität durch Überwachungsverfahren optimiert werden können. Dazu wird eine Kosten-Nutzen-Analyse für den Lebenszyklus einer Gründungstruktur von Offshore-Windenergieanlagen durchgeführt. Im Rahmen der Bayes'schen Entscheidungstheorie werden durch eine Prä-posteriori-Entscheidungsanalyse die optimalen Entscheidungsparameter für den Entwurf eines Überwachungssystems bestimmt. Als Fallstudie wird ein Überwachungssystem für die Gründungsstruktur eines Multibrid-M5000-Prototyps konzipiert und die mögliche Reduktion der Risiken und erwarteten Betriebskosten quantifiziert. N2 - This paper contains recent research results in the field of monitoring supported structural integrity management. The structural integrity management aims at ensuring the functioning of a structure throughout the life cycle by compliance with the target reliabilities. Building upon research results concerning the characteristics of monitoring techniques and data within the framework of reliability analyses, an approach is introduced for the optimisation of the expected structural integrity management costs by monitoring information. For this aim, a life cycle cost benefit analysis for offshore wind turbine support structures is formulated. The optimal monitoring decision parameters are then assessed utilizing the Bayesian pre-posterior decision theory. As a case study a monitoring system for a Multibrid M5000 offshore wind turbine prototype support structure is designed and possible reductions of the risks and expected costs are quantified. KW - Management der Tragwerksintegrität KW - Messunsicherheit KW - Tragwerkszuverlässigkeit KW - Bayes'sche Aktualisierung KW - Kosten-Nutzen-Analyse KW - Lebenszyklus KW - Structural integrity management KW - Measurement uncertainty KW - Structural reliability KW - Bayesian updating KW - Cost-benefit analysis KW - Life cycle KW - Bauwerkserhaltung/Sanierung - Maintenance and Repair KW - Meerestechnik - Offshore engineering KW - Stahlbau - Steel construction PY - 2012 DO - https://doi.org/10.1002/bate.201200021 SN - 0932-8351 SN - 1437-0999 SN - 0005-6820 SN - 0341-1052 SN - 0932-6359 VL - 89 IS - 8 SP - 525 EP - 532 PB - Ernst & Sohn CY - Berlin AN - OPUS4-26313 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian A1 - Faber, M.H. A1 - Rücker, Werner ED - Faber, M.H. ED - Köhler, J. ED - Nishijima, K. T1 - On the utilization of monitoring data in an ultimate limit state reliability analysis N2 - This paper describes a structural reliability analysis utilizing monitoring data in the ultimate limit state with consideration of the uncertainties of the monitoring procedure. For this purpose the uncertainties of the monitoring data are modeled utilizing a new framework for the determination of measurement uncertainties. The approach is based on a process equation and Statistical models of observations for the derivation of a posterior measurement uncertainty by Bayesian updating. This facilitates the quantification of a measurement uncertainty using all available data of the measurement process. For the reliability analysis in the ultimate limit state, monitoring data can be utilized as a loading model Information and as proof loading, i.e. resistance model Information. Both approaches are discussed with generic examples and it is shown that the modeling of monitoring data in a reliability analysis can result in a reduction of uncertainties and as a consequence in the reduction of the probability of failure. Furthermore, the proof loading concept is developed further to account for the uncertain characteristic of proof loading due to the measurement uncertainties which is consistent with the framework for the determination of measurement uncertainties. These approaches and findings can be utilized for the assessment of structures for life cycle extension and the design of monitoring Systems. T2 - ICASP 11 - 11th International conference on applications of statistics and probability in civil engineering CY - Zurich, Switzerland DA - 01.08.2011 PY - 2011 SN - 978-0-415-66986-3 SP - 1762 EP - 1769 PB - Taylor & Francis CY - London AN - OPUS4-24292 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rohrmann, Rolf A1 - Thöns, Sebastian A1 - Rücker, Werner A1 - Bicker, S. A1 - Said, Samir A1 - Schmid, Wolfgang T1 - Structural investigations and monitoring results on a prototype of offshore wind turbines of multibrid M5000 series N2 - The concept and technical details of the implementation of the developed integrated monitoring system within the IMO-WIND project are presented. The tasks of the components of the system and its requirements are described. Selected results from the continuous monitoring during operation of the plant M5000_2 regarding the task design verification and dynamic structural analysis are given. T2 - DEWEK 2010 - 10th German wind energy conference CY - Bremen, Germany DA - 2010-11-17 KW - Integrated monitoring system KW - Offshore wind turbines KW - Design verification KW - Structural assessment KW - Limit values KW - Load transfer KW - Data management KW - Dynamic analysis KW - Rotor blades KW - Embedded sensors PY - 2011 IS - S03 SP - 1 EP - 5 PB - DEWI GmbH AN - OPUS4-23712 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - SHM Strategies, application and measurements on tripod offshore wind energy converters within the German Offshore Park Alpha Ventus T2 - The Fifth International Conference on Structural Engineering, Mechanics and Computation (SEMC 2013) CY - Cape Town, South Africa DA - 2013-09-01 PY - 2013 AN - OPUS4-29183 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Faber, M.H. A1 - Thöns, Sebastian A1 - Narasimhan, H. A1 - Schubert, M. T1 - Risikobasierter Ansatz zur Bewertung der Robustheit von Bauwerken N2 - Ziel des vorliegenden Beitrages ist es, einen Überblick über die aktuellen Entwicklungen im Bereich der Bewertung und der Quantifizierung der Robustheit von Bauwerken zu geben. In diesem Sinne ist eine Zusammenstellung von Ansätzen und Ergebnissen aktueller Veröffentlichungen enthalten. Ein umfassender entscheidungstheoretischer Ansatz für die Berechnung und das Management der Robustheit wird vorgestellt. Dieser beinhaltet die Definition der Robustheit als eine Qualität eines Systems, welches das Bauwerk beinhaltet, d. h. eine Qualität, die auf der Grundlage einer Risikoanalyse bewertet werden kann. Um eine umfassende Risikoanalyse zu ermöglichen, wird ein szenarienbasierter Modellansatz eingeführt, welcher zwei Arten von Konsequenzen im System unterscheidet: direkte Konsequenzen (in Verbindung mit Schäden einzelner Komponenten des Systems) und indirekte Konsequenzen (in Verbindung mit einem Versagen des Systems). Die Definition des Systems spielt deshalb für die Risikoanalyse eine wichtige Rolle, und es wird diskutiert, wie die Robustheit für verschiedene Definitionen zu unterschiedlichen Ergebnissen und Erkenntnissen im Sinne des Managements der Integrität des Bauwerks im gesamten Lebenszyklus unter Berücksichtigung seiner Funktionalität führt. Weiterhin werden wichtige Aspekte der Standardisierung der Robustheitsanalyse, wie auch Anforderungen an die Robustheit, diskutiert und Vorschläge zum Umgang mit diesen Aspekten unterbreitet. Auf der Grundlage der vorgestellten Ansätze zur Berechnung der Robustheit eines Bauwerks wird beschrieben, wie Entscheidungen in Bezug auf den Entwurf, die Zustandsbewertung, auf Inspektionen und Wartung sowie in Bezug auf die Überwachung von Bauwerken, in Hinblick auf das Management der Risiken in allen Phasen des Lebenszyklus, optimiert werden können. KW - Qualität KW - Risikoanalyse KW - Modellansatz KW - Konsequenz KW - Direkt KW - Indirekt KW - Versagen KW - Schaden KW - Lebenszyklus KW - Hängebrücke KW - Quality KW - Risk assessment KW - Model approach KW - Consequence KW - Direct KW - Indirect KW - Failure KW - Damage KW - Life-cycle KW - Suspension bridge KW - Entwurf und Konstruktion KW - Berechnungs- und Bemessungsverfahren KW - Bestandssicherung und Erhaltung PY - 2010 DO - https://doi.org/10.1002/stab.201001354 SN - 0038-9145 SN - 1437-1049 SN - 0932-6375 VL - 79 IS - 8 SP - 547 EP - 555 PB - Ernst CY - Berlin AN - OPUS4-21862 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rohrmann, Rolf A1 - Thöns, Sebastian A1 - Rücker, Werner T1 - Integrated monitoring of offshore wind turbines - requirements, concepts and experiences N2 - Wind turbines on offshore sites (OWECs) are subjected to combined loads from wind and waves. These dynamic loads, with a frequency content within the range of the natural frequencies of the structures, cause fatigue-effective stresses in the substructures of wind turbines. Therefore, the examination of natural frequencies is an important part within the design process of wind turbines. The quality of the numerical models for such calculations is of great importance, since the certification guidelines permit only small uncertainties in modal analysis results. The accuracy of the parameters of the numerical model can only be achieved through a comparison of simulation results with corresponding test results. Therefore, it is necessary to measure the dynamic behaviour of all components of the wind turbines simultaneously. This is true not only for the design verification, but also for monitoring the OWECs in operation. The potential of integrated systems for monitoring-based maintenance optimisation should thus be used. KW - Offshore wind turbines KW - Integrated monitoring system KW - Structural assessment KW - Damage indicators KW - Dynamic loads KW - Data management PY - 2010 DO - https://doi.org/10.1080/15732470903068706 SN - 1573-2479 SN - 1744-8980 VL - 6 IS - 5 SP - 575 EP - 591 PB - Taylor & Francis CY - London AN - OPUS4-21452 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Assessing the Value of Structural Health Monitoring T2 - ICOSSAR 2013, 11th International Conference on Structural Safety & Reliability CY - New York, NY, USA DA - 2013-06-16 PY - 2013 AN - OPUS4-28820 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thöns, Sebastian A1 - Stewart, M. G. T1 - On the cost-efficiency, significance and effectiveness of terrorism risk reduction strategies for buildings N2 - We analyse the performance of risk reduction strategies for Terrorist attacks with Improvised Explosive Devices (IEDs) for large governmental building structures in terms of cost-efficiency, significance and effectiveness Accounting for life safety in conjunction with societal preferences and capabilities. The approach builds upon an extended Bayesian pre-posterior decision analysis and the principles of the marginal lifesaving costs based on the Life Quality Index (LQI). The decision scenario is formulated for a decision maker responsible for the safety of governmental or large commercial buildings and consequently the direct risks, the indirect risks due to fatalities and economical importance of the building beside the expected cost for the individual risk reduction strategies are modelled, aggregated and optimised. The considered risk reduction strategies encompass an explicit consideration and distinction of information and actions such as (i) threat surveillance may trigger the temporary evacuation of the building, (ii) the implementation of protection provisions provided by codes and guidelines, (iii) a detailed progressive collapse assessment and specific protection measures and (iv) the combination of protection and surveillance. All considered strategies are found to contribute to risk reduction and can be costefficient, especially for higher threat probabilities. The risk reduction strategies comply with societal macroeconomic and demographical characteristics and societal preferences according to the LQI. The progressive collapse assessment with targeted protection measures is found to be the most cost-efficient, significant and effective counter-terrorism strategy. This finding points to the necessity for a comprehensive utilisation of scientific methods and sophisticated engineering for progressive collapse assessment to determine targeted protection measures. KW - Significance and effectiveness KW - Risk mitigation strategies KW - Terrorist attacks KW - Value of information KW - Bayesian probability KW - Reliability KW - Risk and decision analysis KW - Decision optimality PY - 2020 DO - https://doi.org/10.1016/j.strusafe.2020.101957 VL - 85 SP - 10195 PB - Elsevier Ltd. AN - OPUS4-50794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thöns, Sebastian A1 - Rohrmann, Rolf A1 - Rücker, Werner A1 - Faber, M.H. T1 - Bewertung der Ermüdungsfestigkeit von Baustrukturen in Offshore-Windenergie-Anlagen N2 - Das Bauwerk einer Windenergieanlage dient der Sicherstellung der Energieproduktion. Eine entsprechende Zuverlässigkeit der Struktur und deren permanente Bewertung und Unterhaltung ist dazu notwendig. In diesem Beitrag werden Möglichkeiten der Bewertung des für die Struktur wichtigen Schädigungsmechanismus Ermüdung sowie dessen Überwachung in Zusammenhang mit Schädigungsindikatoren aufgezeigt. Dabei wird auf strukturmechanische, werkstoffmechanische und probabilistische Modelle sowie auf Messdaten eines Prototyps einer OWEA zurückgegriffen. Ausgehend von der gesamtdynamischen Berechnung wird die Zuverlässigkeit gemäß der Auslegung für den Schädigungsmechanismus Ermüdung durch ein Wöhlerlinienmodell berechnet. Damit werden ermüdungssensible Komponenten der Struktur identifiziert. Schädigungsindikatoren zur Überwachung der Ermüdungsfestigkeit werden auf Grundlage schädigungs-äquivalenter Dehnungen vorgestellt. Fatigue assessment of support structures for offshore wind energy converters. The structure of wind energy converters secures a reliable energy production. Hence an adequate reliability of the structure and additionally permanent assessment and maintenance is required. Within this paper methods for the assessment of the important damage mechanism fatigue in combination with monitoring of the fatigue reliability utilizing damage indicators are proposed. These methods comprise structural system, material degradation and probabilistic models as well as monitoring data of an offshore wind energy converter prototype. The structural reliability of the structure as designed is calculated based on an overall dynamic analysis using a SN-approach. Herewith fatigue sensitive components are identified. Damage indicators for monitoring the fatigue reliability based on damage equivalent strains are presented. KW - Bewertung KW - Offshore-Windenergie KW - Ermüdung KW - Strukturspannungskonzept KW - Zuverlässigkeit KW - Schadensindikatoren KW - Integrated Monitoring System KW - Damage Identification KW - Load Monitoring KW - Wind turbines PY - 2008 DO - https://doi.org/10.1002/stab.200810076 SN - 0038-9145 SN - 1437-1049 SN - 0932-6375 VL - 77 IS - 9 SP - 630 EP - 638 PB - Ernst CY - Berlin AN - OPUS4-17977 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Rohrmann, Rolf A1 - Rücker, Werner A1 - Thöns, Sebastian A1 - Said, Samir A1 - Schmid, Wolfgang T1 - Ergebnisse der Dauerüberwachung an einem Prototypen von Offshore-Windenergieanlagen T2 - 3. VDI-Fachtagung - Baudynamik CY - Kassel, Deutschland DA - 2009-05-14 KW - Integrated Monitoring System KW - Offshore wind turbines KW - Assessment KW - Damage identification KW - Load monitoring PY - 2009 SN - 978-3-18-092063-4 SN - 0083-5560 VL - 2063 SP - 455 EP - 466 PB - VDI-Verl. CY - Düsseldorf AN - OPUS4-19795 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rohrmann, Rolf A1 - Thöns, Sebastian T1 - Design-Verifikation von Offshore-Windenergieanlagen mit Hilfe integraler Überwachungssysteme T2 - Finales Statusseminar zum Forschungsvorhaben IMO-WIND CY - Berlin, Germany DA - 2009-10-01 PY - 2009 AN - OPUS4-20077 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Inspection and monitoring supported structural integrity management T2 - BAM-DTU Workshop on Design and maintenance of support structures for Offshore Wind Converters CY - Copenhagen, Denmark DA - 2011-10-25 PY - 2011 AN - OPUS4-24734 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rohrmann, Rolf A1 - Rücker, Werner A1 - Thöns, Sebastian T1 - Integrated Monitoring Systems for Offshore Wind Turbines T2 - 6th International Workshop on Structural Health Monitoring CY - Stanford, USA DA - 2007-09-11 KW - Integrated Monitoring System KW - Damage Identification KW - Load Monitoring KW - Wind turbines PY - 2007 SP - 1 EP - 8 AN - OPUS4-16280 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Assessment and monitoring of reliability and robustness of offshore wind energy converters T2 - ESREL 2008 CY - Valencia, Spain DA - 2008-09-22 PY - 2008 AN - OPUS4-18076 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Verfahren der Lebenszykluskurven auf der Grundlage der Tragwerkszuverlässigkeit T2 - VDI Wissensforum: Bauwerksmonitoring CY - Hamburg, Germany DA - 2013-04-17 PY - 2013 AN - OPUS4-28112 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Überwachung von Brückenbauwerken in Deutschland T2 - Seminar zu ausgewählten Problemstellungen beim Entwerfen, dem Bau und der Überwachung, aktueller Brückenbauprojekte. CY - Gdansk, Poland DA - 2011-06-14 PY - 2011 AN - OPUS4-23995 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian A1 - Döhler, M. ED - del Grosso, A. E. ED - Basso, P. T1 - Structural reliability updating with stochastic subspace damage detection information N2 - Damage detection algorithms as a part of Structural Health Monitoring (SHM) are widely applied in research and industry and have shown their capabilities to efficiently detect structural damages. These algorithms usually compare a model front a safe reference state of a structure to Vibration data from a possibly damaged state. For such a comparison, special properties of real Vibration data introduce uncertainties, such as low signal-to-noise ratios, non-stationary or nonwhite ambient excitation, non-linear behavior and many more. Recently, Statistical damage detection algorithms based on stochastic subspace Identification have been proposed that take into account the uncertainties in the data. Building upon the uncertainty modeling, the next step in the view of the authors is to utilize damage detection algorithm information in the context of the structural reliability theory. Therefore, this paper introduces an approach for the updating of the structural reliability with damage detection algorithm information. Two steps are described namely the determination of a probability of detection (PoD) distribution function for damage detection algorithms accounting for the relevant uncertainties and the concept of Bayesian updating of the structural reliability. The introduced approaches are applied in generic examples. In this way the potential of the utilization of damage detection system information for more reliable structural systems are demonstrated. T2 - EACS 2012 - Smart Structures - 5th European Conference on Structural Control CY - Genoa, Italy DA - 18.06.2012 KW - Stochastic subspace KW - Structural reliability KW - Bayesian updating KW - Probability of detection PY - 2012 SN - 978-88-95023-13-7 IS - Paper #008 SP - 1 EP - 12 PB - Erredi Grafiche Editoriali CY - Genoa AN - OPUS4-26181 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rabe, Frederik A1 - Löhnert, Andrea A1 - Knaust, Christian A1 - Thöns, Sebastian T1 - Numerical quantification of fire smoke toxicity in tunnels N2 - Vehicle fires in tunnels can have catastrophic consequences for the road users, the property and traffic inffastructure. To support an evacuation planning, this study simulates the fire smoke toxicity and the smoke layer of a vehicle fire in a full-size test tunnel. The three dimensional prediction of the fire smoke toxicity in the test tunnel is realized by implementing the Fractional Effective Dose and the Fractional Summation concept in a CFD environment. The developed model facilitates to calculate fire scenarios for various types of tunnels and to quantify the hazard e.g. during an evacuation scenario. T2 - ISAVFT 15 - 15th International symposium on aerodynamics, ventilation and fire in tunnels CY - Barcelona, Spain DA - 18.09.2013 KW - Toxicity KW - Fire KW - Smoke KW - Tunnel KW - FED KW - Fractional effective dose PY - 2013 SN - 978-1-85598-137-9 SP - 203 EP - 215 AN - OPUS4-29719 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Berchtold, Florian A1 - Thöns, Sebastian A1 - Knaust, Christian A1 - Rogge, Andreas T1 - Review of road tunnel risk assessment - common aspects? N2 - Safety measures like tunnel emergency Ventilation Systems cause high financial costs. Hence, safety measures have to be chosen with the focus on the expected reduction of the consequences like fatalities or damage on structures and in conjunction with the investments. Since 2004, the European directive EU 2004/54/EC proposes therefore the application of risk assessments. Because the EU directive provides only few legal requirements on risk assessments, the methodologies developed on this basis have large differences. After one decade of intensive research, the comparative study now highlights common aspects and differences of several methodologies. T2 - 6th International symposium on tunnel safety and security CY - Marseille, France DA - 12.03.2014 KW - Tunnel KW - System KW - Risk assessment KW - Fire KW - Safety KW - Comparative study PY - 2014 SP - 669 EP - 670 AN - OPUS4-31256 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Integral Monitoring System for Offshore Wind Turbines T2 - IRIS Summer Academy CY - Zell am See, Austria DA - 2009-04-01 PY - 2009 AN - OPUS4-20076 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Messkonzept für die Strukturüberwachung der Multibrid M5000 T2 - InnoNet-Status-Seminar CY - Bremen, Germany DA - 2006-11-21 PY - 2006 AN - OPUS4-18628 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rücker, Werner A1 - Thöns, Sebastian A1 - Said, Samir A1 - Schmid, Wolfgang ED - Zingoni, A. T1 - SHM strategies, application and measurements on tripod offshore wind energy converters within the German offshore park Alpha Ventus N2 - Prototypes of wind turbines of the megawatt dass are to be built and tested until 2008 within a German offshore wind energy test field in the North Sea (ALPHA VENTUS). To ensure a high operational reliability of offshore wind turbines with economically acceptable repair and maintenance efforts, comprehensive diagnosis and supervision concepts are required. Automatic monitoring Systems will be an essential part of such concepts. Because of the fact, that during Operation there will be static and dynamic interaction between the components ‘structure’, ‘machinery’ and ‘blades’ it is necessary to develop the monitoring techniques in an overall concept. These monitoring Systems are supposed to be applied for the design and testing as well as for the Operation and maintenance phases. In the paper the developed approaches for the measurement of actions and the condition monitoring of all components of an offshore wind energy plant will be shown. T2 - Research and applications in structural engineering, mechanics and computation - 5th International conference on structural engineering, mechanics and computation CY - Cape Town, South Africa DA - 02.09.2013 PY - 2013 SN - 978-1-138-00061-2 SN - 978-1-315-85078-8 SP - 977 EP - 982 PB - CRC Press AN - OPUS4-29104 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thöns, Sebastian A1 - Schneider, Ronald T1 - The Influence of brittle Daniels system characteristics on the value of load monitoring information N2 - This paper addresses the influence of deteriorating brittle Daniels system characteristics on the value of structural health monitoring (SHM). The value of SHM is quantified as the difference between the life cycle benefits with and without SHM. A value of SHM analysis is performed within the framework of the Bayesian pre-posterior decision theory and requires (1) structural performance modelling and prediction, (2) structural integrity management models, (3) the (pre-posterior) modelling of SHM and (4) the coupling of SHM and the structural performance models. The pre-posterior decision theoretical framework facilitates that the value of SHM can be quantified before the SHM system is quantified and before data are acquired. The results of this study support decisions to select structural systems for which the SHM strategy load monitoring is optimal. T2 - 8th European Workshop on Structural Health Monitoring (EWSHM 2016) CY - Bilbao, Spain DA - 05.07.2016 KW - Value of information KW - Structural performance KW - Deterioration KW - Daniels systems PY - 2016 UR - http://www.ndt.net/?id=20186 SN - 1435-4934 VL - 21 IS - 8 SP - 1 EP - 9 PB - NDT.net CY - Kirchwald AN - OPUS4-38217 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hu, Wei-Hua A1 - Thöns, Sebastian A1 - Rohrmann, Rolf A1 - Said, Samir A1 - Rücker, Werner T1 - Vibration-based structural health monitoring of a wind turbine system. Part II: Environmental/operational effects on dynamic properties N2 - The second part of these companion papers mainly researches environmental/operational influences on structural dynamic properties under normal operational conditions during two years, in order to extract a statistical based damage-sensitive indicator for health monitoring of a wind turbine system. The correlation analyses between experimental identified frequencies, damping values as well as mode shapes and environmental/operational factors such as rotation speed of blades, wind speed, pitch angle, temperature and nacelle direction are presented. It is observed that the frequency estimates are influenced by the nacelle position, the activation of rotor, the rotation speed of blades and the wind speed as well as the temperature. Regarding to the damping estimates, they are mainly associated with variation of the aerodynamic damping due to the increasing wind speed. Besides, the resonance phenomenon is also observed in higher modes. The harmonic frequencies due to blades passing by tower are found and the corresponding damping value decreases. Moreover, the mode shapes in some modes are strongly affected by the position of the nacelle. Subsequently, two types of simulated damage including the reduction of stiffness in both the rotor blade and the tubular tower are successfully detected by applying the Principal Component Analysis (PCA) based methods to these temperature-sensitive frequency estimates. Comparison of change of the extracted health features indicates that they are more sensitive with the tower damage. KW - Vibration KW - Structural health monitoring KW - Wind turbine KW - Environmental/operational effects KW - Modal properties KW - Principal Component Analysis KW - Novelty analysis KW - Damage detection KW - Sommerfeld effect KW - Automated operational modal analysis KW - Resonance PY - 2015 DO - https://doi.org/10.1016/j.engstruct.2014.12.035 SN - 0141-0296 VL - 89 SP - 273 EP - 290 PB - Elsevier Ltd. CY - Oxford AN - OPUS4-32879 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hu, Wei-Hua A1 - Thöns, Sebastian A1 - Rohrmann, Rolf A1 - Said, Samir A1 - Rücker, Werner T1 - Vibration-based structural health monitoring of a wind turbine system. Part I: Resonance phenomenon N2 - This paper is focused on a resonance phenomenon of a wind turbine system in 5 MW class, on the basis of dynamic signals acquired continuously from the tubular tower under normal operational conditions during two years. Firstly, technique specifications of the wind turbine system are introduced and a finite element model is developed to characterize the structural dynamic properties. The following part describes the continuous dynamic monitoring system integrated with an automated operational modal analysis procedure using the poly-reference Least Squares Complex Frequency domain (p-LSCF) method. Subsequently, variations and mutual relationships of environmental/operational factors such as vibration amplitude, temperature, wind speed, rotation speed of blades, pitch angle and nacelle direction are also presented. Finally, significant resonance is observed due to the fundamental frequency of the tower matching with the harmonic frequency induced by the rotation of three blades. As the rotation speed of rotor approaches to 8 rpm, the vibration amplitude of the tower increases significantly and the corresponding damping value decreases. With the further rising wind velocity, the rotation speed of blades stops increasing and the input energy just contribute to accumulate the vibration amplitude of tower. Such observation indicates the Sommerfeld effect that aggravates the resonance phenomenon. A vibration control device is necessary to minimize the excessive structural responses. A companion paper will further discuss the environmental/operational effects on dynamic properties of the wind turbine system under the operational conditions. KW - Vibration KW - Structural health monitoring KW - Wind turbine KW - Automated operational modal analysis KW - Resonance KW - Sommerfeld effect PY - 2015 DO - https://doi.org/10.1016/j.engstruct.2014.12.034 SN - 0141-0296 VL - 89 SP - 260 EP - 272 PB - Elsevier Ltd. CY - Oxford AN - OPUS4-32878 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rohrmann, Rolf A1 - Rücker, Werner A1 - Thöns, Sebastian A1 - Said, Samir T1 - Design and operation of integrated monitoring systems for offshore wind turbines N2 - To ensure a high operational reliability of future generations of offshore wind conversion systems (OWEC) with economically acceptable repair and maintenance efforts, comprehensive diagnosis and supervision concepts are required. Automatic monitoring systems will be an essential part of such concepts. Because of the fact, that during operation there will be static and dynamic interaction between the components 'structure', 'machinery' and 'blades' it is necessary to develop the monitoring techniques in an overall concept. These monitoring systems are supposed to be applied for the design and testing as well as for the operation and maintenance phases. The used methods are focused on the design requirements for the structure, which are stated in the respective standards and certification guidelines. For the validation of the design, methods are specified which would be also applicable for SHM in the operating condition, e.g. for the evaluation of the structural conditon possibly after the occurrence of damages or changes. The further task consists in the realization of condition monitoring for all components, aiming at early damage detection and the observation of the damage development and its evaluation. Here the task consists of determining with assessment procedures the optimum time for maintenance actions to be carried out. T2 - DEWEK 2008 - 9th German wind energy conference CY - Bremen, Germany DA - 2008-11-26 KW - Integrated monitoring system KW - Offshore wind turbines KW - Assessment KW - Damage identification KW - Load monitoring PY - 2008 SP - 1 EP - 4(?) AN - OPUS4-19872 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - SHM Standardisation Aspects T2 - International Workshop on Structural Health Monitoring 2013 (WSHM 2013) CY - Stanford, CA, USA DA - 2013-09-09 PY - 2013 AN - OPUS4-29182 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thöns, Sebastian T1 - On the Value of Monitoring Information for the Structural Integrity and Risk Management N2 - This article introduces an approach and framework for the quantification of the value of structural health monitoring (SHM) in the context of the structural risk and integrity management for systems. The quantification of the value of SHM builds upon the Bayesian decision and utility theory, which facilitates the assessment of the value of information associated with SHM. The principal approach for the quantification of the value of SHM is formulated by modeling the fundamental decision of performing SHM or not in conjunction with their expected utilities. The expected utilities are calculated accounting for the probabilistic performance of a system in conjunction with the associated structural integrity and risk management actions throughout the life cycle, the associated benefits, structural risks, and costs and when performing SHM, the SHM information, their probabilistic outcomes, and costs. The calculation of the expected utilities necessitates a comprehensive and rigorous modeling, which is introduced close to the original formulations and for which analysis characteristics and simplifications are described and derived. The framework provides the basis for the optimization of the structural risk and integrity management based on utility gains including or excluding SHM and inspection information. Studies of fatigue deteriorating structural Systems and their characteristics (1) provide decision Support for the performance of SHM, (2) explicate the influence of the structural component and system characteristics on the value of SHM, and (3) demonstrate how an integral optimization of SHM and inspection strategies for an efficient structural risk and integrity management can be performed. KW - Monitoring KW - Structural Integrity and Risk Management KW - SHM PY - 2018 DO - https://doi.org/10.1111/mice.12332 VL - 33 IS - 1 SP - 79 EP - 94 PB - John Wiley & Sons, Inc. CY - Hoboken, NJ, USA AN - OPUS4-44537 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, W.-H. A1 - Qin, J. A1 - Lu, D.-G. A1 - Thöns, Sebastian A1 - Havbro Faber, M. T1 - Vol-informed decision-making for SHM system arrangement N2 - Structural health monitoring systems have been widely implemented to provide real-time continuous data support and to ensure structural safety in the context of structural integrity management. However, the quantification of the potential benefits of structural health monitoring systems has not yet attracted widespread attention. At the same time, there is an urgent need to develop strategies, such as optimizing the monitoring period, monitoring variables, and other factors, to maximize the potential benefits of structural health monitoring systems. Considering the continuity of structural health monitoring information, a framework is developed in this article to support decision-making for structural Health monitoring systems arrangement in the context of structural integrity management, which integrates the concepts of value of information and risk-based inspection planning based on an approach which utilizes a conjugate prior probability distribution for updating of the probabilistic models of structural performances based on structural health Monitoring information. An example considering fatigue degradation of steel structures is investigated to illustrate the application of the proposed framework. The considered example shows that the choice of monitoring variables, the Monitoring period, and the monitoring quality may be consistently optimized by the application of the proposed framework and approach. Finally, discussions and conclusions are provided to clarify the potential benefits of the proposed Framework with a special view to practical applications of structural health monitoring systems. KW - Value of information KW - Structural health monitoring systems arrangement strategy KW - Structural integrity management KW - Rskbased inspection KW - Structural health monitoring information model PY - 2020 DO - https://doi.org/10.1177/1475921720962736 SN - 1475-9217 VL - 21 IS - 1 SP - 37 EP - 58 PB - SAGE Journals CY - USA AN - OPUS4-53064 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schneider, Ronald A1 - Thöns, Sebastian A1 - Rücker, Werner A1 - Straub, D. ED - Deodatis, G. ED - Ellingwood, B.R. ED - Frangopol, D.M. T1 - Effect of different inspections strategies on the reliability of Daniels systems subjected to fatigue N2 - Inspections are an efficient means of enhancing the reliability of redundant structural Systems subjected to fatigue. To investigate the effect of such inspections, we represent the deterioration state of a Daniels System by means of a probabilistic fatigue crack growth model of all elements, which considers stochastic dependence among element fatigue behavior. We include inspection results in the calculation of the System collapse probability through Bayesian updating of the System deterioration state. Based on this approach, we calculate the collapse probability of a deteriorating Daniels System conditional on different inspection strategies in terms of inspection coverage and inspection times. The acceptability of an inspection strategy is verified by comparing the calculated collapse probabilities with maximum acceptable System failure probabilities. This study is a Step towards identifying optimal inspection strategies for redundant structural Systems subjected to fatigue. T2 - 11th International conference on structural safety and reliability - Safety, reliability, risk and life-cycle performance of structures and infrastructures CY - New York, USA DA - 16.06.2013 PY - 2013 SN - 978-1-138-00086-5 SN - 978-1-315-88488-2 SP - 1 EP - 8 PB - CRC Press CY - Leiden, The Netherlands AN - OPUS4-28984 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Utilization of Monitoring and Damage Detection Procedures for Risk Optimization and Operation Support. T2 - IRIS Week 2010 CY - Vienna, Austria DA - 2010-11-10 PY - 2010 AN - OPUS4-22631 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Fallstudie einer Offshore-Windenergieanlage T2 - VDI Wissensforum: Bauwerksmonitoring CY - Hamburg, Germany DA - 2013-04-17 PY - 2013 AN - OPUS4-28110 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - On the Value of Structural Health Monitoring T2 - ESREL 2013 Conference CY - Amsterdam, Netherlands DA - 2013-09-29 PY - 2013 AN - OPUS4-29490 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Faber, M.H. A1 - Thöns, Sebastian ED - Miraglia, S. ED - Vrouwenvelder, A.C.W.M. ED - Steenbergen, R.D.J.M. ED - Van Gelder, P.H.A.J.M. T1 - On the value of structural health monitoring N2 - Health monitoring has, over the last 2-3 decades, become a topic of significant interest within the structural engineering research community, but also in the broader areas of civil and mechanical engineering. Whereas the merits of Structural Health Monitoring (SHM) are generally appreciated in qualitative terms there has, as of yet, not been reported much fundamental research on the quantification of the benefit of SHM. The present paper addresses the quantification of SHM with basis in the Bayesian pre-posterior decision analysis. The starting points are historical and recent developments in the fields of SHM and the quantification of value of information as well as the identification of typical situations in structural engineering in which SHM has the potential to provide value beyond its costs. Subsequently, the theoretical framework which allows for the quantification of the value of information collected through SHM Systems is developed and elaborated. It is shown how the value of information can be quantified to support the assessment and optimization of decisions on whether and how to implement SHM. To illustrate the use of the developed theoretical framework for evaiuating the benefit of SHM an example is provided. The example addresses the life-cycle benefit maximization for offshore jacket structures subject to fatigue crack growth utilizing monitoring of near field fatigue stresses as a means of optimizing risk based inspection and maintenance strategies. T2 - 22nd ESREL conference - Safety, reliability and risk analysis: Beyond the horizon CY - Amsterdam, The Netherlands DA - 29.09.2013 PY - 2014 SN - 978-1-138-00123-7 SP - 2535 EP - 2544 PB - Taylor & Francis AN - OPUS4-29894 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Buckling reliability of steel shells utilising the Eurocode 3 methodology T2 - JCSS workshop on FEM and reliability code requirements, TU Delft CY - Delft, Netherlands DA - 2009-12-01 PY - 2009 AN - OPUS4-20910 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Überwachungssysteme zur Unterstützung des Managements der Bauwerksintegrität von Brücken T2 - Vortrag an der Bundesanstalt für Straßenwesen CY - Bergisch Gladbach, Germany DA - 2011-08-17 PY - 2011 AN - OPUS4-24547 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hu, Wei-Hua A1 - Thöns, Sebastian A1 - Said, Samir A1 - Rücker, Werner ED - Cunha, A. ED - Caetano, E. ED - Ribeiro, P. ED - Müller, G. T1 - Resonance phenomenon in a wind turbine system under operational conditions N2 - A prototype of wind turbines in 5 megawatt dass was built and tested at the first German offshore wind energy test fteld in the North Sea. In order to investigate dynamic behaviors under a complex state of loads, a continuous dynamic monitoring System was implemented by Federal Institute for Material Research and Testing (BAM). It recorded structural responses and environmental/operational variables from November 2007 to October 2009. This paper presents significant resonance phenomenon due to the interaction in the tower-nacelle System under operational conditions. Modal parameters are automatically estimated by the poly reference Least Square Complex Frequency domain (p-LSCF) method. Campbell plot demonstrates that a three-blade passage frequency and its multiples f3n match with the natural frequencies of the wind turbine System in several modal Orders. The damping estimates decrease and the Vibration amplitude increase significantly. A control System is necessary to minimize the excessive vibrations. T2 - EURODYN 2014 - 9th International conference on structural dynamics CY - Porto, Portugal DA - 30.06.2014 KW - Wind turbine KW - Tower-nacelle system KW - Resonance KW - Continuous dynamic monitoring KW - Automated operational modal analysis PY - 2014 SN - 978-972-752-165-4 SN - 2311-9020 SP - 3619 EP - 3626 AN - OPUS4-32970 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian A1 - McMillan, D. T1 - Condition monitoring benefit for offshore wind turbines N2 - As more offshore wind parks are commissioned, the focus will inevitably shift from a planuing, construction and warranty focus to an Operation, maintenance and investment payback focus. In this latter case, both short-term risks associated with wind turbine component assemblies, and longterm risks related to structural integrity of the Support structure, are highly important. This research focuses on the role of condition monitoring to lower costs associated with short-term reliability and long-term asset integrity. This enables comparative estimates of life cycle costs and reduction in uncertainty, both of which are of value to Investors. T2 - PMAPS 2012 - 12th International Conference on Probabilistic Methods Applied to Power Systems CY - Istanbul, Turkey DA - 10.06.2012 KW - Condition monitoring KW - Offshore wind KW - Operation KW - Risk KW - Life cycle KW - Cost KW - Cost benefit analysis KW - Offshore wind turbine KW - Operation management KW - Structural integrity management PY - 2012 SP - 37 EP - 42 PB - Istanbul Technical University CY - Instanbul, Turkey AN - OPUS4-26117 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Support Structure Reliability of Offshore Wind Turbines Utilizing an Adaptive Response Surface Method T2 - 29th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2010) CY - Shanghai, China DA - 2010-06-06 PY - 2010 AN - OPUS4-21650 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Probabilistische Zustandsbewertungsverfahren für Offshore-Windenergieanlagen T2 - IMO-WIND Statusseminar, BAM CY - Berlin, Germany DA - 2009-10-01 PY - 2009 AN - OPUS4-20079 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian A1 - Hille, Falk T1 - Damage detection and risk estimation of bridge S101 T2 - IRIS Summer Academy CY - Zell am See, Austria DA - 2009-04-01 PY - 2009 AN - OPUS4-20495 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schneider, Ronald A1 - Thöns, Sebastian A1 - Straub, D. ED - Strauss, A. ED - Frangopol, D.M. ED - Bergmeister, K. T1 - Probalistic fatigue crack growth modeling for reliability-based inspection planning N2 - The fatigue deterioration modeling for welded steel structures subjected to high cycle fatigue is presented in the current document. The aim of this paper is to formulate approaches based on actual Research results for the phases fatigue crack initiation, fatigue propagation and fatigue failure. The physical characteristics of the approaches are discussed in combination with the associated uncertainties and the probabilistic modeling of this time variant reliability problem. The fatigue deterioration modeling documented here serve as a basis for a reliability-based approach to inspection planning. T2 - 3rd International symposium on life-cycle civil engineering CY - Vienna, Austria DA - 03.10.2012 PY - 2012 SN - 978-0-415-62126-7 SP - 319 EP - 326 PB - CRC Press AN - OPUS4-27067 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rohrmann, Rolf A1 - Said, Samir A1 - Schmid, Wolfgang A1 - Thöns, Sebastian A1 - Bicker, S. A1 - Rücker, Werner ED - De Roeck, G. ED - Degrande, G. ED - Lombaert, G. ED - Müller, G. T1 - Results from monitoring and assessment of offshore wind turbines N2 - To ensure a high operational reliability of offshore wind turbines (OWEC) with economically acceptable repair and maintenance efforts, comprehensive diagnosis and supervision concepts are required. Automatic monitoring Systems will be an essential part of such concepts. Because of the fact, that during Operation there will be static and dynamic interaction between the components ‘structure’, ‘machinery’ and ‘blades’ it is necessary to develop the monitoring techniques in an overall concept. These monitoring Systems are supposed to be applied for the design and testing as well as for the Operation and maintenance phases. The knowledge of the dynamic behavior of wind turbines is important both for the design and for a safe Operation. The available monitoring data from a period of three years, allow first conclusions on the long-term Operation of such Systems in terms of quality requirements to the instrumentation to the structure and the rotor blades T2 - EURODYN 2011 - 8th International conference on structural dynamics CY - Leuven, Belgium DA - 04.07.2011 KW - Integrated monitoring system KW - Offshore wind turbines KW - Structural assessment KW - Limit values KW - Measurement hardware KW - Data management KW - Embedded FBG sensors KW - Data analysis KW - Damage detection KW - Rotor blades PY - 2011 SN - 978-90-760-1931-4 IS - MS25 SP - 3450 EP - 3456 AN - OPUS4-24293 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grasse, Fabian A1 - Trappe, Volker A1 - Thöns, Sebastian A1 - Said, Samir ED - De Roeck, G. ED - Degrande, G. ED - Lombaert, G. ED - Müller, G. T1 - Structural health monitoring of wind turbine blades by strain measurement and vibration analysis N2 - Wind turbine blades have to withstand a high number of load cycles in mostly hard weather conditions over 20 years. In a research project BAM and several partners have designed, evaluated and tested a condition monitoring system for all parts of a wind turbine. At a rotorblade with a length of 58 m fibre bragg grating sensors were applied for in-service strain measurement. Additionally a complex test rig was designed to enable real biaxial loading conditions at a representative test rotor blade to simulate the mechanical loading conditions in the lab. In this test blade with a length of 8 m also fibre bragg grating sensors were implemented to determine their influences for the structure and the condition monitoring system. Vibration measurements were carried out at different test phases. The results were compared with finite element strain and modal analysis. T2 - EURODYN 2011 - 8th International conference on structural dynamics CY - Leuven, Belgium DA - 04.07.2011 KW - Rotor blade KW - Test blade KW - Modal analysis KW - Condition monitoring PY - 2011 SN - 978-90-760-1931-4 IS - MS25 Tue SP - 3490 EP - 3497 AN - OPUS4-25076 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thöns, Sebastian T1 - Monitoring- und Risikoanalyseverfahren am Beispriel von Offshore-Windenergieanlagen T2 - BAM Kolloquium CY - Berlin, Germany DA - 2009-09-30 PY - 2009 AN - OPUS4-20078 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Thöns, Sebastian A1 - McMillan, D. ED - Karki, R. ED - Billinton, R. ED - Vermar, A.K. T1 - Condition monitoring benefit for operation support of offshore wind turbines N2 - As more offshore wind parks are commissioned, the focus will inevitably shift from a planning, construction, and warranty focus to an operation, maintenance, and investment payback focus. In this latter case, both short-term risks associated with wind turbine component assemblies, and long-term risks related to integrity of the support structure, are highly important. This research focuses on the role of condition monitoring to lower costs and risks associated with short-term reliability and long-term asset integrity. This enables comparative estimates of the life cycle costs and reduction in uncertainty, both of which are of value to investors. KW - Condition monitoring KW - Offshore wind KW - OperationRisk KW - Life cycle cost PY - 2014 SN - 978-81-322-1797-8 SN - 978-81-322-1798-5 DO - https://doi.org/10.1007/978-81-322-1798-5_11 N1 - Serientitel: Reliable and sustainable electric power and energy systems management – Series title: Reliable and sustainable electric power and energy systems management SP - 169 EP - 182 PB - Springer AN - OPUS4-31275 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thöns, Sebastian A1 - Döhler, M. A1 - Long, Lijia T1 - On Damage Detection System Information for Structural Systems N2 - Damage detection systems (DDS) provide information of the structural system integrity in contrast to e.g. local information by inspections or non-destructive testing techniques. In this paper, an approach is developed and demonstrated to utilize DDS information to update the structural system reliability and to integrate this information in structural system risk and utility analyses. For this aim, a novel performance modelling of DDS building upon their system characteristics and non-destructive testing reliability is introduced. The DDS performance modelling accounts for a measurement system in combination with a damage detection algorithm attached to a structural system in the reference and damage states and is modelled with the probability of indication accounting for type I and II errors. In this way, the basis for DDS performance comparison and assessment is provided accounting for the dependencies between the damage states in a structure. For updating of the structural system reliability, an approach is developed based on Bayesian updating facilitating the use of DDS information on structural system level and thus for a structural system risk analysis. The structural system risk analysis encompasses the static, dynamic, deterioration, reliability and consequence models, which provide the basis for the system model for calculating the direct risks due to component failure and the indirect risks due to system failure. Two case studies with the developed approach demonstrate a high Value of DDS Information due to risk and expected cost reduction. KW - Damage detection KW - Value of Information KW - Structural systems KW - Damage detection uncertainty PY - 2018 DO - https://doi.org/10.1080/10168664.2018.1459222 VL - 28 IS - 3 SP - 255 EP - 268 PB - Taylor & Francis AN - OPUS4-46964 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schneider, Ronald A1 - Thöns, Sebastian A1 - Rogge, Andreas ED - Bucher, Christian ED - Ellingwood, Bruce R. ED - Frangopol, Dan M. T1 - Simulating the service life performance of an inspected group of jacket-type structures N2 - A novel method for risk-based optimization of inspection and repair strategies for deteriorating structural systems has recently been proposed. The method defines heuristics at the system level to reduce the number of possible strategies. For each defined strategy, it computes the updated system failure probability conditional on simulated inspection and repair histories, and evaluates the associated costs and risk. The expected total service life costs and risk for a strategy are finally determined using Monte Carlo simulation. The optimal strategy minimizes the expected total service life costs and risk. We intend to adopt this approach to optimize inspection, monitoring and repair activities for offshore wind park support structures. As a first step, we simulate – in analogy to an offshore wind park – the service life performance of an inspected group of jacket-type frames. The performance is quantified in terms of the group’s system failure probability conditional on simulated inspection and repair histories. The underlying system model accounts for the structural redundancy of the frames and the interdependence among their failure events due to similar loading conditions. The model also captures stochastic dependence among the deterioration states of the frames. As part of the simulation process the a-priori unknown outcome of any planned inspection is generated conditional on the outcome of all previous inspections. T2 - 12th International Conference on Structural Safety and Reliability CY - Vienna, Austria DA - 06.08.2017 KW - Reliability KW - Fatigue KW - Inspection KW - Service life performance KW - Inspection planning PY - 2017 SN - 978-3-903024-28-1 SP - 2738 EP - 2747 PB - TU-MV Media Verlag GmbH CY - Vienna, Austria AN - OPUS4-41344 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kapoor, M. A1 - Sørensen, J. D. A1 - Ghosh, S. A1 - Thöns, Sebastian T1 - Decision theoretic approach for identification of optimal proof load with sparse resistance information N2 - Proof load testing may be performed to confirm the reliability of the bridge for an existing classification or to prove the reliability for a higher classification. In this paper, a probabilistic decision analysis approach is applied to the scenario for the evaluation of target proof load in the situation where information on the bridge resistance model is lacking. In this case, the resistance model is established by proof loading and taking very basic prior knowledge into account. The decision scenario is modelled in the context of the proof load test planner who shall choose the required load level for assessment of a bridge. The choice of the load level depends on the risks due to the testing and the expected benefit gain from the test. Information acquired about the loading response from monitoring during the proof load testing is modelled by taking basis in the model uncertainty formulation. The optimal proof load level for classification of a single lane, simply supported bridge of 8m span subjected to live load from very heavy (gross weight > 80 tons) transport vehicles was calculated. The optimal proof load level was identified as leading to a positive expected benefit gain to the decision maker while also satisfying target reliability criteria for remaining service life. The analysis was performed for the evaluation of bridge performance with respect to five classifications of very heavy transport vehicles with different vehicle weights and configurations. T2 - 10th International Conference on Bridge Maintenance, Safety and Management (IABMAS) CY - Sapporo, Japan DA - 11.04.2021 KW - Proof load testing KW - Probabilistic decision analysis KW - Bridge resistance model PY - 2021 SN - 978-0-429-27911-9 DO - https://doi.org/10.1201/9780429279119-104 SP - 789 EP - 797 PB - CRC Press CY - Boca Raton, Florida AN - OPUS4-57879 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -