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. -------------------------------------------------------------------------------------------------------------------------------------------------------------------- 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 SN - 0932-8351 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 - JOUR A1 - Thöns, Sebastian A1 - Faber, M.H. A1 - Rücker, Werner T1 - Ultimate limit state model basis for assessment of offshore wind energy converters N2 - This paper establishes the model basis regarding the ultimate limit state consisting of structural, loading, and probabilistic models of the support structure of offshore wind energy converters together with a sensitivity study. The model basis is part of a risk based assessment and monitoring framework and will be applied for establishing the 'as designed and constructed' reliability as prior information for the assessment and as a basis for designing a monitoring system. The model basis is derived considering the constitutive physical equations and the methodology of solving these which then in combination with the ultimate limit state requirements leads to the specific constitutive relations. As a result finite element models based on shell elements incorporating a structural and a loading model are introduced and described in detail. Applying these models the ultimate capacity of the support structure and the tripod structure are determined with a geometrically and materially nonlinear finite element analysis. The observed failure mechanisms are the basis for the definition of the ultimate limit state responses. A probabilistic model accounting for the uncertainties involved is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. In combination with the developed structural and loading models, sensitivity analyses in regard to the responses are performed to enhance the understanding and to refine the developed models. To this end, as the developed models necessitate substantial numerical efforts for the probabilistic response analysis predetermined designs of numerical experiments are applied for the calculation of the sensitivities using the Spearman rank correlation coefficient. With this quantification of the sensitivity of the random variables on the responses including nonlinearity the refinement of the model is performed on a quantitative basis. KW - Condition monitoring KW - Failure analysis KW - Finite element analysis KW - Offshore installations KW - Probability KW - Risk analysis KW - Shells (structures) KW - Structural engineering KW - Wind power KW - Model basis KW - Offshore wind KW - Support structure KW - Sensitivity KW - Ultimate limit state PY - 2012 DO - https://doi.org/10.1115/1.4004513 SN - 0892-7219 VL - 134 IS - 3 SP - 031904-1 - 031904-9 CY - Fairfield, NJ AN - OPUS4-26358 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rücker, Werner A1 - Lüddecke, Falk A1 - Thöns, Sebastian T1 - Tragverhalten von Offshore Gründungskonstruktionen - Rechnerische und messtechnische Untersuchungen N2 - Dieser Artikel enthält eine Zusammenfassung von Ergebnissen des Forschungsverbundvorhabens 'OGOWIN: Optimierung aufgelöster Gründungsstrukturen für Offshore-Windenergieanlagen hinsichtlich Materialeinsatz, Montageablauf und neuer Fertigungsverfahren'. Die Ergebnisse umfassen (1) eine Untersuchung des dynamischen Verhaltens der verschiedenen Gründungsvarianten Monopile, Tripod und Jacket, (2) die Ermittlung einer Wöhlerlinie für den Grundwerkstoff eines Stahlgussknotens, (3) die Ermittlung der Traglast eines Stahlgussknotens in einem 1:1-Versuch sowie (4) Berechnungen zur Form- und Materialoptimierung. Zur Überwachung der Gebrauchstauglichkeit während des Betriebes wurden relevante Parameter hinsichtlich ihres Einflusses auf die ersten Eigenfrequenzen der o. g. Gründungskonstruktionen rechnerisch untersucht. Untersuchungen der Ermüdungsfestigkeit und die erstmalige experimentelle Ermittlung der Traglast eines Gussknotens tragen zu einem optimierten Entwurf durch genaue Kenntnis des Materialverhaltens und der höchstbeanspruchten Bereiche bei. Darüber hinaus konnte gezeigt werden, dass eine geometrische Optimierung des Stahlgussknotens unter konstruktiven Randbedingungen zu einer Verringerung des Materialaufwandes bzw. zu einer Erhöhung der Traglast führen kann. -------------------------------------------------------------------------------------------------------------------------------------- This paper contains a summary of the joint research project 'OGOWIN: Optimisation of support structures for offshore wind turbines regarding the material consumption, the construction and production sequence as well as new production methodologies'. The results comprise (1) a modal analyses of various types of offshore wind turbine support structures, (2) the fatigue strength testing of the cast steel material, (3) a large scale ultimate capacity test of a cast steel tube connection and (4) an optimisation of the tube connection aiming at material and stress reduction. The sensitivity of the relevant parameters on the first natural frequencies was quantified and the most influencing parameters were identified. The analyses of the fatigue strength and of the ultimate capacity of the cast steel tube connection support an optimised design by precise knowledge of the failure mechanisms and material behaviour. Moreover, it is shown that optimising the cast steel node can reduce the material use and stress concentration. KW - Gussknoten KW - Ermüdung KW - Traglast KW - Optimierung KW - Cast steel tube connection KW - Fatigue KW - Ultimate capacity KW - Optimisation KW - Meerestechnik KW - Offshore engineering KW - Stahlbau KW - Steel construction KW - Neue Verfahren/Versuchstechnik KW - New Processes/Experimental Techniques PY - 2012 DO - https://doi.org/10.1002/bate.201200022 SN - 0932-8351 SN - 1437-0999 SN - 0005-6820 SN - 0341-1052 SN - 0932-6359 SN - 0932-8351 VL - 89 IS - 12 SP - 821 EP - 830 PB - Ernst & Sohn CY - Berlin AN - OPUS4-27426 LA - deu 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 - CONF A1 - Thöns, Sebastian A1 - Rücker, Werner A1 - Faber, M.H. T1 - Support structure reliability of offshore wind turbines utilizing an adaptive response surface method T2 - OMAE 2010 - 29th International conference on ocean, offshore and arctic engineering CY - Shanghai, China DA - 2010-06-06 PY - 2010 IS - OMAE2010-20546 SP - 1 EP - 10 AN - OPUS4-21666 LA - eng 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 - CONF A1 - Thöns, Sebastian A1 - McMillan, D. T1 - Condition monitoring benefit for offshore wind turbines T2 - PMAPS 2012 - 12th International conference on Probabilistic Methods Applied to Power Systems CY - Istanbul, Turkey DA - 2012-06-10 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 AN - OPUS4-26117 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 - Fatigue and serviceability limit state model basis for assessment of offshore wind energy converters N2 - This paper develops the models for the structural performance of the loading and probabilistic characterization for the fatigue and the serviceability limit states for the support structure of offshore wind energy converters. These models and a sensitivity study are part of a risk based assessment and monitoring framework and will be applied for establishing the 'as designed and constructed' reliability as prior information for the assessment and the design of monitoring systems. The constitutive physical equations are introduced in combination with the fatigue and serviceability limit state requirements as the starting point for the development of the structural performance and loading models. With these models introduced in detail, several modeling aspects for both limit states are analyzed. This includes analyses of the influence on the hot spot stresses by applying a contact formulation for the pile guide brace connection and the application of a finite element formulation using solid elements. Further, the comparison of the natural frequencies of a discrete rotor model with a continuous rotor model is documented. To account for uncertainties associated with the structural and loading models, a probabilistic model is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. The sensitivity study is based on the calculation of a nonlinear coefficient of correlation in conjunction with predetermined designs of experiments. This is conducted by a systematic analysis of the influence of the random variables on limit state responses and hence on the structural reliability. Integrating the analyses and sensitivity studies of the fatigue and serviceability limit state models developed in this paper as well as the ultimate limit state models in Thöns et al. ('Ultimate Limit State Model Basis for Assessment of Offshore Wind Energy Converters,' ASME J. Offshore Mech. Arct. Eng.), the model basis for the assessment is completed. The process of establishing and analyzing such a model basis contributes to a detailed understanding of the deterministic and probabilistic characteristics of the structure and provides valuable insights in regard to the significance of available data. KW - Fatigue KW - Finite element analysis KW - Rotors KW - Wind power PY - 2012 DO - https://doi.org/10.1115/1.4004514 SN - 0892-7219 VL - 134 IS - 3 SP - 031905-1 - 031905-10 CY - Fairfield, NJ AN - OPUS4-26437 LA - eng 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 T2 - 22nd ESREL conference - Safety, reliability and risk analysis: Beyond the horizon CY - Amsterdam, The Netherlands DA - 2013-09-29 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 - 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 - JOUR A1 - Long, Lijia A1 - Alcover, I. F. A1 - Thöns, Sebastian T1 - Utility analysis for SHM durations and service life extension of welds on steel bridge deck N2 - Optimization of the duration of Structural Health Monitoring (SHM) campaigns is rarely performed. This article provides a utility-based solution to posteriorly determine: i) optimal monitoring Durations and ii) the extension of the service life of the welds on a steel bridge deck. The approach is Illustrated with a case study focusing on remaining fatigue life estimation of the welds on the orthotropic steel deck of the Great Belt Bridge, in Denmark. The identification of the optimal monitoring duration and the decision about extending the service life of the welds are modelled by maximizing the expected benefits and minimizing the structural risks. The results are a parametric analysis, mainly on the effect of the target probability, benefit, cost of failure, cost of rehabilitation, cost of monitoring and Discount rate on the posterior utilities of monitoring strategies and the choice of service life considering the risk variability and the costs and benefits models. The results show that the decision on short-term monitoring, i.e., 1 week every six months, is overall the most valued SHM strategy. In addition, it is found that the target probability is the most sensitive parameter affecting the optimal SHM Durations and service life extension of the welds. KW - Fatigue KW - Monitoring strategy KW - Orthotropic steel deck KW - Structural health monitoring KW - Utility and decision theory PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521719 DO - https://doi.org/10.1080/15732479.2020.1866026 SN - 1573-2479 VL - 18 IS - 4 SP - 492 EP - 504 PB - Taylor Francis Online AN - OPUS4-52171 LA - eng 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 A1 - Rücker, Werner T1 - Risikobasierte Überwachungsverfahren zur Lebensdauerverlängerung von bestehenden und neuen Bauwerken T1 - Risk based condition monitoring for life cycle extension of structures N2 - Diese Veröffentlichung enthält Konzepte zur Lebensdauerverlängerung von Bauwerken auf der Grundlage der Tragwerkszuverlässigkeitstheorie. Es werden aktuelle Forschungsergebnisse aus nationalen und europäischen Forschungsvorhaben vorgestellt. Den Schwerpunkt bildet die Verwendung von Bauwerksüberwachungsdaten unter Berücksichtigung von Messunsicherheiten zur Bestimmung der Tragwerkszuverlässigkeit. Dazu wird ein neuer Ansatz zur Bestimmung der A-posteriori Messunsicherheit vorgestellt. Es wird gezeigt, aufgrund welcher Eigenschaften der verwendeten probabilistischen Modelle die Zuverlässigkeit im Grenzzustand der Ermüdung in Bezug auf eine Lebensdauerverlängerung beeinflusst werden kann. N2 - This paper contains approaches aiming at the life cycle extension of structures on the basis of the structural reliability theory. Actual research results are presented with the focusing on the utilisation of monitoring data for the structural reliability analysis. In this context a framework for the determination of the posterior measurement uncertainty applying Bayesian Updating the process equation based measurement uncertainty with the Observation based measurement uncertainty is introduced. The general concepts for the utilisation of monitoring data and inspection data for updating the structural reliability in the view of life cycle extension are outlined. The characteristics of monitoring data in the context of the structural reliability theory are shown in detail on the basis of an example. T2 - DVM-Tag 2011 - Bauteilzuverlässigkeit - Schäden und ihre Vermeidung CY - Berlin, Germany DA - 04.05.2011 KW - Lebensdauerverlängerung KW - Tragwerkszuverlässigkeit KW - Messunsicherheit KW - Bauwerksüberwachung KW - Life cycle extension KW - Structural reliability KW - Measurement uncertainty KW - Structural monitoring PY - 2011 SN - 0946-5987 N1 - Serientitel: DVM-Bericht – Series title: DVM-Bericht IS - 678 SP - 1 EP - 10 AN - OPUS4-23720 LA - deu 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 - 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 - 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 - Long, Lijia A1 - Döhler, M. A1 - Thöns, Sebastian T1 - Determination of structural and damage detection system influencing parameters on the value of information N2 - A method to determine the influencing parameters of a structural and damage detection system is proposed based on the value of Information analysis. The value of information analysis utilizes the Bayesian pre-posterior decision theory to quantify the value of damage detection system for the structural integrity management during service life. First, the influencing parameters of the structural system, such as deterioration type and rate are introduced for the performance of the prior probabilistic system model. Then the influencing parameters on the damage detection system performance, including number of sensors, sensor locations, measurement noise, and the Type-I error are investigated. The preposterior probabilistic model is computed utilizing the Bayes’ theorem to update the prior system model with the damage indication information. Finally, the value of damage detection system is quantified as the difference between the maximum utility obtained in pre-posterior and prior analysis based on the decision tree analysis, comprising structural probabilistic models, consequences, as well as benefit and costs analysis associated with and without monitoring. With the developed approach, a case study on a statically determinate Pratt truss bridge girder is carried out to validate the method. The analysis shows that the deterioration rate is the most sensitive parameter on the effect of relative value of information over the whole service life. Furthermore, it shows that more sensors do not necessarily lead to a higher relative value of information; only specific sensor locations near the highest utilized components lead to a high relative value of information; measurement noise and the Type-I error should be controlled and be as small as possible. An optimal sensor employment with highest relative value of information is found. Moreover, it is found that the proposed method can be a powerful tool to develop optimal service life maintenance strategies—before implementation—for similar bridges and to optimize the damage detection system settings and sensor configuration for minimum expected Costs and risks. KW - Damage detection systems KW - Value of information KW - Deteriorating structures KW - Probability of damage indication KW - Decision theory PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-508083 DO - https://doi.org/10.1177/1475921719900918 SN - 1475-9217 SN - 1741-3168 VL - 21 IS - 1 SP - 19 EP - 36 PB - Sage Publications CY - Thousand Oaks, Calif. AN - OPUS4-50808 LA - eng 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 - Long, Lijia A1 - Anh Mai, Q. A1 - Morato, P. G. A1 - Dalsgaard Sorensen, J. A1 - Thöns, Sebastian T1 - Information value-based optimization of structural and environmental monitoring for offshore wind turbines support structures N2 - The use of load and structural performance measurement information is vital for efficient structural integrity management and for the cost of energy production with Offshore Wind Turbines (OWTs). OWTs are dynamically sensitive structures subject to an interaction with a control unit exposed to repeated cyclic wind and wave loads causing deterioration and fatigue. This study focuses on the quantification of the value of structural and environmental information on the integrity management of OWT structures, with the focus on fatigue of welded joints. By utilizing decision analysis, structural reliability methods, measurement data, as well as the cost-benefit models, a Value of Information (VoI) analysis can be performed to quantify the most beneficial measurement strategy. The VoI assessment is demonstrated for the integrity management of a butt welded joint of a monopile support structure for a 3 MW OWT with a hub height of approximately 71m. The conditional value of three-year measured oceanographic information and one-year strain monitoring information is quantified posteriori in conjunction with an inspection and repair planning. This paper provides insights on how much benefits can be achieved through structural and environmental information, with practical relevance on reliability-based maintenance of OWT structures. KW - Structural health monitoring KW - Offshore wind turbine KW - Monopile support structure KW - Value of information KW - Weld fatigue KW - Decision tree KW - Dynamic Bayesian Network PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514098 DO - https://doi.org/10.1016/j.renene.2020.06.038 VL - 10 IS - 159 SP - 1036 EP - 1046 PB - Elsevier Ltd. AN - OPUS4-51409 LA - eng 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 -