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 U6 - 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 U6 - 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 U6 - 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 U6 - 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 - 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 - GEN A1 - Thöns, Sebastian A1 - Faber, M.H. A1 - Rücker, Werner A1 - Rohrmann, Rolf ED - Martorell, S. ED - et al., T1 - Assessment and monitoring of reliability and robustness of offshore wind energy converters T2 - ESREL 2008 CY - Valencia, Spain DA - 2008-09-22 KW - Structural reliability KW - Robustness KW - Monitoring KW - Risk KW - Wind energy converter PY - 2008 SN - 978-0-415-48513-5 SP - 1567 EP - 1572 PB - Taylor & Francis CY - London, UK AN - OPUS4-18565 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 - CHAP A1 - Thöns, Sebastian A1 - Faber, M.H. A1 - Rücker, Werner T1 - Life cycle cost optimized monitoring systems for offshore wind turbine structures N2 - Monitoring information should be utilized to support optimal decisions. In this sense monitoring systems should be designed such as to optimize expected Life Cycle Costs. PY - 2013 SN - 978-3-200-03179-1 IS - Chapter 4 SP - 75 EP - 90 CY - Vienna, Austria AN - OPUS4-29103 LA - eng 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 - 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 - 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 - 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 U6 - 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 - RPRT A1 - Fischer, J. A1 - Straub, D. A1 - Schneider, Ronald A1 - Thöns, Sebastian A1 - Rücker, Werner T1 - Intelligente Brücke - Zuverlässigkeitsbasierte Bewertung von Brückenbauwerken unter Berücksichtigung von Inspektions- und Überwachungsergebnissen N2 - Der vorliegende Bericht beschreibt Konzepte für eine intelligente Brücke auf der Grundlage einer zuverlässigkeitsbasierten Zustandsbewertung unter Berücksichtigung von Bauwerksinformationen, welche aus Prüfungen, Inspektionen und Überwachung gewonnen werden. Das Brückensystem wird durch ein Modell beschrieben, welches den zentralen Teil des Konzeptes darstellt. Das Modell wird in Schädigungsmodelle und ein Tragwerkssystem-Modell unterteilt. Dieses Modell wird a-priori durch die Eingangsdaten (welche etwa die Geometrie, die Materialien und die Verwendung der Brücke beschreiben) charakterisiert. Aus diesen ergeben sich dann auch die Ausgangsmodelle. Um die signifikanten Streuungen und Unsicherheiten adäquat abzubilden sind diese Modelle probabilistisch. Das Modell liefert eine sich kontinuierlich ändernde probabilistische Zustandsbewertung. Die Zustandsbewertung gibt eine Aussage über den Zustand und die Zuverlässigkeit des Brückensystems und seiner Bauteile und dient als Grundlage für die Planung und die Optimierung von Maßnahmen. Die Verwendung von Resultaten aus Inspektionen, Prüfungen und Überwachungen erfolgt durch eine Aktualisierung der Modellparameter. Die Aktualisierung beruht auf der Methode der Bayes'schen Aktualisierung und wird auf der Grundlage der entwickelten Klassifizierung der Bauwerksinformationen mit entsprechenden Methoden durchgeführt. Dieses Verfahren erlaubt es, alle Informationen in konsistenter Weise in ein einziges Modell einfließen zu lassen. Dabei wird die Genauigkeit und Aussagekraft der gewonnenen Daten und Beobachtungen explizit berücksichtigt. Durch die Aktualisierung der Modellparameter unter Berücksichtigung von Systemeffekten wird die Zustandsbewertung der Bauteile und des Brückensystems aktualisiert. Das ermöglicht die Planung und die Optimierung von Maßnahmen unter Berücksichtigung der Bauwerksinformationen. Auf diese Weise wird die intelligente Brücke mit Inspektionen und Überwachungen zu einem adaptiven System, welches sich Veränderungen anpassen kann.---------------------------------------------------------------------------------------------------------------------------------------------------------------------------This report describes concepts for an intelligent bridge on the basis of a reliability-based condition assessment utilizing inspection and monitoring data. The central part of the concept is a model describing the bridge system. The overall bridge model is comprised of deterioration models and a mechanical system model of the structure. The model is a-priori characterized by the input data (such as the geometry, the materials, and the utilization of the bridge). Significant uncertainties in the deterioration modeling as well as the load conditions motivate a probabilistic modeling. The model enables a continuously updated probabilistic condition assessment. It provides information about the condition and the reliability of the bridge system and its components and serves as a basis for the planning and the optimization of maintenance actions. Inspection, measurement, and monitoring information are included by updating the model parameters. Bayesian updating is utilized for the updating of the model parameters and is performed on the basis of the developed classification of structural information and the corresponding procedures. These methodologies allow to consistently incorporate all available information into the model and the prediction. Thereby, the precision and the validity of the data and observations are explicitly accounted for. The condition assessment of the bridge system and its components is updated by updating the model parameters, and maintenance actions can be planned and optimized taking into account all available information in a rational and consistent manner. In this way, the intelligent bridge with inspections, measurements, and monitoring information becomes an adaptive system, which has the ability to adjust to changes. KW - Berechnung KW - Brücke KW - Dauerhaftigkeit KW - Deutschland KW - Echtzeit KW - Forschungsbericht KW - Kontinuierlich KW - Kontrolle KW - Messung KW - Prognose KW - Prüfverfahren KW - Rechenmodell KW - Sachschaden KW - Tragfähigkeit KW - Wahrscheinlichkeit KW - Zustandsbewertung PY - 2014 UR - http://bast.opus.hbz-nrw.de/volltexte/2014/768/pdf/BASt_B_99_ELBA_PDF.pdf SN - 978-3-95606-078-6 SN - 0943-9293 IS - B 99 SP - 1 EP - 111 PB - Fachverlag NW in der Carl Schünemann Verlag GmbH CY - Bremen AN - OPUS4-31300 LA - deu 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 - 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 U6 - 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 - 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 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 - 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 - 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 U6 - 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 U6 - 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 - 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 -