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 - THES A1 - Thöns, Sebastian T1 - Monitoring based condition assessment of offshore wind turbine support structures N2 - A central societal need in developed countries is the energy production with a low environmental impact. Thus ambitious energy programs have been initiated aiming at the establishment of renewable energies as a main contributor to the energy mix in the next decade. Like no other renewable energy, the offshore wind energy possesses a high potential and constitutes the main contributor to this aim. The development of large scale wind parks is one of the major challenges in the offshore industry today while the first wind parks of significant size and in considerable water depths are being built. In preparation for the next step, this thesis aims to contribute to the efficient and cost effective operation of wind parks. It specifically addresses the support of the inspection and maintenance activities of offshore wind turbines by the development of methods for the assessment and monitoring of support structures. The essential finding of this thesis is that the operation efficiency of wind turbine structures can be significantly enlarged by monitoring based assessment procedures. It is found that a substantial expected life-cycle benefit for the operation can be achieved by the conceptual integration of structural monitoring techniques in the structural reliability theory. The integration should be bidirectional in the sense that the generic design decisions for structural monitoring systems are based on a structural reliability assessment and that simultaneously a possible reduction of the uncertainty associated with the condition is utilized for the structural reliability assessment and thus for the inspection and maintenance planning. The thesis covers the issues of (I) the integration of monitoring data in the framework for structural reliability assessment of the Joint Committee on Structural Safety (JCSS), (II) the issue of the consistent determination of the measurement uncertainties utilizing all available information of the measurement process, (III) the issue of the application of monitoring techniques for structural integrity management and (IV) the establishment of a full probabilistic performance model basis for the support structure of an offshore wind turbine. To cover these issues the thesis comprises (1) the development of probabilistic structural, loading and limit state models, (2) a response surface algorithm for a multiple component reliability analysis, (3) a reliability analysis of an offshore wind turbine support structure applying the model basis, (4) a framework for the determination of measurement uncertainties utilizing process and observation data and (5) concepts for utilizing monitoring data in a structural reliability analysis as well as for the risk based inspection planning. The starting point of this thesis is the development of the model basis containing the models for the structural performance of a reference case, namely a support structure of an offshore wind turbine. The model basis comprises the structural, loading and probabilistic characterization of the ultimate, fatigue and the serviceability limit states and is derived considering the constitutive physical equations. The introduced models for the structural performance and loads account for design, production and execution information. A sensitivity study is performed on the basis of a non-linear coefficient of correlation. The process of establishing and analyzing these models contributes to an enhanced understanding of the performance of the structure and is documented in detail. The reliability analysis of an offshore wind turbine support structure builds upon the developed model basis. In order to facilitate the reliability analysis with such complex multiple component models, an adaptive response surface algorithm is developed. This algorithm utilizes clustered experimental designs in combination with an efficient augmentation scheme for these designs. The results of the reliability analyses comprise the system reliabilities and the probabilities of failure for the components in the individual limit states. With these results critical components are identified. A comparison with the target reliabilities specified in DIN EN 1990 (2002) shows that the target reliabilities are met. A novel contribution, as mentioned above, constitutes a new approach for the determination of measurement uncertainties in the context of the structural reliability theory. This approach builds upon two types of measurement uncertainties (as defined in the ISO/IEC Guide 98-3 (2008a)), namely the uncertainty based on a statistical analysis of observations and the uncertainty derived from a process equation describing physically the measurement process. Both types of measurement uncertainties are utilized 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. The measurement uncertainty models derived are analyzed through a sensitivity study and are discussed in detail resulting in an identification of the most relevant sources of measurement uncertainties. For the utilization of monitoring data in a structural reliability analysis the approach for the determination of measurement uncertainties data is applied. Monitoring data can be interpreted in two ways, namely as probabilistic loading model information and as probabilistic resistance model information, i.e. proof loading. For both ways the influence of the measurement uncertainties on the structural reliability is shown and how the specific modeling of monitoring data in a reliability analysis can result in a reduction of uncertainties and as a consequence in an increase of the reliability. The proof loading concept is developed further to account for probabilistic proof loading information, i.e. information subjected to measurement uncertainties. In conjunction with an alternative proof loading concept utilizing Bayesian updating techniques, a criterion to facilitate a consistent choice of the appropriate proof loading method is developed. The developed approaches and the findings are applied in a life-cycle cost-benefit analysis comprising the expected costs of failure, of inspection, of repair and of the monitoring system as well as its operation. Here, concepts for the design decision support of monitoring systems are introduced by formulating the life-cycle cost-benefit analysis as an optimization problem. On this basis, it can be determined which components should be monitored to achieve a life cycle benefit. Furthermore, an approach for the reduction of monitoring period is introduced. The most significant result of the cost-benefit analysis is that a substantial expected life-cycle benefit is achievable by the application of the developed concepts. KW - Structural condition assessment KW - Monitoring KW - Offshore wind turbine KW - Measurement uncertainty KW - Cost benefit analysis KW - Structural integrity management PY - 2012 DO - https://doi.org/10.3929/ethz-a-009753058 SN - 0257-6821 IS - 345 SP - 1 EP - 149 PB - vdf Hochschulverlag AG CY - Zollikon AN - OPUS4-28280 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 -