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 - 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 - GEN A1 - Farhan, Muhammad A1 - Schneider, Ronald A1 - Thöns, Sebastian T1 - Corrigendum to Predictive information and maintenance optimization based on decision theory: a case study considering a welded joint in an offshore wind turbine support structure N2 - This article has been revised and republished due to substantial changes to the text of the original article, as published Online First on January 31, 2021. Most of the change were minor grammatical changes. The following changes are more significant and will be highlighted below. KW - Integrity management KW - Decision theory KW - Value of information KW - Structural reliability KW - Fracture mechanics KW - Fatigue KW - Predictive maintenance KW - Wind turbine support structure PY - 2022 U6 - https://doi.org/10.1177/14759217211040385 SN - 1475-9217 VL - 21 IS - 4 SP - 1956 EP - 1956 PB - Sage Publications CY - London AN - OPUS4-55165 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 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-521719 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 - Farhan, Muhammad A1 - Schneider, Ronald A1 - Thöns, Sebastian T1 - Predictive information and maintenance optimization based on decision theory: a case study considering a welded joint in an offshore wind turbine support structure N2 - Predictive information and maintenance optimization for deteriorating structures is concerned with scheduling (a) the collection of information by inspection and monitoring and (b) maintenance actions such as repair, replacement, and retrofitting based on updated predictions of the future condition of the structural system. In this article, we consider the problem of jointly identifying—at the beginning of the service life—the optimal inspection time and repair strategy for a generic welded joint in a generic offshore wind turbine structure subject to fatigue. The optimization is performed based on different types of decision analyses including value of information analyses to quantify the expected service life cost encompassing inspection, repair, and fatigue damage for all relevant combinations of inspection time, repair method, and repair time. Based on the analysis of the expected service life cost, the optimal inspection time, repair method, and repair time are identified. Possible repair methods for a welded joint in an offshore environment include welding and grinding, for which detailed models are formulated and utilized to update the joint’s fatigue performance. The decision analyses reveal that an inspection should be scheduled approximately at mid-service life of the welded joint. A repair should be performed in the same year after an indication and measurement of a fatigue crack given an optimal inspection scheduling. This article concludes with a discussion on the results obtained from the decision and value of information analyses. KW - Integrity management KW - Value of information KW - Decision theory KW - Structural reliability KW - Fracture mechanics KW - Fatigue KW - Predictive maintenance KW - Wind turbine support structure PY - 2021 U6 - https://doi.org/10.1177/1475921720981833 SN - 1475-9217 SN - 1741-3168 PB - Sage Publications CY - London AN - OPUS4-52771 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schneider, Ronald A1 - Thöns, Sebastian A1 - Rogge, Andreas ED - Bucher, Christian ED - Ellingwood, Bruce R. ED - Frangopol, Dan M. T1 - Simulating the service life performance of an inspected group of jacket-type structures N2 - A novel method for risk-based optimization of inspection and repair strategies for deteriorating structural systems has recently been proposed. The method defines heuristics at the system level to reduce the number of possible strategies. For each defined strategy, it computes the updated system failure probability conditional on simulated inspection and repair histories, and evaluates the associated costs and risk. The expected total service life costs and risk for a strategy are finally determined using Monte Carlo simulation. The optimal strategy minimizes the expected total service life costs and risk. We intend to adopt this approach to optimize inspection, monitoring and repair activities for offshore wind park support structures. As a first step, we simulate – in analogy to an offshore wind park – the service life performance of an inspected group of jacket-type frames. The performance is quantified in terms of the group’s system failure probability conditional on simulated inspection and repair histories. The underlying system model accounts for the structural redundancy of the frames and the interdependence among their failure events due to similar loading conditions. The model also captures stochastic dependence among the deterioration states of the frames. As part of the simulation process the a-priori unknown outcome of any planned inspection is generated conditional on the outcome of all previous inspections. T2 - 12th International Conference on Structural Safety and Reliability CY - Vienna, Austria DA - 06.08.2017 KW - Reliability KW - Fatigue KW - Inspection KW - Service life performance KW - Inspection planning PY - 2017 SN - 978-3-903024-28-1 SP - 2738 EP - 2747 PB - TU-MV Media Verlag GmbH CY - Vienna, Austria AN - OPUS4-41344 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -