TY - CONF A1 - Eichner, Lukas T1 - LUKAS’ JACKET: A test structure for model and monitoring based lifetime management of offshore jacket support structures N2 - The goal of the experiments is to demonstrate that systems like three-dimensional jackets possess redundancies that, despite the reduced fatigue life of individual components, enable reliable operation if an appropriate maintenance concept is in place. In practice, individual potentially faulty components in the structure have been handled conservatively so far. To move away from this approach, methods and strategies in the field of life cycle management that enable economically optimal and reliable operation must be transferred from scientific research to practice. Experiments are the preferred method to establish the proof of concept. To realistically simulate the operational lifetime of a jacket structure through an experiment, cyclic loads must be applied to the structure to replicate typical fatigue processes. To ensure that the test structure is not a "disposable product" and can undergo multiple test cycles, the experimental concept includes system-level and component-level tests. The latter are conducted on removable joints. These elements at the nodes of the structure have been manufactured in multiple variations, both to potentially contain mentioned flaws and to undergo more load cycles individually than the main structure. Once the removable joint is sufficiently pre-damaged and thus the reduced remaining fatigue life is established, the element is inserted into the overall structure. The defined maintenance strategy is then implemented on the entire system. This strategy consists of structural health monitoring (SHM), inspections, and repairs. At defined intervals, cyclic loading is interrupted to apply dynamic loads. Using the installed monitoring system and coupled operational modal analysis (OMA), the modal parameters of the structure are determined, which can help identify potential system damage. Optimal sensor placement (OSP) can be determined based on a maximum value of information (VoI) across the entire pre-posterior predicted service life. For detailed investigations at the hotspots, inspections are conducted using non-destructive methods, among others. Overall global and local information about the structure's condition is gathered these methods, which are then incorporated into models describing the structure through Bayesian updating. This allows for initial system identification based on different system responses and later updating of the predicted parameters of analytical and numerical models. Utilizing the updated models, decisions regarding maintenance actions, such as further inspections or repairs, are made, which are subject to uncertainties. The probabilistic models enable a reliability- and risk-based maintenance strategy, where, for example, maximum failure rates can act as triggers for maintenance actions. These decisions are relevant for the planned duration of the simulated operational lifetime, as well as for potential lifetime extensions, which are currently of significant importance in practice. Optimizing the maintenance strategy for the operational lifetime of the structures with these methods will lead to a higher utility of the offshore wind farm. The work associated with the test structure encompasses a variety of topics (including fatigue, damage detection and identification, reliability, Bayesian updating, system identification, SHM, maintenance planning, decisions under uncertainties), which are integrated through corresponding models and methods. All these models have been and are being applied in the numerical accompaniment of the experiments. By applying them to a structure that includes the relevant locations and aspects of real-world structures, both well-functioning and suboptimal parts of the established framework will be revealed. T2 - 20th EAWE PhD Seminar on Wind Energy CY - Visby, Sweden DA - 23.09.2024 KW - Offshore Jacket Support Structure KW - Test Structure KW - Fatigue KW - Lifetime Management KW - Structural Health Monitoring PY - 2024 AN - OPUS4-61146 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiele, Marc T1 - Detection and monitoring of the fatigue crack growth on welds – Application-oriented use of NDT methods N2 - Early detection of fatigue cracks and accurate measurements of the crack growth play an important role in the maintenance and repair strategies of steel structures exposed to cyclic loads during their service life. Observation of welded connections is especially of high relevance due to their higher susceptibility to fatigue damage. The aim of this contribution was to monitor fatigue crack growth in thick welded specimens during fatigue tests as holistically as possible, by implementing multiple NDT methods simultaneously in order to record the crack initiation and propagation until the final fracture. In addition to well-known methods such as strain gauges, thermography, and ultrasound, the crack luminescence method developed at the Bundesanstalt für Materialforschung und -prüfung (BAM), which makes cracks on the surface particularly visible, was also used. For data acquisition, a first data fusion concept was developed and applied in order to synchronize the data of the different methods and to evaluate them to a large extent automatically. The resulting database can ultimately also be used to access, view, and analyze the experimental data for various NDT methods. During the conducted fatigue tests, the simultaneous measurements of the same cracking process enabled a comprehensive comparison of the methods, highlighting their individual strengths and limitations. More importantly, they showed how a synergetic combination of different NDT methods can be beneficial for implementation in large-scale fatigue testing but also in monitoring and inspection programs of in-service structures - such as the support structures of offshore wind turbines. T2 - Fatigue Design 2023 CY - Senlis, France DA - 29.11.2023 KW - Crack growth KW - Fatigue KW - NDT KW - Welded PY - 2023 AN - OPUS4-62374 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiele, Marc T1 - Fatigue crack detection methods for high-cyclic loaded steel structures and challenges in mechanical testing N2 - For the generation of renewable energy offshore wind farms play an important role. The majority of these wind generators are connected to steel foundation structures. Steady increasing power output of these wind turbines leads to new challenges as well for engineers of the related support structures. Caused by the high-cyclic loading of these structures by wind and waves fatigue plays a very important role. Besides the consideration of fatigue within the design process it is additionally an important topic and challenge to monitor the existing steel structures relating to potential fatigue cracks occurring during their lifetime. This plays a role for a fundamental understanding of mechanisms as investigated in testing but also for inspection in real structures. Since the structures of the offshore wind generators are very large and in addition partially under water effective and reliable methods for fatigue crack detection are required. This contribution will present results of recent investigations on different crack detection methods applied on high-cycle fatigue tests on small welded steel samples as well as on welded steel components. The comparison of these measurements will show what are the advantages and disadvantages of the different methods and which method is potentially more suitable for the application on real offshore wind structures. It is outlined where challenges for detection methods exist. Furthermore, in this context the resulting challenges for the execution of material testing especially caused by the increasing dimensions of wind energy converters will by exemplarily presented. T2 - EERA JP Wind & SETWind Online Annual Event 2020 CY - Online meeting DA - 14.09.2020 KW - Fatigue KW - Crack detection KW - Steel structures PY - 2020 AN - OPUS4-51356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schneider, Ronald T1 - Vibration-based system identification of a large steel box girder bridge N2 - The Bundesanstalt für Materialforschung und -prüfung (BAM) collaborates with TNO to develop a software framework for automated calibration of structural models based on monitoring data. The ultimate goal is to include such models in the asset management process of engineering structures. As a basis for developing the framework, a multi-span road bridge consisting of ten simply supported steel box girders was selected as a test case. Our group measured output-only vibration data from one box girder under ambient conditions. From the data, we determined eigenfrequencies and mode shapes. In parallel, we developed a preliminary structural model of the box girder for the purpose of predicting its modal properties. In this contribution, we provide an overview of the measurement campaign, the operational modal analysis, the structural modeling and qualitatively compare the identified with the predicted modes. As an outlook, we discuss the further steps in the calibration process and future applications of the calibrated model. T2 - XII International Conference on Structural Dynamics (EURODYN 2023) CY - Delft, Netherlands DA - 02.07.2023 KW - Bridge KW - Safety KW - Fatigue KW - Modal system identification KW - Model updating PY - 2023 AN - OPUS4-57863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -