TY - CONF A1 - Ratkovac, Mirjana A1 - Gerards-Wünsche, Paul A1 - Thiele, Marc A1 - Brackrock, Daniel A1 - Stamm, Michael 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 (FatDes 2023) CY - Senlis, France DA - 29.11.2023 KW - Fatigue KW - Welded KW - NDT KW - Crack growth PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600238 DO - https://doi.org/10.1016/j.prostr.2024.03.062 VL - 57 SP - 560 EP - 568 PB - Elsevier B.V. AN - OPUS4-60023 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mendler, A. A1 - Döhler, M. A1 - Hille, Falk T1 - Detecting changes in boundary conditions based on sensitivity-based statistical tests N2 - Structural health monitoring is a promising technology to automatically detect structural changes based on permanently installed sensors. Vibration-based methods that evaluate the global system response to ambient excitation are suited to diagnose changes in boundary conditions, i.e., changes in member prestress or imposed displacements. In this paper, these changes are evaluated based on sensitivity-based statistical tests, which are capable of detecting and localizing parametric structural changes. The main contribution is the analytical calculation of sensitivity vectors for changes in boundary conditions (i.e., changes in prestress or support conditions) based on stress stiffening, and the combination with a numerically efficient algorithm, i.e., Nelson’s method. One of the main advantages of the employed damage diagnosis algorithm is that, although it uses physical models for damage detection, it considers the uncertainty in the data-driven features, which enables a reliabilitybased approach to determine the probability of detection. Moreover, the algorithm can be trained and the probability of detecting future damages can be predicted based on data and a model from the undamaged structure, in an unsupervised learning mode, making it particularly relevant for unique structures, where no data from the damaged state is available. For proof of concept, a numerical case study is presented. The study assesses the loss of prestress in a two-span reinforced concrete beam and showcases suitable validation approaches for the sensitivity calculation. T2 - International Symposium on Non-Destructive Testing in Civil Engineering (NDT-CE 2022) CY - Zurich, Switzerland DA - 16.08.2022 KW - Nelson’s method KW - Global ambient vibrations KW - Asymptotic local approach KW - Sensitivity vectors KW - Probability of detection KW - Stress stiffening PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-566632 DO - https://doi.org/10.58286/27311 SN - 1435-4934 VL - 27 IS - 9 SP - 1 EP - 13 PB - NDT.net CY - Kirchwald AN - OPUS4-56663 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eichner, Lukas T1 - Design of offshore jacket support structure for experimental fatigue life evaluation N2 - One crucial metric of interest to wind farm operators is the remaining useful life (RUL) of single components, wind turbines, or even entire wind farms. Occasionally, questions arise regarding how to operate a turbine, even in the presence of manufacturing or design errors, which from a computational design standpoint reduce the remaining lifetime below the intended service life. A typical measure involves adapting the monitoring and inspection plan. Using such a maintenance plan, the author intends to simulate the lifetime of jacket-type structure in a fatigue test. The objective of the experiment is to demostrate that systems like three-dimensional jackets possess redundancies that enable reliable continued operation, despite the reduced fatigue life of individual components due to technical flaws, if an appropriate maintenance concept is in place. This presentation discusses the steps leading to the procedure of the experiment including the design process and the maintenance planning. T2 - 19th eawe PhD Seminar CY - Hannover, Germany DA - 06.09.2023 KW - Offshore wind energy KW - Jacket support structure KW - Simulation and experiment KW - Structural integrity management KW - Risk-based maintenance planning PY - 2023 AN - OPUS4-58240 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Design challenges for Offshore wind-farms. From foundation mechanics to wind-farm aerodynamics N2 - This talk provides a brief introduction on general engineering design challenges for the offshore wind energy production. Some general features of the offshore wind-energy field from a civil engineering perspective are firstly presented, followed by a brief discussion of some of the main geomechanical issues for the foundation of the offshore turbines into the seabed. In the following part, an overview of relevant fluid-structure interactions and some options for an efficient numerical analysis are provided, where the hydromechanical Wave–Tower interaction is firstly discussed. Then, some general aspects of the windfarm aerodynamics are introduced. On the one hand, some modelling possibilities for the wake analysis of single turbines and turbine groups are discussed. And on the other hand the relevance of such analyses for a proper windfarm layout optimization is pointed out. In particular, this talk shows that: i) The bearing capacity of turbine multi-pile foundations can degrade under cyclic loading (waves, wind, …), while for monopile foundations cyclic hydromechanical coupling effects may take place, which may lead to a foundation softening; ii) Numerical analysis of a turbine’s interaction with wind/waves is useful and affordable, while simplified models can already provide a useful insight into the windfarm aerodynamics. iii) Turbulent wake analysis is very relevant for the windfarm layout. T2 - Colloquium "Energy systems compared", Winter semester 20/21, Faculty of Physics CY - Online meeting DA - 21.01.2021 KW - Offshore wind energy KW - Marine geotechnics KW - Fluid-structure interaction KW - Numerical modelling PY - 2021 AN - OPUS4-52038 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Design challenges for Offshore wind-farms. From foundation mechanics to wind-farm aerodynamics N2 - This talk provides a brief introduction on general engineering design challenges for the offshore wind energy production. Some general features of the offshore wind-energy field from a civil engineering perspective are firstly presented, followed by a brief discussion of some of the main geomechanical issues for the foundation of the offshore turbines into the seabed. In the following part, an overview of relevant fluid-structure interactions and some options for an efficient numerical analysis are provided, where the hydromechanical Wave–Tower interaction is firstly discussed. Then, some general aspects of the windfarm aerodynamics are introduced. On the one hand, some modelling possibilities for the wake analysis of single turbines and turbine groups are discussed. And on the other hand the relevance of such analyses for a proper windfarm layout optimization is pointed out. In particular, this talk shows that: i) The performance and behavior of the turbine's foundation is often conditioned by the appearance of large deformations, fluid couplings and grain-scale phenomena, whereby specific physical testing (both in field and lab conditions) and ad-hoc simulation techniques can provide useful insights for design; ii) Numerical analysis of a turbine’s interaction with wind/waves is already affordable in engineering scales, while simplified models can already provide a useful insight into the windfarm aerodynamics. iii) Turbulent wake analysis is very relevant for the windfarm layout. T2 - Colloquium "Energy systems compared", Winter semester 22/23, Faculty of Physics CY - Duisburg, Germany DA - 24.01.2023 KW - Offshore wind-turbine foundations KW - Water-structure interaction KW - Wind-farm aerodynamics PY - 2023 AN - OPUS4-56888 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gerards-Wünsche, Paul T1 - Der Weg vom Labor zur industriellen Einsetzbarkeit der Risslumineszenz N2 - Der Vortrag beschreibt die Relevanz der Zuverlässigkeitsbewertung von klassischen ZfP- und SHM-Verfahren. Diese Zuverlässigkeitsbewertung soll auch für das an der BAM entwickelte Risslumineszenzverfahren durchgeführt werden. Die Risslumineszenz wird zunächst vorgestellt und es wird beschrieben welchen Weg man beschreiten muss, um eine Zuverlässigkeitsbewertung für eine Technik durchzuführen, die nicht nur als ZfP-Verfahren genutzt werden soll, sondern auch für die Dauerüberwachung unter der Einbindung einer KI-basierten automatisierten Risserkennung. Die mit dieser Erweiterung des Einsatzspektrums einhergehenden Faktoren für Messunsicherheit und -variabilität wird als Problematik erkannt und als zukünftige Aufgabe, die es zu lösen gilt, definiert. T2 - ZfP-Seminar Prof. Große TU München WS22 CY - Online meeting DA - 15.12.2022 KW - Rissprozes KW - Structural Health Monitoring KW - Risslumineszenz KW - Ermüdungsprüfung KW - Rissprozess PY - 2022 AN - OPUS4-56643 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines. Part 2: Lateral behaviour and Advanced topics T1 - Cimentaciones profundas para aerogeneradores marinos. Parte 2: Comportamiento lateral y temas avanzados N2 - his presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures. The second lecture continues with the case of laterally loaded offshore piles, which bears most relevance for the case of the monopile foundations. Here again, a clear separation between physical reality and design methods is intended. Finally, the last part of the second lecture introduces several advanced topics which lie outside the classical design approaches, namely the hydromechanical coupling effects (i.e. the excess pore-pressure generation around the monopiles), the cyclic pile fatigue and the so-called pile setup (i.e. the time effects on the axial pile capacity). The relevance of the latter two topics is illustrated with experimental results from a field testing campaign on real large-scale piles. T2 - CEDEX-UNED 2021 Master course on Soil Mechanics and Geotechnical Engineering CY - Online meeting DA - 24.03.2021 KW - Offshore wind energy KW - Deep foundations KW - Offshore geomechanics KW - Lateral load bearing KW - Cyclic degradation KW - Pile ageing PY - 2021 AN - OPUS4-52342 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines. Part 1: Axial behaviour T1 - Cimentaciones profundas para aerogeneradores marinos. Parte 1: Comportamiento axial N2 - This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures. The first lecture presents a brief introduction to the context and peculiarities of such foundations, and then focuses on the particular case of axially loaded piles. This part is most relevant for the relatively slender piles of the multi-pile substructures (i.e. jackets and tripods). A clear distinction between physical phenomenology and practical design is drawn here. T2 - CEDEX-UNED 2021 Master course on Soil Mechanics and Geotechnical Engineering CY - Online meeting DA - 24.03.2021 KW - Offshore wind energy KW - Deep foundations KW - Offshore geomechanics KW - Axial load bearing KW - Design models PY - 2021 AN - OPUS4-52341 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines. Lecture 2: lateral behaviour and advanced topics T1 - Cimentaciones profundas para aerogeneradores marinos - Parte 2: Comportamiento lateral y tematica avanzada N2 - This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures. The second lecture continues with the case of lateraly loaded offshore piles, which bears most relevance for the case of the monopile foundations. Here again, a clear separation between physical reality and design methods is intended. Finally, the last part of the second lecture introduces several advanced topics which lie outside the classical design approaches, namely the hydromechanical coupling effects (i.e. the excess pore-pressure generation around the monopiles), the cyclic pile fatigue and the so-called pile setup (i.e. the time effects on the axial pile capacity). The relevance of the latter two topics is illustrated with experimental results from a field testing campaign on real large-scale piles. T2 - Masters course on Soil Mechanics and Geotechnical Engineering. Geotechnical Laboratory of CEDEX CY - Online meeting DA - 21.04.2020 KW - Pile foundations KW - Offshore wind turbines KW - Physical phenomenology KW - Design methods PY - 2020 AN - OPUS4-51059 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines. Lecture 1: Axial behaviour T1 - Cimentaciones profundas para aerogeneradores marinos - Parte 1: Comportamiento axial N2 - This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures. The first lecture presents a brief introduction to the context and peculiarities of such foundations, and then focuses on the particular case of axially loaded piles. This part is most relevant for the relatively slender piles of the multi-pile substructures (i.e. jackets and tripods). A clear distinction between physical phenomenology and practical design is drawn here. T2 - Masters course on Soil Mechanics and Geotechnical Engineering. Geotechnical Laboratory of CEDEX CY - Online meeting DA - 21.04.2020 KW - Pile foundations KW - Offshore wind turbines KW - Physical phenomenology KW - Design methods PY - 2020 AN - OPUS4-51057 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -