TY - CONF A1 - Cuéllar, Pablo A1 - Baeßler, Matthias T1 - Design challenges for offshore wind-farms. From foundation mechanics to wind-farm aerodynamics N2 - This talk provides a brief introduction on general engineering aspects of offshore wind energy production. Then some geomechanical issues for the foundation of OWTs into the seabed are introduced, while the results from experimental investigations and coupled computational analysis are discussed. In the second part of the seminar, 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. Concerning the geomechanical issues the talk shows that: i) The pile’s bearing capacity can degrade under cyclic loading (waves, wind, …). ii) The time effects can be relevant: Capacity improvement can be substantial, but also fragile. iii) There are cyclic PWP effects: Cyclic interaction with pore water may lead to soil softening and an uncoupled analysis (current design practice) is potentially unsafe. And concerning the hydromechanical and aerodynamical design considerations, this seminar shows that: i) Numerical analysis of turbine’s interaction with wind/waves is useful and affordable. ii) Simplified models can provide insight into windfarm aerodynamics. iii) Turbulent wake analysis is very relevant for the windfarm layout. T2 - Energy Science Kolloquium CY - Fakultät für Physik, Universität Duisburg-Essen, Germany DA - 25.01.2018 KW - Offshore wind farms KW - Geomechanics KW - Design PY - 2018 AN - OPUS4-43958 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines T1 - Cimentaciones profundas para aerogeneradores marinos N2 - This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided in 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. 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 cyclic pile fatigue and the so-called pile setup (i.e. the time effects on the axial pile capacity). The relevance of these 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 2018, Geotechnical Laboratory of CEDEX CY - Madrid, Spain DA - 13.04.2018 KW - Pile foundations KW - Offshore wind energy KW - Physical phenomenology KW - Design practice PY - 2018 AN - OPUS4-44764 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Geißler, Peter A1 - Cuéllar, Pablo A1 - Hüsken, Götz A1 - Kühne, Hans-Carsten A1 - Baeßler, Matthias T1 - Insights into compaction grouting for offshore pile foundations N2 - The authors are currently investigating the possibility to apply compaction grouting for offshore pile foundations (Jacket piles as well as monopiles) as a possible retrofitting technique for an optimised foundation concept. In this research project, we are developing a design approach aiming to predict the ideal amount and properties of a grout for a specific soil situation and desired improvement of pile bearing capacity after Installation and during service time. Both numerical and experimental tests have been carried out to investigate the injection process during which a highly viscous grout is injected into the soil under high pressure to displace and compact the surrounding soil without fracturing it. The implicit Material Point Method (MPM) based on a mixed formulation is the numerical technique chosen to deal with the expected large deformations and the arbitrary shape of the developing grout bulb. The usage of MPM prevents both the need of remeshing and the numerical instability induced by extensive mesh distortion. For validation with experimental results, we have constructed a testing chamber with one transparent sidewall. This chamber enables us to observe the injection process directly at the transparent vertical window and to measure the in-plane soil displacements and strains by means of the Digital Image Correlation (DIC) technique. The results already reveal the interrelation of soil and grout properties for a successful usage of this common ground improvement technique. T2 - ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2018) CY - Madrid, Spain DA - 17.06.2018 KW - Offshore Pile Foundation KW - Compaction Grouting KW - Material Point Method KW - Digital Image Correlation PY - 2018 AN - OPUS4-45352 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Auersch, Lutz A1 - Said, Samir T1 - Strukturschwingungen und Schwingungsminderung – Bauwerksmodelle, Messungen vor Ort und auf dem Versuchsgelände der BAM N2 - Die Grundidee einer Schwingungsminderung ist es eine tiefe Eigenfrequenz der Struktur zu erreichen, so dass höhere Frequenzen abgemindert werden. Das gilt für die Minderung an der Quelle, zum Beispiel einem Eisenbahngleis, und für die Minderung am Empfänger, dem Gebäude. Die Eigenfrequenz ermittelt man aus dem Verhältnis der Auflagersteifigkeit und der Masse. Wie ist die Masse bei einem Gebäude zu wählen? Und wie ist die Untergrund-steifigkeit zu berücksichtigen? Als Referenzsituation ohne Minderungsma߬nahme? Der Beitrag bringt Rechenergebnisse zu abgefederten Gebäuden mit einfachen und komplexen (FE-) Modellen, Mess- und Rechenergebnisse zur Schwingungsübertragung von unabge-federten Gebäuden. Es wird der Einfluss der Abstimmfrequenz, der Bodensteifigkeit und der „starren“ Gebäudemasse untersucht. Die komplexen Gebäudemodelle erlauben, neben der Berechnung einer elastischen Gebäudelagerung, auch die Variation von Gebäudepara¬metern zur Reduktion der Deckenschwingungen. Den Ergebnissen bei der Erschütterungs-übertragung in Gebäude werden zwei ähnliche Beispiele zur elastischen Maschinenlagerung und zur elastischen Gleislagerung gegenübergestellt. T2 - 6. VDI-Fachtagung Baudynamik CY - Würzburg, Germany DA - 17.04.2018 KW - Elastische Gebäudelagerung KW - Rechenmodelle PY - 2018 AN - OPUS4-45472 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Said, Samir A1 - Auersch, Lutz T1 - Prediction of explosion-induced ground and building vibrations - measured wave velocities, transfer functions and attenuation N2 - Explosion-induced ground vibrations have been measured at several places. Results about the wave propagation are shown in this contribution. The particle velocities of the soil have been measured at up to 1000 m distance from the explosion and are presented as time records (seismograms) and one-third octave band spectra (transfer functions). The results are compared with the results of hammer impacts. The seismograms clearly show different wave types, compressional waves of the air, the water and the soil, and the Rayleigh wave. The hammer impacts yield good results up to 100 m and incorporate higher frequencies at about 50 Hz, whereas the explosion results in a ground vibration with frequencies around 10 Hz and a longer range of influence. Explosion and hammer excitations are evaluated for the wave velocities of the soil by using the wavenumber and the spatial auto-correlation method. The attenuation of the ground vibration amplitudes A with distance r can well be presented by a power law A ~ r -q. This type of amplitude-distance law and the corresponding power q > 1 are substantiated in the contribution. The influence of the charge weight W is evaluated as an additional power law A ~ W -p for each measuring site. The power is found quite similarly around q  0.6 as all sites have a medium soft soil such as sand and clay. The obtained amplitude-charge-distance law can be used to predict the explosion-induced ground and building vibrations at other sites. T2 - International Congress on Sound and Vibration (ICSV25) CY - Hiroshima, Japan DA - 08.07.2018 KW - Soil properties KW - Amplitude-charge weight laws KW - Amplitude-distance laws KW - Explosion-induced ground vibrations KW - Hammer impact KW - Prediction of explosion induced ground and building vibration PY - 2018 AN - OPUS4-45508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Shamsuddoha, Md A1 - Hüsken, Götz A1 - Pirskawetz, Stephan A1 - Baeßler, Matthias A1 - Kühne, Hans-Carsten A1 - Thiele, Marc T1 - Remediation of Cracks Formed in Grouted Connections of Offshore Energy Structures under Static Loads N2 - The future energy demand necessitates the exploration of all potential energy sources both onshore and offshore. Global trend has shifted towards offshore energy, which can be obtained from either carbon intensive or renewable options, hence requiring structures such as rigs, platforms, and monopiles. Most of these structures adopt easily installable construction techniques, where lower foundation need to be connected with the super structure by mean of grouted composite joints. Generally, these composite connections have exterior sleeve, interior pile and infill grout. Being located in remote offshore conditions, connections can experience considerable adverse loading during their lifetimes. Degradations were reported inside similar connections, which were installed in last three decades. Besides, grouting in the offshore sites may often be proven difficult, which eventually leads to reduced capacity of connections in the long run. Thus, repair and rehabilitation of such connections should be planned ahead to minimize operational delays and costs in the future. This study aims at characterizing the nature of crack generation in grouted connections and thereby identifying the potential of repair using suitable repair material. Scaled grouted joints were manufactured using a novel mold, and connections were loaded under static load to visualize the main failure pattern. The failure mechanism and loading capacity are found compatible to previous results from earlier literature. Grouted connection was then repaired using cementitious injectable grout. The effectiveness of the repair system is also discussed. T2 - Twenty-eighth (2018) International Ocean and Polar Engineering Conference CY - Sapporo, Japan DA - 10.06.218 KW - Offshore KW - Energy KW - Grouted Connection KW - Cracks KW - Repair KW - Rehabilitation PY - 2018 AN - OPUS4-45226 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baeßler, Matthias T1 - Aktivitäten der BAM zu Offshore-Windenergie N2 - Die BAM ist in vielen Bereich zum Thema Ausbau Windenergie, insbesondere für den Offshore-Bereich aktiv. Die Aktivitäten werden exemplarisch für die Tätigkeiten im Bereich FE, PAZ und BI dargestellt. Anlass war eine Zusammenkunft mit dem Verband der Betreiber (AGOW) T2 - Erfahrungsaustausch AGOW-BAM CY - BAM, Berlin, Germany DA - 24.01.2018 KW - Offshore-Wind PY - 2018 AN - OPUS4-43991 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baeßler, Matthias A1 - Zobel, D. A1 - Cuéllar, Pablo A1 - Geißler, Peter A1 - Hüsken, Götz A1 - Grabe, J. T1 - Improvement of the Bearing Capacity of Offshore Pile Foundations N2 - The Presentation gives an overview about Background, Needs and challenges with respect to pile design and modular pile capacity increase in the Frame of Offshore-Wind Foundations. Results and ideas of the Project TOP are presented. The presentation is prepared jointly by TUHH and BAM. T2 - Offshore Wind R&D Conference 2018 CY - Bremerhaven, Germany DA - 14.11.2018 KW - Grout Injection KW - Pile Capacity KW - TOP PY - 2018 AN - OPUS4-46626 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Benseghier, Z. A1 - Cuéllar, Pablo A1 - Luu, L.-H. A1 - Bonelli, S. A1 - Philippe, P. T1 - Parallel LBM-DEM simulation of fluid flow erosion using GPU N2 - Surface erosion of a cohesive granular soil by a fluid flow is investigated numerically by coupling the Lattice Boltzmann Method (LBM) for the fluid phase and the Discrete Element Method (DEM) for describing the motion of the solid particles. In addition, inter-particles cohesion is insured by a contact model featuring a paraboloidal yield surface. The use of a fully resolved LBM-DEM coupling technique is currently limited due to the computational cost when simulating a large number of particles. This issue can be overcome using the graphics processing unit (GPU) thanks to ist massively parallel hardware architecture. Here, we first present a 2D GPU implementation of LBM-DEM coupling for a granular assembly. The GPU implementations are approximatively 30 times faster than a single core CPU version. Then, we apply the parallelization technique to practical erosional cases, namely the jet erosion test (JET) and the shear-driven erosion by a Couette flow. These numerical tests aim to relate micro parameters of a cohesive material (eg. cohesion) to macro parameters (eg. soil erodibility, mechanical strengths). Preliminary results show that micromechanical features indeed provide a novel insight of soil erosion phenomena. T2 - CILAMCE 2018 CONGRESS CY - Paris/Compiègne, France DA - 11.11.2018 KW - Micromechanical LBM-DEM simulation KW - GPU parallelisation KW - Soil erosion PY - 2018 AN - OPUS4-46594 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kullolli, Borana T1 - A generalized plasticity model adapted for shearing interface problems N2 - The response of many geotechnical systems, whose structural behavior depends on shearing effect, is closely related to soil structure interaction phenomenon. Experimentally it is found that the localisation of these effect happens at a narrow soil layer next to the structure. Numerically, this behavior can be modelled through interface elements and adequate constitutive models. In this work, a constitutive model in the framework of Generalized Plasticity for sandy soils has been chosen to be adapted for the interface zone. From the direct shear experiments a sandy soil at loose and dense states under different normal pressures is considered. The adapted constitutive model is able to reproduce contraction and dilatation of the soil according to its relative density and it shows a good agreement with the experimental data. T2 - Numerical Geotechnics CY - Porto, Portugal DA - 25/06/2018 KW - Interface model KW - Cyclic axial shearing KW - Numerical model PY - 2018 AN - OPUS4-47068 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -