TY - JOUR A1 - Karabeliov, Krassimire A1 - Cuéllar, Pablo A1 - Baeßler, Matthias A1 - Rücker, Werner T1 - System identification of inverse, multimodal and nonlinear problems using evolutionary computing - Application to a pile structure supported on nonlinear springs N2 - This paper deals with the system identification of a mechanical structure supported by nonlinear springs subjected to an external load. If all mechanical parameters of the system were known, the displacement of the system subjected to this load could be easily calculated. However, the monitoring applications often deal with the inverse problem. The loads and displacements of the system are known and certain mechanical Parameters of the system are sought. The solution of such inverse problems can be difficult, especially when they have a nonlinear and multimodal character, which often makes them appear intractable at first sight. However, evolutionary computing can be applied to solve this inverse, nonlinear and multimodal problem. Sometimes a prior knowledge exists on certain system properties, which is difficult to implement into analytical or numerical solvers. This knowledge can play a decisive role in identifying the System properties and it can be easily included as a boundary condition when applying evolutionary algorithms. This article discusses how and under what conditions the unknown spring resistances can be identified. The practical application of this procedure is exemplified here with the mechanical system of a pile foundation. KW - Evolutionary computing KW - Inverse problem KW - Multimodal solution KW - System identification KW - Pile monitoring PY - 2015 U6 - https://doi.org/10.1016/j.engstruct.2015.07.034 SN - 0141-0296 SN - 1873-7323 VL - 101 SP - 609 EP - 620 AN - OPUS4-39310 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Baeßler, Matthias A1 - Cuéllar, Pablo A1 - Victor, A. A1 - Lüddecke, F. ED - Triantafyllidis, T. T1 - Stability and large deformations of slender structures supported by soil materials N2 - The stability and geometric nonlinearities of slender structures are a major topic in structural design. While this topic is most relevant in the field of Structural Engineering, e.g. for steel or concrete structures, only few applications take the role of soil-structure-interaction explicitly into account. The focus of this paper is placed on the impact of soil support and its modelling for the buckling analysis based on examples both for pile foundations and for railway track stability. The general interaction between steel design and the geotechnical input will be addressed. The paper discusses and summarizes a range of subtopics based on experience and current research at the author’s institute. KW - Buckling soil-structure-interaction offshore piles track PY - 2020 SN - 978-3-030-28515-9 SN - 978-3-030-28516-6 U6 - https://doi.org/10.1007/978-3-030-28516-6 SN - 1613-7736 SN - 1860-0816 VL - 91 SP - 355 EP - 369 PB - Springer CY - Cham, Switzerland AN - OPUS4-49166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo A1 - Baeßler, Matthias A1 - Rücker, Werner T1 - Relevant factors for the liquefaction susceptibility of cyclically loaded offshore monopiles in sand N2 - The offshore foundations may exhibit a relatively high liquefaction susceptibility due to the full saturation of the porous seabed and the cyclic nature of the typical offshore loads. Here, the particular relevance of some of the main factors that affect the liquefaction susceptibility of an offshore monopile will be addressed, focusing on the possibility of a progressive accumulation of residual pore water pressure within the saturated soil around a monopile under cyclic lateral loading. The discussion is based on numerical results obtained with a coupled FE model of the offshore foundation which includes the Biot-Zienkiewicz u-p model. A constitutive model of the Generalized Plasticity type has been used for the soil in order to reproduce important features of its behaviour under cyclic loading. This paper presents the findings derived from a parametric study of the problem and shows that the accumulation of residual pore pressure can produce significant changes of the pile's behaviour under external loading. The paper also investigates the effects caused by the loading from a realistic storm of moderate magnitude and the consequential transient degradation of the foundation's stiffness. T2 - Poromechanics V - 5th Biot conference on poromechanics CY - Vienna, Austria DA - 2013-07-10 KW - Soil liquefaction KW - Cyclic loads KW - Piles KW - Sand (hydraulic) KW - Offshore structures PY - 2013 SN - 978-0-7844-1299-2 U6 - https://doi.org/10.1061/9780784412992.160 SP - 1336 EP - 1345 AN - OPUS4-28873 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cuéllar, Pablo A1 - Baeßler, Matthias A1 - Rücker, Werner T1 - Ratcheting convective cells of sand grains around offshore piles under cyclic lateral loads N2 - Sand densification around the pile has traditionally been regarded as an explanation for the grain migration and soil subsidence that often occur around cyclic laterally loaded piles embedded in sand. Supported by new empirical evidence, this paper proposes that, additionally to some soil densification around the pile, the main cause for the continuous "steady-state" grain migration is a convective cell flow of sand grains in the vicinities of the pile head. Such convective flow would be caused by a ratcheting mechanism triggered by the cyclic low-frequency lateral displacements of the pile. Furthermore, the experimental results suggest that the limit between the convective cell and the static soil is marked by a distinct direct shear surface. This might shed some light into the complex phenomena related to the pile-soil interaction in the upper layers of the bedding, which are normally the main contributor for the lateral load-bearing capacity of piles. KW - Grain migration KW - Pile foundation KW - Cyclic lateral load KW - Ratcheting KW - Convection KW - Densification PY - 2009 U6 - https://doi.org/10.1007/s10035-009-0153-3 SN - 1434-5021 SN - 1434-7636 SP - 1 EP - 12(?) PB - Springer CY - Berlin ; Heidelberg AN - OPUS4-20104 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cuéllar, Pablo A1 - Baeßler, Matthias A1 - Georgi, Steven A1 - Rücker, Werner T1 - Porenwasserdruckaufbau und Bodenentfestigung um Pfahlgründungen von Offshore-Windenergieanlagen N2 - Die Gründung von Offshore-Windenergieanlagen erfordert oft die Installation von Stahl-Pfählen mit großem Durchmesser, entweder als Monopile- oder Mehrpfahl-Konfiguration (Jacket, Tripod, usw.). In dieser Veröffentlichung werden die Auswirkungen einer zyklischen lateralen Belastung auf Offshore-Pfahlgründungen untersucht. Hierbei wird besonderes Augenmerk auf die Entwicklung des Porenwasserdrucks im umgebenden gesättigten Boden gelegt. Es wird gezeigt, dass der progressive Aufbau von Porenwasserdruck zu erheblichen Veränderungen des Verhaltens der Gründung unter externer Belastung führen kann, die die Stabilität bzw. Gebrauchstauglichkeit der Anlage potenziell gefährden. Dazu werden auch einige Effekte, die während eines realistischen Sturms von moderater Stärke entstehen, untersucht. Die transiente Abminderung der Gründungssteifigkeit wird hierbei thematisiert. Die genannten Aspekte wurden von den Autoren mittels eines gekoppelten zweiphasigen numerischen Modells der Offshore-Gründung untersucht. Das verwendete Stoffgesetz für den Boden, im Rahmen der Theorie der verallgemeinerten Plastizität, kann wichtige Merkmale von zyklischem Bodenverhalten reproduzieren, wie z. B. die Tendenz zu einer fortschreitenden Verdichtung unter zyklischer Belastung, die für Verflüssigungsphänomene unter undränierten Bedingungen verantwortlich ist. Die Notwendigkeit der Verwendung eines solchen Ansatzes wird hier anhand von Vergleichsberechnungen mit einem einfacheren Stoffmodell bzw. mit einem ungekoppelten Modell erörtet. Abschließend werden einige Implikationen der untersuchten Fragenstellungen für die praktische Bemessung von Offshore-Monopiles diskutiert und spezifische Empfehlungen gegeben.--------------------------------------------------------------------------------------------------------------------------- For the installation of wind turbines in the offshore environment and their foundation in the seabed it is customary to employ large-diameter steel piles, either in monopile or multi-pile configurations (jacket, tripod, etc. ...). The effects of cyclic lateral loading on the offshore piles and particularly the possibility of a progressive accumulation of residual pore water pressure within the saturated embedding soil are discussed in this article. Here it is shown that this can lead to significant changes of their behaviour under external loading, which can potentially compromise the foundation's stability or serviceability. Furthermore, some of the singular effects arising during a realistic storm of moderate magnitude as well as their potential for transient damages to the foundation's stiffness are addressed in the paper. For the investigation of these phenomena the authors have employed a coupled bi-phasic analytical model of the offshore foundation. The constitutive model employed for the seabed, in the frame of the theory of Generalized Plasticity, can reproduce some complex features of cyclic soil behaviour such as the tendency for a progressive densification under cyclic loading, which is responsible for the soil liquefaction phenomena in undrained conditions. Finally, some implications and specific recommendations for the design of offshore monopiles in the frame of the limit states are provided. KW - Porenwasserdruckaufbau KW - Offshore-Pfahlgründung KW - Belastung KW - Zyklische KW - Pore pressure build-up KW - Offshore pile foundation KW - Cyclic loading PY - 2012 U6 - https://doi.org/10.1002/bate.201200031 SN - 0932-8351 SN - 1437-0999 SN - 0005-6820 SN - 0341-1052 SN - 0932-6359 SN - 0932-8351 VL - 89 IS - 9 SP - 585 EP - 593 PB - Ernst & Sohn CY - Berlin AN - OPUS4-26981 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo A1 - Baeßler, Matthias A1 - Rücker, Werner T1 - Pore-pressure accumulation and soil softening around pile foundations for offshore wind turbines T2 - OMAE 2012 - 31st International conference on ocean, offshore and artic engineering CY - Rio de Janeiro, Brazil DA - 2012-07-01 KW - Offshore pile foundation KW - Cyclic loading KW - Coupled numerical modelling KW - Pore-pressure accumulation KW - Softening KW - Liquefaction PY - 2012 SN - 978-0-7918-4491-5 VL - 4 SP - 219 EP - 228 PB - ASME CY - New York, N.Y. AN - OPUS4-26738 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cuéllar, Pablo A1 - Georgi, Steven A1 - Baeßler, Matthias A1 - Rücker, Werner T1 - On the quasi-static granular convective flow and sand densification around pile foundations under cyclic lateral loading N2 - The saturated sand surrounding an offshore pile foundation under quasi-static cyclic lateral load can show the physical phenomena of macromechanical densification and convective granular flow. Based on the results from physical model tests at different geometrical scales, this paper provides a certain quantification of such phenomena and discusses their causes and consequences. The progressive sand densification leads to subsidence of the soil surface and a significant stiffening of the pile behaviour. Conversely, the ratcheting convective motion of two closed cells of soil beneath the pile-head is responsible for an endless grain migration at the soil surface, the inverse grading of the convected material and a direct shear of the sand at the distinct boundary of the revolving soil domain. In this respect, and from a macromechanical perspective considering the soil as a continuum, it appears that the convecting material tends to follow gradient lines of shear stress during its ratcheting motion. Concluding the paper, the practical relevance of these phenomena and their extrapolation to other conditions are briefly discussed. KW - Offshore pile foundation KW - Cyclic loading KW - Ratcheting KW - Granular convection KW - Densification PY - 2012 U6 - https://doi.org/10.1007/s10035-011-0305-0 SN - 1434-5021 SN - 1434-7636 VL - 14 IS - 1 SP - 11 EP - 25 PB - Springer CY - Berlin ; Heidelberg AN - OPUS4-25405 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bronsert, Jeffrey A1 - Baeßler, Matthias A1 - Cuéllar, Pablo A1 - Rücker, Werner ED - Dimitrovová, Z. ED - de Almeida, J.R. ED - Goncalves, R. T1 - Numerical modeling of train-track-interaction at bridge transition zones considering the long-term behaviour T2 - ICOVP-2013 - 11th International conference on vibration problems CY - Lisbon, Portugal DA - 2013-09-09 KW - Train-track-interaction KW - Transition zone KW - Track settlement PY - 2013 SN - 978-989-96264-4-7 SP - 1 EP - 10(?) AN - OPUS4-29591 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 - 37th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2018) CY - Madrid, Spain DA - 18.06.2018 KW - Offshore pile foundation KW - Compaction grouting KW - Material Point Method (MPM) KW - Mixed formulation KW - Digital Image Correlation (DIC) PY - 2018 SN - 978-0-7918-5130-2 SN - 2153-4772 VL - 9 SP - V009T10A013, 1 EP - 9 AN - OPUS4-46004 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Baeßler, Matthias A1 - Rücker, Werner A1 - Cuéllar, Pablo A1 - Georgi, Steven A1 - Karabeliov, Krassimire T1 - Großmaßstäblicher Versuchsstand für zyklisch axial belastete Pfähle N2 - Offshore-Pfähle in Mehrpfahlgründungsstrukturen wie Jacket-Gründungen müssen nach der Rammung überwiegend zyklisch axialen Belastungen widerstehen. Die Abmessungen der Pfähle werden sowohl von der inneren Tragfähigkeit und dem Ermüdungsverhalten des Stahlquerschnittes als auch von der äußeren Tragfähigkeit und der Pfahl-Boden-Interaktion bestimmt. Aufgrund der großen Zahl von Pfahlgründungen, die für aktuelle und zukünftige Windparkprojekte benötigt werden, besteht ein dringender Bedarf, die Dimensionierung und die damit verbundenen Kosten des Einzelpfahles zu optimieren. Bezüglich der Pfahltragfähigkeit sind wichtige aktuelle Forschungsthemen eine mögliche Traglaststeigerung durch Anwachsen und die geeignete Abschätzung der zyklischen Degradation. Zur Untersuchung beider Effekte wurde eine großmaßstäbliche Versuchsanlage auf dem Testgelände BAM TTS in Horstwalde nahe Berlin errichtet. Auf diesem Versuchsfeld können große Stahlrohrammpfähle zyklisch druck- und zugbelastet werden. Zudem kann die Untersuchung von Alterungseffekten durch zeitlichen Versatz zwischen den Messkampagnen untersucht werden. Erste Ergebnisse zeigen einen Anstieg der Pfahltragfähigkeit bis zu ca. 60 % nach einer Standzeit von ca. 18 Monaten. Für die Degradation der Tragfähigkeit der zyklisch belasteten Pfähle zeigen die ersten vorläufigen Ergebnisse ein zum Teil unerwartetes Verhalten. Zusätzliche Untersuchungen werden derzeit zur weiteren Abklärung durchgeführt. KW - Stahlpfahl, gerammt KW - Offshore-Gründung KW - Anwachsen KW - Feldversuch KW - Tragfähigkeit KW - Rammung KW - Offshore foundation KW - Increase KW - Field test KW - Bearing capacitiy KW - Driving Versuche - Experimental set-ups KW - Berechnungs- und Bemessungsverfahren - Analysis and calculation KW - Stahlhochbau - Steel buildings KW - Mast- und Turmbau - Masts and towers KW - Stahlwasserbau - Steel structures for hydraulic engineering KW - Steel pile, driven in PY - 2014 U6 - https://doi.org/10.1002/stab.201430005 SN - 0038-9145 SN - 1437-1049 SN - 0932-6375 VL - 83 IS - Suppl. 1 (Erneuerbare Energien) SP - 26 EP - 32 PB - Ernst CY - Berlin AN - OPUS4-30898 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -