TY - GEN A1 - Cuéllar, Pablo A1 - Pastor, M. A1 - Mira, P. A1 - Fernández-Merodo, J.A. A1 - Baeßler, Matthias A1 - Rücker, Werner ED - Benz, T. ED - Nordal, S. T1 - Numerical investigations for the pile foundation of an offshore wind turbine under transient lateral load N2 - Numerical analysis can be useful for the investigation of important aspects of offshore foundation prototypes that otherwise could hardly be studied experimentally, like the evolution of pore-water pressure around the monopile foundation of an offshore wind turbine under extreme loading. A combination of mixed pressuredisplacement formulations along with a constitutive model for sands based on the Generalized Plasticity Theory can replicate accurately the soil behaviour in saturated conditions. However, additional issues must be taken into account in order to perform numerical simulations of offshore piles. Some implications of the Babuska-Brezzi restriction, as well as considerations about the pile-soil interface and suitable solution strategies are discussed here. Due to the high cost of the transient analysis, the parallel computation offers a promising perspective, but can be complex and needs to be implemented carefully in order to avoid a performance deterioration. A brief overview on current trends and functional software is given here. T2 - 7th European conference on numerical methods in geotechnical engineering (NUMGE 2010) CY - Trondheim, Norway DA - 2010-06-02 KW - Offshore pile foundation KW - Cyclic lateral load KW - Pore pressure accumulation PY - 2010 SN - 978-0-415-59239-0 SP - 913 EP - 919 PB - Taylor & Francis AN - OPUS4-21572 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 DO - 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 - 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 DO - 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 - CONF A1 - Kullolli, Borana A1 - Cuéllar, Pablo A1 - Baeßler, Matthias T1 - On contact problem application for the local behavior of soil-pile interaction N2 - In this paper a shear test, which helps to study local behavior of the soil-pile interaction, is modelled numerically with the Finite Element Method as a 2D plane strain problem. A normal pressure on top and shear displacement on side were applied. So far, the material behavior was considered elastic for the sake of simplicity. The effect of thickness on contact elements and the presence of in plane stress has been highlighted. The purpose of the paper is to find a suitable contact element which represents more close to reality a soil-pile interaction problem under cyclic axial loading. Moreover, an insight on the presence of in-plane stress shows that it needs to be considered cautiously. T2 - ICCE2017 CY - Tirana, Albania DA - 12.10.2017 KW - Contact problem KW - Numerical modelling PY - 2017 SP - 167 EP - 174 PB - Polytechnic University of Tirana CY - Tirana, Albania AN - OPUS4-42962 LA - eng 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 - JOUR A1 - Cuéllar, Pablo A1 - Mira, P. A1 - Pastor, M. A1 - Merodo, J.A.F. A1 - Baeßler, Matthias A1 - Rücker, Werner T1 - A numerical model for the transient analysis of offshore foundations under cyclic loading N2 - A comprehensive numerical model for the analysis of offshore foundations under a general transient loading is presented here. The theoretical basis of the model lies on the Swansea formulation of Biot's equations of dynamic poroelasticity combined with a constitutive model that reproduces key aspects of cyclic soil behaviour in the frame of the theory of generalised plasticity. On the practical side, the adoption of appropriate finite element formulations may prevent the appearance of spurious numerical instabilities of the pore pressure field. In this respect, the use of a coupled enhanced-strain element is here proposed. On the other hand, the practicality of the presented model depends ultimately on its computational efficiency. Some practical recommendations concerning the solution strategies, the matrix storage/handling procedures and the parallel multi-processor computation are here provided. Finally, the performance of the model with a benchmark study case and its practical application to analyse the soil–structure interaction of an offshore monopile under a realistic transient storm loading are discussed. KW - Offshore foundations KW - Cyclic loading KW - Numerical model KW - Pore pressure accumulation KW - Liquefaction analysis PY - 2014 DO - https://doi.org/10.1016/j.compgeo.2014.02.005 SN - 0266-352x VL - 59 SP - 75 EP - 86 PB - Elsevier Ltd. CY - Barking AN - OPUS4-30490 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 DO - 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 - Karabeliov, Krassimire A1 - Baeßler, Matthias A1 - Cuéllar, Pablo A1 - Rücker, Werner T1 - A method for system identification of a structure supported by nonlinear springs using evolutionary computing N2 - A mechanical structure supported by nonlinear springs subjected to an external load is considered. If all mechanical parameters of the system were known, the displacement of the system subjected to this load could be easily calculated. If not all of the parameters are known, but the load and the displacement are measured at one location, an inverse problem exists. In the presented problem the nonlinear springs are unknown and have to be determined. At first glance a problem needs to be solved, which is underdetermined due to the number of unknown variables. 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 solver. This knowledge can play a decisive role in identifying the system properties and it can be easily included as boundary condition when applying evolutionary algorithm. This article examines how and under what conditions the spring resistances can be identified. The procedure is exemplified at a mechanical system of a pile foundation. T2 - 2nd International conference on mathematical modeling in physical sciences 2013 CY - Prague, Czech Republic DA - 01.09.2013 PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-304531 UR - http://iopscience.iop.org/1742-6596/490/1/012095/pdf/1742-6596_490_1_012095.pdf DO - https://doi.org/10.1088/1742-6596/490/1/012095 SN - 1742-6588 SN - 1742-6596 VL - 490 IS - 012095 SP - 1 EP - 4 PB - IOP Publ. CY - Bristol, UK AN - OPUS4-30453 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kullolli, Borana A1 - Stutz, H. H. A1 - Cuellar, Pablo A1 - Baeßler, Matthias A1 - Rackwitz, F. ED - Cardoso, A. S. ED - Borges, J. L. ED - Costa, P. A. ED - Gomes, A. T. ED - Marques, J. C. ED - Vieira, C. S. 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 inter-face elements and adequate constitutive models. In this work, a constitutive model in the framework of Gen-eralized 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 - Conference CY - Porto, Portugal DA - 25.06.2018 KW - Numerical modelling KW - Soil-pile interaction KW - Interface KW - Shearing PY - 2018 SN - 978-1-138-33198-3 VL - 1 SP - 97 EP - 102 PB - NUMGE CY - Porto, Portugal AN - OPUS4-45721 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 -