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Calibri 83ffff̙̙3f3fff3f3f33333f33333.kTU Delft Repositoryg uuidrepository linktitleauthorcontributorpublication yearabstract
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departmentresearch group programmeprojectcoordinates)uuid:350f908e0ad54c2d961faf4cc10d7d4eDhttp://resolver.tudelft.nl/uuid:350f908e0ad54c2d961faf4cc10d7d4e?A 3D Glacial Isostatic Adjustment model for Northwestern Europe6van Casteren, Rosalie (TU Delft Aerospace Engineering)Zvan der Wal, Wouter (mentor); Delft University of Technology (degree granting institution)The Earth is subjected to 100,000 year cycles of glaciation and deglaciation. The deformations induced by glacial and oceanic loading and the continuous attempt at recovery of the isostatic equilibrium within the solid Earth, are referred to as Glacial Isostatic Adjustment (GIA). This process is ongoing still and yields a large contribution to present day surface deformation and sea level change in formerly glaciated areas. In order to accurately model GIA, the lateral viscosity variations within the interior of the Earth are accounted for (Kaufmann et al., 2000; Steffen et al., 2006; Wu and van der Wal, 2003). Additionally, an increased level of accuracy is obtained by adopting a combination of linear and nonlinear viscoelasticity as demonstrated by Barnhoorn et al. (2011); Forno and Gasperini (2007); van der Wal et al. (2013);Wu and Wang (2008).<br/><br/>During the Last Glacial Maximum, the BritishIrish and Fennoscandian Ice Sheets covered large parts of Northwestern Europe. The interior of the Earth in this area is known to consist of material of very heterogeneous tectonic origin (Artemieva et al., 2006). Additionally, research in this area is promoted by the availability of the independent regional ice model Bradley2018 (Bradley, personal communication), an RSL observation database for the RhineMeuse Delta (Hijma and Cohen, 2019), and a collection of GPS derived uplift rates throughout Europe (Teferle, personal communication).<br/><br/>At the Astrodynamics and Space Missions research group of Delft University of Technology, a 3D GIA FEM model has been developed to model GIA in Antarctica (Blank et al., 2017). This model follows the work by Wu (2004) and van der Wal et al. (2013), and is complemented with an iterative algorithm to solve the sea level equation in accordance with Kendall et al. (2005). This research aims to provide a single GIA model best suited for the prediction of GIA induced vertical surface deformation in Northwestern Europe, by adapting the existing model. In doing so, a better understanding of the interior of the Earth in Northwestern Europe can be achieved.<br/><br/>The response of the Earth is dictated by the composite rheology creep flow laws for olivine (Hirth and Kohlstedt, 2003). By varying the grain size as well as the water content of the mantle material, and by implementing a global temperature model of the Earth s interior, four 3D composite rheology Earth models are obtained. The fifth Earth model considered is the radially symmetric VM5a viscosity profile developed by Peltier et al. (2015) in conjunction with the global ice model ICE6G_C. The performance of all five Earth model configurations in combination with both the ICE6G_C model and the Bradley2018 model is analysed in terms of relative sea level and uplift rates.<br/><br/>It is found that the Bradley2018 model is the preferred ice model for GIA modelling in Northwestern Europe. The ICE6G_C model outperforms the Bradley2018 model at farfield RSL sites, which is attributed to its superior representation of global eustatic sea level rise. The 3D composite rheologies lead to improved fits to RSL observations for the majority of the investigated measurement sites compared to the 1D scenario. The dry 4 mm grain size rheology yields the best overall performance out of all rheological configurations considered. A preference towards wet rheology exists in regions of SvecoNorwegian tectonic origin. The strongest rheology is preferred in the mid< west of Scotland. No definitive connection is found between the local tectonic origin and preferred rheology fromRSL simulations. It is believed that this analysis may benefit from the inclusion of laterally varying grain sizes and water content inferred from geophysical observations, as well as the extension of the variable space for the water content.<br/><br/>For both ice models, an improved fit to observed uplift rates can be obtained through the application of a 3D composite rheology. The GPS derived uplift rates can be reproduced best using the dry 10 mm grain size rheology in combination with the Bradley2018 ice history. This model is deemed to be best suited for simulation of GIA induced uplift rates in Northwestern Europe. The secondbest performance in terms of uplift rate is found using the 1D Earth model. In Scandinavia the 4 mm dry rheology yields uplift rates equal to roughly half the observed uplift rates, while the uplift rates for the 10 mm and 4 mm wet rheologies are nearzero. In the farfield, where other surface deformation mechanisms may infer a larger deformation rate than GIA (Fokker et al., 2018), no model could reproduce the observed uplift rates.<br/><br/>The presence of a high viscosity anomaly beneath Eastern Fennoscandia is captured by the 3D rheologies and results in a shift of the centre of positive and negative uplift rates. As the spatial distribution of minima and maxima in both uplift rates and RSL change rates is sensitive to the inclusion of a 3D rheology, this should be accounted for in future regional sea level change and surface deformation projections.<brGlacial Isostatic Adjustment; Relative sea level; Composite rheology; GPS; FEM; Fennoscandia; British Isles; Postglacial rebound; Viscoelasticityen
master thesis)uuid:b3973e65336e458db8877d36edbef3fdDhttp://resolver.tudelft.nl/uuid:b3973e65336e458db8877d36edbef3fdSteering towards Stiffness: A preliminary analysis method for local deformations in a yacht structure caused by waveinduced loads4van der Linde, Luuk (TU Delft Aerospace Engineering)van Campen, Julien (mentor); Van Wijngaarden, Martijn (graduation committee); Sinke, Jos (graduation committee); Saunders, Gillian (mentor); Delft University of Technology (degree granting institution)The superyacht industry faces an increasing trend of larger dimensions, more open spaces, larger hull openings and more exotic shapes. This puts more effort on the structural design and especially for superyacht longitudinal stiffness is important, since the luxurious interior and delicate systems installed in a superyachts are not allowed to cause creaking noises or be damaged. A method is developed that can provide global and local deformations in operational sea conditions to use for risk assessment and provide guidance on clearances or connections that should be used for interior installment. Waveinduced loads are calculated with a linear response analysis in combination with a regular equivalent design wave. The yacht hull is modelled as a 1D Timoshenko beam including shear deformations and torsion for which good agreement is found with a detailed 3D FE model with shear deformations accounting for 20% to the vertical displacement. <br/><br5Superyachts; Longitudinal stiffness; waveinduced loads; strip method; linear response analysis; Timoshenko beam theory; Shear deformations; Comfort; risk assessment; equivalent design waves; Finite Element Method; 1D beam elements; FEA; FEM; Finite Element Analysis; Structural analysis; Structural ModellingAerospace Engineering)uuid:5bd246b8d608412cbb1278cc231c5df0Dhttp://resolver.tudelft.nl/uuid:5bd246b8d608412cbb1278cc231c5df0[Mechanical Influence of the Intervertebral Disc on the Vertebrae: A Finite Element AnalysisJTazelaar, Eliane (TU Delft Mechanical, Maritime and Materials Engineering)Dankelman, Jenny (mentor); Phillips, Andrew (mentor); Favier, Clement (mentor); Delft University of Technology (degree granting institution); Imperial College London (degree granting institution)Background: To find treatment options for lower back< pain, one must gain insight in the spinal anatomy and biomechanics such as joint reaction forces and movement strategies. These can be acquired with use of the Finite Element Method. Previously investigated finite element models of the lumbar intervertebral disc have been designed with the main purpose of understanding the biomechanics of the disc itself, and not necessarily its influence on other spinal elements. A change in disc biomechanics is hypothesised to cause a disruption in the surrounding structures such as the vertebrae which, in turn,<br/>could result in lower back pain. Goal: To create a finite element model of a spinal unit for investigating mechanical influences of the disc onto its adjacent vertebrae. Assessment was performed by examining bone adaptation as a result from simulated disc generation. Methods: A MATLAB script was written to assemble an input file of a parametric model to be used for finite element analyses in Abaqus/CAE. The model was validated with experimental data from literature. A bone adaptation algorithm was used to assess a change in bone material properties before and after simulating disc degeneration by adjusting disc material properties. Results: Finite element analyses showed how a load was transferred by the disc and how bone consequently adapted in response to simulated disc degeneration. The overall trabecular structure was observed to become softer, especially in the vertebral core, while the structure inferior to the anulus became relatively stiffer. Conclusions: Visualisation of bone adaptation after simulating disc degeneration supports the hypothesis that disrupted disc biomechanics indeed affect bone configuration in the adjacent vertebrae.IFEM; intervertebral disc; biomechanics; spine; vertebrae; bone adaptation/Mechanical Engineering  Biomedical Engineering)uuid:51e618cab5704983a732844a34ea98beDhttp://resolver.tudelft.nl/uuid:51e618cab5704983a732844a34ea98be[Damage to Masonry Houses due to a Riverine Dyke Breach: A hydraulic and structural approach9Teeuwen, Max (TU Delft Civil Engineering and Geosciences)Jonkman, Bas (graduation committee); Molenaar, Wilfred (mentor); Hoogenboom, Pierre (mentor); Delft University of Technology (degree granting institution)"The Netherlands has always been in close proximity to water, whether its rivers or the sea. This proximity to water and the need for land to settle and farm, led to vast amounts of land reclamation by constructing dykes along the water features to prevent flooding of the new earned land. This newly reclaimed land started to subside over the years, increasing the difference between the high water in the rivers and the lowlying land even more. With an expanding population, rising water levels and increasingly severe storms, the consequences of a future flood due to a riverine dyke breach are ever rising. <br/>The aim of this thesis follows from these increasing consequences and is to determine the potential structural damage to a masonry house due to a dyke breach leading to a riverine flood.3masonry; dyke; bore; breach; DIANA; FEM; flood wave)Civil Engineering  Hydraulic Engineering)uuid:615f2151bcae4e78a2cb3f1891a28275Dhttp://resolver.tudelft.nl/uuid:615f2151bcae4e78a2cb3f1891a28275yAn Integrated Machine Learning and Finite Element Analysis Framework, Applied to Composite Substructures including Damage.Gulikers, Tom (TU Delft Aerospace Engineering)SChen, Boyang (mentor); Delft University of Technology (degree granting institution)Engineering fields such as aerospace rely heavily on the Finite Element Method (FEM) as a modelling tool. In combination with the scale and complexity of the structures typically involved here, computational cost remains a traditional issue. To perform FEM analyses of such structures efficiently nonetheless, engineers rely on techniques such as substructure homogenisation. Essentially, the advantages to using homogenised models are an easier division of labour, less model preparation time and a reduced computational time. Unfortunately, the classical approach to substructurin< g is either limited to linear elasticity as in the case of static condensation, or is still computationally expensive as nonlinear FEA of detailed substructure models need to be performed each time a different loading is applied to the full structure. To improve the efficiency and/or accuracy of homogenised substructures, it would therefore be of interest to develop a methodology which allows to capture a complex structural response without constantly resorting to nonlinear FEA. An emerging technology that may assist in improving the efficiency and accuracy of how homogenised substructures are modelled, is machine learning. While the fundamental principles of this field were developed in the 1940's, the everincreasing accessibility and magnitude of computational power have resulted in a leap of popularity since the 1990's. Especially the (deep) Artificial Neural Network (ANN), a versatile machine learning framework, has proven to be a promising tool that can perform tasks ranging from image recognition to the failure analysis of composites. In the current master's thesis, a framework is developed that integrates ANN and FEM techniques as to establish a highly flexible approach to substructure homogenisation. More specifically, this framework allows to establish a homogenised representation of a substructure regardless of its structural complexity (e.g. inclusions or cutouts) and material complexity (e.g. damage progression and failure). To achieve this, traditional techniques to approximate homogenised behaviour are replaced by a constitutive model that is captured in an ANN. The developed framework consists of three parts. Firstly, the data generator module creates, runs and postprocesses a series of FEM simulations of a chosen substructure, based on a predetermined Design of Experiments. In this DoE, all independent parameters (e.g. applied loads) that influence the response to be modelled should be sufficiently varied. The second module trains an ANN based on the generated data. In doing so, it learns to predict the homogenised mechanical behaviour of the chosen substructure as a function of the independent parameters. The third module then integrates this trained ANN in the FEM software package Abaqus as a user material subroutine (UMAT). The substructure of choice is now homogenised and represented by a single element, which can be readily used together with traditional elements in a global model.<br/>The described methodology was applied to two FEM models of increasing complexity. The first model was a biaxially loaded, 2D elastoplastic high strength steel material without additional complexities. An initial ANN design was made based on this model and it turned out that a network with 2 Hidden Layers (HL) and 10 nodes per HL was ideal to capture the response. Furthermore, it was determined that the ANN converged after training for 1,500 epochs with the 'Nadam' scheme. The second model was a composite plate with an elliptical cutout and Hashin damage, thus adding both structural and material complexities. This model was loaded in biaxial tension and inplane shear. A 2HL network was found to be the most suitable architecture with 60 and 40 nodes in each HL respectively. A training time of 10,000 epochs was required to reach convergence using the Nadam optimiser, which led to an excellent fit of the mechanical response. Moreover, several input and output vectors for the ANN were investigated. It was concluded that the best results are obtained if the input vector contains the previous and current stress and strain state as well as the strain increment, whereas the output is the predicted stress increment.Composites; Homogenisation; Homogenization; Substructuring; Machine Learning; Neural Networks; Artificial Neural Networks; Structural Analysis; Structural Modelling; Finite Element Method; FEM; Finite Element Analysis; FEA; Damage
20181220)uuid:293a5061ec1644bb80dcd0d7adb3ff9cDhttp://resolver.tudelft.nl/uuid:293a5061ec1644bb80dcd0d7adb3ff9cCBehaviour of Suction Caisson subjected to Cyclic Loading in TensionDSu< dhakaran, Kamaleshwar (TU Delft Civil Engineering and Geosciences)Askarinejad, Amin (mentor); Gavin, Ken (graduation committee); Lanzafame, Robert (graduation committee); Galavi, Vahid (graduation committee); Delft University of Technology (degree granting institution)XAs countries around the world are in a race for clean energy, various renewable energy sources are harvested to meet the energy needs. In Western Europe, wind energy is the primary source of renewable energy. To meet the energy demand, higher capacity wind turbines are being installed in deeper waters. In deep waters, monopile foundations are ineffective due to its inability to withstand large overturning moments. Thus, multicaisson foundations are preferred in deeper waters. Typically jacket or tripod foundations are preferred as multicaisson foundation and these foundations are supported by either piles or suction caissons. Suction caissons are preferred due to the ease of installation and removal.Based on the literature, it was understood that various kinds of research are being undertaken throughout the world to better understand the performance of suction caisson foundations. Two main components of suction caisson are researched widely, first being the installation behaviour, and second being the behaviour of caisson during repeated cyclic loading. This thesis seeks to gain further insight on the installation behaviour of the suction caisson. For this purpose, a suction installation apparatus was designed to be used in centrifuge. Various installation characteristics such as flow rate, soil profile has been studied in this thesis and detailed analysis is provided. Extraction tests of caisson were also done at a slow rate to determine the drained tensile capacity, which was used for determining tensile amplitudes in cyclic loading tests.Tripod structures withstand load by pushpull system, where the windward caisson is pulled out of the soil due to the cyclic environmental loads. This movement is compensated by the push behaviour of the other two caissons. Thus, the tensile capacity ofcaissons plays an important role in the design of caissons in a tripod structure. Windward caisson of a tripod foundation was modelled in this thesis to study the behaviour of the caisson under cyclic loading in tension. Cyclic loading tests were done at 100g using the geocentrifuge at Delft University of Technology. A series of tests was done for various cyclic loading characteristics such as the average load, frequency and soil profile. Settlement and stiffness response of the suction caisson were obtained for each scenario. A brief discussion of the results is made in this thesis report. Very high settlement was observed when oneway compressive load was applied on the caisson installed in layered sand. A test was also done to study the response of caisson to storm loading where very high tensile amplitudes were used. The results obtained from these tests show the complexity of the response under tensile loads. When the tensile amplitude was more than 50% of the tensile capacity of the caisson, significant uplift of the caisson was witnessed along with a significant reduction in the stiffness of the soil.Finally, Finite Element Modelling (FEM) was done using the geotechnical finite element software  Plaxis 2D to compare the cyclic loading results obtained from centrifuge modelling with FEM. It was observed that the initial settlement behaviour was captured well in plaxis. But after few cycles, no more accumulation of strain was witnessed in the centrifuge tests. However, plaxis failed to capture this behaviour and thus higher settlements were observed in FEM analysis.This thesis can be used as a basis for the design of tripod foundations for OWT using suction caissons. The results obtained from this thesis reinforces previous studies and adds confidence in understanding the tensile behaviour of suction caissons.FSuction caisson; Offshore Wind Energy; Sand layer; Cyclic loading; FEM
20201231#Civil Engineering  GeoEngineering)uuid:213ce335202a4f7488f2737c853c42a0Dhttp< ://resolver.tudelft.nl/uuid:213ce335202a4f7488f2737c853c42a0Analysis of Single and Group Micropile Behavior: The Bearing Capacity of Single Pile and Pile Groups under Axial Tensile Loading using FEM[Feiz, Marziyeh Sadat (TU Delft Civil Engineering and Geosciences; TU Delft Geoengineering)Broere, Wout (mentor); Brinkgreve, Ronald (mentor); Gavin, Ken (mentor); Hendriks, Max (mentor); Haasnoot, JK (mentor); Delft University of Technology (degree granting institution)This thesis investigates the behavior of single and group micro piles under axial tensile loading. Micro piles are small diameter piles consist of grout and steel rebar and they are capable of absorbing tensile loads. By constructing a group of piles the bearing capacity of each pile within a group is less compared to the single pile. The reason is due to the existence of group effect in the pile group which influences the bearing capacity. During the production of the piles for Amsterdam car parking project, load tests are performed to check whether the piles behave according as expected which can be considered as acceptance tests. However in this test, only individual piles are tested and not a pile group. CUR 236 design procedure states that the bearing capacity of a pile in a pile group is less than the bearing capacity of that pile when it is loaded not in a group. To take this effect into account for the acceptance test, an additional load is added to the test load. It turned out at the Amsterdam car parking project that piles failed the acceptance tests due to this additional load which is required to apply according to CUR 236 design guide. However this procedure is questionable because the pile is loaded into a much higher level than it will actually experience during its lifetime. Therefore an evaluation of the standards and the influence of group effects on micro pile behavior is needed. The initial plan of approach was to investigate the standards of other countries and compare them to Dutch standards to find the eventual existing gap and propose an improvement method which did not succeed. The reason was that the standards of other countries were all written in their national language and therefore it was not possible to study them. Seeking for the research on tension pile group behavior did not help so much because many researchers believe that including a realistic group effect in the design is not an easy task and there was no clear conclusion on micro pile group influence. The direction of approach is then changed towards the numerical modelling and based on it the influence of group effects on micro pile behavior is presented. First a single micro pile is modelled with Finite Element Method in Plaxis. The single pile is finally modelled in plane strain by using Embedded Beam Row element. Model parameters and properties are defined based on Amsterdam case study. The loaddisplacement behavior of the single pile model was comparable with the one from Amsterdam field failure test and is therefore validated based on field failure test data. After development of single pile model, the model for pile groups is made. This group model is made to represent the practical situation in a building pit for Amsterdam case study. Three models for the pile group have been made which differ in pile spacing and the impact of this parameter on the capacity per micro pile is investigated. The different used pile spacings are 5D, 10D and 15D which are equal to 1 meter, 2 meters and 3 meters. Also for each pile spacing, the dominant failure mechanism is determined. According to the results it was concluded that for 5D and 10D pile spacing, the failure mechanism is based on soil plug pullout while for 15D, it is according to slip failure. By validation of the pile group model, an improvement for the space between the piles within a pile group can be proposed as 10D where the soil plug pullout is dominant failure mechanism. It is recommended to validate the pile group model based on fullscale failure test on pile groups or by smallscale test using Geocentrifuge models< . Also by monitoring, a real data base of the group behavior can be obtained. Comparing the monitoring data to the design values based on CUR 236 could give an idea how well the design guide is formulated.bMicropile; Plaxis; FEM; Analysis; bearing capacity; Single pile; Pile group; Axial tensile loadingCivil Engineering)uuid:0314e592ffa24f1dbc315da7011805b7Dhttp://resolver.tudelft.nl/uuid:0314e592ffa24f1dbc315da7011805b7KImplementation of a FluidStructure Interaction Solver for a Spinnaker Sail/Ramolini, Anna (TU Delft Aerospace Engineering)van Zuijlen, Alexander (mentor); van Oudheusden, Bas (graduation committee); Schmehl, Roland (graduation committee); Folkersma, Mikko (graduation committee); Delft University of Technology (degree granting institution)7The design of sails has always been done experimentally, and only recently simulations are starting to be used in the design process. This thesis is a first attempt in creating a solver that couples CFD and FEM in order to compute the deformed sail shape (flying shape) and the thrust it can provide. Such solvers already exist but are not available to the public, or if they are they come with a very high license price. The complexity of the problem is both in the flow, which is fully turbulent and detached, and in the structure, which is deformable and free to move in all directions. Moreover, the coupling of the solvers has to be performed in a way that minimizes loss of information and accuracy.<br/>First the CFD simulations have been run and validated with two softwares, OpenFOAM and FINE/Open. The results were very satisfying for FINE/Open, while quite poor for OpenFOAM. Consequently, the FEM solver has been successfully validated for some cases of which the analytical solution is known, due to lack of reference data for this specific case. <br/>Finally, the interpolation techniques have been implemented in Matlab and the fluid structure interaction solver has been run. The solver has been validated on a given testcase with satisfying results; however there is still room for improvement in terms of run times and automatization of the solver. From the results it can be argued that the design and flying shape of the sail are quite different and provide different thrusts. That is an indication of the significance of this type of analysis in the sail design process.9Fluid Structure Interaction; CFD; FEM; Sailing; Spinnaker)uuid:dca3dbc82b744904ba89084cdb97ff64Dhttp://resolver.tudelft.nl/uuid:dca3dbc82b744904ba89084cdb97ff64Glass Flood Defences: A theoretical and practical assessment of the impact resistance of Glass Flood Defences to floating debris?van der Meer, Roos (TU Delft Civil Engineering and Geosciences)Nijsse, Rob (mentor); Veer, Fred (mentor); Molenaar, Wilfred (mentor); Staphorsius, John (mentor); Lenting, Fred (mentor); Delft University of Technology (degree granting institution)In the far south of the Netherlands, the erratic river Meuse flows through the landscape. It recently flooded twice in the 1990s, causing much economical damage. Emergency measures, such as a demountable flood wall, were taken to prevent future flooding. And while this solution was to the liking of the inhabitants, the update in the flood safety standard called for a more permanent structure. In the search for an alternative and permanent solution, a glass flood wall was suggested.<br/><br/>Nowadays there are not many examples of glass used in a flood defence in Dutch practice, and certainly not as part of a primary flood defence. It can be classified as an innovation, from which little is known from a structural safety perspective. Glass is used globally to retain water in numerous applications such as aquaria, under water glazing, glass bottom boats, etc; therefore water pressure is not seen as a high risk to the glass. What happens when floating debris hits the glass structure? Impact on glass can result in immediate failure, where the water retaining function could be lost. This thesis aims to answer this question, by theory and later on by impact experiments in a dr< y setting.<brWGlass; Flood Defence; Impact; Floating debris; Glass structures; Experiment; FEM; RiverStructural Engineering)uuid:bb7b15873ec14c7d8d285ca8406af029Dhttp://resolver.tudelft.nl/uuid:bb7b15873ec14c7d8d285ca8406af029Test Loading of Quay Structures using FEM: A case study to determine the load capacity of the old Amazonehaven and the SIF quay structures>van Weringh, Mark (TU Delft Civil Engineering and Geosciences)Gavin, Ken (mentor); de Gijt, Jarit (mentor); Brinkgreve, Ronald (mentor); Broos, Erik (mentor); Mourillon, Nadevah K.N. (mentor); Pacejka, H.E. (mentor); Putteman, Jan (mentor); Delft University of Technology (degree granting institution)tQuay structures play an important role in society. How much load these structures can withstand however is not certain. This MSc thesis contains insight into the load capacity of the old Amazonehaven and the current SIF quay structures. Both are quay structures which use a combined sheet pile wall, a reinforced concrete relieving platform, M.V.piles, and two rows of bearing piles. The objective of this MSc thesis was to determine the load capacity of the structures, the models should therefore be as close to the actual conditions as possible. For that reason no safety and/or material factors have been applied throughout this MSc thesis. The approach is shown below.<br/>A literature study was performed to gain insight into the areas of interest that needed to be studied. This theory in combination with a review of the structures led to the critical cross sections of the respective structures. These cross sections were then modelled with conventional design methods (Blum and DSheet Piling). The Blum method determined the individual contributions of several aspects (loads, water, soil) to the horizontal stress distribution along the combined sheet pile wall and calculated the reaction forces using a set of boundary conditions. Within DSheet Piling the relieving platform was modelled by removing it, the loads that acted on it, and the soil that rested on it. The last method that was applied was a FEM software (Plaxis 2D). The FEM models were validated in three steps: First, by comparing their results to that of the conventional methods, it was found that the results of the conventional methods were within ca. 30% of the FEM results. Second, by comparing the results to actual field data, here the results showed both deviation and similarities, these deviations could however be explained. Lastly, by critically assessing the models to ensure that certain aspects were incorporated into the models correctly, this resulted in uncertainty about drained or undrained soil conditions for the thicker clay layers. The main function of both quay structures was the storage of certain goods, for that reason the only aspect that was not constant in the test loading set up was the magnitude of the primary surcharge. Both geotechnical and structural failure were taken into consideration for the quay structures.<br/>The results of the FEM models showed that neither of the structures had failed at their design loading conditions. For the Amazonehaven it was found that the magnitude of the primary surcharge at the first failure of the model was relatively close to that of the design loading conditions, it was incited by the exceedance of the geotechnical bearing capacity of the M.V.piles. The first failure of the SIF model occurred at a surcharge that was more than 4 times the magnitude of the design loading conditions, it was incited by the exceedance of the normal stress capacity of the M.V.piles.FEM; combined sheet pile wall; quay structures; relieving platform; M.V.piles; Blum; DSheet Piling; Finite Element Method; Plaxis 2D; load capacity; Maasvlakte,Hydraulic Engineering  Hydraulic Structures51.9595317, 3.985464)uuid:277f7b383eb2455d9d4fc5afdf349b06Dhttp://resolver.tudelft.nl/uuid:277f7b383eb2455d9d4fc5afdf349b06JAn investigation of finite element model updating of the Pioneering SpiritHSchout, Arthur (TU Delft Mechanical, Maritime and Materials Engineering)Kamin< ski, Mirek (mentor); Bos, Reinier (mentor); van Woerkom, Paul (mentor); van der Horst, Tim (mentor); Rodenburg, Freek (mentor); Delft University of Technology (degree granting institution)Correctly predicting the structural behavior of the Pioneering Spirit is vital for ensuring the structural integrity of the ship and the cargo. A detailed finite element model is used to predict the structural behavior of the Pioneering Spirit. The finite element method is based on fundamental principles in solid mechanics. However, when using finite element models considerable differences between the predicted and observed behavior of a structure can occur, even when best industry practices are used to create such models. Because of these<br/>differences there is a need to validate the detailed finite element model of the Pioneering<br/>Spirit.<br/>Finite element model updating is a method that can validate finite element models. In this method the discrepancy between the measured behavior and the observed behavior is minimized by modifying model assumptions and parameters. Currently a number of sensors is installed on the Pioneering Spirit, which can be used to find the measured behavior. Whether or not the measured behavior is detailed enough to be used in the validation of the finite element model is the subject of this research. To investigate this a simplified finite element model of the Pioneering Spirit was created using beam elements, this model provides the predicted behavior. Then sensitivitybased finite element model updating was implemented and applied to the beam model. <br/>Simulated<br/>measurements were used to show that the beam model can be updated using the current sensor setup. When actual measurements were used to update the beam model it was found that the beam model does not correlate with the measured behavior, making it impossible to update the beam model in a meaningful way. <br/>The detailed model does correlate with measured behavior. By assuming that the method will work similarly for the detailed model as it did for the beam model, it can be concluded that the detailed model can be validated using the current sensor setup for a static case. For a dynamic case this is not possible.(FEMU; Finite element model updating; FEM
20230827)uuid:f72a6568d033480384773c4727c82de0Dhttp://resolver.tudelft.nl/uuid:f72a6568d033480384773c4727c82de08Structural Wave Propagation in Unconsolidated Granulates9Evans, Louis (TU Delft Civil Engineering and Geosciences)Van Damme, Bart (mentor); Manen, Dirk Jan Van (mentor); Drijkoningen, Guy (graduation committee); Delft University of Technology (degree granting institution); ETH Zrich (degree granting institution); RWTH Aachen University (degree granting institution) Unconsolidated granulates exhibit complex, nonlinear behaviour when subjected to dynamic forces. The presence of granular contacts gives this type of material a relatively low stiffness and provides hysteretic energy losses. These features make unconsolidated granulates suitable for railway ballast as it provides dissipation of vibrational energy from passing trains which is important to minimise vibrational disturbance. However, simulating the response of the railway superstructure under dynamic loads becomes difficult due to then onlinearity of the ballast. In order to develop better prediction tools, the elastic behaviour of unconsolidated rocks is first investigated experimentally by quasistatic and dynamic stressstrain experiments yielding the Young's modulus, nonlinear resonance shift and analysis of harmonic generation. In addition, the transmission of structural waves through granulates is investigated by assessing the transfer function for different thicknesses of granulates, different<br/>particle sizes and different materials with varying viscous damping. Three granulates are used, smallscale ballast, a gravel, and two sizes of uniform steel spheres. All three materials exhibit a combination of classical and hysteretic nonlinearity where the strain depends on the stress amplitude and history.<br/><br/>< A completely new finite element approach is taken to model the hysteretic nonlinearity, based on an existing phenomenological static model. Multiple springslider elements with gaps are used, as opposed to implementing a homogenised material model. It is shown that only 50 elements can reproduce the hysteretic nature of the material, which is a significant advantage to a traditional material model requiring the discretisation of the entire ballast volume. Each springslider element is parameterised by two springs constants, a yield force and an initial gap. A distribution of these parameters across the 50 elements is found that reproduces the quasistatic stress cycles acquired experimentally. In addition, a parametric study of the model parameters during dynamic excitation reveals that key indicators of nonlinearity can be simulated. The finite element simulations prove that using a set of springslider elements<br/>to model the behaviour of unconsolidated granulates is viable method. With experimental tests performed on true ballast and further work on the finite element model to understand optimal parameter distributions, a more accurate and efficient railway superstructure model can be produced.geophysics; FEM; granulates Applied Geophysics  IDEA League)uuid:86d469f30c444f459396ec296d87031fDhttp://resolver.tudelft.nl/uuid:86d469f30c444f459396ec296d87031fnA Multiphysics Numerical Framework for Epoxy Resins: Investigating Hygrothermal Ageing in Laminated Composites@van Leeuwen, Robbie (TU Delft Civil Engineering and Geosciences)van der Meer, Frans (mentor); Barcelos Carneiro M Rocha, Iuri (mentor); Sluijs, Bert (mentor); Bessa, Miguel (mentor); Delft University of Technology (degree granting institution))Epoxy resins are increasingly used in critical structural components with widespread applications in the transportation, construction and energy industries. The wind energy sector is one of the fastest growing commercial markets for epoxy resins, meaning that the structural behaviour of epoxy resins is becoming a key area of research, especially regarding its application to wind turbines. Wind turbines, particularly those in offshore installations, are subject to a wide range of environmental conditions, most notably large variations in humidity and temperature. Both moisture and increased temperatures have been observed to have a significant impact on the stiffness and strength of epoxy resins. These environment effects, coupled with complex time dependent mechanical behaviour, means that the accurate prediction of the structural performance of epoxy resins has not yet been fully described.<br/><br/>This thesis presents a multiphysics framework for the simulation of hygrothermal ageing in epoxy resins. The constitutive model formulated in this thesis consists of a nonlinear viscoelastic and viscoplastic mechanical model, physically coupled with a Fourier heat conduction model and a Fickian diffusion model. Degradation based on a glass transition surface is implemented to describe the multistate behaviour of epoxy resins. To justify the model assumptions, DMA and creep tests are performed on epoxy resin specimens and their temperature dependent mechanical behaviour is established. A number of numerical benchmark tests and case studies are performed using a finite element implementation of the numerical framework. It is shown that the multiphysics framework can capture the characteristic mechanical and hygrothermal ageing behaviour exhibited by epoxy resins. Recommendations are provided for further development of the numerical model and calibration of the material properties. In a secondary study, a mesh sensitivity analysis is performed on an existing viscoelasitcviscoplasticdamage model and recommendations for an improved formulation are provided.yMultiphysics; Viscoelasticity; Viscoplasticity; Epoxy Resin; FEM; Hygrothermal Ageing; Continuum Damage; Glass Transition0Structural Engineering  Computational Mechanics)uuid:903db7967f254ce3b5cec92fd207c883Dhttp://resolver.tudelft.nl/uuid:903db7967f254ce3b5ce< c92fd207c883jDevelopment of a Reliable and Efficient 3D Calculation Model of a HighRise Building Under Seismic Loading:Mussche, Henk (TU Delft Civil Engineering and Geosciences)Rots, Jan (graduation committee); Hendriks, Max (graduation committee); Terwel, Karel (graduation committee); Delft University of Technology (degree granting institution)This thesis research focusses on the development of a reliable and efficient 3D calculation model of an existing highrise, reinforced concrete building in the Groningen area, in order to analyse the dynamic behaviour of the existing and subsequently retrofitted main bearing structure of this highrise building. The assessment of the existing building is performed through a NonLinear Time History analysis in Simulia Abaqus, in which cracking of concrete and yielding of reinforcement is taken into account. Multiple NLTH analyses are performed for optimisation of the 3D model in order to obtain correct results with a minimum amount of calculation costs. This optimisation process results in a clear understanding of the dynamic behaviour of the building and the main sensitivities of the model. <br/>The 3D model is verified by means of a simplified 1D beam type model, developed and analysed with the software package Matlab. This 1D model consists of three elements, corresponding to the three main structural parts of the building. Next to this, a modal response spectrum analysis is performed for verification of the 3D model results.<br/>The seismic assessment of the building is performed according to the Near Collapse criterion of the NPR. The results show that the building meets this criterion, based on one record of the NPR. Since at least seven various records should be applied, it is possible that the building does not meet the Near Collapse criterion for one of these records. Also from a structural point of view, it is interesting to develop and analyse strengthening possibilities for this specific building. therefore, three strengthening proposals are developed and initially analysed with the 1D model in Matlab.Seismic; Abaqus; 3D Model; Reliable; Efficient; 1D Model; Simulia; Matlab; Groningen; Response; Response Spectrum; Accelerogram; NPR; Near Collapse; Seismic loading; Modal Response Spectrum Analysis; Verification; Base Shear; Existing; HighRise; Reinforced Concrete; Earthquake; Earthquake analysis; Human induced; Gas extraction; dynamic behaviour; strengthening; strengthening measures; Zonneveld ingenieurs; TU Delft; Harm Hoorn; Jan Rots; Max Hendriks; NPR9998; Eurocode 8; Concrete Damaged Plasticity; NLTH; NLTH Analysis; Euler Bernoulli; Plastic analysis; Nonlinear; Awesome; Optimisation; Finite Element Method; FEM; Analysis; Henk Mussche)uuid:4614239a961c4ceebbbf87431119e2caDhttp://resolver.tudelft.nl/uuid:4614239a961c4ceebbbf87431119e2caAn improved 3D embedded beam element with explicit interaction surface: A study into the improvement of a numerical modelling technique that enables simplified modelling of pile foundationspSmulders, Carla (TU Delft Civil Engineering and Geosciences; TU Delft Materials Mechanics Management & Design)Sluijs, Bert (mentor); Brinkgreve, Ronald (graduation committee); Houben, Lambert (graduation committee); Hosseini, S (graduation committee); Delft University of Technology (degree granting institution)
Numerical modelling of pile foundations can be done in several ways. In commercial finite element packages two main options are available; using volume elements with interface elements between the pile and soil domains and the embedded beam approach. The embedded beam element was first proposed by Sadek and Shahrour (2004) and considers a beam element that can cross a solid element at any arbitrary location with any arbitrary inclination. This has several advantages to the volume pile method, such as the need for fewer elements and the mesh uncoupling of the pile and soil, which make this method much more efficient and leads to a significant reduction in calculation time. However, the embedded beam element also deals with a number of< limitations and drawbacks. This research focuses on overcoming the mesh sensitivity, which is caused by the stress singularity that is introduced in the soil by the beam element. Also, the inability to take into account the pile surface will be resolved, aiming to improve the lateral pilesoil interaction.<br/><br/>The idea of Turello et al. (2016) of an embedded beam element with explicit interaction surface is extended and generalised leading to a new embedded beam formulation. In the proposed model the beam displacements at the interaction surface are obtained by a mapping scheme that takes into account Timoshenko beam theory and which is generalised to model inclined piles as well. A constitutive equation that describes the relation between the interface stresses and relative displacements between the pile and soil is defined along the shaft and at the foot of the pile. Along the shaft of the pile a shear stress limit is defined based on the MohrCoulomb failure criterion in order to incorporate plasticity in lateral direction. Furthermore, a more practical and efficient assembly procedure is proposed. <br/><br/>Validation of the proposed method proofs that the proposed model leads to a significant mesh sensitivity reduction in case of axially loaded models compared to the existing implementation. The overall response of laterally loaded piles is improved considerably as well. However, the proposed method is still unable to capture lateral interface behaviour in order to model soil slippage around the pile. Furthermore, it is recommended to formulate a generally applicable foot interface stiffness and to optimise the code in order to reduce the computation time. The description of the interaction surface opens up many new possibilities for future research, such as modelling the true crosssection shape. <br,Embedded beam element; FEM; pile foundations)uuid:8af78bca42b44bcb9546ac32cea590f2Dhttp://resolver.tudelft.nl/uuid:8af78bca42b44bcb9546ac32cea590f2qThe Prediction of Multiscale Voids and Their Mechanical Effect on Thick Composite Structures Manufactured by RTM/Wang, Yuanyuan (TU Delft Aerospace Engineering)van Hoorn, Niels (mentor); Kassapoglou, Christos (mentor); Turteltaub, Sergio (mentor); Delft University of Technology (degree granting institution)Thick composite laminates can be used in aerospace and automotive industry replacing metals for weight saving.<br/>Increasing the thickness can bring more defects, like voids.<br/>This master thesis focuses on the multiscale voids prediction and their mechanical effect simulation of thick composite laminates manufacturing by \ac{RTM}.<br/>It could be potentially used in safe design of thick composite components.<br/>The main objective of the thesis work is to analyze the effect of multiscale voids caused by the filling process on mechanical properties of thick composite laminates. <br/><br/>First is using PAMRTM to simulate the locations of voids and their percentage.<br/>Then, the material properties of each \ac{MVE} with different micro and macro voids are evaluated by Digimat at micro and meso scales.<br/>After that, the macroscale material properties of the thick laminates are simulated in ABAQUS.<br/>%This simulation process is reliable after verifying with the results of a literature.<br/>The simulation processes are verified by using the parameters from the literature and then comparing with the published results.<br/><br/>The simulation from PAMRTM indicates the average void percentage of the whole laminate reduces with the increasing injection pressure or permeabilities.<br/>The total void volume increases with an increasing laminate thickness but the average void volume does not change with the changing thickness.<br/>The result of this thesis suggests that the effect of multiscale voids on material properties (i.e., Young's modulus, Poisson's ratio, and Shear modulus) does not change due to an increasing thickness.<br/>The writing presents the actions taken in order to achieve the objective of the research successfully. Thick compoiste; RTM; voids; < FEM)uuid:d1b776855b954991bd417ce4cdd01605Dhttp://resolver.tudelft.nl/uuid:d1b776855b954991bd417ce4cdd01605Parametric reduced order modeling of structural models by manifold interpolation techniques: Application on a jacket foundation of an offshore wind turbinexSpeet, Jeroen (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Precision and Microsystems Engineering)ZLangelaar, Matthijs (mentor); Delft University of Technology (degree granting institution)An important aspect of structural design is to obtain adequate knowledge and prediction of the structure s dynamic behavior. Wind Turbine Manufacturers (WTMs) design their wind turbines for a lifetime of typically 25 years during which the structure has to withstand a large variety of loads, induced by wind and wave conditions. To obtain a suitable design, numerous load calculations have to be performed for each design. A versatile approach is to use Reduced Order Models (ROMs) to restrict the computational effort that comes with<br/>these numerical techniques, which are also used in other industries (automotive, aerospace, etc. ). However, during the design process, structural changes are often applied. Since ROMs lack robustness with respect to these variations, this approach calls for a reconstruction of the ROM each time the initial model is changed, and the intensive calculation procedure has to be repeated afterwards.<br/>With the motivation to improve the limitations of ROMs and how they are used in engineering practice, a literature survey was performed on relevant Parametric Reduced Order Model (PROM) methodologies. Based on appropriate criteria in the context of a WTM s design cycle, a methodology was selected that interpolates between the precalculated ROMs and their corresponding Reduced Order Basis (ROB). To preserve the properties these matrices typically have (i.e. symmetricpositive definiteness, orthogonality, etc.), the interpolation is<br/>performed on a matrix tangent manifold. For the three most commonly used reduction techniques, being Modal Truncation (MT), Guyan Reduction (GR) and CraigBampton (CB), the method is applied on an offshore jacket foundation, designed to support a 5 MW wind turbine, and subjected to realistic design<br/>changes in a local section of the structure. In the presented configuration, the interpolation approach is suitable to update the GR basis with high accuracy. The technique also shows good performance while updating the MT and CB basis, but challenges are found when the structure preserves symmetry properties because of close and multiple eigenvalues of the modes. Furthermore, promising results were shown while updating the ROM matrices, but influence of offdiagonal elements has been observed.OROM; PROM; reduction; reduced; parametric; FEM; structural; dynamics; eigenmode)uuid:29f2aaca239b47c583234d1ed22fd11cDhttp://resolver.tudelft.nl/uuid:29f2aaca239b47c583234d1ed22fd11cVConstraining Glacial Isostatic Adjustment with Horizontal GPS Velocities in AntarcticaIHermans, Tim (TU Delft Aerospace Engineering; TU Delft Space Engineering)VGlacial isostatic adjustment is the viscoelastic response of the Earth to ice and ocean loads. In forward models of glacial isostatic adjustment, mantle viscosity is often assumed to be laterally homogeneous. However, a lateral transition in shear wave velocities suggests a sharp transition in viscosity between West and East Antarctica. Along this transition, horizontal GPS velocities of<br/>ANET/POLENETWest of the Ross Sea Embayment point towards the ice load rather than away from it. It is unclear why, as the dependency of horizontal velocities on viscosity is not well understood. In this thesis, this dependency is clarified, and it is investigated with a 3D finiteelement model if the horizontal GPS velocities can be used to constrain the viscosity transition.<br/><br/>It was found that horizontal velocities point away from the ice load for viscosities of 1020 Pa s and lower, whereas for 1021 Pa s and higher their direction is reversed. The results in this thesis s< how that the GPS measurements at the Ross Sea Embayment likely require a lateral viscosity transition.<br/>Preferred viscosities in the upper mantle are found to lay between 1018 and 1019 Pa s at the West Antarctic side of the transition, and between 1021 and 1022 Pa s at the East Antarctic side. The results demonstrate that horizontal GPS velocities can be used to constrain lateral variations in rheology. As more studies will start to use 3DEarth models, horizontal GPS velocities should be used as one of the<br/>primary constraints of glacial isostatic adjustment, since their direction can be reversed depending on mantle viscosity.aGlacial Isostatic Adjustment; GPS; Horizontal; Antarctica; FEM; 3D; Viscosity; Ross Sea Embayment
20181231Astrodynamics & Space Missions)uuid:2a4f30150fb5434296c8eb6fd1d92646Dhttp://resolver.tudelft.nl/uuid:2a4f30150fb5434296c8eb6fd1d92646=A NURBSenhanced DiscontinuityEnriched Finite Element MethodKDe Lazzari, Elena (TU Delft Mechanical, Maritime and Materials Engineering)Aragon, Alejandro (mentor); van Keulen, Fred (graduation committee); van der Meer, Frans (graduation committee); Turteltaub, Sergio (graduation committee); Delft University of Technology (degree granting institution)EGeneralized finite element methods have proved a great potential in the meshindependent modeling of both weak and strong discontinuities, such as the ones encountered when treating materials with inclusions or cracks. By removing the constraint of a conforming mesh, more freedom is offered to modeling exact geometries by means of splines. However, very few studies have been published which combine NonUniform Rational BSplines (NURBS) to interfaceenriched methods, addressing uniquely weak discontinuities. Therefore, the aim of this thesis is to propose a NURBSbased enhancement to the DiscontinuityEnriched Finite Element Method (DEFEM) in two dimensions and to discuss the potential of its application. The main advantage of this method is the possibility to study problems that present discontinuities with arbitrary smooth shapes, while maintaining exact geometries throughout the analysis: in this way, the equivalence between design and computational geometry is preserved. To this purpose, a suitable NURBSbased analysis technique is selected and implemented within the framework offered by the group's finite element library, Hybrida. <br/>The capabilities of the NURBSenhanced DEFEM to solve several weakly discontinuous problems are assessed for composites of different complexities. Furthermore, a novel study is presented which extends this technique to the treatment of strong discontinuities, in the context of fracture mechanics. The accuracy, convergence properties and numerical efficiency of the proposed method are investigated, in particular in comparison with the standard DEFEM. Based on these observations, further insights are provided into the convenience and the limitations of adopting NURBS enhancements within the DEFEM formulation. Lastly, some recommendations about possible directions of improvement are provided.QFEM; NURBS; structural mechanics; discontinuities; composites; fracture mechanics)uuid:31539dc5f6954bbab277037a800df3a6Dhttp://resolver.tudelft.nl/uuid:31539dc5f6954bbab277037a800df3a6VEvaluation of the Fatigue Resistance of Offshore Jacket Joints by Numerical ApproachesQMendoza Espinosa, Jorge (TU Delft Mechanical, Maritime and Materials Engineering)Metrikine, Andrei (mentor); Muskulus, Michael (mentor); Vossbeck, Marc (mentor); Lourens, ElizMari (mentor); Delft University of Technology (degree granting institution); Norwegian University of Science and Technology (NTNU) (degree granting institution)
Jacket support structures are a preferred solution for offshore wind turbines in deeper waters. Extensive knowledge exists in relation to its construction technique as well as its crucial components, but due to considerable cost pressure, continued optimization is essential for the future competitiveness of the concept in the offshore wind business. Their joints along with < their complex welds are of special interest in terms of cost reduction. The design of tubular joints is generally driven by fatigue resistance. Due to the size, complexity and cost of these joints, this is assessed by using detailed FE models.<br/>Several aspects that have an impact on the results of the models are found to require further research and are investigated within this project: (1) influence of using solid versus shell elements in the modelling of the joint members; (2) degree of accuracy of the Efthymiou equations; (3) influence of the carryover effect in multiplanar KKjoints; (4) differences in the fatigue life predictions between the hotspot and the effective notch stress methods.<br/>Guidelines recommend the use of both solid and shell theories for the definition of the FE models used in the hotspot fatigue assessment. Both options are compared in terms of accuracy of the results and computational time. Generally speaking, significant differences are found between both models. The background of the differences is studied.<br/>The employment of the Efthymiou formulae is common in practice. These equations provide the SCF at the locations around the weld where they are found to be maximum. The output of this approach is compared with the results of numerical models. The validity of its use is quantified.<br/>Offshore wind jacket joints are mainly multiplanar KKjoints. Loading in the braces of one face of the jacket may yield significant carryover effects on the outofplane braces connected to the same joint. A parametric comparison is carried out to study the accuracy of modelling the joint as a planar Kjoint. In general, it is found that the carryover effect cannot be neglected and the assumption is not accurate.<br/>The fatigue assessment of tubular joints by means of the hotspot method is subjected to several assumptions that limit the optimization of the members. The notch concept is a more realistic method that is presented as an alternative. However, this method is not widely used in engineering practice due to the difficulties in building the numerical model and the high computational requisites. An algorithm to carry out the effective notch stress assessment, based on the submodelling technique, is proposed. A comparison of the fatigue life prediction, between the hotspot and the effective notch methods, is presented. The latter method is found to predict a higher fatigue life for many of the situations tested. Furthermore, since this method allows for a more detailed modelling, the weld profile can also be designed in order to optimize the fatigue resistance. The weld slope is found to have a significant impact on the results.<Offshore; Wind energy; Jacket; Fatigue; FEM; Hotspot; NotchEuropean Wind Energy Master)uuid:c54afaaf1bb249d8bcaba01fd061c5b8Dhttp://resolver.tudelft.nl/uuid:c54afaaf1bb249d8bcaba01fd061c5b8lAnalysis of a reinforcement detail in a bar reinforced soilmix wall: An experimental and numerical approachWDik, Inge (TU Delft Civil Engineering and Geosciences; TU Delft Structural Engineering)Hordijk, Dick (mentor); Braam, Rene (mentor); Hoogenboom, Pierre (mentor); Meijdam, Jeroen (mentor); Van Bezooijen, Joost (mentor); Delft University of Technology (degree granting institution)
Soilmix walls are subsoil walls, which are constructed by in situ mixing of soil<br/>with cement and water. The technique was initially used as a ground improvement<br/>technique and is now being developed as construction method for walls<br/>with a structural purpose. Currently these walls are reinforced with large steel<br/>profiles, which requires a large quantity of steel. Replacing the profiles with<br/>bar reinforcement might lead to a decrease in required material quantity and<br/>thus a reduction of material costs.<br/>There are multiple aspects which influence the possibilities and limitations<br/>of bar reinforced soilmix walls. These include predictability of the material<br/>quality, durability and cooperation between soilmix and the reinforcement.<br/>The aim of this project was t< o contribute to this research by analysing one<br/>of the influential aspects. The specific goal of this research project was to<br/>analyse the capacity of a reinforcement detail within a soilmix wall and define<br/>the governing failure mechanism. The research combined an experimental and<br/>numerical approach to the subject.<br/>The critical detail was chosen based on the Huybrechts et al. (2016), Ganne<br/>et al. (2010), Drendahl et al. (2004) and contact with soilmix experts. To<br/>model this detail in a finite element model, in 2D and 3D, material parameters<br/>were derived from Denies et al. (2012a), Denies et al. (2014), Denies et al.<br/>(2015a) and performed physical tests. The 2D models represented the most<br/>critical sections of the detail based on the theoretical stress distribution. The<br/>geometrical parameters of the reinforcement design were varified in the models<br/>to provide insight in the influence of the design on the capacity.<br/>The model results were used to define an preliminary set of design guidelines<br/>for the reinforcement cage, related to the depth of the wall. Since only<br/>the capacity of the detail is considered, these guidelines are not suficient for<br/>a complete design of a bar reinforced soilmix wall and can only serve as an<br/>initial indication.<br/>In conclusion, the reinforcement detail is most sensitive to failure due to vertical<br/>splitting and has suficient capacity for acceptable wall depths. As stated<br/>before there are multiple aspects relevant to the feasibility of bar reinforced<br/>soilmix walls. The predictability of the material quality, the bond with the<br/>reinforcement and the durability of the soilmix strongly influence the final<br/>capacity and behaviour of the wall. Therefore it is important to perform further<br/>research on these, and other, aspects to conclude on the total structural<br/>integrity of an entire bar reinforced soilmix wall.Soilmix; Reinforcement; FEMConcrete Structures)uuid:5ebdd5b3721741c39152e433e8108a6fDhttp://resolver.tudelft.nl/uuid:5ebdd5b3721741c39152e433e8108a6fDetermination of planar crack front geometry based on nearcrack surface displacement field obtained from simulated digital image correlation measurementsISlagmolen, Mark (TU Delft Mechanical, Maritime and Materials Engineering)Kaminski, Mirek (mentor); den Besten, Henk (mentor); Janssen, Michael (graduation committee); Synetos, Georgios (mentor); Delft University of Technology (degree granting institution)Digital image correlation (DIC) is a surface measurement technique that can be applied whilst performing experimental tests. At Delft University of Technology, a fatigue test is to be conducted and DIC will be used to measure surface displacements around the developing crack. These surface displacements are directly related to the crack geometry parameters. These crack geometry parameters can be found numerically via a minimisation algorithm where the difference between the surface displacements measured via DIC and surface displacement found via finite element analysis is minimised. Aim of present study is to perform a preliminary analysis before the experiment is performed in order to assess what is to be expected. It is looked into whether the outofplane surface displacement information that has to be taken into account since this influences the DIC hardware to be used during the experiment. Secondly, it has been looked into the noise as consequence of using DIC, and the influence of the noise on the minimisation to be performed. Finally it has been looked at the influence of the DIC noise on the accuracy of the minimisation. Since present study describes a preliminary analysis, simulated DIC surface measurements have been used. A finite element (FE) model of the specimen to be tested has been used in order to perform the study for uniaxial tension only. An algorithm using the FE model to perform the minimisation has been build and tested for simple 2D cases and a simpler 3D first before performing the 3D analysis with geometry considered. The s< imulated DIC noise taken is 0%, 1%, 2%, 5% and 10% of the mean measured displacement field in order investigate the influence of the noise on the minimisation. Present study showed that neglecting the outofplane displacement information introduces an error of around 2x10^2 millimetres for 1000 MPa uniaxial tension applied. It is assumed that the algorithm used finds the same crack geometry parameters as have been used to construct the simulated DIC surface displacement field in case no noise is applied. It is found that this is not the case in present study. Reason is the algorithm converging to local minima located very close to the global minimum. Present study showed the location of the global minimum becoming less defined when noise applied is increased, i.e. the area in which the global minimum is located becomes larger. Present study shows that the algorithm can convergence towards the target crack geometry parameters. Accuracy of the algorithm as function of the noise has been checked for the full displacement field and the displacement field where outofplane information is neglected. Confidence intervals increase for increasing DIC noise, as can be expected. Due to the local minima the algorithm might converge to, it is not possible to draw conclusions on whether the full displacement field should be taken into account in order to have the accuracy required. Therefore, it is strongly recommended to change the algorithm to take extra information into account to make the algorithm converge to the global minimum. Furthermore, it is recommended to improve the numerical model, in order to improve the speed of the algorithm. simulated DIC; FEM; Minimisation)uuid:1cea9ad436c746ec812a0dd63b79b159Dhttp://resolver.tudelft.nl/uuid:1cea9ad436c746ec812a0dd63b79b159_Analysis of Electromagnetic Behavior of Permanent Magnetized Electrical Machines in Fault ModesQHassan, USMAN (TU Delft Electrical Engineering, Mathematics and Computer Science)Polinder, Henk (mentor); Nilssen, Robert (mentor); Rkke, Astrid (mentor); Delft University of Technology (degree granting institution); Norwegian University of Science and Technology (NTNU) (degree granting institution)M
Over the years, the use of PM machines has been increasing in the offshore wind industry and marine industry. The industries thrive on efficient function of the PM machines. These machines are prone to electromechanical faults due to environmental conditions and maintenance. Out of all these faults, stator internal faults are concerning as they can lead to insulation failures which may take around 30 seconds to expand and lead to a fire on ships, or on wind turbines. These type of faults develop gradually, which gives the opportunity to control the fault currents before they reach dangerous levels. Rolls Royce Marine AS is also working to tackle this problem for their hybrid propulsion shaft generator. DNVGL requires the generator to be made electrically dead during such event and the longterm propulsion should not be affected. During such conditions, WTs are either turned off or field weakening is used to develop a fault tolerant control (FTC) by the help of power electronics for the WT. FTC helps the machine not to be turned off completely, but less power is generated during fault conditions. An alternative efficient field weakening method using a Dual Rotor PMSM was suggested for both the applications. The DRPMSM has two rotors instead of one, with identical surface mounted magnets on both rotors. One of these rotors has the capacity to rotate with respect to the other, in order to reduce the flux or completely short the flux path by misalignment of rotors. The machine stator is exactly like the conventional PMSM. The machine is capable of reducing the induced emf to zero by field weakening. <br/><br/>In this thesis a transient 3D finite element model is presented to test the credibility of the machine. A 2D FEM of a conventional PMSM was also built to check the validity of the machine. It is seen that torque is a function of the active length of the machine, and if < a gap is introduced between the rotors then the total length of the machine must be increased. Also, axial flux component which induces eddy currents in the stator teeth was studied. By modeling anisotropy in the stator iron, certain hot spots could be seen in the middle part of the stator. The forces that were in the shifting mechanism were studied and it was concluded that machine cogging can be reduced to reduce the effect of these forces. A machine prototype was also built which confirms the field weakening capability of the machine. <br/><br/>The DRPMSM works like a conventional PMSM but with flux weakening capabilities and can be implemented on marine and wind turbine applications for these type of fault conditions.LFEM; FEM analysis; PMSM; stator faults; field weakening; COMSOL Multiphysics)uuid:2fbfb0a9ce2c4b8b997e0c7df7216031Dhttp://resolver.tudelft.nl/uuid:2fbfb0a9ce2c4b8b997e0c7df7216031~Modelling construction phases of bored tunnels with respect to internal lining forces: A comparison of Finite Element Programs^kunst, David (TU Delft Civil Engineering and Geosciences; TU Delft Geoscience and Engineering)Broere, Wout (mentor); Safari, Bahram (mentor); Vardon, Phil (graduation committee); Blom, Kees (graduation committee); Delft University of Technology (degree granting institution).
Areas are getting more and more populated causing new infrastructure lines to be constructed below the surface. A bored tunnel is one of the possibilities to create this subsurface infrastructure, but the construction process of a bored tunnel is a complicated one. Many loads and aspects are present in this construction process that can be divided into six phases. In each of these phases, different loads and aspects are acting on the tunnel lining or the surrounding soil which can cause the lining to deform. <br/><br/>The increasing complexity and demands of problems have led to the use of the finite element method. A computer based method which allows one to model the problem.<br/><br/>For finite element modelling, numerous programs are available of which several claim to be able to model bored tunnels. However, it is not yet clear what the exact differences between the different programs are. With many aspects to be modelled, many differences between programs occur, either in the soil, the tunnel lining or a combination of both.<br/><br/>This research has focussed on the possibilities of modelling the different construction phases of bored tunnels in two widely used programs: DIANA and Plaxis. Simple two dimensional (2D) models were created to which the different construction phases were added before continuing with three dimensional (3D) modelling. This approach has led to a good assessment of the possibilities and limitations within these two programs. <br/><br/>DIANA is not yet suitable for modelling the construction process of bored tunnels completely. The construction phases are modelled undrained to account for the relative short time they are acting. A consolidation phase in which the pore pressure can dissipate cannot be modelled in DIANA, which is essential for modelling the construction phases.<br/><br/>Plaxis, on the contrary, is not able to model joints in the segmental lining appropriate for 3D. In 3D, Plaxis only allows to model a joints as "fixed" or "free". In DIANA different theories can be applied to the joints, including Janssens. For 2D, both programs have a rotational springs besides the free and fixed connection for modelling the joints.<br/><br/>For the model in which the material models were changed, the difference with the main impact between the two programs occurred, especially for the bending moment. This means the Modified MohrColomb material model in DIANA is different than the Hardening Soil model in Plaxis.<br/><br/>Including the construction phases leads to more favourable internal lining forces for tunnels, something of which clients should be convinced. However, not until the models have been benchmarked with measured data from a tunnel project. <br/><br/>While 3D models have been investigated in < this research, they should be extended in order have a better understanding of the different 3D phenomena that are present in the construction of bored tunnels. This will both assess the possibilities of modelling this process and more potential differences between programs can be investigated.<br/><br/>Besides extending the 3D models, other programs should be investigated on their capabilities too. In order to come to a proper assessment of the possibilities, program experience is strongly recommended. These programs should also be compared with measured data for benchmark purposes.)Tunnelling; FEM; Lining Forces; ModellingGeoEngineering)uuid:2446d8cfbdc14ae89a9a398bb1bc6636Dhttp://resolver.tudelft.nl/uuid:2446d8cfbdc14ae89a9a398bb1bc6636mFatigue assessment in finite element analysis: A postprocessor to FEA output for hot spot stress calculationSwierstra, E.P.bFrissen, C.M. (mentor); Hendriks, M.A.N. (mentor); Veljkovic, M.V. (mentor); Pavlovic, M. (mentor)p
For the fatigue assessment of welded structures, several design methods are described by the design codes of IIW, Eurocode3 and DNV. The relation between the stress range and cycles to failures were derived from experiments: the SN curves. With the increased accessibility of finite element software to engineers, a more flexible approach emerged: the socalled hot spot stress method. Particularly suitable for welded structures, it assesses the influence of the geometric discontinuity on the stress distribution. A stress extrapolation procedure is required to overcome the high stresses computed by FEA at the notch. Normal stresses at the surface, perpendicular to the weld, are to be used. For curved welds and surfaces, e.g. in case of tubular joints, these stresses are complex to determine from FEA output. A method that automates the hot spot stress calculation as a post processor to FEA output would facilitate the process. Such an automated subroutine would further enable a study on the finite element modelling aspects, including the use of shell and solid elements and the inclusion of the weld profile, in relation to conducted fatigue experiments. This report describes the development of a subroutine as postprocessor for FEA output to calculate the hot spot stresses. Read out points for stress extrapolation are located independently of the finite element mesh. In addition, for each weld node the local coordinate system is to be determined and subsequently the corresponding stress transformation is to be performed. Equivalent stresses at the read out points are determined by means of interpolation from a triangleshaped plane formed by three element nodes. Cutout specimens of an orthotropic bridge deck were tested against fatigue and strain gauges were used to measure the strains. This report shows that FEA stresses corresponded well with the measurements. Inclusion of the weld profile is important; ignoring the weld underestimates the stress levels by 10%. Use of shell elements resulted in 4% lower nominal stresses than solid elements, however in the weld region only the solid element model accurately reproduced the stress distribution. An alternative method for the fatigue classification described in EC3 is proposed, which represents better the observed stress levels for the crack initiation point at the weld root. Finally, this report considers stress concentration factors of tubular joints as recommended by CIDECT design guide. The FEA results are compared to the SCFs from parametric formulae. Good correspondence was found between the FEA and CIDECT results. A validation analysis of the boundary and loading conditions was performed, from comparing the joint model with the entire truss structure for shell elements. A correction function is derived to cover the small observed differences. Additionally, strain gauge measurements from experiments on large scale tubular joints in a marine environment are compared to the FEA results. Good correspondence was found between the measured and numerically computed strains. For solid element models, the weld leg size is fou< nd to be important for the hot spot stresses; each millimetre shift of the weld toe affected the stress levels by 3%. A characteristic SN curve was derived from the experiments. Fatigue assessment by means of the FEA hot spot stress in combination with the corresponding DNV SNcurve was found to be more conservative.;fatigue; FEA; FEM; hot spot stress; finite element analysis!Civil Engineering and Geosciences)uuid:3cf25e8e397c4aa5a728e07ea881bd3cDhttp://resolver.tudelft.nl/uuid:3cf25e8e397c4aa5a728e07ea881bd3c{The influence of the Transition Zone on the structural behavior of pin connected areas in local metal reinforced composites$Puzio, Tomek (Aerospace Engineering)rPetersen, Enno (mentor); van Campen, Julien (mentor); Delft University of Technology (degree granting institution)Fibre Metal Laminates (FML) are hybrid composites, with the attempt to combine the advantages of metals and fibre reinforced plastics. Their promising properties are used locally in joining areas to reduce the structural weight. As the metal foils density, in this case a steel alloy, is much higher than the density of carbon plies, its amount should be kept minimal. Hence, the replacement of the laminas is done gradually creating a so called Transition Zone (TZ). <br/><br/>In this research, the focus is given to the influence of the TZ on the structural behavior in pin connected FMLs. In the investigation two different designs of TZ and two different starting positions of TZ (closer and further from the pin) are considered. First their effect on the laminates behavior is investigated with static bearing tests accompanied by Digital image Correlation (DIC) measurement, followed by a Finite Element Analysis for an indepth look at the laminas behavior. Later includes the implementation of the Cuntze failure criterion for damage prediction. The studies revealed that the distance between load introduction and start of the TZ can be very short without affecting the load carrying capacity.XFEM; FML; Fibre Metal Laminates; Transition Zone; Digital Image Correlation; Pin Bearing
20200707)uuid:010174b9fb1d4956965697767b54ca68Dhttp://resolver.tudelft.nl/uuid:010174b9fb1d4956965697767b54ca68zCalculation Methods for Steel Joints: Comparative Study of European Design Regulations and Partial Finite Element AnalysesMvan Egeraat, Hugo (Civil Engineering and Geosciences; Structural Engineering)Veljkovic, Milan (mentor); de Vries, P.A. (mentor); Pasterkamp, S. (mentor); Hendriks, M.A.N. (mentor); L.J.M., Houben (mentor); van Lammeren, T. (mentor); Delft University of Technology (degree granting institution)style="margin: 0cm 0cm 0pt; lineheight: normal; msolayoutgridalign: none;">Traditionally, steel joints are calculated by the calculation rules described in the Eurocode 3: NENEN 199318. Effective lengths are important parameters to determine the different resistances of the components in the steel joint. Finite Element Analyses (FEA) are becoming increasingly important in engineering, including in construction industry. Specialised software is developed to determine the stresses and corresponding strains in the plate elements of the joints by the Finite Element Method (FEM). This thesis reports on a comparative study of the traditional calculation method and a method which is using partial FEA for determining the resistance of joints. The approach, assumptions and principles used for these calculations are explained in this report. It will be investigated whether the same components of a joint are decisive for each method and if there are differences in joint resistances. If so, the magnitude of the difference will be determined as well. This is done for different simple shear joints (SSJ) andmoment resisting joints (MRJ). For the last group, two joint configurations (Flush End Plate Joint and Extended End Plate Joint) are calculated manually, partially modelled with the FEM, and compared with the results of executed experiments. <br/></p><p style="margin: 0cm 0cm 0pt; lineheight: normal; msolayoutgridalign: none;"/><p style="margin: 0< cm 0cm 0pt; lineheight: normal; msolayoutgridalign: none;"Steel Joints; Simple Shear Joint; Moment Resisting Joint; FEM; FEA; WALDO; Eurocode 3; Component Method; Comparative Study; Extended End Plate Joint; Flush End Plate Joint; SSJ; MRJ)uuid:89a15968c6594939ac9b1b487c9a976bDhttp://resolver.tudelft.nl/uuid:89a15968c6594939ac9b1b487c9a976bFNumerical modelling of dowelled connections in Laminated Veneer LumberLJanssens, Steven (Civil Engineering and Geosciences; Structural Engineering)Rots, Jan (graduation committee); de Vries, Peter (graduation committee); Hoogenboom, Pierre (graduation committee); Li, Minghao (mentor); Ottenhaus, Lisa (mentor); Delft University of Technology (degree granting institution)The complex mechanical behaviour of timber makes it hard to predict the failure modes in connections made of timber in Finite Element Models (FEM). The combination of various failure modes (brittle and ductile) , anisotropic behaviour, contact of steel elements and large deformations that can occur in a timber joint challenges the use of FEM. To this date no widely used approach is available for the modelling of timber connections. This knowledge gap impedes the use of large timber connections for high rise buildings in seismic regions like New Zealand. For tall seismic resilient structures a profound understanding of the various failure modes of a connection is needed to guarantee a safe design. In this thesis a new model approach with the use of cohesive elements to simulate cracking is investigated for the prediction of the mechanical behaviour of connections. An embedment test simulation is a logical step towards this connection model.<br/><br/>Timber can be characterised by its strong longitudinal fibres and the lignin that forms the bonding between the fibres. This anisotropic structure of the material results in a strong and stiff parallel and a weaker perpendicular behaviour of the material. Timber reacts ductile to compression loading and brittle in tension and shear loading. A typical crushing action of the timber (with micro cracking and densification of the timber) occurs when the maximum compression parallel to the grain stress is reached. <br/><br/>The specific manufacturing process of Laminated Veneer Lumber (LVL) reduces the inhomogeneous character of timber. This improves the strength and the predictability of the material. The cracks that occur in tension and shear can cause four different brittle failure modes in a dowelled connection (row shear, group tear out, failure of the net cross section and tensile splitting). A brittle failure mode can be prevented when minimum end or edge distances and spacing between fasteners are satisfied. In that case a ductile failure is expected with plastic deformation of the dowel and crushing of the timber underneath the dowel.<br/><br/>FEM is a powerful tool that is able to solve complex partial differential equation problems. Its basis lies in the linear formulation of small elements that are linked by coinciding nodal degrees of freedom to form a structure. The linear formulation has limited validity and a failure criteria is needed to define the onset of nonlinear behaviour. Multiple nonlinear approaches are available to accurately simulate the complex behaviour of timber in connections. The most promising approach is the use of cohesive elements at the locations where cracks are expected. The anisotropic nature of wood makes the prediction of crack locations in connections possible. The cohesive elements have a damage formulation to simulate strength and stiffness loss after the material strength is reached. This softening model hinders the solution procedure and therefore special solution techniques (e.g. line search, automatic stabilization and viscous regularization) are employed.<br/><br/>A first model is made to simulate the embedment behaviour in LVL. In the embedment tests conducted by Franke and Quenneville a steel dowel is pushed in a timber block with a predrilled hole. In the translation of this test to an accurate FEM model three nonlinear pheno< mena are simulated (cracking, crushing in compression and contact). The cracking behaviour in tension and shear is modelled with cohesive elements with a damage formulation. These cracks are inserted at the location of potential crack growth. The remaining timber has a trilinear isotropic plastic hardening formulation to accurately predict the deformations in the LVL under compression loading. The last nonlinear phenomena is contact between the steel and the timber. This is simulated as "hard" contact in normal direction and frictional contact in tangential direction. <br/><br/>The implicit solver encountered difficulties in converging due to contact alterations (chatter) and the softening behaviour in the cohesive elements. The automatic time incrementation algorithm reduced the increment size to overcome these difficulties. The analysis resulted in a load displacement curve that had good agreement with the experimental curve. A parameter study proved that the small difference can be related to the natural variation of material properties.<br/><br/>The approach of the embedment FEM was implemented in a more complex connection model. The connection tests conducted by Ottenhaus et al. that is simulated consists of 4 dowels that connect two outer LVL blocks with an inner steel plate. The spacing was chosen in such a way that a ductile failure mode was expected with brittle failure modes at large deformations. In the connection model plasticity in the steel dowels, the size of the specimens and the inclusion of tension parallel cracks increased the complexity of the model. This increased the convergence difficulties and the analysis ceased (at 0.43 mm) before the maximum load was reached .<br/><br/>A study was made to improve the stability of the numerical solution procedure. The impact of changing the formulations of cohesive elements, contact and the solution procedure on the convergence is tested. The viscous regularization and the initial dummy stiffness of the cohesive elements had the most influence on the convergence. With increased viscous regularization the implicit solver becomes more stable and computes more displacement increments (up to 6.91 mm). However, viscous regularization introduces artificial forces that significantly decreased the damage evolution. This prevented the formation of brittle failure mechanism.<br/><br/>By reducing the initial dummy stiffness of the cohesive elements (down to 2 times the timber element stiffness) the convergence improved significantly. With this initial cohesive stiffness the global softening behaviour (up to 10.08 mm) and failure development that are observed in the experiments could be simulated. The failure development consisted of the formation of plastic hinges in the dowels, tensile splitting and finally row shear failure that completely removed the supporting action of the timber under the dowels.<br/><br/>The decrease of cohesive element stiffness has impact on the effective stiffness of the adjacent timber elements and decreases the accuracy of the model. The model needs to be improved to make the predictions of the brittle failure development more accurate. With arclength control, an explicit solver or the sequential linear analysis method the convergence might be increased, without the accuracy loss that is attributed to cohesive stiffness decrease. Further research is needed to improve this connection model approach.DCohesive Zone Model; Timber; FEM; Laminated Veneer Lumber; Nonlinear)uuid:b012a2e87ae04b26aed88c32df1aff6eDhttp://resolver.tudelft.nl/uuid:b012a2e87ae04b26aed88c32df1aff6ecStrain Rate Dependen 3Point Bending Test and Simulation of a Unidirectional Carbon/Epoxy Composite Righi, R.Kassapoglou, C. (mentor)In order to use composite materials in automotive production while ensuring that passengers safety it is crucial to fully understand the strain rate effect on their mechanical properties.This study implements a strain rate dependent 3point bending test setup for a high rate servohydraulic testing machine. A finite element model to simulate strain rat< e dependent 3point bending tests has been created and used for the validation of material cards that consider strain rate dependent material properties.The test setup developed allows the correct characterisation of the strain rate dependent 3point bending tests. The study also demonstrates that strain rate effects can be successfully considered in finite element simulations._Strain rate; 3point bending; impact; FEM; material card; simulation; digital image correlation
20220320 Aerospace Structures & Materials)uuid:01b37bf697da423b9d47a3623d03b201Dhttp://resolver.tudelft.nl/uuid:01b37bf697da423b9d47a3623d03b201UA Practical Application of Topology Optimization for Heat Transfer and Fluid DynamicsScholten, T.C.van der Kolk, M. (mentor)Topology optimization is widely used within the academic environment. It is however not yet a standard design tool within the commercial industry. My research aims to shorten this gap by applying a topology optimization for an industrial design load. The design load is from a Printed Circuit Assembly (PCA) that requires active cooling in order to function within specification. The PCA is cooled with a water cooled plate. The topology optimization is used to find the optimal distribution of the cooling channels such that optimal cooling is provided. The first part of my research describes a conceptual design for the cooling of the PCA. The thermal behavior of the design is predicted with a Finite Element analysis and the results are verified by means of an experimental measurement setup. The second part is the practical application of the topology optimization. The topology optimization is applied to the heat transfer and fluid dynamics that govern the behavior of the cool plate. Multiple water inlet and outlet positions are considered. A comment is given on which is the best performing design. An experimental measurement setup is created with the optimized design, and the difference in performance between the optimized and the baseline design is measured.WTopology Optimization; Fluid Dynamics; Heat transfer; ASML; Prototype; Measurement; FEM.Mechanical, Maritime and Materials Engineering,Precision and Microsystems Engineering (PME))uuid:b0ca8953de6f49b196923e7bb1b1f687Dhttp://resolver.tudelft.nl/uuid:b0ca8953de6f49b196923e7bb1b1f687nHomogeneous Orthotropic Masonry Material Model: Research, development and implementation for explicit analysisAukselis, A.hRots, J.G. (mentor); Hendriks, M.A.N. (mentor); Yang, Y. (mentor); Hoorn, H. (mentor); Koot, A. (mentor)The Groningen region, in the Netherlands, experiences earthquakes since 1986. These earthquakes are new to the region and the structures built there are not designed for it. Therefore, they pose a great risk for the historical structures and people living in the area. Most of the buildings there are built using masonry and to analyze such structures on how they will be affected by earthquakes using currently available tools and methods is rather complicated. In this report, the author investigates the use of available continuum damage mechanics models for the purpose of simulating orthotropic masonry behavior during an explicit integration analysis. The material behavior is described in Fortran programming language and is used as a custom user subroutine (VUMAT) in Simulia Abaqus finite element analysis software. The developed material model exhibits 3D elasticity and 2D plane plasticity. Furthermore, it is assumed that two general failure mechanisms are present. One associated with tensile and shear brittle fracture represented by Rankine type yield surface and other with distributed crushing of a material represented by Hill type yield surface. The model exhibits uncoupled damage evolution in the tension regime and coupled in compression. Additionally, the model supports tensile crack closure, while in compression it accumulates the plastic deformations and if an element is crushed it can be flagged for deletion from the mesh. The model is formulated in such a way that most of the properties in material directions are i< ndependent of one another. The developed model was tested by examining its behavior in analyses where numerical models were composed out of one or few elements. Additionally, for experimental comparison, four shear walls were modelled, three subjected to monotonic loading and one to cyclic. The analyses closely agree to experimental results even when using raw test data. The material model is stable due to the explicit approach and provides qualitative results as it is flexible enough to be used for various types of analyses, either static or cyclic.In the final part of the report, further developments are considered, including improvements to the code base, additional testing, and development of a custom element.Wmaterial model; Masonry; FEM; damage mechanics; earthquakes; Groningen; Fortran; Python)uuid:26b0b336527a43a8a98f9cc7555765e7Dhttp://resolver.tudelft.nl/uuid:26b0b336527a43a8a98f9cc7555765e7JStructural Damage to Masonry Housing due to EarthquakeFlood MultiHazardsKorswagen Eguren, P.A.FJonkman, S.N. (mentor); Molenaar, W.F. (mentor); Terwel, K.C. (mentor)
The possibility of multihazards, the occurrence of two or more (natural) hazards at once or shortly after another in the same location, can lead to an increased risk of structural damage and life loss. In the Netherlands, seismicallyunprepared houses are especially vulnerable to newly expected earthquakes in the region of Groningen. These seismic events have the potential to compromise levees in the area, in a way that can lead to flooding. The flood, in combination with its triggering earthquake, are the multihazard that is closely studied in this report; damage is assessed to typical unreinforced masonry houses standing close to the aforementioned levees in the Groningen area. In the study, a framework is introduced to analyse damage and its probability for a study case, which consists of a house with longitudinallyoriented precast hollow concrete slabs resting on 100mmthick calciumsilicate loadbearing masonry walls, and longitudinal infilled masonry walls. This house is located behind a levee, for which the failure probability due to earthquakes has been characterised by the study of Zuada (2014). First, earthquake damage is assessed by obtaining the lateral displacement of the house in response to the earthquake s peak ground acceleration via a finite element model and a nonlinear time history analysis. And, relating the computed displacement to the amount of cracking and cracked walls as observed from a generated pushover curve that depicts loss of lateral resistance against lateral displacement. For each possible damage state of the house, a set of parameters that describe its weakening is defined. Then, the impact of various flood actions are analysed on the potentially weakened structural cases. Firstly, the flood resulting from a levee breach is studied with a FEM hydraulic model in order to obtain the probable flood depth and flow velocity, related to initial probabilistic parameters for the water level and the characteristics of the breach. Secondly, the interaction of debris (such as trees and vehicles) with the flood and the structure is studied. Then, the loads generated by the flood and the potential impact of debris are evaluated on a nonlinear FEM of a wall of the house for an appraisal of damage. Finally, the probability for the house to be in a particular damage state as a result of the earthquake is computed and joined to the probability of the flood further damaging the house and the failure probability of the levee. From this, fragility curves are elaborated detailing the probability of damage as a function of earthquake ground acceleration. For a period of fifty years, the risk of structural collapse for the case study house was computed at 1/25. The impact of debris was observed to a be an often overlooked flood action with a paramount influence on structural damage. For the medially intense flood due to a levee breach with a water level difference of around two meters, all collapse cases due to flood actions were due to debris i< mpact. Severe earthquake damage was observed to be a result of the infilled walls that contribute little to the structural resistance of the house, as well as the lack of redundancy and ductility of the structure. The influence of the multihazard on the risk of individual loss of life was also investigated and seen to increase from 4.2104 for earthquakeonly analyses to 9.1104 per year for an earthquakeflood multihazard. Clearly, multihazards are both structurally damaging and dangerously threatening to human life._earthquake; flood, masonry; framework; probability; damage; fragility; FEM; Maple; multihazardHydraulic Structures53.228592, 6.619579)uuid:b4f6ce8eeabf46df84f02206dbd1b6b5Dhttp://resolver.tudelft.nl/uuid:b4f6ce8eeabf46df84f02206dbd1b6b50Local Buckling and Collapse of ThickWalled pipeHuiskes, S.W.G.Keijdener, C. (mentor)Heerema Marine Contractors is an offshore contractor who specializes in the installation and removal of a range of offshore facilities. This includes the installation of submarine pipelines in excess of 1500 [m] water depth. Higher water depths drive the pipeline designs to increase wall thickness. Another motive to apply a low D/t ratio is to incorporate corrosion allowance, such that the wall thickness is still sufficient after the lifetime has expired. A good understanding of the challenges of thick walled pipeline behaviour during installation can be of great benefit to Heerema Marine Contractors. This thesis will focus on the buckling behaviour during J lay of steel submarine pipelines with a D/t ratio lower than 20 (from here on referred to as thick walled). During design the DNV formulas for collapse and local buckling are used. Existing research shows conservatism in the pure collapse DNV formula for thick walled pipe.aDNV; Local Buckling; Collapse; sagbend; FEM; FEA; Heerema; thick walled pipe; offshore; pipelines
20211208!Offshore and Dredging Engineering)uuid:43544d87e4194765a4bd8b141d393b19Dhttp://resolver.tudelft.nl/uuid:43544d87e4194765a4bd8b141d393b19]Dynamic response analysis of a spar floating wind turbine in level ice with varying thicknessTsigkris, E.SMetrikine, A. (mentor); Keijdener, C. (mentor); Ghao, Z. (mentor); Shi, W. (mentor)The wind energy industry in order to find stronger winds, has to go further offshore and move into deeper waters where bottom founded wind turbines cannot be deployed anymore. This is the main reason why floating wind turbines have been studied extensively in the past years. In the case of regions with cold climates, ice loads become significant and have to be taken into account when designing an offshore structures like an offshore wind turbine. As soon as this strong background on ice is founded through extensive literature study, a set of existing measurements of level ice from the ARISE expedition that took place in Antarctica in East 2003 was used in order to formulate a random varying thickness ice field. This is achieved by constructing a tool which based on the spectrum from the existing measurements, a new random varying ice thickness floe is generated. An existing model that considers constant ice thickness floes was updated in order to account for varying thickness fields. This was accomplished by modelling the ice floe as an Euler Bernoulli beam of varying cross section. It is noticeable to mention that ice fails in an arc shaped wedge. An FEM numerical model was implemented in FORTRAN that accounts for the variations in thickness. Moreover, beam elements of different widths were used in order to build up an approximation of the arc shaped wedge. By coupling the FORTRAN code with the aeroelastic code HAWC2, the effect of the varying thickness ice field is compared with the constant ice thickness floe. The results obtained generally revealed a decrease in the ice loads when a varying ice field is considered. Moreover, it is observed that the varying ice thickness field introduces a more dynamic effect on the structure, especially for the low drifting speeds. As soon as aerodynamic loads are also included< , then it is also noticed that the combined wind and ice loads, give rise to frequencies different from the ones only the ice loads excite.offshore wind energy; spar floating wind turbine; iceloads; response analysis; level ice; varying thickness; FEM; EulerBernoulli beam theory)uuid:ec1fecb68e3f4207aea8b9f4318d0330Dhttp://resolver.tudelft.nl/uuid:ec1fecb68e3f4207aea8b9f4318d0330Combining existing independent seismic reinforcing methods for clay brick masonry: Knowledge development of the behaviour of reinforced masonry by using Finite Element ModellingMeulman, E.wRots, J.G. (mentor); Hoogenboom, P.C.J. (mentor); Van Beek, A. (mentor); Trkmen, . (mentor); Hermans, M.J.M. (mentor)In the last decades induced earthquakes are taking place more frequently in Groningen. This is due to gas extraction form the soil. Buildings are damaged by the earthquakes and building collapse is possible in the near future. Houses in Groningen are commonly build up out of single leaf masonry cavity walls and are not designed for earthquake loads. Oosterhof Holman and SealteQ Group have designed a masonry reinforcing method that is called QuakeShield. QuakeShield is an unique reinforcing method and consists out of a combination of two existing independent seismic reinforcing measures. These two existing independent seismic reinforcing measures are: NSM FRP strips and an EB FRP layer. Carbon strips are placed in vertical grooves in the masonry which are filled with a ductile adhesive to bond the strips to the masonry (NSM FRP strips). A polymer or cementitious base layer with an embedded polymer or carbon mesh is attached to one side of the masonry on the outer surface (EB FRP layer). Both reinforcing measures increase stiffness, strength and ductility of the masonry. These three factors result in an increase in earthquake energy absorption and dissipation of the masonry. Which is important when reinforcing houses and buildings to prevent collapse due to earthquake loads. In this project a FEM model is made based on a three point bend test (outofplane bending) performed on QuakeShield reinforced masonry samples. The FEM model is used to develop knowledge about the effect of combining two existing independent seismic reinforcing measures as used in the QuakeShield masonry reinforcing method. The FEM model is a 3D model with a simplified micromodel approach for the masonry. The bricks are solid elements, the reinforcing materials are shell elements and the mortar and the ductile adhesive are interface elements. The bondslip behaviour of the ductile adhesive has a significant contribution in the behaviour of QuakeShield reinforced masonry. The mechanical properties of the ductile adhesive determines mainly the pre and post peak behaviour of the reinforced masonry. Providing gradually decline in load bearing capacity after the peak load. The EB FRP layer has a significant contribution to the reinforced masonry in the displacement range from the initiation of the first crack in the masonry till the onset of yielding of the EB FRP layer. In this range the EB FRP layer is the dominant reinforcing measure. After yielding of the EB FRP layer the NSM CFRP strip becomes the most dominant of the two. The EB FRP layer also provides cohesion between the individual bricks, keeping the masonry wall together after severe cracking has taken place. The FEM model is also used for a configuration analysis to research different geometrical and material variations of the QuakeShield masonry reinforcing method. The configuration analysis gives more insight in the behaviour of reinforced masonry. For the configuration analysis two independent seismic reinforcing measures, NSM FRP strips and EB FRP layer, are applied separately to the FEM model. This is done to investigate its individual effect on the behaviour of reinforced masonry. Strip spacing has a significant effect on the load bearing capacity. If an epoxy is used as adhesive, which is much stronger and stiffer than the adhesive used by QuakeShield, an increase in load bearing capacity is achieved bu< t also sudden failure after the peak load is observed. This is an undesirable failure mode and reduces the total energy that the reinforced masonry can absorb. Results of the different configurations used for the EB layer show that the polymer (PU) base layer has the most significant contribution of the used EB FRP layer materials when considering overall ductility and energy absorption of the reinforced masonry.6Earthquake; QuakeShield; FRP; FEM; Reinforced masonry&Materials Engineering and Applications)uuid:0c15a53a731748c99d8e941963ca651bDhttp://resolver.tudelft.nl/uuid:0c15a53a731748c99d8e941963ca651buInducible Displacement of a Knee Implant: A finite element study and validation of a loose and fixed tibial componentVan Wolfswinkel, G.HValstar, E.R. (mentor); Zadpoor, A.A. (mentor); Blankevoort, L. (mentor)Introduction. Aseptic loosening is indicated as the main cause of knee implant failure. Despite all currently used techniques, it remains challenging to diagnose an aseptic loose knee implant. A promising technique to reveal aseptic loose related implant motions is inducible displacement (ID). ID measurements are used to detect implant motion relative to the bone. To diagnose a loose implant via ID, motion thresholds are required. Such thresholds are dependent on a number of subject specific factors including bone material, loading conditions, used implant and interface contact properties between implant and bone. Such thresholds do still not exist. As a first step towards subject specific motion thresholds, a finite element (FE) model can be used to investigate the factors affecting ID. Objective. To setup and to validate a finite element model that can be used to simulate inducible displacements of a tibial component of a knee implant. Method. As a basis for the finite element modelling, a previously performed experimentally study was used. This study provides data and material to build two finite element models. One model represents an aseptic loose (i.e., silicone layer between implant and bone) tibial component and a model represents a fixed (i.e., cemented) tibial component. FEmodels were based on quantitative computed tomography (QCT) scans of the cadaveric tibiae. The experiments were simulated on the FEmodels and the ID compared to the experimentally determined ID. Inducible displacements were expressed in terms of rotations and translations. Sensitivity analyses were performed in order to investigate the effects of assumptions during the modelling process on ID. The following assumptions were analyzed; bone material properties, load application points, interface contact properties, silicone layer stiffness and cement material properties. Results. Loose implant; translations due to top implant loads were found in good agreement to the experimental translations. FE determined rotations were considerable higher. Rotations and translations due to side implant loads were considerably less in the FEmodel. Fixed implant: No clear agreement was found after comparing experimentally and FE determined displacements in the cemented implant model. A sensitivity analysis reveals that the implementation of interface interaction properties led to a considerable reduction of the error between experimentally and FE determined ID. A sensitivity analysis reveals also that experimental loading conditions were not correctly applied leading to a considerable increase of implant rotations. Effects of variations of bone material properties on ID are found negligible. Conclusion. Two FEmodels were build. A model representing a loose implant and a model representing a fixed implant. This study shows that: i) The implementation of interface interaction properties contributes to a considerable improvement of realistic FE determined ID. ii) Experimental data used to validate FEsimulations should be sufficiently accurate to analyze a cemented implant and be suitable to implement in a FEmodel. iii) Bone material properties have a small influence on ID and might be implemented in a simplified way. Further research is required to < optimize the validation of the FEmodels.Minducible displacement; FEM; knee implant; total knee replacement; validationBiomedical EngineeringTissue Biomechanics & Implants)uuid:273a0318d8be4448b4e2310a4c6a297aDhttp://resolver.tudelft.nl/uuid:273a0318d8be4448b4e2310a4c6a297afThermal Characterization of StructureIntegrated Thermal Subsystems based on the MASCOT Landing ModuleRagupathy, A.P./Zandbergen, B.T.C. (mentor); Lange, M. (mentor)A
Accurate thermal characterisation of composite structures can help structural designers in predicting thermal paths in a spacecraft structure and assessing the effect of modifying materials on the structure s overall thermal performance. Existing spacecraft thermal analysis software lack the ability to model anisotropic thermal properties of composite materials. This in turn leads to inaccurate prediction of their thermal behaviour. The thesis describes the applied modelling methods and assumptions that are used to simulate the thermal characteristics of the MASCOT Landing Module s (LM) composite structure. MASCOT is a 10 kg shoeboxsized lander platform developed by DLR in cooperation with CNES and JAXA for the Hayabusa 2 sample return mission from the asteroid 1999JU3. The MASCOT LM structure s framework walls are made from a Carbon Fibre Reinforced Polymer/Foam sandwich. The M55J fibres used for the unidirectional sandwich face sheets are of Polyacrylonitrile (PAN) type and have high stiffness and strength properties, but poor thermal conductivity. Also, the glued connections between the framework walls are realised with PAN fibre patches. This is one reason, which necessitated a thermal subsystem consisting of heat pipes and a radiator. Both contribute with a total mass of 450 g, almost the same as the structural mass (550 g). Also, the structural design is itself influenced by the needs of the thermal subsystem. The modelling is carried out using Patran whereby methods to develop a thermal finite element model from the existing structural model are assessed and steady state analyses are carried out. To decrease the computational effort for radiation simulation, a novel method of developing radiation shell elements which are overlaid on the solid elements in the structure is described. Subsequently, the results from the finite element simulations are compared to actual temperature measurements, which were performed in a thermal vacuum chamber. The model is correlated with the test results and the method adopted is validated. The next phase of the thesis work involves the use of the developed thermal model to assess solutions for integrating the thermal functions within the LM structure. As a first step, the heat pipes are removed. The impact of the removal of the heat pipes on the LM is assessed and various design solutions are proposed for the MASCOT LM. From the simulations, it is concluded that it is indeed possible to remove the heat pipes from the LM and that a structureintegrated thermal subsystem can be achieved by introducing conductive interfaces in the structure.$thermal; composites; spacecraft; FEM
20190126Space Systems Engineering)uuid:6011108fcd5a4effb84fc38d3f8ed35eDhttp://resolver.tudelft.nl/uuid:6011108fcd5a4effb84fc38d3f8ed35eUEvaluating the acoustoelastic coupling in an industrial gas turbine annular combustor
Scortescu, S.Turteltaub, S.R. (mentor)Macoustoelasticity; gas turbines; structuralacoustic coupling; combustor; FEM
20210101+Mechanics, Aerospace Structures & Materials0Aerospace Structures and Computational Mechanics)uuid:6ce5f7ff578b4be7bb9bfd16e068a9bfDhttp://resolver.tudelft.nl/uuid:6ce5f7ff578b4be7bb9bfd16e068a9bfkDesign and analysis of a semisubmersible floating wind turbine with focus on structural response reduction
Vittori, F.E.)Moan, T. (mentor); Metrikine, A. (mentor)3 Floating structures as spar, semisubmersibles and TLP have been proposed for offshore wind turbines for deep waters (>60m) according to the report of Arapogianni, Moccia, Williams, & Phillips (2011), where bottom fixed substructures are technically a< nd economically not feasible. Several floating concepts have been designed and just some of them were deployed as Hywind (Statoil, 2015) and WindFloat (Roddier, Cermelli, Aubault, & Weinstein, 2010), but still they are prototypes that require further improvements in order to achieve it technoeconomic feasibility. At the Centre for Ships and Ocean Structures (CeSOS) NTNU a braceless concept was developed for deep waters called CSC. This floater consists on one central column supporting the wind turbine and three side columns connected each of them at the bottom to the central one through pontoons. These cantilever columns might induce large dynamic stress at the connection section on the pontoon as well on the cross section closer the central column. The project objective is to propose a structural connection between the central and outer columns at the top avoiding wave loads and check its stress reduction on the pontoon. The design methodology involves a stability analysis using numerical tool from Det Norske Veritas (DNV) Genie and HydroD. The wind turbine from the National Renewable Laboratories (NREL) in E.E.U.U. of 5MW was employed to estimate the loads and workability of the floater. The hydrodynamics analysis is going to be done in frequency domain based just in wave loads. Through the hydrodynamic loads the stresses are estimated assuming rigid body behavior. It estimation are done by EulerBernoulli theory and via Finite Element Method using beams and shell elements. The results show that the upper beams reduce significantly the dynamic axial stress on the pontoon, increasing the floater strength. The FEM using beam elements is a simple and reliable numeric approach to obtain global loads and the stress distribution on the structure. The FEM shell mode could predict the stress for the simplest case but it requires more computational effort in order to set up the mesh model and achieve satisfactory results. The EulerBernoulli method under predict the stress on the pontoons as the whole structure of pontoonbrace does not fulfill the beam theory assumptions./FOWT; wind energy; RAO; FEM; offshore structure
20170717Hydraulic Engineering)uuid:215ed6ef5fcb4366b39eb2706050d580Dhttp://resolver.tudelft.nl/uuid:215ed6ef5fcb4366b39eb2706050d580\Heat transfer enhancement of a permanent magnet synchronous machine used in vehicle tractionSrisankar, V.B.1Polinder, H. (mentor); Van Der Geest, M. (mentor)DOne of the major restrictions that hinder the versatility of electrical machines in any sector is their thermal limitations. This thesis deals with the study of the heat transfer occurring in an outer rotor permanent magnet synchronous machine used in the electric vehicle industry with the aim of exploring possibilities to reduce the hotspot temperature. The project is in collaboration with eTraction, an electric vehicle systems designer. A 3D numerical model of the machine is designed using the Finite Element Method (FEM) with heat transfer coefficients obtained from a computational fluid dynamics (CFD) simulation. A closer look at the secondary flow with vortices in curved tubes is also presented as part of the pursuit to estimate boundary conditions required for the FEM model. The equivalent thermal conductivity of the slot region was estimated by a 2D FEM model and the external heat transfer coefficients were represented using empirical relations. The model was validated with experimental tests performed at the eTraction's test bench facility and was found to be sufficiently accurate to predict the influence of material and mechanical design changes on the heat transfer. Results show that by using certain potting materials and making slight changes in the cooling region, hotspot temperatures can be significantly reduced.>PMSM; FEM; CFD; Heat Transfer machines; Dean Vortices; Potting8Electrical Engineering, Mathematics and Computer Science+DC Systems , Energy Conversions and Storage)uuid:13d032bfbfc64c5f963b6e7981c19911Dhttp://resolver.tudelft.nl/uuid:13d032bfbfc64c5f963b6e7981c19911UEffect of plastic deforma< tion on residual strength of ship structures after groundingZhou, Y.ZKaminski, M. (mentor); Jiang, X. (mentor); Nieuwenhuijs, M. (mentor); Koelman, H. (mentor)RShip grounding decreases the strength of ship hull structures once plastic deformation occurs during the event. In practice of ship societies, current method of determining residual strength of ship hull structures after grounding is to totally remove the plastically damaged parts. As plastically deformed part of ship hull structures might still contribute considerable amount of strength, the method of total removal might be overly conservative. The article is oriented to quantify the residual strength of ship hull structures after grounding according to varied levels of plastic deformation. Literature study indicates that most of studies are focused on longitudinal residual strength of damaged ship structures, and transverse residual strength is rarely researched. Hence, it is target to study transverse residual strength after grounding damage, with implementation of a joint study of test and finite element simulation. The experiment gives validation to finite element models, and then an empirical formula can be derived by a series of FE simulations with the verified finite element model.vFEM; experiment; residual Strength; grounding; buckling; ultimate Strengt; elastic Strength; digital Image CorrelationMarine & Transport Technology)uuid:d10408eaeeb945dd83e5bc7139457990Dhttp://resolver.tudelft.nl/uuid:d10408eaeeb945dd83e5bc7139457990/Structural behavior of pressure locked gratingsVan Reekum, R.B.)Abspoel, R. (mentor); Feijen, M. (mentor)Pressure locked gratings have many uses, both on land and at sea. This is mainly due to the high degree of flexibility in dimensions and load bearing capacity. Despite the many uses in our surroundings, the term pressure locked grating is unknown to many. This term refers to the way in which the most important connection in pressure locked gratings is manufactured. Pressure locked gratings are galvanized and/or coated to prevent corrosion, galvanization is almost always used. This thesis is primarily focused on the behavior of galvanized pressure locked gratings. A pressure locked grating is made up of three type of bars: load bearing bars, cross bars and support bars. The connections between the load bearing bars and the cross bars are realized by pressing the cross bar into premade notch in the load bearing bar. The bars will deform plastically, which results in a connection based only on friction. This connection is called a pressure locked connection. The load bearing bars serve primarily for load transfer in one direction. The pressure locked connection weakens the load bearing bars. The cross bars redistribute a local load over the load bearing bars outside of the loading area and reduce the buckling length of the individual load bearing bar. The support bars are spotwelded to both the load bearing and cross bars. Pressure locked gratings are calculated according to RALGZ638, a standard published by the Deutsches Institut fr Gtesicherung und Kennzeichnung e.V. In this standard, pressure locked gratings are calculated on the basis of linear elasticity theory. A calculation according to the EN 199311 is not possible because it is not suited for pressure locked gratings. The main objective of this thesis is to determine if a calculation based on the plasticity theory is possible for pressure locked gratings. Through the application of this theory the design strength can be greatly increased, which has a large economic potential. This research is divided up into four parts that are stated below. Analytical study Experimental study FEM validation Parametric study The vast diversity in size and properties and the complex functioning of the pressure locked connection make pressure locked gratings a difficult product to research. The pressure locked connection also has a big influence on the strength and stiffness. In this galvanizing has a big influence. The analytical study shows that pressure locked gratings fai< l through: local lateral torsional buckling of one of the load bearing bars, global lateral torsional buckling for the entire pressure locked grating or by a mechanism due to a plastic hinge in de load bearing bars. To research the behavior, numerical models were developed in the FEMpackage ABAQUS. To determine the accuracy of these models, experiments were carried out on a number of pressure locked grating geometries. The results of the tests were compared with FEM simulations which made it possible to validate the FEMmodels. The validation has taken place on the basis of four test series. Three test series focused on failure mechanisms, namely: collapse due to a mechanism as a result of plastic hinges in the load bearing bars, test series 1A, collapse due to local lateral torsional buckling, test series 2A and collapse due to global lateral torsional buckling of the entire pressure locked grating, test series 2B. The last test series, test series 1B, is aimed at examining the structural behavior of a common used pressure locked grating. After this validation it is possible to make FEMmodels for a large number of different geometries. The behavior of these geometries can then be analyzed. The validation shows that failure mode and failure load are correctly determined by the FEM models. There is however a notable difference between the stiffness of the FEMmodel and the stiffness of the test specimens. This difference is likely the result of the influence of the pressure locked connection between the load bearing and cross bars. The research shows that all aforementioned failure modes play a role depending on the dimensions of load bearing bars and cross bars. For relatively thickset load bearing bars pressure locked gratings fail due to a mechanism as the result of plastic hinges in the load bearing bars. For slender load bearing bars pressure locked gratings fail as a result of instabilities. With the aid of FEM models, it is possible to estimate the extent in which the plastic capacity is present in actually produced pressure locked gratings. This analysis shows that in 72% of the produced pressure locked gratings, the full plastic capacity of the load bearing bars can be reached to 96% or more. It is however important to keep in mind that, the dimensions of the load bearing bars are determined by deflection or by strength. This is determined by the load bearing bar height and span. When deflection is determining the dimensions of the load bearing bars, a plastic calculation methodology is not useful, because it only increases the design strength. It can thus be stated that the full plastic capacity cannot be fully used. On the basis of this study it is not yet possible to apply a plastic calculation methodology on pressure locked gratings. This is because this research shows that the pressure locked connection can have a big influence on plastic strength. It is not clear if the pressure locked connection always has the same influence on the plastic capacity. It is possible that the plastic capacity is influenced by fatigue, corrosion and manufacturing tolerances.1steel; pressure locked gratings; FEM; experimentsnl
20170316#Structural and Building Engineering)uuid:802993a5b2184b7fa7b49cf5375f7b38Dhttp://resolver.tudelft.nl/uuid:802993a5b2184b7fa7b49cf5375f7b382Preliminary Structural Design for a Hypersonic UAV
Terhes, C.EZandbergen, B.T.C. (mentor); Eggers, A. (mentor); Wijker, J. (mentor)The design and development of a small unmanned aerial vehicle is proposed in order to provide more accurate hypersonic flight data. The outcomes could improve the current shortage of hypersonic flight data and serve to understand and predict how test conditions may be different from actual test flight. Furthermore, the response of the structure and materials due to hypersonic speed will be investigated and stability and control methods during flight will be enriched. To achieve these goals, further investigation of the current configuration of the drone needs to be addressed in order to determine if the proposed structure is f< easible. The vehicle and its mission have been called Hypresearch. The Hypresearch vehicle will be launched at the initial flight conditions of Mach 6 and 42 km altitude and it will selfsustain the hypersonic flight by its own rocket engine, descent and land. Thermalstructural challenges can be quite severe on hypersonic vehicles. Aerodynamic loads (mechanical loads) and aerodynamic heating (thermal loads) can be identified for all the flight stages. Besides, since Hypresearch needs to be introduced at the designated initial flight conditions, a launch system needs be designed or selected. The liftoff phase impose extra challenges, since the aircraft will be launched on the side of a rocket booster and undergo launch loads, such as gforces, vibration, interface loads, not presented during the straight and level flight. After the loads on the vehicle were identified and categorized, the primary and secondary structure was set up using the strength of material and elastic instability approach. The materials selected were MAX phases for the leading edge and nose section, and titanium alloy for the main body. Likewise, titanium alloy was the material preferred for the secondary structure and attachments, as it deals the best with the expected temperature gradients. The following step was the positioning of the internal structure in respect to the constraints set by the project (notrimming conditions during level flight), and the attachments concepts between the airframe and internal units, were proposed. After the initial structural design, the finite element model for the vehicle was set up to be used for the proposed structure s analyses. The undertaken finite element analyses consist of: static, modal, pressure distribution, random and shock effect. The results show that the vehicle s structure is likely to withstand the selected loading environment of the launch vehicle. From this model, the final mass budget of the vehicle s structure was obtained. It was concluded that the structure is considered feasible with regards to the liftoff loads and within the mass budget requirement of a maximum 35 kg. In a nutshell, the graduation project is focused on finding simple solutions to some structural design problems and providing an accurate analysis of the vehicle, in order to confirm the feasibility of the design under investigation./structural design; hypersonic vehicle; FEM; FEASpace FlightSpace Engineering)uuid:5227795e41474d20b058cc3650956556Dhttp://resolver.tudelft.nl/uuid:5227795e41474d20b058cc3650956556uDwarskrachtsterkte van verticaal voorgespannen tandopleggingen / Shear capacity of vertically prestressed half jointsKranenburg, M.C.{Hordijk, D.A. (mentor); Van der Veen, C. (mentor); Hendriks, M.A.N. (mentor); De Boer, A. (mentor); Houben, L.J.M. (mentor)H
The application of prefabricated and usually prestressed concrete elements has increased since mid20th century. These elements are at the point of reaching the end of their life span, are subjected to damages or a change in functionality. Therefore, it is necessary to evaluate their structural safety. In many cases, existing structures do not meet the minimum level of structural safety according to the current building codes. If it is possible to improve the verification of the minimum level of structural safety of existing structures, it is not necessary to take expensive measures like reconstruction or strengthening these structures. For concrete beam elements the structural safety appeared to be in most cases governed by shear resistance. This study specifically investigates the shear resistance of vertically prestressed dapped end beams. An analytical study is performed in order to evaluate the influence of vertically prestressing on the failure mechanism and the shear resistance of vertically prestressed dapped end beams. Next, an analytical calculation procedure based on the equilibrium of the tornoff section is used to determine the bearing reaction of several prestressed dapped end beams. Additionally, a Case Study is performed to verify if the results< of a nonlinear finite element analysis (NLFEA) using a highly simplified model are in accordance with the results described in CURreport 40. In this report the results are described of a full size test on a prestressed dapped end beam. Determining the design shear resistance of vertically prestressed dapped end beams using the equilibrium calculation procedure will give very conservative results. This is caused by the unknown locations of reinforcements and possibly by omitting the concrete contribution to the shear resistance caused by the compressive zone, aggregate interlock and dowel action. Furthermore, in case of correct detailing of reinforcement, the equilibrium calculation procedure will in all cases lead to a safe, lower limit of the shear resistance. It should be noted, that in the experiments in case of a limited amount of reinforcement the concrete contributes to the shear resistance significantly. It is of great importance that proper detailing of reinforcement is carried out to prevent sudden failure of dapped ends by shear. In case of improper detailing the failure mechanism assumed to be governing can mostly not develop. In accordance with the results described in the experiments, this will probably cause early failure. The finite element model (FEM) used is highly simplified. Only the prestressing cables and Dywidag bars are included in the model and loads are not distributed over multiple nodes. Overall it can be concluded that initiation as well as the direction of crack propagation are simulated quite well. However, it is not possible to make realistic statements about crack propagation, crack width and realistic crack strains at different load steps. More important, the calculated bearing reaction is a safe lower limit of the shear resistance. During the NLFEA it became clear that obtaining a realistic model of a prestressed dapped end beam is strongly depended on the input parameters used. It is expected that modelling of all reinforcement bars will result in a less conservative shear resistance. Further research is required to verify the statement above.Qshear capacity; half joints; dapped end beams; vertically prestressed; FEM; DIANA)uuid:8c564409ed5a4ca5b55fb85e16814076Dhttp://resolver.tudelft.nl/uuid:8c564409ed5a4ca5b55fb85e16814076YEnhancing iterative solution methods for general FEM computations using rigid body modes.Sangers, A.eVan Gijzen, M.B. (mentor); Vuik, C. (mentor); Schreppers, G.M.A. (mentor); Dubbeldam, J.L.A. (mentor)Rigid body modes; Approximate rigid body; Deflation; Coarse grid correction; FEM; Finite elements; Iterative solution method
20140627Numerical AnalysisApplied Mathematics52.009507, 4.360514)uuid:461ff59f1e5642cc9ffcc0c7e9edbbc9Dhttp://resolver.tudelft.nl/uuid:461ff59f1e5642cc9ffcc0c7e9edbbc9;High Strength Steel Structures FEM Validation ExperimentsChen, Y.\Kolstein, H. (mentor); Bijlaard, F. (mentor); Hoogenboom, P. (mentor); Dijkstra, O. (mentor)FFEM; Validation; Ansys workbench; High strength steel; Weld connection)uuid:a2b26a7f2f514176bc97550e30a6604aDhttp://resolver.tudelft.nl/uuid:a2b26a7f2f514176bc97550e30a6604aEStresses in asphaltic wearing courses on renovated steel bridge decks Jol, J.J.Molenaar, A.A.A. (mentor); Bijlaard, F.S.K. (mentor); Van Bochove, G.G. (mentor); Houben, L.J.M. (mentor); Kolstein, M.H. (mentor)Fatigue damage is a common problem in a lot of bridges with orthotropic steel decks. Frequent maintenance is required to prevent aggravation of the problems, which gives a lot of nuisance for the traffic using the bridge. This comes especially into play at large (river) crossings where not many alternatives are available. Therefore, methods are investigated for strengthening of those bridges in such a way that the magnitude and frequency of maintenance works can be reduced. In 2012, research work which focussed on the strengthening of bridges with movable steel decks (where usually a surface treatment is applied instead of an asphaltic surfacing) was finished, which showed very promising results. FEM modelling, labo< ratory tests and the application on a bridge deck in use all showed significant stress reductions. This thesis investigates the applicability of the above described renovation method for fixed bridges where an asphaltic wearing course should be taken into account. This does result in extra dead load on the renovated deck. Furthermore, the occurring stresses in the surfacing should now be taken into account. To investigate this structure, a characteristic part of the bridge deck (the deck plate between two stiffener webs) is simplified to a simply supported beam. The proposed renovation method is based on the addition of an extra steel plate with a polyurethane core between the original deck and this additional plate. A thicker core means more mass, but it also increases the bending stiffness of the whole structure. The extra mass from the reinforcement has to be compensated so that the dead load on the main girders and foundation is not increased. This demands special properties of the surface layer. For the wearing course, Brugflex is selected. This asphalt mix developed by Heijmans is stiff in vertical direction, but flexible in horizontal direction so that a good resistance against both rutting and fatigue cracking is obtained. For the membrane between the steel and asphalt, Parafor Ponts is selected. This bituminous membrane from the Icopal Group provides a good cohesion between the wearing course and the deck plate and has excellent waterproofing properties. It was chosen to use a finite element analysis approach to investigate the behaviour of the renovated structure, when subjected to a moving load. First, a lot of tests had to be executed to identify the membrane shear and tension properties at different temperatures and deformation rates. Finally those test results were combined to predict the properties for any arbitrary temperature and deformation rate. For the other materials, those characteristic properties were already defined. Finally, the renovated structure was modelled as a simple supported beam. Besides a reference model, similar to the surfacing on the Van Brienenoordbrug, five different geometries with varying asphalt thicknesses were constructed. It was tried to give all those renovated geometries a similar mass as the reference model, which was achieved by varying the core thickness between the two steel plates. The finite element analysis showed some promising results. With respect to the reference model, the bending stresses in the steel and asphalt were significantly reduced. Especially the decreased tension stress in the asphalt is important regarding fatigue cracks. Also the shear stresses in the membrane were considerably lower than in the reference model. Overall, the proposed renovation method showed encouraging results, which recommend further research. In the future, this renovation method might probably be a good option when an existing orthotropic bridge deck suffering fatigue has to be strengthened.0Asphalt; Steel; Bridge; Deck; Abaqus; FEM; PronyRoad and Railroad Engineering)uuid:374f9f8d5b1f438a8c09230e76a6de90Dhttp://resolver.tudelft.nl/uuid:374f9f8d5b1f438a8c09230e76a6de90NPunching shear behaviour of structural slabs on top of ribbed foundation piles
Schut, J.F.N.cHordijk, D.A. (mentor); Blom, C.B.M. (mentor); Hoogenboom, P.C.J. (mentor); Houben, L.J.M. (mentor)The excavated building pit is a frequently used building technique during the construction of structures below ground level. A temporary structure of sheet piles and underwater concrete is designed to retain soil and water. Ribbed tension piles are driven to compensate the hydrostatic pressure after dewatering of the construction pit. Generally, the top of the foundation piles are crushed before concreting the structural. The uncovered pile reinforcement is combined with the slab reinforcement which results in a monolithic floor with an optimal connection between slab and pile. During some construction projects it is desirable to avoid pile head crushing for economic reasons or to prevent the stray current phenomena. The que< stion that arises is to what extend does the partly penetrated ribbed foundation pile influence the punching shear behaviour of the structural slab when the pile is loaded in compression during the exploitation phase. At the heart of this debate lies the problem of the effectiveness of the present ribs and the associated punching cone perimeter. In order to investigate the punching shear behaviour, simulations by nonlinear finite element analyses have been performed using the software ATENA developed by Cervenka Consulting. Initially, conducted experiments were simulated in order to validate the modelling technique. The contact area is modelled with interface material, based on the MohrCoulomb failure criterion for shear planes. The FEM analyses showed good agreement with the conducted experiments regarding to crack propagation which induces punching shear. The case study is made up of a number of subsequent modelling steps to investigate each influence separately. The case study starts with a parameter study to investigate the influence of the shear transfer capacity from slab to pile on the punching behaviour. The maximum allowable shear stress depends of a cohesion parameter and a coefficient of friction parameter. Various combinations of both parameters are investigated with respect to the punching shear behaviour. A clear distinction in failure behaviour is observed between a friction coefficient of 1.0 and 1.4. Up to a friction coefficient of 1.0, the critical shear crack propagates from pile head towards the slab surface which indicates that only the top part of the slab is responsible for punching shear resistance. From a friction coefficient of 1.4 the critical shear crack propagates from slab bottom towards slab surface, which indicates that the full slab height is active in punching resistance. This change in punching cone size results in a failure load which is more than twice as high. No significant increase of failure load is observed during analyses with different cohesion values. The second step consists of adding reinforcement to the initial model. The influence of bending reinforcement was neglectable due to the limited slab deflections. However, the influence of shear reinforcement was significant. For friction coefficients from 0.0 to 1.0, the failure load increased with a magnitude of roughly four compared to the failure load without shear reinforcement. An increase of roughly two is observed for friction coefficients of 1.4 or greater. Also a change in failure behaviour is observed. For friction coefficients of 1.0 or greater, the brittle punching behaviour changes into ductile flexural behaviour. This is highly desirable because large structural deflections insinuates an upcoming failure. Although full scale laboratory tests are needed to verify the numerical results, the recommendation for practical use is that for structural slabs provided with shear reinforcement and a foundation pile with at least two ribbed sides, a fully punching cone develops.1Punching Shear; FEM; ATENA Concrete; Ribbed piles)uuid:b6d766d5903040be8cfded75b23833dfDhttp://resolver.tudelft.nl/uuid:b6d766d5903040be8cfded75b23833dfuNumerical modeling of damreservoir interaction seismic response using the Hybrid Frequency Time Domain (HFTD) methodSirumbal Zapata, L.F.cMetrikine, A.V. (mentor); Hendriks, M.A.N. (mentor); Kikstra, W.P. (mentor); Lourens, E.M. (mentor)The research work studies the fundamentals of the Hybrid FrequencyTime Domain (HFTD) method for dynamic analysis of structures, applied to the seismic analysis of damreservoir interaction systems. The theoretical consistency and accuracy of the HFTD method, based on the frequency domain Fourier analysis, is demonstrated through all the parts of the thesis, but particularly in Chapter 5 for linear and highly nonlinear single degree of freedom (SDOF) models subject to several types of loading, and in Chapter 7 for a 2D damreservoir interaction finite element model subject to an earthquake ground acceleration loading. On the other hand, a Finite Element Method (FEM) fo< rmulation of damreservoir interaction problems is presented, being demonstrated the frequencydependence nature of this type of systems. The fluid compressibility and boundary conditions of the reservoir are analytically identified as the frequency dependent properties of the system. In this context, the HFTD method is proposed as an ideal method for the dynamic analysis of frequency dependent systems with nonlinear behavior, being the damreservoir interaction problem taken as a case study to prove this hypothesis.HFTD; damreservoir interaction; frequency domain analysis; fourier analysis; FEA; DIANA; FEM; seismic analysis; earthquake engineering; ground acceleration loadingStructural Mechanics)uuid:6dd0caf03128420093a5104ebbbc135fDhttp://resolver.tudelft.nl/uuid:6dd0caf03128420093a5104ebbbc135fYFeasibility study on fiber reinforced polymer cylindrical truss bridges for heavy trafficChlosta, M.cBijlaard, F.S.K. (mentor); Kolstein, M.H. (mentor); De Boer, A. (mentor); Hendriks, M.A.N. (mentor)Considering the recent increase in the use of fiber reinforced polymers in the civil engineering industry in general and in the bridge engineering industry in particular, as well as the recently more and more applied cylindrical truss bridge type, this research focuses on the question whether it is possible to combine fiber reinforced polymers as standalone structural material and this bridge type to construct a bridge suitable for heavy traffic as well as bicycle and pedestrian traffic. This research combines an extensive literature study on the use of fiber reinforced polymers for bridge engineering with a theoretical feasibility and designstudy on fiber reinforced polymer cylindrical truss bridges for heavy traffic. During the design study the spatial needs of all bridge users were defined to obtain an initial shape of the bridge. This shape was then optimized in several steps using finiteelementmodeling and analysis, yielding a final shape of the bridge. The behavior of this structure under design loads was then extensively investigated, again using finite element analysis, showing that the bridge could very well meet the selfderived deflection limit for fiber reinforced polymers at relatively low stress levels. Since fiber reinforced materials are a very diverse field of material, with hundreds of different compositions being available, the first result of this study was the choice of a suitable composite for further analysis. For this bridge design very high fiber content (>60%) carbon/epoxy composite was used. The main reason for this choice was the high modulus and strength of the carbon fibers and the high durability and strength of the epoxy resin. A major reason of the slow implementation of fiber reinforced polymers in the bridge engineering industry are the worries concerning the lack of fire safety of the material. The literature study of this research showed however that it is possible to construct a heavy traffic fullFRP truss bridge, while complying with the known fire safety standards. The virgin FRP material can be adapted by several fireprotection measures; it turned out that a combination of intumescent gelcoating and low volume phosphorous filler systems works best in increasing the fire resistance and thereby providing a fire resistance class of R30 for hydrocarbon fire curve loading. The initial shape of the bridge was optimized in three stages: first several different truss topologies, which were derived with a parametric geometric model, were analyzed and compared using finite element analysis software, yielding the square truss with one diagonal as most efficient topology. In the next steps several grid sizes of this truss as well as several cross section dimensions were compared, again using finite element analysis software. An optimum was found between minimum material usage and minimum deflection, which reduced the material usage of the main load bearing elliptical truss by about 40% compared to the initial variant. The optimized structure was then fitted with the inner bridge deck suppor< ting trusses as well as the cantilever trusses. The elliptical truss bridge performed very well considering the maximum deflections and stresses under Eurocode design loads and load combinations that were derived in finite element modeling software. When comparing the fullFRP bridge design with similar, existing steel structures, the maximum deformations and stresses were considerably lower for the fullFRP bridge while only weighing about 60% of the steel structure. This research showed that the new cylindrical truss bridge type is not only an aesthetically appealing structure but also performs structurally very well when combined with fiber reinforced polymer as structural material. It turned out that fiber reinforced polymers can be used as standalone structural material for medium span heavy traffic bridges. Next to that, this research clarified that there is no legitimate structural reason for the fact that fiber reinforced polymers are used relatively scarcely in the civil engineering and bridge engineering industry compared to traditional building materials such as steel and concrete. Since this research is one of the first researches of its kind, using FRP as standalone structural material for a relatively new and complex bridge type, more research is needed in the field of high order connections for fiber reinforced polymer circular hollow sections. Next to that the possibility of the use of differently sized and shaped cross sections for the truss members should be investigated.fiber reinforced polymers; plastics; FRP; civil engineering; bridge engineering; structural engineering; structural design; bridge design; stiffness driven design; cylindrical truss; elliptical truss; tubular truss; spatial truss; truss topology optimization; grid size optimization; space efficiency; heavy traffic road bridge; truss topology; mechanical properties of FRP materials; fire safety; fire resistance; steel viaduct comparison; FEA; FEM; finite element modeling; finite element analysis; CFRP; carbon; epoxy
20120724)uuid:2b519b8aaaa546499d63b951c8237489Dhttp://resolver.tudelft.nl/uuid:2b519b8aaaa546499d63b951c8237489zThreedimensional numerical analysis of tunnelling induced damage: The influence of masonry building geometry and locationKappen, J.M.J.^Rots, J.G. (mentor); Hendriks, M.A.N. (mentor); Giardina, G. (mentor); Pasterkamp, S. (mentor)HRecent tunnelling projects have received a great amount of media attention due to settlement induced damage. Due to the simplified approach of existing risk assessment methods, a new assessment system is in development, which can account for threedimensional structural aspects of buildings. The aim of this study is to investigate the influence of the position and geometry of masonry buildings on the development of damage, while undergoing tunnelling induced settlements. In line with previous research, threedimensional finite element analyses are used as a tool to perform a parametric study. A parametric study consists of an evaluation of the parameters position, aspectratio, grouping and orientation. The position parameter is divided into three characteristics: the sagging zone, a combined settlement profile and the hogging zone. The aspectratio parameter is also divided into three characteristics: shallow buildings, square buildings and deep buildings. The grouping effect parameter also distinguishes three characteristics: small and large isolated buildings and grouped buildings. The orientation parameter includes seven different increasing angles of the building main axis with respect to the tunnelling axis. The maximum measured crack width in the buildings gives input for a classification of damage, according the system of Burland et al. (1977). An average trend in the damage classification indicates the sensitivity to tunnelling induced settlements of the parameters. Both during and after tunnelling, a position of the building in the combined settlement profile appears to be the most sensitive to differential settlements. Buildings far away from the tunnelling axis generall< y obtain no more than slight damage. Structures with a low aspectratio seem on average to obtain equal amounts of damage as buildings with an aspectratio of 1. Structures with a higher aspectratio are less affected, both during and after tunnelling. Grouping of the buildings seems to be an influential parameter. Small isolated buildings obtain far less damage than large or grouped buildings. In relation to the numerical analyses, the empirical Limiting Tensile Strain Method (LTSM) seems to overestimate the damage for an isolated small building, but underestimate the damage in large or grouped buildings. For buildings in the sagging zone, a building with a low orientation angle is the least sensitive to differential settlement, while the maximum measured crack width increases by increasing the angle. The difference in maximum crack width can grow to a factor 3. A building in the combined settlement profile or in the hogging zone displays opposite behaviour. Cases with low orientation angles are the most susceptible to damage, while increasing the angle to 90 degrees lowers the maximum measured crack width. The difference in results can grow up to a factor 2.wtunnelling; settlement damage; LTSM; FEM; damage assessment; masonry; FEA; 3D finite element analysis; tunnel alignment)uuid:c25459fa60c94cb3acd0ad6035ce6b0fDhttp://resolver.tudelft.nl/uuid:c25459fa60c94cb3acd0ad6035ce6b0f0Modelling and simulation of bone implant healingThe, M.T.A.Vermolen, F. (mentor)gIn this report a model for the ingrowth of a prosthesis in a bone will be formulated and simulated. First an overview is given of all the biological processes that are part of this healing process and what external factors can influence this process. Then a first mathematical model is presented in which the mechanical stimuli (one of the external factors that can influence the healing process) are neglected. The model is solved by numerical means with both the finite volume method as the finite element method. For the finite element method a short introduction is first given to get familiar with this technique. Results for this model will be presented, followed by a short discussion about the results and a conclusion. Subsequently the previous model is extended to incorporate mechanical stimuli, this is done by combining it with an elasticity equation. A short introduction will also be given to the theory of linear elasticity. The model is then solved using finite element analysis and finally also the results for this extended model will be presented, together with once again a short discussion and conclusion.Fimplant; bone healing; simulation; modelling; FEM; biology; prosthesisbachelor thesis
20100901)uuid:c72e6c92f1dc43a097ae1fdbcb41e496Dhttp://resolver.tudelft.nl/uuid:c72e6c92f1dc43a097ae1fdbcb41e496hLocal Buckling Behaviour of a Corrosion Resistant Alloy Liner in Tight Fit Pipe due to Axial Compression Fathi, N.YCurrie, P.K. (mentor); Meek, J. (mentor); Zitha, P.L.J. (mentor); Gresnigt, A.M. (mentor)A promising possibility to reduce corrosion resistant pipeline costs is the concept of Tight Fit Pipe, which is a double wall pipe where a Corrosion Resistant Alloy liner is mechanically fitted inside a carbon steel outer pipe. The mechanical bonding of the Tight Fit Pipe is made through a thermohydraulic manufacturing process. Problem definition Buckling of cylinders subjected to flexural loads (applied to Tight Fit Pipe during cost effective reeling) correlates in a number of respects to buckling of axially compressed cylinders: in both cases the critical stresses (or strains) are of the same order of magnitude and the failure modes have the same characteristics. Results from the axial compression tests provided better understanding of the buckling behaviour of Tight Fit Pipe during bending and results from this thesis study have been used as input for a bending rig construction. Research The main objective of this thesis is to investigate, theoretically and experimentally, the local buckling behaviour due to axial compression of the Corrosion Resist<Sant Alloy liner, whilst fitted in the outer pipe of the Tight Fit Pipe configuration. The liner of the Tight Fit Pipe as tested is first analysed when not fitted in the outer pipe. Secondly the liner is analysed when fitted in the outer pipe of the Tight Fit Pipe. The liner has a higher capacity in stress and strain when the liner is placed in the outer pipe, i.e. mechanically fitted, compared with the liner alone. Results, Conclusions and Recommendations [a.] Buckling of the liners (of Tight Fit pipes (TFP) used in the experiments), without the outer pipe, occurred outward in a single axi symmetrical wrinkle. [b.] The liners in the tight fit pipes, confined in an outer 12 inch pipes used in the experiments, buckle inward in a nonsymmetrical wrinkle. [c.] Wrinkles (of liners confined in an outer 12 inch pipe) do not exceed 90 of the circumference. The wrinkles have an axis which is circumferential. Wrinkles do not tend to connect with each other if more than one is present at about the same height. [d.] The maximum force in the load  strain diagram was considered to be the point at which wrinkling occurred. There was a good agreement between the Finite Element (FEM) results and test results for the maximum force. The FEM results for the strain at the maximum force were much higher than in the tests. [e.] Buckling of a liner in a 12 inch pipe has a larger critical buckling force than a liner which is not confined in an outer pipe. This is due to the resistance to outward buckling. Bigger wrinkles must fit in a smaller radius which costs more energy than free outward buckling. This could also be the reason why the wrinkles do not tend to form as one big wrinkle in a 360 degrees radius. Outward buckling tend to occur in one axi symmetrical wrinkle. [f.] The buckling behaviour of the liner in the TFP is believed to be influenced by three different TFP properties: [f1.] Low or high fit (residual hoop stress), [f2.] Type of CRA (Material strength) and [f3.] Type of outer pipe used, seamless or UOEpipe (Liner to outer pipe contact irregularities ) [f1] has been proven in the test results; [f2] and [f3] are still to be proven in future work.Tight fit Pipe; Liner; TFP; Reeling; Finite Element; FEM; Axial Compression; CRA; Buckling; Oil Pipeline; Gas Pipeline; Corrosion; wrinkling; Buckle
Geotechnology
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