Dissertations / Theses on the topic 'Interaction avalanche and structure'
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Allen, Simon Keith. "Meteorology and snowpack structure associated with avalanche hazard, Porter Heights, Canterbury." Thesis, University of Canterbury. Department of Geography, 2004. http://hdl.handle.net/10092/2778.
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With an increase in use of New Zealand's alpine terrain, there is a growing need to understand processes and phenomena associated with snow avalanche hazard. This research investigates snowpack structure and meteorological influences associated with avalanching at Porter Heights Ski Area and overviews the management practices employed in response to this hazard. Data sources are derived from meteorological and snowpack observations dating back to 1977, coupled with comprehensive field studies in 2003. Weak faceted and mixed crystal forms were found to comprise on average over 40 % of the early season snowpack on sunny and shaded slope aspects, although they could persist on shaded slopes throughout the season, contributing to spring avalanche events. The growth of both lower pack depth hoar, and near-surface facets were strongly influenced by synoptic airflows. Forty-eight hours after the onset of a cool southeast airflow, the temperature gradients in a shallow snowpack ranged from -0.36 °C cm-1 near the surface, to -0.17 °C cm-1 deeper in the pack. A warmer northwest flow induced surface melting, and dramatically altered the thermal regime of the snowpack. Thick layers of rounded grains indicated the importance of equilibrium growth and wind redistribution of snow. Wind loading is most extensive on slopes leeward to the prevalent, strong, west to northwest winds, and slab formation in this terrain is regularly controlled using hand placed explosives and ski cutting techniques. Density measurements centred on a median value of 185 kg/nr' suggested the significance of decomposing new snow in forming surface slabs, with the largest snowfalls at Porter Heights occurring during east to southeast storm events. While this study has cemented a comprehensive understanding of meteorology and snowpack structure at Porter Heights, backcountry avalanche forecasting in the neighbouring terrain will further benefit from larger scale, collaborative future research initiatives.
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Zäll, Emma. "Footbridge Dynamics : Human-Structure Interaction." Licentiate thesis, KTH, Bro- och stålbyggnad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-224527.
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For aesthetic reasons and due to an increased demand for cost-effective and environmentally friendly civil engineering structures, there is a trend in designing light and slender structures. Consequently, many modern footbridges are susceptible to excessive vibrations caused by human-induced loads. To counteract this, today's design guidelines for footbridges generally require verification of the comfort criteria for footbridges with natural frequencies in the range of pedestrian step frequencies. To ensure that a certain acceleration limit is not exceeded, the guidelines provide simplified methodologies for vibration serviceability assessment. However, shortcomings of these methodologies have been identified. First, for certain footbridges, human-structure interaction (HSI) effects might have a significant impact on the dynamic response. One such effect is that the modal properties of the bridge change in the presence of a crowd; most importantly, the damping of the bridge is increased. If this effect is neglected, predicted acceleration levels might be overestimated. Second, as a running person induces a force of greater amplitude than a walking person, a single runner might cause a footbridge to vibrate excessively. Hence, the running load case is highly relevant. These two aspects have in common that they are disregarded in existing design guidelines. For the stated reasons, the demand for improvements of the guidelines is currently high and, prospectively, it might be necessary to require the consideration of both the HSI effect and running loads. Therefore, this licentiate thesis aims at deepening the understanding of these subjects, with the main focus being placed on the HSI effect and, more precisely, on how it can be accounted for in an efficient way. A numerical investigation of the HSI effect and its impact on the vertical acceleration response of a footbridge was performed. The results show that the HSI effect reduces the peak acceleration and that the greatest reduction is obtained for a crowd to bridge frequency ratio close to unity and a high crowd to bridge mass ratio. Furthermore, the performance of two simplified modelling approaches for consideration of the HSI effect was evaluated. Both simplified models can be easily implemented and proved the ability to predict the change in modal properties as well as the structural response of the bridge. Besides that, the computational cost was reduced, compared to more advanced models. Moreover, a case study comprising field tests and simulations was performed to investigate the effect of runners on footbridges. The acceleration limit given in the design guideline was exceeded for one single person running across the bridge while a group of seven people walking across the bridge did not cause exceedance of the limit. Hence, it was concluded that running loads require consideration in the design of a footbridge.På grund av estetiska skäl och en ökad efterfrågan på kostnadseffektiva och miljövänliga konstruktioner är merparten av de gångbroar som konstrueras idag förhållandevis lätta och slanka. Med anledning av detta ökar risken för att stora svängningar uppstår på grund av dynamisk belastning från människor på bron. För att motverka att detta inträffar kräver dagens normer att komforten verifieras för gångbroar med egenfrekvenser inom området för människans stegfrekvens. Komforten verifieras genom att säkerställa att ett visst accelerationskriterium inte överskrids. För detta ändamål finns handböcker som tillhandahåller förenklade beräkningsmetoder för uppskattning av accelerationsnivåer. Brister i dessa beräkningsmetoder har emellertid identifierats. För det första kan olika typer av människa-bro-interaktion (HSI) ha en betydande inverkan på responsen hos vissa broar. Exempel på en HSI-effekt är att brons modala egenskaper förändras när människor befinner sig på bron; i huvudsak sker en ökning av brons dämpning. Om denna effekt inte tas i beaktande föreligger stor risk att överskatta förväntade accelerationsnivåer. För det andra är kraften från en löpare större än kraften från en gående person vilket gör att en ensam löpare på en gångbro kan ge upphov till accelerationsnivåer som överskrider gränsvärdena för komfort. Löpande personer är därför ett mycket relevant lastfall. Befintliga normer uttrycker inte explicit att någon av dessa aspekter bör tas i beaktande. Behovet av förbättrade riktlinjer för hur normerna bör tillämpas är därför mycket stort och i framtiden kan det bli nödvändigt att kräva att både HSI-effekter och löparlaster tas i beaktande. Därför syftar denna licentiatavhandling till att bidra till en fördjupad förståelse inom dessa två ämnen, med huvudfokus på ovan nämnda HSI-effekt i allmänhet och hur den kan beaktas på ett enkelt, noggrant och tidseffektivt sätt i synnerhet. En numerisk undersökning av HSI-effekten och dess inverkan på den vertikala responsen hos en gångbro genomfördes. Resultaten visar att HSI-effekten reducerar den maximala accelerationen och att störst reduktion erhålls då folksamlingen och bron har ungefär samma egenfrekvens och då folksamlingens massa är stor i förhållande till brons massa. Vidare utvärderades två förenklade metoder för beaktande av HSI-effekten vilka kan implementeras av konstruktörer med grundläggande kunskaper inom strukturdynamik. Det konstaterades att båda metoderna uppskattar HSI-effekten såväl som brons respons förhållandevis väl samtidigt som de reducerar beräkningstiden något jämfört med mer avancerade metoder. Effekten av löpare på gångbroar studerades genom en fallstudie med fältmätningar. Utifrån resultaten från dessa fältmätningar kunde det konstateras att accelerationsgränsen som anges i normerna överskreds när en ensam löpare sprang över bron men inte när en grupp på sju personer gick i takt över samma bro. Därför drogs slutsatsen att löparlaster bör tas i beaktande vid dimensionering av en gångbro.
QC 20180320
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Fernandez, Carlos Javier. "Pile-structure interaction in GTSTRUDL." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/21418.
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Howell, Richard Martyn. "Snoring : a flow-structure interaction." Thesis, University of Warwick, 2006. http://wrap.warwick.ac.uk/101139/.
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A novel method for calculating the linear fluid-structure interaction of a cantilevered flexible surface centrally positioned in an ideal channel flow, incorporating the effects of vorticity shed downstream, is described. The perturbation pressure is modelled using a linearised boundary-element method. The flexible surface deflection is modelled using linearised one-dimensional beam theory. The shed vorticity is modelled using a linearised discrete vortex method. The computational model can therefore be used to conduct numerical experiments where no presupposition of the flexible surface deflection is made. This linear model can accurately capture the onset of instability in this fluid-structure system. The flexible surface is infinitely thin; the upper and lower sides of the surface can therefore be considered stream lines of the flow, with a step jump in pressure between them across the surface. The discontinuity of tangential velocity across the flexible surface generates lift. The flexible surface is therefore modelled by a distribution of vortex singularities with a Kutta condition applied at the surface’s trailing edge. The individual models of the flexible surface and the fluid velocity and vorticity, together with the action of the individual hydrodynamic pressure components created when the models are combined to form a single unsteady model, are validated via a series of numerical experiments and by quantitative comparison with an appropriate, previously developed computational model. Unique, highly detailed investigations into the ideal fluid-structure phenomena observed in numerical experiments conducted over a wide range of mass ratio and inlet velocity are documented. For the first time, detailed numerical investigation of the effect on this fluid-structure interaction of channel walls, a rigid central surface (upstream and adjacent to the flexible surface), unsteady mean flow, the variation of stiffness and damping properties along the flexible surface and the vorticity shed at the trailing edge of the flexible surface have been quantified. Calculations of the critical velocity show good correlation with other published work and examples of the possible application of the unsteady model to different physical fluid-structure phenomena are outlined. Of central importance is the application of the unsteady model to the investigation of the human snoring phenomenon. Further insight into the operation of two types of snore is made and a new type of snore is discovered, incorporating the effects of inhalation. The numerical experiments demonstrate that the location (on the flexible surface) of the destabilising phase shift between the flexible surface velocity and fluid pressure leading to instability change drastically for a small shift in mass ratio. Coupled with knowledge of further snore mechanisms from other published work, these results show the uniqueness of treatment required to provide effective surgical treatment to individual patients suffering from snoring; furthermore, this highlights the need for more realistic fluid-structure models to be created.
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El, Baroudi Adil. "Modélisation en interaction fluide-structure." Rennes 1, 2010. http://www.theses.fr/2010REN1S140.
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Ce travail de thèse est essentiellement constitué de deux parties. La première partie s’intéresse à la modélisation du système crâne-cerveau lors d’un choc. Dans ce système, le fluide joue un rôle tampon entre les deux solides qui ont des propriétés matérielles complètement différentes. Lors d’un choc, on n’arrive pas jusqu’à présent à comprendre les phénomènes d’apparition de lésions cérébrales, qui constituent un enjeu majeur en accidentologie. L’étude s’appuie sur un dispositif expérimental existant, à partir duquel des modèles ont été élaborés. Deux modèles ont été proposés : couplage inertiel et couplage visqueux. Ceux-ci ont été résolus analytiquement et numériquement. La seconde partie aborde la dynamique du système aortique pendant un choc. Dans un premier temps, on s’intéresse à la réponse dynamique de la branche ascendante de l’aorte où une solution analytique du problème modal associé est proposée, afin de pouvoir utiliser par la suite une technique de projection modale. Ensuite, le système entier est soumis à un choc. En effet, en accidentologie, on observe dans certaines situations, une rupture au niveau de la partie terminale de branche ascendante de l’aorte : c’est la rupture isthmique. Dans toute l’étude, le caractère hétérogène de la paroi aortique est pris en compte. Diverses études à caractère paramétrique ont été menéesThis thesis is essentially constituted of two parts. The first part focuses on modeling the skull-brain system during an impact. In this system, the fluid acts as a buffer between the two elastic solids with completely different material properties. During an impact, we are not able to understand untill now some phenomena of brain injury, which is a major challenge in traffic accident. The study used on an existing experimental device from which models were developed. Two models were proposed : inertial coupling and viscous coupling. These have been solved analytically and numerically. The second part deals with the dynamics of the aortic system during a shock. Initially, we study the dynamic response of the ascending branch of the aorta where an analytical solution of the modal problem associated is proposed in order to subsequently use a modal projection technique. Then, the whole system is subjected to a shock. Indeed, in accident research, we observe in some cases, a break at the end portion of descending branch of the aorta : the isthmic rupture phenomenon. In all the study, the heterogeneous character of the aortic wall is taken into account. Various parametric studies have been conducted
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Saez, Robert Esteban. "Interaction dynamique non-linéaire sol-structure." Phd thesis, Ecole Centrale Paris, 2009. http://tel.archives-ouvertes.fr/tel-00453297.
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L'interaction dynamique entre le sol et les structures (IDSS) a fait l'objet de nombreuses études sous l'hypothèse de l'élasticité linéaire, bien que les effets de l'IDSS puissent être différents entre un système élastique et un système inélastique. De fait, les méthodologies usuelles développées à partir des études élastiques peuvent ne pas être adaptées aux bâtiments conçus pour dissiper de l'énergie par de l'endommagement lors de séismes sévères. De plus, il est bien connu que la limite d'élasticité du sol est normalement atteinte même pour de séismes relativement faibles. En conséquence, si les effets inélastiques de l'IDSS sont négligés, les études d'endommagement sismique des bâtiments peuvent être très inexactes. L'objectif de ce travail est de développer une stratégie générale pour l'étude du problème de l'IDSS non-linéaire dans le contexte de l'analyse de la vulnérabilité sismique des bâtiments. Ainsi, des modèles d'éléments finis réalistes sont développées et appliquées à des problèmes d'IDSS non-linéaires. Les modèles couvrent une large gamme des conditions pour le sol et des typologies de bâtiments soumis à plusieurs bases de données sismiques. Une stratégie de modélisation a été développée et validée afin de réduire significativement le coût numérique. Pour cela, un modèle 2D équivalent a été développé, implanté dans GEFDyn et utilisé pour effectuer une importante étude paramétrique. De nombreux indicateurs de comportement non-linéaire de la structure et du sol ont été proposés pour synthétiser leur fonctionnement lors du chargement sismique. De surcroît, une stratégie d'évaluation de la vulnérabilité sismique basée sur l'information apportée par une base des données sismiques a été développée. De façon, générale, les résultats ont mis en évidence une réduction de la demande sismique lorsque les effets inélastiques de l'IDSS sont pris en compte. Cette réduction est liée fondamentalement à deux phénomènes : l'amortissement par radiation et l'amortissement hystérétique du sol. Ces deux effets ont lieu simultanément pendant le mouvement sismique. Il est alors très difficile d'isoler l'influence de ces deux phénomènes. En effet, le mouvement effectif transmis à la structure n'est pas le même que celui en champs libre du aux effets d'interaction, ainsi qu'à la modification locale du comportement du sol fortement lié aux poids du bâtiment. Une série de mesures de sévérité sismique et des mécanismes de dissipation d'énergie au niveau du sol et du bâtiment a été introduite dans le but d'analyser ces effets. Cependant, ces résultats sont en général très irréguliers et leur généralisation a été très difficile. Néanmoins, ces résultats mettent en évidence l'importance de la prise en compte des effets du comportement inélastique du sol. La plupart des cas étudiés ont montré un effet favorable de l'IDSS non-linéaire. Mais, en général, l'IDSS peut augmenter ou diminuer la demande sismique en fonction de la typologie de la structure, des caractéristiques du mouvement sismique et des propriétés du sol. Tout de même, il y a une justification économique pour étudier les effets du comportement non-linéaire du sol sur la réponse sismique.
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Altstadt, Eberhard, Helmar Carl, and Rainer Weiß. "Fluid-Structure Interaction Investigations for Pipelines." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28993.
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The influence of the fluid-structure interaction on the magnitude fo the loads on pipe walls and support structures is not yet completely understood. In case of a dynamic load caused by a pressure wave, the stresses in pipe walls, especially in bends, are different from the static case.
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Jones, Christopher Andrew. "Crowd-structure dynamic interaction in stadia." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543299.
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Plessas, Spyridon D. "Fluid-structure interaction in composite structures." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/41432.
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Approved for public release; distribution is unlimited.In this research, dynamic characteristics of polymer composite beam and plate structures were studied when the structures were in contact with water. The effect of fluid-structure interaction (FSI) on natural frequencies, mode shapes, and dynamic responses was examined for polymer composite structures using multiphysics-based computational techniques. Composite structures were modeled using the finite element method. The fluid was modeled as an acoustic medium using the cellular automata technique. Both techniques were coupled so that both fluid and structure could interact bi-directionally. In order to make the coupling easier, the beam and plate finite elements have only displacement degrees of freedom but no rotational degrees of freedom. The fast Fourier transform (FFT) technique was applied to the transient responses of the composite structures with and without FSI, respectively, so that the effect of FSI can be examined by comparing the two results. The study showed that the effect of FSI is significant on dynamic properties of polymer composite structures. Some previous experimental observations were confirmed using the results from the computer simulations, which also enhanced understanding the effect of FSI on dynamic responses of composite structures.
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Randall, Richard John. "Fluid-structure interaction of submerged shells." Thesis, Brunel University, 1990. http://bura.brunel.ac.uk/handle/2438/5446.
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A general three-dimensional hydroelasticity theory for the evaluation of responses has been adapted to formulate hydrodynamic coefficients for submerged shell-type structures. The derivation of the theory has been presented and is placed in context with other methods of analysis. The ability of this form of analysis to offer an insight into the physical behaviour of practical systems is demonstrated. The influence of external boundaries and fluid viscosity was considered separately using a flexible cylinder as the model. When the surrounding fluid is water, viscosity was assessed to be significant for slender structural members and flexible pipes and in situations where the clearance to an outer casing was slight. To validate the three-dimensional hydroelasticity theory, predictions of resonance frequencies and mode shapes were compared, with measured data from trials undertaken in enclosed tanks. These data exhibited differences due to the position of the test structures in relation to free and fixed boundaries. The rationale of the testing programme and practical considerations of instrumentation, capture and storage of data are described in detail. At first sight a relatively unsophisticated analytical method appeared to offer better correlation with the measured data than the hydroelastic solution. This impression was mistaken, the agreement was merely fortuitous as only the hydroelastic approach is capable of reproducing-the trends recorded in the experiments. The significance of an accurate dynamic analysis using finite elements and the influence of physical factors such as buoyancy on the predicted results are also examined.
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Warnakulasuriya, Hapuhennedige Surangith. "Soil structure interaction of buried pipes." Thesis, University of East London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286607.
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Lees, Andrew Steven. "Soil/structure interaction of temporary roadways." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324808.
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Giannopapa, Christina-Grigoria. "Fluid structure interaction in flexible vessels." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413425.
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Wright, Stewart Andrew. "Aspects of unsteady fluid-structure interaction." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621939.
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Jones, Piet. "Structure learning of gene interaction networks." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86650.
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Thesis (MSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: There is an ever increasing wealth of information that is being generated regarding biological systems, in particular information on the interactions and dependencies of genes and their regulatory process. It is thus important to be able to attach functional understanding to this wealth of information. Mathematics can potentially provide the tools needed to generate the necessary abstractions to model the complex system of gene interaction. Here the problem of uncovering gene interactions is cast in several contexts, namely uncovering gene interaction patterns using statistical dependence, cooccurrence as well as feature enrichment. Several techniques have been proposed in the past to solve these, with various levels of success. Techniques have ranged from supervised learning, clustering analysis, boolean networks to dynamical Bayesian models and complex system of di erential equations. These models attempt to navigate a high dimensional space with challenging degrees of freedom. In this work a number of approaches are applied to hypothesize a gene interaction network structure. Three di erent models are applied to real biological data to generate hypotheses on putative biological interactions. A cluster-based analysis combined with a feature enrichment detection is initially applied to a Vitis vinifera dataset, in a targetted analysis. This model bridges a disjointed set of putatively co-expressed genes based on signi cantly associated features, or experimental conditions. We then apply a cross-cluster Markov Blanket based model, on a Saccharomyces cerevisiae dataset. Here the disjointed clusters are bridged by estimating statistical dependence relationship across clusters, in an un-targetted approach. The nal model applied to the same Saccharomyces cerevisiae dataset is a non-parametric Bayesian method that detects probeset co-occurrence given a local background and inferring gene interaction based on the topological network structure resulting from gene co-occurance. In each case we gather evidence to support the biological relevance of these hypothesized interactions by investigating their relation to currently established biological knowledge. The various methods applied here appear to capture di erent aspects of gene interaction, in the datasets we applied them to. The targetted approach appears to putatively infer gene interactions based on functional similarities. The cross-cluster-analysis-based methods, appear to capture interactions within pathways. The probabilistic-co-occurrence-based method appears to generate modules of functionally related genes that are connected to potentially explain the underlying experimental dynamics.
AFRIKAANSE OPSOMMING: Daar is 'n toenemende rykdom van inligting wat gegenereer word met betrekking tot biologiese stelsels, veral inligting oor die interaksies en afhanklikheidsverhoudinge van gene asook hul regulatoriese prosesse. Dit is dus belangrik om in staat te wees om funksionele begrip te kan heg aan hierdie rykdom van inligting. Wiskunde kan moontlik die gereedskap verskaf en die nodige abstraksies bied om die komplekse sisteem van gene interaksies te modelleer. Hier is die probleem met die beraming van die interaksies tussen gene benader uit verskeie kontekste uit, soos die ontdekking van patrone in gene interaksie met behulp van statistiese afhanklikheid , mede-voorkoms asook funksie verryking. Verskeie tegnieke is in die verlede voorgestel om hierdie probleem te benader, met verskillende vlakke van sukses. Tegnieke het gewissel van toesig leer , die groepering analise, boolean netwerke, dinamiese Bayesian modelle en 'n komplekse stelsel van di erensiaalvergelykings. Hierdie modelle poog om 'n hoë dimensionele ruimte te navigeer met uitdagende grade van vryheid. In hierdie werk word 'n aantal benaderings toegepas om 'n genetiese interaksie netwerk struktuur voor te stel. Drie verskillende modelle word toegepas op werklike biologiese data met die doel om hipoteses oor vermeende biologiese interaksies te genereer. 'n Geteikende groeperings gebaseerde analise gekombineer met die opsporing van verrykte kenmerke is aanvanklik toegepas op 'n Vitis vinifera datastel. Hierdie model verbind disjunkte groepe van vermeende mede-uitgedrukte gene wat gebaseer is op beduidende verrykte kenmerke, hier eksperimentele toestande . Ons pas dan 'n tussen groepering Markov Kombers model toe, op 'n Saccharomyces cerevisiae datastel. Hier is die disjunkte groeperings ge-oorbrug deur die beraming van statistiese afhanklikheid verhoudings tussen die elemente in die afsondelike groeperings. Die nale model was ons toepas op dieselfde Saccharomyces cerevisiae datastel is 'n nie- parametriese Bayes metode wat probe stelle van mede-voorkommende gene ontdek, gegee 'n plaaslike agtergrond. Die gene interaksie is beraam op grond van die topologie van die netwerk struktuur veroorsaak deur die gesamentlike voorkoms gene. In elk van die voorgenome gevalle word ons hipotese vermoedelik ondersteun deur die beraamde gene interaksies in terme van huidige biologiese kennis na te vors. Die verskillende metodes wat hier toegepas is, modelleer verskillende aspekte van die interaksies tussen gene met betrekking tot die datastelle wat ons ondersoek het. In die geteikende benadering blyk dit asof ons vermeemde interaksies beraam gebaseer op die ooreenkoms van biologiese funksies. Waar die a eide gene interaksies moontlik gebaseer kan wees op funksionele ooreenkomste tussen die verskeie gene. In die analise gebaseer op die tussen modelering van gene groepe, blyk dit asof die verhouding van gene in bekende biologiese substelsels gemodelleer word. Dit blyk of die model gebaseer op die gesamentlike voorkoms van gene die verband tussen groepe van funksionele verbonde gene modelleer om die onderliggende dinamiese eienskappe van die experiment te verduidelik.
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Fairfield, Charles Alexander. "Soil-structure interaction in arch bridges." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/13809.
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European Community directives now insist upon the imposition of 11.5t axle weights for the assessment of highway bridges and structures. This need for heavier loads arises from the Community wide harmonisation of transport policy. Its successful implementation requires the urgent assessment of our bridge stock of some 75000 masonry arches. The analysis of arch bridges has long lacked an accurate method of assessing the loads transmitted to the arch ring by the surrounding soil. This thesis proposes pressure distributions suitable for use in the analysis of arch bridges. It examines, by way of instrumented small scale and in-situ tests, the soil-structure interaction effects arising from the backfill material. Observations of zones of soil displacement around a loaded arch are made in order to better describe the interactive effects. A finite element analysis of the instrumented tests was done and a parametric study was used to assess the effects of various material properties upon the system's behaviour. The inclusion of the interactive effects observed, and modelled, intends to lead to cost savings in the arch bridge assessment programme by reducing the conservatism inherent in the most common assessment methods. Design curves incorporating soil-structure interaction effects are presented where significant capacity increases can be seen compared with analyses ignoring the effects.
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Sim, Jackie H. H. "Human-structure interaction in cantilever grandstands." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:78fa0288-7567-4ea0-83f6-c7e921f6697f.
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There is a risk that excessive vibration in long span cantilever grandstands can be triggered by the spectators synchronising their jumps to the music played. If the jumping frequency excites a resonance of the grandstand, large force could be generated. This thesis studies human-structure interaction in cantilever grandstands, with emphasis on modelling the passive and jumping crowds, and analysing the response of a single degree-of-freedom (SDOF) structural system. Preliminary work on analysing a cantilever occupied by seated humans shows that it is acceptable to use a SDOF structural system for analysis which meant emphasis of later work could be placed on understanding the interaction between a passive crowd and the structure. Human dynamic models from published biomechanics studies are used to develop a passive crowd model. A transfer function, fitted to the crowd apparent mass, is used to define the crowd model. It is found that the passive crowd can be approximated well by using a single 2DOF system. The combined passive crowd-structure system is modelled as a feedback system and a parametric study is conducted. It is found that the passive crowd adds significant mass and damping to the structure and these effects vary with the natural frequency of the structure. Records of forces of people jumping to a beat are used to develop a probabilistic model of crowd jumping loads. Key parameters are introduced to characterise the timing and shape of the jumping impulses. An analytical function is used to approximate the impulse shape. All parameters are characterised with probability distribution functions. Using the fitted probability distribution functions, the Monte Carlo method is used to simulate individual jumping load-time histories and to obtain the structural responses due to group jumping loads. The variations of the structural response with the natural frequency of the empty structure and the size of the active crowd are presented in charts. As expected, the worst response is found on structures with natural frequencies coinciding with the first three harmonics of the crowd jumping loads. For structures occupied by passive crowds, a significant reduction in the structural response is found at resonance excited by the second and third harmonics, due to high levels of damping provided by the passive crowds. On variation of the structural response with the crowd size, it is found that the structural response becomes asymptotic for groups larger than 16 people. Experimental individual jumping and bobbing tests are conducted at six distinct beat frequencies to look at the variations of the impulse shape and degree of synchronisation with the beat frequency. The bobbing action is found to have a higher inherent variability between individuals compared to jumping. Jumping tests involving two people facing each other are also conducted. The results show that there is a better synchronisation when two people are jumping together compared to when jumping alone.
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Altstadt, Eberhard, Helmar Carl, and Rainer Weiß. "Fluid-Structure Interaction Investigations for Pipelines." Forschungszentrum Rossendorf, 2003. https://hzdr.qucosa.de/id/qucosa%3A21726.
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The influence of the fluid-structure interaction on the magnitude fo the loads on pipe walls and support structures is not yet completely understood. In case of a dynamic load caused by a pressure wave, the stresses in pipe walls, especially in bends, are different from the static case.
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Taherzadeh, Reza. "Seismic soil-pile group-structure interaction." Châtenay-Malabry, Ecole centrale de Paris, 2008. http://www.theses.fr/2008ECAP1096.
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Si la prise en compte de l'interaction sol-structure peut être abordée de façon relativement simple dans la plupart des fondations superficielles, il n'en est pas de même pour des groupes de pieux. Les principales difficultés rencontrées sont liées à la complexité et à la taille du modèle numérique nécessaire à l’analyse détaillée. Cette thèse porte sur la modélisation de l’interaction dynamique sol-structure dans le cas particulier des fondations comportant un grand nombre de pieux. Ce travail consiste à faire des modélisations avancées en utilisant un couplage entre le logiciel MISS3D d’éléments de frontière pour des milieux élastiques stratifiés et la toolbox matlab d’éléments finis SDT pour la modélisation des fondations et des structures. Après avoir validé la modélisation à partir de solutions de la littérature, les principaux paramètres gouvernant l’impédance de ces fondations ont été mis en évidence. Les modèles simplifiés de ces impédances ont ensuite été développés dans le cas de pieux flottants ou de pieux encastrés dans un bedrock. Des paramètres de ces modèles simplifiés ont été déterminés par des analyses statistiques fondées sur une base étendue de modèles numériques couvrant une large gamme de situations pratiques. Ces modèles approchés ont été validés sur des cas particuliers, puis différents spectres de réponse modifiés par la prise en compte de l’interaction sol-structure ont été proposésDespite the significant progress in simple engineering design of surface footing with considering the soil-structure interaction (SSI), there is still a need of the same procedure for the pile group foundation. The main approach to solve this strongly coupled problem is the use of full numerical models, taking into account the soil and the piles with equal rigor. This is however a computationally very demanding approach, in particular for large numbers of piles. The originality of this thesis is using an advanced numerical method with coupling the existing software MISS3D based on boundary element (BE), green's function for the stratified infinite visco-elastic soil and the matlab toolbox SDT based on finite element (FE) method to modeling the foundation and the superstructure. After the validation of this numerical approach with the other numerical results published in the literature, the leading parameters affecting the impedance and the kinematic interaction have been identified. Simple formulations have then been derived for the dynamic stiffness matrices of pile groups foundation subjected to horizontal and rocking dynamic loads for both floating piles in homogeneous half-space and end-bearing piles. These formulations were found using a large data base of impedance matrix computed by numerical FE-BE model. These simple approaches have been validated in a practical case. A modified spectral response is then proposed with considering the soil-structure interaction effect
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Brahimi, Malek. "Structure turbulente des panaches thermiques : interaction." Poitiers, 1987. http://www.theses.fr/1987POIT2282.
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Toubalem, Franck. "Interaction sol-structure en milieu stochastique." Ecully, Ecole centrale de Lyon, 1996. http://bibli.ec-lyon.fr/exl-doc/TH_T1669_ftoubalem.pdf.
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En vue d'améliorer la modération de l'lnteraction Sol-Structure, pour des ouvrages "à risque", et d'évaluer par là meme, leurs marges de dimensionnements sous séisme, plusieurs pays se sont associés pour développer un projet international. Ce dernier repose sur la construction d'une maquette instrumentale d'un batiment réacteur de Centrale Nucleaire à l'échelle 1/4, sur le site actif de Hualien (Taiwan). Cette étude succède au projet Lotung qui était l'analogue sur un sol beaucoup plus mou. Les tests de vibrations forcées de cette structure parfaitement axisymétrique font apparaitre deux fréquences de résonance du mode de balancement nettement différentes, dans deux directions orthogonales. Un modèle de sol homogene, aussi sophistiqué soit-il, ne permet pas d'expliquer cet écart. Ainsi pour pallier cette faiblesse, cette thèse propose une interprétation possible du phénomène, via l'intégration de données statistiques qui prennent en compte la variability spatiale à l'échelle macroscopique des caractéristiques mécaniques du sol. Pour appréhender cette nouvelle approche probabiliste et des délicats problèmes adjoints, notre demarche s'articule autour de trois parties relativement independantes les unes des autres, mais néanmoins complémentaires. Dans un premier temps, on établit une synthèse bibliographique sur l'aspect expérimental de ce projet Hualien, et les résultats importants sont exhibés. Dans un deuxième temps, on considère une structure rigide dont le mouvement est successivement décrit par deux puis trois degrés de liberté (respectivement en mono puis en bidimensionnel). Pour traduire les hétérogénéités naturelles du sol et son caractère non deterministe qui en decoule, le corps rigide est supporté par un continuum de ressorts à caractéristiques stochastiques. Dans le cas du tassement, on retrouve ainsi des résultats qui, jusqu'à présent, avaient été seulement observés à l'aide de modèles aux éléments finis, couteux sur le plan numerique. En dynamique, on quantifie d'une part, la dispersion statistique des grandeurs modales (valeurs propres, et fonction de transfert), et d'autre part, on fait apparaître un couplage entre les modes de pompage et de balancement engendré par la prise en compte d'un aléa dans le sol. On met egalement en évidence l'importance du paramètre adimensionnel u ; dans le cas où ce dernier est égal à 3, on retrouve à l'aide du modèle de Winkler bidimensionnel, l'écart expérimental observé. Pour finir, une dernière partie consiste à étudier des milieux continument aléatoires. Dans le cas d'une colonne de sol, l'équation différentielle à coefficients aléatoires est ramenée, grâce à un traitement mathématique original, au cas connu de l'équation d'Helmoltz. Par ailleurs, on examine la question des atténuations liées à ces types de modeles : on montre que l'atténuation "apparente", mise en oeuvre par manipulation d'opérateurs stochastiques n'a pas de sens physique; elle n'existe qu'au travers d'un effet de lissage suscité exclusivement par l'espérance mathématique. En revanche, si on s'intéresse a un modèle de sol constitueé par un continuum de colonnes dont les caractéristiques sont non-déterministes, l'atténuation des amplitudes des pics de résonance est d'autant plus prononcée que la fréquence augmente. Par conséquent, considerer les propriétés mécaniques moyennes d'un tel milieu, ne va pas engendrer la fonction de transfert en déplacement la plus représentative.
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Holder, Justin. "Fluid Structure Interaction in Compressible Flows." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin159584692691518.
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Cormier, Anthony. "Interaction tubuline-nucléotide : structure et biochimie." Paris 6, 2009. http://www.theses.fr/2009PA066030.
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Les microtubules sont des composants clefs du cytosquelette des cellules eucaryotes, ils alternent des phases d’assemblage et de désassemblage, un processus appelé instabilité dynamique. La tubuline qui constitue les microtubules est une protéine hétérodimérique liant deux nucléotides guanosine, l’un au site non-échangeable, l’autre au site échangeable. Au cycle de polymérisation/dépolymérisation des microtubules est associé un cycle nucléotidique au cours duquel la tubuline échange son nucléotide en solution et l’hydrolyse ensuite lors de son assemblage. L’objectif de ma thèse a été de caractériser l’interaction de la tubuline avec le nucléotide échangeable. Nous avons d’abord montré que son activité GTPase nécessite l’intervention de deux tubulines pour se produire et qu’elle n’est efficace que lorsque les tubulines sont positionnées bout à bout en conformation droite. Nous avons également montré que l’échange du nucléotide est unimoléculaire. Cet échange est rendu possible par la flexibilité générale du site ainsi que par son libre accès. En résumé, ce travail a permis de mieux comprendre les relations de la tubuline avec son nucléotide.
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Jamois, Eric. "Interaction houle-structure en zone côtière." Aix-Marseille 2, 2005. http://theses.univ-amu.fr.lama.univ-amu.fr/2005AIX22083.pdf.
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Dans le contexte du dimensionnement de structures marines ou côtières soumises à des vagues non-linéaires dans des profondeurs d'eaux variables, il est nécessaire de considérer les interactions vagues/structure et vagues/vagues sur de grands domaines. Dans cette optique, un modèle de type Boussinesq d'ordre élevé a été développé et a permis d'étudier les interactions non-linéaires susceptibles d'apparaître entre des vagues régulières, d'incidence normale ou oblique, et une structure de type parallélépipédique verticale dans toute la colonne d'eau. Plusieurs applications du modèle sur des cas concrets mettant en jeu des interactions non-linéaires vagues/structure d'ordre élevé, sont présentées. Une étude exhaustive d'un nouveau phénomène physique non-linéaire entraînant de fortes amplifications des vagues au devant de structures réfléchissantes est aussi menéeFor the design of marine or coastal structures subject to nonlinear waves in deep to shallow water, it is crucial to take into account both wave/structure and wave/wave interactions on large fluid domains. In this purpose, a high-order Boussinesq-type model has been developed and used to investigate nonlinear wave interactions with piecewise rectangular bottom-mounted (surface piercing) structures. Several practical applications of the model involving highly nonlinear wave run-up on a rigid plate are presented. Both normal and oblique wave conditions are considered. A new physical phenomenon creating large wave amplification in front of reflective structures is also fully studied
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Brahimi, Malek. "Structure turbulente des panachés thermiques interaction /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376034157.
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Saez, Robert Esteban Modaressi Arézou. "Interaction dynamique non-linéaire sol-structure." S. l. : Ecole centrale de Paris, 2009. http://theses.abes.fr/2009ECAP0012.
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Ritter, Stefan. "Experiments in tunnel-soil-structure interaction." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273891.
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Urbanisation will require significant expansion of underground infrastructure, which results in unavoidable ground displacements that affect the built environment. Predicting the interaction between a tunnel, the soil and existing structures remains an engineering challenge due to the highly non-linear behaviour of both the soil and the building. This thesis investigates the interaction between a surface structure and tunnelling-induced ground displacements. Specifically, novel three-dimensionally printed building models with brittle material behaviour, similar to masonry, were developed and tested in a geotechnical centrifuge. This enabled replication of building models with representative global stiffness values and realistic building features including strip footings, intermediate walls, a rough soil-structure interface, building layouts and façade openings. By varying building characteristics, the impact of structural features on both the soil and building response to tunnelling in dense sand was investigated. Results illustrate that the presence of surface structures considerably altered the tunnelling-induced soil response. The building-to-tunnel position notably influences the magnitude of soil displacements and causes localised phenomena such as embedment of building corners. An increase of the façade opening area and building length reduces the alteration of the theoretical greenfield settlements, in particular the trough width. Moreover, the impact of varying the building layout is discussed in detail. For several building-tunnel scenarios, building distortions are quantified and the crucial role of building features is demonstrated. Structures spanning the greenfield inflection point experienced more deformation than identical structures positioned in either sagging or hogging, and partitioning a structure either side of the greenfield inflection point is shown to lead to unconservative damage assessments. Results also quantify the significant extent to which structural distortions increase as façade openings and building length increases. Observed building damage and cracking patterns confirm the reported trends. The experimental results are used to evaluate the performance of available methods to assess the behaviour of buildings to tunnelling. Predictions ignoring soil-structure interaction are usually overly conservative, while approaches based on the relative stiffness of a structure and the soil result in inconsistent predictions, though some methods performed better than others. Practical improvements to consider structural details when assessing this tunnel-soil-structure system are finally proposed.
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Roussillon, Pierre. "Interaction sol-structure et interaction site-ville : aspects fondamentaux et modélisation." Lyon, INSA, 2006. http://theses.insa-lyon.fr/publication/2006ISAL0008/these.pdf.
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La réévaluation sismique du bâti existant est un enjeu de sécurité majeur. Dans ce cadre a été effectuée une étude de l'interaction sol-structure (ISS) destinée à orienter l'auscultation du bâti et être intégrée dans un premier diagnostic de vulnérabilité. Elle s'inscrit dans une approche basée sur l'établissement de modèles simples de comportement dynamique issus de la confrontation du comportement supposé de la structure avec des données recueillies in situ par la méthode du bruit de fond, de l'excitation harmonique ou des chocs. Le choix d'une représentation simplifiée de l'ISS, autorisant un calcul analytique des fonctions d'impédances, a permis de déterminer, pour chacun des modèles les plus courants de structures, les paramètres adimensionnels essentiels qui gouvernent le phénomène puis d'estimer, selon les valeurs de ces paramètres, la nature et l'importance de l'effet de l'ISS sur les caractéristiques modales du système. Avec le même souci de privilégier les approches analytiques ou semi-numériques, des modèles basses fréquances ont été développés pour appréhender le phénomène d'interaction site-ville (ISV), autrement dit l'effet d'une urbanisation dense sur le champ d'onde sismique. Une première approche macroscopique, correspondant à une homogénéisation périodique des conditions aux limites en surface, a permis d'identifier le paramètre significatif du couplage mécanique entre le sol et la ville puis d'évaluer l'effet de l'interaction site-ville sur l'amplitude et la durée de la réponse sismique. Une deuxième approche, basée sur une formulation simplifiée et néanmoins réaliste du champ d'onde émis par chaque bâtiment, conduit à définir une couche limite pour décrire les interactions multiples entre sol et bâtiment. L'estimation distincte du mouvement en champ libre ou au niveau d'une fondation est ainsi rendue possibleWe present a dimensional and parametric analysis of soil structure interaction effects, using simple representative models of structure and closed form impedances of cone model. The effect of a dense urban environment on seismic motions is investigated thanks to macroscopic analytical models: as a first approach, the effect of buildings is described by a mean impedance on the soil-city interface. This enables to identify a mechanical soil-city coupling parameter which governs the magnitude of the interaction, and to determine a characteristic time of the soil-city response. A second more refined model based on approximated wave fields radiated by each building lead to introduce a boundary layer to describe the multiple interactions effect. This work highlights the main mechanisms and governing parameters of single and multiple interaction phenomenon
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Roussillon, Pierre Boutin Claude. "Interaction sol-structure et interaction site-ville aspects fondamentaux et modélisation /." Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?id=roussillon.
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Aldaikh, Hesham S. H. "Discrete models for the study of dynamic structure-soil-structure interaction." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633205.
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The problem of Dynamic Structure-Soil-Structure Interaction (SSSI) refers to the mutual interaction of adjacent buildings in built-up high density areas through the underlying soil under earthquake excitation. Due to the complexity of the problem, past studies have mainly considered the use of intricate mathematical formulations or the computationally demanding numerical Finite Element and Boundary Element methods. In the present study, linear elastic two-dimensional formulations are proposed using simple discrete lumped parameter models for structures and soil for groups of two and three adjacent buildings systems. The formulation includes a rotational spring as a key buildings interaction mechanism. Inverse power laws are proposed for this rotational interaction and for soil/foundation springs stiffnesses which turn out to be functions of spacing between adjacent buildings. These relationships are obtained by equating energies from the low order discrete and high order Finite Element models.
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phelipot, Annabelle. "Interaction sol-structure lors d'opérations de microtunnelage." Phd thesis, INSA de Lyon, 2000. http://tel.archives-ouvertes.fr/tel-00003398.
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Ce travail s'inscrit dans le cadre du Projet National de Recherche français "Microtunnels". Le microtunnelage est une technique de pose de canalisations sans tranchée. Elle consiste à foncer la canalisation à l'arrière d'un microtunnelier ayant les fonctions d'excavation, de marinage et de guidage. Cette méthode récente, permettant de réduire les nuisances liées à la pose des réseaux en tranchée, se développe principalement dans le cadre du génie civil urbain.Cette étude essentiellement expérimentale concerne les problèmes liés au frottement à l'interface sol-canalisation, à la stabilité du front de taille, et enfin aux mouvements induits au sein du massif de sol traversé.
Une première phase d'observations de terrain, basée sur le suivi complet de chantiers de microtunnelage dans des conditions de sol diverses, comportait la caractérisation des terrains traversés ainsi que l'enregistrement des principaux paramètres de fonçage et de pilotage. L'interprétation de ces données a permis de mettre en évidence l'incidence de la nature des terrains, de la surcoupe, de la lubrification et des problèmes de guidage sur les frottements mobilisés, sans permettre toutefois de toujours faire la part de chacun de ces paramètres. Les problèmes de stabilité du front et leur incidence sur les mouvements du sol ont pu également être observés et analysés.
A partir de ces résultats, une étude complémentaire, dans des conditions bien contrôlées, a été entreprise dans une chambre de calibration adaptée à la modélisation du fonçage de canalisations. Les essais réalisés ont permis de cerner plus précisément l'incidence de la surcoupe et de l'injection de lubrifiant sur les frottements mobilisés et sur les mouvements engendrés dans le massif. L'incidence de la surcoupe a été modélisée à l'aide de simulations numériques bidimensionnelles en vue de l'extension aux conditions in situ.
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Yogendrakumar, Muthucumarasamy. "Dynamic soil-structure interaction : theory and verification." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29222.
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A nonlinear effective stress method of analysis for determining the static and dynamic response of 2-D embankments and soil-structure interaction systems is presented. The method of analysis is incorporated in the computer program TARA-3. The constitutive model in TARA-3 is expressed as a sum of a shear stress model and a normal stress model. The behavior in shear is assumed to be nonlinear and hysteretic, exhibiting Masing behavior under unloading and reloading. The response of the soil to uniform all round pressure is assumed to nonlinearly elastic and dependent on the mean normal effective stresses.
The porewater pressures required in the dynamic effective stress method of analysis are obtained by the Martin-Finn-Seed porewater pressure generation model modified to include the effect of initial static shear. During dynamic analysis, the effective stress regime and consequently the soil properties are modified for the effect of seismically induced porewater pressures.
A very attractive feature of TARA-3 is that all the parameters required for an analysis may be obtained from conventional geotechnical engineering tests either in-situ or in laboratory.
A novel feature of the program is that the dynamic analysis can be conducted starting from the static stress-strain condition which leads to accumulating permanent deformations in the direction of the smallest residual resistance to deformation. The program can also start the dynamic analysis from a zero stress-zero strain condition as is done conventionally in engineering practice.
The program includes an energy transmitting base and lateral energy transmitting boundaries to simulate the radiation of energy which occurs in the field.
The program predicts accelerations, porewater pressures, instantaneous dynamic deformations, permanent deformations due to the hysteretic stress-strain response, deformations due to gravity acting on the softening soil and deformations due to consolidation as the seismic porewater pressures dissipate.
The capability of TARA-3 to model the response of soil structures and soil-structure interaction systems during earthquakes has been validated using data from simulated earthquake tests on a variety of centrifuged models conducted on the large geotechnical centrifuge at Cambridge University in the United Kingdom. The data base includes acceleration time histories, porewater pressure time histories and deformations at many locations within the models. The program was able to successfully simulate acceleration and porewater pressure time histories and residual deformations in the models.
The validation program suggests that TARA-3 is an efficient and reliable program for the nonlinear effective stress analysis of many important problems in geotechnical engineering for which 2-D plane strain representation is adequate.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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De, Nayer Guillaume. "Interaction Fluide-Structure pour les corps élancés." Phd thesis, Ecole centrale de nantes - ECN, 2008. http://tel.archives-ouvertes.fr/tel-00820472.
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Les moyens de calcul actuels conduisent les différentes disciplines scientifiques à se rapprocher, afin de prendre en compte des phénomènes physiques de plus en plus complexes. Ainsi, un axe de recherche de l'Équipe de Modélisation Numérique du Laboratoire de Mécanique des fluides UMR6598 de l'École Centrale Nantes est l'Interaction Fluide-Structure (IFS). Dans ce contexte, le développement d'un solveur structure grand déplacement, limité aux corps élancés, puis son couplage avec le code RANSE volumes-finis non-structuré ISIS ont été réalisés. Le solveur poutre s'appuie sur la théorie de Cosserat et sur la méthode dite 'géométriquement exacte'. Une attention particulière a été portée au couplage en espace sur les interpolations et au transfert des informations à l'interface fluide-structure, afin d'être le plus précis possible et d'assurer la conservation des efforts. Le code poutre pouvant prendre en compte de grands mouvements, une technique originale a dû être écrite pour mettre à jour le domaine de calcul fluide. Elle se base sur l'approche pseudo-solide, et permet via une loi de comportement locale du pseudo-solide, de contrôler finement la déformation du maillage. Chaque partie du code IFS a été validée : le solveur poutre sur des cas-tests 2D/3D, en statique et en dynamique, en petit et grand déplacement; le module de remaillage sur des géométries variées et en calcul parallèle. Enfin, quelques applications IFS ont été traitées : deux exemples bidimensionnels, l'un stationnaire, l'autre très instationnaire; puis, le programme a montré ses possibilités en tridimensionnel sur un câble déformable fixé à une extrémité et subissant un courant, ou encore un riser tracté dans un environnement multifluide au repos.
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Gregson, James. "Fluid-structure interaction simulations in liquid-lead." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/12340.
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An Eulerian compressible flow solver suitable for simulating liquid-lead flows involving fluid-structure interaction, cavitation and free surfaces was developed and applied to investigation of a magnetized target fusion reactor concept. The numerical methods used and results of common test cases are presented. Simulations were then performed to assess the smoothing properties of interacting mechanically generated shocks in liquid lead, as well as the early-time collapse behavior of cavities due to free surface reflection of such shocks. An empirical formula to estimate shock smoothness based on the shock smoothing results is presented, and issues related to shock driven cavity collapse in liquid liner magnetized target fusion reactors are presented and discussed.
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Sun, Hepn Wing. "Ground deformation mechanisms for soil-structure interaction." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303931.
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Stallard, Timothy J. "Simulation of unsteady viscous flow-structure interaction." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418130.
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The design of slender structures such as longspan bridges, masts, offshore risers and cables is strongly influenced by their response behaviour when subjected to unsteady loads due to wind, waves and current. Simulation of the behaviour of a viscous flow past a structural cross section is of great importance to engineers concerned with the design of such structures. Offshore engineers are concerned with estimating the magnitude of structural forces induced by the most severe storm-induced wave events. Numerous studies have been conducted in an effort to estimate the structural forces induced by both regular and irregular waves. However, estimation of the maximum extreme wave-induced structural forces, particularly for relatively small diameter horizontal components, has received less attention. Since the most widely used method for estimating the force experienced by a bluff body subjected to wave loading is the empirical drag-inertia equation developed by Morison, O’ Brien, Johnson, and Schaaf (1950), it is important to determine whether this equation is adequate to describe the forces imposed by extremely large ocean waves. A method is presented for the simulation of incompressible viscous flow past acylinder using a stream function vorticity-transport formulation discretised on a cutcell quadtree mesh. A cut-cell technique is employed to provide accurate boundary representation and to facilitate the simulation of flow past a moving boundary. The finite volume discretisation consists of second-order accurate central difference approximations within uncut flow cells and a polynomial reconstruction technique within the cut-cells that are intersected by the solid boundary. Several preliminary validation tests concerned with flow past a circular cylinder are presented to confirm the accuracy of the numerical model. Firstly, the cut-cell discretisation is applied to the solution of the Euler equations and is shown to be almost second order accurate. Comparisons of wake geometry and force coefficients for steady and oscillatory flows at low Reynolds number are then made with existing results, and show satisfactory agreement. Preliminary tests are presented to assess the accuracy of a cut-cell based method for simulating flow past a circular body that moves across a background mesh. A series of experiments is also presented concerned with the measurement of theforce experienced by a circular cylinder undergoing a pre-defined two-dimensionalmotion within a still fluid. The cylinder trajectory is representative of the motionof a fluid particle beneath an idealised large ocean wave as defined by the NewWave formulation (Tromans et al. 1991). It is observed that, whilst the magnitude of high frequency vortex induced force fluctuations varies with the ratio of wave amplitude to cylinder diameter (A=D) and the wave spectrum shape, the overall shape of both x- and y-direction force time histories is very similar for all wave groups for which the underlying spectrum has the same shape. For all of the two-dimensional cylinder motions considered, the spectrum of both measured forces closely approximates the spectrum of uq (where u is a component of the velocity vector and q the absolute velocity) and, as a result, the vector form of the well known equation developed by Morison et al. (1950) is shown to provide a satisfactory estimate of the cartesian force components. The high frequency component of the force that is not captured by the Morison et al. equation is clearly identified as a lift-type force in the radial direction. For design purposes, a reasonable estimate of the magnitude of the peak force is obtained by neglecting inertial forces and employing a drag coefficient CD = 1.0.
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David, Thevaneyan Krishta David. "Integral bridges: modelling the soil-structure interaction." Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581881.
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Integral abutment bridges, also known as integral bridges, have become one of the most common types of joint-less bridge construction, certainly over the last three decades. Their principal advantages are derived from the elimination of expansion joints and bearings, making them a very cost-effective system in terms of construction, maintenance, and longevity. The elimination of joints from bridges creates a significant soil-structure interaction behind the abutment and the piles generating an interesting problem since the response of the different elements of the integral bridge are interdependent. This research project used numerical analyses to investigate the complex interactions that exist between the structural components of the stub-type integral abutment bridge and the backfill soil. Where possible, these results were validated with existing field data. A literature review was conducted to gain an insight into the behaviour of integral abutment bridges, particularly the soil-structure interaction of integral bridges. To gain a better understanding of the behaviour of integral abutment bridges and their interaction with the backfill soil adjacent to the abutment and the piles, particularly due to thermally induced movement/loads, a 2D finite element analysis was performed on a typical integral abutment bridge using OASYS GSA and OASYS SAFE. The results from this research are believed to help answer two of the most debated issues with respect to stub-type integral abutment bridge-soil interaction analyses. Firstly, it is clear, and now possible, that a reliably accurate soil profile is used in the analysis/design. The Mohr-Coulomb soil model was found to realistically represent the soil behaviour. Secondly, the research may suggest that cyclic movements / loads may not significantly influence the overall behaviour of integral abutment bridges. In addition, it was found that the development of earth pressure behind the integral abutment is significantly affected by the backfill soil properties and is a function of the integral abutment displacement. Limiting values for the abutment displacement, which induces maximum backfill pressure, have been suggested. The soil separation phenomenon (gapping) was also found to significantly affect the backfill/foundation soil-load relationship behaviour. Implications· of this research for practising engineers and recommendations for future research work are also included.
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Dewsbury, Jonathan J. "Numerical modelling of soil-pile-structure interaction." Thesis, University of Southampton, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582152.
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Soil-pile-structure interaction analysis is the simultaneous consideration of the structural frame, pile foundations, and the soil forming the founding material. Failure to consider soil-pile-structure interaction in design will lead to a poor prediction of load distribution within the structure. A poor prediction of load distribution will cause the structure to deform under loads that have not been calculated for. This may result in the structure cracking or the overstressing of columns. If the actual load distribution significantly differs from that designed for, the factor of safety on structural elements may be substantially decreased. Despite the importance, there are currently no studies quantifying the effect of soil-pile-structure interaction for simple office structures. As a result the effects of soil-pile-structure interaction are often deemed unimportant, and ignored in the design of simple structures. Numerical methods are often relied upon to consider soil-pile-structure interaction for complex structures, such as tall towers. However in their current form they are limited because the meshes required for analysis, especially when in three dimensions, are difficult to verify, and take a long time to set up and run. Therefore this thesis proposes a meshing method within the framework of the finite element method that allows large, complex, and non-symmetrical pile foundation layouts to be meshed in a manner that is quick, can be easily checked, and significantly reduces the analysis run time. Application of the meshing method to an office structure (recently designed for the 2012 Olympic Games) has allowed the effects of soil-pile-structure interaction to be quantified. The subsequent normalisation of the results provides a method for assessing when it is necessary to consider soil- pile-structure interaction in future design. Comparison between the monitored performance of 'The Landmark' (a 330m tower founded on a piled raft) and numerical predictions have demonstrated the importance of correct ground stiffness selection for achieving accurate predictions of piled raft settlement, and load distribution. The role of single pile load tests and in situ testing for ground stiffness selection for piled raft design has also been assessed
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Zolghadr, Zadeh Jahromi Hamid. "Partitioned analysis of nonlinear soil-structure interaction." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512070.
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Blair, Stuart R. "Lattice Boltzmann Methods for Fluid Structure Interaction." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/17325.
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Approved for public release; distribution is unlimitedThe use of lattice Boltzmann methods (LBM) for fluid flow and its coupling with finite element method (FEM) structural models for fluid-structure interaction (FSI) is investigated. A body of high performance LBM software that exploits graphic processing unit (GPU) and multiprocessor programming models is developed and validated against a set of two- and three-dimensional benchmark problems. Computational performance is shown to exceed recently reported results for single-workstation implementations over a range of problem sizes. A mixed-precision LBM collision algorithm is presented that retains the accuracy of double-precision calculations with less computational cost than a full double-precision implementation. FSI modelling methodology and example applications are presented along with a novel heterogeneous parallel implementation that exploits task-level parallelism and workload sharing between the central processing unit (CPU) and GPU that allows significant speedup over other methods. Multi-component LBM fluid models are explicated and simple immiscible multi-component fluid flows in two-dimensions are presented. These multi-component fluid LBM models are also paired with structural dynamics solvers for two-dimensional FSI simulations. To enhance modeling capability for domains with complex surfaces, a novel coupling method is introduced that allows use of both classical LBM (CLBM) and a finite element LBM (FELBM) to be combined into a hybrid LBM that exploits the flexibility of FELBM while retaining the efficiency of CLBM.
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Taunton, Paul R. "Centrifuge modelling of soil/masonry structure interaction." Thesis, Cardiff University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244112.
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Callaway, Phillip Arthur. "Soil-structure interaction in masonry arch bridges." Thesis, University of Sheffield, 2007. http://etheses.whiterose.ac.uk/3036/.
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Cadby, Jonathan R. "Wave/structure interaction in two-layer fluids." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/7554.
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Nitikitpaiboon, Chanwut. "Finite element formulations for fluid-structure interaction." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/37500.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1993.Includes bibliographical references (leaves 123-128).
by Chanwut Nitikitpaiboon.
Ph.D.
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Siddorn, Philip David. "Efficient numerical modelling of wave-structure interaction." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:de36bd2f-cd23-4f11-b67f-9d8cd48ecd3c.
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Offshore structures are required to survive in extreme wave environments. Historically, the design of these offshore structures and vessels has relied on wave-tank experiments and linear theory. Today, with advances in computing power, it is becoming feasible to supplement these methods of analysis with fully nonlinear numerical simulation. This thesis is concerned with the development of an efficient method to perform this numerical modelling, in the context of potential flow theory. The interaction of a steep ocean wave with a floating body involves a moving free surface and a wide range of length scales. Attempts to reduce the size of the simulation domain cause problems with wave reflection from the domain edge and with the accurate creation of incident waves. A method of controlling the wave field around a structure is presented. The ability to effectively damp an outgoing wave in a very short distance is demonstrated. Steep incident waves are generated without the requirement for the wave to evolve over a large time or distance before interaction with the body. This enables a general wave-structure interaction problem to be modelled in a small tank, and behave as if it were surrounded by a large expanse of water. The suitability of the boundary element method for performing this modelling is analysed. Potential improvements are presented with respect to accuracy, robustness, and computational complexity. Evidence of third order diffraction is found for an FPSO model.
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Paquette, Yves. "Interaction Fluide-Structure et Érosion de Cavitation." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI104/document.
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Lorsqu’un liquide est soumis à de fortes dépressions, des bulles de gaz etde vapeur peuvent apparaître en son sein. Ce phénomène est appelé cavitation Ces bulles sont susceptibles d’imploser dans les zones de surpression etd’endommager les parois solides environnantes à travers la création d’écoulements violents. Dans les applications industrielles, ce phénomène d’érosionpar cavitation peut réduire la durée de vie des machines hydrauliques. Dans ledomaine biomédical, le phénomène d’érosion par onde de choc est utilisé pourl’ablation de tissus mous ou la destruction de calculs rénaux.Dans ce travail, à caractère numérique, nous nous intéressons à une bulled’air isolée implosant au voisinage d’une paroi déformable sous l’effet d’unesurpression générée par une onde de choc incidente. Le travail de thèse aconsisté à mettre en place un couplage fluide structure pour simuler le phénomène d’implosion de la bulle dans la partie fluide et la déformation plastiqueengendrée dans la partie solide. Pour cela, une stratégie en deux étapes a étémise en oeuvre. La première étape a consisté à construire un code fluide avecmaillage mobile pour gérer le déplacement de l’interface fluide/solide. Le codedéveloppé est dérivé du modèle numérique développé par Eric Johnsen et al.à University of Michigan dans lequel nous avons implémenté une méthodeALE (Arbitrary Lagrangian Eulerian) permettant de passer d’une descriptioneulérienne sur maillage fixe à une description eulérienne sur maillage mobile.La seconde étape a consisté à modéliser la déformation élasto-plastique de lapartie solide au cours de l’implosion de la bulle grâce à un couplage fort ducode fluide avec le logiciel CAST3M. La communication entre les deux codesutilise la bibliothèque MPI.A l’issue du couplage, nous avons été en mesure de simuler l’implosiond’une bulle d’air à proximité d’une paroi déformable. Nous avons pu calculerle niveau de déformation de la paroi solide ainsi que l’amortissement de la sur-pression en paroi pour plusieurs matériaux. L’outil numérique ainsi développépermettra à terme d’étudier le comportement de revêtements amortissants capables de protéger des structures industrielles de l’érosion de cavitation oud’optimiser les effets bénéfiques des traitements par onde de choc dans lesapplications biomédicalesHis numerical work focuses on the collapse of a single air bubble close to adeformable wall generated by the impact of an incident high-pressure wave. A CFD code was fully coupled to a FEM solid code in order to compute the bubble collapse and the subsequent plastic deformation in the material. The CFD code was developed from the numerical model of Johnsen et al. (University of Michigan). A mobile mesh capability was added in order to account for the displacement of the fluid-structure interface. An ALE (Arbitrary LagrangianEulerian) method was implemented to switch from an Eulerian description in a fixed mesh to an Eulerian description in a moving mesh. The solid response to bubble collapse was computed with the FEM software CAST3M (developed by CEA) assuming an elastic-plastic constitutive law for the material. The communication between the two codes is achieved through the MPI library.For the CFD code, bubble collapse dynamics was validated by comparison with two others codes: research software CaviFlow and commercial software Ansys Fluent. The coupling between the CFD and the FEM code was validated on the case of the impact of a wave on an elastic medium.The paper will present a detailed analysis in 2D of both the dynamics of bubble collapse and solid behaviour for various conditions. They were obtained by changing the amplitude of the incident shock wave, the standoff distance and the material properties. Special attention will be given to the shock wave that forms when the microjet hits the bubble interface and to the impact of this shock wave on the material surface. In particular, the damping of the impactpressure with respect to a perfectly rigid wall was computed as well as the plastic deformation of the material surface. These final data gave us crucial information about the requirement of taking account of fluid-structure interaction in numerical modeling of cavitation erosion
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Gout, d'Henin Emmanuelle. "Ondes de Stoneley en interaction fluide-structure." Poitiers, 2002. http://www.theses.fr/2002POIT2263.
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Cevaer, Franck. "Interaction sol-structure. Modélisation des fonctions d'impédance." Nantes, 1993. http://www.theses.fr/1993NANT2009.
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L' interaction sol-structure en dynamique caractérisée usuellement par les fonctions d'impédance doit être prise en compte des la conception des ouvrages tant pour les fondations de machine que pour les fondations d'ouvrages soumis a l'action sismique. Les fonctions d'impédance relatives à une fondation, un type de sol, et un mode de vibration représentent, sous excitation harmonique, la raideur dynamique complexe du sol. Le travail de bibliographie regroupe l'ensemble des fonctions d'impédance relatives aux fondations superficielles trouvées dans la littérature sous forme paramétrée. Cette étude a permis la réalisation d'un ouvrage: manuel des fonctions d'impédance - fondations superficielles. Y apparaissent les résultats relatifs aux fondations de forme simple (circulaire, rectangulaire et filante) et aux sols de caractéristiques simples (milieu semi-infini, monocouche surmontant soit un substratum rigide, soit un demi-espace). Cet ouvrage permet au concepteur de prendre en compte l'interaction sol-structure dans les cas simples ou au niveau d'avant-projets. Une méthode pratique de prise en compte de l'interaction sol-fondation est développée dans le cas ou le sol peut être assimile a un monocouche homogène et viscoélastique reposant sur un substratum rocheux, et pour une fondation circulaire rigide. Les fonctions d'impédance des modes de translation horizontale et de balancement sont représentées par un modèle discret dont les paramètres, indépendants de la fréquence, sont déterminés par des abaques ou des formules empiriques en fonction de la géométrie sol-fondation du problème. Un amortisseur visqueux de caractéristiques dépendant hyperboliquement de la fréquence est utilise pour rendre compte des effets (en basses fréquences) de l'amortissement interne de la couche de sol. Le modèle fréquentiel ainsi réalise permet d'obtenir des réponses de structures en très bonne corrélation avec celles prenant en compte les fonctions complètes d'impédance
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Nayer, Guillaume de. "Interaction fluide-structure pour les corps élancés." Nantes, 2008. http://www.theses.fr/2008NANT2090.
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Les moyens de calcul actuels conduisent les différentes disciplines scientifiques à se rapprocher, afin de prendre en compte des phénomènes physiques de plus en plus complexes. Ainsi, un axe de recherche de l'Équipe de Modélisation Numérique du Laboratoire de Mécanique des fluides UMR6598 de l'École Centrale Nantes est l'Interaction Fluide-Structure (IFS). Dans ce contexte, le développement d'un solveur structure grand déplacement, limité aux corps élancés, puis son couplage avec le code RANSE volumes-finis non-structuré ISIS ont été réalisés. Le solveur poutre s'appuie sur la théorie de Cosserat et sur la méthode dite ``géométriquement exacte''. Une attention particulière a été portée au couplage en espace sur les interpolations et au transfert des informations à l'interface fluide-structure, afin d'être le plus précis possible et d'assurer la conservation des efforts. Le code poutre pouvant prendre en compte de grands mouvements, une technique originale a dû être écrite pour mettre à jour le domaine de calcul fluide. Elle se base sur l'approche pseudo-solide, et permet via une loi de comportement locale du pseudo-solide, de contrôler finement la déformation du maillage. Chaque partie du code IFS a été validée : le solveur poutre sur des cas-tests 2D/3D, en statique et en dynamique, en petit et grand déplacement; le module de remaillage sur des géométries variées et en calcul parallèle. Enfin, quelques applications IFS ont été traitées : deux exemples bidimensionnels, l'un stationnaire, l'autre très instationnaire; puis, le programme a montré ses possibilités en tridimensionnel sur un câble déformable fixé à une extrémité et subissant un courant, ou encore un riser tracté dans un environnement multifluide au reposThe current computational resources lead the different scientific disciplines to get closer to each other, in order to consider more and more complex phenomena. Thus, one of the axis of research of the CFD Team from École Centrale Nantes is the Fluid-Structure Interaction (FSI). In this context, the development of a large displacement structural solver for elongated bodies and its coupling with the non-structured finite volume RANSE solver, ISIS, has been done. This thin beam solver relies on the Cosserat theory and on the ``geometrically exact'' approach. The space coupling on the interpolations and the information transfer at the fluid-structure interface were realised with caution, in order to be as accurate as possible and to fulfill the load conservation. Since the beam solver can be used for great displacements, an original technique had to be built to update the fluid computational domain. It is based on the pseudo solid approach, which allows a precise control over the mesh deformation through a local behaviour law of the pseudo-solid. Each part of the FSI code has been checked: the structural solver on 2D/3D test-cases, in statics and in dynamics, in small and large displacements; the remeshing module has been tested on various geometries and with MPI. Finally, some FSI applications have been performed: two bidimensional examples, a steady case and a fully unsteady one; then, the program has shown its capabilities in 3D on a deformable cable in a current with a fixed end. The computation of a riser towed in a multifluid environment at rest has also been done and studied
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Le, Nam B. "Structure-Interaction Effects In Novel Nanostructured Materials." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6296.
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Recent advances in experimental and computational methods have opened up new directions in graphene fundamental studies. In addition to understanding the basic properties of this material and its quasi-one dimensional structures, significant efforts are devoted to describing their long ranged dispersive interactions. Other two-dimensional materials, such as silicene, germanene, and transition metal dichalcogenides, are also being investigated aiming at finding complementary to graphene systems with other "wonder" properties. The focus of this work is to utilize first principles simulations methods to build our basic knowledge of structure-interaction relations in two-dimensional materials and design their properties. In particular, mechanical folding and extended defects in zigzag and armchair graphene nanoribbons can be used to modulate their electronic and spin polarization characteristics and achieve different stacking patterns. Our simulations concerning zigzag silicene nanoribbons show width-dependent antiferromagnetic-ferromagnetic transitions unlike the case of zigzag graphene nanoribbons, which are always antiferromagnetic. Heterostructures, build by stacking graphene, silicene, and MoS$_2$, are also investigated. It is found that hybridization alters the electronic properties of the individual layers and new flexural and breathing phonon modes display unique behaviors in the heterostructure compositions. Anchored to SiC substrate graphene nanoribbons are also proposed as possible systems to be used in graphene electronics. Our findings are of importance not only for fundamental science, but they could also be used for future experimental developments.