[pt] Com o objetivo de introduzir a heterogeneidade e o efeito de escala na modelagem numérica de estruturas de concreto, este trabalho contribui para um melhor entendimento de alguns aspectos inerentes a este tipo de estudo. Apresentam-se uma formalização e generalização do modelo de dano distribuído, a partir da identificação do processo de evolução do modelo, desde os trabalhos iniciais até a adoção de relações de compliância inversa. A referida formalização contempla as várias possibilidades para a relação de compliância inicial, variação da direção de ocorrência de dano, aproximações do tensor tangente do referido modelo e para as leis de evolução de dano em tração e em compressão. Discutem-se as limitações dos métodos incrementais-iterativos clássicos na solução de problemas fisicamente não-lineares. As formulações secante e tangente destes métodos, bem como uma revisão dos procedimentos de controle mais utilizados são apresentadas. Um método que tem a variação das deformações como parâmetro controlador é proposto e suas formulações secante e tangente são mostradas. As evidências experimentais dos fenômenos associados com a heterogeneidade e efeito de tamanho em estruturas de concreto, bem como os estudos teóricos destinados a representá-los,são discutidos, a partir de um resgate histórico dos mesmos. Um modelo para consideração dos efeitos de tamanho e heterogeneidade, via método dos elementos finitos, que se baseia na aleatoriedade da ocorrência de fases sólidas no volume estrutural, bem como nas diferenças das respostas constitutivas associadas a diferentes tamanhos estruturais, é proposto. Através de exemplos, os aspectos do trabalho relacionados com o modelo constitutivo adotado, com os processos de obtenção de trajetórias de equilíbrio e com o modelo proposto para tratar a heterogeneidade e o efeito de tamanho, são discutidos. / [en] This study is a contribution to a better understanding of some aspects in the numerical modeling of the heterogeneity and size effects in the analysis of concrete structures. A general format of the smeared damage model is presented based on a historical perspective, since the first studies to the adoption of the inverse compliance relationship. This format includes diverse initial compliance relations, change in the direction of the damage approximations to the tangent tensor and different evolution damage laws for tension and compression.The limitations of the classical incremental-iterative methods for the solution of nonlinear physical problems are discussed. The secant and tangent formulations of these methods are shown as well as a review of the most commonly used controlling procedures. A new method is introduced in which the controlling parameter is based on the strain variation. Its secant and tangent formulations are also indicated.A historical review of the experimental and theoretical studies concerning the aspects of heterogeneity and size effects in concrete structures is done. A finite element model is then proposed which includes both the heterogeneity and size effects. It is based on the random occurrence of solid phases in the structural volume as well as on the differences of constitutive responses due to structural size.Examples problems are solved which illustrate the employed constitutive model, the procedures for the determination of the equilibrium paths and the model to heterogeneity and size effect.

[pt] Esta dissertação tem como objetivo propor modelos matemáticos e ferramentas computacionais de assessoria na tomada de decisão para o dimensionamento da frota ótima de veículos. O trabalho apresenta modelos que visam reduzir os custos de transporte para uma frota heterogênea de veículos composta por veículos próprios e terceirizados. Os modelos são baseados em problemas de Bin Packing, Roteirização de veículos e dimensionamento de frotas heterogêneas e foram moldados para atender as necessidades da empresa em estudo. Os resultados obtidos na aplicação de cada modelo foram comparados e as ferramentas computacionais utilizadas foram analisadas para identificar os pontos positivos e negativos. Este trabalho também propõe um modelo que compara a compra de novos veículos com a terceirização das entregas quando a frota própria não é suficiente para atender a demanda. / [en] This dissertation aims to propose mathematical models and computational tools to optimize the dimension of a heterogeneous vehicle fleet in his size and composition. This work shows models that intend to reduce transportation cost for a heterogeneous fleet compose by own and third vehicles. The models are based in problems such as BPP- Bin packing problem, VRP – Vehicle routing problem and linear programming. The problems have been molded to attend the necessities of the company in the study of case. The results achieved in the application of each model were compared and the computational tools had been analyzed to identify positive and negative points. This work also proposes a model that compares the purchase of new vehicles with the delivery by third company when the own fleet is not enough to attend the demand.

Ce travail porte sur le développement de méthodes d'homogénéisation numériques pour les matériaux non linéaires élastoplastiques et élasto-visco plastiques avec pour finalité le calcul de structures hétérogènes faite de ces matériaux sous chargements cycliques. Les techniques proposées se basent sur des approches incrémentales. Dans une première partie, nous développons une méthodologie pour déterminer la taille du VER dans le cas non linéaire pour les types de comportements cités précédemment. Pour cela, une étude de la convergence statistique de paramètres d'une loi semi-analytique incrémentale est menée. Cette méthode permet de diminuer les temps de calcul pour l'identification des paramètres et ainsi qu'une meilleure approximation de la loi de comportement effective, qui peut ensuite être utilisée dans un calcul de structure. Dans une deuxième partie, nous proposons une méthode d'homogénéisation numérique incrémentale dans laquelle l'originalité est de calculer le module tangent effectif par superposition de solutions numériques calculées par éléments finis sur le VER, en exploitant la linéarisation du problème à caque incrément. Un schéma alternatif aux techniques telles que la méthode Eléments finis multi niveaux (FE2) est ainsi développé, avec pour avantage un nombre réduit de calculs éléments finis à effectuer sur le VER. La technique est appliquée au calcul de structures hétérogènes non linéaires élastoplastiques, pour des microstructures anisotropes ou de morphologies complexes, et pour des lois de comportement locales élastoplastiques avec écrouissage isotrope et cinématique / In this work, computational homogenization methods for nonlinear materials with elasto-plastic and elasto-visco-plastic phases are developed, with application to the computation of heterogeneous structures made of these nonlinear materials under cyclic loading. The proposed techniques are based on incremental approaches. In a first part, we develop a methodology to determine the size of an RVE in the nonlinear case for the types of nonlinear behavior mentioned above. For this purpose, a convergence study of the parameters of a semi-analytical incremental constitutive law is carried out. This method allows reducing computational times related to the identification of these parameters and provides a better approximation of the effective constitutive relationship, which can then be used in a structure calculation once identified. In a second part, we propose an incremental computatioal homogenization method in which the originality is to compute directly the effective tangent tensor by superposition of numerical solutions computed by finite elements on an RVE, by taking advantage of the linearization of the problem at each increment. An alternative scheme to classical multilevel finite element techniques (FE2) is then developed, with the advantage of a reduced number of computations to perform on the RVE. The technique is applied to the computation of heterogeneous, nonlinear structures, for anisotropic microstructures or with complex morphologies and for phase with elastoplastic behavior with isotropic and kinematic hardening

L'objectif de la présente thèse et de développer un cadre d'étude et de simulation apte à prédire les propriétés effectives de diffusion dans les matériaux cimentaires saturés. Le principe suivi, fondé sur les approches multi-échelles séquencées, permettra de modéliser chaque échelle d'intérêt, depuis le gel des C-S-H, jusqu'au matériau béton, et ainsi via des simulations de prédire les coefficients de diffusion effectifs.Le cadre d'étude est donc fondé sur les points clés suivant :- Des morphologies de type "matrice - inclusion" sont générées via des excursions de champs aléatoires corrélés tri-dimensionnels. Cette approche, combinée avec quelques opérations morphologiques, permet la génération de morphologies inclusionnaires 3D suivant des distributions de tailles imposées. Il est ensuite possible de faire évoluer ces morphologies, depuis un état initial, en fonction d'un modèle prescrit (par exemple en termes de fraction volumiques), via le seuil de l'excursion.- Les cibles morphologiques de chaque échelle considérées tentent de refléter les résultats expérimentaux et modèles les plus communément admis. En supplément, à l'échelle de la pâte de ciment, un modèle "simple" d'hydratation est développé afin de prédire l'évolution de celle-ci dans le temps en termes de fractions volumiques. Le choix a été fait d'utiliser pour fondement un modèle simple (Jennings & Tennis), incorporant des paramètres essentiels, tels que la composition minéralogique du ciment ou le rapport e/c. Des modifications mineures ont été apporté au modèle, afin de prendre en compte de récents résultats expérimentaux, concernant principalement la fin de l'hydratation ainsi que sa cinétique.- Le cadre d'homogénéisation a été construit pour être utilisable à toutes les échelles considérées, et il permet ainsi de prédire les propriétés effectives de diffusion avec des considération énergétiques d'équivalence entre échelles. De façon analogue à la théorie de Hill pour l'élasticité, le cadre d'étude assure une séparation d'échelle cohérente vis-à-vis des propriétés effectives de diffusion.- Enfin, d'un point de vue numérique, les simulations utilisent les méthodes E-FEM, couplées à l'utilisation de maillages non-adaptés sur lesquels les morphologies sont "projetées". De cette façon, les discontinuités géométriques (discontinuité de propriétés matériaux) sont sont assurés par les élément finis enrichis, et ne requièrent pas d'éléments joint, ou de "moyennage" de propriétés.Les résultats de chaque échelle sont utilisés comme paramètres d'entrés pour les échelles suivantes. Depuis l'échelle des hydrates (C-S-H), jusqu'à l'échelle du béton, les coefficients de diffusion effectifs sont ainsi estimés. / The aim of the present Ph.D. is to develop a methodology and a simulation framework able to predict as accurately as possible effective properties regarding diffusion in saturated cement based materials. A sequenced multiscale framework is developed to perform numerical homogenization on diffusive properties, and thus predict effective properties. The general outline is to model every scale in concrete-like materials, from the C-S-H gel, to the concrete scale, and with the help of a proper framework, be able to predict effective properties. The methodology relies on the following key points for every considered scale :- Inclusion-matrix like morphologies are generated through level set methods applied to multi-dimensional correlated random fields. This approach, together with few morphological operations allows to generate 3D morphologies with given particle size distributions (PSD), or pore size distributions. Then, it is also possible, from the initial state, to make those morphologies evolve according to any descriptive model (e.g. in terms of volume fraction), via the level set.- The morphological description of each scale is chosen according to the most acknowledged experimentations and models. In addition, at the cement paste scale, a hydration model was developed to predict the evolution of the cement paste through time, in terms of volume fractions. The choice was made to keep a simple model (Jennings & Tennis), with few but essential input parameters (mineral cement composition, w/c ratio, PSD). It has only been modified to include recent experimental results, such as the maximal hydration degree, or the hydration rates.- The upscaling framework was built to suit every considered scale, and allows to assess effective properties based on energy conservation principles. Similar to Hill's theory for elasticity, the framework is build to ensure to proper scale separation regarding effective diffusion coefficients.- Lastely, the numerical context is based on E-FEM techniques, which allows to use unstructured meshes, on which the morphologies are projected. This way, any material discontinuity in dealt within the FE, and thus does not require averaging properties, or joint elements. Results from every scale will be used as inputs at the higher scales, and effective diffusion coefficients are thus estimated.

No description available.

The prediction of fracture is of utmost importance regarding the design of modern, specifically tailored engineering materials. These materials are often heterogeneous, \ie their properties vary in space. This can either be achieved purposefully by combining two or more constituents to profit from a more resilient composite material, or happen due to unavoidable imperfections. In any case, purely experimental assessment of failure is tedious and circuitous as soon as the structure of interest gets more complex, and the involvement of numerical models is inevitable. In this work, the phase-field approach to fracture is applied which is able to capture manifold crack phenomena inherently and sidesteps the need for remeshing by describing the crack as a continuous field. The phase-field model is extended to a fully diffuse incorporation of heterogeneities: A static order parameter smoothly transitions from one to the other bulk material constituent, while the weak, brittle interface is incorporated via a continuous fracture toughness distribution. The sharp interface jump conditions still hold for the diffuse representation since a partial rank-1 relaxation is employed in accordance with the unilateral contact condition of the phase-field model. Moreover, a compensation procedure ensures the independence of the interface fracture toughness from interface and phase-field length scales. The model is validated by a comparison to analytical results and the predictive power is demonstrated by the deduction of direction-dependent, effective fracture properties of heterogeneous microstructures. / Die Vorhersage des Bruchverhaltens ist für die Entwicklung moderner, speziell zugeschnittener technischer Werkstoffe von größter Bedeutung. Diese Materialien sind oft heterogen, d.h. ihre Eigenschaften variieren im Raum. Dies kann entweder absichtlich durch die Kombination zweier oder mehrerer Bestandteile erreicht werden, um von einem widerstandsfähigeren Verbundwerkstoff zu profitieren, oder durch unvermeidbare Imperfektionen geschehen. In jedem Fall ist eine rein experimentelle Versagensbewertung komplexer Strukturen mühsam und umständlich, und die Nutzung numerischer Modelle unvermeidlich. In dieser Arbeit werden Brüche mittels Phasenfeldmethode modelliert, wodurch vielfältige Rissphänomene erfasst werden können und die Notwendigkeit einer Neuvernetzung durch die Beschreibung des Risses als kontinuierliches Feld entfällt. Das Phasenfeldmodell wird um eine vollständig diffuse Einbindung von Heterogenitäten erweitert: Ein statischer Orderparameter beschreibt den glatten Übergang zwischen zwei Bestandteilen des Materials, während die geschwächte, spröde Grenzfläche durch eine kontinuierliche Bruchzähigkeitsverteilung eingebunden wird. Die scharfen Grenzflächensprungbedingungen gelten auch für die diffuse Darstellung, da eine partielle Rang-1 Relaxation in Übereinstimmung mit der unilateralen Rissflächenkontaktbedingung genutzt wird. Darüber hinaus gewährleistet ein Kompensationsverfahren die Unabhängigkeit der Grenzflächenbruchzähigkeit von inhärenten Längenskalen der Grenzfläche und des Rissphasenfelds. Das Modell wird durch einen Vergleich mit analytischen Ergebnissen validiert und die Vorhersagekraft wird durch die Ableitung richtungsabhängiger, effektiver Brucheigenschaften heterogener Mikrostrukturen demonstriert.

[pt] O compartilhamento de dados é um fator crítico para o sucesso das organizações devido à emergente necessidade de comunicação com seus parceiros de negócios. Porém, a heterogeneidade das fontes de dados é uma das barreiras para a efetiva interoperabilidade entre sistemas de informação. Esta dissertação inicialmente introduz o conceito de Catálogo de Objetos baseado em Ontologia (OnOC) como uma estratégia para endereçar o problema de interoperabilidade entre diferentes fontes de dados. Um OnOC oferece recursos para definir e manter um vocabulário comum, chamado ontologia de referência, que facilita o intercâmbio de dados entre diferentes fontes. Em seguida, propõe uma arquitetura para OnOCs que combina conceitos tais como catálogos de metadados, servidores de ontologias, mediadores e federações de bancos de dados. / [en] Data sharing is a critical factor for the success of organizations due to the increasing need to facilitate communication with business partners. However, data source heterogeneity proved to be a barrier for the effective interoperability between information systems. The concept of an Ontology- based Object Catalog (OnOC) is first introduced as a strategy to address the interoperability problem between heterogeneous data sources. An OnOC offers support for the definition and maintenance of a common vocabulary, called a reference ontology, that facilitates data interchange among different sources. Then, an architecture for OnOCs is proposed that combines concepts such as metadata catalogs, ontology servers, mediators and database federations.

Ce travail de thèse cherche à mieux caractériser le comportement des matériaux hétérogènes sous cisaillement avec une approche multi-échelles (macro-méso-microscopique).Cela est rendu possible en développant un montage innovant qui couple un rhéomètre à un système d’imagerie de speckle résolue spatialement et temporellement (RheoSpeckle). Nous montrons la validation de notre expérience en l’appliquant sur deux matériaux parfaits : un solide et un liquide. Sur le solide, on mesure le champ de déplacement sur les images de speckle avec une résolution meilleure que 1 µm. Puis on prouve l’élasticité du matériau à l’échelle microscopique. Sur le liquide, la taille des nanoparticules est déterminée avec un excellent accord avec la spécification du fabriquant. Le champ de vitesse dans l’entrefer du Couette est calculé avec une bonne précision sur un temps inférieur à 1 s et avec une résolution spatiale de 100 µm sur 5mm. La dynamique microscopique d’une solution brownienne est étudiée et l’influence du cisaillement sur la décorrélation est déterminée. Nous montrons les capacités de notre expérience à étudier des matériaux hétérogènes en l’appliquant sur une solution concentrée de micelles géantes. La rhéologie linéaire est étudiée en rhéometrie classique mais aussi en utilisant l’imagerie du speckle. La rhéologie non linéaire de ce matériau est déterminé en rhéometrie (macro) mais aussi en calculant le champ de vitesse et l’intensité des images de speckle (méso) ou on caractérise les bandes de cisaillement qui se forment à partir d’un cisaillement critique. En fin la relaxation spatio-temporelle des bandes de cisaillement (micro) est caractérisée. On observe pour la première fois l’existence de deux temps de relaxation après l’arrêt du cisaillement et que la relaxation des bandes est relativement lente. / This work tries to better characterize the behavior of homogeneous and heterogeneous materials under shear with a multi-scale approach (macro-meso-micro-scopic). To do that, we have developed an innovative setup by coupling a rheometer to a speckle imaging geometry witch is spatially and temporally resolved (RheoSpeckle). We validate our experience using two perfect materials: a solid and a pure viscous fluid. On a solid sample, we calculate the displacement field on the speckle images with a resolution better than 1 µm. we demonstrate than, the microscopic elasticity of this material. On a pure viscous fluid, we measured the nanoparticle’s size with excellent accuracy. When a constant shear rate is applied, the velocity profile is measured with a time less than 1 s with a spatial resolution of 100 µm over 5 mm. The microscopic dynamic of a Brownian solution under shear is probed and the shear induced on the decorrelation of the intensity correlation function is studied. We show the capabilities of our experience using a concentrated solution of wormlike micelles. The linear rheology is studied using rheometric measurements and our speckle imaging system. Nonlinear rheology is studied using rheometric measurements (macro), but also by calculating the velocity filed and the intensity of speckle images (meso). With mesocopics measurements, the formation of shear banding is proved and characterized. Finally, the spatio-temporal relaxation (micro) of shear bands of this material is studied. We show for the first time the existence of two relaxations times after shear and that the relaxation of bands is relatively slow.

Diversos materiais de interesse tecnológico podem ser considerados como materiais heterogêneos, onde sua natureza aleatória deve ser considerada para representar corretamente o comportamento não-linear. A avaliação quantitativa do dano em materiais sujeitos a estados de tensão ou deformação tem grande importância devido ao caráter crítico desse fenômeno, que pode crescer de forma abrupta e resultar em uma falha catastrófica da estrutura. Em estudos anteriores, Carpinteri e seus colaboradores apresentaram diferentes aspectos relacionados à caracterização do dano em materiais heterogêneos. Três desses aspectos são discutidos neste trabalho: (i) a proposta do número de fragilidade como medida da fragilidade da estrutura em análise; (ii) a evolução da dimensão fractal em que o processo de dano é desenvolvido; (iii) e os índices globais obtidos pela análise de Emissão Acústica (EA). Neste trabalho, uma versão do método dos elementos discretos formado por barras é utilizada para explorar esses aspectos. Espécimes de material quase-frágil são simulados e, quando possível, os resultados numéricos são comparados com resultados experimentais. Além disso, a discussão dos resultados obtidos é realizada visando compreender o comportamento desse tipo de material, como por exemplo, o fato de que estruturas com diferentes dimensões, porém com o mesmo número de fragilidade, têm comportamentos similares. Ademais, o método numérico empregado é apresentado como uma ferramenta viável para complementar a informação obtida em ensaios experimentais na avaliação do processo de dano. Pelo sinal de EA obtido através do método numérico empregado, obtiveram-se parâmetros para a classificação do tipo de falha e para o cálculo do tensor momento, onde comparando os resultados obtidos pelo modelo numérico e pela EA se observam comportamentos coerentes. / Several materials with technological interest can be considered as heterogeneous materials, where their random nature must be accounted to correctly represent the nonlinear behavior. The quantitative evaluation of damage in materials subjected to stress or strain states have great importance due to the critical nature of this phenomenon, which abruptly can rise to catastrophic failure. In previous studies, Carpinteri and his coworkers have presented different aspects of the damage process characterization in heterogeneous materials. Three of these aspects are discussed in this work: (i) the brittleness number proposal to measure the brittleness level of the analyzed structure, (ii) the relationship of the fractal dimension in which the damage process is developed, (iii) and the global indexes obtained by the Acoustic Emission (AE) analysis. In the present work, a version of discrete element method formed by bars is used to explore these concepts. A set of quasi-brittle material specimen is simulated and, when possible, the numerical results are compared with experimental ones. Moreover, a discussion of the obtained results is carried out aiming to understand the behavior of this kind of material, for instance, the fact that structures with different dimensions, but with the same brittleness number, have similar behavior. In addition, the numerical method is presented as a viable tool to complement information from experimental test on the damage process. From the AE signal obtained by the numerical method, parameters to classify the type of crack and for calculating the moment tensor were obtained, where consistent behaviors are observed by comparing the results of the numerical model and the AE.

[pt] A análise técnica ou grafismo consiste na identificação visual de padrões geométricos em gráficos de séries de preços de mercado com o objetivo de antecipar tendências de preço. Esta Dissertação revisita a questão da validação estatística da análise técnica, que tem sido estudada na literatura sem os devidos cuidados com os problemas de heterogeneidade e de dependência estatística dos dados analisados - agrupamento de séries de retornos referentes a diversos ativos financeiros distintos. O objetivo central deste estudo consiste em resolver o primeiro problema citado, através de uma metodologia para homogeneizar os ativos no que concerne às distribuições de probabilidades de suas séries de retorno. Os passos gerais desta metodologia envolvem a identificação dos processos estocásticos geradores dos retornos dos ativos, o agrupamento de ativos semelhantes e, finalmente, a análise de presença, ou ausência, de informação advinda dos padrões de preços. Como ilustração, são analisadas séries de diversos ativos do mercado financeiro mundial. A nossa investigação verifica a existência de conteúdo informativo estatisticamente significante em dois dos três padrões usualmente identificados na análise técnica, a saber: triângulos retângulos e head & shoulders. / [en] Technical analysis or charting aims on visually identifying geometrical patterns in price charts in order to anticipate price trends. This dissertation revisits the issue of technical analysis statistical validation, which has been tackled in the literature without taking care of the presence of heterogeneity and statistical dependence in the analyzed data - agglutinated return time series from many distinct securities. The main purpose of this study is to address the first cited problem by suggesting a methodology to homogenize the securities according to the probability distributions of their return series. The general steps of the methodology go through the identification of the data generating stochastic processes for the security returns, the clustering of similar securities and, finally, the analysis of the presence, or absence, of informational content coming from those price patterns. We illustrate the proposed methodology with several financial securities of the global market. Our investigation shows that there is a statistically significant informational content in two out of the three common patterns usually found through technical analysis, namely: triangles, rectangle and head & shoulders.