Les matériaux granulaires exhibe un spectre très large de propriétés constitutives, le long de chemins de chargement très divers. Développer des modèles constitutifs permettant de reproduire ces caractéristiques a demeuré un réel challenge scientifique au cours des dernières décennies. A cet égard, les approches multi-échelles constituent aujourd’hui une voie très prometteuse. Elles permettent de relier les propriétés macroscopiques à celles observées à l’échelle microscopique.Une investigation a été menée sur la base de simulations numériques discrètes (DEM)d’essais biaxiaux, afin d’identifier les caractéristiques micro-structurelles du matériau granulaire, la manière dont elles évoluent au cours d’un chemin de chargement, et le rôle qu’elles jouent dans l’émergence du comportement macroscopique. A l’échelle mésoscopique,le réseau de transmission de force (chaines de force) et les cellules définies parles vecteurs branches (meso-cycles) apparaissent jouer un rôle de première importance.Les meso-cycles, construits à partir du réseau de contact de l’assemblage, peuvent être caractérisés en fonction du nombre de cotés qu’ils contiennent (topologie). Leur influence sur le comportement volumique de l’échantillon est en effet étroitement liée à ce nombre de contact. En outre, leur interaction avec les chaines de force est également fortement dépendante de leur topologie. Ainsi, les cycles contenant 3 cotés (L3) participent activement à la stabilisation des chaines de force, alors que les cycles contenants au moins6 cotés (L6+) contribuent essentiellement au comportement dilatant de l’échantillon et à l’effondrement des chaines de force. Enfin, l’existence d’une méso-structure unique à l’état critique, au sein de la bande de cisaillement (rupture localisée) ou au sein de l’échantillon (rupture diffuse), est clairement démontrée.viii Sur la base de ces résultats, un modèle constitutif a été développé à partir du modèle H-directionnel (Nicot and Darve, 2011b). La structure du matériau granulaire est décrite par un assemblage d’hexagones (modélisant les cycles L6), orientés dans toutes les directions de l’espace. A partir d’opérations d’homogénéisation, les contraintes et les déformations incrémentales peuvent être reliées à l’échelle de l’assemblage, donnant lieu à un modèle de comportement dont la performance a pu être testée le long de chemins de chargements variés. / Granular materials exhibit a wide spectrum of constitutive features under various loading paths. Developing constitutive models which succeed to characterize these features has been challenging scientists for decades. A promising direction of achieving this can be the multi-scale approach. Through which the constitutive model is formulated in the way that relating material's macroscopic properties to their micro-scale essences, namely, corresponding micro-structure properties.To better characterize the micro-structure and formulate the relation between different scales, a comprehensive investigation have been carried out on the basis of numerical biaxial tests using 2D discrete element method (DEM), in order to ascertain the micro-structure characteristics of the granular material, the way they evolve versus loading and their corresponding rules in the macroscopic behaviors. In a meso-scale, intermediate between the single contact scale and the macro-scale, the force transmission network (force-chains) and area element enclosed by contacts branches (meso-loops) are highlighted in terms of their significant influences on material's macro-scale behavior. Meso-loops herein are tessellated from the whole area of the granular assembly by the contact branch network, and are subsequently categorized according to their side number.The development of meso-loops is observed to be intimately related to material's volumetric evolution, especially the plastic part. Then, the interaction between force-chains and meso-loops and its significance to the global volumetric behavior are revealed. Otherwise, in critical state, an identical meso-structure is found in the failure area of both localized and diffuse failure mode. Meso-loops with 3 sides (L3) appear to be indispensable for the force-chain stability, meanwhile, meso-loops with more than or equal to 6 sides (L6+) contribute much to the volume expansion and accelerate the force-chain buckling. The interplay between L3 and L6+ largely embody, or are representative of, the various mechanical performance of the granular material.A constitutive model has been developed by modifying the H-directional model. In this model, individual hexagons, representatives of L6+, construct the fabric as distributing along different directions in the space. Then multi-scale approach is then used to relate macroscopic properties from local ones, and eventually, to give the constitutive relation. This model is then validated in different loading paths, and eventually proved satisfying.

The African Union (AU) was established by the African Union Constitutive Act in 2000 to address the shortcomings of its predecessor the Organisation for African Unity (OAU). One of the main considerations for the establishment of the AU was the OAU’s strict adherence to the principle of non-intervention. The OAU was established on the principle of sovereignty and territorial integrity but the leaders of Africa realised that while the protection of sovereignty and territorial integrity was important ambitions for the African continent, it was just as important that African conflicts are resolved more effectively. While the AU Constitutive Act restates the commitment of the AU to the principles of sovereignty and territorial integrity, the AU Constitutive Act also provides for protection of human rights and, most significantly, for the limited intervention by the AU in grave circumstances. Article 4(h) of the AU Constitutive Act provides the “right of the Union to intervene in a Member State pursuant to a decision of the Assembly in respect of grave circumstances, namely war crimes, genocide and crimes against humanity”. The right to intervention contain in this article provide a great opportunity to improve the effectiveness of conflict management on the African continent. However, Articles 2(4) and 2(7) of the United Nations Charter pose a strong challenge to the legality of intervention under article 4(h) of the AU Constitutive Act. It is generally accepted that consent or invitation by the state concerned precluded any wrongfulness of the prima facie violation of international law and in particular a valid exception to the prohibition on the use of force. By signing the AU Constitutive Act the member states of the AU consented in advance to the possibility of intervention and consequently there is no conflict between the right to intervene and the prohibition of the use of force, as long as the AU remains within the bounds set out in the AU Constitutive Act and the succeeding mandate given by the Assembly. It might be argued that the prohibition on the use of force is a ius cogens norm that cannot be contracted out and that any agreement to this effect is void. However, the commentaries to Article 26 of the Articles on State Responsibility state that consent may be relevant when applying such a peremptory norm. Furthermore, only the prohibition on aggression is peremptory in nature. The definition of aggression states inter alia that aggression is the use of armed force on the territory of another in contravention of an agreement between the parties concerned. Thus, use of force undertaken in the territory of a state within the bounds of the agreement between the parties is not aggression and thus not a violation of a peremptory norm. The increased international focus on human rights and human security has influenced the way the notion of sovereignty and the principle of non-interference are understood. In 2001 the International Commission on Intervention and State Sovereignty’s report “The Responsibility to Protect” introduced the twin norms of sovereignty as a responsibility and the Responsibility to Protect. The notion of sovereignty as a responsibility implies that every state has the responsibility to protect its people from gross human rights abuses, while the Responsibility to Protect (R2P) refers to the responsibility of the international community to act should as state be unwilling or unable to fulfil its responsibilities towards its citizens. By incorporation of the right to intervention in its Constitutive Act, the AU has embraced the concept of Responsibility to Protect. While the international endorsement of this concept and the constant paralysis of the SC, especially in respect of Africa, adds considerable legitimacy to possible intervention by the AU in terms of article 4(h). / Dissertation (LLM)--University of Pretoria, 2013. / gm2014 / Public Law / Unrestricted

La thèse aborde le « trou noir de la genèse » dans l’étude des organisations, c’est-àdire comment une organisation en vient à exister pour la première fois. Elle montre comment la genèse s’accomplit à travers l’agencement de multiples composantes (humaines, symboliques, matérielles), articulées à travers les interactions. S’appuyant sur une analyse détaillée des interactions performées durant le congrès fondateur d’un parti politique au Québec tenu durant l’année 2006, elle identifie et discute les diverses stratégies et tactiques employés par les artisanes et artisans de cette fondation pour mettre en acte l’existence de ce nouvel agent collectif. Autrement dit, la thèse mène à une recension des manières de « communiquer la genèse ». Cela inclut l’usage de narratifs unificateurs, la gestion des identités, la mise en place de principes à travers des documents fondateurs, et la création d’une voix collective, à la fois partagée et négociée par les divers agents impliqués dans ce processus. Ces accomplissements mettent en lumière la dimension résolument rhétorique de l’organisation, conçus en tant que « stratégies pour rendre compte d’une situation », pour nommer sa structure et ses composantes primordiales à travers « l’usage du langage comme moyen symbolique d’induire la coopération ». La configuration rhétorique de discours, d’objets, de corps, de dispositifs spatiaux et physiques, et d’impératifs économiques, politiques et institutionnels à l’oeuvre dans les organisations procure un nouvel éclairage sur les modes d’existence de l’organisation. Par le fait de recenser les composantes « essentielles » ou « fondatrices » du parti politique investigué, et par l’analyse de celle-ci à l’aide des concepts de la théorie rhétorique du dramatisme, la thèse développe une perspective novatrice pour l’étude de la constitution communicative des organisations. / The dissertation addresses the “black hole of genesis” in organizational studies: how an organization gets constructed in the first place, and for the first time. It shows that an organization is founded through the interplay of various agencies (human, symbolic, material) articulated by communicative interactions. Based on the in-depth analysis of interactions performed during the founding convention of a political party in the Canadian province of Québec in 2006, it identifies and discusses the various strategies and tactics employed by members to enact the existence of a new collective agent, i.e., their ways of “communicating genesis.” Those include unification narratives, management of identities, institution of principles through founding documents, and the establishment of a collective voice, simultaneously shared and disputed by various agents. Such accomplishments are inherently rhetorical to the extent that they are “strategies for encompassing a situation,” for naming its structure and outstanding ingredients through “the use of language as a symbolic means of inducing cooperation.” This rhetorical configuration of discourses, objects, bodies, physical and spatial designs, economical, political, and institutional imperatives, that represents the heterogeneous agencies at work in organizations, bears new lights on what organizations come into being. By identifying the “foundational” or “essential” components of this political party, and by inscribing them in the concepts of the dramatist rhetorical theory, the dissertation develops an innovative perspective for the study of the communicative constitution of organizations.

CAR (Constitutive Androstane Receptor, NR1I3) et PXR (Pregnane X Receptor, NR1I2) sont deux récepteurs nucléaires dédiés à la reconna issance et à l'élimination de molécules lipophiles potentiellement toxiques pour l'organisme. Ces facteurs de transcription peuvent être activés par des ligands d'origines et de structures diverses (médicaments, polluants environnementaux, produits de l'alimentation et de phytothérapies). L'activation de ces récepteurs entraîne l'expression des gènes majeurs de la fonction de détoxication entéro-hépatique (CYP450, transférases, transporteurs) permettant l'élimination de ces toxiques. Dans ce travail, nous avons dans un premier temps 1) montré que CAR contrôle l'expression de Spot14, une protéine pro-lipogénique, et 2) nous avons identifié une nouvelle isoforme de PXR (PXR-small) codant uniquement pour le domaine de liaison des ligands de PXR. Nous avons pu déterminer les origines de transcription par 5'-RACE PCR et montrer que PXR-small représente environ 10% de l'ensemble des transcrits de PXR dans le tissu hépatique sain par une approche de PCR qua ntitative. Nous avons pu détecter sa présence par western-blot sur des extraits de protéines nucléaires issus de tissus hépatiques et de lignées cellulaires hépatiques. Par des expériences de gel retard, nous avons observé que cette nouvelle isoforme tronquée, qui ne code que pour le LBD de PXR, ne peut pas se lier à l'ADN. Des expériences de gènes rapporteurs suggèrent que cette isoforme se comporte comme un dominant négatif de PXR. Enfin, la présence d'un ilot CpG situé juste en amont de PXR-small suggère que cette nouvelle isoforme pourrait être régulée épigénétiquement par méthylation, notamment dans les cellules tumorales. / CAR (Constitutive Androstane Receptor, NR1I3) and PXR (Pregnane X Receptor, NR1I2) are two nuclear receptors devoted to the recognition and elimination of lipohilic molecules potentially toxic to the body.These transcription factors can be activated by ligands of different origins and structures (drugs, environmental pollutants, food products and herbal medicine...). The activation of these receptors leads to the expression of major genes of the detoxification process (CYP450, transferases, transporters) leading to the elimination of these toxics. In this work, we 1) showed that Spot14, a pro-lipogenic protein, is a target gene of CAR, then 2) we identified a novel isoform of PXR (PXR-small), coding only the ligand binding domain of PXR. By using 5'-RACE PXR, we established the origins of transcription of PXR-small and by quantitative PCR we observed that PXR-small represents about 10% of all PXR transcripts in human liver. By using western blo t, we detect its presence on nuclear protein extracts from liver tissues and hepatic cell lines. In Electromobility shift essays experiments, we observed that PXR-small cannot bind to DNA, while reporter essay experiments suggest that this isoform acts as a dominant negative of PXR. Finally, the presence of a CpG island just upstream of PXR-small suggests that this novel isoform might be regulated epigenetically by methylation, more particularly in tumor cells.

La thèse aborde le « trou noir de la genèse » dans l’étude des organisations, c’est-àdire comment une organisation en vient à exister pour la première fois. Elle montre comment la genèse s’accomplit à travers l’agencement de multiples composantes (humaines, symboliques, matérielles), articulées à travers les interactions. S’appuyant sur une analyse détaillée des interactions performées durant le congrès fondateur d’un parti politique au Québec tenu durant l’année 2006, elle identifie et discute les diverses stratégies et tactiques employés par les artisanes et artisans de cette fondation pour mettre en acte l’existence de ce nouvel agent collectif. Autrement dit, la thèse mène à une recension des manières de « communiquer la genèse ». Cela inclut l’usage de narratifs unificateurs, la gestion des identités, la mise en place de principes à travers des documents fondateurs, et la création d’une voix collective, à la fois partagée et négociée par les divers agents impliqués dans ce processus. Ces accomplissements mettent en lumière la dimension résolument rhétorique de l’organisation, conçus en tant que « stratégies pour rendre compte d’une situation », pour nommer sa structure et ses composantes primordiales à travers « l’usage du langage comme moyen symbolique d’induire la coopération ». La configuration rhétorique de discours, d’objets, de corps, de dispositifs spatiaux et physiques, et d’impératifs économiques, politiques et institutionnels à l’oeuvre dans les organisations procure un nouvel éclairage sur les modes d’existence de l’organisation. Par le fait de recenser les composantes « essentielles » ou « fondatrices » du parti politique investigué, et par l’analyse de celle-ci à l’aide des concepts de la théorie rhétorique du dramatisme, la thèse développe une perspective novatrice pour l’étude de la constitution communicative des organisations. / The dissertation addresses the “black hole of genesis” in organizational studies: how an organization gets constructed in the first place, and for the first time. It shows that an organization is founded through the interplay of various agencies (human, symbolic, material) articulated by communicative interactions. Based on the in-depth analysis of interactions performed during the founding convention of a political party in the Canadian province of Québec in 2006, it identifies and discusses the various strategies and tactics employed by members to enact the existence of a new collective agent, i.e., their ways of “communicating genesis.” Those include unification narratives, management of identities, institution of principles through founding documents, and the establishment of a collective voice, simultaneously shared and disputed by various agents. Such accomplishments are inherently rhetorical to the extent that they are “strategies for encompassing a situation,” for naming its structure and outstanding ingredients through “the use of language as a symbolic means of inducing cooperation.” This rhetorical configuration of discourses, objects, bodies, physical and spatial designs, economical, political, and institutional imperatives, that represents the heterogeneous agencies at work in organizations, bears new lights on what organizations come into being. By identifying the “foundational” or “essential” components of this political party, and by inscribing them in the concepts of the dramatist rhetorical theory, the dissertation develops an innovative perspective for the study of the communicative constitution of organizations.

Carregamentos cíclicos são causados de diversas maneiras, como tráfego de veículos, ondas, vento e terremotos. Nos últimos anos, particularmente, tem-se aumentado o número de estudos para este tipo de carregamento devido ao desenvolvimento da engenharia offshore. Além disso, técnicas de melhoramento de solos granulares têm sido empregadas para alterar as características dos solos naturais, com o objetivo de aumentar sua resistência e retardar - ou evitar - a ocorrência de liquefação. Alguns estudos anteriores desenvolveram leis constitutivas completas para areias reforçadas com fibras sob carregamento monotônico, mas não são encontrados na literatura trabalhos sobre a modelagem deste tipo de solos sob carregamentos cíclicos. Sendo assim, essa dissertação desenvolve e valida um novo modelo constitutivo capaz de avaliar o comportamento de solos granulares reforçados com fibras sob carregamento cíclico sob condições não-drenadas. Este modelo é baseado em dois modelos previamente desenvolvidos por Diambra et al. (2013) e Diambra e Ibraim (2014), que utilizam uma técnica de homogeneização para considerar a contribuição da areia e das fibras. O comportamento da areia segue o Modelo Severn-Trent Sand, proposto por Gajo e Muir Wood (1999). Uma vez estruturado o modelo e definido seu procedimento de cálculo, realiza-se uma análise paramétrica, a fim de demonstrar a influência de cada parâmetro das fibras e da areia no comportamento do compósito. Um fator de ajuste para levar em consideração a mudança nas forças interparticulares causada pelas fibras é proposto neste trabalho. Ao final, o modelo é calibrado com resultados experimentais e faz-se uma análise de suas competências e limitações. O processo de calibração mostrou que o modelo é capaz de capturar importantes tendências causadas pela inserção de fibras, como a redução nas deformações axiais e na geração de poropressões, retardando a ocorrência de liquefação. O modelo proposto mostrou-se mais efetivo em reproduzir o comportamento de areias fofas, ou seja, aquelas cujo estado de tensões se encontra acima da linha do estado crítico. / Cyclic loads are induced by several sources, such as traffic, waves, wind and earthquakes. Particularly in the last years, more attention has been given to such loading conditions due to the development of the offshore engineering. Additionally, ground improving techniques have been employed to alter the characteristics of natural soils in order to increase its strength and delay – or avoid – liquefaction. Previous studies have developed complete constitutive laws for fibre-reinforced sands under monotonic loading conditions, but no previous work on modelling granular soils under cyclic loading has been reported. Hence, this research develops and validates a new constitutive modelling which is capable to fully assess the behaviour of fibre-reinforced soils under cyclic loads for undrained conditions. This model is based on two previous models developed by Diambra et al. (2013) and Diambra and Ibraim (2014), which employed a homogenisation technique to scale sand and fibre contribution. The behaviour of the sand follows the Severn-Trent Sand Model proposed by Gajo and Muir Wood (1999). Once the model is structured and its calculation procedure is defined, a parametric analysis is carried out in order to show the influence of each fibre and sand parameter in the composite response. An adjustment factor to account for the change in the interparticle forces caused by the fibres is proposed. Finally, the model is calibrated with experimental results and an analysis of its competences and limitations is performed. The calibration process showed that the model is able to capture important trends caused by the fibre reinforcement, such as a reduction in axial strain and in pore pressure generation, delaying the occurrence of liquefaction. The proposed model was shown to be more effective in reproducing the response of loose sands, i.e. those whose stress states are above the critical state line.

The present thesis proposes model for the analyses of stress-strain response of fiber reinforced soil and municipal solid waste (MSW). The concept of reinforcing soils by introducing tension resisting elements such as fibers is becoming widely accepted. Fiber inclusions are found to improve the post-peak behavior of the soil. Evaluation of the stress-strain response of the fiber-reinforced soil indicates that mobilization of the fiber tension generally requires a strain level higher than that corresponding to the peak strength of unreinforced soil. Further, geotechnical engineering properties of MSW such as compressibility, shear strength and stiffness are of prime importance in design and maintenance of landfills. It is also referred in literature that MSW tends to behave as fiber-reinforced soil due to the presence of various types of wastes in its matrix. However, it is not well understood how the stress-strain and strength characteristics vary with time as the biodegradation of waste continues in the landfill. Based on the experimental observations, in this thesis, an attempt is made for developing generalized constitutive models based on the critical state soil mechanics frame work for fiber reinforced soils and municipal solid waste. The proposed models consider the fiber effect in fiber reinforced soil and, time dependent mechanical and biodegradation effects in case of municipal solid waste, respectively. The proposed models are able to capture the stress-strain and pore water pressure response in both the cases. For better understanding, the present thesis is divided into following seven chapters. Chapter 1 is an introductory chapter, in which the need for use of the constitutive models is presented. Further, the organization of thesis is also presented. Chapter 2 presents a brief description of the available studies in the literature on fiber-reinforced soils and municipal solid waste. Various studies on fiber-reinforced soil included experimental results (both laboratory and field) and modeling methods. Experiments on fiber-reinforced soils were mainly carried out with triaxial compression tests, unconfined compression tests, direct shear tests, one dimensional consolidation tests, etc. Force equilibrium model, limit equilibrium model, statistical theory, regression based models are some of the models available in the literature for quantifying the strength of the fiber-reinforced soil. Further, various studies with regard to the engineering properties of municipal solid waste and their characteristic properties available in the literature are presented. They include different models proposed by various researchers for the prediction of stress-strain response, time dependent behavior and load settlement analysis of the municipal solid waste. Finally, based on the literature review, the scope and objectives of the thesis are presented at the end. Chapter 3 describes various types of soils, properties of soils and fibers used in the present study. A detailed description of the sample preparation and methods adopted in the experimental program are presented in this chapter. Chapter 4 presents the experimental results of triaxial compression tests and one dimensional consolidation test carried out on fiber-reinforced soils. Based on the experimental observations, a constitutive model for fiber-reinforced soil in the frame work of modified cam clay model is proposed. Further, the detailed derivation of proposed model and the discussion on evaluation of the input model parameters from triaxial and consolidation tests are presented. The predictions from the proposed models are validated with the experimental data. From the comparison of the results from the proposed model and experiments, it is evident that the proposed model is able to capture stress-strain behavior of fiber-reinforced soils. Chapter 5 presents the experimental studies on the behavior of municipal solid waste based on the triaxial compression and consolidation tests. Based on the experimental observations, a constitutive model for municipal solid waste in the frame work of modified cam clay model is proposed which considers the mechanisms such as mechanical creep and biodegradation. It also provides detailed description of the selection of the input parameters required for the proposed model. The experimental results in the form of stress-strain and pore water pressure response are compared with the prediction from the proposed model. In addition, the applicability of the proposed model is illustrated using detailed parametric studies of parameters of the model for various ranges. Chapter 6 presents a brief study of load settlement response on municipal solid waste using a case example. The constitutive model for municipal solid waste proposed in chapter 5 is used to study the time-settlement response of municipal solid waste and to compare the results with available published models considering different mechanisms. The major conclusions from the study are presented at the end. Chapter 7 presents a brief summary and conclusions from the various studies reported in the present thesis. vi

Carregamentos cíclicos são causados de diversas maneiras, como tráfego de veículos, ondas, vento e terremotos. Nos últimos anos, particularmente, tem-se aumentado o número de estudos para este tipo de carregamento devido ao desenvolvimento da engenharia offshore. Além disso, técnicas de melhoramento de solos granulares têm sido empregadas para alterar as características dos solos naturais, com o objetivo de aumentar sua resistência e retardar - ou evitar - a ocorrência de liquefação. Alguns estudos anteriores desenvolveram leis constitutivas completas para areias reforçadas com fibras sob carregamento monotônico, mas não são encontrados na literatura trabalhos sobre a modelagem deste tipo de solos sob carregamentos cíclicos. Sendo assim, essa dissertação desenvolve e valida um novo modelo constitutivo capaz de avaliar o comportamento de solos granulares reforçados com fibras sob carregamento cíclico sob condições não-drenadas. Este modelo é baseado em dois modelos previamente desenvolvidos por Diambra et al. (2013) e Diambra e Ibraim (2014), que utilizam uma técnica de homogeneização para considerar a contribuição da areia e das fibras. O comportamento da areia segue o Modelo Severn-Trent Sand, proposto por Gajo e Muir Wood (1999). Uma vez estruturado o modelo e definido seu procedimento de cálculo, realiza-se uma análise paramétrica, a fim de demonstrar a influência de cada parâmetro das fibras e da areia no comportamento do compósito. Um fator de ajuste para levar em consideração a mudança nas forças interparticulares causada pelas fibras é proposto neste trabalho. Ao final, o modelo é calibrado com resultados experimentais e faz-se uma análise de suas competências e limitações. O processo de calibração mostrou que o modelo é capaz de capturar importantes tendências causadas pela inserção de fibras, como a redução nas deformações axiais e na geração de poropressões, retardando a ocorrência de liquefação. O modelo proposto mostrou-se mais efetivo em reproduzir o comportamento de areias fofas, ou seja, aquelas cujo estado de tensões se encontra acima da linha do estado crítico. / Cyclic loads are induced by several sources, such as traffic, waves, wind and earthquakes. Particularly in the last years, more attention has been given to such loading conditions due to the development of the offshore engineering. Additionally, ground improving techniques have been employed to alter the characteristics of natural soils in order to increase its strength and delay – or avoid – liquefaction. Previous studies have developed complete constitutive laws for fibre-reinforced sands under monotonic loading conditions, but no previous work on modelling granular soils under cyclic loading has been reported. Hence, this research develops and validates a new constitutive modelling which is capable to fully assess the behaviour of fibre-reinforced soils under cyclic loads for undrained conditions. This model is based on two previous models developed by Diambra et al. (2013) and Diambra and Ibraim (2014), which employed a homogenisation technique to scale sand and fibre contribution. The behaviour of the sand follows the Severn-Trent Sand Model proposed by Gajo and Muir Wood (1999). Once the model is structured and its calculation procedure is defined, a parametric analysis is carried out in order to show the influence of each fibre and sand parameter in the composite response. An adjustment factor to account for the change in the interparticle forces caused by the fibres is proposed. Finally, the model is calibrated with experimental results and an analysis of its competences and limitations is performed. The calibration process showed that the model is able to capture important trends caused by the fibre reinforcement, such as a reduction in axial strain and in pore pressure generation, delaying the occurrence of liquefaction. The proposed model was shown to be more effective in reproducing the response of loose sands, i.e. those whose stress states are above the critical state line.

The present study in this thesis has attempted to resolve one of the key aspects of enhancing predictability of macroscopic behavior of Shape Memory Alloy (SMA) wire by considering variation of local phase inhomogeneity. Understanding of functional fatigue and its relation with the phase distribution and its passivation is the key towards tailoring thermal Shape Memory Alloy actuators’ properties and performance. Present work has been carried out in two associated areas. First part has covered solving a coupled thermo-mechanical boundary value problem where initial phase fractions are prescribed at the gauss points and subsequent evolution are tracked over the loading cycle. An incremental form of a phenomenological constitutive model has been incorporated in the modelling framework. Finite element convergence studies using both homogeneous and inhomogeneous SMA wires are performed. Effects of phase inhomogeneity are investigated for mechanical loading and thermo-electric loading. Phase inhomogeneity is simulated mainly due to process and handling quality. An example of mechanical boundary condition such as gripping indicates a negative residual strain at macroscopic behavior. Simulation accurately captures vanishing local phase inhomogeneity upon multiple cycles of thermo-mechanical loading on unconstrained straight SMA wire. In the second part, a phase identification and measurement scheme is proposed. It has been shown that by employing variation of electrical resistivity which distinctly varies with phase transformation, martensite phase volume fraction can be quantified in average sense over the length of a SMA wire. This can be easily achieved by using a simple thermo-mechanical characterization setup along with resistance measurement circuit. Local phase inhomogeneity is created in an experimental sample, which is subjected to electrical heating under constant mechanical bias load. The response shows relaxation of the initial shrinkage strain due to local phase. Results observed for thermo-electric loading on the inhomogeneous SMA wires compliment the results observed from the simulated loading cases. Several interesting features such as shrinkage of the inhomogeneous SMA wire after first loading cycle, relaxation of the residual strain over multiple loading cycles due to the presence of inhomogeneity are captured. This model promises useful applications of SMA wire in fatigue studies, SMA embedded composites and hybrid structures.

Carregamentos cíclicos são causados de diversas maneiras, como tráfego de veículos, ondas, vento e terremotos. Nos últimos anos, particularmente, tem-se aumentado o número de estudos para este tipo de carregamento devido ao desenvolvimento da engenharia offshore. Além disso, técnicas de melhoramento de solos granulares têm sido empregadas para alterar as características dos solos naturais, com o objetivo de aumentar sua resistência e retardar - ou evitar - a ocorrência de liquefação. Alguns estudos anteriores desenvolveram leis constitutivas completas para areias reforçadas com fibras sob carregamento monotônico, mas não são encontrados na literatura trabalhos sobre a modelagem deste tipo de solos sob carregamentos cíclicos. Sendo assim, essa dissertação desenvolve e valida um novo modelo constitutivo capaz de avaliar o comportamento de solos granulares reforçados com fibras sob carregamento cíclico sob condições não-drenadas. Este modelo é baseado em dois modelos previamente desenvolvidos por Diambra et al. (2013) e Diambra e Ibraim (2014), que utilizam uma técnica de homogeneização para considerar a contribuição da areia e das fibras. O comportamento da areia segue o Modelo Severn-Trent Sand, proposto por Gajo e Muir Wood (1999). Uma vez estruturado o modelo e definido seu procedimento de cálculo, realiza-se uma análise paramétrica, a fim de demonstrar a influência de cada parâmetro das fibras e da areia no comportamento do compósito. Um fator de ajuste para levar em consideração a mudança nas forças interparticulares causada pelas fibras é proposto neste trabalho. Ao final, o modelo é calibrado com resultados experimentais e faz-se uma análise de suas competências e limitações. O processo de calibração mostrou que o modelo é capaz de capturar importantes tendências causadas pela inserção de fibras, como a redução nas deformações axiais e na geração de poropressões, retardando a ocorrência de liquefação. O modelo proposto mostrou-se mais efetivo em reproduzir o comportamento de areias fofas, ou seja, aquelas cujo estado de tensões se encontra acima da linha do estado crítico. / Cyclic loads are induced by several sources, such as traffic, waves, wind and earthquakes. Particularly in the last years, more attention has been given to such loading conditions due to the development of the offshore engineering. Additionally, ground improving techniques have been employed to alter the characteristics of natural soils in order to increase its strength and delay – or avoid – liquefaction. Previous studies have developed complete constitutive laws for fibre-reinforced sands under monotonic loading conditions, but no previous work on modelling granular soils under cyclic loading has been reported. Hence, this research develops and validates a new constitutive modelling which is capable to fully assess the behaviour of fibre-reinforced soils under cyclic loads for undrained conditions. This model is based on two previous models developed by Diambra et al. (2013) and Diambra and Ibraim (2014), which employed a homogenisation technique to scale sand and fibre contribution. The behaviour of the sand follows the Severn-Trent Sand Model proposed by Gajo and Muir Wood (1999). Once the model is structured and its calculation procedure is defined, a parametric analysis is carried out in order to show the influence of each fibre and sand parameter in the composite response. An adjustment factor to account for the change in the interparticle forces caused by the fibres is proposed. Finally, the model is calibrated with experimental results and an analysis of its competences and limitations is performed. The calibration process showed that the model is able to capture important trends caused by the fibre reinforcement, such as a reduction in axial strain and in pore pressure generation, delaying the occurrence of liquefaction. The proposed model was shown to be more effective in reproducing the response of loose sands, i.e. those whose stress states are above the critical state line.