The research carried out in this thesis has concentrated on the application of numerical solutions to geotechnical penetration problems in offshore engineering. Several important issues closely relevant to deep-water oil and gas developments were investigated, covering installation of suction caisson foundations, interpretation of fullflow penetrometers and shallow penetration of a cylindrical object (submarine pipeline or T-bar), all in clayey sediments such as are often encountered in deep-water sites. These problems are commonly characterised by large vertical movements of structural elements relative to the seabed. A large deformation finite element method was adopted and further developed to simulate these challenging problems, referred to as Remeshing and Interpolation Technique with Small Strain. In this approach, a sequence of small strain Lagrangian increments, remeshing and interpolation of stresses and material properties are repeated until the required displacement has been reached. This technique is able to model relative motion between the penetrating objects and the soil, which is critical for evaluating soil heave inside the caissons, the effect of penetration-induced remoulding on the resistance of full-flow penetrometers, and influence of soil surface heave on the embedment of pipelines. '...' Simple expressions were presented allowing the resistance factors for the T-bar and ball penetrometers to be expressed as a function of the rate and strain-softening parameters. By considering average strength conditions during penetration and extraction of these full-flow penetrometers, an approximate expression was derived that allowed estimation of the hypothetical resistance factor with no strain-softening, and hence an initial estimate of the stain-rate dependency of the soil. Further simulations of cyclic penetration tests showed that a cyclic range of three diameters of the penetrometers was sufficient to avoid overlap of the failure mechanism at the extremes and mid-point of the cyclic range. The ball had higher resistance factors compared with the T-bar, but with similar cyclic resistance degradation curves, which could be fitted accurately by simple expressions consistent with the strain-softening soil model adopted. Based on the curve fitting, more accurate equations were proposed to deduce the resistance factor with no strain-softening, compared with that suggested previously based on the resistances measured in the first cycle of penetration and extraction. The strain-rate dependency was similar in intact or post-cyclic soil for a given rate parameter. The resistance factor for the post-cyclic condition was higher than that for the initial conditions, to some degree depending upon soil sensitivity and brittleness parameter. For the shallow penetration of a cylindrical object, the penetration resistance profile observed from centrifuge model tests was very well captured by the numerical simulation. The mechanism of shear band shedding was reproduced by the numerical technique, although the frequency of the shear band generation and the exact shape of the heave profile were not correctly captured, which were limited by the simple strainsoftening soil model adopted.

Caisson or pier foundations are encountered as part of the foundation system of tall structures such as bridges, transmission towers, heliostats, etc, and correspond to rigid blocks of length-to-diameter (D/B) ratio on the order of D/B = 2-6. As a result of their geometry and stiffness characteristics, the mechanisms of load transfer from the superstructure to the surrounding soil and their kinematic response to seismic wave propagation are governed by a complex stress distribution at the pier-soil interface, which cannot be adequately represented by means of simplified Winkler models for shallow foundations or flexible piles. Continuum model solutions, such as 3D finite elements (FE) cannot be employed frequently in practice for the design of non-critical facilities due to the cost and effort associated with these analyses. The objective of this work is to develop a Winkler-type model for the analysis of transversely-loaded caissons, which approximately accounts for all the main soil resistance mechanisms mobilized, while retaining the advantages of simplified methodologies for design at intermediate levels of target accuracy. Investigation of the governing load-transfer mechanisms and development of complex spring functions is formulated on the basis of 3D FE simulations. Initially, the soil-structure stiffness matrix is computed by subjecting the pier to transverse static and dynamic loading at the top, and numerically estimating the response. Complex frequency-dependent functions are next developed for the spring constants by equating the stiffness matrix terms to the analytical expressions developed for the four-spring model. Sensitivity analyses are conducted for optimization of the truncated numerical domain size, finite element size and far-field dynamic boundary conditions to avoid spurious wave reflections. Simulations are next conducted to evaluate the transient response of the foundation subjected to vertically propagating shear waves, and results are compared to the response predicted by means of the 4-spring model. Finally, the applicability of the method is assessed for soil profiles with depth-varying properties. While the methodology developed is applicable for linear elastic media with no material damping, the expressions of complex spring functions may be extended to include hysteretic damping, nonlinear soil behavior and soil-foundation interface separation, as shown in the conclusions.

Ces dix dernières années, la miniaturisation des transistors MOS en technologie planaire sur silicium massif connait une augmentation considérable des effets parasites liés à la réduction de la longueur du canal. Ces effets canaux courts ont pour conséquence de dégrader les performances des transistors, rendant les circuits moins efficaces énergétiquement et plus sensibles aux phénomènes de fluctuations des procédés de fabrication. Ainsi, cette technologie fait face à une vraie barrière pour les noeuds inférieurs à 32nm.Pour répondre aux besoins des dispositifs mobiles alliant hautes performances et basse consommation, la technologie planaire sur isolant complètement désertée (FD-SOI pour Fully depleted Silicon-On-Insulator) apparaît comme une solution adaptée. En effet, grâce à son film de silicium mince et non dopé, le transistor MOS dispose d’un meilleur contrôle électrostatique du canal et d’une faible variabilité de sa tension de seuil. De plus, cette technologie offre la possibilité de moduler la tension de seuil des transistors grâce à une polarisation étendue à ±3V des caissons situés sous la fine couche d’oxyde enterré. Ainsi, cette spécificité apporte aux concepteurs de circuits intégrés un levier supplémentaire permettant de moduler les performances d’un circuit ainsi que d’en optimiser son efficacité énergétique.Le travail de recherche de thèse présenté dans ce mémoire a contribué au développement de la plateforme technologique FD-SOI pour les noeuds 28 puis 14nm. Dans un premier temps, l’exploitation d’un chemin critique extrait d’un coeur de processeur ARM Cortex-A9 a permis d’évaluer à la fois les gains intrinsèques apportés par la technologie FD-SOI ainsi que ceux produits par la modulation de la tension de seuil des transistors par polarisation du substrat. Cette technique permet ainsi de diviser jusqu’à 50 fois le courant statique d’un circuit lorsqu’il est inactif, ou encore par 2 l’énergie totale nécessaire à fréquence constante. Ces nombreuses analyses ont permis, dans un second temps, de proposer plusieurs solutions de conception visant une nouvelle fois à optimiser l’efficacité énergétique des circuits intégrés. Parmi celles-ci, la conception d’une structure à caisson unique permet notamment de résoudre les difficultés de co-intégration multi-VT classique, présentes en FD-SOI. Cette approche offre également aux concepteurs une solution performante pour les circuits fonctionnant avec une très large gamme de tensions d’alimentation. En effet, à l’aide d’une seule tension de substrat, les transistors n et p-MOS peuvent être simultanément rééquilibrés permettant ainsi de réduire fortement la tension minimale d’alimentation du circuit. / Over the last ten years, the scaling of MOSFETs in bulk planar technology is experiencing a significant increase in parasitic phenomenon driven by the reduction of the transistor channel length. These short-channel effects lead to the degradation of transistor performances, making circuits less energy efficient and more sensitive to the manufacturing process fluctuations. Therefore, this technology faces a real barrier for nodes beyond 32nm.To meet the needs of mobile devices, combining high performances and low power consumption, the planar fully depleted silicon-on-insulator (FD-SOI) technology appears to be a suitable solution. Indeed, thanks to its thin-film of silicon and an undoped channel, MOS transistors have an excellent short-channel electrostatic control and a low variability of the threshold voltage given by an immunity to random dopant fluctuation. In addition, this compelling technology enables to adjust the threshold voltage of transistors by applying a wide ±3V back-bias voltage on Wells. Thus, this specific FD-SOI feature brings to IC designers an additional lever to modulate the performance and to optimize the energy efficiency of circuits.The research work presented in this thesis has contributed to the development of FD-SOI technology platform for the 28 and 14nm nodes. Initially, a critical path extracted from an ARM Cortex-A9 processor was used to assess both the intrinsic gains provided by the FD-SOI technology and those produced by modulating the back-bias voltages. This technique enables to divide by up to 50 times the static current of circuits in standby mode, or by 2 the total energy consumption at same frequency. In the second phase, several design solutions are proposed in order to optimize the energy efficiency of circuits again. Among these, the design of a single-Well structure enables to solve the conventional multi-VT co-integration issue, occurring in FD-SOI. Moreover, this novel approach also offers an efficient solution for integrated circuits operating over a wide supply voltage range. Indeed, thanks to a single back-bias voltage, both n and p-MOS transistors could be easily balanced enabling an outstanding minimal supply voltage.

De nombreuses applications comme les cartes bancaires manipulent des données confidentielles. A ce titre, les circuits microélectroniques qui les composent, font de plus en plus l'objet d'attaques représentant des menaces pour la sécurité. De plus, un grand nombre des circuits électroniques portables et fonctionnant sur batterie demandent que la consommation électrique soit toujours plus réduite. Les concepteurs de circuit doivent donc proposer des solutions sécurisées, tout en limitant la consommation.Ce travail présente l'évaluation sécuritaire et la conception de contre-mesures pour des architectures à triple-caisson dédiées à la réduction de la consommation. Ces recherches, liées au contexte, se sont focalisées sur l'évaluation de cette architecture face à des injections de fautes Laser. Dès le début de ce manuscrit, l’état de l’art de l’injection de fautes est développé, en se focalisant sur les effets physiques d’un faisceau laser. Les architectures à double et triple-caisson sont ensuite analysées dans le but de comparer leur robustesse. Cette démarche permet d’appréhender d’éventuels effets physiques induits par le laser à l’intérieur des caissons de polarisations Nwell, Pwell et des transistors MOS. Suite à cette analyse des phénomènes physiques, des modélisations électriques des portes CMOS ont été développées pour des architectures à double et triple-caisson. De bonnes corrélations ont pu être obtenues entre les mesures et les simulations électriques. Pour conclure, ce travail a permis d'extraire de potentielles règles de conception permettant d’améliorer la robustesse sécuritaire des portes CMOS et de développer des moyens de détections d’attaques lasers. / In many applications such as credit cards, confidential data is used. In this regard, the systems-on-chip used in these applications are often deliberately attacked. This puts the security of our data at a high risk. Furthermore, many SoC devices have become battery-powered and require very low power consumption. In this context, semiconductor manufacturers should propose secured and low-power solutions.This thesis presents a security evaluation and a countermeasures design for a low-power, triple-well architecture dedicated to low-power applications. The security context of this research focuses on a Laser sensitivity evaluation of this architecture.This paper first presents the state of the art of Laser fault injection techniques, focusing on the physical effects induced by a Laser beam. Afterward, we discuss the different dual-and triple-well architectures studied in order to compare their security robustness. Then, a physical study of these architectures as substrate resistor and capacitor modeling highlights their impact on security. This evaluation lets us anticipate the phenomena potentially induced by the Laser inside the biasing well (P-well, N-well) and the MOS transistors.Following the analysis of the physical phenomena resulting from the interaction between the laser and the silicon, electrical modeling of the CMOS gates was developed for dual and triple-well architectures. This enabled us to obtain a good correlation between measurements and electrical simulations.In conclusion, this work enabled us to determine possible design rules for increasing the security robustness of CMOS gates as well as the development of Laser sensors able to detect an attack.

Presented diploma thesis deals with parametric optimization of wing caisson of L 410 NG aircraft to reduce its‘structure weight. The paper is mainly focused on description and application of optimization methods with the use of finite element methods in MSC Nastran. Moreover the thesis contains loading state check of optimized design, done in STAUNO software.

Lors du tsunami de Tohoku en 2011, des relevés de terrain sur les côtes japonaises ont montré la fragilité des structures côtières, où le plus grand brise-lames du monde (brise-lames de Kamaishi) a été fortement endommagé dû à cet événement. Dans ce doctorat, l'objectif est d'étudier l'interaction entre les brise-lames , les structures côtières les plus communes protégeant les zones urbaines et les entrées des ports, et les vagues, en particulier les tsunamis.Dans la première partie de ce travail, la transformation du tsunami en bore ondulaire dans les zones côtières est étudiée numériquement avec le code de calcul BOSZ (modèle Boussinesq). Les résultats montrent que la deuxième vague générée par le tsunami de Tohoku s'est transformée en un bore ondulaire. En revanche, la première vague n'était pas assez cambrée pour permettre une telle transformation. Les forces et les moments dus aux vagues ainsi que la contrainte normale appliquée par la base arrière du caisson sur le sol de fondation sont calculés à l'aide de deux modèles numériques différents: BOSZ et THETIS (modèle Navier-Stokes). Les résultats de BOSZ sont comparés avec THETIS pour l'interaction tsunami-structure. L'étude d'impact est réalisée à relativement grande échelle dans le but d'obtenir une première estimation des efforts d'un tsunamiPar la suite, une expérience numérique utilisant le modèle THETIS a été réalisée pour étudier les impacts du type flip-through sur des brise-lames. Ces impacts de vagues sans air emprisonné sont considérés comme le type d'impact le plus extrême dans la littérature (e.g. Cooker & Peregrine (1992), Hofland et al. (2011)). L'influence de l'inclinaison de l'interface sur la dynamique d'impact et les pressions générées sont analysées dans une configuration de brise-lames réelle. Le modèle d'onde solitaire est utilisé pour générer trois impacts caractéristiques du type flip-through: peu cambré, moyen et très cambré. Le champ de vitesses et la pression à l'intérieur de la fondation sont également étudiés dans cette partie. Les forces horizontales et verticales appliquées sur le caisson sont estimées en intégrant les distributions de pression données par THETIS.La dernière partie de ces travaux montre la stabilité des caissons de brise-lames soumis à des impacts du type flip-through, qui sont ici assimilés à un jet triangulaire (e.g. Cumberbatch (1960), Kihara et al. (2015)). Cette approche simple permet de formuler un modèle semi-analytique pour prédire le mouvement des caissons dû à ce type d'impacts. Après validation avec des simulations numériques, la méthode du jet triangulaire permet d'obtenir des informations sur les forces, la durée du mouvement et le déplacement total en fonction des caractéristiques de la vague et des dimensions du caisson du brise-lames impacté. / During the Tohoku tsunami in 2011, field surveys of the east coast of Japan showed the weakness of coastal defences, as even the world largest tsunami breakwater (Kamaishi) almost completely collapsed due to this event. In this PhD, the aim is to investigate the interaction between breakwaters, the most common offshore coastal structures protecting urban areas and harbour entries, and waves and especially tsunami waves.In the first part of the work, the generation of undular bores in the near-shore area of Sendai during the Tohoku event is numerically investigated with the numerical model BOSZ (Boussinesq-type model). It is shown that the second wave, which stroke the coast during this event, transformed into an undular bore, whereas the first wave did not due to steepness differences. Tsunami loads, moments and bearing stress applied on the offshore breakwater of the Soma Port are calculated using two models: BOSZ and THETIS (Navier-Stokes VOF model). BOSZ results are compared to THETIS for the tsunami wave-breakwater interaction. The impact study is carried out at a relatively large scale aiming to have a first estimation of tsunami efforts. Then, a numerical experiment using THETIS is carried out to investigate flip-through impacts on vertical breakwaters. This non-aerated wave impact is considered as the most severe type of impact in the literature (e.g. Cooker & Peregrine (1992), Hofland et al. (2011)) in terms of maximum pressure generated. The influence of the front interface on the impact dynamics and the pressure induced is analysed in a realistic breakwater configuration. Solitary waves are used to obtain three characteristic flip-through impacts involving least steep, medium steep and steepest wave front. The flow field and pressure inside the porous rubble mound are then investigated as well as horizontal and uplift forces applied on the breakwater caisson. The last part of this study is devoted to the stability of breakwater caissons submitted to flip-through impacts. The latter are here assimilated to water wedges (e.g. Cumberbatch (1960), Kihara et al. (2015)). This simple approach allows to formulate a semi-analytical model to predict caisson motion due to this type of impacts. After validation with numerical results, the water wedge method gives rich informations about forces, motion duration and sliding distance depending on the wave impact characteristics and breakwater caisson dimensions.

L’alliage d’aluminium 6061-T6 a été choisi comme matériau de structure du casier et du caisson du cœur de réacteur Jules Horowitz (RJH). Transparent aux neutrons, il doit ses bonnes propriétés mécaniques à la précipitation de fines aiguilles nanométriques appelées béta'' contenant Mg et Si et à la présence de dispersoïdes Al(Cr,Fe,Mn)Si jouant un rôle important dans la résistance à la recristallisation. Le caisson et le casier seront soumis à de forts flux neutroniques à une température avoisinant les 50°C. L’objectif de cette thèse est d’étudier les évolutions microstructurales de l’alliage sous irradiation et plus particulièrement la stabilité des précipités. Pour cela, des études analytiques par irradiations in-situ et ex-situ aux électrons et aux ions à température ambiante et forte dose ont été réalisées ainsi qu’une étude du comportement des précipités sous irradiations aux neutrons à faible dose. La caractérisation fine des précipités par Microscopie Electronique en Transmission a montré que les dispersoïdes sont stables sous irradiation, cependant ils présentent une structure cœur/coquille avec un cœur riche en (Fe, Mn) et une coquille riche en Cr qui s’accentue sous irradiation par accélération de la diffusion. En revanche, les nano-phases type béta’’ sont déstabilisées par l’irradiation. Elles sont dissoutes par irradiation aux ions au profit de l’apparition d’amas riches en Mg, Si, Al, Cu et Cr participant à l’augmentation du durcissement de l’alliage, tandis qu’elles tendent à se transformer en précipités cubiques sous irradiation aux neutrons. / The 6061-T6 Aluminium alloy, whose microstructure contains Al(Fe,Mn,Cr)Si dispersoids and hardening needle-shaped beta” precipitates (Mg, Si), has been chosen as the structural material for the core vessel of the Material Testing Jules Horowitz Nuclear Reactor. Because it will be submitted to high neutron fluxes at a temperature around 50°C, it is necessary to study microstructural evolutions induced by irradiation and especially the stability of the second phase particles. In this work, analytical studies by in-situ and ex-situ electron and ion irradiations have been performed, as well as a study under neutron irradiation. The precipitates characterization by Transmission Electron Microscopy demonstrates that Al(Fe,Mn,Cr)Si dispersoids are driven under irradiation towards their equilibrium configuration, consisting of a core/shell structure, enhanced by irradiation, with a (Fe, Mn) enriched core surrounded by a Cr-enriched shell. In contrast, the (Mg,Si) beta” precipitates are destabilized by irradiation. They dissolve under ion irradiation in favor of a new precipitation of (Mg,Si,Cu,Cr,Al) rich clusters resulting in an increase of the alloy’s hardness. beta’’ precipitates tend towards a transformation to cubic precipitates under neutron irradiation.

Capacity analysis is a common preliminary step in the design of offshore foundations. Inaccuracies in traditional capacity analysis methods, and the advancement of numerical modelling capabilities, have increasingly led designers to optimise foundations using more complex methods. In this thesis, the ultimate limit state capacity of a range of foundation types is investigated using finite element limit analysis. Novel three-dimensional finite element limit analysis software is benchmarked against analytical solutions and conventional displacement finite element analysis. It is then used to find lower and upper bounds of foundation capacity, with adaptive mesh refinement used to reduce the bound gap over successive iterations of the solution. Rigid foundations subjected to short term loading on clay soil are analysed. The undrained soil is modelled as a rigid--plastic von Mises material, and attention is given to modelling any normal and/or shear stress limits at the foundation/soil interface. Shallow foundations, suction anchor foundations, and hybrid mudmat/pile foundations are considered. Realistic six degree-of-freedom load combinations are applied and results are reported in the form of normalised design charts, and tables, that are suitable for use in preliminary design. Relationships between loading combinations and failure mechanisms are also explored. A number of case studies based on authentic foundation designs are analysed. The results suggest that finite element limit analysis could provide an attractive alternative to displacement finite element analysis for preliminary foundation design calculations.