n recent years, there has been a surge in interest and research into the utilisation of soft actuators within the field of robotics, driven by the novel capabilities of their inherently compliant material. One such actuator is the Pneumatic Artificial Muscle (PAM) which offers a high power-to-mass ratio, compliance, safety, and biological mimicry when compared to their traditional counterparts. However, because of their flexible and complex physical structure and the compressibility of air inside the PAM, they exhibit nonlinear dynamic behaviour, largely due to the influence of the hysteresis phenomenon. In order to implement strategies to counteract this effect, it first needs to be modelled. As such, this thesis investigates two approaches, namely the Maxwell-Slip (MS) and generalised Bouc-Wen (BW) models. Firstly, the test muscle's initial braid angle, maximum displacement, and maximum force are determined to establish the static force using a modified model. Data is then collected on the PAM's force-displacement hysteresis for 2-6 bar of pressure. Using the results from these experiments, the MS and BW model parameters are identified through optimisation. With the static and hysteresis force components characterised, two complete dynamic models are created. The findings show that, when compared to the collected force-displacement data, the BW model has greater accuracy for all pressures except at 4 bar, although both approaches demonstrate results within a satisfactory margin. Lastly, a model validation is conducted to compare the models using a new dataset, separate from the one on which they were trained. Data for this test is recorded at a pressure of 4 bar with a more complex reference that covers four different regions of the muscle's displacement range. Thereafter, both dynamic models are applied to assess their performance. It is evident from the results that the BW model produces a better outcome than the MS, achieving a normalised error of 5.3746% as compared to the latter's 12.835%. The higher accuracy of the generalised BoucWen method is likely due to it having a more complex structure, specialised parameters, and the ability to model asymmetric hysteresis. The Maxwell-Slip model may however still be preferable in some applications due to its relative simplicity and faster optimisation. / Under de senaste åren har intresset och forskningen ökat kring användningen av mjuka ställdon inom robotik, drivet av den innovativa potentialen som erbjuds av egenskaperna hos deras naturligt flexibla material. Ett sådant ställdon är den Pneumatiska Artificiella Muskeln (PAM) som erbjuder hög kraft i förhållande till vikten, elasticitet, säkerhet och biologisk imitation jämfört med dess traditionella motsvarigheter. Trots dessa fördelar så uppvisar PAM:s ett icke-önskvärt olinjärt dynamiskt beteende, till stor del på grund av deras flexibla och komplexa fysiska struktur samt kompressibiliteten av luft inuti PAM:en. Dessa olinjäriteter orsakar hysteresfenomenet i muskeln. För att implementera strategier för att kunna motverka denna effekt så måste den först modelleras. Till följd därav så undersöker denna avhandling två tillvägagångssätt, nämligen Maxwell-Slip (MS) och den generaliserade Bouc-Wen (BW) modellen. Inledningsvis identifieras testmuskelns initiala flätvinkel, maximala förskjutning och maximala kraft för att fastställa den statiska kraften med hjälp av en modifierad modell. Data samlas sedan in på PAM:ens kraft-förskjutningshysteres för 2-6 bar av tryck. Med hjälp av resultaten från dessa experiment identifieras MS- och BW-modellparametrarna genom optimering. Med de statiska och hystereskraftskomponenterna karakteriserade kan två kompletta dynamiska modeller framkallas. Resultaten visar att jämfört med den insamlade kraft-förskjutningsdatan har BW-modellen en större noggrannhet för alla tryck förutom vid 4 bar, men båda metoderna uppvisar resultat som är inom en godtagbar marginal. Slutligen genomförs en modellvalidering för att jämföra modellerna med hjälp av ett nytt dataset, annorlunda från den som de tränades på. Datan för detta test mäts vid ett tryck på 4 bar med en mer komplex referens som täcker fyra olika regioner av muskelns förskjutningsområde. Därefter tillämpas båda dynamiska modellerna för att bedöma deras prestanda. Det är uppenbart från resultaten att BW-modellen ger ett bättre resultat än MS-modellen, och uppnår ett normaliserat fel på 5,3746% jämfört med den sistnämndas 12,835%. Den högre noggrannheten hos den generaliserade Bouc-Wen-metoden beror sannolikt på att den har en mer komplex struktur, specialiserade parametrar och förmågan att modellera asymmetrisk hysteres. Maxwell-Slipmodellen kan däremot ändå vara att föredra i vissa sammanhang på grund av dess relativa simplicitet och snabbare optimering

[pt] Uma fase crítica do processo de obtenção do petróleo é a perfuração do solo para o acesso ao reservatório. Um dos problemas, em particular, é compreender o comportamento dinâmico da coluna de perfuração durante o processo de perfuração diante de diversos fatores como a interação broca-rocha, choques da coluna de perfuração contra a parede do poço, estratégias de controle da velocidade angular de operação e outros fatores. Uma etapa fundamental para lidar com este problema é a representação do sistema dinâmico para caracterizar a coluna de perfuração, isto é, o modelo matemático que representará a resposta dinâmica da estrutura diante dos carregamentos. Neste contexto, este trabalho abordará o problema da dinâmica de uma coluna de perfuração através de um modelo matemático baseado na teoria de Cosserat, que resultará em um sistema de seis equações diferenciais parciais que descrevem a resposta dinâmica de uma estrutura unidimensional, inserida no espaço euclidiano tridimensional, em termos das variáveis de deslocamento linear da curva e angular das seções. O modelo é capaz de descrever uma dinâmica não-linear, incluindo flexão, torsão, extensão e cisalhamento. Inicialmente, o sistema de EDPs é resolvido na forma quase estática, satisfazendo as condições de contorno, utilizando o método de Perturbação Regular. As soluções aproximadas são utilizadas como funções base para implementação no método de Elementos Finitos. Estas funções base são conhecidas como elemento de Cosserat Modificado (Modfied Cosserat Rod Element - MCRE). Verifica-se a limitação destas funções base para problemas que não envolvam grandes deslocamentos, não sendo adequadas para o problema proposto. Diante deste fato, o sistema de EDPs é escrito na forma fraca e resolvido por um software comercial de análise de Elementos Finitos considerando as condições de contorno, o modelo de interação broca-rocha, a estratégia de controle da velocidade angular e eventuais contatos da coluna contra a parede do poço. O modelo proposto produziu resultados que estão de acordo com a literatura e se mostrou capaz de lidar com grandes deslocamentos. / [en] A critical step in the oil exploration process is drilling the soil for access to the petroleum reservoir. One of the problems is understanding the dynamic behavior of the drill string during the drilling process in the face of various factors such as drill bit-rock interaction, drill string shocks against the well wall, angular velocity control strategies and other factors. A key part of dealing with this problem is the representation of the dynamic system to characterize the drill string, e.g., the mathematical model that will represent the dynamical response of the structure when facing different types of loads. In this context, this work will address the problem of the dynamics of a drill string using a mathematical model based on Cosserat theory that will result in a system of six partial differential equations that describe the dynamic response of a one-dimensional structure, inserted in three-dimensional Euclidean space, in terms of the linear displacement variables of the curve and angular displacement of the cross sections. The model is able to describe nonlinear dynamics, including flexure, torsion, extension and shear. Initially, the system of partial differential equations is solved in a quasi-static sense, satisfying the boundary conditions, using the Regular Perturbation method. The approximate solutions are used as shape functions for implementation in the Finite Element method. These shape functions are known as Modified Cosserat Rod Element (MCRE). It is verified that these shape functions are restricted to problems that do not involve large displacements and for this reason they are not suitable for the proposed problem. Given this fact, the system of partial differential equations is written in a weak form and solved by a commercial software based on Finite Element analysis, considering the boundary conditions, the drill bit-rock interaction model, the angular velocity control strategy and for any string contacts against the well wall. The proposed model produced results that are in agreement with the literature and is capable of dealing with large displacements.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Current ground-based tracking systems at the DoD test and training ranges require transmission of a variety of signals from rotating platform to fixed control and process center. Implementation of commercial off the shelf (COTS) solution for transmitting high-speed, multiple-channel data signals over a rotational platform prompt the development of an advanced electro-optic hybrid rotating-to-fixed information transmission technology. Based on current demand, an Air Force-sponsored Small Business Innovative Research (SBIR) contract has been awarded to Physical Optics Corporation (POC) to modify existing tracking mounts with a unique electro-optic hybrid rotary joint (EOHRJ). The EOHRJ under current development is expected to provide the following features: 1) include a specially designed electrical slip-ring, which is able to accommodate hundreds of transmission channels, including electrical power, control, feedback, and low-speed data signals; 2) include an optical fiber slip-ring which, by incorporating with electrical time division mulitplexing (TDM) and optical wavelength division multiplexing (WDM) technologies, is able to provide multiple channel, high data rate (over gigabits per second), and bi-directional signal transmission; and 3) is designed to be reliable for harsh environmental operation, adaptive to stringent size requirement, and accommodating to existing electrical and mechanical interfaces. Besides the military use, other possible commercial applications include on board monitoring of satellite spinners, surveillance systems, instrumentation and multi spectral vision systems, emergency/medical instruments, remote sensing, and robotics.

Cette thèse porte sur l'étude de l'amortissement des structures assemblées, et plus précisément de la contribution des assemblages sous sollicitations vibratoires. Le mémoire est composé de cinq chapitres traitant la problématique tant du point de vue analytique qu'expérimental. Un banc d'étude académique est proposé afin d'étudier des assemblages sous sollicitation normale constante (statique) et sous sollicitations tangentielles liées aux vibrations de la structure (dynamique). Le facteur de perte caractérisant l'amortissement de la structure est obtenu, dans un premier temps par une étude locale quasi-statique. Puis une fonction de dissipation est définie, permettant d'affiner la modélisation de l'amortissement par une étude dynamique globale. Au regard des résultats obtenus par la modélisation, une analyse expérimentale est menée. Cela afin d'isoler la contribution, à l'amortissement de la structure, des glissements partiels dans les assemblages. Pour cela, deux structures géométriquement identiques, l'une monolithique et l'autre assemblée sont étudiées. Les effets des interfaces sont analysés puis comparés aux résultats analytiques. Afin de simuler plus précisément ces effets, une modélisation prenant en compte les défauts de forme des surfaces en contact est menée / This thesis presents a study of damping in assembled structures, or, more precisely, a study of the vibrations of assemblies under external excitations. The paper contains five chapters examining this problem from both analytical and experimental viewpoints. An academic investigation is presented as a foundation in order to study assemblies both under constant normal stresses (static), and under tangential stresses linked to the structural vibrations (dynamic). The loss factor that characterizes the damping of the structure is obtained through a quasi-static local study. Then, a dissipation function is given, which allows the refinement of the damping model through a global dynamic study. An experimental analysis is undertaken to examine the results obtained by the modeling. The objective of this analysis is to isolate the effects, at the structural damping, of partial sliding in the assemblies. To isolate these effects, two structures identical in shape and material, one assembled and one uniform, are studied. The data collected from the interfaces are analyzed, and then compared to the analytical results. In order to simulate these effects with greater precision, a modeling is undertaken that takes into account the defects of form for the surfaces in contact

Nous menons une étude en simulations atomiques des propriétés des dislocations vis <a> dans le zirconium et le titane pur, et de l'effet durcissant de l'oxygène dans ces deux métaux de transition de structure hexagonale compacte. Nous utilisons deux modèles énergétiques : les calculs ab initio, basés sur la théorie de la fonctionnelle de la densité, et les calculs en potentiel empirique.Ce travail permet d'abord d'établir le profil énergétique complet de la dislocation vis dans le Zr pur au cours de ses différents modes de glissement. Nos calculs révèlent l'existence d'une configuration métastable de la dislocation vis partiellement étalée dans le plan pyramidal de première espèce. Cette configuration est responsable du glissement dévié de la dislocation vis du plan prismatique, plan principal de glissement, vers le plan pyramidal ou le plan basal. Ce profil énergétique est modifié par l'ajout d'atomes d'oxygène en impureté. L'oxygène favorise le glissement dévié dans le plan pyramidal ce qui entraine un durcissement du glissement prismatique, et il piège la dislocation dans la configuration métastable sessile.La même démarche de modélisation est ensuite appliquée au titane. Dans le Ti pur, les mêmes configurations de la dislocation vis dans le Zr sont obtenues, mais avec des niveaux énergétiques différents. Ceci conduit à un mécanisme de glissement différent. Tout comme dans le Zr, l'oxygène favorise le glissement pyramidal dans le Ti en affectant la structure de cœur de la dislocation. De plus, la présence de l'oxygène fait baisser l'énergie de la configuration métastable mais pas suffisamment pour la piéger. / We performed atomistic simulations to determine screw dislocations properties in pure zirconium and titanium and to explain the hardening effect attributed to oxygen alloying in both hexagonal close-packed transition metals. We used two energetic models: ab initio calculations based on the density functional theory and calculations with an empirical potential.The complete energetic profile of the screw dislocation when gliding in the different slip planes is obtained in pure Zr. Our calculations reveal the existence of a metastable configuration of the screw dislocation partially spread in the first order pyramidal plane. This configuration is responsible for the cross slip of screw dislocations from prismatic planes, the easiest glide planes, to pyramidal or basal planes. This energy profile is affected by oxygen addition. Ab initio calculations reveal two main effects: oxygen enhances pyramidal cross slip by modifying the dislocation core structure, and pins the dislocation in its metastable sessile configuration.The same modeling approach is applied to titanium. In pure Ti, the same configurations of the screw dislocation in Zr are obtained, but with different energy levels. This leads to a different gliding mechanism. The same way as in Zr, oxygen enhances pyramidal glide in Ti by modifying the dislocation core structure. Besides, oxygen atom lowers the energy of the metastable configuration but not enough to pin the dislocation in this sessile configuration.

O presente trabalho propõe o entendimento do comportamento no estado fresco de argamassas colantes, com base na caracterização reológica e físico-química de diferentes composições comerciais, servindo de base para analisar o fenômeno de deslizamento, a partir do ensaio estabelecido na norma brasileira. Para isso, foi utilizado o ensaio “Squeeze flow" (escoamento por compressão axial), empregado na caracterização de argamassas de revestimento no laboratório de microestrutura do CPqDCC da EPUSP, como ferramenta de análise do comportamento de argamassas colantes. Neste ensaio, o escoamento do material decorre da aplicação de uma carga de compressão sobre a amostra no estado fresco, a qual ocasiona deslocamentos no seu interior devido a esforços de cisalhamento radiais originados durante o fluxo. O critério de seleção das argamassas colantes comerciais (tipo AC-I) se baseou nos resultados do ensaio de deslizamento, escolhendo-se duas com resultado muito abaixo do limite especificado, duas com resultado próximo do limite e outras duas com resultado acima do mesmo. A composição química e física foi caracterizada com o objetivo de embasar a análise dos resultados obtidos no “Squeeze flow". A separação da fração fina das argamassas na peneira no.200 contribuiu para o conhecimento da viscosidade da pasta e da sua influência no comportamento reológico das argamassas. Foi observado que as argamassas estudadas apresentam diferenças de composição físico-química e de comportamento reológico. As diferenças de comportamento reológico das argamassas decorrem, provavelmente, de ação sinérgica de alguns parâmetros da composição, com destaque para a distribuição granulométrica. O “Squeeze flow" mostrou-se uma ferramenta adequada na caracterização das argamassas colantes e contribuiu para explicar o deslizamento estabelecido na norma brasileira, pela proposição de modelos hipotéticos de comportamento. / Present thesis proposes the study of plastic-state behaviour of dry-set mortars based on the rheological and physicochemical characterization of different commercially available dry-set mortar compositions. Such characterization served as basis for the analysis of dry-set mortar slip phenomena using the tests recommended by brazilian standards (NBR). The Squeeze Flow test (slip by axial compression) originally used for coating mortars characterization by the EPUSP CPqDDC Microstructure Laboratory was adopted as a test tool for analysing the dry-set mortar behaviour. In the mentioned test the material slip is obtained by compressing the sample in its plastic state which caused internal displacements due to radial shearing tensions originated during the mentioned slip. The dry-se mortars (all of them AC-I type) used in the study were selected based in the slip tests results against brazilian standards specified limits resulting in the selection of two dry-set mortars below the specified limit, two dry-set mortars close to the specified limit and dry-set mortars above the specified limit. Chemical and physical compositions were characterized in order to serve as basis for Squeeze Flow results analysis. Fine fraction segregation, using number 200 sieve contributed to understanding of plastic-state mortar viscosity and its influence in mortar rheological behaviour. It was observed diverse physicochemical and rheological behaviour among the studied dry-set mortars. The rheological behaviour diversity of dry-set mortars were due to the synergy among some composition parameters, specially the granular distribution. The Squeeze Flow was considered a suitable tool for the characterization of dry-set mortars and contributed to develop hypotetical behaviour models that allowed to explain the slip as stated by brazilian standards.

La Mongolie occidentale a connu une sismicité intracontinentale exceptionnelle au cours de la première moitié du XXe siècle, avec 4 évènements sismiques d'une magnitude supérieure à 7.9, localisés sur des grandes structures décrochantes en régime transpressif senestre. Cette sismicité historique a été qualifiée d’essaim sismique, et des études paléosismologiques indiquent que ce phénomène a déjà pu se produire par le passé (3 à 4 ka). Mais si la partie est de la chaine du Gobi-Altaï a rompu lors du séisme du même nom en 1957 (Mw8) le long de la faille de Bogd orientale (WBF), plusieurs traces de failles affectant des formations Holocènes et présentant des longueurs > 100 km ont été documentées dans la partie ouest du massif, sans pour autant faire l’objet d’études quantitatives.Cette thèse apporte un état des lieux de l’activité sismique dans le Gobi-Altaï, au travers d’une cartographie détaillée des escarpements de failles actives au cours du pléistocène supérieur, associée à une analyse de la segmentation au regard de critères géométriques et cinématiques. Parallèlement, des investigations morphotectoniques et paléosismologiques, couplées à des méthodes de datations au 10Be in situ, OSL et 14C, ont permis de quantifier les vitesses de glissement depuis le Pléistocène supérieur, et les âges des paléo-ruptures au cours de l’Holocène sur les deux principaux décrochements analysés : les failles de la Vallée des Lacs (VOLF), et de Bogd occidentale (WBF) ; des données préliminaires permettent également de contraindre l’âge de la dernière rupture et la vitesse de glissement sur les failles de Tsogt (TF) et de Tsagaan Gol (TGF), situées respectivement dans le prolongement occidental de la WBF et de la VOLF. De plus, des mesures systématiques des décalages cosismiques horizontaux enregistrés par la morphologie, notamment le long de la rupture de surface du séisme de 1957, couplés à l’utilisation et le développement d’une approche statistique de détermination des glissements cosismiques moyens au regard de la segmentation, a permis de déterminer la fonction de distribution du glissement le long de l’EBF sur 3 cycles sismiques, suggérant d’une part une distribution du glissement assez homogène le long de la rupture, et d’autre part que le glissement du séisme généré en 1957 est d’une amplitude comparable de celle des précédents séismes, pour au moins 50 % de la rupture principale. Cette approche de détermination statistique des glissements moyens sur plusieurs cycles sismiques est prometteuse mais présente néanmoins certaines incohérences, et des voies de développement et de validations sont proposées.Les paramètres morphotectoniques et les âges des paléoséismes documentés dans cette thèse présentent une grande cohérence avec les données précédemment acquises sur l’EBF, avec des vitesses de faille lentes (0,7 ± 0,2 mm.a-1 sur la WBF et 0,5 ± 0,1 mm.a-1 sur la VOLF), des périodes de retour longues (4,0 ± 1,2 ka pour la WBF), et des décalages cosismiques relativement importants (2 – 4 m). Nos mesures de vitesses de faille indiquent par ailleurs une distribution de la déformation depuis la EBF vers les WBF et VOLF, séparant la déformation en deux faisceaux de failles, l’un se branchant au nord depuis la VOLF sur la TGF. Les déterminations des âges de paléoséismes indiquent une possibilité de cluster entre les différentes failles étudiées, avec trois ruptures potentiellement synchrones au cours de l’Holocène, dont une, rompant l’intégralité des décrochements analysés (WBF, EBF et VOLF), s’avère être temporellement corrélée au précédent cluster potentiellement identifié à 3 – 4 ka. Les paramètres présentés dans cette thèse permettent finalement de calculer des paléomagnitudes associées aux deniers évènements sur les WBF et VOLF, comprises entre Mw7,6 et Mw8 selon les paramètres et les lois considérés. Ces données fondamentales pourront servir de canevas de base pour les actuelles études d’aléas sismique en Mongolie. / Western Mongolia experienced an exceptional intracontinental seismic activity during the first part of the XXth century, with four seismic events with Mw > 7.9, located on large strike-slip faults with a transpressive left-lateral motion. This historical seismicity has been qualified as a cluster, and paleoseismological studies indicate that this phenomenon might have occurred 3 to 4 ka ago. Although the eastern part of the Gobi-Altai mountain range broke during the eponymous earthquake in 1957 (Mw8) along the Eastern Bogd Fault (EBF), several fault traces affecting Holocene formations and presenting continuous fault length > 100 km have been documented on the western part of the range, while not been the purpose of quantitative studies.This thesis first gives an inventory of the seismic activity within the Gobi-Altai, through detailed mapping of the fault scarps which show activity during the late-Pleistocene, also with an analyze of the fault segmentation regarding to geometric and kinematic criteria. Secondly, some morphotectonical and paleoseismological surveys have been carried on, along with dating techniques as 10Be in situ, OSL and radiocarbon, which allow quantifying the faults slip-rates since late-Pleistocene, and paleo-ruptures ages during the Holocene period on the two main strike slip faults analyzed : the Valley of Lakes Fault (VOLF), and the Western Bogd Fault (WBF); preliminary data also allow quantifying the slip rates and the age of the most recent event along the Tsogt Fault (TF) and the Tsagaan Gol fault (TGF), respectively located in the westward continuation of the WBF and the VOLF. Moreover, systematic lateral offset measurements have been carried on along the faults traces, and especially along the 1957 surface rupture, where a statistical approach based on probability density has been applied in order to assess the average lateral offsets successively recorded by the landforms, and reveals that the slip distribution along the EBF on 3 seismic cycles. This suggests first that the slip distributions rather even along the rupture, and secondly that the slip related to the 1957 earthquake is of the same amount than previous major ruptures on that fault, for half of the main 1957 surface rupture. This approach of average coseismic slip assessment on several seismic cycles is promising, but still presents some inconsistencies, and we propose developments and validation perspectives.Morphotectonic parameters and ages of paleo-earthquakes reported in this thesis present a strong consistency with former studies along the EBF, with slow slip-rates (0,7 ± 0,2 mm.yr-1 on the WBF and 0,5 ± 0,1 mm.yr-1 on the VOLF), and significant left lateral coseismic offsets (2 – 4 m). Our measurements of slip rates indicate furthermore a distribution of the on-fault deformation from the EBF to the WBF and the VOLF, splitting the deformation in two branches, the north one reaching the TGF and the southern one visibly branches on the TF. Assessments of the paleoearthquakes ages show three possible clusters between the studied faults during the Holocene time, and one of them may break the three faults (WBF, EBF and VOLF), and seems as well to correspond to the cluster possibly identified 3-4 kyr ago. The fault parameters presented in this thesis allow computing the paleomagnitudes related to last seismic events along the WBF and the VOLF, ranging from Mw7.6 and Mw8, depending of parameters and empirical relations considered. Finally those fundamental data may serve as basic pattern for current seismic hazard assessments in Mongolia.

Les observations récentes ont mis en évidence la diversité des régimes de glissement des failles, et particulièrement l'existence de glissements asismiques transitoires, les séismes lents. Ce travail a pour objectif la compréhension de l'impact de ces séismes lents sur le cycle sismique. La zone étudiée correspond à la zone de subduction du sud du Mexique, au niveau de la lacune sismique de Guerrero. A partir de mesures de déplacement de surface, principalement par GPS, le glissement sur l'interface de subduction est modélisé par des dislocations dans un milieu élastique. Cette analyse nous permet de contraindre l'évolution spatio-temporelle de deux épisodes de glissements lent (2006 et 2009-2010), ainsi que le couplage de l'interface de subduction. Nos résultats montrent une certaine variabilité dans l'évolution spatio-tempororelle des deux glissements étudiés : le séisme lent de 2006 présente clairement une propagation du glissement, à une vitesse d'environ 1 km/jour ; le séisme lent de 2009-2010 présente deux sous-évènements, l'occurrence du deuxième sous-évènement étant liée au déclenchement par le séisme de Maule au Chili. Nos résultats mettent également en évidence les variations latérales dans le couplage intersismique de l'interface de subduction : le couplage dans la lacune sismique de Guerrero étant 4 fois plus faible que le couplage de part et d'autre de la lacune. Ainsi la majeure partie du glissement est accommodée par les séismes lents dans la lacune sismique de Guerrero. / Recent observations reveal the existence of different slip behaviors on fault, and among them the occurrence of transient aseismic slip events, the so-called slow slip events (SSEs). The general goal of this work is to understand the impact of slow slip events on the seismic cycle. The area of study is located in the southern Mexican subduction zone, around the Guerrero seismic gap. We use continuous GPS measurements of the ground displacements to model the slip on the subduction interface, using a dislocation model in an elastic half space. We can thus constrain the spatial and temporal evolution of two slow slip events (in 2006 and in 2009-2010), as well as the coupling ratio of the subduction interface. Our results highlight the differences in the spatio-temporal evolution of the two slow slip events : during the 2006 SSE, the slip propagated at a velocity of 1 km/day. The 2009-2010 SSE occurred in two sub-events and the second sub-event was triggered by the surface waves of the Maule earthquake (in Chili). Our results also show the lateral variations in the interseismic coupling of the subduction interface : the coupling ratio in the Guerrero gap being only 1/4 of the couling ratio on both sides of the gap. Most of the slip is thus accommodated by slow slip events in the Guerrero seismic gap.

Ces vingt dernières années, le développement de réseaux haute résolution sismologiques et géodésiques denses a permis la découverte de nouveaux signaux géophysiques parmi lesquels on trouve les trémors non-volcaniques (Non-volcanic tremor, NVT, Obara 2002) et les glissements lents épisodiques (Slow Slip Event, SSE, Dragert et al., 2001). La combinaison de NVT et de SSE est communément observée le long des frontières de plaques, entre la zone sismogénique bloquée à faible profondeur et la zone en fluage ductile à plus grande profondeur (Dragert et al., 2004). Cette association définie des glissements et trémors épisodiques (Episodic Tremor and Slip, ETS), systématiquement associés à des surpressions de fluides et à des conditions proches de la rupture. Dans cette thèse, nous proposons de combiner une étude microstructurale de roches exhumées avec une approche par modélisation numérique afin de reproduire et de mieux comprendre la mécanique des glissements et trémors épisodiques.Nous nous sommes concentrés sur des roches continentales provenant de la Zone de Cisaillement Est du Tende (Corse, France), correspondant à une zone de cisaillement Alpine kilométrique ayant enregistré une déformation dans la zone de subduction (10 kb / 400-450°C, Gueydan et al., 2003). Ces conditions pression-température sont cohérentes avec la localisation des ETS dans les zones de subduction. Les analyses microstructurales et EBSD de ces roches mettent en évidence des localisations de la déformation le long de zones de cisaillement centimétriques contrôlées par une rhéologie dépendante de la taille des grains. La microfracturation de la phase dure (ici du feldspath) et le colmatage de ces microfractures correspondent, respectivement, à de processus de réduction et d’augmentation de la taille des grains.La plupart des récentes modélisations des ETS sont basées sur une loi frictionnelle dite rate-and-state, associant les SSE et les NVT à un cisaillement sur un plan. Contrairement à ces modèles, nous souhaitons modéliser l’ensemble de la roche (et non pas uniquement un plan) avec une rhéologie ductile dépendante de la taille des grains directement guidée par nos observations microstructurales (avec microfracturation et colmatage), Nous faisons l’hypothèse que les SSE peuvent résulter d’une localisation ductile de la déformation et non d’un glissement sur des fractures. Durant la localisation de la déformation, le pompage des fluides peut déclencher une fracturation de la roche par surpression de fluide, ce qui pourrait être la signature des NVT. Le modèle numérique 1D présenté ici nous permettra de valider ces hypothèses. En suivant la loi de Darcy, notre approche nous permet également de prédire les variations de la pression de pore en fonction des variations de la porosité/perméabilité et du pompage des fluides.Les résultats numériques montrent que l’évolution dynamique des microstructures, dépendante des fluides, définie des cycles de localisation ductile de la déformation liés aux augmentations de la pression de fluide. Notre modèle démontre que la disponibilité des fluides et l’efficacité du pompage des fluides contrôlent l’occurrence des ETS. Nous prédisons également les conditions pression-température nécessaires au déclenchement des ETS : 400-500°C et 30-50 km de profondeur en subduction, et ~500°C et 15-30 km de profondeur le long des zones de décrochement. Ces conditions PT sont cohérentes avec les exemples naturels.Aussi simple soit-elle, notre modèle mécanique s’appuyant sur des observations de terrain décrit correctement la relation entre surpressions de fluides, rhéologie dépendant de la taille des grains et le déclenchement des ETS. Des travaux restent à entreprendre comme par exemple la comparaison directe de nos résultats avec des données géophysiques (GPS) ou bien l’introduction d’un nouvelle assemble minéralogique, comme par exemple des roches mafiques pour prendre en compte des minéralogies océaniques. / These last twenty years, the development of dense and highly sensitive seismologic and geodetic networks permits the discovery of new geophysical signals named non-volcanic tremor (Obara 2002) and slow slip events (Dragert et al., 2001). The combination of non-volcanic tremor and transient slow slip is commonly observed at plate interface, between locked/seismogenic zone at low depths and stable/ductile creep zone at larger depths (Dragert et al., 2004). This association defines episodic tremor and slip, systematically highlighted by over-pressurized fluids and near failure shear stress conditions. In this thesis we propose to combine a microstructural analysis of exhumed rocks with a modeling approach in order to accurately reproduce and understand the physics of episodic tremor and slip.We focus on continental rocks from the East Tenda Shear Zone (Corsica, France), a kilometer-wide localized Alpine shear zone that record HP/LT deformation (10kb / 400-450°C, Gueydan et al., 2003). Such pressure-temperature conditions are consistent with the location of episodic tremor and slip in subduction zone. Microstructural and EBSD analyses on these rocks describe a pattern of strain localization in centimeter-scale shear zones guiding by a grain size-sensitive creep. Microfracturing of the strong phase (feldspar here) and the sealing of these microfractures act, respectively, as grain size decrease and grain size increase processes.Most of recent modeling approaches of episodic tremor and slip are based on the rate-and-state variable friction law, describing slow slip event and non-volcanic tremor as slow shear slip on a plane. In contrast with such models, we wish to model the entire rock volume, with a ductile grain size-sensitive rheology guided by our microstructural observations (e.g. microfracturing and sealing as grain size variation processes). We hypothesize that slow slip events may result from ductile strain localization and not transient slip on fractures. Fluid pumping during strain localization may trigger whole rock fracturing at near lithostatic conditions that can be the signature of non-volcanic tremor. The 1D numerical model presented here will allow us to validate these assumptions.We also can predict pore fluid pressure variation as a function of changes in porosity/permeability and strain rate-dependent fluid pumping following the Darcy’s flow law. The fluid-enhanced dynamic evolution of microstructure defines cycles of ductile strain localization related to the increase in pore fluid pressure. We show that slow slip events can be ductile processes related to transient strain localization, while non-volcanic tremor can correspond to fracturing of the whole rock at peak of pore fluid pressure. Our model shows that the availability of fluids and the efficiency of fluid pumping control the occurrence of episodic tremor and slip. We also well predict the temperature and depth ranges of episodic tremor and slip: 400-500°C and 30-50 km in subduction zones and ~500°C and 15-30 km in strike slip settings, consistent with natural examples.As simplistic as it is, our field-guided mechanical model well describe, at first order, the relation between high pore fluid pressure, grain size-sensitive rheology and episodic tremor and slip. Some efforts remain to be done like a real fit of geophysical data (GPS) or the introduction of the new mineralogical assemblage, such as mafic rocks to reproduce oceanic environment.

A falta de controle e planejamento dos espaços públicos, entre eles, as calçadas, gera problemas como a falta de segurança e de acesso aos equipamentos urbanos e até impede a livre circulação das pessoas. As calçadas são uma pequena, mas importante parte da complexa infraestrutura urbana. O provimento de calçadas adequadas é um meio de incentivo ao deslocamento a pé e ao uso de transporte coletivo. A calçada não deveria oferecer nenhum risco aos pedestres, porém, grande parte das calçadas existentes no Brasil é imprópria para a circulação, seja pela existência de obstáculos, seja pela precariedade ou inadequação dos materiais utilizados em sua construção. Essa falta de qualidade das calçadas é a causa de muitos acidentes. Os pedestres em geral e, além dos idosos, principalmente as crianças e as pessoas portadoras de necessidades especiais, podem ser considerados usuários vulneráveis. No presente trabalho, as exigências dos usuários, no que se refere à segurança em uso, de acordo com a abordagem de desempenho, foram identificadas como sendo segurança ao risco de quedas, segurança ao risco de atropelamentos, segurança ao risco de lesões por choque e acessibilidade. As exigências dos usuários foram traduzidas em requisitos de desempenho a serem cumpridos em calçadas seguras e, após, foram identificados os respectivos critérios, níveis de atendimento e métodos de avaliação, com base na legislação e bibliografia. Com isso, foi elaborado um instrumento de avaliação de segurança em calçadas. Um estudo de caso em um trecho da Av. Independência, em Porto Alegre, foi realizado para testar o instrumento elaborado, com aplicação experimental em 17 calçadas. O instrumento mostrou-se eficiente na aquisição, processamento e registro de dados. Para a validação definitiva do instrumento, é necessário que se amplie os testes. Além disso, foi realizada pesquisa exploratória com aplicação do ensaio com o Pêndulo Britânico, para avaliação da resistência ao escorregamento. Todas as calçadas foram aprovadas quanto a este critério. O método de avaliação se mostrou adequado, porém limitado a calçadas com pequena inclinação. Adicionalmente, as diversas falhas relativas à segurança encontradas nas calçadas avaliadas foram analisadas. Nenhuma calçada do estudo de caso foi aprovada e considerada segura. A calçada com pior desempenho atendeu a apenas 38,88% dos critérios. Já o melhor resultado foi de uma calçada com taxa de atendimento aos critérios de 68,42%. Os critérios menos atendidos foram o desnível em relação à via, o rebaixo para acesso de veículos adequado, rampa nos pontos de travessia e a sinalização tátil no piso. Diante da grande quantidade de falhas encontradas no estudo de caso, aponta-se a ausência de um técnico no processo de construção de uma calçada, como uma das principais causas das não conformidades, junto à falta de um documento, preferencialmente uma Norma Técnica, que reúna as informações necessárias para o projeto de calçadas. Desta forma, este trabalho visa contribuir para o tema desempenho de calçadas, com foco nos requisitos relativos à segurança dos usuários. / The absence of control and planning of public spaces, including sidewalks, creates problems such as lack of security and access to urban equipment and even prevents the free movement of people. The sidewalks are a small but important part of the complex urban infrastructure. Providing adequate sidewalks is a means of encouraging walking and the use of public transport. The sidewalk should not pose any risk to pedestrians, but most of the existing sidewalks in Brazil are unfit for circulation, either by the existence of obstacles, or by the precariousness or inadequacy of the materials used in their construction. This lack of quality in sidewalks is the cause of many accidents. Pedestrians in general and, in addition to the elderly, especially children and people with special needs, can be considered vulnerable users. In this work, users' requirements regarding safety in use, according to the performance approach, have been identified as safety for the risk of falls, safety for the risk of pedestrian crashes, safety for the risk of shock injuries and accessibility. The users’ requirements were translated into performance requirements to be met on safe sidewalks and, afterwards, the respective criteria, suitable levels and evaluation methods were identified, based on legislation and bibliography. And therewith, a safety assessment instrument for sidewalks was developed. A case study on an excerpt from Av. Independência, in Porto Alegre, was carried out to test the instrument, with experimental application on 17 sidewalks. The instrument was efficient in data acquisition, processing and recording. For definitive validation of the instrument, it is necessary to expand the tests. In addition, an exploratory study was carried out with the application of the British Pendulum test to evaluate the slip resistance. All sidewalks were approved for this criterion. The method of evaluation was adequate, but limited to sidewalks with a small slope. In addition, the various safety flaws found on the evaluated sidewalks were analyzed. No sidewalk from the case study was approved and considered safe. The sidewalk with the poorest performance met only 38.88% of the criteria. The best result was a sidewalk with a rate of meeting the criteria of 68.42%. The least attended criteria were the height in relation to the roadway, adequate vehicle access ramp, ramp at crossing points and tactile signage on the ground. Considering the large number of flaws found in the case study, it is pointed out that the absence of a technician in the process of building a sidewalk is one of the main causes of nonconformities, due to the lack of a document, preferably a Technical Standard, that gathers the necessary information for sidewalk projects. Thus, this work aims to contribute to the theme of performance of sidewalks, focusing on requirements regarding user safety.