Résumé : La technologie des armatures en matériaux composites de polymères renforcés de fibre (PRF) reste relativement récente (moins de 20 ans) et souffre d’une moins bonne réputation en termes de durabilité, ce qui tend à freiner son acceptation par les professionnels du secteur. Les travaux présentés dans ce mémoire ont pour but d’étudier les effets de l’humidité et de l’alcalinité sur les performances mécaniques et thermomécaniques de barres d’armature en PRF. Si de nos jours l’évolution des propriétés des armatures de PRF a été largement étudiée par différents chercheurs, nous n’avons que peu d’informations sur les modes de dégradation qui entrainent ces pertes de performances. Le but des travaux entrepris dans ce mémoire est de trouver des pistes d’investigation pour la compréhension de ces mécanismes de dégradation qui pourraient éventuellement par la suite être reprises dans le cadre de travaux de thèse. Les travaux qui ont été entrepris s’articulent autour de deux projets. Le premier s’intéresse à l’étude du vieillissement accéléré de barres de polymère renforcé de fibres de verre (PRFV) de différents diamètres et soumis à un environnement humide. Le second s’intéresse à l’étude de barres de PRFV et de polymère renforcé de fibres de basalte (PRFB) de même diamètre soumis à un environnement alcalin qui simule le milieu interstitiel du béton. / Abstract : The FRP rebars technology remains relatively recent and suffers from a bad reputation in terms of durability which slows its acceptation among the professionals of the construction field. The aim of the work presented in this essay is to study the effects of moisture and alkalinity on the mechanical and thermo mechanical performances of FRP rebars. Nowadays, the progressions of FRP performances have been widely studied by different researchers but we still have few knowledge about the modes of degradation which lead to performance losses. The final goal of this work is to find investigation trails for the understanding of those degradation mechanisms which could possibly be taken over as part of a thesis work. The work is divided into two projects. The first one is the study of accelerated aging of glass fibers reinforced polymer (GFRP) rebars, of different diameters, conditioned in a moist environment. The second one concerns the behavior of GFRP and basalt fibers reinforced polymer (BFRP) rebars, of same diameter, conditioned in an alkaline environment which simulates the interstitial solution of concrete.

As we move into the twenty-first century, the renewal of our lifelines or deterioration of infrastructure becomes a topic of critical importance. The structures may have to carry larger loads, require change in building use, suffer steel corrosion problems, or errors made during the design or construction phases so that the structure may need to be repaired or strengthened before it can be used. The use of fiber reinforced polymers (FRP) in the last few years in various engineering application, forums and configuration offers an alternative design approach for the construction of new concrete structures and the rehabilitation of existing ones. The use of FRP materials for external strengthening of reinforced concrete (RC) structures has emerged as one of the most exciting and promising technologies in material and structural engineering. Externally bonded FRP reinforcement is relatively unprotected against impact, vandalism or severe environmental conditions. Their structural performance can be greatly affected by these drawbacks. But if the composite material is placed in slots inside the concrete cover some of these drawbacks can be overcome. This method is designated by Near Surface Mounted (NSM) method. Therefore, the presented work is carried out using this advantageous strengthening technique utilizing the non-corrodible FRP materials. My research involved both experimental and analytical investigations on the use of FRP systems for strengthening concrete structures using NSM techniques. The main objectives of my research were to (1) develop/utilize an NSM system composed of FRP bars and adhesives, (2) investigate the bond performance for the proposed NSM system, (3) investigate the effect of freeze and thaw cycles on the of the new proposed system, (4) study the flexural behaviour of RC beams strengthened with NSM FRP bars, (5) develop an analytical model using non-linear finite element analysis (ADINA) taking into consideration the interfacial behaviour between the concrete and FRP bars and (6) establish design recommendations for the use of FRP bars for the NSM method. To achieve these objectives, the research program was divided into two parts. The first part included the experimental work while the second part included the analytical work. The first part consisted of two phases. The first phase included the pullout testing of 76 C-shape concrete blocks including 16 conditioned blocks. The second phase included testing 20 flexural strengthened concrete beams using the NSM method. The second part included developing an analytical model to be used in a non-linear finite element program and to analyze and predict the behaviour of concrete beams strengthened for flexure using NSM FRP bars. The efficiency and accuracy of the model was verified by comparing its results to the experimental results. The developed analytical model was used to study the effect of different parameters. Test results are presented in terms of deflection, strain in the concrete, steel and FRP and modes of failure. Test results showed the superior performance of the proposed NSM FRP/adhesive system. The NSM system is able to increase both the stiffness and flexural capacity of concrete beams by approximately 100% over the unstrengthened one. The FEM was able to predict of the behaviour of the strengthened beams in flexure with NSM. Based on the experimental and analytical study, useful conclusions and recommendations for flexural strengthening with NSM FRP were provided.||Alors que nous entrons dans le XXIème siècle, la dégradation des infrastructures devient un sujet d'une importance cruciale. Les structures doivent supporter des charges plus grandes et subir des changements d'utilisation. En plus de cela s'ajoute les problèmes de corrosion de l'acier, des erreurs de conception et de construction, ce qui souvent nécessitent que la structure soit réparée ou renforcée, des fois même avant sa mise en service. L'utilisation de polymères renforcés de fibres (PRF) dans les dernières années dans divers domaines d'ingénierie a permis une avancée technologique, et leur utilisation dans la construction de nouvelles structures en béton ainsi que la réhabilitation des anciennes. L'utilisation de matériaux en PRF pour le renforcement externe des structures en béton armé est une technologie des plus prometteuses dans l'ingénierie structurale ou de matériaux. Cependant le renforcement par collage externe de PRF n'offre pas une bonne protection contre les chocs, le vandalisme ou les conditions environnementales sévères, ce qui pourraient affecter les performances structurales des éléments réhabilités. Ces inconvénients peuvent être surmontés si le PRF est inséré dans des rainures réalisées dans le recouvrement de béton. Cette méthode est appelée « mise en place d'Armatures Encastrées Près de la surface (AEPS)». Le présent travail s'articule autours de cette technique de renforcement utilisant des matériaux non corrodables. Mes travaux de recherches se focalisent sur l'utilisation des AEPS en PRF pour le renforcement des structures, et cela d'un point de vue expérimental et analytique. Les principaux objectifs de mes recherches sont: (1) développer/utiliser un système d'AEPS composé de barres en PRF et d'adhésif, (2) étudier les performance d'adhérence du système proposé, (3) étudier l'effet des cycles gel-dégel sur le système proposé, (4) l'étude du comportement en flexion de poutres en béton armé, renforcées avec des barres d'AEPS en PRF, (5) développer un modèle analytique utilisant des méthodes non-linéaires d'analyse par éléments finis (logiciel ADINA) en tenant compte du comportement de l'interface béton-barres en PRF, et (6) mettre en place des recommandations de calcul pour l'utilisation des barres en PRF comme AEPS. Pour atteindre ces objectifs, le programme de recherche a été divisé en deux parties. La première partie comprenait les travaux expérimentaux tandis que la deuxième comprenait des travaux d'analyse. La première partie elle même était constituée de deux phases. La première phase comprenait des essais d'arrachement direct de blocs de béton en forme de «C», dont 16 blocs conditionnés dans une chambre environnementale. Alors que la deuxième phase comportait des essais de flexion 20 poutres en béton armé, renforcés par des AEPS en PRF. La deuxième partie a consisté au développement d'un modèle analytique non-linéaire par éléments finis de façon à pouvoir analyser et prédire le comportement en flexion de poutres en béton armé, renforcées par des AEPS en PRF. L'efficacité et la précision du modèle ont été vérifiées en comparant ses résultats analytiques aux résultats expérimentaux. Le modèle analytique développé a été utilisé pour étudier l'effet de différents paramètres. Les résultats des tests sont présentés en termes de déflexion, de contraintes dans le béton, l'acier et le PRF et les modes de rupture. Les résultats des essais ont démontré les bonnes performances du système armatures PRF/adhésif proposé, ce dernier a permit d'augmenter à la fois la rigidité en flexion et la résistance des poutres en béton d'environ 100% par rapport à la poutre non renforcée. L'analyse par éléments finis a été en mesure de prédire le comportement en flexion des poutres renforcées avec des AEPS en PRF. Basé sur ces travaux, des conclusions et des recommandations utiles concernant le renforcement en flexion avec des AEPS en PRF ont été fournis.

Les microlithes sont retrouvés souvent en grand nombre dans les niveaux archéologiques attribués au Mésolithique. Dès leur découverte durant le dernier quart du XIXe, ils ont attiré toute l’attention des préhistoriens, d’une part, par leurs dimensions réduites et la variabilité de leurs formes dites parfois géométriques et, d’autre part, parce qu’ils étaient les seuls représentants de ce qui pouvait alors passer pour un outillage préhistorique au sein d’un assemblage lithique déconcertant et d’une industrie particulièrement pauvre en outillage osseux. Notre propre travail naît du constat que les classifications traditionnelles des microlithes attribués à la période Mésolithique ne sont pas suffisantes pour caractériser les systèmes techniques dont ils sont issus. Si ces classifications sans lien avec une réalité fonctionnelle précise ont servi à sérier le Mésolithique et à en décrire la variabilité géographique, la variabilité mise en évidence ne permet pas d’expliquer les dynamiques culturelles expliquant cette diversité des faits techniques. Nous avons donc appréhendé le microlithisme comme un équipement, plus précisément une partie d’un équipement vulnérant répondant à un besoin physico-technique fondamental pour les sociétés de chasseurs de l’Holocène, à savoir acquérir leurs ressources carnées. L’observation à la loupe binoculaire de l’ensemble de notre corpus nous a permis d’accéder à une vision très précise des caractéristiques morphologiques des supports et des méthodes de retouche. Celle-ci nous a conduite à proposer de nouveaux critères pour la classification morphotechnique des microlithes. En parallèle, nous avons mis en place une batterie d’expérimentations nous permettant de tester le piétinement, la fabrication et l’utilisation des armatures de projectile de ces objets. Ces tests nous ont permis de créer un modèle fonctionnel interprétatif de la fragmentation et de la dispersion des microlithes selon leur position sur la hampe. Ils nous ont également fourni la possibilité d’évaluer leur efficacité et leur rôle selon leurs caractéristiques morphotechniques. La dernière partie de notre travail est consacrée à un retour sur notre corpus archéologique. La synthèse de nos résultats permet d’établir un pont entre nos résultats expérimentaux et nos observations archéologiques de façon à proposer de nouvelles explications sur le fonctionnement des microlithes mésolithiques. / Microliths are often found in large numbers in archaeological layers attributed to the Mesolithic. Since their discovery in the last quarter of the nineteenth century they have attracted the attention of prehistorians, firstly because of their small size and the variability of their shapes – oftentimes described as geometric – and secondly because they were the only representatives of what appeared to constitute a prehistoric toolkit within a little understood lithic assemblage and a particularly meagre bone tool industry. Our own work originates from the observation that traditional classifications of microliths attributed to the Mesolithic period are not sufficient to characterize the technical systems that produced them. Even though these classifications were unrelated to a specific functional reality, until now they were used to classify the Mesolithic and describe its geographic variability. But they did not allow us to highlight the cultural dynamics explaining the diversity of technical artefacts. We thus approached the microlith as a piece of equipment, specifically a wound-generating tool which fulfilled a fundamental physical-technical need for the Holocene societies of hunters; namely that of acquiring meat. The minute observation of our entire collection of microliths using a stereomicroscope allowed us to acquire a clear understanding of the morphological characteristics of the supports and re-sharpening methods that were used. This led us to propose new criteria for the morpho-technical classification of microliths. In parallel, we have developed a series of experiments specifically designed to test the trampling, the manufacture and the usage of these objects as projectile arms. These tests allowed us to create an interpretive functional model of fragmentation and dispersion of microliths according to their position on throwing shaft. These tests also provided the opportunity of evaluating their effectiveness and their role according to their morpho-technical characteristics. The last part of our work is devoted to a re-analysis of our archaeological collection. The summary of our results allows us to establish a bridge between our experimental results and our archaeological observations to propose some preliminary explanations on the workings of Mesolithic microliths.

Pour déterminer la vulnérabilité sismique des structures en béton armé, des méthodes de calcul numérique à l’échelle structurelle, effiaces et suffisamment précises, sont nécessaires. Des formulations d’éléments finis bidimensionnels ou tridimensionnels, largement utilisées, fournissent des résultats fiables. Cependant, ces types de méthodes impliquent un grand nombre de degrés de liberté et des lois de comportement robustes 3D pour le béton et l’acier, afin de capturer avec précision les non-linéarités dans les éléments élancés de structure en béton armé. Une autre méthode plus pratique dans le domaine de l’ingénierie des structures est l’utilisation des éléments de poutres multifibres. C’est la méthode adoptée dans ce travail de thèse.Les éléments poutres multifibres permettent de discrétiser la structure à l’aide d’éléments linéiques qui portent une section discrétisée dans le sens transversal en faisant l’hypothèse de cinématique d’Euler Bernoulli ou Timoshenko. La discrétisation de la section permet d’utiliser simplement des lois de comportement non linéaires et de modéliser des sections composites comme le béton armé. Néanmoins, il existe des limitations à ce genre de modèle. Ainsi, plusieurs recherches ont été menées, ces dernières années pour enrichir les éléments poutres afin de reproduire correctement les effets de cisaillement surtout dans le cas de poutres peu élancées où l’effet de cisaillement est non négligeable. Comme l’approche proposée par [VEC 88] adéquate pour les chargements bidimensionnels mais ne reproduisant pas l’effet de torsion, celle présentée par [LEC 12], mais dont le modèle ne peut pas être appliqué aux éléments en béton armé, et la formulation numérique de [MOH 10] qui est adaptée aux applications en béton armé mais ne fonctionne qu’en 2D. Plus récemment ([CAP 16b]; [CAP 16a]) et son équipe ont développé une technique adaptée au béton armé, qui prend en compte le gauchissement de la section et permet de calculer un état de déformation dans les fibres de béton sous des sollicitations 3D. Dans les travaux cités plus haut, soit les cadres d’armatures transversales ne sont pas du tout pris en compte, soit ils le sont de manière trop approximative. Cependant, comme le montrent certains essais expérimentaux menés par [CUS 95], la quantité de ferraillage transversal déclenche de manière significative le comportement des éléments structuraux, notamment sous chargement cyclique.Basé sur les travaux de [LEC 12] et [CAP 16a], ce travail de thèse vise à modéliser l’effet des armatures transversales sur le comportement du béton. La démarche proposée est d’enrichir les éléments finis poutres multifibres pour prise en compte de la distorsion de la section. Pour cela, des déplacements transversaux additionnels sont introduits. L’application du principe des puissances virtuelles sur le champ de vitesse virtuel associé permet de projeter les équations d’équilibre de l’élément et ainsi d’obtenir l’équation d’équilibre classique de l’élément mais aussi l’équilibre de la section. Cette dernière permet donc de tenir compte de l’effet des armatures transversales et de calculer correctement les contraintes latérales appliquées à chaque fibre de béton. En outre, afin de pouvoir reproduire l’effet de confinement des fibres de béton par les cadres, une loi de comportement dilatante doit être attribuée au béton. Dans ce contexte, la loi de comportement du µ modèle a été choisie. Celle-ci est dépourvue du comportement dilatant. Pour cette raison, une méthode d’introduction de la dilatance au niveau du coefficient de poisson est présentée dans ce mémoire. Les éléments poutres multifibres enrichis 2D et 3D sont formulés en déplacement et sont basés sur le modèle poutre de Caillerie [CAI 15] avec des fonctions de formes d’ordre supérieur. La pertinence de ces deux approches est finalement démontrée en confrontant la réponse du modèle numérique à différents résultats expérimentaux de la littérature. / In order to determine the seismic vulnerability of reinforced concrete structures, effective and sufficiently accurate numerical methods are required. Two-dimensional or three-dimensional finite element methods, widely used, provide reliable results. However, these types of methods involve a large number of degrees of freedom and robust 3D behavioral laws for concrete and steel to accurately capture the non-linearities in slender reinforced concrete elements. Another more practical method, in the field of structural engineering, is the use of multifiber beam elements.By using multifiber beam elements, the structure can be discretized with linear elements that carry a section discretized in the transversal direction based on the kinematic assumption of Euler Bernoulli or Timoshenko. The discretization of the section makes it possible to simply use nonlinear behavior laws and to model composite sections such as reinforced concrete. Nevertheless, there are limitations to this kind of model. Therefore, several researches have been conducted in the past few years to enhance the kinematics of the beam elements in order to correctly reproduce the shearing effects, especially in the case of short beams where the latter effect is not negligible. Several approaches have been developed in this field, as the one proposed by [VEC 88] adequate for two-dimensional case studies but doesn’t reproduce the torsional effect, the approach presented by [LEC 12], but whose model can not be applied to reinforced concrete elements, and the formulation proposed by [MOH 10] which is suitable for reinforced concrete applications but works only in 2D. More recently ([CAP 16b]; [CAP 16a]) have developed an enhanced multifiber beam model adapted to reinforced concrete elements and takes into account the warping of the section. The combination of this beam element with a concrete behavior model such as the µ model [MAZ 13], provides robust results with interesting computational speed. However, as shown by some experimental tests [CUS 95], the amount of transverse reinforcement triggers significantly the behavior of the beam elements, especially under cyclic loading . In the previous works, these reinforcements are neglected or considered in an approximative manner.Based on the work of [LEC 12] and [CAP 16a], this thesis aims to model the effect of transversal reinforcement. The approach proposed herein is to enhance the multifiber beam elements in order to take into account the distortion of the section. For this purpose, additional transverse displacements are introduced. The application of the principle of virtual powers on the field of associated virtual velocity leads to project the equilibrium equations of the element and thus to obtain the classical equilibrium equation of the element as well as the equilibrium of the section. The latter one allows to take into account the effect of the transverse reinforcements and to correctly calculate the lateral stresses applied to each concrete fiber. Moreover, in order to be able to reproduce the confinement effect due to the presence of stirrups, a dilatant constitutive law has to be attributed to the concrete fibers at the section level. In this context, the Mu model has been chosen even though it’s not a dilatant model. For this reason, a method of introducing dilatancy at the level of the Poisson’s coefficient is presented in this work. The 2D and 3D enhanced multifiber displacement beam models are formulated based on the Caillerie beam element [CAI 15] with higher order interpolation functions. The performance of these two approaches is also demonstrated by comparing the numerical model response to different experimental results of the literature.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographic references. / by Craig G. Prohazka. / M.S.

Electromagnetic launchers are currently being developed for their use as military weapons. These devices launch a projectile to extremely high speeds using very large electric currents. One obstacle facing the development of electromagnetic launchers is damage to the rails and armature during launch. The damage occurs due to current arcing in the armature-rail interface and is denoted as a transition. One solution is to use a lubricant injection system contained inside the armature to provide a conductive lubricant to the interface. The lubricant will ensure good electrical contact, prevent solid-solid contact, and cool the interface to prevent a launch from transitioning. Various different armature designs are currently under development. Each design must be analyzed through armature-rail interface modeling in order to predict the physical behavior and identify causes of transitions. There have been many studies on the physical behavior of sliding contacts. Some of which are directly applied to electromagnetic launch. In particular the magneto-elastothermohydrodynamic model is the most comprehensive model found for use in simulating electromagnetic launch. It includes calculation of the electromagnetic field, elastic deformation of the armature, calculation of the armature temperature history, and a hydrodynamic study of the lubricant both in the injection system and the armature-rail interface. The magneto-elastothermohydrodynamic model has been applied to only one armature design with limited success due to the assumptions used. The magneto-elastothermohydrodynamic model is applied to six different armature designs each requiring modifications to be made in order to predict the distinct behavior of each launcher. Modifications to the model include consideration of turbulent flow in the injection conduit, unique injection configurations, dry-out of the armature-rail interface, two dimensional pressure fields, and analyses of cylindrical bore launcher designs. The results show the model is effective in predicting when a transition will occur and what physical event leads to a transition when compared to experimental launch data. Additionally, experimental observations are used to affirm the simulation of other physical characteristics. It is found by the simulation that the base case armature is successful in preventing a transition of the shot, which is consistent with the experimental results. The simulation of NRL shot 223 reveals that such a small amount of lubricant is supplied by the reservoirs that the armature-rail interface partially dries out making a transition likely at a time of 4.7 ms; agreeing with the experimentally observed transition at a time of 4.5 ms. It is determined that the transition of NRL shot 406 is not due to a lack of lubricant inside the interface and that the amount of lubricant which leaks from the joint is negligible. IAP shot 7 did not transition in the experiment, however, after a time of about 3.5 ms the muzzle voltage began to rise. The simulation presents a possible explanation, showing that the armature-rail interface is beginning to empty out after 4.2 ms. The simulation of the GTL-2-4C armature shows that the experimentally observed transition is caused by the reservoirs emptying out at about 2.1 ms. The exploratory simulation of a modified GTL-2-4C armature determines that the absence of the slit in the armature trailing edges will not prevent the transition nor extend the successful portion of the shot.

The objective of this work has been to investigate the applicability of the gas gun to study the armature-rail interface wear characteristics relevant to rail gun operations. The approach involved developing constitutive models for armature materials (aluminum 6061) as well as oxygen-free high-thermal conductivity copper as the rail material. Taylor rod-on-anvil impact experiments were performed to validate the accuracy of constitutive strength models by correlating predictions of dynamic simulations in ANSYS AUTODYN with experimental observations. An optical comparator was used to discretize the cross sectional deformation profile of each rod-shaped sample. Parameters of the Johnson-Cook strength model were adjusted for each material to match deformation profiles obtained from simulations with profiles obtained from impact experiments. The fitted Johnson-Cook model parameters for each material were able to give overall deformed length and diameter values within 2% of the experimentally observed data. Additional simulations were then used with the validated strength model parameters to design the geometry involving cylindrical rods of armature material accelerated through a concentric cylindrical extrusion die made of copper, to emulate the interface wear effects produced in a rail gun operation. Experiments were conducted using this geometry and employing both the 7.62mm and 80mm diameter gas guns. Microstructural analysis was conducted on interfaces of the recovered samples from both designs. Hardness measurements were also performed along the interface layer to evaluate the structure formation due to solid-state wear or melt formation. The stress and strain conditions resulting in the observed microstructural effects were correlated with predictions from numerical simulations performed using the validated material models. The overall results illustrate that the stress-strain conditions produced during acceleration of Al through hollow concentric copper extrusion die, result in interface deformation and wear characteristics that are influenced by velocity. At velocities (less than 800m/s), interface wear leads to formation of layer dominated by solid-state alloying of Cu and Al, while higher velocities produce a melted and re-solidified aluminum layer. Hence, use of different armature (Al-based) and rail (Cu-based) materials can be evaluated with the gas-gun set-up employed in the current work to study the effects of interface wear ranging from formation melt layer to solid-state alloying as a function of material properties and velocity.

In electromagnetic launcher (EML) systems, the behavior of the materials and forces at the armature-rail interface involves fluid mechanics, electromagnetics, thermal effects, contact mechanics and deformation mechanics. These factors must interact successfully in order for a launch to be successful. A lubricant film either deposited on the rails prior to launch or injected from the armature during launch has been suggested as a means of improving the electrical conductivity of the rail-armature interface and of avoiding the occurrence of arcing. The fluid pressure generated by such film, together with the magnetic force, the contact force and the uneven temperature field in the armature, deforms the armature and changes the interface gap shape. An analytical model to study the interfacial behavior under these influences is necessary in order to predict the performance of a potential EML design and to provide optimization information. Studies of this interfacial behavior have been done by a number of researchers. However, many critical factors were not included, such as surface roughness, cavitation, injection, magnetic lateral force, interface deformation and thermal effects. The three models presented in this study investigate the influence of those factors on the EML interface problem. The magneto-hydrodynamic (MHD) model establishes a description of the lubrication process under electromagnetic stress but neglects interface deformation. The magneto-elastohydrodynamic (MEHD) model extends the MHD model by considering the lateral magnetic force, interface contact force and elastic deformation. Finally, the magneto-elastothermohydrodynamic (METHD) model adds the thermal effects to the deformation analysis. A coupled analysis of the interface behavior with the METHD model is developed and the history of a typical launch is studied. Detailed injection, lubrication and launch processes are revealed and the performance is predicted. A failed launch is simulated and the cause of failure is identified to be debris left on the rails. Several operation and design parameters, such as rail surface profile, electric current pattern, reservoir load, lubrication length, pocket size and geometry, injection conduit diameter, are analyzed and a recommended injection design procedure is developed. A scaling study is performed by doubling the dimensions to predict the scaling effects. In the end, the base case configuration and scaled configuration are optimized using the technique developed in this study.

It is estimated that nearly two in three people will live in urban areas by 2045. The city is increasingly seen as a place of opportunity. It has become a receptacle for new social, cultural and economic strata. The urban environment is converted and mutated by everyday public performances. This condition becomes evident when the street is inhabited as a space that connects the workplace, the home and institutions. The built wall often attracts and establishes these new activities.It is here that conventional architectural typologies are challenged. This dissertation explores the notion of the wall in an attempt to reconfigure the sidewalk. A conceptual network of interfaces that contain infrastructure, public services and urban armatures is proposed. Within this context, it is argued that architecture should support these everyday performances as well as define a new spatial identity, within the urban environment. / Dissertation MArch(Prof)--University of Pretoria, 2012. / Architecture / MArch(Prof) / Unrestricted

Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1979 / Includes bibliographical references. / by Kohji Tanaka. / M.S. / M.S. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science