Este trabalho objetivou o estudo dos edifícios de múltiplos andares constituídos por elementos mistos aço-concreto, com enfoque acadêmico, porém abordando aspectos e recomendações normativas diretamente aplicadas na prática corrente da engenharia estrutural. A revisão bibliográfica foi realizada com base em estudos acadêmicos e normativos além do estudo de um edifício exemplo constituído por elementos mistos. Os elementos mistos lajes, vigas e pilares foram abordados inicialmente de forma isolada, com base nas recomendações normativas, sendo que ao final os elementos foram interligados, apresentando ao leitor os principais aspectos teóricos e normativos para o dimensionamento de um edifício completo constituído de elementos estruturais mistos. / This study aims the multiple storey buildings formed by composite elements steel-concrete, with academic emphasis, however approaching standard recommendations and aspects directly applied to the structural engineering. A bibliographic review based on academic and standard studies was made, besides the design of an example building formed by composite elements. The composite elements: slabs, beams and columns were firstly approached based on standard aspects, and in the end, the elements were interconnected and presented to the reader the main theoretical and standard aspects to the design of a complete building formed by composite structural elements.

Largamente utilizadas nas obras de engenharia civil, as vigas mistas aço-concreto surgem como conseqüência natural da utilização de vigas de aço sob lajes de concreto, proporcionando um melhor aproveitamento das características de cada material constituinte. Para que se comporte como um elemento misto, é necessário haver um trabalho conjunto entre laje e viga, razão pela qual são utilizados elementos metálicos denominados conectores de cisalhamento, que visam restringir o escorregamento longitudinal e o descolamento vertical na interface. Tendo em vista os aspectos mencionados, são apresentados neste trabalho modelos numéricos tridimensionais de vigas mistas com vistas a simular o seu comportamento estrutural, principalmente no referente à interface entre viga de aço e laje de concreto. Os modelos são constituídos por vigas mistas simplesmente apoiadas com laje de faces planas e conectores de cisalhamento do tipo pino com cabeça. As simulações foram realizadas por meio do código de cálculo ANSYS versão 8.0, que tem como base o método dos elementos finitos. Os resultados obtidos foram comparados com valores experimentais, extraídos de trabalhos apresentados por outros pesquisadores / Widely used in civil engineering frameworks, steel-concrete composite beams appear as consequence of the use of steel beams with concrete slab, providing better management of each constituent material properties. To act as a composite element, it is necessary that the slab and the beam work together, aspect obtained by using metallic elements called shear connectors, that restrict the longitudinal slipping and the uplifting between steel beam and concrete slab. In this sense, this work presents three-dimensional numerical models of steel-concrete composite beams in order to simulate its structural behavior with emphasis, in particular, at the interface between steel beam and concrete slab. The numerical models are constituted of simply supported composite beams with plain faces slab and stud bolt shear connectors. The simulations had been carried out by means of the code ANSYS version 8.0, based on finite elements method. The results had been compared with experimental values, extracted of works presented by others researchers

Largamente utilizadas nas obras de engenharia civil, as vigas mistas aço-concreto surgem como conseqüência natural da utilização de vigas de aço sob lajes de concreto, proporcionando um melhor aproveitamento das características de cada material constituinte. Para que se comporte como um elemento misto, é necessário haver um trabalho conjunto entre laje e viga, razão pela qual são utilizados elementos metálicos denominados conectores de cisalhamento, que visam restringir o escorregamento longitudinal e o descolamento vertical na interface. Tendo em vista os aspectos mencionados, são apresentados neste trabalho modelos numéricos tridimensionais de vigas mistas com vistas a simular o seu comportamento estrutural, principalmente no referente à interface entre viga de aço e laje de concreto. Os modelos são constituídos por vigas mistas simplesmente apoiadas com laje de faces planas e conectores de cisalhamento do tipo pino com cabeça. As simulações foram realizadas por meio do código de cálculo ANSYS versão 8.0, que tem como base o método dos elementos finitos. Os resultados obtidos foram comparados com valores experimentais, extraídos de trabalhos apresentados por outros pesquisadores / Widely used in civil engineering frameworks, steel-concrete composite beams appear as consequence of the use of steel beams with concrete slab, providing better management of each constituent material properties. To act as a composite element, it is necessary that the slab and the beam work together, aspect obtained by using metallic elements called shear connectors, that restrict the longitudinal slipping and the uplifting between steel beam and concrete slab. In this sense, this work presents three-dimensional numerical models of steel-concrete composite beams in order to simulate its structural behavior with emphasis, in particular, at the interface between steel beam and concrete slab. The numerical models are constituted of simply supported composite beams with plain faces slab and stud bolt shear connectors. The simulations had been carried out by means of the code ANSYS version 8.0, based on finite elements method. The results had been compared with experimental values, extracted of works presented by others researchers

This master thesis contents alternative design of three spans single-railed steel bridge and its main bearing structures. The bridge is located in km 19,459 on the track Děčín - Oldřichov. Crossing barrier is highway D8. The span is 28,38 m + 41,28 m + 28,38 m. The main bearing structure consists of solid steel beams with variable height of 2,3 m ~ 3,8 m, which are in the axial distance of 6 meters and reinforced with lengthwise and transverse stiffeners. The lower bridge deck with a continuous ballast bed consists of reinforced concrete bath, which is coupled with steel cross beams. All elements of the structure are made out of steel S 355. For design of the following standards have been used: ČSN EN 1991-2, ČSN EN 1993, ČSN EN 1994 – 2.

Une des causes majeures responsables de la perte de performance des ouvrages en béton armé (fissuration excessive, perte de capacité portante) peut être imputée à la corrosion des armatures présentes dans les éléments structuraux. Ce phénomène est susceptible de se développer soit par carbonatation, soit par pénétration des ions chlorures par le béton d'enrobage. C'est alors que des produits de corrosion apparaissent et génèrent des contraintes de traction qui, dès dépassement de la résistance en traction, favorisent l'apparition de fissures. D'un point de vue pratique, dès que les premières fissures sont remarquées à la surface du béton, la corrosion a généralement atteint un stade avancée et des actions de maintenance doivent être envisagées. Cela entraînent d'importants coûts évitables si une prédiction satisfaisante avait pu être réalisée. Cette étude vise à apporter des éléments de réponse à cette problématique. Deux objectifs essentiels sont considérés dans ces travaux de thèse : le premier consiste à proposer des lois de comportement robuste et satisfaisantes permettant de bien décrire le comportement des éléments de structure existants et le second vise à introduire une méthode probabiliste permettant d'actuali ser les paramètres des deux modèles sur la base de l'information disponible sur le terrain. Un cadre constitutif générique couplant élasticité, endommagement isotrope et glissement interne, thermodynamiquement admissible, est pour cela développé. Cette classe de modèles est particularisée au cas de l'interface acier/béton en présence de corrosion et au cas du béton. Ces dernières peuvent être utilisées non seulement sous chargement monotone mais aussi sous chargement cyclique. Les lois proposées permettent de prendre en compte les effets hystérétiques, les déformations permanentes et l'effet unilatéral. En outre, ces dernières ont été validées sur différents cas tests. Des versions multifibres des lois précédemment mentionnées ont également été développées pour offrir à l'ingénieur des modèles simplifiés. Une prise en compte du caractère imparfait de l'interface acier/béton au sein du formalisme multifibre est notamment considérée. L'étape d'identification des paramètres mat ériaux n'est pas toujours aisée à réaliser en raison d'une part des incertitudes qui entachent ces derniers et, d'autre part, de la méconnaissance des mécanismes locaux. Ainsi, une méthodologie probabiliste complète permettant d'actualiser les paramètres d'entrée sur la base d'observations extérieures est proposée. Elle s'appuie sur une utilisation conjointe des réseaux bayésiens et de la théorie de la fiabilité. Elle permet ainsi de réduire l'écart entre la prédiction numérique et les mesures réalisées sur le terrain. Ce travail de thèse devrait contribuer à fournir aux gestionnaires d'ouvrage des outils d'aide à la décision leur permettant de mieux gérer leurs ouvrages en béton armé / A major source of a noticeable loss of performance (excessive cracking, loss of carrying load capacity) can be attributed to the corrosion phenomena induced either by carbonation or by chloride ions ingress. The corrosion products being expansive, tensile stresses are generated and usually lead to the cover concrete cracking when tensile strength is exceeded. From a practical point of view, when first observable signs of degradation are noticed on site, it is generally too late and maintenance actions have to be made. This results in important expenses that could have been avoided if a satisfying prediction had been made. This thesis aims to propose some answers to that problem. Two main objectives have been handled. The first one consists in formulating reliable constitutive models for a better understanding of the mechanical behaviour of existing concrete structures. The second objective aims to develop a probabilistic approach for updating t he mechanical model according to experimental information available on site. A general constitutive framework, thermodynamically admissible, has been proposed coupling elasticity, isotropic damage and internal sliding. This general framework has been declined in two specific constitutive models, on one hand for modelling the steel/concrete interface including corrosion and, on the other hand for modelling the concrete behaviour. Both models are validated on several structural cases. They can be used for monotonic and cyclic loadings. Besides, they account for non linear hysteretic effects, quasi unilateral effect, permanent strains, etc. Simplified versions of the proposed constitutive models are also proposed for engineering purposes within the framework of the multifiber beams theory. In the case of the steel/concrete interface, although a Timoshenko based kinematic is assumed, a non-perfect interface between steel and concrete can be considered locally. The material para meter identification is not always straightforward. Therefore, the use of robust updating methods can improve the accuracy of mechanical models. A complete probabilistic approach based on Bayesian Networks has been proposed. It allows not only considering the uncertainties related to mechanical parameters but also reducing the gap between experimental measurements and numerical predictions. This study provides to stakeholders pertinent decision tools for predicting the structural behaviour of degraded reinforced concrete structures

Les structures en béton armé sont amenées à répondre à différentes exigences pouvant dépasser la simple résistance mécanique. Pendant le processus de fissuration, les contraintes dans le béton armé sont progressivement redistribuées entre l’acier et le béton via l’interface entre ces deux matériaux. Cette redistribution de contraintes a un impact direct sur l’état de fissuration final et doit donc être prise en compte dans la modélisation. Il existe différents modèles numériques capables de représenter les effets de la liaison acier-béton. Cependant, leur usage est, pour l’instant, incompatible avec les applications concernant les structures de grandes dimensions (difficultés de maillage, coût de calcul…). Dans ce cadre d’application, l’hypothèse de liaison parfaite entre l’acier et le béton (déplacement identique) est donc toujours utilisée. On se propose ici de développer un nouveau modèle éléments finis de liaison acier-béton qui soit à la fois représentatif des phénomènes physiques se produisant à l’interface entre les deux matériaux et compatible avec les contraintes de modélisation des structures de grandes dimensions. Ce travail de thèse se découpe en trois grandes parties : - le développement d’un modèle élément fini de liaison acier-béton adapté aux contraintes de modélisation des structures de grandes dimensions. Ce modèle numérique permet ainsi de tenir compte des interactions mécaniques entre le béton et les armatures d’acier représentées à l’aide d’éléments barres. - la caractérisation du comportement de la liaison acier-béton. Un modèle de loi d’adhérence (évolution de la contrainte d’adhérence en fonction du glissement) basé sur des observations expérimentales (campagne expérimentale de pull-out menée au cours de la thèse et données bibliographiques) est proposé. Il permet en particulier de différencier le cas d’une rupture par arrachement, d’une rupture par éclatement en tenant compte des caractéristiques matériaux et géométriques de la structure. - l’application du modèle proposé à un élément structurel (poutre). Un essai de poutre en flexion quatre points visant à caractériser l’évolution de la fissuration (évolution de l’ouverture de fissure mesurée à l’aide de la technique de corrélation d’images notamment) a ainsi été proposé. Ces résultats ont ensuite été comparés à ceux de simulations numériques tenant compte de la liaison acier-béton d’une part ou de l’hypothèse de liaison parfaite d’autre part. Les deux modélisations donnent une bonne approximation du comportement extérieur de la structure (comportement global et ouvertures de fissure des surfaces extérieures de la poutre). Le modèle de liaison acier-béton apporte cependant une meilleure caractérisation de la phase de fissuration active (apparition des fissures) et modifie plus particulièrement le comportement local de la structure à proximité directe des armatures (limitant le développement de l’endommagement du béton le long des renforts). / Reinforced concrete structures may have to fulfill functions that go beyond their simple mechanical resistance. During the cracking process, stresses are progressively transferred from steel to concrete through the steel-concrete interface. This stress transfer has a direct impact on the crack properties. Taking into account these effects seems thus essential to predict correctly the cracking of reinforced concrete structures. Different models exist to represent the steel-concrete bond behavior. However, these models are rarely compatible with large scale simulations (meshing difficulties, heavy computational cost…). To overcome these difficulties, a perfect relation between steel and concrete (same displacements) is generally considered for structural applications. In this contribution, a new finite element approach is proposed to represent the steel-concrete bond effects in a context adapted for large scale simulations. This thesis is divided in three parts: - the development of a finite element steel-concrete bond model adapted for large scale structural applications . This model takes into account mechanical interactions between concrete and steel reinforcement represented by truss elements. - the characterization of the steel-concrete bond behavior. A model for the bond stress-slip law based on experimental observations (experimental campaign on pull-out test carried out during the thesis and data of literature) is proposed. This model differentiates the case of a pull-out failure and of splitting failure and takes into account the material properties and the geometric characteristics of the structure. - an application of the proposed model on a structural element (beam). A four point bending beam is experimentally tested. This test aims to characterize the crack evolution (in particular the crack opening using the image correlation technique). Experimental results are then compared with numerical simulations taking into account the bond–slip effect between steel and concrete or considering the perfect relation hypothesis. The two simulations give a good approximation of the external behavior of the structure (global behavior and crack opening on the external face of the beam). Nevertheless, the bond model improves the cracking description during the active cracking phase (beginning of crack apparition) and influences the local behavior of the structure especially near the steel bars (avoiding the propagation of the damage of concrete along the steel reinforcement).

Depuis plusieurs années, la société MATIERE développe un nouveau type de renforcement des structures en béton reposant sur l'utilisation d'aciers plats crantés en substitution des aciers ronds à haute adhérence habituellement utilisés. Ce travail entre dans le cadre du programme de Recherche - Développement des techniques couvertes par les brevets de M. Marcel MATIERE. L'intérêt de ces nouveaux aciers plats crantés réside principalement dans leur géométrie qui permet d'envisager de nouvelles dispositions constructives associées à un gain sur l'épaisseur de béton, notamment au niveau de l'enrobage. Ces aciers sont principalement destinés aux éléments de type dalle ou aux voiles minces où ils permettront de réaliser les économies de béton les plus significatives. Cependant, aucune norme ou règlement ne prend en compte, à ce jour, ces nouveaux aciers. Une étude scientifique validée, principalement basée sur la modélisation numérique, s'est avérée nécessaire pour d'une part modéliser et comprendre l'interaction entre l'acier plat et le béton et, d'autre part, pour justifier que les méthodes de calcul traditionnelles restent applicables à ce genre de renforcement. Dans le cadre de la problématique de la fissuration, une stratégie de modélisation reposant sur une approche probabiliste multi-échelles a été développée. Cette approche multi-échelles ne consiste pas à développer une modélisation qui inclut, dans son formalisme, toutes les échelles, depuis l'échelle très locale jusqu'à l'échelle globale (une structure complète), mais à développer une panoplie de modélisations qui apportent des informations pertinences à l'échelle d'analyse choisie. Quelle que soit l'échelle considérée, la modélisation est succeptible de donner des informations sur l'ouverture et l'espacement de fissures. L'aspect probabiliste est essentiellement lié à l'hétérogénéité du matériau béton. Les modèles développés permettent aussi de tenir compte des effets d'échelle, propres aux matériaux hétérogènes, qui jouent un rôle prépondérant dans le comportement des structures en béton. Le travail de recherche a donc consisté à développer des outils de modélisation du comportement d'interface en parfaite cohérence avec l'échelle de modélisation des phénomènes envisagés, notamment au regard des processus de fissuration des structures renforcées par aciers plats. La démarche scientifique s'est appuyée sur une identification des paramètres de la modélisation par analyse inverse effectuée sur la base de résultats d'essais expérimentaux réalisés sur de grands tirants en béton armé par aciers plats. Les outils de modélisation ont ensuite été validés sur des modélisations du comportement en flexion de poutres-dalles de grandes dimensions comparées à des résultats d'essais expérimentaux. L'ensemble des essais expérimentaux, nécessaires à cette étude, ont été réalisés par Polytech' Clermont à la demande de l'entreprise MATIERE / For several years, the MATIERE company has developed a new type of reinforcement based on the use of ribbed flat steel in substitution of high-adhesion round steel used for precast products. This work is a part of the Technological Research and Development program implemented in the frame of Marcel MATIERE patents. The interest of these new ribbed carbon flat steel lies in their geometry that allows to consider a new structural disposition associated with a gain on the thickness of concrete, particularly at the coating level. These steels are mainly used for thin elements where they will achieve the savings of the most significant concrete. However, no standard or regulation take into account in this time for these new steels. A scientific study validated, mainly based on numerical modeling, is so necessary, firstly, to model and understand the interaction between the flat steel and the concrete, and secondly, to justify the traditional calculation methods are applicable to such reinforcement. In this frame, a modeling strategy based on a probabilistic multiscale approach was developed. This multiscale approach is not to develop a model that includes, in its formalism, all modeling scales, from the very local to the global scale (complete structure), but to develop a panoply of models that provides the relevant informations on the scale of analysis chosen. Whatever the scale considered, the modeling can provide the information relative to the cracks opening and cracks spacing. The probabilistic aspect is mainly due to the heterogeneity of the concrete. The developed models can take into account the scale effects, specific heterogeneous materials, which play an important role in the behavior of concrete structures. The research was therefore to develop a modeling tools of the interface behaviour which is perfectly consistent with the scale modeling of phenomena considered, particularly with regard to the cracking process of structure reinforced by steel plates. The scientific approach was based on a parameters identification of the modeling by an inverse analysis performed on the results of experimental tests carried out on the tie-beam reinforced by flat steel. Modeling tools were then validated on the modeling of the beams-slabs in flection and compared to experimental results. All experimental tests for this study were made by Polytech Clermont Ferrand to the request of the MATIERE company

A presente pesquisa propõe analisar, avaliar e validar o uso de ensaios de aderência açoconcreto para estimativa da resistência à compressão axial do concreto in loco nas primeiras idades em canteiros de obras, como alternativa ao controle de qualidade tradicional. Alguns pesquisadores propuseram a utilização de um ensaio de aderência modificado, que denominaram Appropriate Pull-Out Test (APULOT), como uma adaptação do método pullout test (POT) tradicional, normalizado pela norma EN12504-3. Para viabilizar o uso do ensaio APULOT como ensaio que possa ser implementado na prática do controle tecnológico do concreto em canteiros de obras e seja representativo da resistência in loco é necessário definir um padrão para o mesmo. O presente trabalho desenvolveu um molde específico para o ensaio, analisou a influência do processo da cura nos resultados da tensão máxima de aderência, estudou como a medição da maturidade no concreto pôde auxiliar na determinação do momento certo para fazer o ensaio de arrancamento e comparou resultados dos ensaios feitos em corpos de prova para teste de aderência com ensaios de arrancamento de barras de aço em painéis de concreto. Para tanto foram feitos nove concretagens empregando diferentes tamanhos e configurações de corpos de prova, ensaios de arrancamento, extrações de testemunhos de painéis de concreto, ensaios à compressão simples e medições de maturidade dos concretos empregados. Também se realizaram registros de temperatura ambiente e velocidade do vento na vizinhança dos painéis, buscando estabelecer relações entre a maturidade e as condições ambientais do canteiro. Os ensaios descritos anteriormente realizaram-se às idades de 3, 5, 7 e 28 dias. Os resultados obtidos mostram que, sob condições padronizadas de ensaio, existe ótima correlação entre a tensão máxima de aderência e a resistência à compressão do concreto e por tanto o ensaio de aderência pode ser utilizado para fazer uma estimativa da resistência à compressão do concreto in loco nas primeiras idades. / This research aims to analyze, evaluate and validate the use of steel-concrete bond tests to estimate the axial compression strength of in situ concrete at early ages on construction sites, as alternative to conventional strength control tests. Some researchers have proposed the use of a modified bond test, named Appropriate Pull-Out Test (APULOT), as an adaptation of the traditional pull-out test method (POT) standardized by the EN12504-3. To implement the APULOT as a strength control procedure for concrete on construction site, standardization is needed. This study developed a specific mold for the test; analyzed the influence of curing process on the results of the maximum bond stress; studied how measuring the maturity in the concrete could help to determine when is the right time to make the pull-out test; compared results of tests made on cores for testing the bond and pull-out tests on steel bars in concrete panels. Therefore, it have been made nine concrete events, pull-out tests using different sizes and configurations of cylindrical concret specimen, pull-out tests and extraction of cores from concrete panels, compressive test and maturity measurements of specific employees. Also, temperature and wind speed records have been performed in the panel´s sourrundings, seeking to establish relationships between maturity and ambiental conditions on construction site. The tests described above were carried out at 3, 5, 7 and 28 days. The results show that, under standardized test conditions, a correlation between the maximum bond stress and the concrete compression strength exists, and therefore, bond test can be used to estimate the in situ compression strength of the concrete in the first ages.

Com a crescente utilização de vigas mistas de aço e concreto em obras civis e devido à insuficiência de estudos relativos ao seu comportamento estrutural, investigações aprofundadas são necessárias para suprir as carências e aperfeiçoar o tema. Um fenômeno familiar na literatura de estruturas mistas é a distribuição não uniforme de tensões ao longo da largura da laje de concreto, denominado shear lag na literatura inglesa. Na análise e projeto de estruturas compostas, deflexões, tensões e resistência são tipicamente obtidas utilizando-se o conceito de largura efetiva, na qual o efeito shear lag é contabilizado indiretamente, substituindo a largura real da laje, por uma largura apropriadamente reduzida. Sem dispor de análises numéricas exatas para o dimensionamento prático, é necessário que códigos normativos forneçam métodos simplificados para a avaliação da largura efetiva minimizando perdas de precisão. Diante disso, no presente trabalho, procedimentos numéricos para a avaliação da largura efetiva, encontrados na literatura técnica, foram estudados e implementados ao modelo matemático em elementos finitos disponível no CEMACOM/PPGEC/UFRGS, capaz de representar com confiabilidade estruturas mistas. Comprovando-se a eficácia do modelo numérico em captar o efeito do shear lag, a resposta de uma viga mista biengastada, representando um vão intermediário de uma ponte contínua, submetida a um carregamento em longo prazo, e considerando-se os fenômenos reológicos do concreto de fluência e retração, além do comportamento não-linear devido a fissuração, é obtida e comparada à fórmulas estipuladas nas principais normas de projeto e em metodologias desenvolvidas por pesquisadores. Falhas potenciais nos códigos de projeto atuais foram evidenciadas, necessitando-se de adicionais estudos paramétricos experimentais e numéricos para a comprovação dos resultados. / With the increasing use of steel-concrete composite beams in bridges and buildings more investigations related to this topic are necessary to fill the needs and improve the subject. A familiar phenomenon in the literature of composite structures is the non-uniform distribution of stresses along the width of the concrete slab, called shear lag. In the analysis and design of composite beams, deflections, stresses, and strengths are typically obtained by utilizing the concept of effective width, in which shear lag effects are accounted for indirectly, by replacing the actual slab width by an appropriately reduced width. Without having exact numerical analysis for design, it is necessary that the design codes provide simplified methods for evaluating this effective width, minimizing losses of accuracy. In this work, numerical procedures for the evaluation of effective width, found in the specialized literature, were studied and implemented in the mathematical finite element model available in CEMACOM/PPGEC/UFRGS. This computational code is capable of representing the behavior of steel-concrete composite beams and is capable of capturing the shear lag effect. The response of a single span composite beam with fixed ends, representing an intermediate span of a continuous girder bridge, subject to long-term loading, and considering both rheological phenomena of concrete, such as creep and shrinkage, besides the non-linear behavior due to cracking, is obtained and compared to the stipulated formulas in the main code provisions and in the developed methodologies by some researchers. Potential failures in the current design codes were evidenced, requiring additional experimental and numerical parametric studies to prove the results.

Σκοπός είναι η διερεύνηση της τεχνολογίας των χερσαίων (onshore) ανεμογεννητριών και συγκεκριμένα των πυλώνων των ανεμογεννητριών. Αν εξετάσουμε το αιολικό δυναμικό στις χερσαίες περιοχές της Ευρώπης, παρατηρούμε αμέσως τις τεράστιες δυνατότητες ανάπτυξης ανεμογεννητριών. Παρατηρούμε επίσης την πλεονεκτική θέση της χώρας μας που εμφανίζεται να διαθέτει στο Αιγαίο πέλαγος μια από τις πλουσιότερες, σε αιολικό δυναμικό, περιοχές της Ευρώπης. Για να έχουμε όμως μεγαλύτερη απόδοση στην ισχύ μιας ανεμογεννήτριας πρέπει να αυξήσουμε το ύψος της έτσι ώστε να εκμεταλλευτούμε τις υψηλότερες ταχύτητες ανέμου σε μεγαλύτερα ύψη. Αυτό με την σειρά του θα επιφέρει πιο μεγάλα φορτία και επομένως μεγαλύτερες καταπονήσεις (εντατικά μεγέθη) στην βάση του πυλώνα καθώς η ανεμογεννήτρια προσομοιώνεται με σύστημα προβόλου. Ως συνέπεια τούτου θα πρέπει να αυξήσουμε την αντοχή του πυλώνα είτε αυξάνοντας το πάχος του υλικού της διατομής (αποφεύγεται – απαιτούνται μεγάλα πάχη συνεπώς μεγάλα κόστη), είτε αυξάνοντας τη διάμετρο της διατομής (αποφεύγεται – περιορισμένο πλάτος οδικού δικτύου που αποτρέπει την μεταφορά τμημάτων του πυλώνα της ανεμογεννήτριας με μεγάλες διατομές), είτε αυξάνοντας την αντοχή του υλικού της διατομής (αντικείμενο διατριβής). Στην παρούσα διατριβή γίνεται μελέτη βελτιστοποίησης σχεδιασμού των πυλώνων των ανεμογεννητριών με σύμμικτη διατομή χάλυβα-σκυροδέματος η οποία οδηγεί σε σχετικά μικρά πάχη διατομών, μικρής διαμέτρου, μεγάλης επιθυμητής αντοχής και μειωμένου κόστους υλικά. Αρχικά γίνεται η ανάλυση διατομής με στόχο την βελτιστοποίηση - ελαχιστοποίηση του κόστους για δεδομένη αντίσταση και στη συνέχεια η ανάλυση επαναλαμβάνεται για την βελτιστοποίηση του κόστους για δεδομένη δυσκαμψία. Στη συνέχεια με τη βοήθεια του σχεδιαστικού αναλυτικού προγράμματος ANSYS θα γίνει η σχεδίαση του πυλώνα της ανεμογεννήτριας όπου θα εφαρμοστούν τα προβλεπόμενα φορτία. Κατόπιν αυτού του σχεδιασμού διεξάγουμε πείραμα στο εργαστήριο όπου προσομοιώνουμε την ανεμογεννήτρια ώστε να συγκρίνουμε τα πειραματικά αποτελέσματα με την αναλυτική διαδικασία στο πρόγραμμα ANSYS. Γίνεται παράθεση και σχολιασμός των αποτελεσμάτων ώστε να προκύψουν τα συμπεράσματά μας και τελικώς γίνονται προτάσεις για περαιτέρω έρευνα όσον αφορά τα υλικά της διατομής των πυλώνων καθώς και την καλύτερη αξιοποίηση της αιολικής ενέργειας. / The aim is to investigate the technology of land (onshore) wind turbines and specifically for the pillars of wind turbines. If we investigate the wind potential in inland areas of Europe, we see immediately the enormous growth potential of wind turbines. We also observe the vantage point of our country that appears to have the Aegean Sea, one of the richest in wind potential areas of Europe. In order to increase the power of a wind turbine we must increase its height so as to take advantage of higher wind speeds at higher altitudes. This leads to higher loads and thus higher stresses (section forces) at the base of the tower as the wind turbine system is simulated with the cantilever system. As a consequence we should increase the strength of the pillar by increasing the thickness of the section material (to be avoided - large thicknesses therefore high costs required) or by increasing the diameter of the cross section (to be avoided - narrow road network that prevents transfer of the turbine pillar parts with large cross-sections), or by increasing the strength of the section’s material (subject of thesis). This thesis deal with the Design Optimization of Composite Cross Section Steel – Concrete Wind Turbine Towers which leads to relatively low thickness cross-sections, with small diameters, desirable high strength and reduced cost of materials. Initially we conduct sectional analysis in order to optimize - minimize the cost for a given resistance, and then the analysis is repeated for cost optimization for a given stiffness. Then we develop equations which correlate the moment, the stiffness and the cost of the wind turbine tower with the thicknesses of the materials (steel – concrete) which the cross section is composed of. Consequently we plot the equations that give the materials’ dimensions ranges when both the moment and stiffness is modified. Also we can understand how all this procedure affects the whole cost of the cross section. Then we conduct analysis and design of the wind turbine pillar with the analytical program ANSYS according to the design loads. Afterwards, lab-scale tests are conducted in order to model the wind turbine behavior. The experimental results are compared to the analytical observations. Finally we display and comment the results of that research so as to draw conclusions regarding the pillar design and the efficient wind energy utilization and present suggestions to future research.