Understanding the complex dynamics that underpin the response of structures in the occurrence of earthquakes is of paramount importance in ensuring community resilience. The operational continuity of structures is influenced by the performance of nonstructural components, also known as secondary structures. Inherent vulnerability characteristics, nonlinearities and uncertainties in their properties or in the excitation pose challenges that render their response determination as a non-straightforward task. This dissertation settles in the context of mathematical modelling and response quantification of seismically driven secondary systems. The case of bilinear hysteretic, rigid-plastic and free-standing rocking oscillators is first considered, as a representative class of secondary systems of distinct behaviour excited at a single point in the primary structure. The equations governing their full dynamic interaction with linear primary oscillators are derived with the purpose of assessing the appropriateness of simplified analysis methods where the secondary-primary feedback action is not accounted for. Analyses carried out in presence of pulse-type excitation have shown that the cascade approximation can be considered satisfactory for bilinear systems provided the secondary-primary mass ratio is adequately low and the system does not approach resonance. For the case of sliding and rocking systems, much lighter secondary systems need to be considered if the cascade analysis is to be adopted, with the validity of the approximation dictated by the selection of the input parameters. Based on the premise that decoupling is permitted, new analytical solutions are derived for the pulse driven nonlinear oscillators considered, conveniently expressing the seismic response as a function of the input parameters and the relative effects are quantified. An efficient numerical scheme for a general-type of excitation is also presented and is used in conjunction with an existing nonstationary stochastic far-field ground motion model to determine the seismic response spectra for the secondary oscillators at given site and earthquake characteristics. Prompted by the presence of uncertainty in the primary structure, and in line with the classical modal analysis, a novel approach for directly characterising uncertainty in the modal shapes, frequencies and damping ratios of the primary structure is proposed. A procedure is then presented for the identification of the model parameters and demonstrated with an application to linear steel frames with uncertain semi-rigid connections. It is shown that the proposed approach reduces the number of the uncertain input parameters and the size of the dynamic problem, and is thus particularly appealing for the stochastic assessment of existing structural systems, where partial modal information is available e.g. through operational modal analysis testing. Through a numerical example, the relative effect of stochasticity in a bi-directional seismic input is found to have a more prominent role on the nonlinear response of secondary oscillators when compared to the uncertainty in the primary structure. Further extending the analyses to the case of multi-attached linear secondary systems driven by deterministic seismic excitation, a convenient variant of the component-mode synthesis method is presented, whereby the primary-secondary dynamic interaction is accounted for through the modes of vibration of the two components. The problem of selecting the vibrational modes to be retained in analysis is then addressed for the case of secondary structures, which may possess numerous low frequency modes with negligible mass, and a modal correction method is adopted in view of the application for seismic analysis. The influence of various approaches to build the viscous damping matrix of the primary-secondary assembly is also investigated, and a novel technique based on modal damping superposition is proposed. Numerical applications are demonstrated through a piping secondary system multi-connected on a primary frame exhibiting various irregularities in plan and elevation, as well as a multi-connected flexible secondary system. Overall, this PhD thesis delivers new insights into the determination and understanding of the response of seismically driven secondary structures. The research is deemed to be of academic and professional engineering interest spanning several areas including seismic engineering, extreme events, structural health monitoring, risk mitigation and reliability analysis.

[pt] Ao longo dos anos, a interação aço-concreto tem obtido um lugar de destaque do ponto de vista estrutural, ampliando a gama de soluções em concreto armado e aço, o que permite atender aos novos desafios arquitetônicos e às exigências que o mercado impõe. O objetivo do sistema misto é a combinação desses dois materiais, formando um único sistema estrutural em que a capacidade portante de cada elemento possa ser explorada ao máximo, tirando-se proveito da grande capacidade do concreto resistir a esforços de compressão, e de o aço, à tração. Essas características singulares de sistemas mistos aço-concreto conduzem a frequências naturais mais próximas da faixa de frequência de excitações associada às atividades humanas. Sendo assim, as considerações relacionadas ao projeto estrutural obrigam os engenheiros a fazer verificações quanto à resistência e à estabilidade de sistemas estruturais (estados limites últimos), mas os problemas relacionados ao estado limite de utilização desses sistemas devem ser analisados de forma mais cuidadosa. Embora o assunto de vibrações em lajes de edifícios induzidas por atividades humanas tem sido de continuado interesse a pesquisadores e a engenheiros ao longo dos últimos dois séculos (1828-2009), inexiste na literatura técnica, até onde o autor tem conhecimento, análise de correlações teórico-experimentais de vibrações de estruturas mistas aço-concreto sob ação de atividades humanas, na qual são consideradas a ortotropia, a interação parcial e as ligações semirrígidas. Com o objetivo de contribuir nessa direção, o presente trabalho investiga o efeito da interação aço-concreto sobre a resposta dinâmica de sistemas de pisos mistos. / [en] Over the years the steel-concrete interaction have been achieving excelent results, in terms of structural performance. This fact have enlarged the range of applications of concrete and steel structures enabling the development of efficient solutions that attend the demands claimed by the market and by increasinly daring architectures. The composite action main objective is to combine steel and concrete into single structural system where the optimum performance of the combined elements could be explored. The concrete is used to sustain compressive while the steel is better used when submitted to tension. These singular characteristics of the composite systems, on the other hand, lead to composite structural systems with natural frequencies close to the frequency associated to human induced loads. Usually the design of composite structures is focused on verifications related to ultimate limit states associated to strength and stability, but the problems related to serviceability limit states should also be carefully considered. Despite the fact that floor vibration induced by human activity has been extensively investigated in the past (1828-2009) there is still a lack of published information on theoretical-experimental correlations on the dynamic response of composite structures specially after considering effects releted to partial interaction, orthotropy and semi-rigid connections. The present study has the objective of contributing in the direction of better understand the effect of the steel-concrete interaction on the composite floor system dynamic response.

Advancement of micro-electro-mechanics and wireless communication have proliferated the deployment of large-scale wireless sensor networks. Due to cost, size and power constraints, at most a few sensor nodes can be equipped with a global positioning system; such nodes (whose positions can be accurately determined) are referred to as anchors. However, one can deter-mine the distance between two nearby sensors using some form of local communication. The problem of computing the positions of the non-anchor nodes from the inter-sensor distances and anchor positions is referred as sensor network localization (SNL). In this dissertation, our aim is to develop an accurate, efficient, and scalable localization algorithm, which can operate both in the presence and absence of anchors. It has been demon-strated in the literature that divide-and-conquer approaches can be used to localize large net-works without compromising the localization accuracy. The core idea with such approaches is to partition the network into overlapping subnetworks, localize each subnetwork using the available distances (and anchor positions), and finally register the subnetworks in a single coordinate system. In this regard, the contributions of this dissertation are as follows: We study the global registration problem and formulate a necessary “rigidity” condition for uniquely recovering the global sensor locations. In particular, we present a method for efficiently testing rigidity, and a heuristic for augmenting the partitioned network to enforce rigidity. We present a mechanism for partitioning the network into smaller subnetworks using cliques. Each clique is efficiently localized using multidimensional scaling. Finally, we use a recently proposed semidefinite program (SDP) to register the localized subnetworks. We develop a scalable ADMM solver for the SDP in question. We present simulation results on random and structured networks to demonstrate the pro-posed methods perform better than state-of-the-art methods in terms of run-time, accuracy, and scalability.

O presente trabalho tem por objetivo desenvolver uma formulação numérica baseada em Análise Isogeométrica para o estudo de problemas de interação fluido-estrutura (IFE) em aplicações envolvendo corpos rígidos submersos, onde escoamentos incompressíveis de fluidos Newtonianos com superfície livre são considerados. Propõe-se o emprego da Análise Isogeométrica por permitir a unificação entre os procedimentos de pré-processamento e análise, melhorando assim as condições de continuidade das funções de base empregadas tanto na discretização espacial do problema como na aproximação das variáveis do sistema de equações. O sistema de equações fundamentais do escoamento é formado pelas equações de Navier-Stokes e pela equação da conservação de massa, descrita segundo a hipótese de pseudo-compressibilidade, em uma formulação cinemática ALE (Arbitrary Lagrangean- Eulerian). A consideração da superfície livre no escoamento se dá tratando o fluido como um meio bifásico, através do método Level Set. O corpo rígido apresenta não linearidade na rotação e restrições representadas por vínculos elásticos e amortecedores viscosos, sendo a equação de equilíbrio dinâmico resolvida através do método de Newmark. O esquema de acoplamento sólido-fluido adotado é o particionado convencional, que impõe condições de compatibilidade cinemáticas e de equilíbrio sobre a interface sólido-fluido, analisando ambos os meios de maneira sequencial. A discretização das equações governantes é realizada através do esquema explícito de dois passos de Taylor-Galerkin, aplicado no contexto da Análise Isogeométrica. Por fim, são analisados alguns problemas da Dinâmica de Fluidos Computacional, de onde se concluiu que os resultados obtidos são bastante consistentes com os fenômenos envolvidos, com as ferramentas exclusivas da Análise Isogeométrica, como o refinamento k, melhorando a convergência dos resultados. Para escoamentos bifásicos, verificou-se que o método Level Set obteve resultados bastante promissores apresentando, entretanto, uma dissipação numérica excessiva. Propõe-se, para estudos futuros, a elaboração de esquemas numéricos que conservem melhor o volume da fase líquida do escoamento. / The present work aims to development of a numerical formulation based on Isogeometric Analysis for the study of Fluid-Structure Interaction problems in applications involving rigid bodies submerged, considering incompressible Newtonian flows with free surface. The use of the Isogeometric Analysis allows unification between the preprocessing and analysis steps, improving then the continuity of the base functions employed, both in the spatial discretization and approximation of the variables in the system of equations. The fundamental flow equations are formed by the Navier-Stokes and the mass conservation, described by de pseudo-compressibility hypothesis, in an ALE (Arbitrary Lagrangean-Eulerian) kinematic formulation. The free surface consideration of the flow is handled treating the fluid like a two- phase medium, using the Level Set method. The rigid body considers nonlinearity in rotation, and restrictions represented by elastic springs and viscous dampers, with the dynamic equilibrium equation being resolved using the Newmark’s method. The solid-fluid coupling scheme is the conventional partitioned, which imposes kinematics and equilibrium compatibility conditions on the solid-fluid interface, analyzing both mediums in a sequential manner. The governing equations are discretized using the explicit two step Taylor-Galerkin method, applied in an Isogeometric Analisys context. Finally, some Computational Fluid Dinamics problems are analysed, from which it was concluded that the results obtained are quite consistent with phenomena involved, with the unique tools of Isogeometric Analysis, such as k-refinement, improving the convergence of the results. For biphasic flows, it was verified that the Level Set method obtained very promising results, presenting, however, an excessive numerical dissipation. For future studies, it is proposed the elaboration of numerical schemes that better preserve the volume of the liquid phase of the flow.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A comunidade científica tem conhecimento de que uma das etapas mais relevantes no projeto de estruturas de aço e mistas, diz respeito a uma avaliação precisa sobre os modelos estruturais que representam o comportamento real das ligações viga-coluna. Este assunto tem sido objeto de vários trabalhos de pesquisa nas ultimas décadas. Na prática corrente do projeto de estruturas de aço, a grande maioria das ligações viga-coluna é representada por modelos flexíveis (rótulas) ou rígidos (engastes). Contudo, na maior parte dos casos práticos, essas ligações assumem um comportamento intermediário, ou seja, semi-rígido. Um outro ponto importante acerca do assunto diz respeito à avaliação da resposta dinâmica de estruturas de aço com a consideração pertinente do efeito das ligações, especialmente, no que tange as semi-rígidas, já que a maioria dos trabalhos de pesquisa concentra-se apenas no estudo da resposta estática dos modelos. Assim sendo, esta investigação apresenta uma contribuição inicial no que tange ao emprego de elementos que representem mais fielmente os efeitos das ligações estruturais na análise dinâmica de estruturas de aço, evidentemente, com a consideração do efeito de semi-rigidez dessas ligações. Desta forma, este trabalho de pesquisa propõe o uso de um modelo mecânico com elementos de mola rotacionais não-lineares, objetivando simular adequadamente o efeito das ligações viga-coluna especificamente em pórticos de aço. Inicialmente, foi feita uma calibração do modelo computacional desenvolvido, comparando os resultados obtidos mediante o uso do modelo de mola rotacional com os dados obtidos na literatura técnica sobre o assunto. Na seqüência, desenvolve-se uma analise paramétrica extensa, com a inclusão de todos os efeitos mencionados no parágrafo anterior, de forma a avaliar mais detalhadamente a resposta dinâmica dos pórticos de aço, deslocamentos e esforços, com base no estudo de um edifício residencial de quatro pavimentos. / The scientific community has realized that one of the most relevant stages in the design of steel and composite structures concerns to an accurate evaluation about the structural models that represent the actual behaviour of the beam-to-column connections. This issue has been the subject of many studies over the last decade. In the current design of steel structures, most of the beam-to-column connections are represented by pinned or rigid models. However, in most of the current cases, the connections have an intermediate behaviour between these two cases. Another important issue about the correct evaluation of the dynamic response of steel structures its about the consideration of the effects of the joints, especially of the semi-rigid joints, since most of the studies consider only a static analysis of the models. Therefore, this dissertation has proposed the use of a mechanical model of rotational springs with a nonlinear behaviour, objectifying a proper simulation of the beam-to-column effects in steel frames. The numeric results were obtained along the present study, and calibrated based on many computer models available on the literature. On the sequence, a large parametric analysis is developed, including all the effects mentioned before, objectifying evaluate more precisely the dynamic response of the steel frames (displacements and forces), based on the static and dynamic response of a four storey edifice.

Made available in DSpace on 2016-06-02T20:09:04Z (GMT). No. of bitstreams: 1 DissASS.pdf: 3030488 bytes, checksum: a4d23b016b1767d42942fdad295c0fe1 (MD5) Previous issue date: 2006-09-01 / Universidade Federal de Minas Gerais / The behaviour of reinforced concrete precast beams is strongly influenced by the flexural stiffness of its beam-column connections, wherein there is interdependence between the nonlinearity of the moment-curvature relationship along the beam and the non-linearity of the moment-rotation relationship of the beam-column connections. In most of the existing researches on semi-rigid connections in precast structures, the main focus lays on the characterization of the flexural stiffness by performing experimental tests on isolated models of beam-column connections instead of tests on sub-frames, comprising beam and connections. In this research an experimental procedure was developed, wherein different theoretical equations based on the fixity factor of the connections were combined, allowing the integration between the stiffness of the reinforced concrete beam with the flexural stiffness of the beam-column connections. Therefore, by using this procedure it was possible to evaluate the semi-rigid behaviour of the beam-column connection, highlighting the possibility of carrying out just one test for the precast beam with its connections. The analyses of the experimental results indicate that the studied connection was capable of absorbing around 53% of the elastic beam-end moment at the ULS, compared with the situation of a full restrained connector, implying the increase of 170% of the positive mid-span moment of the beam. This level of semi-rigid behaviour for the beam-column connection can affect the global stability of skeletal precast concrete structures with more than five storeys in height. For this reason, the present research shows the need for further studies with the purpose of enhancing the analysis and the design of precast concrete structures for multi-storey buildings. / O comportamento das vigas pré-moldadas de concreto armado é fortemente influenciado pela rigidez à flexão das ligações viga-pilar, existe uma interdependência entre a não linearidade da relação momento-curvatura ao longo da viga pré-moldada com a não linearidade da relação momento-rotação nas ligações viga-pilar. A maioria das investigações experimentais existentes sobre ligações semi-rígidas em estruturas pré-moldadas, tanto na literatura nacional quanto internacional, têm enfatizado seus estudos na caracterização da rigidez à flexão de maneira isolada, não realizando ensaios do comportamento conjunto das vigas pré-moldadas com as suas ligações. Desenvolve-se nesta pesquisa um procedimento experimental onde se procurou integrar diversos equacionamentos teóricos com base no fator de restrição aos giros na ligação, os quais permitiram integrar parâmetros de rigidez da ligação e da viga. Desta forma, com base nos resultados experimentais em um único ensaio de um modelo de viga com ligações viga-pilar, foi possível se estimar o engastamento parcial nas ligações viga-pilar. A partir dos resultados experimentais, a ligação viga-pilar foi capaz de absorver cerca de 53% dos momentos elásticos na extremidade da viga, havendo assim um acréscimo de 170% no momento positivo no centro da viga para a situação de projeto no ELU. Este engastamento parcial pode afetar sensivelmente a estabilidade global de estruturas pré-moldadas com mais de 5 pavimentos. Por esta razão, o presente estudo aponta para a necessidade de mais pesquisas nesta área, com o objetivo de possibilitar projetos mais adequados e seguros de estruturas pré-moldadas em esqueleto para múltiplos pavimentos.

Made available in DSpace on 2016-06-02T20:09:05Z (GMT). No. of bitstreams: 1 DissMNK.pdf: 4268420 bytes, checksum: 50c2feaa3b1252323d08d023d64588ae (MD5) Previous issue date: 2007-02-26 / Universidade Federal de Minas Gerais / The present research deals with the study of continuity in slab-beam-column connections in precast concrete structures, wherein an experimental investigation about the contribution of longitudinal reinforced bars, passing on the side of the column in the top of the slab, on the connector flexural stiffness. For this study, a beam-to-column connection was selected, comprising concrete corbel with dowel bars and continuity reinforced bars passing trough the column and fulfilling of grout in the interface of the connection. Two tests were carried out for the characterization of the moment-rotation relationship of two different connection prototypes, one with 100% of the continuity reinforced bars passing trough the column and another with 50% trough the column and 50% in the laterals. The experimental results indicate that bars passing on both sides of the column enhanced the moment-rotation relationship for the second prototype, being even more significant for the serviceability stage. However, rotations at the beginning of plasticization of the moment-rotation curve were close for the two prototypes. The results indicate that the transverse reinforcement between the slab and the beam was capable of mobilizing the external longitudinal bars at the same time of the internal longitudinal bars, passing through the column. Additionally, this reinforcement arrangement provided an increase of the cracking control within the connection zone at the end of the beam / No presente trabalho foi estuda a continuidade em ligações laje-viga-pilar em estruturas pré-moldadas de concreto com a realização de uma investigação experimental quanto à contribuição da parcela de armadura passante nas laterais do pilar na capa da laje, tanto para a rigidez à flexão quanto para o controle da fissuração. Para objeto de estudo, selecionou-se uma ligação viga-pilar com consolo de concreto e chumbador, com armadura de continuidade passante no pilar por meio de bainhas lisas preenchidas com graute. Foram realizados ensaios para a caracterização das ligações com dois modelos experimentais, sendo um com 100% da armadura de continuidade passando dentro do pilar e o segundo com 50% dentro do pilar e 50% nas laterais. Os resultados experimentais mostraram que as barras laterais ao pilar contribuíram para aumento da rigidez à flexão, principalmente para a fase de serviço, inferior à carga de projeto. Entretanto, as rotações relativas ao início da plastificação da relação momento-rotação foram próximas para os dois modelos. Acredita-se que o detalhamento empregado para armadura de costura entre a viga e a laje permitiu que as armaduras longitudinais dentro e fora do pilar fossem mobilizadas de forma conjunta, tanto na fase de serviço quanto para a fase de projeto, promovendo um controle efetivo da fissuração na região da ligação

Made available in DSpace on 2016-06-02T20:09:07Z (GMT). No. of bitstreams: 1 DissACJJ.pdf: 4431196 bytes, checksum: 0cd979c0d63cf2d4e62f5e4290affb0c (MD5) Previous issue date: 2007-08-30 / This research comprehends a study of the analysis procedures of the global stability in precast concrete structures, considering the effect of the semi-rigid connections. A Look over in the standards and directives of the precast structures project was necessary specifically on the procedures of global stability verification, recommended by the NBR 6118. Besides, it was looked to identify particular situations where the analysis of the precast concrete structures differentiates of the analysis of the structures cast in place. Such discussion is relevant at the moment of the publication of the new NBR 9062, where the effect of the behavior of the beam-to-column connections must be considered in the analysis of the global stability. In the carried through studies, the frame action proportionate by the bending moment resistant beam-to-column connections is a efficient method of bracing of the structure since that the interdependence of some factors is analyzed as the number of the floors, the stiffness and the cracking of columns and the beams and the fixity factor αR. Finally, examples of numerical application are presented with intention to guide the designer of precast concrete structures in the analysis of structures with semi-rigid connections. / Esta pesquisa compreende o estudo dos procedimentos de análise da estabilidade global em estruturas pré-moldadas considerando o efeito das ligações semi-rígidas. Foi realizada uma revisão dos critérios e diretrizes de projeto em estruturas pré-moldadas necessárias no procedimento de verificação da estabilidade global recomendada pela NBR 6118. Além disto, procurou-se identificar situações particulares em que a análise das estruturas pré-moldadas se diferencia da análise das estruturas moldadas no local. Tal discussão é relevante no momento da publicação da nova NBR-9062, onde o efeito do comportamento das ligações viga-pilar deve ser considerado na análise da estabilidade global. Nos estudos realizados, o efeito de pórtico proporcionado pelas ligações viga-pilar resistentes à flexão mostrou-se um método de contraventamento adequado desde que seja analisada a interdependência de vários fatores como o número de pavimentos, a rigidez e a fissuração de pilares e vigas e o fator de restrição à rotação αR. Finalmente, são apresentados exemplos de aplicação numérica com o intuito de orientar o projetista de estruturas pré-moldadas na análise de estruturas com ligações semi-rígidas.

Made available in DSpace on 2016-06-02T20:09:15Z (GMT). No. of bitstreams: 1 4134.pdf: 10682019 bytes, checksum: 08a3b53f3f78732a452841c76b25a524 (MD5) Previous issue date: 2012-02-13 / One of the main differences in the structures composed of prefabricated elements of the conventional structures (cast in situ) refers to the way of how structural elements are connected together. The operation of such links is essential to perform an accurate analysis of stability and removed from these buildings. A place where the connection is very important in verifying the structural behavior is among the cellular elements of the slab. In a conventional structure, usually made of solid slabs for floors, it is observed that the behavior of slabs have a great influence on the distribution of efforts arising from actions horizontal resistance between the porch and, consequently, the stability of the same. This phenomenon, defined as a rigid diaphragm, can also be found in precast buildings, with floors composed of hollow core slabs. In order to verify the necessity of including some details of connection between the slab elements (joints between the slabs and among other things) will be proposed in this paper the analysis of five structures with different characteristics, considering the different possibilities of bracing and disposal of prefabricated slabs in the floor. Consideration will be given the difference in the distribution efforts of the pavements, considering the application of shear walls and gateways, as well as the provision of slabs parallel and perpendicular to side action. The interference of the cover structure will also be analyzed in a number of examples. From a modeling specific to the floors of these buildings and different situations with different levels of horizontal actions, one can determine the stresses at specific points of the same, thus indicating the types of reinforcements to be willing to actually floors act as a diaphragm. Finally, we intend to discuss the organization of prefabricated elements interfere in the distribution of efforts on the pavement (joints between the slab elements), based on different amounts of reinforcing bars of each type of pavement structure will require. / Uma das principais diferenças das estruturas compostas por elementos pré-fabricados das estruturas convencionais (moldadas in loco) faz referência à maneira de como os elementos estruturais são ligados entre si. O modo de funcionamento de tais ligações é primordial para se realizar uma correta análise de estabilidade e deslocabilidade dessas edificações. Um local no qual a ligação se faz muito importante na verificação do comportamento estrutural é entre os elementos de laje alveolar. Em uma estrutura convencional, geralmente composta por pavimentos de lajes maciças, observa-se que as lajes têm um comportamento de grande influência na distribuição de esforços advindos de ações horizontais entre os pórticos resistentes e, conseqüentemente, na estabilidade da mesma. Esse fenômeno, definido como diafragma rígido, pode também estar presente em edificações pré-fabricadas, com pavimentos compostos por lajes alveolares. De modo a se verificar a necessidade de inserção de alguns detalhes de ligação entre os elementos de laje (juntas entre as lajes e entre outros elementos) serão propostos neste trabalho a análise de cinco estruturas com características distintas, considerando as diferentes possibilidades de elementos de contraventamento e disposição das lajes pré-fabricadas no piso. Será analisada a diferença na distribuição dos esforços nos pavimentos, considerando a aplicação de paredes de cisalhamento e pórticos, bem como a disposição de lajes paralelas e perpendicular a ação lateral. A interferência da capa estrutural também será analisada em um dos exemplos numéricos. A partir de uma modelagem específica para os pavimentos dessas diferentes edificações e situações, com diferentes níveis de ações horizontais, podem-se determinar os esforços em pontos específicos dos mesmos, indicando assim os tipos de reforços que deverão ser dispostos para que de fato os pavimentos funcionem como diafragma. Por fim, pretende-se discorrer sobre como a organização dos elementos pré-fabricados interfere na distribuição dos esforços no pavimento (juntas entre os elementos de laje), com base nas diferentes quantidades de armaduras de reforço do pavimento que cada tipo de estrutura exigirá.

Ce travail de thèse porte sur le développement d’une nouvelle génération de mousses polymères biosourcées capables de satisfaire la fonction d’âme alvéolaire et structurale de pièces automobiles. Les formulations époxy choisies comme base polymère reposent sur deux différents prépolymères époxy, l’huile de lin époxydée (ELO) et le glycérol époxydé (GE). Ces derniers, associés en proportions variables, sont réticulés avec deux différents durcisseurs : l’isophorone diamine (IPDA) ou l’anhydride méthyl tétrahydrophtalique (MTHPA). Les formulations ternaires « ELO – GE – durcisseur » ont été caractérisées selon une approche multi-techniques (DSC, TGA, rhéométrie dynamique et en mode permanent) permettant d’établir des relations structure-propriétés fiables. Puis, la production d’une mousse a été possible grâce à la maîtrise d’une réaction chimique qui se déroule parallèlement à la réticulation de la résine époxy. Le bicarbonate de sodium et de potassium ont été retenus comme agents moussants. Afin d’améliorer les performances finales des mousses, la proportion de GE au sein des formulations polymère à base IPDA a été augmentée. Mais, une telle modification induit la dégradation thermique du système à cause de l’exothermicité élevée de la réaction de réticulation. L’introduction d’un absorbeur d’exothermicité, permet grâce à sa décomposition endothermique de contrôler l’excès de chaleur dégagée et par la même d’empêcher la dégradation. Une dernière classe de durcisseurs a également été étudiée et donne après optimisation des mousses dotés d’excellentes propriétés ultimes. Ainsi, une large gamme de mousses biosourcées rigides et légères pouvant être mises en œuvre dans un temps très court a été développée. / This thesis focuses on the development of a new generation of bio-based polymer foams able to produce low density core in sandwich structure for automotive applications. The polymer formulations used in this research contain two different epoxy compounds, epoxidized linseed oil (ELO) and the epoxidized glycerol (GE). Combined in varying proportions, they were cured with two different hardeners, isophorone diamine (IPDA) or methyl tetrahydrophthalic anhydride (MTHPA). Ternary formulations “ELO – GE – hardener” were characterized by a multi-techniques approach (DSC, TGA, rheometry in steady or dynamic mode) in order to establish structure-property relationships. The production of polymeric-foam materials was carried out by tuning a chemical reaction which takes place during curing. Sodium bicarbonate and potassium bicarbonate were used as harmless foaming agents. In order to improve the final performances of the foams, the ratio GE/ELO was increased in the reactive formulations based on IPDA hardener. But, such modification provokes also the thermal degradation of the system because of the high exothermicity of the curing reaction. The introduction of “exothermicity regulators” that undergo endothermic transformations allowed to control the excess of released heat and consequently, to prevent the material degradation. A last class of hardener was also studied and made it possible after optimization the production of foams with good ultimate properties. To conclude, a large range of biobased and lightweight rigid foams able to be produced in a few minutes was developed.