Atualmente, problemas de interação fluido-estrutura representam um grande desafio em diferentes áreas de engenharia e ciências aplicadas. Dentro das aplicações de engenharia civil, a ação do vento sobre estruturas tem grande relevância principalmente na avaliação de instabilidades elásticas de estruturas muito flexíveis, como pontes e estruturas de membrana. Este trabalho introduz os conceitos principais das estruturas de membrana e da ação do vento em estruturas. A ação do vento em estruturas de membrana será apresentada em capítulo à parte, através de aplicações computacionais para problemas de fluidodinâmica. A ação do vento em estruturas é tratada de forma consistente com as prescrições da norma técnica da Associação Brasileira de Normas Técnicas (ABNT) NBR 6123 Forças devidas ao Vento em Edificações, a qual está vigente desde Junho de 1988. Ainda, foi apresentado breve resumo sobre análise dinâmica do vento através de modelos reduzidos em túneis de vento. Devido às estruturas de membrana possuírem formas incomuns e comportamento estrutural diferenciado com relação às estruturas convencionais, as forças devido à ação do vento nestas estruturas não fazem parte do escopo da NBR 6123. Utilizando-se dos conceitos básicos e benchmarks da norma supracitada, a análise fluido-dinâmica das aplicações será tratada computacionalmente. As leis físicas e equações gerais para solução deste tipo de problema são apresentadas em concordância com o software utilizado. Neste trabalho a ação do vento em estruturas de membrana foi solucionada com acoplamento parcial em algumas aplicações tridimensionais, fazendo-se uso do software Ansys versão 11. Aqui entende-se por acoplamento parcial a tratativa do vento e da estrutura em domínios separados. Em primeira análise, foram obtidas as pressões de vento sobre uma malha de elementos infinitamente rígidos e indeslocáveis com a forma geométrica da membrana. As pressões foram então aplicadas sobre a estrutura, obtendo-se deslocamentos e tensões estáticas. Atualizando-se o domínio do vento para a nova geometria, novos processamentos foram realizados sucessivamente até que a variação de tensões ou das pressões na estrutura fosse desprezível. / Currently, problems of fluid-structure interaction represent a major challenge in different areas of engineering and applied sciences. Within the civil engineering applications, the action of wind on structures has great importance particularly in the evaluation of elastic instabilities of very flexible structures such as bridges and tension membrane structures. This work introduces the main concepts of tension membrane structures and wind acting on structures. The fluid-dynamic analysis are presented in a separate chapter, focused on computational applications. The wind acting on structures is treated consistently with the prescriptions of the national code ABNT (Associação Brasileira de Normas Técnics Brazilian Technical Standards Association) NBR 6123 - Wind Forces on Buildings, issued on June 1988. Still, a brief summary was presented on the dynamic analysis of wind using wind tunnels. As tension membrane structures having unusual shapes and different structural behavior compared to conventional structures, the forces due to wind action on membranes are not part of the scope of NBR 6123. Using the basic concepts and benchmarks available, the fluid-dynamics for the applications are treated computationally. The general physical laws and equations for solving this problem are presented in accordance with the software. The wind acting on membrane structures was solved with partial coupling in some three-dimensional applications, using Ansys v.11 software. Here, partial coupling means solving wind problem and structure problem separately. In the first analysis, the wind problem is solved obtaining pressures over a rigid mesh with the geometric shape of the membrane structure. These pressures are then applied on the membrane, resulting on static displacements and stresses. Updating the domains to the new geometry, other analysis are run until the change over the structural tensions is negligible.

Nesta tese discute-se a necessidade de se desenvolver novas ferramentas para auxiliar o projeto e análise de estruturas de cabos e membranas. Esse tipo de estrutura, essencialmente não linear, é geralmente analisada por meio do Método dos Elementos Finitos, combinado com o Método de Newton-Raphson, para a resolução do sistema de equações não lineares resultante. Porém, a ausência de um campo de tensão de tração sobre toda estrutura composta por elementos finitos de cabos e membranas pode gerar uma matriz de rigidez tangente indeterminada, levando à divergência da solução pelo Método de Newton-Raphson. O Método da Relaxação Dinâmica é uma alternativa interessante para resolver problemas não lineares complicados de equilíbrio estático, na qual o problema do equilíbrio estático é resolvido por uma análise dinâmica, com integração no tempo. A resposta transiente é fictícia e não tem significado físico, entretanto a parte estacionária é a solução do problema de equilíbrio estático. Nesta tese, apresenta-se uma contextualização histórica sobre o Método da Relaxação Dinâmica, apontando as contribuições mais relevantes já desenvolvidas por outros autores. Propõe-se um procedimento de sintonia da massa dos elementos, capaz de uniformizar as condições impostas ao incremento de tempo, para se obter estabilidade do processo de integração numérica. Implementam-se as formulações dos elementos finitos adotados, bem como um algoritmo de enrugamento para os elementos de membrana e diversas rotinas de pós-processamento, no programa de elementos finitos SATS (A System for the Analysis of Taut Structures), desenvolvido pelo autor desta tese, em colaboração com seu orientador. A implementação desenvolvida é aplicada a uma série de exemplos relativos ao projeto e análise de estruturas de cabos e membranas, permitindo verificar a eficiência dos procedimentos de amortecimento e cinético e de sintonia de massa propostos. / This thesis discusses the need to develop new tools to assist the design and analysis of cables and membrane structures. This type of structures, essentially non-linear is generally analyzed using the Finite Element Method, where in most cases the solution is obtained by the Newton-Raphson Method. However, the absence of a tension stress field over the entire structure composed only with cable and membrane finite element can generate a non-positive definite tangent stiffness matrix, leading to the divergence of Newton-Raphson iterations. The Method of Dynamic Relaxation is an interesting alternative to solve complicated nonlinear problems of static equilibrium, replaced by an equivalent dynamic analysis. The transient solution is fictitious and without physical meaning, and the stationary phase provides the static equilibrium solution. This thesis presents a historical contextualization of the Dynamic Relaxation Method, highlighting the most relevant contributions already developed by other authors. A procedure for the tuning of the element masses is proposed, which is capable of making uniform the restrictions imposed to the time steps in order to preserve the stability of the numerical integration. Some adopted finite element formulations are implemented, as well as an algorithm for representing the wrinkling of membrane elements and several post-processing routines, in the SATS (A System for the Analysis of Taut Structures) finite element program, developed by the author of this thesis, in collaboration with his advisor. The developed implementation is applied to a series of examples on the design and analysis of cables and membrane structures, allowing verification of the efficiency of the procedures proposed for kinetic damping and mass tuning.

Předkládaná práce se zabývá problematikou navrhování membránových konstrukcí, a to především s ohledem na vývoj potřebných výpočetních nástrojů v rámci MKP programů. Po uvedení základních fyzikálních požadavků jednotlivých kroků při navrhování těchto konstrukcí budou dále prezentovány vybrané či navržené algoritmy. Kapitola form finding se zabývá analýzou tvaru membránových konstrukcí. Rovnovážný tvar je odvozen od požadavku na výsledné předpětí, specifikované okrajové podmínky a aplikované zatížení. Obecně se ale tento proces zabývá i samotným hledáním rovnovážné soustavy sil v prostoru. V důsledku této skutečnosti jsou součástí popisované analýzy také vhodné stabilizační metody. V této kapitole budou prezentovány jak zvolené postupy, tak i navržená stabilizační technika specializovaná na hledání tvarů kuželových membrán. Dále je také popsán navržený algoritmus pro řešení úloh optimalizujících tvary ohybově tuhých konstrukcí, které jsou spjaty s hledáním labilních rovnovážných konfigurací. Kapitola structural analysis je zaměřená především na fenomén vrásnění membrán. Tato náhlá ztráta stability silně ovlivňuje statickou i dynamickou odezvu membránových konstrukcí. V rámci této kapitoly je představena a verifikována navržená výpočetní metoda, modulárně aplikovatelná na lineární, nelineárně elastické i plastické materiály používané pro uvedené konstrukce. Kapitola cutting pattern generation se zabývá výpočtem střihových vzorů, nezbytných pro výrobní proces membránových konstrukcí. Pro tento proces je v rámci předkládané práce navržena kombinace dvou různých metod. Zvolená posloupnost algoritmů cílí na optimalizaci poměru rychlosti, obecnosti a přesnosti výpočtu. Zmíněné kapitoly jsou doplněny jednotlivými příklady, analyzovanými pomocí popisovaných algoritmů, které demonstrují konkrétní fyzikální problémy či nezbytné implementační procesy.

This diploma thesis deals with methods for design of membrane structure shape. Main purpose is to analyze topology designs by Formfinder and Rhinoceros in RFEM and compare results. Test a possibility of designing shape by software RFEM.

Les cellules présentatrices d'antigène (CPAs) font le lien entre le système immunitaire inné et adaptatif en présentant des antigènes (Ags) étrangers aux cellules T CD4+. Pour être efficace, cette présentation nécessite que les Ags soient apprêtés et chargés de manière adéquate dans le sillon des molécules du complexe majeur d'histocompatibilité de classe II (CMHII). C'est uniquement dans ce contexte que les cellules T CD4+, via leur récepteur (TCR), peuvent reconnaître l'Ag et engager pleinement la réponse immunitaire adaptative. Ce processus doit être finement contrôlé pour diminuer les risques de réaction auto- immune. L'expression de CMHII est régulée à la fois au niveau transcriptionnel par le trans- activateur du CMHII (CIITA) et au niveau post-traductionnel via l’ubiquitination d'un seul résidu de lysine, situé dans la queue cytoplasmique de sa chaîne b. Dans les cellules dendritiques (DCs) et les cellules B, cette ubiquitination est dépendante de la E3 ubiquitine ligase MARCH1. La baisse d’expression de MARCH1 contribue à l'acquisition de propriétés immuno-stimulatrices qui accompagnent la maturation des DCs humaines. De plus, il a été démontré que l'absence d'ubiquitination du CMHII entraîne son accumulation excessive au niveau de la membrane plasmique, ce qui perturbe les radeaux lipidiques et les réseaux de tétraspanines chez les DCs de souris. Ces structures membranaires sont connues pour interagir avec des molécules de signalisation régulant de nombreux processus biologiques dans les cellules B, comme le récepteur des cellules B (BCR) et CD19. De surcroît, dans les cellules B naïves, les molécules de CMHII sont fortement exprimées à la surface cellulaire, même si elles sont constitutivement ubiquitinées par MARCH1. Il est également intéressant de noter que les lymphocytes B présentent l'expression la plus élevée de MARCH1 parmi toutes les cellules immunitaires et que cette expression augmente au cours de leur développement. L'impact qu’a l’ubiquitination des molécules de CMHII à la surface membranaire des lymphocytes B sur leur développement, leur activation et leurs fonctions n'a pas encore été pleinement étudié. Ici, nous montrons d'abord que l'absence d'ubiquitination du CMHII modifie fortement le pool de cellules B de la zone marginale (MZBs). Nous soutenons que cette altération peut résulter en partie de la protéotoxicité du CMHII sur les réseaux de tétraspanines contenant CD81, ce qui influe sur la dynamique de CD19 à la surface cellulaire et affecte sa capacité à activer la cascade PI3K / Akt induite par les signaux BCR dits « toniques ». L’altération du pool de cellules MZBs a également des répercussions sur la réponse immunitaire aux Ags T-indépendants de type 2 (TI-2 Ags) et sur la formation de centre germinatifs (GCs) dans la rate. Ensemble, ces effets atténuent la réponse humorale et peuvent conférer un effet protecteur contre les infections. Par exemple, nous montrons ici que les infections parasitaires à Leishmania donovani, dont l’établissement nécessite la présence de cellules B pleinement fonctionnelles, sont beaucoup mieux contrôlées en l’absence de MARCH1. Ces résultats démontrent qu’un contrôle fin de l'expression de surface du CMHII est nécessaire pour l'établissement d'un pool de cellules B variées et pleinement fonctionnelles pouvant répondre à une large gamme d'Ags. En second lieu, nous avons décrit une approche expérimentale que nous avons adaptée pour produire des outils moléculaires permettant d’identifier des partenaires d’interaction potentiels de MARCH1 dans des lignées cellulaires et des cellules B primaires. Cette approche repose sur la production de protéine de fusion qui pourront être utilisées dans des tests de liaison de proximité (BioID2). Ce projet a permis de mettre en lumière les effets importants de l'ubiquitination du CMHII sur le développement, l'activation et les fonctions des lymphocytes B. Il a également permis d’établir des bases solides pour de futures études sur de nouvelles cibles de MARCH1 qui permettront de mieux comprendre les effets biologiques de cette E3 ubiquitine ligase et leurs impacts sur la santé et les maladies. / Antigen-presenting cells (APCs) link the innate and adaptive immune system by presenting foreign antigens to CD4+ T cells. To be efficient, this presentation requires antigens to be adequately processed and loaded in the peptide groove of the major histocompatibility complex class II (MHCII) molecules. It's solely in this context that CD4+ T cells, via their T cell receptor (TCR), can recognize the antigen and fully engage the adaptative immune response. This process needs to be tightly regulated to avoid autoimmunity. MHCII expression is regulated both transcriptionally by the MHCII transactivator (CIITA) and post- translationally by ubiquitination of a single lysine residue located in the cytoplasmic tail of its b-chain. This is carried out by the MARCH1 E3 ubiquitin ligases in dendritic cells (DCs) and B cells. The down-regulation of MARCH1 contributes to the acquisition of potent immunostimulatory properties that coincides with the maturation of human DCs. Accordingly, the lack of MHCII ubiquitination has been shown to result in its excessive accumulation at the plasma membrane and in the disruption of lipid rafts and tetraspanin webs in mice DCs. These membrane structures are known to interact with signaling molecules that regulate numerous biological processes in B cells, such as the B cell receptor (BCR) and CD19. Moreover, in naïve B cells, MHCII molecules are highly expressed at the cell surface even if they are constitutively ubiquitinated by MARCH1. Interestingly, B lymphocytes exhibit the highest expression of MARCH1 among all immune cells and this expression is increasing during B cells development. The impact of the ubiquitin-dependent MHCII turnover on B lymphocytes development, activation, and functions have yet to be fully addressed. Here, we first show that the absence of MHCII ubiquitination strongly alter the marginal zone (MZ) B cell pool. We provide evidence that this alteration may in part be due to the previously described MHCII proteotoxicity on the CD81-containing tetraspanin web, which impacted CD19 surface dynamic and its capacity to activate the PI3K/Akt cascade during “Tonic” BCR signaling. The altered MZ B cell pool also affected the immune response to a type 2 T-independent antigen (TI-2 Ag) and the germinal center (GC) reaction in the spleen, which dampens humoral response and may confer a protective effect against infections. As per example, we show here that parasitic infections with Leishmania donovani, the establishment of which requires the presence of fully functional B cells, are better controlled in the absence of MARCH1. These results demonstrate the need for a tight control over MHCII surface expression for the establishment of a varied and fully functional B cell pool, which are mandatory for proper responses to a broad range of antigens. Secondly, we described an experimental approach that we adapted to produce molecular tools that will allow the identification of potential interacting partners of MARCH1 in cell lines and primary B cells. This approach is based on the production of fusion proteins that can be used in proximity binding assays (BioID2). This project shed light on the important effects of MHCII ubiquitination on the development, activation, and function of B lymphocytes. It also laid the groundwork for valuable future studies on novel MARCH1 targets which will provide a better understanding of the biological effects of this E3 ubiquitin ligase and their impact on health and disease.

As estruturas de membrana empregadas em coberturas são sistemas construtivos formados principalmente pela membrana estrutural, que ainda tem a função de vedar. As membranas estruturais são folhas flexíveis que resistem às ações externas devido à sua forma, às suas características físicas e ao seu pré tracionamento. O pré-tracionamento da membrana pode ser alcançado, ou através do seu estiramento por meio de cabos (estruturas de membrana protendida por cabos), ou através da atuação da pressão de gases (estruturas pneumáticas). Ambas estão sendo usadas em coberturas de centros esportivos, de áreas comerciais e de construções industriais ou agro-industriais. Todavia, as estruturas de membrana são pouco conhecidas, estudadas e empregadas no Brasil. Neste contexto, este trabalho tem como objetivos sistematizar o conhecimento científico existente sobre o tema e introduzi-lo no Brasil e, também, apontar caminhos para investigação científica sobre as estruturas de membrana no país. Apresenta o sistema construtivo, o processo de projetar e os métodos de análise das estruturas de membrana empregadas em coberturas. Sistematiza o projeto de estruturas de membrana, através de recomendações e de estudo de caso. Propõe um modelo de pesquisa integrado voltado para o desenvolvimento desta tecnologia no Brasil. Este deve auxiliar a coordenação e a compatibilização dos esforços de investigação científica nas diversas áreas do conhecimento envolvidas no desenvolvimento das estruturas de membrana / Membrane structures used in roofs are constructive systems formed mainly by structural membrane, which has also the function of sealing. Structural membranes are flexible sheets that resist to external loads due to their form, to their physical characteristics and to their pre-stressing. The pre-stressing of the membrane can be achieved either through its stretching using cables (surface-tensioned membranes) or through gases pressurization (pneumatic structures). These structures are being utilized in roofs over airports, stadiums, industrial facilities, shopping precincts and buildings for industrial or agricultural use, among others. However, membrane structures are not yet well known, studied and used here in Brazil. In this context, this work has as objectives to systematize the scientific knowledge existent on the theme, to introduce it in Brazil and, also, to point out ways for scientific investigation on membrane structures in this country. This research presents the constructive system, the design process and the analysis methods of membrane structures used in roofs. This work systematizes the membrane structural design, with recommendations and study of case. This work proposes an integrated model of research for this technology development in Brazil. This model should assist the coordination and the mutual appreciation of the scientific investigation efforts in the different knowledge areas involved in the membrane structure development

As estruturas de membrana empregadas em coberturas são sistemas construtivos formados principalmente pela membrana estrutural, que ainda tem a função de vedar. As membranas estruturais são folhas flexíveis que resistem às ações externas devido à sua forma, às suas características físicas e ao seu pré tracionamento. O pré-tracionamento da membrana pode ser alcançado, ou através do seu estiramento por meio de cabos (estruturas de membrana protendida por cabos), ou através da atuação da pressão de gases (estruturas pneumáticas). Ambas estão sendo usadas em coberturas de centros esportivos, de áreas comerciais e de construções industriais ou agro-industriais. Todavia, as estruturas de membrana são pouco conhecidas, estudadas e empregadas no Brasil. Neste contexto, este trabalho tem como objetivos sistematizar o conhecimento científico existente sobre o tema e introduzi-lo no Brasil e, também, apontar caminhos para investigação científica sobre as estruturas de membrana no país. Apresenta o sistema construtivo, o processo de projetar e os métodos de análise das estruturas de membrana empregadas em coberturas. Sistematiza o projeto de estruturas de membrana, através de recomendações e de estudo de caso. Propõe um modelo de pesquisa integrado voltado para o desenvolvimento desta tecnologia no Brasil. Este deve auxiliar a coordenação e a compatibilização dos esforços de investigação científica nas diversas áreas do conhecimento envolvidas no desenvolvimento das estruturas de membrana / Membrane structures used in roofs are constructive systems formed mainly by structural membrane, which has also the function of sealing. Structural membranes are flexible sheets that resist to external loads due to their form, to their physical characteristics and to their pre-stressing. The pre-stressing of the membrane can be achieved either through its stretching using cables (surface-tensioned membranes) or through gases pressurization (pneumatic structures). These structures are being utilized in roofs over airports, stadiums, industrial facilities, shopping precincts and buildings for industrial or agricultural use, among others. However, membrane structures are not yet well known, studied and used here in Brazil. In this context, this work has as objectives to systematize the scientific knowledge existent on the theme, to introduce it in Brazil and, also, to point out ways for scientific investigation on membrane structures in this country. This research presents the constructive system, the design process and the analysis methods of membrane structures used in roofs. This work systematizes the membrane structural design, with recommendations and study of case. This work proposes an integrated model of research for this technology development in Brazil. This model should assist the coordination and the mutual appreciation of the scientific investigation efforts in the different knowledge areas involved in the membrane structure development

This work deals with the design and calculation of membrane structure for shelter placed above selected ground plan. The hyperbolic paraboloid was chosen as most optimal shape. Subsequently, three different sub-studies were conducted. In the first study, influence of mesh density on a finite element calculation model was studied. Second study deal with the effect of the geometry changes of the computational model. In the third study, deformations and tensions of membrane structure in relation to material formation calculation model was studied. For the static solution of those selected variant, structural analysis software RFEM and RF-FORM-FINDING add-on module was used. Geometric nonlinear solution was applied in the calculation.

This work aims at dimensional reduction of nonlinear material models in an asymptotically accurate manner. The three-dimensional(3-D) nonlinear material models considered include isotropic, orthotropic and dielectric compressible hyperelastic material models. Hyperelastic materials have potential applications in space-based inflatable structures, pneumatic membranes, replacements for soft biological tissues, prosthetic devices, compliant robots, high-altitude airships and artificial blood pumps, to name a few. Such structures have special engineering properties like high strength-to-mass ratio, low deflated volume and low inflated density. The majority of these applications imply a thin shell form-factor, rendering the problem geometrically nonlinear as well. Despite their superior engineering properties and potential uses, there are no proper analysis tools available to analyze these structures accurately yet efficiently. The development of a unified analytical model for both material and geometric nonlinearities encounters mathematical difficulties in the theory but its results have considerable scope. Therefore, a novel tool is needed to dimensionally reduce these nonlinear material models. In this thesis, Prof. Berdichevsky’s Variational Asymptotic Method(VAM) has been applied rigorously to alleviate the difficulties faced in modeling thin shell structures(made of such nonlinear materials for the first time in the history of VAM) which inherently exhibit geometric small parameters(such as the ratio of thickness to shortest wavelength of the deformation along the shell reference surface) and physical small parameters(such as moderate strains in certain applications). Saint Venant-Kirchhoff and neo-Hookean 3-D strain energy functions are considered for isotropic hyperelastic material modeling. Further, these two material models are augmented with electromechanical coupling term through Maxwell stress tensor for dielectric hyperelastic material modeling. A polyconvex 3-D strain energy function is used for the orthotropic hyperelastic model. Upon the application of VAM, in each of the above cases, the original 3-D nonlinear electroelastic problem splits into a nonlinear one-dimensional (1-D) through-the-thickness analysis and a nonlinear two-dimensional(2-D) shell analysis. This greatly reduces the computational cost compared to a full 3-D analysis. Through-the-thickness analysis provides a 2-D nonlinear constitutive law for the shell equations and a set of recovery relations that expresses the 3-D field variables (displacements, strains and stresses) through thethicknessintermsof2-D shell variables calculated in the shell analysis (2-D). Analytical expressions (asymptotically accurate) are derived for stiffness, strains, stresses and 3-D warping field for all three material types. Consistent with the three types of 2-D nonlinear constitutive laws,2-D shell theories and corresponding finite element programs have been developed. Validation of present theory is carried out with a few standard test cases for isotropic hyperelastic material model. For two additional test cases, 3-Dfinite element analysis results for isotropic hyperelastic material model are provided as further proofs of the simultaneous accuracy and computational efficiency of the current asymptotically-correct dimensionally-reduced approach. Application of the dimensionally-reduced dielectric hyperelastic material model is demonstrated through the actuation of a clamped membrane subjected to an electric field. Finally, the through-the-thickness and shell analysis procedures are outlined for the orthotropic nonlinear material model.

This diploma thesis deals with problem of design and calculation of membrane structure of stadium roof. This is a complex engineering problem, which includes many partial problems: finding of initial form of membrane, statically and architecturally suitable arrangement of catenaries, economical solution of boundary conditions (foundations). All components affect each other and cannot be dealt without mutual coordination. It always greatly depends on the experience and intuition of engineer who design such structure. Task which cannot be resolved according to the theory of the first order. Equilibrium forces on the deformed structure, which in many projected structures gives satisfactory results, did not correspond to reality. It is therefore necessary to consider equilibrium of forces on the deformed structure according to the theory of large deformations. Diploma thesis was entered with regard to the intention of the companies Ing. Software Dlubal s.r.o. and FEM consulting s.r.o., working together to develop software RFEM. These companies plan to complement this program system with a module MEMBRANE for searching of initial shapes of membrane structures. This work is a contribution to the creation of this module.