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Les structures de type gridshell élastique permettent de réaliser des enveloppes courbes par la déformation réversible d’une grille structurelle régulière initialement plane. Cette capacité à “former la forme” de façon efficiente prend tout son sens dans le contexte actuel où, d’une part la forme s’impose comme une composante prédominante de l’architecture moderne, et d’autre partl’enveloppe s’affirme comme le lieu névralgique de la performance des bâtiments. Fruit des recherches de l’architecte et ingénieur allemand Frei Otto dans les années 1960, elles ont été rendues populaires par la construction de la Multihalle de Mannheim en 1975. Cependant, en dépit de leur potentiel, très peu de projets de ce type ont vu le jour suite à cette réalisation emblématique qui en a pourtant démontré la faisabilité à grande échelle. Et pour cause, les moyens engagés à l’époque ne sauraient assurer la reproductibilité de cette expérience dans un contexte plus classique de projet, notamment sur le plan économique. Par ailleurs, les techniques et les méthodes développées alors sont pour la plus part tombées en désuétude ou reposent sur des disciplines scientifiques qui ont considérablement évoluées. Des matériaux nouveaux, composites, ont vu le jour. Ils repoussent les limitations intrinsèques des matériaux usuels tel que le bois et offrent des performances techniques bien plus intéressantes pour ce type d’application. Enfin, notons que le cadre réglementaire a lui aussi profondément muté, apportant une certaine rigidité vis-à-vis de la pénétration des innovations. Ainsi la conception des gridshells se pose-t-elle en des termes nouveaux aux architectes et ingénieurs actuels et se heurte à l’inadéquation des outils et méthodes existant. Dans cette thèse, qui marque une étape importante dans une aventure de recherche personnelle initiée en 2010, nous tentons d’embrasser la question de la conception des gridshells élastiques dans toute sa complexité, en abordant aussi bien les aspects théoriques que techniques et constructifs. Dans une première partie, nous livrons une revue approfondie de cette thématique et nous présentons de façon détaillée l’une de nos principales réalisation, la cathédrale éphémère de Créteil, construite en 2013 et toujours en service. Dans une seconde partie, nous développons un élément de poutre discret original avec un nombre minimal de degrés de liberté adapté à la modélisation de la flexion et de la torsion dans les gridshells constitués de poutres de section anisotrope. Enrichi d’un noeud fantôme, il permet de modéliser plus finement les phénomènes physiques au niveau des connexions et des appuis. Son implémentation numérique est présentée et validée sur quelques cas tests. Bien que cet élément ait été développé spécifiquement pour l’étude des gridshells élastiques, il pourra avantageusement être utilisé dans tout type de problème où la nécessité d’un calcul interactif avec des tiges élastiques prenant en compte les couplages flexion-torsion s’avère nécessaire / An elastic gridshell is a freeform structure, generally doubly curved, but formed out through the reversible deformation of a regular an initially flat structural grid. Building curved shapes that way seems to offer the best of both worlds : shell structures are amongst the most performant mechanically speaking while planar and orthogonal constructions are much more efficient and economic to produce than curved ones. This ability to “form a form” efficiently is of peculiar importance in the current context where morphology is a predominant component of modern architecture, and envelopes appear to be the neuralgic point for building performances. The concept was invented by Frei Otto, a German architect and structural engineer who devoted many years of research to gridshells. In 1975 he designed the Multihalle of Mannheim, a 7500 m2 wooden shell which demonstrated the feasibility of this technology and made it famous to a wide audience. However, despite their potential, very few projects of this kind were built after this major realization. And for good reason, the ressources committed at that time cannot guarantee the replicability of this experiment for more standard projects, especially on the economic level. Moreover, the technics and methods developed by Otto’s team in the 1960s have mostly fall into disuse or are based on disciplines that have considerably evolved. New materials, such as composite materials, have recently emerged. They go beyond the limitations of conventional materials such as timber and offer at all levels much better technical performances for this kind of application. Finally, it should be noted that the regulatory framework has also deeply changed, bringing a certain rigidity to the penetration of innovations in the building industry. Therefore, the design of gridshells arises in new terms for current architects and engineers and comes up against the inadequacy of existing tools and methods. In this thesis, which marks an important step in a personal research adventure initiated in 2010, we try to embrace the issue of the design of elastic gridshells in all its complexity, addressing both theoretical, technical and constructive aspects. In a first part, we deliver a thorough review of this topic and we present in detail one of our main achievements, the ephemeral cathedral of Créteil, built in 2013 and still in service. In a second part, we develop an original discrete beam element with a minimal number of degrees of freedom adapted to the modeling of bending and torsion inside gridshell members with anisotropic cross-section. Enriched with a ghost node, it allows to model more accurately physical phenomena that occur at connections or at supports. Its numerical implementation is presented and validated through several test cases. Although this element has been developed specifically for the study of elastic gridshells, it can advantageously be used in any type of problem where the need for an interactive computation with elastic rods taking into account flexion-torsion couplings is required

The stiffness and frequency properties of tensegrity structures are functions of the pre-stress, topology, configuration, and axial stiffness of the elements. The tensegrity structures considered are tensegrity booms, tensegrity grids, and tensegrity power lines. A study has been carried out on the pre-stress design. It includes (i) finding the most flexible directions for different pre-stress levels, (ii) finding the pre-stress pattern which maximizes the first natural frequency. To find the optimum cross-section areas of the elements for triangular prism and Snelson tensegrity booms, an optimization approach is utilized. A constant mass criterion is considered and the genetic algorithm (GA) is used as the optimization method. The stiffness of the triangular prism and Snelson tensegrity booms are modified by introducing actuators. An optimization approach by means of a GA is employed to find the placement of the actuators and their minimum length variations. The results show that the bending stiffness improves significantly, but still an active tensegrity boom is less stiff than a passive truss boom. The GA shows high accuracy in searching the non-structural space. The tensegrity concept is employed to design a novel transmission power line .A tensegrity prism module is selected as the building block. A complete parametric study is performed to investigate the influence of several parameters such as number of modules and their dimensions on the stiffness and frequency of the structure. A general approach is suggested to design the structure considering wind and ice loads. The designed structure has more than 50 times reduction of the electromagnetic field and acceptable deflections under several loading combinations. A study on the first natural frequencies of Snelson, prisms, Micheletti, Marcus and X-frame based tensegrity booms has been carried out. The result shows that the differences in the first natural frequencies of the truss and tensegrity booms are significant and not due to the number of mechanisms or pre-stress levels. The tensegritybooms of the type Snelson with 2 bars and prism with 3 bars have higher frequencies among tensegrity booms. / <p>QC 20120904</p>

QC 20100901

Detta examensarbete tar plats i Bredäng, söder om Stockholm. Projektet har varit en undersökning i hur man omarbetar, anpassar och informerar två befintliga bostadshus från miljonprogramsåren till dagens behov. Med syfte att skapa kontinuitet och komplexitet i dessa strikta strukturella fält, detta genom en formfinnande process där textilt skumgummi har använts som ett medlande objekt av additiv och subtraktiv information med referenser till “The Renewed Novelty of Symmetry” av Greg Lynn. Det är ett spekulativt projekt som tar upp frågor kring byggnaders evolution samt begreppet "mismatch", med ambitionen att dessa byggnader skall få fortsätta berättelsen om nya sätt att bygga bra bostäder för framtiden. Den berättelse som de en gång var en del utav när miljonprogrammet utvecklades, då avståndet mellan forskning och profession var mycket kort och byggnaderna byggdes tillsammans med de nyaste idéerna och teknikerna för den tiden. Men att låta livet i och runt dessa byggnadsstrukturer ha en inverkan på sin egen situation samt att förankra byggnaderna på platsen har varit fokus. / This thesis project has been an investigation in how to rework, adapt and inform two existing housing structures from the million-programme-era in Bredäng, south of Stockholm, to the needs of today. Aiming to create continuity and complexity in these structural fields through a form finding process using textile foam rubber as the intermediating object of additive and subtractive information, referring to “The Renewed Novelty of Symmetry” by Greg Lynn. It's a speculative project that takes on the question of building evolution and mismatch, where I want these buildings to continue the story of new innovative ways of building good housing for the future. The story which they once where part of when the million-program-era was developed, when the distance between research and profession was short and the buildings where built with the new building ideas and techniques of that time. So trying to let the life within and around these building structures have an impact on its own situation and also tying the buildings to the site has been the main focus.

La majorité des bâtiments existant aujourd'hui ne respectent pas les réglementations thermiques actuelles. Pour répondre aux exigences environnementales il est impossible, dans ce contexte, d'envisager une politique globale de démolition-reconstruction. Des campagnes de réhabilitation doivent être mises en place. Une solution innovante de réhabilitation énergétique est proposée permettant d'exploiter les ressources énergétiques urbaines, peu utilisées actuellement. Elle consiste à rajouter autour du bâtiment une enveloppe extérieure qui aurait pour fonction principale le captage d'énergie solaire. Un outil d'optimisation de la géométrie de l'enveloppe et de la distribution spatiale de panneaux capteurs à sa surface est développé. Sa validation est effectuée sur des cas simples, puis il est appliqué aux situations présentant de forts contrastes : optimisation pendant la période d'hiver ou d'été, à Oslo ou à Tunis, avec des obstacles proches masquant le Soleil. Afin de réaliser les formes complexes obtenues, il est proposé d'utiliser les gridshells comme système constructif. Ces structures obtenues par déformation élastique d'une grille de poutres en matériau composite initialement planes posent la question de la durabilité de ces matériaux soumis au chargement permanent. Pour étudier le comportement à long terme (fluage et rupture différée) de ces matériaux composés de fibres de renfort et matrice polymère viscoélastique, un modèle micro-mécanique est développé. Ce modèle de type shear-lag permet d'étudier l'influence des propriétés mécaniques des constituants sur la durée de vie du composite soumis à un chargement en traction et traction-cisaillement combinés / The majority of existing buildings does not follow present energy efficiency regulations. In order to fulfill environmental requirements it seems impossible, in this context, to consider a global demolition-reconstruction policy. Renovation programmes need to be implemented. An innovative energy efficiency improvement solution is proposed, enabling to explore urbain energy ressources presently underexploited. The concept is to add, around the building, an external envelope whose main function would be to collect energy. An optimization tool aiming at finding the optimal geometry and collectors' spatial distribution on the envelope's surface, is developed. Its validation is carried out on simple cases, it is then applied in situations showing strong contrasts: optimization during summer and winter, in Oslo and in Tunis, with close obstacles partially masking the Sun. In order to build the emerging complex geometries, the use of gridshell structures is proposed. These structures are obtained through elastic deformation of an initially plane grid made of composite material slender beams. This raises the problem of composite materials durability under sustained loading. In order to study the long-term behavior (creep and creep rupture) of these materials composed of reinforcing fibres and a polymeric viscoelastic matrix, a micromechanical model is developed. This shear-lag type model allows studying the influence of the constituents' mechanical properties on the lifespan of the composite under permanent pure traction or combined shear and traction loadings

Esta dissertação trata das metodologias de busca da forma (form finding) aplicadas a sistemas estruturais de cabos de aço retesados, destacando aquelas que foram amplamente utilizadas pelo arquiteto alemão Frei Otto: modelos físicos de correntes e molas e o método numérico das Densidades de Forças. O método de Relaxação Dinâmica, as soluções gráficas, modelos de correntes e pesos, assim como os de películas de sabão, também foram analisados de modo breve. O trabalho objetivou examinar as singularidades de tais metodologias de concepção estrutural. Tarefa que foi realizada, em primeiro lugar, por meio da revisão da literatura crítica acerca do emprego e do desenvolvimento das tecnologias de sistemas de cabos de aço retesados. Em seguida, partindo das obras examinadas, simulou-se quatro situações de projetos de estruturas retesadas, que foram executadas através da construção de modelos físicos e numéricos. As maquetes físicas foram construídas por meio de modelos de correntes e molas, e tiveram o intuito de fornecer dados de ordem qualitativa acerca do comportamento estrutural. As representações digitais, por sua vez, foram desenvolvidas com o método das Densidades de Forças, por intermédio do software Rhinoceros e do seu plug-in Grasshopper. Elas permitiram avaliar critérios quantitativos, como precisão, conformidade e eficiência. Por fim, os resultados obtidos através dos modelos físicos foram comparados aos experimentos digitais, com o intuito de analisar as especificidades de cada alternativa, buscando compreender as vantagens e limites de suas aplicações práticas. / This work presents two form finding methodologies applied to steel cable structures, physical model with springs and Force Density Method, both widely used by Frei Otto and his team. Other techniques are also studied; e.g. chains models, soap film models, graphic solutions and Dynamic Relaxation Method. Firstly, the historical developments of form-active structures were listed, together with a series of projects that became technical and conceptual milestones in the Brazilian and international scenario. Secondly, the process of manufacturing two form finding models is reported, one physical spring model and one numerical Force Density Method performed with computer-aided design (CAD) application Rhinoceros and its plug-in Grasshopper. Both models were carried out aiming to investigate their advantages and limits. Lastly, four experimental case studies were selected, based on projects studied in the first phase of this work. Diverse typologies and boundary conditions were chosen for comparative evaluation of the qualitative physical model and the numerical one. The appraisal of the modeling techniques\' efficiency and robustness levels was done through analysis of the differences between nodes\' coordinates and bars\' lengths obtained through each method.

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.

This thesis aims to study the design possibilities for supporting explorative form-finding in 3D modeling applications. For today’s many design professions, 3D forms are achieved partly in engagement with digital environments. Use of software has far exceeded final idea execution, extending to the early phases of design work in which the outcome is not predetermined. This insight led designers of interactive systems support sketching and ideating activities by reducing the risk of experimentation and cognitive effort demanded from user. Yet, there has been less emphasis on traditional design and craft practice that acknowledges engagement with materials and effort spent on work as an integral part of creative process.The notion of exploration in the scope of this thesis attempts to incorporate such aspects. Relevant literature about workshop practice in design and craft has been reviewed, as well as examples of CAD technologies that aid designers. In this light, HCI perspectives on the design of creativity support tools and games have been discussed. The thesis work aimed to concretize this background by building a design strategy and an interactive artifact. A 3D form-finding application concept using objects in modeling space to indirectly manipulate geometry, “kfields”, has been developed and evaluated with users at various stages. The thesis concludes by reflecting on the findings of different design stages and proposing further directions for design.