01 Fakultät Architektur und Stadtplanung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/2
Browse
9 results
Search Results
Item Open Access Glasfaserverstärkte Kunststoffe unter hoher thermischer und mechanischer Belastung(2009) Ludwig, Carsten; Knippers, Jan (Prof. Dr.-Ing.)Faserverstärkte Kunststoffe (FVK) bieten gegenüber konventionellen Materialien mehrere Vorteile, wie zum Beispiel hohe spezifische Festigkeiten, einen guten Korrosionswiderstand und eine geringe Wärmeleitfähigkeit. Mit der steigenden Verwendung von Glasfaserverstärkten Kunststoffen (GFK) für Tragstrukturen, wie sie in diversen Projekten eingesetzt wurden, ist es von großer Bedeutung, den Einfluss hoher Temperaturen im Lastfall Brand auf das mechanische Verhalten abschätzen zu können. Dieser fehlende Nachweis schränkt bisher das Applikationspotential als Werkstoff für Tragwerke erheblich ein. Grundsätzlich lassen sich Faserverstärkte Kunststoffe in ihren Eigenschaften durch die Wahl der Faser und Matrix, über den Herstellungsprozess und die Nachbehandlung innerhalb weiter Grenzen variieren. Für die grundlegenden Untersuchungen in dieser Arbeit wurde jedoch nicht angestrebt, einen bestimmten Verbund für möglichst viele Belastungsfälle umfassend zu charakterisieren, sondern es wurden für drei verschiedene Materialkombinationen (E-Glasfaser/ungesättigtem Polyester-, Vinylester- und Phenolharz) die verbundspezifischen Eigenschaften bei erhöhter Temperatur und unter gleichzeitiger mechanischer Biegebeanspruchung erfasst. Als grundlegende Methode zur Werkstoffdatengenerierung von glasfaserverstärkten Kunststoffen wird in dieser Arbeit die Thermische Analyse angewendet. Um die Verbunde so wenig wie möglich zu schädigen, wurden verschiedene Methoden zur Herstellung der Probekörper evaluiert, da diese erheblichen Einfluss auf die Messungen der Thermischen Analyse haben. Durch die thermische Beanspruchung der Verbunde in den Untersuchungen verändern sich sowohl kalorische und thermogravimetrische, als auch mechanische Eigenschaften. Insbesondere der Elastizitätsmodulverlauf gilt als einer der Hauptindikatoren zur Beurteilung der Strukturintegrität bei hohen Temperaturen. Experimentelle Untersuchungen von glasfaserverstärkten Polyesterharzprofilen an einem Kleinversuchsofen zeigen, dass keine Linearität zwischen der Wahl größerer Trägerquerschnitte mit höheren Widerstandsmomenten und einer längeren Feuerwiderstandsdauer besteht. Die Versuche machen Schwächen von GFK-Tragelementen unter Drei-Punkt-Biegung im Druckbereich deutlich, die vierseitig bei hohen Temperaturen beflammt werden. Auf Grundlage der experimentellen Ergebnisse wurden im Weiteren numerische und analytische Modelle generiert. Die auf die thermische Belastung reduzierten numerischen Modellierungen erlauben eine Auswertung des Einflusses der thermischen Kennwerte und die Angabe von groben Empfehlungen für die Versagenszeiträume in Bezug auf ihren Ausnutzungsgrad. Dies führte zur Aufstellung eines analytischen Modells, welches unter Annahme gleichmäßiger allseitiger Erwärmung in Abhängigkeit einer Ausbreitungsgeschwindigkeit von Isothermen gesetzt werden konnte. Eine auf den experimentellen Ergebnissen basierende numerische Ergebnismodellierung mit thermischer und mechanischer Beanspruchung zeigte geringe Abweichungen von den versuchstechnisch ermittelten Werten. Dabei konnte die Gültigkeit eines linear elastischen Werkstoffverhaltens der GFK-Profilträger in Abhängigkeit von der Zeit und innerhalb eines bestimmten Temperaturniveaus als hinreichend genau bestätigt werden.Item Open Access Bio-inspired integrated actuation and variable stiffness for compliant mechanisms(Stuttgart : Institut für Tragkonstruktionen und Konstruktives Entwerfen, Universität Stuttgart, 2022) Mader, Anja; Knippers, Jan (Prof. Dr.-Ing.)Due to advantages, such as a low mechanical complexity, low weight, and the absence of friction of wear, compliant kinetic systems are increasingly used, including for large-scale applications like facade shading. To exploit the advantages also for the actuation, bio-inspired joint-free actuators were developed within two case studies. Both actuation principles proved their potential to actuate 2-dimenional compliant devices within physical prototypes. Additionally, adaptive stiffness concepts were developed to potentially increase the load bearing capability temporarily. Following a biomimetic top-down approach, the leaf folding of the model plant Sesleria nitida caused by turgor variations within large bulliform cells was investigated using a FEA. The turgor pressure opens the leaf against a present pre-stress. Turgor and volume variation within the bulliform cells that result from fluctuations in water availability generate forces high enough to fold and unfold the leaf. This pressurize-based actuation principle is abstracted to a technical cellular structure constructed from GFRP (glass fibre-reinforced plastic) cells with compliant hinges. An increase in inner cell pressure causes a reconfiguration of the cell and an overall bending motion of the actuator. At the same time, thin-walled plant tissues show a strong turgor dependent stiffness. By adding a second, counteracting cell row that decouples deformation from absolute pressure, this can be realized also in the technical actuator. The bending motion is now determined by the pressure ratio, and the stiffness by the pressure magnitude. Within physical and numerical experiments, the stiffness of a cellular actuator increases by a factor of 2.5 at a pressure increase of 1 bar. Within the second case study, a pneumatic actuation that is fully integrated into a GFRP laminate was developed. The wing vein ultrastructure of Graphosoma lineatum italicum inspired the laminate built-up of the GFRP with an integrated pneumatic pouch. By surrounding the pouch with an elastomeric layer, analogous to the resilin bearing endocuticle within the biological model, a delamination of the laminate layers is prohibited. The approach allows a simple fabrication, and slender, homogenous appearance. Upon an internal pressure increase, the eccentric placement of the pneumatic pouch and the greater compliance of the thinner layer results in a rotation into that direction. This way a folding motion is realized by a pouch placed in a hinge zone of greater compliance. A quasi-uniform bending is created by placing a segmented large-surface pouch integrated in a plate of distributed compliance. The adaptive stiffness is added by an antagonistic actuator set-up inspired by opposing muscles used to control and stiffen skeletal joints. For a GFRP plate an increase in stiffness of 60% was achieved at 1.8 bar internal pressure.Item Open Access Compliant folding : design and fabrication methodology for bio-inspired kinetic folding mechanisms utilized by distinct flexible hinge zones(Stuttgart : Institut für Tragkonstruktionen und Konstruktives Entwerfen, Universität Stuttgart, 2021) Körner, Axel Hannes; Knippers, Jan (Prof. Dr.-Ing.)Within the larger context of bio-inspired compliant mechanisms for architectural applications and adaptive building envelopes, this thesis aims for the establishment of a design and fabrication framework for bio-inspired compliant folding mechanisms, utilized by distinct flexible hinge-zones. This includes a methodological design approach, consisting of the abstraction and classification of biological folding mechanisms, as well as a sequential abstraction process of underlying working principles regarding kinetic behaviour, materialisation, and actuation strategies. Furthermore, the geometric adaptability and the design space of the established folding mechanisms has been evaluated, especially related to the applicability to different tessellation patterns for double curved surfaces. The insights built the basis for the development of a series of technical applications on a demonstrator level. The functional case studies serve not only as basis to test and evaluate the established design framework, but also to define, test and assess various fabrication and materialisation strategies, as well as actively controlled actuation principles. The first chapters provide a contextualisation of the topic within the larger architectural discourse and give an overview of the background which has influenced the presented research, including biomimetic architecture, compliant mechanisms and suitable materials. The section concludes with a presentation of current research challenges within the field of kinetic and adaptive building envelopes and introduces a series of sate of the art projects. Chapter three contains the publications about the development of the four demonstrator projects Flectofold, Flexafold, Arch(k)inetic and the ITECH Research Demonstrator 2018-19 and relevant investigations which built the basis for this thesis on the topic of bio-inspired compliant folding mechanisms. Chapter four and five conclude the thesis with a summary and critical reflection of the results, as well as the discussion of potential future developments within the topic of compliant mechanisms for adaptive building envelopes.Item Open Access Knoten für Tragkonstruktionen aus betongefülltem Faser-Kunststoff-Verbund, inspiriert von der Biomechanik pflanzlicher Verzweigungen : Sondierung einer neuen Bauweise für Tragknoten aus geflochtenem Textil und Beton(Stuttgart : Institut für Tragkonstruktionen und Konstruktives Entwerfen, Universität Stuttgart, 2020) Jonas, Florian, A.; Knippers, Jan (Prof. Dr.-Ing.)Item Open Access Design and monitoring of cold bent lamination-stabilised glass : investigated by applying fibre optic sensors(2015) Fildhuth, Thiemo; Knippers, Jan (Prof. Dr.-Ing.)Continuously curved, highly transparent façades or roofs are increasingly demanded in architecture. Regularly curved or free-form building envelope shapes represent a rapidly growing market field in construction and project design. For such transparent roof or façade claddings, the necessary durability, strength and safety require laminated safety glass as the principle material. Whereas the faceting of curved surfaces to apply planar glass elements is a frequently used cladding solution, the employment of curved glass modules permits a more precise, smooth achievement of curved envelopes. Recent improvements in the industrialised fabrication of curved glass render the use of such elements increasingly attractive. The two main, but different, production methods to shape these modules are the heat bending and cold bending of glass. Plastic heat bending results in a stable glass shape permitting high curvature. However, any potential optical surface bumps, any remaining irregular local interior stress from production and the limited applicability of toughened glass impose restrictions on the use of heat bent glass. In contrast, elastic cold bending only allows for low curvature but provides high optical surface quality and permits the unrestricted use of toughened glass. Stabilisation of the curved shape of cold bent glass without a retaining substructure can be achieved through the establishment of a shear compound of several elastically bent glass panes via lamination with polymeric interlayers. The bending stress remains in the glass. Despite the potential of this type of cold bent glass for construction purposes, comprehensive research approaches and the necessary stress- and shape-monitoring methods for glass laminates are lacking. Therefore, the characteristic properties and parameters influencing manufacture, the short- and long-term behaviour of cold bent glass, applicable numerical form-finding models and shape- and interior stress-monitoring methods have been investigated in the present work. The testing of real scale cold bent glass specimens with respect to displacement and stress permits the verification of the analyses. Close range photogrammetry has been applied to measure the three-dimensional shape and recovery behaviour of bent laminates. A new method for permanent real-time monitoring of the interior stress in the laminate by applying thin, barely visible, fibre-optical Bragg-grating sensors with transparent adhesive bonding has been developed. Fibre optical sensing has been examined and evaluated and is discussed as a possible monitoring system applicable to multi-layered glass units. Based on the accumulated modelling and testing results, information regarding the behaviour and the design of cold bent lamination-stabilised glass and the potential of fibre-optical monitoring for glass laminates is provided as a working basis in the conclusion to this work.Item Open Access Nature-inspired generation scheme for shell structures(2012) La Magna, Riccardo; Waimer, Frédéric; Knippers, JanAlthough less researched and put into practice in the building environment, pure plate structures are to be observed frequently in biological structures. The 3-plate principle which is common in the morphology and growth pattern of natural systems is also found to be of a structurally optimum content when considered from a plate point of view. This is for instance the case of the sea urchin’s plate skeleton morphology, which served as biological inspiration for the recently built ICD/ITKE Research Pavilion 2011 at the University of Stuttgart. The current paper will focus on the 3-plate principle and its mechanical features, also presenting study models to analyse the structural characteristics and advantages of the principle. Along with the theoretical background, the paper will introduce the structural concept of the pavilion, as well as the analysis methods used for its design and engineering.Item Open Access Form-finding of grid shells with continuous elastic rods(2011) Li, Jian-Min; Knippers, JanGrid shells with continuous elastic rods have the advantages to generate curved spaces with uniform members and joints. However, finding the boundary conditions, including the grid pattern and bearing positions, which lead to a specific geometry, is not an easy task. Designers have to keep equal grid lengths, minimise the residual forces and ensure the smoothness of geometries simultaneously. In this paper, we present a new numerical method which can derive the grid pattern and bearing positions in accordance with a desired geometry. This is done by finding the least strain energy state of the elastic grid in the solution domain defined by constraints. This method can provide architects a grid pattern that satisfies all the geometrical demands. At the same time, a structure with less strain energy is favoured by engineers. This is especially important for elastic grid shells, whose structural stability is largely affected by the residual forces.Item Open Access Toward reciprocal feedback between computational design, engineering, and fabrication to co-design coreless filament-wound structures(2024) Kannenberg, Fabian; Zechmeister, Christoph; Gil Pérez, Marta; Guo, Yanan; Yang, Xiliu; Forster, David; Hügle, Sebastian; Mindermann, Pascal; Abdelaal, Moataz; Balangé, Laura; Schwieger, Volker; Weiskopf, Daniel; Gresser, Götz T.; Middendorf, Peter; Bischoff, Manfred; Knippers, Jan; Menges, AchimItem Open Access Structural development of segmented timber shell systems(Stuttgart: Institut für Tragkonstruktionen und Konstruktives Entwerfen, Universität Stuttgart, 2025) Bechert, Simon; Knippers, Jan (Prof. Dr.-Ing.)In response to the growing global challenges of climate change, resource scarcity, and urbanisation, there is an increasing demand for sustainable and material-efficient building systems. Segmented timber shell systems offer a promising solution by combining modularity, structural lightness, and the efficient use of renewable materials with advanced digital design and fabrication technologies. This dissertation develops an integrative structural design methodology to advance segmented timber shells as viable solutions for large-span architecture. Chapter one introduces the research motivation and context, establishing the relevance of segmented timber shells as a future-oriented building system. Chapter two reviews the state of the art, tracing the evolution of shell structures and highlighting the potential of modular, lightweight timber construction within sustainable architecture. Segmented timber shells synergise these fields as a contemporary alternative in the context of an evolving built environment. Chapter three formulates three Research Objectives (ROs) addressing key challenges in the design, engineering, and construction of segmented timber shells. These objectives form the basis for the Research Methods (RM1-RM3) outlined in chapter four, which translate them into fundamental developments and innovations for integrative structural design of segmented timber shell systems. The core contributions are documented in peer-reviewed publications, each supported by full-scale demonstrators: the ITECH Research Demonstrator 2015-16, the Urbach Tower, the BUGA Wood Pavilion, and the livMatS Biomimetic Shell. Chapter five summarises these publications and their contributions to the overarching research framework. Chapter six discusses the research results (RR1-RR3), demonstrating the structural viability, life cycle performance, and industrial scalability of segmented timber shells. The work shows how interdisciplinary co-design, performance-driven structural assessment, and automated prefabrication strategies enable the realisation of modular, lightweight timber shell structures. Finally, chapter seven concludes with a critical reflection on the contributions and limitations of the research and outlines the future potential of segmented timber shells in large-scale architectural applications, bridging the gap between experimental research and construction practice.