Zechmeister, C., Gil Pérez, M., Knippers, J., & Menges, A. (2023). Concurrent, computational design and modelling of structural, coreless-wound building components. Automation in Construction
, 104889. https://doi.org/10.1016/j.autcon.2023.104889
AbstractCoreless filament winding extends established industrial processes, enabling the fabrication of building parts with minimal formwork. Since the part's final geometry is unknown until completed, it creates uncertainties for design and engineering. Existing architectural design workflows are insufficient, and industrial software packages cannot capture the complexity of self-deforming fibres to model complex fibre layups. This research introduces a feedback-based computational method conceived as four development cycles to design and evaluate fibre layups of large-scale architectural building components, and a multi-scalar digital-physical design and evaluation toolset to model and evaluate them at multiple resolutions. The universal applicability of the developed methods is showcased by two different architectural fibre structures. The results show how the systematization of methods and toolset allow for increased design flexibility and deeper integration of interdisciplinary collaborators. They constitute an important step towards a consolidated co-design methodology and demonstrate the potential to simultaneously co-evolve design and evaluation methods.
Ranjazmay Azari, M., Bemanian, M., Mahdavinejad, M., Körner, A., & Knippers, J. (2023). Application‑based principles of islamic geometric patterns; state‑of‑the‑art, and future trends in computer science/technologies: a review. Heritage Science
, ((2023) 11:22
AbstractCurrently, there is a tendency to use Islamic Geometric Patterns (IGPs) as important identities and cultural elements of building design in the Middle East. Despite high demand, lack of information about the potential of IGPs principles have led to formal inspiration in the design of existing buildings. Many research studies have been carried out on the principles of IGPs. However, comprehensive studies relating to new possibilities, such as structure-based, sustainablebased, and aesthetic-based purposes, developed by computer science and related technologies, are relatively rare. This article reviews the state-of-the-art knowledge of IGPs, provides a survey of the main principles, presents the status quo, and identifies gaps in recent research directions. Finally, future prospects are discussed by focussing on different aspects of the principles in accordance with collected evidence obtained during the review process.
Rihaczek, G., Klammer, M., Basnak, O., Köerner, A., La Magna, R., & Knippers, J. (2022). Timbr Foldr – A Design Framework and Material System for Closed Cross - Section Curved Folded Structures. Journal of the International Association for Shell and Spatial Structures
(4), Article 4. https://doi.org/10.20898/j.iass.2022.014
AbstractThis research investigated building components that can be produced and transported in a flat state and transformed to a spatial state without scaffolding on-site. Curved folding was employed to allow for a shape change between flat and spatial bending active structures. Bending generally allows for expressive curvature with simple flat production as well as easy customization. Limitations presented by laborious forming and upscaling of individually bent plates were overcome by large-scale curved folding.
The present research builds upon the context but adds a design framework for volumetric curved folded components, a bistable behavior, and comprehensive detailing regarding upscaling and increased structural capacity. The mechanism was studied on a kinematic level, considering geometrical rules of curved folding and
the design space. It was also studied on a kinetic level under the consideration of material properties specific to plywood. As a proof of concept, a 1:1 scale demonstrator was built. Finite element modeling software was used to optimize
the shape. The demonstrator was fabricated flat, folded up, and locked in its stable configuration by the bistability and bases. It supported twelve people with a self-weight of approximately 300kg.
AbstractStructural members made of fiber-reinforced polymers (FRP) attract increasing attention in the development of novel architectural systems that challenge the standard design methodologies. Cylindrical surfaces constitute one of the typical geometric sets obtained with the FRP component fabrication. This paper explores the influences of two geometric parameters on the buckling performance of elliptical cylinders: inverse slenderness (ratio of minimum diameter to height) and eccentricity (ratio of radii along semi-axes). The overall stiffness properties are defined using lamination parameters. This analysis method eliminates the dependency of optimal solutions on the initial assumptions regarding the laminate configuration, which needs to be explicitly described in multi-layer modeling. Finite element analyses are utilized to compute buckling loads of the cylinders under axial compression force and bi-axial bending moments. The optimal lamination parameters and buckling stresses are determined for various parameters, and the lamination parameters corresponding to the optimal and simple ±45° angle-ply design points are presented in the lamination parameter plane via Miki's diagram. The results reveal the level of performance that can be achieved by a specific geometry and provide guidelines for the optimal design of elliptical laminated cylinders against buckling.
Mindermann, P., Gil Pérez, M., Knippers, J., & Gresser, G. T. (2022). Investigation of the Fabrication Suitability, Structural Performance, and Sustainability of Natural Fibers in Coreless Filament Winding. Materials
(9), Article 9. https://doi.org/10.3390%2Fma15093260
AbstractCoreless filament winding is an emerging fabrication technology in the field of building construction with the potential to significantly decrease construction material consumption, while being fully automatable. Therefore, this technology could offer a solution to the increasing worldwide demand for building floor space in the next decades by optimizing and reducing the material usage. Current research focuses mainly on the design and engineering aspects while using carbon and glass fibers with epoxy resin; however, in order to move towards more sustainable structures, other fiber and resin material systems should also be assessed. This study integrates a selection of potential alternative fibers into the coreless filament winding process by adapting the fabrication equipment and process. A bio-based epoxy resin was introduced and compared to a conventional petroleum-based one. Generic coreless wound components were created for evaluating the fabrication suitability of selected alternative fibers. Four-point bending tests were performed for assessing the structural performance in relation to the sustainability of twelve alternative fibers and two resins. In this study, embodied energy and global warming potential from the literature were used as life-cycle assessment indexes to compare the material systems. Among the investigated fibers, flax showed the highest potential while bio-based resins are advisable at low fiber volume ratios.
Gil Pérez, M., Guo, Y., & Knippers, J. (2022). Integrative material and structural design methods for natural fibres filament-wound composite structures: The LivMatS pavilion. Material & Design
AbstractCoreless filament winding (CFW) is a novel fabrication technique that utilises fibre-polymer composite materials to efficiently produce filament wound structures in architecture while reducing manufacturing waste. Previous projects have been successfully built with glass and carbon fibre, proving their potential for lightweight construction systems. However, in order to move towards more sustainable architecture, it is crucial to consider replacing carbon fibre’s high environmental impact with other material systems, such as natural fibre. This paper evaluates several fibres, resin systems, and their required CFW fabrication adjustments towards designing and fabricating a bio-composite structure: the LivMatS Pavilion. The methods integrate structural design loops with material evaluation and characterisation, including small-scale and large-scale structural testing at progressive stages. The results demonstrate the interactive decision-making process that combines material characterisation with structural simulation feedback, leveraged to evaluate and optimise the structural design. The built pavilion is proof of the first successful coreless filament wound sustainable natural fibres design, and the developed methods and findings open up further research directions for future applications.
Knippers, J., & Menges, A. (2022). Robotische Fertigung als computerbasierte Planung für neue architektonische und konstruktive Perspektiven / Zwei Leichtbaupavillons demonstrieren lastangepasste und feingliedrige zukunftsorientierte neue Bausysteme. Der Prüfingenieur, 60, 36–43.
Gil Pérez, M., Früh, N., La Magna, R., & Knippers, J. (2022). Integrative structural design of a timber-fibre hybrid building system fabricated through coreless filament winding: Maison Fibre. Journal of Building Engineering, 49.
AbstractCoreless filament winding is a robotic fabrication technique in which conventional filament winding is modified to reduce the core material to its minimum. This method was showcased and developed through a series of pavilions demonstrating its potential to create lightweight structures. The latest project, Maison Fibre, goes one step further and adapts the fabrication into a hybrid structure combining fibre-polymer composites (FPC) with laminated veneer lumber (LVL) to allow for walkability. The result is the first multi-storey building system fabricated with this novel technique. During the integrative design process of the slab system, the optimum fibre layup was negotiated between the timber support span, load induction, boundary conditions, and material amount required. A total of four iterations of the hybrid component were load tested and compared with the maximum enveloped forces resulting from the global structural simulation. The full-scale load tests were used to calibrate the refined structural simulation of the slab components. The experimental process allowed for material reduction and validated the structural system's capability to withstand the design forces. In addition, the fibre layup was tailored and load adapted for the non-tested wall and slab components of the installation using the test results and achieving further material optimization. This publication describes the integrative design process of the hybrid slab system from initial concepts to the iterative optimization of the structural system, demonstrating its potential for future applications.
Guo, Y., Gil Pérez, M., Serhat, G., & Knippers, J. (2022). A design methodology for fiber layup optimization of filament wound structural components. Structures
, 1125–1136. https://doi.org/10.1016/j.istruc.2022.02.048
AbstractThe applications of fiber-reinforced polymer (FRP) composites extend rapidly along with the development of new manufacturing techniques. However, due to the complexities introduced by the material and fabrication processes, the application of conventional structural design methods for construction members has been significantly challenging. This paper presents an alternative methodology to find optimum fiber layups for a given tube-shape geometry via a graphical optimization strategy based on structural performance requirements. The proposed technique employs simplified shell element models based on classical lamination theory (CLT) to avoid explicit fiber modeling in the FEA simulations. Lamination parameters are utilized to generate the reduced stiffness matrices for continuous multi-layer FRP lamination. The fiber layup of the component is retrieved from the optimal lamination parameters that maximize the structural performance. The case study results demonstrate that the developed method provides compact solutions, linking the structural design requirements with optimal fiber orientations and volumetric proportions. In addition, the determined solutions can be interpreted directly by the winding fabrication settings.
Gil Pérez, M., Zechmeister, C., Kannenberg, F., Mindermann, P., Balangé, L., Guo, Y., Hügle, S., Gienger, A., Forster, D., Bischoff, M., Tarín, C., Middendorf, P., Schwieger, V., Gresser, G. T., Menges, A., & Knippers, J. (2022). Computational co-design framework for coreless wound fibre–polymer composite structures. Journal of Computational Design and Engineering
(2), Article 2. https://doi.org/10.1093/jcde/qwab081
AbstractIn coreless filament winding, resin-impregnated fibre filaments are wound around anchor points without an additional mould. The final geometry of the produced part results from the interaction of fibres in space and is initially undetermined. Therefore, the success of large-scale coreless wound fibre composite structures for architectural applications relies on the reciprocal collaboration of simulation, fabrication, quality evaluation, and data integration domains. The correlation of data from those domains enables the optimization of the design towards ideal performance and material efficiency. This paper elaborates on a computational co-design framework to enable new modes of collaboration for coreless wound fibre–polymer composite structures. It introduces the use of a shared object model acting as a central data repository that facilitates interdisciplinary data exchange and the investigation of correlations between domains. The application of the developed computational co-design framework is demonstrated in a case study in which the data are successfully mapped, linked, and analysed across the different fields of expertise. The results showcase the framework’s potential to gain a deeper understanding of large-scale coreless wound filament structures and their fabrication and geometrical implications for design optimization.
Suzuki, S., & Knippers, J. (2022). A Generic Particle Model with Topologic Modeling Capabilities for the Computational Form-Finding of Elastic Structures. Computer-Aided Design
AbstractRecent efforts on the research of bending- and tensile-active structures have shown the vast range of aesthetic and performative opportunities that elastic structures can offer for generating innovative architectural solutions. In this context, the task of conceptualizing and representing elastic structures is not trivial due to the presence of large deformations along the forming process. This condition demands to expand beyond current geometrical modeling schemes used in architecture and develop a more intuitive simulation-based design practice. Dynamic methods, such as Particle System and Dynamic Relaxation, have become an important topic on this subject with major efforts entirely focused on speeding up rates of numerical convergence. Fast simulations simplify the development of design iterations, but designers are still forced to break the integration process when topological changes need to be introduced for fulfilling a given design intention. As the exploration of elastic structures becomes more integrated within architectural design agendas, there is a growing necessity to introduce more flexible numerical models for design conceptualization. In this paper we introduce the conceptual framework for a generic Particle System model built on principles of combinatorial maps and graph theory that is designed to support topological transformations on the fly. The computational implementation of the proposed model is demonstrated with two types of data structures. The aim of this work is to enhance modeling capabilities when numerical simulations are used as design tools.
Mindermann, P., Gil Pérez, M., Kamimura, N., Knippers, J., & Gresser, G. T. (2022). Implementation of Fiber-Optical Sensors into Coreless Filament-Wound Composite Structures. Composite Structures
, 115558. https://doi.org/10.1016/j.compstruct.2022.115558
AbstractFiber-reinforced composite structures manufactured by coreless filament winding (CFW) are adaptable to the individual load case and offer high, mass-specific mechanical performance. However, relatively high safety factors must be applied due to the large deviations in the structural parameters. An improved understanding of the structural behavior is needed to reduce those factors, which can be obtained by utilizing an integrated fiber-optical sensor. The described methods take advantage of the high spatial resolution of a sensor system operating by the Rayleigh backscatter principle. The entire strain fields of several generic CFW samples were measured in various load scenarios, visualized in their spatial contexts, and analyzed by FEM-assisted methods. The structural response was statistically described and compared with the ideal load distribution to iteratively derive the actual load introduction and prove the importance of the sensor integration. The paper describes methods for the sensor implementation, interpretation and the calibration of structural data.
Krtschil, A., Orozco, L., Bechert, S., Wagner, H. J., Amtsberg, F., Chen, T.-Y., Shah, A., Menges, A., & Knippers, J. (2022). Structural development of a novel punctually supported timber
building system for multi-storey construction. Journal of Building Engineering
, 104972. https://doi.org/10.1016/j.jobe.2022.104972
AbstractThough capable of allowing multi-directional spans, timber products such as cross-laminated timber are primarily utilized uni-directionally using linear supports like walls or beam elements. Recent building designs increasingly show punctual supports but with narrow column grid layouts.
Support beams and narrow grids limit the design space for multi-storey timber buildings. To overcome these design limits, an integrative design concept for punctually supported timber slabs is being developed that allows for large spans and irregular column layouts. Therefore, engineering methods are integrated in the architectural design of the building components, such as plates, columns, and their connections. The developed slab system combines hardwood and softwood materials in a sandwich construction. The plates have a tailored internal topology considering the force flow in the slab. A plate-to-plate connection design is evaluated through
mechanical tests, which also serve as calibration for the global structural model. The research findings are validated through the design and construction of a large scale demonstrator: the ITECH Campus Lab.
Orozco, L., Krtschil, A., Skoury, L., Knippers, jan, & Menges, A. (2022). Arrangement of reinforcement in variable density timber slab systems for multi-story construction. International Journal of Architectural Computing
AbstractThe arrangement of columns and their spacing in multi-story timber construction is restricted to rectangular grids by the production and shipping sizes of floor assemblies. This is particularly true for hollow box floor systems, for which the punctual supports must be placed at the reinforced edges of the hollow boxes. The
arrangement of the columns and their spacing is thereby restricted by the production and shipping sizes of the box ceilings to rectangular grids. To overcome these design limits a new wooden box building system is developed that allows for irregular column layouts through a tailored slab interior design. This development allows for the increased applicability of timber floor systems regardless of site shape or architectural design intent. The slab interior design is dependent on occurring forces and fabrication requirements. Three methods for the internal slab layout are developed and compared: a sequential method, a structurally informed
agent-based method, and a geometrically informed agent-based method that uses both a sequential and agent-based approach. The structural performance of each method is compared through the analysis of three reinforcement layouts an architectural testing setup.
Sippach, T., Dahy, H., Uhlig, K., Grisin, B., Carosella, S., & Middendorf, P. (2021). Structural Optimization through biomimetic-inspired material-specific Application of plant-based Natural Fiber-Reinforced Polymer Composites (NFRP). Polymers
AbstractUnder normal conditions, the cross-sections of reinforced concrete in classic skeleton construction systems are often only partially loaded. This contributes to non-sustainable construction solutions due to an excess of material use. Novel cross-disciplinary workflows linking architects, engineers, material scientists and manufacturers could offer alternative means for more sustainable architectural applications with extra lightweight solutions. Through material-specific use of plant-based Natural Fiber-Reinforced Polymer Composites (NFRP), also named Biocomposites, a high-performance lightweight structure with topology optimized cross-sections has been here developed. The closed life cycle of NFRPs promotes sustainability in construction through energy recovery of the quickly generative biomass-based materials. The cooperative design resulted in a development that were verified through a 1:10 demonstrator, whose fibrous morphology was defined by biomimetically-inspired orthotropic tectonics, generated with by the fiber path optimization software tools, namely EdoStructure and EdoPath in combination with the appliance of the digital additive manufacturing technique: Tailored Fiber Placement (TFP).
Born, L., Möhl, C., Kannenberg, F., Melnyk, S., Jonas, F. A., Menges, A., Knippers, jan, & Gresser, G. T. (2021). Semi-automated braiding of complex, spatially branched FRP-structures. Composite Structures
, 114551. https://doi.org/10.1016/j.compstruct.2021.114551
AbstractIn building industries, branched load-bearing structures are used for defined load transfer and load distribution. While fiber-reinforced plastics are established as concrete formwork for straight segments, node geometries are less available. This is caused by the complex manufacturing process of spatially branched, three-dimensional textile preforms. There are only few productive textile processes for the manufacture that are attractive to industry, the most common is braiding. However, setting up the process, including programming the mandrel path through the braiding machine and adjusting the fiber placement, is very time consuming, making the process unattractive despite high productivity. This paper presents a new digitalized process workflow for the fabrication which simplifies the process preparation and thus could establish the braiding process for rapid fabrication of spatially branched, three-dimensional geometries. The digitalized workflow is validated by manufacturing a 4-arm node structure consisting of a concrete-filled CFRP in a scale relevant to the building industry.
Bechert, S., Aldinger, L., Wood, D., Knippers, J., & Menges, A. (2021). Urbach Tower: Integrative structural design of a lightweight structure made of self-shaped curved cross-laminated timber. Structures
, 3667--3681. https://doi.org/10.1016/j.istruc.2021.06.073
AbstractRecent development in research and practice for curved cross-laminated timber (CLT) opens up novel and interesting possibilities for applications of slender surface-active shell structures in architecture. Such typologies provide advantageous structural behaviour allowing for efficient and lightweight structures while simultaneously determine the envelope and space of a building. The high degree of prefabrication combined with a sustainable and renewable building material makes CLT an ecological and economic solution for future construction. This paper presents the design development and construction of the Urbach Tower for the Remstal Gartenschau 2019: a structure made from high curvature CLT components on a building scale. This research contribution illustrates a sophisticated integrative design to construction process emphasizing computational and structural design, fabrication and detailing for curved timber components in complex spatial structures. The authors further explore the structural potential of self-shaped curved CLT investigating the influence of curvature radius on the load-bearing behaviour of the tower structure. The Urbach Tower translates these technical developments into practice arising at the intersection of digital innovation and scientific research.
Mindermann, P., Rongen, B., Gubetini, D., Knippers, J., & Gresser, G. T. (2021). Material Monitoring of a Composite Dome Pavilion Made by
Robotic Coreless Filament Winding. Materials
, 5509. https://doi.org/10.3390/ma14195509
AbstractA hemispherical research demonstration pavilion was presented to the public from April to October 2019. It was the first large-scale lightweight dome with a supporting roof structure primarily made of carbon- and glass-fiber-reinforced composites, fabricated by robotic coreless filament winding. We conducted monitoring to ascertain the sturdiness of the fiber composite material of the supporting structure over the course of 130 days. This paper presents the methods and results of on-site monitoring as well as laboratory inspections. The thermal behavior of the pavilion was
characterized, the color change of the matrix was quantified, and the inner composition of the coreless wound structures was investigated. This validated the structural design and revealed that the surface temperatures of the carbon fibers do not exceed the guideline values of flat, black façades and that UV absorbers need to be improved for such applications.
Gil Pérez, M., Rongen, B., Koslowski, V., & Knippers, J. (2021). Structural design assisted by testing for modular coreless filament-wound composites: The BUGA Fibre Pavilion. Construction and Building Materials
AbstractThe BUGA Fibre Pavilion was built in 2019 in the Bundesgartenschau (National Gardening exhibition) at Heilbronn, Germany. The pavilion consists of modular fibre-polymer composite components made out of glass and carbon fibres with an epoxy resin matrix. The fabrication technique employed, called coreless filament winding (CFW), is a variant from conventional filament winding where the core is reduced to minimum frame support. The fibres are wound between these frames, freely spanning and creating the resulting geometry through fibre interaction. For the structural design of these components, conventional modelling and engineering methods were not sufficient as the system cannot be adequately characterized in the early stage. Therefore, a more experimental design approach is proposed for the BUGA Fibre Pavilion, where different levels of detailing and abstraction in the FE simulations are combined with prototyping and structural testing. This paper shows the procedure followed for the design and validation of the structural fibre components. In this process, the simulations are used as a design tool rather than a way to predict failure, while mechanical testing served for the verification and validation of the structural capacity.
Knippers, J., Kropp, C., Menges, A., Sawodny, O., & Weiskopf, D. (2021). Integrative computational design and construction: Rethinking architecture digitally. Civil Engineering Design
AbstractIncreasing the construction capacity, while at the same time significantly reducing harmful emissions and consumption of nonrenewable resources, and still providing a liveable and affordable built environment, provides a great challenge for future construction. In order to achieve this, both the productivity of construction processes and the energy and resource efficiency of construction systems have to be improved in a reciprocal process. Digital technologies make it possible to address these challenges in novel ways. The vision of this Cluster of Excellence IntCDC at the University of Stuttgart and the Max Planck Institute for Intelligent Systems is to harness the full potential of digital technologies to rethink design and construction based on integration and interdisciplinarity, with the goal of laying the methodological foundations to profoundly modernize the design and construction process and related building systems by adopting a systematic, holistic and integrative computational approach. One key objective is to develop an overarching methodology of “co-designing” methods, processes and systems based on interdisciplinary research encompassing architecture, structural engineering, building physics, engineering geodesy, manufacturing and systems engineering, computer science and robotics, and humanities and social sciences. In this way, the Cluster aims to address the ecological, economic and social challenges and to provide the prerequisites for a high-quality and sustainable built environment and a digital building culture.
Mühlich, M., Gonzalez, E. A., Born, L., Körner, A., Schwill, L., Gresser, G. T., & Knippers, J. (2021). Deformation Behavior of Elastomer-Glass Fiber-Reinforced Plastics in Dependence of Pneumatic Actuation. Biomimetics
, 6(3), 43
, Article 6(3), 43. https://doi.org/10.3390/biomimetics6030043
AbstractThis paper aims to define the influencing design criteria for compliant folding mechanisms with pneumatically actuated hinges consisting of fiber-reinforced plastic (FRP). Through simulation and physical testing, the influence of stiffness, hinge width as well as variation of the stiffness, in the flaps without changing the stiffness in the hinge zone, was evaluated. Within a finite element model software, a workflow was developed for simulations, in order to infer mathematical models for the prediction of mechanical properties and the deformation behavior as a function of the aforementioned parameters. In conclusion, the bending angle increases with decreasing material stiffness and with increasing hinge width, while it is not affected by the flap stiffness itself. The defined workflow builds a basis for the development of a predictive model for the deformation behavior of FRPs.
Knippers, J., Kropp, C., Menges, A., Sawodny, O., & Weiskopf, D. (2021). Integratives computerbasiertes Planen und Bauen: Architektur digital neu denken. Bautechnik
, 194–207. https://doi.org/10.1002/bate.202000106
AbstractDie Herausforderung an das Bauen der Zukunft besteht darin, mehr zu bauen, dabei weniger Schadstoffe zu emittieren und weniger endliche Ressourcen zu verbrauchen und trotzdem eine qualitätsvolle und lebenswerte gebaute Umwelt zu schaffen. In einem sich wechselseitig beeinflussenden Prozess müssen hierfür sowohl die Produktivität der Bauprozesse als auch die Energie‐ und Ressourceneffizienz der Bausysteme verbessert werden. Digitale Technologien bieten neue Lösungsansätze für diese Herausforderungen.
Ziel des Exzellenzclusters IntCDC an der Universität Stuttgart und dem Max‐Planck‐Institut für Intelligente Systeme ist es, das volle Potential digitaler Technologien zu nutzen, um das Planen und Bauen in einem integrativen und interdisziplinären Ansatz neu zu denken und damit die methodischen Grundlagen für eine umfassende Modernisierung des Bauschaffens zu legen. Eine zentrale Zielsetzung ist die Entwicklung einer übergeordneten Methodologie des „Co‐Design“ von Methoden, Prozessen und Systemen, basierend auf interdisziplinärer Forschung zwischen den Bereichen Architektur, Bauingenieurwesen, Ingenieurgeodäsie, Produktions‐ und Systemtechnik, Informatik und Robotik sowie Geistes‐ und Sozialwissenschaften. So sollen Lösungswege für die ökologischen, ökonomischen und sozialen Herausforderungen aufgezeigt und die Voraussetzungen für eine qualitätsvolle, lebenswerte und nachhaltige gebaute Umwelt sowie für eine digitale Baukultur geschaffen werden.
Früh, N., & Knippers, J. (2021). Multi-stage filament winding: Integrative design and fabrication method for fibre-reinforced composite components of complex geometries. Composite Structures
AbstractThe multi-stage filament winding (MSFW) method enables the sustainable production of lightweight fibre composites with complex geometries. Double curved components, even with undercuts, are analysed and concave areas which are not suitable for filament winding are replaced by convex temporary geometries.
Permanent and temporary mandrel parts are combined for the stage-based fabrication method. The sand composites developed for MSFW mandrels can be washed out using water. The sand can be reused. This paper introduces the fabrication method, presents the status of the research, and focuses on the geometry generation algorithm of the integrative design process.
Bechert, S., Sonntag, D., Aldinger, L., & Knippers, J. (2021). Integrative structural design and engineering methods for segmented timber shells : BUGA Wood Pavilion. Structures
(December), Article December. https://doi.org/10.1016/j.istruc.2021.10.032
AbstractThe presented research describes the holistic development of a modular lightweight timber shell. So-called segmented timber shells approximate curved geometries with the use of planar plates, thus combining the excellent structural performance of double curved shells with the resource-efficient prefabrication of timber modules using only planar elements. Segmented timber shells constitute a novel building system that demands for innovative approaches on structural design and construction technologies. The geometric complexity of plate shells in conjunction with the particularities of the building material wood pose great challenges to the computational design and planning processes as structural requirements and fabrication constraints determine the shell design at early design phases. This paper discusses the design development and construction of the BUGA Wood Pavilion: A segmented timber shell structure made of hollow cassette components. Particular
emphasis lies on the technical challenges of the employed building system, notably structural design and analysis, detailing solutions and the construction process. The authors further describe the integrative structural design and optimization methods developed for the timber shell in question. The BUGA Wood Pavilion demonstrates
the possibilities of lightweight and sustainable wood architecture merging the merits of integrative design, structural engineering and high-tech robotic fabrication methods.
Körner, A., Born, L., Bucklin, O., Suzuki, S., Vasey, L., Gresser, G. T., Menges, A., & Knippers, J. (2020). Integrative design and fabrication methodology for bio-inspired folding mechanisms for architectural applications. Computer-Aided Design
AbstractAdaptive shading devices are of special interest in the context of global need for reducing greenhouse gas emissions. To reduce mechanical complexity of kinetic architectural applications, the investigation of bio-inspired compliant mechanisms has proven to be a promising approach.
Thus, a coherent integrative design framework for bio-inspired kinetic folding mechanisms has been developed. This includes the abstraction process of biological principles, such as kinematic behaviours, actuation, as well as materialisation principles. A computational design and simulation model is built to analyse the kinematic and kinetic behaviour of the abstracted biological principles under consideration of specific materialisation and fabrication parameters and constraints. The design and simulation model builds the basis for an automated fabrication process, as well as for interaction and active control of the physical application. The development of the ITECH Research Demonstrator 2018-19, a large-scale compliant folding mechanism, inspired by the folding behaviour ladybug wings (Coleptera coccinellidae), serves as a case study of the developed process. The folding motion of the demonstrator is facilitated by distinct elastic hinge-zones with integrated pneumatic actuators.
Rihaczek, G., Klammer, M., Basnak, O., Petrs, J., Grisin, B., Dahy, H., Carosella, S., & Middendorf, P. (2020). Curved Foldable Tailored Fiber Reinforcements for Moldless Customized Bio-Composite Structures. Proof of Concept: Biomimetic NFRP Stools. Polymers
(9), Article 9. https://doi.org/10.3390/polym12092000
AbstractFiber Reinforced Polymers (FRPs) are increasingly popular building materials, mainly because of their high strength to weight ratio. Despite these beneficial properties, these composites are often fabricated in standardized mass production. This research aims to eliminate costly molds in order to simplify the fabrication and allow for a higher degree of customization. Complex three-dimensional shapes were instead achieved by a flat reinforcement, which was resin infused and curved folded into a spatial object before hardening. Structural stability was gained through geometries with closed cross-sections. To enable this, the resource-saving additive fabrication technique of tailored fiber placement (TFP) was chosen. This method allowed for precise fibers’ deposition, making a programmed anisotropic behavior of the material possible. Principles regarding the fiber placement were transferred from a biological role-model. Five functional stools were produced as demonstrators to prove the functionality and advantages of the explained system. Partially bio-based materials were applied to fabricate the stool models of natural fiber-reinforced polymer composites (NFRP). A parametric design tool for the global design and fiber layout generation was developed. As a result, varieties of customized components can be produced without increasing the design and manufacturing effort
Mader, A., Langer, M., Knippers, J., & Speck, O. (2020). Learning from plant movements triggered by bulliform cells: the biomimetic cellular actuator. Journal of the Royal Society Interface
AbstractWithin the framework of a biomimetic top-down approach, our study started with the technical question of the development of a hinge-free and compliant actuator inspired by plant movements. One meaningful biological concept generator was the opening and closing movements of the leaf halves of grasses. Functional morphological investigations were carried out on the selected model plant Sesleria nitida. The results formed the basis for further clarifying the functional movement principle with a particular focus on the role of turgor changes in bulliform cells on kinetic amplification. All findings gained from the investigations of the biological model were incorporated into a finite-element analysis, as a prerequisite for the development of a pneumatic cellular actuator. The first prototype consisted of a row of single cells positioned on a plate. The cells were designed in such a way that the entire structure bent when the pneumatic pressure applied to each individual cell was increased. The pneumatic cellular actuator thus has the potential for applications on an architectural scale. It has subsequently been integrated into the midrib of the facade shading system Flectofold in which the bending of its midrib controls the hoisting of its wings.
Menges, A., & Knippers, J. (2020). Wahrzeichen aus selbstgeformtem Holz. Dach + Holzbau - das Profimagazin für Dachdecker und Zimmerer, 34–39.
Costalonga Martins, V. anessa, Cutajar, S., van der Hoven, C., Baszyński, P., & Dahy, H. (2020). FlexFlax Stool: Validation of Moldless Fabrication of Complex Spatial Forms of Natural Fiber-Reinforced Polymer (NFRP) Structures through an Integrative Approach of Tailored Fiber Placement and Coreless Filament Winding Techniques. Applied Sciences
(9), Article 9. https://doi.org/10.3390/app10093278
AbstractIt has become clear over the last decade that the building industry must rapidly change to meet globally pressing requirements. The strong links between climate change and the environmental impact of architecture mean an urgent necessity for alternative design solutions. In order to propose them in this project, two emergent fabrication techniques were deployed with natural fiber-reinforced polymers (NFRPs), namely tailored fiber placement (TFP) and coreless filament winding (CFW). The approach is explored through the design and prototyping of a stool, as an analogue of the functional and structural performance requirements of an architectural system. TFP and CFW technologies are leveraged for their abilities of strategic material placement to create high-performance differentiated structure and geometry. Flax fibers, in this case, provide a renewable alternative for high-performance yarns, such as carbon, glass, or basalt. The novel contribution of this project is exploring the use of a TFP preform as an embedded fabrication frame for CFW. This eliminates the complex, expensive, and rigid molds that are traditionally associated with composites. Through a bottom-up iterative method, material and structure are explored in an integrative design process. This culminates in a lightweight FlexFlax Stool design (ca. 1 kg), which can carry approximately 80 times its weight, articulated in a new material-based design tectonic.
Neuhaus, R., Zahiri, N., Petrs, J., Tahouni, Y., Siegert, J., Kolaric, I., Dahy, H., & Bauernhansl, T. (2020). Integrating Ionic Electroactive Polymer Actuators and Sensors into Adaptive Building Skins : Potentials and Limitations. Frontiers in Built Environment
, 95. https://doi.org/10.3389/fbuil.2020.00095
Gil Pérez, M., Rongen, B., Koslowski, V., & Knippers, J. (2020). Structural design, optimization and detailing of the BUGA fibre pavilion. International Journal of Space Structures
(4), Article 4. https://doi.org/10.1177/0956059920961778
AbstractThe BUGA fibre pavilion built in April 2019 at the Bundesgartenschau in Heilbronn, Germany, is the most recent coreless fibre winding research pavilion developed from the collaboration between ICD/ITKE at the University of Stuttgart. The research goal is to create lightweight and high-performance lattice composite structures through robotic fabrication. The pavilion is composed of 60 carbon and glass fibre components, and is covered by a prestressed ethylene tetrafluoroethylene (ETFE) membrane. Each of the components is hollow in section and bone-like in shape. They are joined through steel connectors at the intersecting nodes where the membrane is also supported through steel poles. The components are fabricated by coreless filament winding (CFW), a technique where fibre filaments impregnated with resin are wound freely between two rotating scaffolds by a robotic arm. This novel structural system constitutes a challenge for the designer when proving and documenting the load-carrying capacity of the design. This paper outlines and elaborates on the core methods and workflows followed for the structural design, optimization and detailing of the BUGA fibre pavilion.
Born, L., Körner, A., Mader, A., Schieber, G., Milwich, M., Knippers, J., & Gresser, G. T. (2019). Adaptive FRP Structures For Exterior Applications. Advanced Materials Letters
(12), Article 12. https://doi.org/10.5185/amlett.2019.0029
AbstractRegarding modern, daylight-flooded buildings with large window façades, appropriate shading systems to improve the energy consumption of climate controlling systems are becoming more relevant. Building envelopes contribute largely to the temperature control and should be at best installed on the outside to prevent the interior from heating up. Preferably, those systems work with minimum maintenance and maximum robustness, covering as much of the window area as possible. Previous shading systems were mostly based on rigid-body mechanisms using error-prone joints. Components, whose movability is achieved by a local compliance of the material, offer a way to avoid the usage of mechanical joints. Within this paper, a new fiber-reinforced plastic (FRP) façade shading demonstrator called “Flexafold” is presented. Its opening and closing movement are controlled by pneumatic cushions which are integrated directly into the laminate set-up. The Flexafold shows thereby the possibility of producing self‑supporting, adaptive FRP components whose actuators are integrated into the component and thus protected in exterior applications. The functional principles and components of Flexafold, e.g. the locally compliant FRP material, the folding pattern and the integrated actuator system, are explained within this paper. Furthermore, a comparison to existing adaptive façade shading systems “flectofin®” and “Flectofold” is given.
Menges, A., & Knippers, J. (2019). Urbach Turm – Architektonische Landmarke aus selbstgeformtem Holz. Deutsche Bauzeitschrift DBZ, 52 – 55.
Mader, A., Born, L., Körner, A., Schieber, G., Masset, P.-A., Milwich, M., Gresser, G. T., & Knippers, J. (2019). Bio-inspired integrated pneumatic actuation for compliant fiber-reinforced plastics. Composite Structures
, Article 111558. https://doi.org/10.1016/j.compstruct.2019.111558
AbstractCompliant mechanisms of fiber-reinforced plastic (FRP) have been developed to reduce the mechanical complexity of kinetic systems. In a further step, pneumatic actuation was integrated into the set-up of the FRP, offering lightweight, slender, and inconspicuous actuation. Inflation of an integrated cushion causes rotation through the asymmetric material lay-up. Inspiration from the ultrastructure of pressurized veins in arthropod wings has led to the development of a thin layer of elastomer surrounding this pneumatic cushion to avoid delamination. T-peel tests revealed that the elastomer forms a higher adhesion to itself than to glass-fiber-reinforced plastic (GFRP) layers with an epoxy matrix. The angle-pressure relationship for specific GFRP samples with a defined compliant hinge zone was investigated physically and numerically, showing good consistency between the two. Further, a mathematical model, taking into account the bending stiffness of the cushion-surrounding FRP layers, was developed, and a parametric study was conducted on the actuation angles.
Solly, J., Früh, N., Saffarian, S., Aldinger, L., Margariti, G., & Knippers, J. (2019). Structural design of a lattice composite cantilever. Structures
, Vol. 18
, 28–40. https://doi.org/10.1016/j.istruc.2018.11.019
AbstractThe ICD/ITKE Research Pavilion 2016/2017 is the most recent in the series of experimental building demonstrators developed by the Institute for Computational Design (ICD) and the Institute for Building Structures and Structural Design (ITKE) at the University of Stuttgart. The completed structure is a 12 m long cantilevering lattice-composite shell that was wound in one piece by a multi-machine fabrication system using coreless filament winding. To realise such a structure through this fabrication process involved a negotiation between architectural design, structural requirements and fabrication constraints. The structural design process was divided into two steps. A shell model was used to evaluate possible geometries in the initial negotiation between architectural design and fabrication constraints. In order to approximate the highly anisotropic material behaviour of fibre reinforced polymers, substitute material properties had to be determined in physical tests. In the second step the actual fibre layup was analysed using a detailed beam-element model. The main load bearing fibre bundles were directly analysed in cross section and position. As-built and intended geometry were constantly compared and the feedback was used to refine the finite element analysis during fabrication. This paper covers the aspects mentioned and gives an outlook on further possibilities of this design and fabrication approach.
Dahy, H. (2019). Materials as a Design Tool’ Design Philosophy Applied in Three Innovative Research Pavilions Out of Sustainable Building Materials with Controlled End-Of-Life Scenarios. Buildings
(3), Article 3. https://doi.org/10.3390/buildings9030064
AbstractChoosing building materials is usually the stage that follows design in the architectural design process, and is rarely used as a main input and driver for the design of the whole building’s geometries or structures. As an approach to have control over the environmental impact of the applied building materials and their after-use scenarios, an approach has been initiated by the author through a series of research studies, architectural built prototypes, and green material developments. This paper illustrates how sustainable building materials can be a main input in the design process, and how digital fabrication technologies can enable variable controlling strategies over the green materials’ properties, enabling adjustable innovative building spaces with new architectural typologies, aesthetic values, and controlled martial life cycles. Through this, a new type of design philosophy by means of applying sustainable building materials with closed life cycles is created. In this paper, three case studies of research pavilions are illustrated. The pavilions were prefabricated and constructed from newly developed sustainable building materials. The applied materials varied between structural and non-structural building materials, where each had a controlled end-of-life scenario. The application of the bio-based building materials was set as an initial design phase, and the architects here participated within two disciplines: once as designers, and additionally as green building material developers. In all three case studies, Design for Deconstruction (DfD) strategies were applied in different manners, encouraging architects to further follow such suggested approaches.
Dahy, H. (2019, February 12). Natural Fibre-Reinforced Polymer Composites (NFRP) Fabricated from Lignocellulosic Fibres for Future Sustainable Architectural Applications, Case Studies: Segmented-Shell Construction, Acoustic Panels, and Furniture
(No. 3). Sensors. https://doi.org/doi: 10.3390/s19030738
AbstractDue to the high amounts of waste generated from the building industry field, it has become essential to search for renewable building materials to be applied in wider and more innovative methods in architecture. One of the materials with the highest potential in this area is natural fibre-reinforced polymers (NFRP), which are also called biocomposites, and are filled or reinforced with annually renewable lignocellulosic fibres. This would permit variable closed material cycles’ scenarios and should decrease the amounts of waste generated in the building industry. Throughout this paper, this discussion will be illustrated through a number of developments and 1:1 mockups fabricated from newly developed lignocellulosic-based biocomposites from both bio-based and non-bio-based thermoplastic and thermoset polymers. Recyclability, closed materials cycles, and design variations with diverse digital fabrication technologies will be discussed in each case. The mock-ups’ concepts, materials’ compositions, and fabrication methods are illustrated. In the first case study, a structural segmented shell construction is developed and constructed. In the second case study, acoustic panels were developed. The final case studies are two types of furniture, where each is developed from a different lignocellulosic-based biocomposite. All of the presented case studies show diverse architectural design possibilities, structural abilities, and physical building characteristics.
Schieber, G., Born, L., Bergmann, P., Körner, A., Mader, A., Saffarian, S., Betz, O., Milwich, M., Gresser, G. T., & Knippers, J. (2018). Hindwings of insects as concept generator for hingeless foldable shading systems. Bioinspiration & Biomimetics
(1), Article 1. https://doi.org/10.1088/1748-3190/aa979c
AbstractHingeless shading systems inspired by nature are increasingly the focus of architectural research. In contrast to traditional systems, these compliant mechanisms can reduce the amount of maintenanceintensive parts and can easily be adapted to irregular, doubly curved, facade geometries. Previousmechanisms rely merely on the reversible material deformation of composite structures with almost homogeneous material properties. This leads to large actuation forces and an inherent conflict between the requirements of movement and the capacity to carry external loads. To enhance the performance of such systems, current research is directed at natural mechanisms with concentrated compliance and distinct hinge zones with high load-bearing capacity. Here, we provide insights into our biological findings and the development of a deployable structure inspired by the Flexagon model of hindwings of insects in general and the hierarchical structure of the wing cuticle of the shield bug (Graphosoma lineatum). By using technical fibre-reinforced plastics in combination with an elastomer foil, natural principles have been partially transferred into a multi-layered structure with locally adapted stiffness. Initial small prototypes have been produced in a vacuum-assisted hot press and sustain this functionality. Initial theoretical studies on test surfaces outline the advantages of these bio-inspired structures as deployable external shading systems for doubly curved facades.
Früh, N., Amorth, A., & Wieland, T. (2018). Holzbau-Formen für Stuttgart 21 – Modellbasierte Entwicklung und Fertigung eines Schalungssystems aus Brettsperrholz zur Herstellung von Schalentragwerken aus Stahlbeton. Bautechnik, (95), 505–511.
AbstractDie Realisierung von Schalentragwerken aus Stahlbeton ist anspruchsvoll. Hohe Anforderungen an Planung und Ausführung sowie damit verbundene Kosten führen dazu, dass diese Tragwerkstypologie nur selten realisiert wird. Der Artikel beschreibt das Schalungssystem, das beim Bau des zukünftigen Stuttgarter Hauptbahnhofs zum Einsatz kommt. Zahlreiche Anforderungen führten zu der Entwicklung von massiven Brettsperrholzbauteilen, deren Oberfläche mit faserverstärktem Kunststoff beschichtet wird. Die Fertigung der Bauteile erfolgt in mehreren Stufen. Nach der Herstellung von Brettsperrholzrohlingen werden aus mehreren Schichten Rohkörper zusammengesetzt. Die Formgebung erfolgt in zwei Schritten. Mit einer Plattenbearbeitungsanlage werden die Konturen der einzelnen Schichten gefräst. Die endgültige Form wird von einem Industrieroboter herausgearbeitet. Nach der Beschichtung wird die Form der Bauteile mithilfe eines Laser‐Scanners verifiziert. Alle Prozesse während Planung und Fertigung der Schalungselemente sind weitgehend modellbasiert. Mit dem entwickelten Schalungssystem wurden die ersten Elemente des Schalentragwerks aus Weißbeton bereits erfolgreich betoniert.
AbstractIn previous studies, it was demonstrated that the geometry of regular anticlastic membrane structures attached to edge beams on all four sides of the membrane is one of the most influential factors for the performance of the structure. However, regular anticlastic membranes are not easy to apply at specific design sites. For this reason, a greater degree of irregularity is introduced in this study to create a wider range of design possibilities. From the regular-shaped fabric panels that are symmetric about the two axes, one of the symmetries is removed. In this way, two new parameters are introduced: asymmetry about the transverse axis creating trapezoid-shaped panels, and asymmetry about the longitudinal axis creating inclined panels. These two types of panel parametric studies are the scope of this work. From findings of case studies of irregular anticlastic membrane structures with asymmetry about one or both axes, design aid charts and design equations for trapezoid-shaped and inclined panels are proposed that would be needed at the preliminary design phase.
Horn, R., Dahy, H., Gantner, J., Speck, O., & Leistner, P. (2018). Bio-Inspired Sustainability Assessment for Building Product Development—Concept and Case Study”, Sustainability. Sustainability, Special Issue “Sustainable Construction,” 10(1)
(130), Article 130. https://doi.org/10.3390/su10010130
AbstractTechnological advancement culminating in a globalized economy has brought tremendous improvements for mankind in manifold respects but comes at the cost of alienation from nature. Human activities nowadays are unsustainable and cause severe damage especially in terms of global depletion and destabilization of natural systems but also harm its own social resources.
In this paper, a sustainability assessment method is developed based on a bio-inspired sustainability framework that has been developed in the project TRR 141-C01 “The biomimetic promise”. It is aims at regaining the advantages of societal embeddedness in its environment through biological inspiration. The method is developed using a structured approach including requirement specification, description of the inventory models on bio-inspiration and sustainability assessment, creation of a bio-inspired sustainability assessment model and its validation. It is defined as an accompanying assessment for decision support, using a six-fold two-dimensional structure of social, economic and environmental functions and burdens. The method is applied and validated in 6 projects of TRR 141 and its applicability is exemplarily shown by the assessment of “Bio-flexi”, a biobased and biodegradable natural fiber reinforced plastic composite for indoor cladding applications. Based on the findings of the application the assessment method itself is proposed to be advanced towards an adaptive structure and a consequent outlook is provided.
Menges, A., & Knippers, jan. (2017). Architektonisches Potential tragender Faserverbundstrukturen. Deutsche Bauzeitschrift DBZ, 64 – 69.
Suzuki, S., & Knippers, J. (2017). ElasticSpace: A computational framework for interactive form-finding of textile hybrid structures through evolving topology networks. International Journal of Parallel, Emergent and Distributed Systems, Vol. 32, 11/2017
, Vol 32
(1), Article 1. https://doi.org/10.1080/17445760.2017.1390101
AbstractTextile Hybrid Structures are a novel type of structural system referring to the coupling of tensile form- and bending-active components into a stiffer construct. For form finding its static equilibrium shape, several computational frameworks built upon the Dynamic Relaxation method have been developed for the interactive exploration of material and geometric properties. However, efforts are still required when addressing dynamic alterations of topology without completely resetting the simulation. The main problem to face is the dynamic alteration of topological data without losing consistency of connectivity. In this paper, we present the development of a computational framework for form-finding textile hybrid structures which enables dynamic explorations of complex topological configurations during solver’s execution. A so-called evolving network formulation used to model mutable assemblies of interconnected particles is presented as well as the numerical scheme adopted to find the equilibrium state of such structures. The implementation of the framework is further described through the development of ElasticSpace, an interactive form finding tool for textile hybrid structures built with Java.
Dahy, H. (2017). Biocomposite materials based on annual natural fibres and biopolymers – Design, fabrication and costumized applications in architecture. Construction and Building Materials, 147, Article 147.
AbstractNatural fibres retrieved from annual agricultural by-products offer diverse advantages, when applied as a main ingredient in biocomposite building materials. These fibres, such as straw and other non-wood fibres are annually renewable and are worldwide available having the lowest cost, in comparison to other natural fibres available in the industrial fibre market. In this paper, the author presents three case studies of natural fibre reinforced polymers (NFRP), discussing the agro-fibre densification, different architectural designs for customized applications and fabrication stages. The natural fibres were compounded with three different biopolymers: a thermoplastic, a thermoset and an elastic thermoplastic one. This allowed variations in the final designs and geometries that can be reached, but caused a necessity of changing the fabrication technique in each case accordingly. To prove the applicability of the developed products, mechanical properties and environmental assessment were analyzed.
Gil Pérez, M., Kim, S. D., & Kang, T. H.-K. (2017). Development of design aid for barrel vault shaped membrane fabric structures. Journal of Structural Integrity and Maintenance
(1), Article 1. https://doi.org/10.1080/24705314.2017.1280592
AbstractThis study introduces the development of membrane fabric structures as well as the procedure for their design and analysis along with an explanation of the finite element modeling and conditions considered. In addition, a parametric study on regular barrel vault shaped membranes supported between arches is conducted. The following three parameters determine the geometry of this type of membranes: the arch curvature, the width of the panel, and the scale of the arch. Considering these three parameters and the different combinations among them, regular membrane panels are analyzed leading to the development of a design aid for this type of membranes.
Knippers, J., & Menges, A. (2017). Einblicke in die Ideenwelt des Stuttgarter Instituts für Tragkonstruktionen und Konstruktives Entwerfen: Mit bionisch inspirierten Faserverbundkonstruktionen können ganz neue Tragstrukturen realisiert werden. Der Prüfingenieur, 5/2017, Article 5/2017.
Knippers, J. (2017). Frei Otto. Bauingenieur, Jahresausgabe 2017/18, 149 – 153.
Sonntag, D., Bechert, S., & Knippers, J. (2017). Biomimetic timber shells made of bending-active segments. International Journal of Space Structures, Vol. 32((3-4)), Article (3-4).
AbstractIn the research field of segmented timber shells, two construction systems have lately received much attention, which both expose interesting structural and constructional characteristics: planar plate structures made of thin plywood and actively bent plywood structures. The research presented in this article combines elements of both approaches, resulting in a construction system for segmented shell structures with elastically bent elements. The increasing complexity of this approach requires a sophisticated design process, which integrates fabrication constraints as well as structural feedback. As a consequence, form-finding strategies of bending-active timber shells are discussed, with a special focus on the programming of the stiffness distribution in order to fulfil geometrical requirements. The authors also reflect on the specific structural challenges of joining thin sheets of plywood by transferring traditional textile connection methods to timber construction. Investigations of biological role models such as the sand dollar led to transfers of constructional principles on different levels. The resulting construction system was validated through the design and construction of a full-scale architectural prototype
Jonas, F. A., & Knippers, J. (2017). Tragverhalten von Betondruckgliedern mit Umschnürung durch geflochtene und gewickelte Carbonrohre: Tragfähigkeitssteigerung durch Aktivierung eines mehraxialen Spannungszustands im Beton. Beton- und Stahlbetonbau, 517 – 529.
AbstractDie Tragfähigkeit von Betondruckgliedern, wie Stützen im Hochbau, kann durch eine Umschnürung gesteigert werden. Dies erlaubt reduzierte Querschnittsabmessungen, geringeres Gewicht der Bauteile sowie einen Geschoßflächengewinn bei gleichem Traglastniveau. Es werden Untersuchungen zum Tragverhalten an unbewehrten, umschnürten Betonzylindern mit Querschnittdimensionen, die an gängige Hochbaustützen heranreichen, vorgestellt. Gewickelte und erstmals geflochtene Rohre aus kohlefaserverstärktem Kunststoff dienen als Umschnürungen. Durch den Einsatz der Hülle als verlorene Schalung kann auch der Bauablauf im Vergleich zu konventionell geschalten Stützen verbessert werden.
Das gewählte Steifigkeitsverhältnis des Kerns zur Hülle führt zu einem mehraxialen Spannungszustand, durch den die Druckfestigkeit von Beton gegenüber der einachsigen Beanspruchbarkeit erheblich gesteigert werden kann. Für die Auslegung werden deshalb aktuelle Bemessungsmodelle für gewickelte Umschnürungen angewendet und ausgewertet. Anhand von Druckversuchen an je drei gewickelten und geflochtenen, mit CFK umschnürten Betonzylindern sowie an Betonreferenzprüfkörpern werden Last‐Verformungskurven in Axial‐ und Umfangsrichtung ermittelt. Die mechanischen Eigenschaften der CFK‐Umschnürung werden anhand eines Split‐Disk‐Tests geprüft. Ergebnisse aus analytischen Modellen werden den experimentellen gegenübergestellt und diskutiert.
Knippers, J. (2017). The Limits of Simulation: Towards a New Culture of Architectural Engineering. Technology, Architecture + Design, Vol. 1(Issue 2), Article Issue 2.
AbstractComputational design and fabrication are at the focus of advanced practice and research in architecture. They allow for local differentiation of building components that enable buildings that were unthinkable a few years earlier. However, to fully exploit the potential of computational fabrication, a new paradigm in engineering is necessary. Today, the quantitative prediction of integrity by calculation of stresses and deformations is conceived as an indispensable prerequisite for any building construction. However, each simulation is only valid within certain boundary conditions, often not able to cope with advanced material systems. This paper discusses the need for alternative engineering strategies including integrated monitoring and physical testing in the design process to overcome the limitations of simulation.
Dahy, H. (2017). Efficient fabrication of sustainable building products from annually generated non-wood cellulosic fibres and bioplastics with improved flammability resistance. Waste Biomass Valor
, 1–9. https://doi.org/DOI: 10.1007/s12649-017-0135-3
AbstractCellulosic fibres retrieved from annual agricultural by-products offer diverse advantages when applied as a main ingredient in biocomposite building materials. Within this paper work, the application possibility of non-wood straw fibres in innovative building products is highlighted. Fabrication efficiency is reached here through reducing the number of industrial processes and additives needed to manufacture the final biocomposite products. The natural mineral contents of the straw selected (rice straw) were investigated at 20% fibre load as active flame-retardant fillers in combination with two types of bio-based synthesized thermoplastics poly-lactic acid (PLA) and Lignin. Flammability behavior and morphological examinations of the resulted building materials were tested. Through post-fabrication techniques including vacuum thermoforming processes, a variety of cladding panels with different architectural designs were achieved. The applied fibres were not chemically treated. Instead, the fibres were mechanically densified, maintaining the inner natural minerals contents. The results have shown promising possibility of applying straw fibres as partial replacement of classic flame-retardants especially in combination with bioplastics. The straw based green biocomposites were proved to offer high ecological, economical and aesthetic input in the building industry.
Körner, A., Born, L., Mader, A., Sachse, R., Saffarian, S., Westermeier, A. S., Poppinga, S., Bischoff, M., Gresser, G. T., Milwich, M., Speck, T., & Knippers, J. (2017). Flectofold - A biomimetic compliant shading device for complex free form facades. Smart Materials and Structures
(017001), Article 017001. https://doi.org/10.1088/1361-665X/aa9c2f
AbstractSmart and adaptive outer façade shading systems are of high interest in modern architecture. For long lasting and reliable systems, the abandonment of hinges which often fail due to mechanical wear during repetitive use is of particular importance. Drawing inspiration from the hinge-less motion of the underwater snap-trap of the carnivorous waterwheel plant (Aldrovanda vesiculosa), the compliant façade shading device Flectofold was developed. Based on computational simulations of the biological role-model's elastic and reversible motion, the actuation principle of the plant can be identified. The enclosed geometric motion principle is abstracted into a simplified curved-line folding geometry with distinct flexible hinge-zones. The kinematic behaviour is translated into a quantitative kinetic model, using finite element simulation which allows the detailed analyses of the influence of geometric parameters such as curved-fold line radius and various pneumatically driven actuation principles on the motion behaviour, stress concentrations within the hinge-zones, and actuation forces. The information regarding geometric relations and material gradients gained from those computational models are then used to develop novel material combinations for glass fibre reinforced plastics which enabled the fabrication of physical prototypes of the compliant façade shading device Flectofold.
Früh, N., Amorth, S., & Wieland, T. (2017). Building Information Modelling (BIM) in der Qualitätskontrolle: Laser-Scanning der Brettschichtholz-Schalenbauteile für die Herstellung des Schalentragwerks des neuen Stuttgarter Hauptbahnhof (S 21). Bauingenieur, Jahresausgabe 2017/18, 96 – 101.
La Magna, R., Waimer, F., & Knippers, J. (2016). Coreless Winding and Assembled Core – Novel fabrication approaches for FRP based components in building construction. Building and Costruction Materials, 1.
Gil Pérez, M., Kang, T. H.-K., Sin, I., & Kim, S. D. (2016). Nonlinear Analysis and Design of Membrane Fabric Structures: Modeling Procedure and Case Studies. Journal of Structural Engineering
(11), Article 11. https://doi.org/10.1061/(ASCE)ST.1943-541X.0001557
AbstractMembrane fabric structures are spatial structures that allow for long span and lightweight roofs. In many cases, membrane roofs are supported with trusses or masts and prestressed together with cables to obtain a resistant shape for a given loading condition. For the design of membrane structures, geometrically nonlinear analysis is required. Additionally, modeling of each membrane element and formfinding of the shape are of great importance in the design process. First, an equilibrium-finding analysis is conducted for the purpose of obtaining the optimal shape of the membrane structure, during which the initial stresses of the membrane and cables must be balanced. Next, the stress-deformation analysis is performed for the required loading condition. This analysis allows understanding of the behavior of the structure and confirms that the design of the membrane satisfies the required safety factor for the construction. The analyses of the Southwestern Baseball Dome in Seoul and the Jeju Stadium Dome in Jeju Island, both in Korea, are presented, with an emphasis on details in all aspects of the analysis process. It is found that the selection of analysis and design techniques and appropriate construction materials would be most critical. The analysis results also show that the form-finding step has a significant effect on increasing the stiffness of the structure and a more regular geometry promotes a more stable response under various loading conditions.
Knippers, J., & Menges, A. (2015). Fasern neu gedacht – auf dem Weg zu einer Konstruktionssprache. Detail, 1238 – 1242.
Hasselhoff, J., Cheng, L., Waimer, F., Gabler, M., & Knippers, J. (2015). Design, manufacturing and testing of shear-cone connectors between CFRP stay-in-place formwork and concrete. COMPOSITE STRUCTURES
, 47–54. https://doi.org/10.1016/j.compstruct.2015.04.001
AbstractStay-in-place formwork is often used to accelerate the construction of structural elements such as flooring, concrete bridge decks and compressed shells. This study aims at designing, manufacturing and testing of two different nonlinear shear connectors made of fiber reinforced polymer composites for the formwork: (1) non-directional, cylindrical shear-cones; and (2) directional, cubical shear-cones with one side beveled. Six 1m-long specimens were constructed using carbon fiber reinforced polymer stay-in-place formwork and a plain concrete slab (200 wide and 130mm thick). Based on the results of three-point bending tests, similar stiffness, load–displacement response and failure mode were observed in the two contrasting designs. The resistance of the specimens using cylindrical shear-cones was approximately 26% higher than that of the ones with cubical design.
Dörstelmann, M., Knippers, J., Menges, A., Parascho, S., Prado, M., & Schwinn, T. (2015). ICD/ITKE Research Pavilion 2013: Modular Coreless Filament Winding Based on Beetle Elytra. AD Architectural Design, 237, Article 237.
Knippers, J., La Magna, R., Menges, A., Reichert, S., Schwinn, T., & Waimer, F. (2015). ICD/ITKE Research Pavilion 2012: Coreless Filament Winding Based on Morphological Principles of Arthropd Exosceleton. AD Architectural Design
, Article 237. https://doi.org/10.1002/ad.1953
Speck, T., Knippers, J., & Speck, O. (2015). Self-X Materials and Structures in Nature and Technology. AD Architectural Design, 237, Article 237.
AbstractOver the course of 3.8 billion years of biological evolution, nature has found the answers to many engineering problems. The aim of biomimetics is to analyse and tap biology's potential as a huge reservoir for innovative solutions. Thomas Speck, Professor and Director of the Plant Biomechanics Group (PBG) at the University of Freiburg and the Freiburg Centre for Interactive Materials and Bioinspired Technologies (FIT), Jan Knippers , Professor and Head of the Institute of Building Structures and Structural Design (ITKE) at the University of Stuttgart, and Olga Speck, a researcher at the PBG, scientific coordinator of FIT and manager of the Competence Network Biomimetics at Freiburg, explain how biological material systems with self‐x properties are cost‐efficient, multifunctional, and can be environmentally friendly; and with several billion trial runs, have surely stood the test of time.
Dörstelmann, M., Knippers, J., Koslowski, V., Menges, A., Prado, M., Schieber, G., & Vasey, L. (2015). ICD/ITKE Research Pavilion 2014: Fibre Placement on a Pneumatic Body Based on a Water Spider Web. AD Architectural Design, 237, Article 237.
AbstractProcess‐based biomimetics focuses on the transfer of biological principles to architectural construction. To realise the ICD/ITKE Research Pavilion 2014 ‐15, presented here by Moritz Doerstelmann, Jan Knippers, Valentin Koslowski, Achim Menges, Marshall Prado, Gundula Schieber and Lauren Vasey of the Institute for Computational Design (ICD) and Institute of Building Structures and Structural Design (ITKE) research team at the University of Stuttgart, sensor‐driven robotic fabrication was combined with advanced design computation and simulation. This enabled the construction of an architectural fibre structure on a pneumatic mould, drawing on the complex design of the web of a water spider.
Lienhard, J., & Knippers, J. (2015). Biegeaktive Tragwerke. Bautechnik (92) 06/2015, S.., Jahrgang 92, 394 – 402.
AbstractBiegeaktive Tragwerke sind gekrümmte Tragwerke, deren Geometrie und Systemsteifigkeit sich aus einer elastischen Verformung von Tragelementen ergibt. Biegung kann demnach dazu genutzt werden, komplexe räumlich gekrümmte Tragsysteme aus ursprünglich geradlinigen oder ebenen Tragelementen zu erzeugen. Bei der Arbeit mit biegeaktiven Tragstrukturen zeigt sich, dass dieser Formgebungsansatz die Entwicklung hocheffizienter Tragsysteme ermöglicht, welche - frei von tradierten typologischen Ansätzen der Tragwerkslehre - aus dem Kurzschließen von Rückstellkräften entstehen. Nach einer Definition der Begriffe und kurzen Darstellung der relevanten mechanischen sowie werkstofftechnischen Grundlagen werden in diesem Aufsatz die besonderen Eigenschaften dieser Tragwerke anhand von Fallbeispielen erläutert.
Li, J.-M., & Knippers, J. (2015). Segmental Timber Plate Shell for the Landesgartenschau Exhibition Hall in Schwäbisch Gmünd the Application of Finger Joints in Plate Structures. International Journal of Space Structures
, Vol. 30
(No. 2), Article No. 2. https://doi.org/10.1260/0266-35126.96.36.199
AbstractSegmental plate shells are an interesting option for the design and construction of cost-effective shell structures. They are composed of prefabricated segmental plates that are joined together to become an integral structure that generates a shell action and transfers external loads into membrane forces. However, connections between segmental plates nearly always weaken shell structures as they disturb the material continuity and thus their stiffness.
The application of finger joint connections can effectively increase the in-plane stiffness and thus makes plate shell structures stiffer and stronger. Moreover, they attract more forces to flow through the connection in the form of in-plane shears instead of axial forces and thus reduce the load in the axial direction of a connection. As a result, the application of finger joints allows a lighter axial joint design with smaller screw diameters, which is preferred in a thin timber plate structure.
The paper presents the Landesgartenschau Exhibition Hall as a successful demonstrator for segmental timber plate shells and highlights the design of the finger joint connections.
Schleicher, S., Lienhard, J., Poppinga, S., Speck, T., & Knippers, J. (2015). A methodology for transferring principles of plant movements to elastic systems in architecture. COMPUTER-AIDED DESIGN
(Issue C), Article Issue C. https://doi.org/10.1016/j.cad.2014.01.005
AbstractIn architecture, kinetic structures enable buildings to react specifically to internal and external stimuli through spatial adjustments. These mechanical devices come in all shapes and sizes and are traditionally conceptualized as uniform and compatible modules. Typically, these systems gain their adjustability by connecting rigid elements with highly strained hinges. Though this construction principle may be generally beneficial, for architectural applications that increasingly demand custom-made solutions, it has some major drawbacks. Adaptation to irregular geometries, for example, can only be achieved with additional mechanical complexity, which makes these devices often very expensive, prone to failure, and maintenance-intensive.Searching for a promising alternative to the still persisting paradigm of rigid-body mechanics, the authors found inspiration in flexible and elastic plant movements. In this paper, they will showcase how today's computational modeling and simulation techniques can help to reveal motion principles in plants and to integrate the underlying mechanisms in flexible kinetic structures. By using three case studies, the authors will present key motion principles and discuss their scaling, distortion, and optimization. Finally, the acquired knowledge on bio-inspired kinetic structures will be applied to a representative application in architecture, in this case as flexible shading devices for double curved facades. Plant movements.Kinetic structures.Biomimetics.Facade shading.Compliant mechanisms.
Lienhard, J., & Knippers, J. (2015). Bending-active textile hybrids. Journal of the International Association for Shell and Spatial Structures, 56(1), Article 1.
AbstractThis paper discusses form-finding and simulation strategies for form- and bending-active hybrid structures. The interaction of tension in the surface and bending in beam elements leads to a complex form-finding question in which the boundary conditions for the membrane are nonlinear; they deform as a result of the membrane pre-
stress. After a general introduction of form- and bending-active hybrid structures the form-finding question is discussed by introducing a numerical approach in FEM as well as through the discussion of realised projects.
Knippers, J. (2014). Faserverbundstrukturen für die Architektur: Potential, Einsatzmöglichkeiten und realisierte Projekte. Umrisse, 6, Article 6.
Knippers, J., & Helbig, T. (2014). Das Prinzip Leichtbau und seine Bedeutung für das konstruktive Entwerfen. Stahlbau, (83), 777 – 783.
AbstractJörg Schlaich setzt sich für eine ganzheitliche Qualität im Ingenieurbau ein. Das Prinzip Leichtbau ist dabei die zentrale Richtschnur seines Entwerfens. Leichtbau ist für ihn nicht Selbstzweck, sondern hat eine soziale, ökologische und kulturelle Bedeutung. Sozial, weil eine feingliedrige Konstruktion eine hohe Wertschöpfung für Planung und Herstellung generiert, ökologisch, weil ein geringer Materialeinsatz Ressourcen spart und kulturell, weil eine dem Kraftfluss folgende Form zeitlosen Gestaltungsprinzipien folgt. Zu seinem Selbstverständnis als kulturell verantwortlicher Ingenieur gehört auch die Verankerung in der Bau‐ und Konstruktionsgeschichte. Viele seiner Entwürfe knüpfen an Ansätze großer Wegbereiter des Ingenieurbaus an, interpretieren diese aber völlig neu und überführen sie in Konstruktionen höchster Eleganz.
Wie werden nun heute die Ansätze von Jörg Schlaich zum Leichtbau aufgegriffen, wie werden sie weiterentwickelt und welche Diskussionen stoßen sie an? Stellvertretend für die vielen Kolleginnen und Kollegen, die ihre prägenden beruflichen Impulse Jörg Schlaich und seinem Umfeld verdanken, möchten wir dies an eigenen Projekten diskutieren.
AbstractThe paper presents experimental work to determine the load-bearing capacity, strain responses up to failure, and failure mode of pultruded carbon fiber–reinforced polymer (CFRP) strips with different deviation saddle geometries. Several tests with different deviation angles and deviation saddle radii were carried out. The results show that the tensile strength of the CFRP strip is reduced significantly by deviation, even if the deviation radius is comparatively large in relation to the thickness of the CFRP strips. Further tests were carried out to determine the influence of other important parameters on the load-bearing capacity of the strip such as surface properties of the saddle. With the help of a polyethylene layer (PE-HD) between the CFRP strip and the deviation saddle, friction could be reduced. This leads to an increase in the breaking strength of the CFRP strip. The effect of these parameters on the load-bearing capacity of the CFRP strip is presented in this article.
Reichert, S., Schwinn, T., La Magna, R., Waimer, F., Knippers, J., & Menges, A. (2014). Fibrous structures: an integrative approach to design computation, simulation and fabrication for lightweight, glass and carbon fibre composite structures in architecture based on biomimetic design principles. Computer-Aided Design
, 27–39. https://doi.org/10.1016/j.cad.2014.02.005
AbstractIn this paper the authors present research into an integrative computational design methodology for the design and robotic implementation of fibre-composite systems. The proposed approach is based on the concurrent and reciprocal integration of biological analysis, material design, structural analysis, and the constraints of robotic filament winding within a coherent computational design process. A particular focus is set on the development of specific tools and solvers for the generation, simulation and optimization of the fibre layout and their feedback into the global morphology of the system. The methodology demonstrates how fibre reinforced composites can be arranged and processed in order to meet the specific requirements of architectural design and building construction. This was further tested through the design and fabrication of a full-scale architectural prototype.
Knippers, J. (2014). Integriertes Entwerfen im digitalen Prozess. Bautechnik, 257 – 261.
Köhler-Hammer, C., & Knippers, J. (2014). Arbo Skin Fassaden-Mock up: Fassaden aus dauerhaften und rezyklierfähigen Biokunststoffen. Fassade / Facade, Schweizerische Fachzeitschrift für Fenster- und Fassadenbau, 1, Article 1.
Knippers, J., Köhler-Hammer, C., Hammer, M. R., & Fildhuth, T. (2014). Fassadenbekleidung aus nachwachsenden Rohstoffen – Thermoplastischer Werkstoff. Deutsches Ingenieurblatt, 4, Article 4.
AbstractWährend eines Forschungsprojektes wurde ein neuer thermoplastischer Werkstoff für Fassadenbekleidungen entwickelt, der zu über 90 % aus nachwachsenden Rohstoffen besteht. Die recyclebare Biokunststoffplatte kann als Fassaden- und Innenwandbekleidung ebener oder frei geformter Innen- und Außenwände eingesetzt werden. Sie erfüllt die üblichen Anforderungen, die hinsichtlich Dauerhaftigkeit und Flammschutz an Baustoffe gestellt werden.
Ziel des am Stuttgarter Institut für Tragkonstruktionen und Konstruktives Entwerfen (ITKE) durchgeführten Forschungsprojektes war, ein möglichst nachhaltiges und dennoch langlebiges Baumaterial zu entwickeln. Der Anteil erdölbasierter Komponenten und Additive sollte dabei gering gehalten werden. Das Institut für Siedlungswasserbau, Wassergüte- und Abfallwirtschaft (ISWA) übernahm die ökobilanzielle Bewertung, ermittelt wurde auch die Beständigkeit des Materials gegenüber mikrobiellem Abbau.
Dahy, H. (2014). Green Biocomposites for architectural applications. Bioplastics MAGAZINE, Issue 3, Article Issue 3.
Dahy, H. (2014). Natural fibres as flame-retardants? Bioplastics Magazine, 02, Article 02.
Waimer, F., La Magna, R., Reichert, S., Schwinn, T., Menges, A., & Knippers, J. (2013). Bionisch-inspirierte Faserverbundstrukturen. Bautechnik, 766 – 771.
Hub, A., Zimmermann, G., & Knippers, J. (2013). Leichtbeton mit Aerogelen als Konstruktionswerkstoff. Beton- und Stahlbetonbau, 654 – 661.
AbstractAerogelhaltiger Leichtbeton weist als gefügedichtes Material eine signifikant verbesserte Wärmedämmung gegenüber luftgedämmten Leichtbetonmaterialien auf. Durch eine gezielte Beeinflussung der Betonkomponenten zu einer höheren Packungsdichte lassen sich auch die Festigkeitseigenschaften positiv beeinflussen, sodass das Material sowohl eine hervorragende Dämmwirkung als auch eine ausreichende Tragfähigkeit aufweist. Der Aufsatz beschreibt die Materialentwicklung und experimentell ermittelte Materialparameter.
Knippers, J., Scheible, F., Oppe, M., & Jungjohann, H. (2013). Bio-inspirierte kinetische Fassade für den Themenpavillon One Ocean Expo 2012 in Yeosu, Korea. Bautechnik, 341 ff.
AbstractDer von SOMA Architecture aus Wien, Österreich entworfene Themenpavillon “One Ocean” ist eines der wichtigsten Gebäude der Expo 2012 in Yeosu, Korea. Die dem Expo‐Gelände und dem Haupteingang zugewandte Seite ist von einer kiemenartigen, mit LED bestückten beweglichen Medienfassade geprägt. Sie stellt einen gestalterischen Bezug zum Meer her und ermöglicht die Lichtsteuerung des Gebäudes.
Grundlage der Entwicklung der kinetischen Fassade war die Analyse natürlicher Bewegungsprinzipien. Die Verwendung von glasfaserverstärkten Kunststoffen (GfK) erlaubt große reversible elastische Verformungen und ermöglicht somit eine komplett neue Interpretation wandelbarer Strukturen.
La Magna, R., Reichert, S., Schwinn, T., Waimer, F., Knippers, J., & Menges, A. (2013). Carbon und Glasfaser- vom Roboter gewickelt. Deutsches Ingenieurblatt, 12–15.
La Magna, R., Gabler, M., Waimer, F., Menges, A., Reichert, S., Schwinn, T., & Knippers, J. (2013). From Nature to Fabrication: Biomimetic Design Principles for the Production of Complex Spatial Structures. International Journal of Space Structures, Vol. 28(No. 1), Article No. 1.
AbstractIn the current paper the authors present a biomimetic design methodology based on the analysis of the Echinoids (sea urchin and sand dollar) and the transfer of its structural morphology into a built full-scale prototype.
In the first part, an efficient wood jointing technique for planar sheets of wood through novel robotically fabricated finger-joints is introduced together with an investigation of the biological principles of plate structures and their mechanical features. Subsequently, the identified structural principles are translated and verified with the aid of a Finite Element Model, as well as a generative design system incorporating the rules and constraints of fabrication. The paper concludes with the presentation of a full-scale biomimetic prototype which integrates these morphological and mechanical principles to achieve an efficient and high-performing lightweight structure.
Knippers, J. (2013). From Model Thinking to Process Design. AD Architectural Design, 74–81.
AbstractThe introduction of computational design processes and particularly of computer‐aided fabrication methods recast roles across the design team. As Jan Knippers , founding partner of Knippers Helbig Advanced Engineering and Head of the Institute of Building Structures and Structural Design (ITKE) at the University of Stuttgart explains, it offers structural engineers a unique opportunity: the potential to break through the barriers of conventional model thinking (thinking in discrete typologies) and to embrace process design and new forms of interaction.
Lienhard, J., & Knippers, J. (2013). Considerations on the Scaling of Bending-Active Structures. International Journal of Space Structures, Vol. 28(Number 3 & 4), Article Number 3 & 4.
AbstractBending-active structures are composed of curved beam or shell elements which base their geometry on the elastic deformation of an initially straight or planar configuration. In bending-active structures the moment of inertia has a direct influence on the residual stress and is therefore limited by a given minimal curvature in the system and the permissible bending stress capacities of the chosen material. These interdependencies may lead to a scaling issue that limit bending-active structures to a certain size range. This range may be widened if the system's reliance on elastic stiffness is compensated by other stiffening factors such as coupling of structural elements and stress stiffening effects.
This paper will analyse the scaling effects in bending-active structures. Some basic systems are studied by means of dimensional analysis and FEM parameter studies to clarify at which power each influencing factor effects scaling. Based on these findings some more complex structures are studied for their scalability. This will offer the basis for some more general conclusions.
Knippers, J., & Menges, A. (2013). LEICHT Forschungspavillon in Stuttgart. Baukultur – Zeitschrift des DAI, 4, Article 4.
Waimer, F., La Magna, R., & Knippers, J. (2013). Integrative Numerical Techniques for Fibre Reinforced Polymers – Forming Process and Analysis of Differentiated Anisotropy. Journal of the International Association for Shell and Spatial Structures, Vol. 54(No. 178), Article No. 178.
AbstractIn the current paper, the authors developed two different numerical methods for fibre reinforced polymers. The first method deals with the simulation of an innovative manufacturing process based on filament winding for glass and carbon fibre reinforced polymers. The second developed numerical method aims at modelling a high level of material complexity and allowing reciprocal confrontation with a geometric differentiated global structure. The developed numerical techniques served as a basis for the design and implementation of a Pavilion built on the campus of the University of Stuttgart in 2012 and could thus be tested and proved.
Dahy, H. (2013). Influence of the 3Rs on Modern Approaches in Sustainable Architecture. The International Journal of Environmental Sustainability, Vol. 8(Issue 4), Article Issue 4.
Köhler-Hammer, C. (2013). Biobased plastics for exterior facades. Bioplastics Magazine, 4, Article 4.
Lienhard, J., Alpermann, H., Gengnagel, C., & Knippers, J. (2013). Active Bending, A Review on Structures where Bending is used as a Self-Formation Process 1. International Journals of Space Structures, Vol. 28, Number 3 & 4, 2013, Vol. 28(Number 3 & 4,), Article Number 3 & 4,.
AbstractIn this paper structures that actively use bending as a self-forming process are reviewed. By bringing together important material developments and various historical as well as recently built samples of such structures, the aim is to show coherences in their design approach, structural systems and behaviour. Different approaches to bending-active structures are defined and described. By making this work accessible and categorising it, this paper aims to contribute to an emerging development.
Adifferentiation of such structures is suggested based on their design approaches. Three such approaches are differentiated: the behaviour based approach, the geometry based approach and current research that seeks to integrate the two. In this paper the nature of these approaches and some important project samples are discussed.
Knippers, J. (2012). Von der Konstruktion des Bauwerks zur Gestaltung der Prozesse. Detail, 1142 – 1148.
Knippers, J., Scheible, F., Jungjohann, H., & Oppe, M. (2012). Themenpavillon EXPO 2012 in Yeosu, Korea: Bio-inspirierte Kinetische Fassade. Innovative Fassadentechnik, 106–109.
Poppinga, S., Lienhard, J., Schleicher, S., Speck, O., Knippers, J., Speck, T., & Masselter, T. (2012). Paradiesvogelblume trifft Architektur. Praxis der Naturwissenschaften: Biologie in der Schule 05/61, 31 – 35.
Knippers, J. (2012). From the Construction of a Building to the Design of the Process Involved. Detail – English Edition, 634 – 638.
Knippers, J., Menges, A., Gabler, M., La Magna, R., Reichert, S., Schwinn, T., & Waimer, F. (2012). von den Seeigeln lernen. Bauen mit Holz, 24 – 27.
Köhler-Hammer, C. (2012). Ressourceneffiziente Werkstoffe. DETAIL Research – Forschung und Entwicklung.
Knippers, J., & Speck, T. (2012). Design and construction principles in nature and architecture. Bioinspiration & Biomimetics, Vol. 7(1), Article 1.
AbstractThis paper will focus on how the emerging scientific discipline of biomimetics can bring new insights into the field of architecture. An analysis of both architectural and biological methodologies will show important aspects connecting these two. The foundation of this paper is a case study of convertible structures based on elastic plant movements.
Knippers, J. (2012). Von Seeigeln und Strelitzien. Deutshe Bauzeitung (db), 64 – 67.
Köhler-Hammer, C. (2012). Bioacoustic room divider – Flame retardant PLA for interior use. Bioplastics MAGAZINE, Vol. 7, 38 – 40.
Knippers, J. (2012). Neue Denkmuster. XIA Intelligente Architektur, 80(07–09), Article 07–09.
Fleischmann, M., Knippers, J., Lienhard, J., Menges, A., & Schleicher, S. (2012). Material Behaviour: Embedding Physical Properties in Computational Design Processes. Architectural Design, Vol. 82(No. 2), Article No. 2.
AbstractMaterial behaviour computes form. In the physical world, material form is always inseparably connected to internal constraints and external forces; in the virtual space of digital design, though, form and force are usually treated as separate entities – divided into processes of geometric form generation and subsequent engineering simulation. Using the example of the interdisciplinary ICD/ITKE Research Pavilion, constructed at the University of Stuttgart in 2010, Moritz Fleischmann, Jan Knippers, Julian Lienhard, Achim Menges and Simon Schleicher explain how feedback between computational design, advanced simulation and robotic fabrication expands the design space towards previously unexplored architectural possibilities.
Mader, A., Volkmann, E., Einsiedel, R., & Müssig, J. (2012). Impact and Flexuaral Properties of Undirected Man Made Reinforced Thermoset Composites. Journal of Biobased Materials and Bioenergy, 6, Article 6.
Menges, A., & Knippers, J. (2012). Skeleton Morphology of Sand Dollar – ICD/ITKE Research Pavilion. Beyond. Architecture Art Culture, No. 13, Article No. 13.
Ludwig, F., Schwertfeger, H., & Storz, O. (2012). Living Systems – Designing Growth in Baubotanik. Architectural Design, Vol. 82(No. 2), Article No. 2.
Knippers, J., & Menges, A. (2011). ICD/ITKE Research Pavilion 2010. Architecture + Urbanism A+U: Timber Innovation, No.490, Article No.490.
Lienhard, J., Fleischmann, M., D´Souza, D., & Schleicher, S. (2011). Digitales Entwerfen: Biegung erwünscht. Bauen mit Holz, 30 – 34.
Knippers, J., & Menges, A. (2011). Research Pavilion ICD/ITKE. C3 Architecture-Landscape-Urbanism, Vol. 27(No. 317), Article No. 317.
Schieber, G. (2011). highrice – ein architektonischer Ansatz, die Ernährung der Weltbevölkerung sicherzustellen. xia Intelligente Architektur, 10–12, Article 10–12.
Gabler, M., Knippers, J., La Magna, R., Menges, A., Reichert, S., Schwinn, T., & Waimer, F. (2011). Leichtbau – Prinzip Seeigel. Bauwelt
, Vol. 102
(No. 31/2011), Article No. 31/2011. https://www.bauwelt.de/dl/791180/bw_2011_31_0020-0021.pdf
Lienhard, J., Schleicher, S., Poppinga, S., Masselter, T., Milwich, M., Speck, T., & Knippers, J. (2011). Flectofin: a hingeless flapping mechanism inspired by nature. Bioinspiration & Biomimetics, Vol. 6.
AbstractThis paper presents a novel biomimetic approach to the kinematics of deployable systems for architectural purposes. Elastic deformation of the entire structure replaces the need for local hinges. This change becomes possible by using fibre-reinforced polymers (FRP) such as glass fibre reinforced polymer (GFRP) that can combine high tensile strength with low bending stiffness, thus offering a large range of calibrated elastic deformations. The employment of elasticity within a structure facilitates not only the generation of complex geometries, but also takes the design space a step further by creating elastic kinetic structures, here referred to as pliable structures. In this paper, the authors give an insight into the abstraction strategies used to derive elastic kinetics from plants, which show a clear interrelation of form, actuation and kinematics. Thereby, the focus will be on form-finding and simulation methods which have been adopted to generate a biomimetic principle which is patented under the name Flectofin®. This bio inspired hingeless flapping device is inspired by the valvular pollination mechanism that was derived and abstracted from the kinematics found in the Bird-Of-Paradise flower (Strelitzia reginae, Strelitziaceae).
Fildhuth, T., & Knippers, J. (2011). Geometrie und Tragverhalten von doppelt gekrümmten Ganzglasschalen aus kalt verformten Glaslaminaten. Stahlbau Spezial (2011) – Glasbau/Glass in Building, 31 ff.
AbstractDie Herstellung doppelt gekrümmter Glaselemente mittels Kaltverformens, wie sie auf der glasstec 2010 vorgestellt wurden, ist vielversprechend für die Verwendung für Ganzglas‐Schalenkonstruktionen, deren optische und technische Qualität auf die Ansprüche der Architektur nach hochtransparenten, sanft gekrümmten Formen reagiert.
Die Ergebnisse der Untersuchung von Formgebungs‐ und Materialeigenschaften der kaltgekrümmten Scheiben ermöglichten die Erarbeitung und Vorauswahl entsprechender doppelt gekrümmter Schalengeometrien. Charakteristische Grundformen sind dann Parameterstudien und Sensibilitätsanalysen zur Ermittlung des Tragverhaltens abhängig von Fügung, Lagerung und Einteilung unterzogen worden. Antiklastische Geometrien haben sich dabei als besonders interessant herausgestellt.
Schieber, G. (2010). Leichte Ingenieurkonstruktionen. Deutsche Bauzeitschrift DBZ, 62 – 63.
Knippers, J., & Helbig, T. (2010). Megastructure-Überdachung des Expo Boulevards EXPO Shanghai. Detail, 32 – 37.
Mangun, C., Mader, A., Sottos, N., & White, S. (2010). Self-healing of a high temperature cured epoxy using poly(dimethylsiloxane) chemistry. Polymer - Jounal of Polymer Research, 51, Article 51.
AbstractA high temperature cured self-healing epoxy is demonstrated by incorporating microcapsules of poly(dimethylsiloxane) (PDMS) resin and separate microcapsules containing an organotin catalyst. Healing is triggered by crack propagation through the embedded microcapsules in the epoxy matrix, which releases the healing agents into the crack plane initiating crosslinking reactions. A series of tapered double-cantilever beam (TDCB) fracture tests were conducted to measure virgin and healed fracture toughness. Healing efficiencies, based on fracture toughness recovery, ranged from 11 to 51% depending on the molecular weight of PDMS resin, quantity of healing agent delivered, and use of adhesion promoters.
Knippers, J., Pelke, E., Gabler, M., & Berger, D. (2010). Bridges with Glass Fibre Reinforced Polymers Decks – The new Road Bridge in Friedberg, Germany. Strucutral Engineering International, SEI 20(4), Article 4.
Knippers, J., Pelke, E., Gabler, M., & Berger, D. (2009). Brücken mit Fahrbahnen aus glasfaser-verstärktem Kunststoff (GFK) – Neue Straßenbrücke in Friedberg (Hessen). Stahlbau, 462 – 470.
AbstractIn Friedberg (Hessen) wurde im Juli 2008 erstmals in Deutschland eine Straßenbrücke unter Verwendung von glasfaserverstärktem Kunststoff (GFK) fertig gestellt. Das Bauwerk überspannt mit 27 m die Bundesstraße B 3a bei der Stadt Friedberg (Hessen) und wurde in Stahl‐GFK‐Verbundbauweise realisiert. Die hohe Dauerhaftigkeit des neuen Werkstoffs und die zügige Montage der Brücke waren die entscheidenden Gründe pro GFK. In den letzten Jahren wurden in den USA, Japan und auch in Europa einige Leichtbaubrücken mit faserverstärkten Kunststoffen realisiert. Dabei konnten wertvolle Erfahrungen zum Bau und Betrieb gesammelt und die Leistungsfähigkeit von Verbundwerkstoffen unter Beweis gestellt werden.
Die Brücke in Friedberg geht über diese Vorbilder hinaus, indem hier erstmals die Verbundwirkung zwischen der GFK‐Fahrbahn und dem Haupttragwerk aus Stahl berücksichtigt wird. Außerdem wurde konsequent der Ansatz eines wartungsarmen und langlebigen Bauwerks verfolgt, indem auf Lager und Fahrbahnübergänge verzichtet wurde.
Knippers, J. (2009). Interview: Vorfertigung hat Vorteile. greenbuilding - Nachhaltig planen, bauen und betreiben, 29 – 31.
Ludwig, F., & Storz, O. (2009). Verwachsende Konstruktionen. Tec 21, Jg. 135(29/30), Article 29/30.
Knippers, J., & Helbig, T. (2009). Recent Developments in the Design of Glazed Grid Shells. International Journal of Space Structures, 24(2), Article 2.
Knippers, J., & Hwash, M. (2008). Umgelenkte Lamellen aus kohlefaserverstärktem Kunststoff für freistehende Spannglieder im Konstruktiven Ingenieurbau. Beton- und Stahlbetonbau
, S. 682 – 688. https://doi.org/10.1002/best.200800637
AbstractKohlenstofffaserverstärkter Kunststoff (CFK) besitzt eine Reihe von ausgezeichneten Eigenschaften mit weitreichenden Anwendungsmöglichkeiten im konstruktiven Ingenieurbau. So werden schon seit einigen Jahren CFK‐Lamellen für die Instandsetzung und nachträgliche Verstärkung von Bauteilen aus Stahlbeton eingesetzt. Solche Lamellen könnten auch als freie Spannglieder, z. B. für extern vorgespannte Stahlbetonbrücken oder für unterspannte Decken im Hochbau, Verwendung finden. Die Empfindlichkeit von Kohlestofffaserverstärktem Kunststoff für Beanspruchungen durch Querpressungen macht jedoch die konstruktive Gestaltung der Endverankerung und der Umlenkung auf einem Sattel schwierig. Für die Endverankerung liegen bereits Ansätze von verschiedenen Forschungseinrichtungen vor. In diesem Aufsatz werden die Ergebnisse von Versuchen zur Ermittlung des Einflusses einer Umlenkung auf die Bruchlast von CFK‐Lamellen veröffentlicht.
Knippers, J. (2008). Neue Bauprodukte aus Reststoffen in Indien. Detail, 582 – 588.
Knippers, J., & Helbig, T. (2008). Vom Entwurf bis zur Ausführung frei geformter Netzschalen – eine Prozesskette. Stahlbau Spezial Konstruktiver Glasbau, 10–15.
AbstractFrei geformte Gitterschalen aus Stahl sind in der zeitgenössischen Architektur weit verbreitet. Computergesteuerte Planungs‐ und Fertigungswerkzeuge ermöglichen Konstruktionen, die vor wenigen Jahren noch undenkbar gewesen wären. Aber wie wird eine frei geformte 3D‐Geometrie in eine gebaute Struktur überführt, ohne dass dabei die architektonische Vision einer elegant geformten Gebäudehülle verlorengeht? Dazu ist von der Formgenerierung bis zur Montage auf der Baustelle eine durchgängige Prozesskette erforderlich, in der der Tragwerksplaner als Schnittstelle zwischen den ästhetischen Ambitionen des Architekten, den technischen Zwängen der Fertigung und den finanziellen Möglichkeiten des Bauherren eine zentrale Rolle einnimmt. In diesem Aufsatz wird am Beispiel von zwei verglasten Gitterschalen gezeigt, wie frei geformte 3D‐Geometrien neue Abläufe bei der Planung erfordern und sich neue Betätigungsfelder für Tragwerksplaner eröffnen.
Knippers, J. (2008). Des Einen Müll ist des Anderen Traum. Der Architekt, 6, Article 6.
Hwang, K.-J., Park, D.-U., Park, S.-W., & Knippers, J. (2007). Fiber Reinforced Polymer Considering of Short and Long-Term Behavior. Journal of the Korean Association for Spatial Structures, 7(3), Article 3.
Hwang, K.-J., Park, D.-U., Park, S.-W., & Knippers, J. (2007). Investigation and Numerical Analysis of Node Connectors in Free-Form Spatial Structures. Journal of the Korean Association for Spatial Structures, 7(3), Article 3.
AbstractThe recent completions of free-form spatial structures provide us a very attractive form. To realize such an extraordinary shape, it is absolutely necessary that the connector systems have to be investigated the characteristics of the systems and analyzed with a practicable method. In this context, this research consists of not only literature research but also numerical analysis with selected connector systems, which was adopted in real free-form spatial structures. For numerical analysis, especially, finite element analysis (FEA) is performed with a various test parameter using a commercial program ANSYS. Consequently, the general characteristics of node connectors the moment-rotation-curves are presented by considering a large deformation effect as well as a multi-linear material properties.
Park, D.-U., Knippers, J., & Hwang, K.-J. (2007). Development of New Detachable Connection for Glass Fiber Reinforced Polymer Considering of Short and Long-Term Behavior. Journal of the Korean Association for Spatial Structures, 7(3), Article 3.
AbstractThe appearance of many Glass Fiber Reinforced Plastic (GFRP) constructions look like ordinary steel construction, because GFRP has been imitated by the same way with the traditional steel's cross section as well as connection system. In terms of detachable connection, there was not enough appropriate option of GFRP connection, such as a traditional bolt connection for steel and wood structures. Most of all, from material characteristic of GFRP related to the deficient ductility, the shearstress principle of GFRP s not proper for the material property, which causes ineffective and not economic application of material. With this research problem, the innovative and detachable onnection system, which is more considered with appropriate material characteristic for FRP, is developed. Not only short time but also long time research with various connection variations is carried out.
Peters, S., Fuchs, A., Knippers, J., & Behling, S. (2007). Ganzglastreppe mit transparenten SGP-Klebeverbindungen – Konstruktion und statische Berechnung. Stahlbau, 151 – 156.
AbstractAuf der glasstec 2006 in Düsseldorf, der weltweit größten Messe der glaserzeugenden und glasverarbeitenden Industrie, wurde von der Firma Seele eine Ganzglastreppe mit einer freien Spannweite von sieben Metern errichtet. Die beiden tragenden Wangen bestehen aus jeweils einer mehrlagigen Floatglasscheibe ohne Stoß. Neben der großen Spannweite der Glasscheiben ist vor allem die Verwendung einer neuartigen Klebetechnik mittels hochtransparenter SGP (SentryGlas® Plus)-Folien bemerkenswert. Im Mittelpunkt dieses Aufsatzes stehen das statische Konzept der Treppe sowie die Ausführung und Bemessung der Klebeverbindungen.
Dahy, H. (2007). User´s Participation in the Architectural Work – Special Study of Self building Issue. Scientific Bulletin of Faculty of Engineering, Ain Shams University.
Knippers, J., & Helbig, T. (2006). Fassadenabwicklung Kaufhaus Peek und Cloppenburg, Köln. Glas ., 1, Article 1.
Ludwig, F., & Storz, O. (2005). Baubotanik – Mit lebenden Pflanzen konstruieren. Baumeister.
Park, D.-U., Hub, A., Hwang, K.-J., & Knippers, J. (2005). The new developments of smart and lightweight structures with glass fiber reinforced polymer (GFRP) in architecture and structural engineering. POAR People & Architects, 113, 82–95.
Knippers, J., & Peters, S. (2005). glasstec Düsseldorf – Fenster und Fassaden aus GFK und Glas. GLAS Architektur und Technik, 14–16.
Knippers, J., Park, D.-U., Hub, A., & Hwang, K.-J. (2005). The mobile and modular GFRP-membrane-structure with the new innovative connection system. Journal of the Korean Association for Shell and Spatial Structures (KASSS), 5(2), Article 2.
AbstractCurrently, the structural material, namely glass fiber reinforced polymer (GFRP) is focused on innovative structure due to lightness, excellent workability and noncorrosive characteristics, etc. However, the lack of GFRP connection technology produces only an imitation of steel and wood structures. This uses univentive design principles as well as unsuitable material applications, causes tons of surplus of materials to be wasted, and results in uneconomical structures, because the characteristics between steel and GFRP are completely different. Thus, this research develops the new, innovative GFRP connection system with considerations of the characteristics of GFRP and adopts it to a mobile und modular membrane pavilion.
Knippers, J., Peters, S., & Zhang, H. (2005). Glasfaserverstärkter Kunststoff – Werkstoff für eine kommende Architektur der Gebäudehülle, Teil 2. Fassadentechnik, 6, Article 6.
Knippers, J., Peters, S., & Weller, C. P. (2005). Glasfaserverstärkter Kunststoff – Werkstoff für eine kommende Architektur der Gebäudehülle. Fassadentechnik, 3, Article 3.
Helbig, T., Knippers, J., & Müller, T. (2005). Ein Walfisch aus Stahl, Holz und Glas – die Fassade des Kaufhauses Peek und Cloppenburg in Köln. Stahlbau, 803 – 808.
AbstractMit dem neuen Kaufhaus Peek und Cloppenburg ist ein Bau von herausragender architektonischer Qualität mitten im Herzen der Kölner Altstadt entstanden. Seine Fassade, über die in diesem Aufsatz berichtet wird, war in vielfacher Hinsicht eine besondere Herausforderung für die Tragwerksplanung. Dies betrifft die komplexe Geometrie, die Lagerung auf dem Rohbau vor allem aber die ungewöhnliche und neuartige Kombination der Werkstoffe Stahl und Holz. Aufgelöste vertikale Holzbinder und horizontale Stahlrohre bilden mit diagonalen Stahlseilen eine freitragende Stabschale. Dazu mußten zahlreiche Konstruktionsdetails, insbesondere die Holzverbinder, erstmals gelöst werden.
Fildhuth, T. (2005). Entwicklung weitspannender, leichter Isolierglaselemente. Großflächige Isolierverglasungen als selbsttragende Bauteile. GLAS Architektur und Technik, Jg. 11(4), Article 4.
Knippers, J., & Park, D.-U. (2003). Stabile Plastiken, Fußgängerbrücken aus faserverstärktem Kunststoff. Deutsche Bauzeitung(db), 75–80.
Knippers, J., & Park, D.-U. (2003). Innovative Glastechnologien, GFK & Glas. Architektur & Bau Forum, 11.
Knippers, J., & Peters, S. (2003). Werkstoffverbund von Kunststoff und Glas. Architektur + Bau Forum, 10–11.
Knippers, J., & Peters, S. (2003). GFK-Glas-Pavillon auf der Glasstec 2002. Glas, Architektur und Technik, 1, Article 1.
Bulenda, T., & Knippers, J. (2001). Stability of grid shells. Computers and Structures, 79, 1161 – 1174.
AbstractGrid shells exhibit different modes of stability failure. This paper explains some parameters influencing the failure load of domes and barrel vaults and makes suggestions for the imperfection shape which has to be assumed in an analysis. All computations are carried out with a commercial FE-program.
Schürmann, P., & Knippers, J. (2000). Domshof – Pavillon in Bremen. Deutsche Bauzeitung (db), 50 – 64.
Bergermann, R., & Knippers, J. (2000). VW-Kundencenter Wolfsburg. Der Bauingenieur, 631 – 635.
Knippers, J. (2000). Johann Wilhelm Schwedler: Vom Experiment zur Berechnung. Deutsche Bauzeitung (db), 105 – 112.
Schlaich, J., & Knippers, J. (2000). Folding Mechanism of the Kiel Hörn Footbridge. Structural Engineering International - Official Journal of the International Association for Bridge and Structural Engineering
(1), Article 1. https://doi.org/10.2749/101686600780620991
AbstractA fjord of the Baltic Sea divides the centre of the City of Kiel. To provide a pedestrian crossing that allows passage of ships, a folding cable-stayed bridge was built. Its unusual folding mechanism was proposed not only to ensure a safe and robust operation, but also to provide a visual and technical attraction. The deck folds at three hinges by the continuous rotation of a pair of single-speed winches, to which all cable drums are connected.
Schlaich, J., & Knippers, J. (1999). Dreifeld-Klappbrücke Kiel-Hörn. Bauingenieur, 213 – 217.
Schlaich, J., Schober, H., & Knippers, Jan. (1999). Bahnsteigüberdachung Fernbahnhof Spandau. Stahlbau, 1022 – 1028.
Schlaich, J., Schober, H., & Knippers, J. (1999). Vom Bogen zur Tonne: der Weg zum Tragwerk des Fernbahnhofs Spandau. DETAIL - Zeitschrift Für Architektur + Baudetail, 675 – 678.
Knippers, J. (1998). Klappbrücke in Kiel. Deutsche Bauzeitung (db), 70 – 77.
Knippers, J. (1998). Zum Stabilitätsverhalten tonnenförmiger Stabschalen. Stahlbau, 298 – 306.
Schober, H., & Knippers, jan. (1998). Fassaden und Glasdächer der Deutschen Bank in Berlin. GLAS Architektur und Technik, 5, Article 5.
Knippers, J., Bulenda, T., & Stein, M. (1997). Zum Entwurf und zur Berechnung von Stabschalen. Stahlbau, 66, 31 – 37.
AbstractDer Beitrag beschreibt den Einfluß von Stablänge, Stabsteifigkeit und dem Stich-zu-Spannweiten-Verhältnis auf die erreichbare Traglast von Stabschalen. Daneben werden Überlegungen zur Wahl der rechnerischen Ersatzimperfektionen angestellt. Diese sind nicht nur für die Stabschalen von Interesse, sondern lassen sich auf die Berechnung von beliebigen stabilitätsgefährdeten Strukturen übertragen.
Knippers, J. (1997). Bahnsteigüberdachung Fernbahnhof Spandau. AIV Forum, 02/1997.
Knippers, J., & Harbord, R. (1994). A mixed/hybrid FE formulation for solution of elasto-viscoplastic problems, Part II : dynamic loading conditions and bending problems. Computational Mechanics
, 231–240. https://doi.org/10.1007/BF00350226
AbstractA mixed/hybrid FE formulation for the solution of elasto-viscoplastic problems under dynamic loading conditions is presented. The constitutive equations under considerations are those of Chaboche. The spatially semi-discretized system of ordinary differential equations is numerically integrated in time by means of a midpoint type algorithm. A layer-model is developed which enables the application of the proposed methods in shell or plate theory. Numerical examples demonstrate the efficiency of the proposed method.
Harbord, R., Knippers, J., & Gellert, M. (1992). A mixed/hybrid FE formulation for solution of elasto-viscoplastic problems. Computational Mechanics
, 173 – 184. https://doi.org/10.1007/BF00350184
AbstractA mixed/hybrid FE formulation for the solution of elasto-viscoplastic problems is presented. The spatially semi- discretized system of ordinary differential equations is numerically integrated in time by means of a midpoint type algorithm. Stability considerations are discussed and conditions for its maintenance are established. Illustrative numerical examples demonstrate the ability of the proposed method to reproduce elasto-viscoplastic behaviour. Comparison with known results is also made.