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Über dieses Buch

Textile composites and inflatable structures have become increasingly popular for a variety of applications in – among many other fields – civil engineering, architecture and aerospace engineering. Typical examples include membrane roofs and covers, sails, inflatable buildings and pavilions, airships, inflatable furniture, airspace structures etc.

The ability to provide numerical simulations for increasingly complex membrane and inflatable structures is advancing rapidly due to both remarkable strides in computer hardware development and the improved maturity of computational procedures for nonlinear structural systems. Significant progress has been made in the formulation of finite elements methods for static and dynamic problems, complex constitutive material behaviour, coupled aero-elastic analysis etc.

The book contains 14 invited contributions written by distinguished authors who participated in the Second International Conference on Textile Composites and Inflated Structures held in Stuttgart, 2-4 October 2005. The meeting was one of the Thematic Conferences of the European Community on Computational Methods in Applied Sciences (ECCOMAS, www.eccomas.org ).

The different chapters discuss recent progress and future research directions in new textile composites for applications in membrane and inflatable structures. Part of the book focuses in describing innovative numerical methods for structural analysis, such as new non linear membrane and shell finite elements. The rest of the chapters present advances in design, construction and maintenance procedures.

This volume contains state-of-the-art research and technology for design, analysis, construction and maintenance of textile and inflatable structures and will be of interest to civil engineers, architects, and materials scientists.

Inhaltsverzeichnis

Frontmatter

Innovative Developments in Fiber Based Materials for Construction

Fiber based materials for construction are in a continuous development. Due to the progress in polymer science and knowledge in process engineering important properties can be improved continuously or sometimes in great steps.
ITV Denkendorf in the south of Germany, close to Stuttgart, is here in charge for improvements, testing and for the development of new materials. A comprehensive industrial and scientific network with competent partners is the best base. In this chapter some examples are given from successful material developments in the research fields of fiber spinning, textile formation, coating, testing and numerical simulation with improved material properties for construction applications like: reduced ageing by new coating processes; selfcleaning surfaces based on bionic knowledge; barrier functions against heat, sound, temperatures, electromagnetic waves.
Special materials for new applications are in the field of smart materials, renewable energies, lightweight for mobile applications.
Thomas Stegmaier, Heinrich Planck

Finite Element Simulation of the Mechanical Behaviour of Textile Composites at the Mesoscopic Scale of Individual Fibers

A simulation of the mechanical behaviour of textile composites at the scale of fibers is presented in this article. The approach, based on a finite element code with an implicit solver, focuses on the taking into account of contact-friction interactions appearing in assemblies of fibers undergoing large transformations. It allows, in a first step, to compute the unknown initial configuration of any woven structure. Then, adding an elastic matrix to the fabric, various loading tests can be simulated in order to identify mechanical properties of composite materials.
Damien Durville

A Predictive Fabric Model for Membrane Structure Design

A predictive model has been developed to determine the biaxial stress-strain response of architectural fabrics, without the need for biaxial testing. Sawtooth and sinusoid models of the fabric unit cell have been formulated, with spring elements between crossovers used to represent the coating. In both models a constant yarn cross-sectional area has been maintained, resulting in a relationship between unit cell length and yarn thickness which eliminates the need to determine the yarn crushing stiffness. A state-of-the-art biaxial test rig and new test protocol have been developed to fully ascertain the stress-strain behaviour of structural fabrics. This enables meaningful comparison to be made between the model output and actual fabric response. The model provides a more accurate representation of fabric behaviour than current industry best practice (i.e. use of elastic constants based on biaxial test data), but without the need for specialist testing or equipment.
Benjamin N. Bridgens, Peter D. Gosling

Modelling Fabric-Reinforced Membranes with the Discrete Element Method

A model for fabrics and fabric reinforced membranes is presented, in which the Discrete ElementMethod (DEM) is applied to a microstructure representation of fabrics on the yarn level. The unit cell is described by discrete mass points and rheological elements. Their assembly represents the relevant deformation mechanisms like crimp interchange, trellising or locking. Additional interaction mechanisms are implemented that account for a coating or embedding of the fabric. In the framework of a Discrete Element description the model is intrinsically dynamic since the equations of motion are solved numerically for every mass point using a predictor-corrector scheme, i.e. an explicit finite difference method. With this model the influences of different microscopic material features on the macroscopic system response are studied, preserving directly the information of the local microstructure deformation. All micromechanisms are implemented in a modular manner in order to make the model adaptable to materials that range from pure fabrics to fabric reinforced membranes. Numerical results are presented that demonstrate the plausibility of our approach.
Dirk Ballhause, Manfred König, Bernd Kröplin

Introducing Cutting Patterns in Form Finding and Structural Analysis

In the design of membrane structures, one encounters the problem of “non-developability”. The final membrane structure is doubly curved, but has to be built from flat panels. Due to this discrepancy, additional stresses arise in the structure. Methods are presented for including these stresses in the form finding procedure and structural analysis for a more realistic representation of the actual stress state.
Johannes Linhard, Roland Wüchner, Kai-Uwe Bletzinger

Kinematics in Tensioned Structures

Movement in tensioned structures can be found on three different layers. On the microscopic layer the sliding of molecular chains in polymer fibers or the sliding in the crystalline grid in steel wires is used get material with high strength. On the second layer tensioned structural elements such as cables, belts and fabric made of high strength wires and yarns are showing several movements under tension influencing the stress and strain behavior, the long term behavior and the possibility of folding and bending with less strain. On the third layer the behavior of tensioned structures is described by movement and strain less deformations depending on the curvature, pretension and installation process.
Rosemarie Wagner

Pneumatic Formwork for Irregular Curved Thin Shells

After studying the historical background, the suitability of pneumatic formworks for the construction of irregular curved thin shells was examined, as an answer to modern double curved architecture. Part of the study is the design of the pneumatic formwork for an irregular curved thin concrete shell. Several measures to obtain the required shape were studied with a membrane engineering program. Guidelines for the design of pneumatic formwork are derived.
Petra C. van Hennik, Rogier Houtman

Static Analysis of Taut Structures

The article presents a general framework for the nonlinear equilibrium analysis of taut structures, such as cables and membranes. Distinction is done between geometric and constitutive stiffness, and all the relevant matrices for truss and membrane finite element static analyses are derived, including the effects of sliding cables and following forces (such as wind pressures). The peculiarities of the design of taut structures are briefly discussed, considering the design of an existent membrane structure as a benchmark.
R. M. O. Pauletti

Analysis of Free Form Membranes Subject to Wind Using FSI

Membranes are extremely light and slender constructions which results in a high susceptibility to wind-induced deformations and vibrations. For the analysis of the complex aeroelastic phenomena, emerging from the interaction of the structural response and the wind flow around it, a partitioned fluid-structure interaction method is proposed. Nearly massless structures interacting with incompressible fluids demand for an iterative coupling scheme, which is enhanced by adaptive under-relaxation for stability and efficiency. The performance of this approach is analyzed in several real-world examples.
Roland Wüchner, Alexander Kupzok, Kai-Uwe Bletzinger

Membrane Structures Formed by Low Pressure Inflatable Tubes. New Analysis Methods and Recent Constructions

This paper shows applications of a recently developed thin shell element adequate for the analysis of membrane and inflatable structures. The element is a three node triangle with only translational degrees of freedom that uses the configuration of the three adjacent elements to evaluate the strains in terms of the nodal displacements only. This allows us to compute (constant) bending strains and (linear) membrane strains using a total Lagrangian formulation. Several examples, including inflation and deflation of membranes and some practical applications to the analysis, design and construction of membrane structures formed by low pressure inflatable tubes are presented.
Eugenio Oñate, Fernando G. Flores, Javier Marcipar

Nonlinear Finite Element Analysis of Inflatable Prefolded Membrane Structures under Hydrostatic Loading

Due to their flexibility shell or membrane like structures subjected to gas or fluid loading or gas/fluid support undergo large deformations. In order to describe this deformation dependent loading, where value and direction of the pressure loading are a function of the current configuration of the shell structure, the gas or fluid volumes, which are enclosed by the thin walled structure, have to be considered for the appropriate constitutive equations. Then the numerical formulation of the fluid or gas loading can be derived via an analytical meshfree description for the fluid/gas, which yields a special structure of equations involving the change of the gas or fluid volume respectively the change of the wetted part of the shell surface, see [2, 1113]. This procedure finally leads to the so-called load-stiffness matrix, to which (in the case of enclosed gas/fluid volumes) several rank updates describing the coupling of the fluid or gas with the structural displacements in addition to the deformation dependence of the pressure load [15] are added. The numerical examples of e.g. (a) deploying simply folded membrane structures and (b) multi-chamber structures containing fluid and air in arbitrary combination demonstrate, how the simulation of structures with static gas and fluid loading or support can be efficiently performed without discretizing the fluid respectively the gas.
Marc Haßler, Karl Schweizerhof

Advanced Capabilities for the Simulation of Membrane and Inflatable Space Structures Using SAMCEF

SAMCEF Mecano is a general implicit non-linear software developed by Samtech. The paper describes several improvements that have been made in SAMCEF Mecano concerning the analysis of inflatable and membrane structures. Most of these developments have been carried out in the frame of an ESTEC contract (PASTISS project). Several examples illustrate the different developments.
Philippe Jetteur, Michaël Bruyneel

Structural Air — Pneumatic Structures

This paper shows the possibilities of pneumatic structures for practical applications. The basic principles of pneumatic structures are presented. A number of projects where pneumatic technology is combined with conventional construction methods are presented.
Bernd Stimpfle

Recent Developments in the Computational Modelling of Textile Membranes and Inflatable Structures

The task of computer-modelling for stressed membrane surface structures is considered. Following a brief introduction the handling of inflatable structures are described. Finally, some evaluation tools are shown. Flexibility ellipsoids help to estimate the sensitivity of mechanical systems; redundancy numbers can be used to determine the accuracy for the production. The so-called force finding helps to find an appropriate state of prestress for primary structures which is shown in examples. It follows an automatic procedures for again and again tasks in the cutting pattern calculations.
Dieter Ströbel, Peter Singer

Backmatter

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