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Design and Optimisation of Elastic Gridshells

  • This thesis investigates and describes the design and structural behaviour of elastic gridshells. Elastic gridshells are shell structures composed of a single- or multi-layer grid of continuous profiles, which are initially straight and will be progressively bent until achieving an architecturally and structurally satisfactory geometry. Usually used as medium to large span surface structures, elastic gridshells present a wide variety in their surface geometry, grid configuration and materiality. One important structural criterion of elastic gridshells is the high residual stress to which they are subjected after the bending process. Using materials with high limit strain, the residual utilisation rate can be reduced. In the first part of the work, the structural aspects to be considered on the design procedure of elastic gridshells are described and identified on existing design approaches. Then, the mechanical properties of available materials, suitable for elastic gridshells, have been compared and application examples have beenThis thesis investigates and describes the design and structural behaviour of elastic gridshells. Elastic gridshells are shell structures composed of a single- or multi-layer grid of continuous profiles, which are initially straight and will be progressively bent until achieving an architecturally and structurally satisfactory geometry. Usually used as medium to large span surface structures, elastic gridshells present a wide variety in their surface geometry, grid configuration and materiality. One important structural criterion of elastic gridshells is the high residual stress to which they are subjected after the bending process. Using materials with high limit strain, the residual utilisation rate can be reduced. In the first part of the work, the structural aspects to be considered on the design procedure of elastic gridshells are described and identified on existing design approaches. Then, the mechanical properties of available materials, suitable for elastic gridshells, have been compared and application examples have been presented and illustrated. Elastic gridshells offer significant cost and time advantages during the production, transport and construction processes. Nevertheless, the shaping of the initially flat grid also generates important bending stresses on the structures, reducing therewith their bearing capacity against external loads. In order to diminish the initial stresses, profiles with low sections and materials with low modulus of elasticity are usually chosen. However, this leads to a reduction of the global stiffness of the gridshell which can result in stability problems. With an optimisation of the grid pattern - orientation and arrangement of the grid profiles - a minimisation of the profiles’ curvature can be obtained and the load-bearing capacity of the gridshells improved. In the second part of the thesis, an optimisation method based on variational principles for regular and irregular gridshells is proposed and different case studies presented. The aim of using variational principles is to establish extremal functions which minimize the value of quantities related to particular grid properties. These properties are: the curvature of the profiles, the distance to a target surface geometry and the deviation of the edge lengths from a desired mesh size. The advantage of this method is that weighting factors can be applied to the grid parameters to be minimised, so that a variety of grid configurations can be established responding to different specific requirements. The bending process and load-bearing behaviour of elastic gridshells can be analysed using three-dimensional finite element models. During the shaping of the profiles, internal forces are induced on the structure, so that the final equilibrium shape of the gridshell will be attained once its edges have been fixed, the bracing elements have been assembled and the external shaping forces have been removed. The goal of the numerical analysis is to quantitatively evaluate the geometry and material stresses resulting from the shaping process and the load-bearing capacity of the gridshell under external loading. In the third part of the thesis, the influence of the orientation and arrangement of the grid profiles on the residual stresses after erection process and on the distribution of forces and deformability of the gridshell under external loading are analysed on three regular anticlastic gridshells with varying grid pattern. Moreover, the potential and limitations of using tensile membranes as restraining and at the same time covering element of elastic gridshells are studied on a hemispheric regular elastic gridshell. Numerical techniques are commonly used for the calculation of stress distributions and displacements of complex indeterminate bearing structures. Nevertheless, to model the elements they are composed of and the connection properties between them, simplifications and approximations are done. The purpose of the fourth and last part of the work is to analyse the influence of these simplifications on the results of the simulation and thereby recalibrate and benchmark the numerical models with physical prototypes. Two gridshells composed of GFRP profiles have been built: an irregular hemisphere of 10 m diameter, braced with a third layer of profiles, and a regular hemisphere of 5 m diameter, restraint with a tensile membrane. The prototypes have been loaded symmetrically and asymmetrically applying point loads at the grid nodes and the resulting nodal displacements have been compared to those calculated with the numerical models.zeige mehrzeige weniger

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Metadaten
Verfasserangaben:Dr.-Ing. Elisa Lafuente Hernández
URN:urn:nbn:de:kobv:b170-9942
Gutachter*in:Prof. Dr.-Ing. Christoph Gengnagel, Prof. Dr.-Ing. Olivier Baverel
Betreuer:Prof. Dr.-Ing. Christoph Gengnagel, Prof. Dr.-Ing. Olivier Baverel
Dokumentart:Dissertation
Sprache:Englisch
Datum der Veröffentlichung (online):16.03.2016
Veröffentlichende Institution:Universität der Künste Berlin
Titel verleihende Institution:Universität der Künste Berlin, Fakultät Gestaltung
Datum der Abschlussprüfung:16.10.2015
Datum der Freischaltung:24.03.2016
Freies Schlagwort / Tag:discrete differential geometry; elastic gridshell; form-finding; numerical analysis
GND-Schlagwort:GitterschaleGND; Numerische MathematikGND; DifferentialgeometrieGND
Seitenzahl:150
Fakultäten und Einrichtungen:Fakultät Gestaltung
DDC-Klassifikation:7 Künste und Unterhaltung / 70 Künste / 700 Künste; Bildende und angewandte Kunst
Lizenz (Deutsch):Keine Lizenz – Urheberrechtsschutz
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