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Figure 8: Buckling study with scaled displacements. Left: Stone shell without stiffeners, load factor 1.24. Right: stone shell with metal stiffeners, load factor 2.2.
In both cases buckling would occur in the lower area of the outermost edge. This behavior is quite typical of shells that frequently show vulnerability at the edges. In the case of the proposed design the lower shell areas feature larger forces as self-weight and post-tensioning force combine. The structural depth of the metal stiffeners changes from 29 mm to 75 mm over the length of the undulating surface.
FROM:
Martin Bechthold (Harvard University School of Design), “New stone shells: design and robotic fabrication”, Proceedings of the International Association for Shell and Spatial Structures (IASS), Evolution and Trends in Design, Analysis and Construction of Shell and Spatial Structures, 28 September – 2 October 2009, Universidad Politecnica de Valencia, Spain
ABSTRACT: The research explores the design and analysis of a thin marble shell that incorporates the latest developments in fabrication technology and computational analysis. Natural stone, one of the oldest and most traditional building materials, is used in innovative ways by manipulating it with a 6-axis robotic waterjet. The research studies techniques for the robotic perforation and surfacing of natural stone, with a particular focus on marble. The work was conducted in collaboration with Monica Ponce de Leon and Wes McGee at the Harvard Graduate School of Design (GSD). Small tests panels explore how transparency and translucency of stone can be generated through robotic waterjet cutting. A prototypical stone shell is designed to further explore the design potential encountered in the small test pieces. The shell is post-tensioned and stiffened with metal stiffeners. Finite-element analysis (FEA) serves as a primary technique to conduct a detailed structural analysis of the shell.
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