High Strength Thin Glass as Stiff Structural Fabric

Abstract

Creating smooth, double curved glass façades from thin glass offers highly curved and complex shaped architecture that is less heavy and still transparent compared to conventionally used hot- or cold bent glass. Although bigger curvatures can be achieved with hot bent glass, it requires non-reusable moulds in the fabrication process, whereas cold bent glass does not. This can lower investment costs. This is especially interesting for high strength thin glass, because high curvatures are easily reached by the elastic (cold) bending technique.
To bend flat glass into a double curved shape, the glass can be twisted, resulting in two curvatures in the opposite direction (anticlastic). The technique that is currently used to twist glass is based on a metastable position which depends on the capability of sustaining compressive forces. The thinner the glass, the earlier compressive stresses cause a buckling phenomenon. The radius of the anticlastic curvature reached with the current technique depends therefore on the thickness of the glass.
Replacing conventional glass by high strength thin glass results in a single bent curvature, instead of an anticlastic curvature. Considering the high amount of prestress, high strength thin glass is capable of transferring high tensile stresses and an alternative twisting technique might be more appropriate, that is based on a high tensile stress capability, instead of a low compressive stress capacity. This research explores the great potentials of high strength thin glass by applying an alternative technique that adds tension to the twisting, which in this research is referred to as ‘three-dimensional tensioning technique’.
This study starts by analysing differences in material- and mechanical properties between high strength thin glass and the familiar glass (thicker and less tempered Soda-Lime-Silicate glass) commonly used as a construction material. Currently, the twisting technique that is used appears to be insufficient because of strong membrane behaviour in the high strength thin glass.
Structural performance of high strength thin glass is tested for pure in-plane tensile strength. In this experimental analysis a non-standard test method is used and compared with currently used methods for materials that have ductile or brittle mechanical behaviour.
Several connection methods are illustrated that enable an anticlastic curvature. From a SWOT-analysis it is concluded that the connection needs to be characterized by a discontinuous elastic modulus, or stiffness, along the edge surface, that is able to transfer high tension, yet is strainable to fill the gap-tolerance when creating a hypar (hyperbolic paraboloid) surface.
In this research an optimisation is carried out of a side supported glass element based on an FE-analysis that shows the capability of high strength thin glass used as tensile membrane structure.