Topologically Optimised Cast Glass Shell

Abstract

Glass is a material which can be seen as a double-edged sword. Its monolithic, smooth, and transparent look transmits a sense of elegance and simplicity. However, due to its brittle mechanical property, it can create complex engineering challenges when intended for a structural load-bearing application. Many forget glass has a comparable compression strength to steel and excels when compared to the mechanical properties of unreinforced concrete. (Oikonomopoulou, 2019; Ashby, 2006) Until now, there have been 4 primary discovered manufacturing techniques for glass. Float glass has a 25mm thickness limitation. (AGC, 2019) Extruded and float glass cannot form complex 3D geometries. (Roeder, 1971) 3D printed glass is not structurally validated. (Klein, 2015) Cast glass can offer a solution to all of these limitations. (Oikonomopoulou, 2019)
This thesis answers the following question: To what extent can topological optimisation and new fabrication methods be employed to create compressive free-form glass structures? To answer this this thesis will delve into glass, topology optimisation and shell structures. Throughout the thesis it will notice how topology optimisation and shell structures offer solutions to glass related challenges.
Compression Shells are ideal for Glass. Why? Because glass is brittle. This means that it fractures without warning when tension is applied to a crack. Glass has a low tensile strength but a very high compressive strength. That is why shell structures are ideal for glass as they experience compression only loads. (Adriaenssens et al., 2014) Shells best utilize the strengths of glass and avoid testing its weakest limitations.
Annealing time is one of the most challenging aspects of cast glass. As the volume/mass ratio increases the annealing time increases exponentially. (Oikonomopoulou, 2019) This means careful consideration should be attributed to decreasing this time. This thesis used topology optimisation as a tool to decrease the thickness and thus the annealing time. This thesis explains structural optimisation and evaluates different topological optimisation approaches and software. At the end a 43% mass reduction was achieved.
The goal in this thesis was to design an 6x6m booth from cast glass for the martial district exhibition. After the shell was topologically optimised and structurally validated by means of finite element analyses, the booth was designed for manufacturing, transportation and assembly. The booth was subdivided to fit in trucks and be assembled using spider cranes. The manufacturing procedure was developed using additively manufactured sand mould designs. Demountable and reusable connections, and foundation designs were also developed for the shell.