Current research conducted at TU Delft focused on utilizing structural Topology Optimization (TO) for designing large monolithic cast glass structures with maximum stiffness and minimum mass. These structures demonstrated improved manufacturability in terms of time, energy, and cost efficiency due to their mass efficiency, which results in shorter annealing times. However, the complex geometries and customization of these forms posed challenges in terms of fabrication.

The manufacturability of intricate glass structures is explored by analysing and comparing three possible fabrication methods for three-dimensional glass structures with complex and customized geometries. The methods examined are:

(i) Kiln casting in disposable moulds,
(ii) Waterjet cutting and lamination of float glass panes,
(iii) Additive manufacturing of glass.

The assessment of these methods is based on a set of criteria related to structural performance, visual quality, fabrication limitations, and sustainability. This comparative study act as a guide to the design of a case study and the selection of the preferred fabrication method. An all-glass topologically optimized bridge observatory in Vikos Gorge, Greece, is chosen as the design case. Based on the comparative study and a set of soft criteria, casting in disposable moulds is selected as the preferred fabrication method.

However, glass casting currently faces major drawbacks that restrict its potential. The two main drawbacks that this thesis tries to address are:

Rough and opaque surface quality (main focus): This issue is tackled through laboratory experimentation with the aim of achieving good surface quality immediately after demoulding. The experiments involve the use of different types of disposable 3D printed sand moulds (3DPSM) and application of refractory coatings and coating combinations at various maximum firing temperatures.

Lack of redundancy: Redundancy is explored though research by design and the implementation of design strategies (segmentation, zoning, fabrication methods combination) to ensure the feasibility of the structure.

The end result of this thesis is a comprehensive study on how an all-glass structure with complex and customized shape can be realized. The experimental part of the research yielded improved results, indicating that the combination of refractory coatings and 3DPSM has the potential to bring such glass components to life, reduce the need for post-processing, and simplify the fabrication process.

Given the limitations of time and knowledge within a master’s thesis, further research is suggested to validate and evaluate the results obtained.

This thesis is part of a larger ongoing research project at the TU Delft regarding structural glass as a novel construction material. Here, the focus is directed towards the casting of glass to create complex free-form geometries. Thus far, only smaller components have been created, but a multitude of previous student work explored how the current limitations in the fabrication process could be overcome by using topology optimization to design larger cast glass components. This thesis continues this research by integrating the limitations and remarks concluded from previous work to further explore the potential of designing large cast glass components using topology optimization.

This thesis intends to contribute to the existing research by creating a tool for the design of 3D optimized cast glass components, which can take into consideration the structural properties of glass as well as manufacturing, annealing and specific design criteria. The tool is created in Matlab, using the SIMP optimization method with 8-noded hexahedral finite elements for the structural model.

From the literature review it was concluded that the SIMP methodology is best suited the requirements of this project. For the structural model, 8-noded hexahedral elements were selected. Two algorithms were developed: one with a compliance based objective and a second with a volume based objective.

The algorithm’s performance was tested on different domains. To facilitate comparison with existing literature, the algorithm was initially calibrated with a domain width of one element, effectively creating a two-dimensional optimization. Subsequently, its performance was assessed through the application of a small three-dimensional problem. Finally, the algorithm is used to design a case study involving the structural slab of a small pedestrian bridge located inside the British Museum.

The results validate the benefits of the 3D algorithm. The geometries optimized in three dimensions have a higher structural stiffness and offer more spatial insight. Moreover, the volume optimizations results in a larger material reduction than those achieved in two-dimensional optimizations. For this reason, the volume-optimized component was selected for post-processing and implementation in the final design.

Glass has been widely used in the construction industry since the early nineteenth century. It was most commonly used in the form of a window, which is a flat glass panel. Glass has natural optical properties and is resistant to weather, making it ideal for use as a facade material. Glass’s novel applications in the built environment have led us to go beyond its 2D application of flat glass panels to a solid, 3D component, as seen in recent projects such as Maison de Hermes in Tokyo and Crystal House in Amsterdam.

Currently, there are two approaches in glass blocks: load-bearing solid glass blocks with poor thermal properties and hollow glass blocks with optimal thermal properties but no structural performance. Can we combine these approaches and develop a glass block with good load-bearing and thermal properties? Research on Hybrid glass blocks is one such topic that investigates the potential of this unique concept. A hybrid glass block is the combination of solid and hollow glass blocks designed as a single product with good thermal performance and load-bearing capacity.

The existing research on this topic is promising and noteworthy for further development as it conceptualises the rudimentary design guidelines for the system. The output of the existing research is oriented towards the design development of the novel hybrid glass blocks, ideation of the production methodologies, and validation of their thermal performance. Thus the scope for further research and development is actual prototyping of the design concepts, validation of the structural performance, and qualitative analysis. It is observed that the shape of the hybrid glass blocks impacts the structural-thermal performance, production methodology, and desirability of standardisation. Thus, to develop this product a thorough investigation and exploration are necessary.

The research first focuses on developing design guidelines for the innovative hybrid glass system. A product development methodology is formulated to guide and aid the design process of the hybrid glass block systems. Various design concepts are explored in-depth for each design problem based on their relationship with the structural-thermal performance, manufacturing, and assembly process and are then assessed through a set of design criteria to develop a final design concept. The final design concept is further refined based on manufacturing standards and challenges. The final design is then detailed and implemented in the Academy of Arts, Maastricht (case study), and various assembly strategies for dry stacked cast glass systems are formulated.

To validate the design a prototype manufacturing is done by using a kiln casting method. The prototyping challenges, observations, and decisions aid to assess the practicality of the design. A hybrid method of numerical and experimental validation is considered to evaluate the design based on its feasibility for application in the building industry. This research proves to be a guide for developing hybrid glass block systems and provides them with a design development, manufacturing, and evaluation framework to design, develop and assess their concepts.

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.

The building industry is a significant waste contributor. Especially at the end-of-life of the building it causes an enormous impact on the environment. Construction solid waste has caused serious environmental problems. Reuse, recycling and reduction of construction materials have been advocated for many years, and various methods have been investigated. However, the effectiveness of its applications seems limited. Waste will be reduced by extending the lifetime of the materials giving the second life.This research aims to the design of a construction component made of reused train windows of the old VIRM trains of NS. The continuous flow of the train windows due to the renovation of the trains demands a multiadaptable solution that offers different design scenarios.

Cast glass is a promising structural material that has seen increasing use in the build environment over the last year. It offers a great freedom of shape for designers and engineers, beyond the two-dimensional float glass that is still primarily used. Despite this, cast glass in practice has only been used for solid bricks, mimicking traditional ceramic brickwork. Little exploration has been made on the complex shapes that can be achieved in cast glass. One of the largest challenges of cast glass is its slow and meticulous cooling process required after casting, to prevent the occurrence of internal stresses. This costly annealing process is the main limitations for producing large scale cast glass elements in an affordable way. Experience in large scale solid glass mirror castings performed for NASA show that annealing times can be reduced through smart design.
Structural topology optimisation is a design tool for creating light-weight, material efficient elements. Its application has mostly been limited to industrial and aerospace design, though it is slowly being introduced in the built environment as the additive manufacturing required for these geometries becomes more advanced, and affordable. So far, topology optimisation of cast glass design has remained unexplored. The goal of this thesis is to investigate the potential of using topology optimisation as a design tool for complex structural cast-glass elements with a reduced annealing time. For this, a complex-shaped grid shell has been redesigned in glass, using optimised cast glass nodes. The entire fabrication process, from digital design, to physical fabrication using additive manufacturing has been explored.

Transparency is embraced more and more in contemporary architecture and therefore glass has become one of the most important materials in the building industry. In structural glass applications the elements are dimensioned based on stiffness and strength requirements. This research investigates the potential of glass sandwich structures as a way to create planar elements with a high stiffness to weight ratio and reduce material consumption in structural glazing applications. The design focuses on the replacement of the glass floors of the Acropolis Museum in Athens with an aim to a)reduce material consumption, b)eliminate the supporting substructure and c)propose an optimised design. 7 different core topologies are designed and tested by means of a 4-point bending test in a way to assess the optical quality of such structures, showcase their potential and finally assess which configuration is the most suitable to be used in the aforementioned application. The topology that fulfills the structural and aesthetical requirements is furtherly investigated and its structural behaviour is “deconstructed”. The knowledge acquired through this process is used to optimise structurally and aesthetically the panels of the new glass floors.. Finally, a design toolbox is devised which constists of three phases: a)graphical/analytical calculations (predimensioning), b)Finite Elements Analysis (detailed calculation) and c)Bending Tests (evaluation). In general, this research proves the advantage of glass sandwich structures over laminated glass in stiffnes-dominated designs but also discusses the importance of integrating the process of selective distraction into the design.