Unveiling the third dimension of glass

摘要

Glass as a material has always fascinated architects. Its inherent transparency has given us the ability to create diaphanous barriers between the interior and the exterior that allow for space and light continuity. Yet, we are just starting to understand the full potential, properties and characteristics of glass as a material. Only in the last decades did we discover the structural potential of glass and started to use it, besides as a cladding material, also for load-bearing applications thanks to its high compressive strength. Indeed, at present the structural applications of glass in architecture are continuously increasing, yet they are dominated by a considerable geometrical limitation: the essentially 2-dimensionality imposed by the prevailing float glass industry. Although glass panels can stretch more than 20 m in length, the maximum monolithic thickness by this manufacturing method remains a mere 25 mm. As a result glass structures are currently dominated by virtually 2-dimensional, planar elements and confined to the limited shapes that can be achieved by those.This research focuses on the exploration of cast glass as a promising, 3-dimensional construction material in architecture. The main aim of this research is therefore to investigate the potential, as well as the constraints, of cast glass components for the engineering of transparent, 3-dimensional glass structures in architecture.By pouring molten glass into moulds, solid 3-dimensional glass components of virtually any shape and cross-section can be made. Owing to their monolithic nature, such components can form repetitive units for the construction of freeform, full-glass structures that are not sensitive to buckling. Such structures can take full advantage of the high compressive strength of glass, sparing the necessity of additional supporting elements. To achieve cast glass structures, it is essential to use an intermediate material between the individual glass components that contributes to the structure’s stiffness, ensures a homogeneous load distribution and prevents early failure due to concentrated stresses triggered by glass-to-glass contact. To maximize transparency, this intermedium should be colourless and any additional substructure should be minimized.Accordingly, the main scientific contribution of this research work is the design, development and experimental investigation of two distinct systems for selfsupporting envelopes of maximized transparency: An adhesively bonded glass block system, using a colourless adhesive as an intermedium and a dry-assembly, interlocking cast glass block system, employing a colourless dry interlayer. Although,nbsp;in this work, both systems have been developed for self-supporting envelopes, the results can be used as a guideline for further structural applications of cast glass components in compressive elements, such as columns, arches and bending elements, such as beams and fins.At present, the load-bearing function of cast glass in architecture remains an uncharted field. Discouraging factors such as the lengthy annealing process required, the to-date non-standardized production and the corresponding high manufacturing costs, have limited cast glass to only a few realized architectural applications. As a result, there is a lack of engineering data and a general unawareness of the potential and risks of employing cast glass structurally. Hence, in order to accomplish the research goal, all pertinent aspects of a cast glass structure should be tackled, ranging from cast glass’s production method to practical implications when building with cast glass. These distinct aspects are addressed through the formulation of the research sub-questions, which in turn define the different chapters of this dissertation. Accordingly, the presented work is divided in four parts.Part I provides the Introduction to the Research, and aims at giving a brief summary of the involved challenges, identify the research gap and introduce the research questions and the research methodology.nbsp;Part II focuses on the Theoretical Framework of the Research. It lays the foundations for this dissertation and contributes to the scientific field of structural glass by providing the first comprehensive literature review and state-of-the art overview of cast glass structural applications. Initially, the material compositions and production methods for solid cast glass components are explored. Then, to address both possibilities and limitations in the size and form of cast glass components, an overview and critical assessment of the largest produced monolithic pieces of cast glass is made. Given the limited published scientific output on this specific field, an extensive field research was conducted in order to derive the relevant data. The discussed examples, although coming from different fields of science and art, provide great insight into the practical implications involved in casting as a manufacturing method. Subse