Publisher
Challenging Glass Conference 8 will be held 23 & 24 June 2022 at Ghent University and is organised by Prof. Jan Belis (Ghent University), Dr. Freek Bos (TU Eindhoven) and Prof. Christian Louter (TU Delft).
Cover image: Apple Marina Bay Sands, Singapore
Photographer: Finbarr Fallon
Published:
2022-06-20
Front matter
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Welcome at Challenging Glass 8!
We gradually emerge from two difficult years of the covid-19 pandemic raging through the world in waves of constantly changing intensities. The associated uncertainties really put the ‘challenging’ into Challenging Glass this time. Still, some of our peers are not able to join us in Ghent, and they will be sorely missed. Nevertheless, we are happy to be able to return this year to the ‘real thing’: a live event which allows the international glass community to finally meet again in person. An excellent opportunity, especially within the... -
Keynote Speakers at Challenging Glass Conference 8:
- Stéphany Le Rhun – Eckersley O’Callaghan
- Prof. Julian Jones – Imperial College London
- Prof. Markus Feldmann – RWTH Aachen
- Robert Capel – Octatube
- Iris Rombouts – Octatube
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Sponsors of Challenging Glass Conference 8:
Platinum Sponsors:
Gold Sponsors:
Architectural Design & Geometries
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The presented research investigates loose sand forming as a reconfigurable molding strategy for custom glass parts. Doubly curved glass parts usually require the labor-intense fabrication of individual ceramic or steel molds. Reconfigurable molds for glass are limited to specific modular geometries and require costly heat-resistant actuation mechanisms. Three-dimensionally (3D) printed sand molds for glass slumping require binders and cannot be reused. The objective of this research is to facilitate a waste-free fabrication of doubly curved glass elements and a facile, fast, low-cost...
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Up to now, fabricating cast glass components of substantial mass and/or thickness involves a lengthy and perplex annealing process. This has limited the use of this glass manufacturing method in the built environment to simple objects up to the size of regular building bricks, which can be annealed within a few hours. For the first time, structural topological optimization (TO) is investigated as an approach to design monolithic loadbearing...
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The presented research investigates a digital fabrication method for custom glass building elements based on three-dimensionally (3D) printed molds. Custom glass parts with specific geometries usually require several steps of manufacturing, highly specialized craft, or machinery. Computer Numerical Control (CNC) milled steel molds are only suitable for large lot sizes due to their high cost and limited geometric freedom. Lost-wax casting requires several steps of manufacturing and post-processing. This paper investigates an accessible, low-cost process for shaping glass artifacts using...
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Glass surfaces are characteristic elements of façades and make a significant contribution to the authenticity of architectural monuments. Glass as a material is considered an important testimony of its time. Depending on the manufacturing process, it differs both in surface and material composition. The period of high modernism (ca. 1880-1970) overlapped with the technical developments of the industrial revolution, which led from manual production to industrial production. The further development of manufacturing processes as well as the dimensions and qualities of the glass thus shaped...
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For designing and constructing a glazing façade the analysis of the foreseeing structural movements must be considered from the first steps of the project. This basic assessment could become quite complicate for those projects where large displacement are expected or just for projects where the design intent would not allow to use standard solutions. Frequently, when working with large glass units, the movement issue must be analysed in detail. The purpose of the presentation would be introducing different approaches to be considered when developing a glass façade concept. Which are the...
CertBond COST Action CA18120
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Glass/steel adhesive joints are being used increasingly in the construction industry as they offer significant structural advantages over conventional mechanical fastener approaches. However, adhesive joints are also known to be sensitive to moisture diffusion into the bondline, which reduces the interfacial bonding strength for hybrid glass/steel substrates. The effect of moisture on the performance degradation of glass/steel adhesive joints has been successfully predicted assuming adhesive property degradation but requires experimental determination of the affected moisture ingress...
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This paper presents a study on the development of a bonded edge seal for fluid-filled insulating glass units. Such novel façade elements enable multifunctional building envelopes and an improved energy efficiency of buildings. The bonded edge seal of a fluid-filled glazing is highly stressed due to the hydrostatic pressure that acts in addition to typical loads on façades. The permanent exposure to the fluid may also cause severe aging effects. Therefore, the edge seal is designed in such a way that the chemical and physical stress splits on two functional zones. The first functional...
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Cast glass is a promising, three-dimensional expression of the material for architectural and structural applications, particularly for the creation of all-transparent, self-supporting structures and envelopes. Typically applied in the form of solid blocks, cast glass components can be used as repetitive units to comprise fully-transparent, cast glass masonry walls. To maximize transparency and ensure an even load distribution, the glass blocks are bonded together by a colourless adhesive. Currently, there is a lack of standardized structural specifications, strength data and building...
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The main goal of Anti-Shatter Films (ASFs) applications for structural glass is to create a barrier able to keep together fragments and minimize risk after any impulsive or static load that could lead glass to cracking. The influence of ASF properties on the flexural strength of coated glass elements is thus a relevant topic for safe design purposes, but still little investigated. To this aim, an experimental material investigation is presented in this paper, in order to achieve a good knowledge of common ASFs from a chemical point of view. Moreover, the deterioration of mechanical and...
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The desire of builders and architects of maximum transparency and homogeneous surfaces in glass façades and glass structures extends to interior all-glass applications such as glass partitions or all-glass doors. In conventional glass systems the interconnections are performed by eye-catching fittings and clamping details that reduce the transparency and disturb the aesthetics. Novel glass–plastic-composite panels show a significantly reduced self-weight by composition of a polymer polymethylmethacrylate (PMMA) interlayer core...
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Glass became a very popular building material in recent decades. Modern architecture often works with glass facades, roofs, banisters or columns. However, using glass elements in structures may be problematic due to glass elements connections. The connection must bear all stresses arising during the lifetime period and meet high aesthetical standards at the same time. Various bolted and adhesive connections were developed in order to achieve as transparent look as possible. The embedded laminated connection combines mechanical and adhesive fixing systems. The ongoing research at the...
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Glass is an attractive, transparent but brittle material which is increasingly popular in civil engineering. Not only small and secondary glass structures such as canopies or railings, but also load-bearing structures or structural elements such as stairways, beams, facades, etc. are commonly designed today. The wider use of glass places demands on the connections of glass-to-glass or glass-to-other materials. Mechanical connections are commonly used owing to their known mechanical properties but there is pressure to use adhesives for their considerable advantages. Unfortunately, there...
Design Philosophy & Structural Safety
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This paper presents the casting of volumetric glass components from glass waste as an alternative glass-recycling approach. The approach is characterized by its flexibility to accommodate a variety of compositions and ability to yield volumetric (solid or thick-walled) glass products that can tolerate higher contamination rates without a significant compromise to their properties. The novelty of the proposed glass-to-glass recycling method lies in the “as-received” recycling of glass waste, using relatively low forming temperatures (750–1200 °C). This reduces both the need for expensive,...
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In recent years, it has become popular for superyacht designs to incorporate large uninterrupted glazed areas in the superstructure. Larger windows increase the amount of natural light that enters the yacht and add to the yacht’s aesthetic appeal and exclusivity. Cruise vessels and other types of passenger ships have seen similar trends. However, window panes are currently isolated from the structural loads within a vessel and their dimensions are restricted by the presence of a frame as a conventional load-bearing structural component. The use of load-bearing glass components presents a...
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Façades are one of the main elements that affect indoor environmental quality (IEQ) in buildings and building performance. Given the increasing development of sensor technology, the collection of building monitoring data is useful to understand whether the building and in particular the façade system performs as designed. The increasing use of Technical Building Management (TBM) as well as Building Automatic and Control System (BACs) has been demonstrated to be a promising method to decrease the energy consumption and increase the indoor comfort in new and existing buildings. This...
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All-glass structures have become increasingly popular with architects and builders in recent years. Glass surfaces are becoming larger and more impressive, while connections are being decreased to obtain maximum transparency. The supporting structure of glass facades, glass roofs or walk-on glazing is mostly made of metal. One of the reasons for this are the fire protection requirements. To increase the overall transparency load-bearing glass structures have recently been given more attention. However, their use is currently still limited due to the concerns about glass performance in...
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Interlocking cast glass assemblies are a promising solution for architectural cast-glass applications aiming for high transparency and a reversible structure that allows the reuse of the glass components (Oikonomopoulou et al.,2018; Oikonomopoulou,2019b). In such a system, an interlayer material between the glass elements is essential, to assist the homogenous stress distribution and account for the surface microasperities of the glass elements. Towards circularity, this material should be dry (and not an adhesive), allowing for the eventual disassembly of the system....
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The mechanical performance of pedestrian structures attracts the attention of several studies, especially with respect to unfavourable operational conditions or possible damage scenarios. In terms of vibrations, for example, specific customer comfort levels must be satisfied, depending on the class of use, the structural typology, the involved materials, in addition to basic safety requirements. A special consideration should be given to in-service systems that are possibly affected by degradation or even damage, and thus potentially unsafe for pedestrians. In this regard, the...
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The worlds spectacular skylines host tall and slender buildings to create a maximum of office, residential and commercial space on a minimized footprint. These structures need to cope with increasing wind forces at height and are additionally affected by wind-induced vibration due to their lower natural frequencies. The resulting vibrations make users uncomfortable. Therefore, heavy tuned mass dampers are installed in structures and occupy valuable space especially in the costliest top-floors. As an example, Taipei 101’s steel damper is located between the 87th and...
Glass in Facades
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This paper is the first in a series on the behavior of Closed Cavity Facades (CCF) under thermo-mechanical loading excitations. CCF are a novel trend for high performance double skin façade solutions, supplying high performances in terms of thermal and acoustic insulation and providing valuable benefits in terms of maintenance cost reduction. However, existing calculation methods adopted for double skin façade glazing verification under wind and climatic loads do not seem accurate to capture the particular behaviour of the CCF. In particular, the permeability of a CCF air cavity is...
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This paper is the second in a series on the behavior of closed cavity façades (CCF) under thermo-mechanical loading excitations. CCF are a novel trend for sustainable high quality double skin façade solutions, characterized by a minimal maintenance demand. The air cavity is designed according to stringent air tightness requirements, provided with a small dry air flow that preserves the relative humidity, minimizing the risk for condensation and dust ingress. This extremely reduced permeability, with respect to typical double skin design, gives a scenario in conflict with the general...
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Closed Cavity Facades (CCF) are a novel trend for high performance double skin façades, providing a valuable benefit in terms of maintenance cost reduction. Current structural codes contain incomplete and conservative assumptions about the wind load sharing design for this type of multiple skin. In addition, in most codes glazing skins are investigated as separated structural glass elements, while it would be more appropriate to consider the structural interaction between the two skins. Indeed, the the CCF structural behaviour key is the air cavity response to wind loads and the way the...
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From early 20th century architects have envisioned transparent buildings such as Mies van der Rohe’s “skin and bones” concept and his 1921 proposal for the Friedrichstrasse Skyscraper competition in Berlin. One hundred years on, there is a much better understanding of the energy consumption implications of highly glazed buildings, yet architects, developers and users are still attracted to fully transparent facades. This paper sheds some light on the challenges to build with high performing glazing façade systems (originally called curtain wall systems) while efficiently utilising...
Hybrid & Composite Glass Components
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The use of thin glass promises to enable a variety of construction industry pursuits. In addition to the ecological benefits of more efficient use of resources, architects can anticipate new design freedoms with thin glass. Based on the sandwich theory, the flexible thin glass can be combined with a 3D-printed open-cell polymer core to form a very rigid yet lightweight composite element. This paper presents an exploratory attempt on the digital manufacturing of thin glass composite façade panels with an industrial robot. It explains the idea of a digital “file-to-factory”-workflow which...
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The new World Trade Center site was rebuilt after 9/11 comprising seven mayor skyscrapers around the memorial site and the 9/11 museum. Between WTC 2 and WTC 3, Santiago Calatrava’s Oculus Station spans its wings in the NY air while finally, the complex is completed by the “The Ronald O. Perelman Performing Arts Center”. This building sets a one-in-a-kind visual appearance to the area. Its four-sided, 42 m tall, even facade is made from 4736 equal-sized insulated glass panes. More specifically, the architectural vision is to create a marble stone front covered with glass which results in...
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Previous research has evidenced that by adding a ductile reinforcement on the tension side of a glass beam, for instance by adhesive bonding, its post-cracking behaviour and redundancy were improved, while an additional pre-stressing of this reinforcement further helped to increase the initial cracking resistance. Past investigations used steel tendons or stainless steel strips, which required rather complex setups and procedures for mechanical pre-stressing. This study aims to introduce an easier-to-apply procedure with strips made of an iron-based shape memory alloy (Fe-SMA), which...
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This research revolves around the design, fabrication and testing of tubular glass columns, with particular focus on their redundancy and fire-safety mechanisms; moreover, addressing aspects such as: the column shape; cleaning and maintenance; end connections; geometric tolerances in the glass and demountability. Two alternative circular hollow (tube) column designs are initially developed and engineered to address these aspects, namely: the MLA (Multi Layered with Air) and the SLW (Single Layered with water). In both concepts the main load-bearing structure consists of two concentric...
Insulating Glass Units
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The Vacuum Insulated Glazing is a highly thermally insulating structure consisting of two (or more) glass sheets, separated by an evacuated gap, and sealed hermetically at the glass edges. An array of support pillars maintains the separation of the panes under the constant load of atmospheric pressure. The performance and durability of the VIG, in terms of thermal loads and atmospheric pressure, has been well studied and ISO Standards have recently been published (ISO 19916-1:2018 and 19916-3:2021). However, the mechanical performance of the VIG, especially when exposed to dynamic loads,...
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Free-form façades with bent glass are becoming increasingly popular. As bending glass provides it with a better resistance to out-of-plane loads, it can result in thinner glass. A promising new technique is to cold bend thin glass plates with a stiff structural edge into a hyperbolic paraboloid (hypar), and to subsequently lock the corners to create a self-contained, self-stressed system. In this study, the bending process of specially-fabricated double glazing units (‘panels’) is investigated with a focus on a local instability phenomenon. The hypothesis that this instability...
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Curved and free-form glass façades represent a clear trend in architectural design. Hot bending is the most common technique used to produce curved Insulating Glass Units (IGU). Although its effectiveness has been proved in many projects, it is well known that it can also be very expensive due to the big number of moulds usually required to build up a free-form façade. As alternative to the ‘hot-bending’ technique, the increasingly used ‘cold-bending’ method is investigated in this paper being less expensive as well as more sustainable. Such method consists in imposing an out-of-plane...
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The analysis of load-bearing capacity and the determination of blast protection levels for ordinary glass windows and façade components in buildings is known to represent a design and research issue of crucial importance. In the same way, reliable methods to address this issue are mostly based on cost and management expensive experimental investigations on full-size samples. According to the tendency of recent years, this paper presents some of major outcomes of Finite Element (FE) numerical methods and simulations that have been explored in the framework of the GLASS-SHARD research...
Joints, Fixings & Adhesives
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Silicone sealants have a long history of successful use in high performance windows and curtainwalls, such as structural glazing (bonding) systems which can contribute to bomb blast mitigating window designs. Previous experimental work illustrated the increase in strength and elongation for silicone sealants at the typically higher strain rates of blast loading. These values have been used as design values for joint dimensioning. With the advent of more sophisticated analysis methods using finite element analysis software and the...
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Since the early 2000s, an increasing number of globally reported fires in tall buildings, which have spread quickly, have been attributed to the façade. These dramatic events have raised concerns regarding the fire risk posed by materials used in façades and inside the building. Improved performance in both reaction to fire and fire resistance is a necessary requirement for construction materials. Silicone is used in many locations of the façade and buildings, such as sealing of linear joints or firestopping of penetrants in fire-rated walls and floors. Standardized testing enables the...
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Previous research has shown that glass beams with external, mechanical post-tensioning along their edges show better structural performance than glass beams without any such reinforcement. The initial and post-fracture load-bearing capacity of glass beams can be increased by reinforcing them with stainless steel or fiber-reinforced plastic (FRP) tendons that are post-tensioned and connected to the beam edges. However, post-tensioning of stainless steel or FRP bars or strips is complex and challenging because it often requires special setups, such as hydraulic jacks. Iron-based shape...
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The brittle material behaviour of glass means that stress concentration features, such as geometric discontinuities (e.g., drilled holes) and mechanical connectors can weaken the structural efficiency of some glass structures. The poor structural efficiency due to the stress concentrations usually makes annealed glass unsuitable in applications where stress concentrations present, such as glass–bolted joints. Laminated and tempered glass are preferred in building construction industry due to their high strength and safe failure behaviour, respectively. However, laminated and tempered...
Laminated Glass & Interlayer Properties
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Minimizing metallic primary structures in directly glazed grid shells is key to increasing transparency. Complete renunciation to a substructure results in the glass itself bearing the loads, with thin glass shells, for example, that support loads mainly via membrane forces. A 4.20 m tall, double-curved, frame-less modular glass shell with stainless steel fittings laminated into the thin interstice of two-ply laminated safety glass has been developed and built as a demonstrator to validate the concept. The fittings used to structurally join the glass modules transfer all translation...
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The temperature dependent linear viscoelastic material behaviour of the most commonly used interlayer PVB is typically determined by means of Dynamic-Mechanical-Thermal-Analysis (DMTA). By horizontally shifting the isothermal modulus curves, a mastercurve is created at a certain reference temperature, which can then be mathematically approximated with a Prony series. A time-temperature superposition principle can be derived from the shift factors. In contrast to PVB, EVA and ionomer (or ionoplastic) interlayers have semi-crystalline structures that melt when the melting temperature is...
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The method of fibre optic strain measurement based on Rayleigh signal analysis enables the detection of the deformation behaviour of laminated glass and the modelling of its load-bearing characteristics. The measurement system is already calibrated for glass surfaces by studies of Chair of Building Structure at Universität Siegen. In addition to discretely measuring systems, such as strain gauges, the distributed measurement system is particularly suitable for the determination of the interlaminar shear modulus. The sensors used in bending tests on laminated glass supplement the...
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When glass is laminated for safety reasons, it usually blocks UV radiation partially or even completely when UV blocking materials are used. In the last decade, there has been an increasing interest in interlayers with high UV transmission, especially in relation to greenhouse applications. In this paper, we present an overview of the effects of UV transmittance on plant growth and development, in order to advice on the use of the high transmission interlayers versus the standard interlayers. Using UV transmitting films instead of UV blocking films has opportunities to alter plant growth...
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Laminated glass is growing its application in structural entities. The thermoplastic polymeric interlayer plays an important role in transferring force and achieving the composite action in laminated glass, which reveals evident temperature-dependent behavior. In this study, a novel composite interlayer (SGE®) was devised to improve the resistance of laminated glass against environmental actions and to enhance the post-fracture performance. It is comprised of modified ethylene-vinyl-acetate (PVE®) and polycarbonate (PC). Through dynamic mechanical thermal analysis, the...
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Structural interlayers in laminated glass have allowed engineers and specifiers to extend and improve the use of glazing solutions in the construction industry. With the availability of embodied carbon values for these interlayers, it is now possible to assess more accurately the reduction in environmental footprint of laminated glass for construction projects. The Tour Montparnasse tower refurbishment project in Paris was selected as a case study to make a comparison between PVB and structural ionomers in terms of embodied carbon. A 15 % embodied carbon reduction could be achieved using...
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Intended for the construction of a double curved, frameless modular glass shell demonstrator, a stainless steel fitting connection with a trapezoidal, thin sheet laminated into the interstice of two-ply safety glass has been developed. For the bonding within the glass laminate, structural PVB interlayer is used. Various interlayer plies of different PVB types can be stacked depending on the necessary interstice thickness and the intended esthetical appearance. The fitting is designed to mainly transfer translational forces, but it also provides some bending stiffness via a crossbar...
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The structural performance of laminated glass is strongly dependent on the shear coupling offered by the interlayer between the bounding layered and monolithic limits of the glass plies. The most common simplified design approach consists of defining the effective thickness, i.e., the thickness of a monolithic section with equivalent flexural section properties. The Enhanced Effective Thickness (EET) method has been verified to estimate deflection in laminated glass for a range of load and boundary conditions for two-, three-, and multi-ply beams; however, for some static schemes, the...
Numerical Modeling & Experimental Validation
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The bridging behavior between fragments is one vital factor in the post-fracture stage of glass laminates. A particle-based discrete element model was developed in this work to simulate the bridging behavior of fractured glass laminates. The model was based on the calibration of hyperelastic PVB material properties using soft-bond model and further validated with the experimental data as well as the observations from through-crack-tensile tests. In order to investigate the bridging performance of fractured glass laminates with multiple fragments under uniaxial tension, three factors...
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The birefringent properties of glass can be well utilized for non-destructive testing of thermally tempered glass. The surface compression stress as well as the compression zone depth of thermally tempered glass is commonly measured with a scattered light polariscope. The measurement with scattered light polariscope provides information about stresses acting perpendicular to the measurement direction. Therefore, the measurement depends on the direction. In order to make a statement about the rough level of the prestress, a measurement in one direction can be sufficient, assuming an...
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The well-known concept of stainless steel reinforced laminated glass enables to achieve post-fracture capacity and ductility in transparent members. It has been experimentally demonstrated before that this hybrid concept satisfies safety criteria for statically determinate structural elements, as well as statically indeterminate beam systems. However, research on two-dimensional structural frame systems still lacks in literature. Exploiting the post-fracture behavior of such systems requires joints complying with the resistance of its connecting members. This paper presents a numerical...
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In the structural design of facade glazing, various types of loads such as dead weight, wind and climatic loads (pressure differences) must be taken into account. In practice, however, there are many cases of damage that can be attributed to direct solar radiation. In these cases, a so-called thermally induced fracture takes place, which can occur as a result of large in-plane temperature differences within the glass. Due to the increasing complexity of glazing constructions, this load type should be taken into account in future glass design. For this reason, thermal-mechanical...
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Civil engineering design and industry are continuously evolving with the support of advancements in technology. Digital tools are able to assist designers in solving several issues with more accuracy and minimized efforts. In parallel, maximization of human comfort is a target for various design procedures, where mathematical models and standardized protocols are conventionally used to optimize well-being of customers. Major challenges and troubles can indeed derive, structurally speaking, from human reactions, which are related to a multitude of aspects, and may further enforced by...
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Laminated glass has been introduced to improve the mechanical performance, in particular impact resistance, of float glass while maintaining its transparency. However, its rate-dependent behaviour has not been sufficiently understood and various methods have been used to model it. This study compares the response of three material models commonly used to model glass cracking implemented in industry-standard LS-DYNA software: a smeared fixed crack model with the Rankine failure criterion, the nonlocal failure criterion by Pyttel...
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In this experimental research a transparent thermoplastic manufactured by the DOW Corporation and known as Surlyn is investigated for use as an interface material in fabrication of an all-glass pedestrian bridge. The bridge is modular in construction and fabricated from a series of interlocking hollow glass units (HGU) that are geometrically arranged to form a compression dominant structural system. Surlyn is used as a friction-based interface between neighbouring HGUs preventing direct glass-to-glass contact. An experimental program consisting of axial loading of short glass columns...
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For the design of façade and roof glazing, loads due to dead weight, climatic loads (IGU - pressure differences), wind and snow are well investigated and are considered in engineering practice. However, glass constructions are also ex-posed to thermally induced stresses due to direct solar irradiation. The standards and guidelines available so far, both nationally and at the European level, are partly outdated or contain only simplified instructions and specifications for calculating thermally induced stresses of façade and roof glazing. Within the research project, a variety of façade...
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Glass balustrades are designed to prevent large deflections and high stress peaks under conventional lateral loads. In practice, linear restraints are generally described in the form of ideal linear clamps for glass, to replace the actual geometrical and mechanical properties of restraint components. This means that strong simplifications are introduced in place of multiple details and components expected to offer local flexibility and prevent premature stress peaks in glass. In this paper, attention is given to linear restraints that are commonly described in terms of “clamp” boundaries...
Projects & Case studies
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The 30 Avenue Montaigne in Paris, historical headquarters of Christian Dior on the Avenue Montaigne in Paris is currently undergoing a major refurbishment to be finished by early 2022. The centrepiece of the project is the Jardin d’Hiver , a new contemporary glazed element covering an existing terrace, creating a exceptional space in the project. The Jardin d’Hiver is a 10m high x 17m long x 8m wide box with four glazed faces: the roof, the two short sides and one long side. The other long side is the existing façade of the historical building. It is composed of 24 structural DGU panels...
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This study aims to describe the engineering challenges and decision making encountered during the design of the hybrid steel and glass structure of the Apple Store at Marina Bay Sands in Singapore. The structural scheme, which was developed to fulfil the architectural ambition for the utmost transparency, is documented and assessed alongside early-stage alternative solutions. Particular attention is then given to the innovative use of large glass panels as bracing for the steel superstructure. System robustness and post-breakage behaviour of the glass envelope are analysed, especially...
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Cold-bent glass is seeing increasing adoption in construction projects with non-planar geometries. This paper presents work undergone for a set of four high-rise towers, featuring 11,136 unique cold-bent panels, hundreds of which are pushed beyond 250mm. The panels are all unique, non-rectangular, and in some cases, slightly curved. The challenging geometry complicates the prediction of the final panel shape, which is an essential step for producing fabrication drawings of a panel’s flat shape prior to bending. While Machine Learning is still a nascent technology in the AEC industry,...
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This paper presents a case study for the new slumped glass façade at Tiffany’s flagship store in New York City. The undulating façade of slumped IGU’s encloses a new, three-story addition that sits atop the existing Tiffany & Company building. Taken as a whole, the new façade appears as though it were a semi-transparent and flexible curtain of wave fold drapes, suspended from the roof of the new addition and wrapping its north and west elevations. The IGU’s, many as tall as 5.2 meters, consist of slumped glass outer lites and flat glass inner lites, which are glazed onto...
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This paper showcases the challenges in design, fabrication, and installation of glass projects. The modus operandi of an engineer working with glass is presented and the rationale behind the decisions explained. The first section discusses the motivations in several projects. The life cycle phases of the projects are outlined. The second chapter introduces the importance of conceptual design and generation of options on an all-glass staircase project example. Communication of the design intent is outlined in the third chapter, supported with graphical communication extracted from our...
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The contribution will look at the decisions taken during the materials selection of the Skypool and the consequential complexities of working with an unusual structural material as acrylic. The early analytical solutions will be reviewed and judged on their merits. The criteria will look not only consider the typical engineering principles of strength and stiffness but also delve further into exploring the architectural requirements that are necessary for exposed structures where transparency is key. It will also consider aspects such as...
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Designed by Neutelings & Riedijk and Bureau Bouwtechniek, the Heldentoren (Eng. Hero tower) is a 67 m high residential tower situated in Knokke-Heist at the Belgian coast. On floor level +2, +7, +12 and +17, the curtain wall façade spans two floors and is partially curved with a bending radius of 2.3 m for which 88.2(ANG, PVB)/15(Ar)/88.2(ANG, PVB) hot bent insulated glass units are used. Considering viscoelastic material behaviour of the interlayers, implementing the curved shape of the glazing and performing geometrically nonlinear analyses, however, will structurally result in...
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Polyhedral Graphic Statics (PGS) is an effective tool for form-finding and constructing complex yet efficient spatial funicular structures. The intrinsic planarity of polyhedral geometries can be leveraged for efficient fabrication and construction using flat sheet materials, such as glass. Our previous research used PGS for the form-finding of a 3 m-span, modular glass bridge prototype to be built with thirteen unique hollow glass units (HGUs) in a compression-only configuration. This paper reports its design optimization, fabrication, and subsequent modular assembly process. The...
Strength & Stability
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A comprehensive understanding of the fire performance of construction products is necessary to achieve fire safety of buildings. However, the behaviour of structural soda-lime-silica glass in elevated temperatures and fires is still relatively unknown. Soda-lime-silica glass is susceptible to thermal shock and its changing material properties when subjected to high temperatures makes predicting its behaviour in fire complex. This paper investigates the fracture behaviour and fracture strength of soda-lime-silica glass at elevated temperatures in a range which is relevant for e.g. early...
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The inspection of glass edges is gaining in importance in research, as the strength of a glass edge has been found to be highly dependent on its processing. Glass edges are produced by cutting. Depending on their type, they may be additionally seamed, ground or polished in the grinding process. Cutting and grinding processes create mechanical interference in the brittle material, leaving flaws and cracks in the edge surfaces. The current state of the art presents cutting process parameters which correlate with minor flaws and a high glass edge strength. Research at...
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Among the environmental factors affecting glass weathering are humidity, exposure time, temperature, and the presence of pollutants in the atmosphere. Notwithstanding that the weathering produced depends on numerous factors, the important weathering effect of high humidity may be specifically mitigated by using a good chemical composition for the glass. To evaluate this relationship, flat glass samples from three suppliers were studied. The chemical composition of the samples was determined and the variability in compositions was evaluated to verify to what extent these small differences...
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The desire to apply annealed float glass with their economic and optical advantages is limited by the reduced edge strength due to the cutting process. The edge strength of annealed float glass is a decisive factor especially for insulating glazing due to temperature stress. In standards (e. g. DIN EN 18008), the edge strengths are reduced compared to the surface strength of annealed glass. This is mainly a result of the applied cutting process with the corresponding parameters and the glass handling after cutting. The type of cutting process and the cutting parameters (cutting wheels,...
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Glass material has been widely used in modern architecture. Scratch-induced surface damage of aged monolithic glass panel leads to the strength degradation of material and thus threatens the glass safety. Therefore, in order to accurately evaluate the strength of aged glass elements, it is crucial to extract key damage features including the damage location and depth in a precise way. This study aims to develop a non-contact stage-wise scanning method to extract 3D damage characteristics on glass surface, which can further facilitate the investigation into the associated influences on...
Thermal, Acoustic, and Lighting Aspects
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Multiple modern glass and window products based on novel glazing designs, metal-dielectric coatings, and proprietary interlayer types have been developed recently. Advanced windows of today can control properties such as thermal emissivity, heat gain, colour, and transparency. In more recent and more novel glass products, solar energy harvesting through PV integration is also featured. Typically, semitransparent and also highly-transparent PV windows are purpose-designed, to include luminescent materials, special microstructures, and customized electric circuitry. Recently, significant...
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During tempering process, the non-homogenous heating or rapid cooling can induce localized strain in the glass leading to birefringence (or optical anisotropy) phenomenon, a result of the photoelastic effect. Since transmission and reflection coefficients of interfaces at high angles can be quite different with the polarization, inhomogeneous birefringence may manifest as peculiar geometric patterns of bright or darkish shadows or iridescence effects in given polarized observation conditions. The patterns appearance may be at the origin of dispute between the client and the glass...
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Long Range is an experimental acoustic surface comprising 64 hexagonal, slumped glass panes, arranged in two layers of 32 panels each. It exhibits gradients of acoustic behaviors including reflection, diffusion, absorption, and transmission, accessed via modification of the form of glass panes at a variety of scales. Moving from flat panels at one end to increasingly slumped and perforated forms and culminating in deeply curved panels with porous openings, the components of Long Range aggregate into an acoustic and visual system of versatile behavior. The flat end primarily exhibits...
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Color Depth is a material-based research project investigating the optical and structural properties of thick glass. The research is driven by an interest in optical gradients of transparency and color, which are designed through a manipulation of geometric form and composition. These qualities can be attributed to the interrelated optical effects created through reflection, refraction, and volume color, in direct correlation to the geometry of individual glass...
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This contribution addresses the impact of tempering processes on the emissivity of LowE glass. The current status of a measurement series conducted at various tempering sites on different types of LowE glass is presented. Emissivity measurements using inductive eddy current sensors have been made on glass before and after tempering. The obtained data shows an improvement by factor 2 in emissivity depending on coating type. Effects from tempering recipes and the resulting emissivity homogeneity have been analyzed. Measurements also show significant worsening of the...
Thin Glass
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The bending strength of flat glass panels including the effects of their edges, is commonly determined by means of the four-point bending test method. This is an established and reliable method. However, when testing glass thinner than 3 mm, large deformation may occur. This means that the calculated stresses might not correspond to the actual, as the hypothesis behind the small deformation theory does no longer hold. Furthermore, it might occur that the specimen slips out of the supports, compelling the testing impossible. An alternative method, suitable for thin glass, consists of...
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Due to climate change, there will be more extreme weather in the future, such as storms, heavy rain events in combination with hail, and the associated damage to various structural areas of our life such as hail damage to greenhouse envelopes. For this reason, it is important to deal with topics which range from the origin of the hail to the damage caused by hailstorms. The so-called hail resistance classes can be determined in a laboratory using suitable testing equipment and in this case these tests were carried out in the laboratory of the University of Applied Sciences FH Joanneum...
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The strength of chemically pre-stressed glass depends on the depth of surface flaws and the value of the pre-stress. So far, some research has been conducted on this topic; however, there were always uncertainties regarding the flaw depth and the pre-stress profile. Consequently, this research characterises the pre-stress profile using experimental methods. The latter include measuring the depth of layer (DoL) and the surface compressive...
