Challenging Glass Conference Proceedings
Challenging Glass Conference Proceedings collects the conference articles presented at the international bi-annual Challenging Glass Conference and focuses on the Architectural and Structural Application of Glass.
Welcome at Challenging Glass – Anniversary Edition! It is with great pleasure and pride that the 2026 edition will be a milestone marking the tenth edition of our – meanwhile renowned – international conference. We welcome you at the same location where back in 2008 CGC was started by some of us as young PhD researchers: at Delft University of Technology. Especially for this occasion we kick off with a celebration event on Monday evening, with special attention not only to the conference’s Anniversary, but also to the latest progress in standardisation, to two newly launched glass books, and to the ten years existence of Glass Structures & Engineering, the peer-reviewed journal with which we are closely collaborating since CGC5. The conference programme includes about a hundred promising presentations on the latest projects, science, technology and industrial glass developments, in four parallel sessions. No less than three thrilling keynote speakers will challenge you and glass, from different perspectives, on three consecutive days. On Monday, Prof. Ruth Kasper, Convenor Elect of CEN TC250 SC11, will introduce us to the new Eurocode “Design of Glass Structures”. On Tuesday, Mrs. Lynda Estes from NASA will focus on windows for applications in space, such as the recent Artemis II mission to the moon. Finally, on Wednesday, Prof. Liesbeth Janssen will share her intriguing insights on glassy physics – from liquids to living cells. Building on our solid tradition of sharing and spreading knowledge, all conference papers will be published in our open access conference proceedings, while a selection of papers will be published in Glass Structures & Engineering (Springer). Thank you to all authors and speakers for sharing their latest insights and knowledge. Lots of gratitude go equally to the members of our Scientific Committee, who did once again a fantastic job in reviewing all submitted abstracts and papers. Last but not least, profound thanks go to our sponsors, both loyal and new, for their continuous support, without which this conference would not have been possible. Also on behalf of our co-hosts Mauro Overend, James O’Callaghan and Fred Veer, we wish you an awesome conference! Christian Louter, Freek Bos and Jan Belis Conference Organisers June 2026 Conference Organisers & Hosts Prof. Christian Louter (TU Delft), Dr Freek Bos (TU Munich), Prof. Jan Belis (Ghent University) Conference Co-Hosts Prof. James O'Callaghan (TU Delft), Prof. Mauro Overend (TU Delft), Dr Fred Veer (TU Delft) Scientific Committee Prof. Chiara Bedon – Trieste University Prof. Jan Belis – Ghent University Prof. Lucio Blandini – University of Stuttgart Dr Freek Bos – Technical University of Munich Dr Telesilla Bristogianni – Delft University of Technology Prof. Suwen Chen – Tongji University Prof. Paulo Cruz – University of Minho Dr Jagoda Cupać – Technische Universität Dresden Dr Corinna Datsiou – University of Hertfordshire Dr Martina Eliášová – Czech Technical University in Prague Prof. Michael Engelmann – Technische Universität Dresden Prof. Steffen Feirabend – Hochschule für Technik Stuttgart Prof. Markus Feldmann – RWTH Aachen Prof. Laura Galuppi – University of Parma Prof. Christian Louter – Delft University of Technology Prof. Jürgen Neugebauer – FH Joanneum Prof. James O'Callaghan – Delft University of Technology Dr Faidra Oikonomopoulou – Delft University of Technology Prof. Mauro Overend – Delft University of Technology Prof. Jens Schneider – Technische Universität Wien Prof. Christian Schuler – Munich University of Applied Sciences Dr Miriam Schuster – Technische Universität Darmstadt Dr Vlad Silvestru – ETH Zurich Dr Bert Van Lancker – Ghent University Dr Fred Veer – Delft University of Technology Keynote speakers Ruth Kasper - Professor - TH Köln, Cologne, German Lynda Estes - Spacecraft Transparencies Discipline Lead - NASA, Houston, USA Liesbeth Janssen - Associate Professor - TU Eindhoven, The Netherlands Platinum Sponsor Saint-Gobain Gold Sponsors Eastman, Kuraray, NorthGlass, sedak, seele Silver Sponsors Dow, Octatube, Permasteelisa Group, Seen
Copyright (c) 2026 Christian Louter, Freek Bos, Jan Belis https://creativecommons.org/licenses/by/4.0
Engineering Cast Borosilicate Glass for Large-Scale External Façades
Cast borosilicate glass offers significant architectural potential for external façades, but its large-scale use is limited by the absence of established design data and standardised verification methods. This paper presents a performance-based methodology for thick, undulating cast borosilicate glass panels laminated to borosilicate float glass. Project-specific testing was undertaken to determine density, elastic modulus, thermal expansion and bending strength. The strength data were assessed using Weibull statistical methods, comparing EN, ASTM and weighted least-squares regression approaches. A calibrated equivalent-thickness method was developed to translate scanned three-dimensional cast geometries into practical shell models for façade analysis. Structural verification considered self-weight, wind loading, support conditions, local bracket zones and laminated glass interaction. Thermal shock risk was assessed using measured optical properties, local climatic data, solar radiation modelling and façade-specific shading scenarios. The resulting temperature differentials were converted into thermal stresses and checked against probabilistically derived material capacities. The work demonstrates a repeatable framework for combining testing, probabilistic design, finite element calibration and environmental assessment in non-standard façades.
Copyright (c) 2026 Vladimir Marinov https://creativecommons.org/licenses/by/4.0
A Virtual Pipeline for the Evaluation of Optical Distortion in Panelled Glass
Architectural panelled glass lacks an objective method for assessing optical distortion: surface topography captures only reflected flatness (weakly correlated with the through-glass distortion observers report) and visual inspection is neither reproducible nor deployable on installed panels. We address this gap with an image-based methodology that measures distortion as observers perceive it: the apparent displacement of a background pattern seen through the glass, reported as a two-channel field of sphere-equivalent optical power and cylinder-equivalent astigmatism. The methodology adapts Fourier Transform Profilometry and phase-measuring deflectometry to architectural glass, and introduces a reference-free Direct Method that recovers the undistorted grid via a RANSAC homography fit, removing the need for a glass-less calibration and enabling deployment both in-factory and in-situ. We design and validate the Distortion Analyzer within a virtual pipeline of ray-traced simulations with known ground truth. Validation against the Pipeline's independent analytical forward model confirms spatial agreement, convergence under grid refinement, and rotational stability. Physical validation and perceptual calibration remain as next steps.
Copyright (c) 2026 Guillermo Casas, Adrián Betanzos, Louis Moreau https://creativecommons.org/licenses/by/4.0
Visual Performance of a Dual Dynamic Switchable Glazing Assembly in a Field Test Setup
Façades with a high window-to-wall ratio in Mediterranean climates pose substantial challenges in terms of overheating and excessive daylight. The control of glare and privacy is often retrospectively improvised using cumbersome internal blinds, while blocking outward view whilst offering protection against overheating and glare, fixed external shading devices lack adaptability and motorised versions of such often cause long-term issues with their moving parts. This paper discusses the visual performance of a prototype dual dynamic insulated glazing unit comprising of two, independently switchable (solar Polymer Dispersed Liquid Crystal and Suspended Particle Device) interlayers designed to control the visible light transmittance into an indoor space while providing for privacy on demand. Using two identical mock-up offices set up as field test chambers, the visual performance provided by the different states of the switchable glazing prototype are compared to that provided by a conventional static insulated glazing unit under identical field test conditions, with and without conventional internal and external shading devices. Results show that the prototype dual dynamic IGU has a potential to provide for a high degree of adaptability, giving building occupants control over their indoor environment to meet visual performance demands.
Copyright (c) 2026 Etienne Magri, Vincent Buhagiar, Mauro Overend https://creativecommons.org/licenses/by/4.0
Environmental and Economic Assessment of Material Recovery Strategies for Architectural Glazing
The reuse and high-value recovery of architectural glazing offer significant potential to reduce waste and minimize the environmental impact of the glass sector. Still, there is a lack of a standardised approach to support decisions in environmentally efficient renovation pathways that integrate all life-cycle stages and account for varying glazing types, geographical locations, and service-life dynamics. This study develops a novel assessment framework to quantify the environmental and financial trade-offs of alternative glass recovery pathways. The computational framework incorporates life-cycle embodied carbon analyses across material recovery scenarios and temporal energy simulations parameterized by panel geometry, build-up, window condition, and collection site. The framework was applied to six reference glazing products in residential and commercial case studies located in France. It was found that carbon payback periods range from under five years for deteriorated early-generation glazing to well beyond 25 years for non-deteriorated products or products subject to high-infiltration conditions, highlighting the importance of existing building condition in guiding intervention decisions. Under current market conditions, it is shown that despite their embodied carbon benefits, reuse and remanufacturing both incur substantially higher 30-year net present value costs (EUR) compared to recycling recovered glazing and installing new high performance IGUs.
Copyright (c) 2026 Emily Lenarduzzi, Simos Maniatis, Alessandra Luna-Navarro, Michaël Peeters, Hadrien Heuclin, Francois Guillemot, Rebecca Hartwell https://creativecommons.org/licenses/by/4.0
Maximizing Transparency for Glazing Wall Systems subjected to Blast Loading
Advances in blast-resistant glazing have shifted critical design demands to supporting frames, where aluminum mullions may govern façade failure under elevated blast-induced reactions. Ensuring compatibility between glazing capacity and framing performance is essential to achieve balanced, capacity-based façade design and prevent disproportionate damage. This study investigates blast load transfer at the glazing–mullion interface by quantifying demand-to-capacity ratios for aluminum mullions, steel-retrofitted aluminum mullions, and structural steel mullions across varying glazing panel sizes. Edge reactions from double- and triple-insulated glazing layups are obtained through nonlinear dynamic analyses in WINGARD, while mullion response is evaluated using single-degree-of-freedom methods. Results show that high-performance glazing, particularly triple-insulated units, improves glazing survivability but can generate reaction forces exceeding the capacity of conventional aluminum mullions. Discussions on the design, architectural, and fabrication challenges related to each mullion type is provided. The findings highlight the necessity of coordinated glazing-to-framing design, offering practical guidance for achieving code-compliant, blast-resistant façade systems while clarifying trade-offs among compatibility, reinforcement requirements, and architectural constraints.
Copyright (c) 2026 Monjee Almustafa, Matt Soda, Andrew Crosby https://creativecommons.org/licenses/by/4.0
Integrated Thermal and Fabrication Workflow for Structural Frameless Glass Structures
For more than two decades, glass shell structures have shaped architecture for their transparency and strength, traditionally using steel lattices with non-load-bearing glass. This project explores fully glass-based envelopes without conventional profiles, pushing the limits of transparent structural design while targeting material efficiency and CO₂ reduction. It investigates frameless constructions with laminated steel fittings between panes, enabling glass as a load-bearing, thermally effective envelope. Methods combine thermal simulations, structural detailing, and parametric automation. A novel linear fitting system for insulating glass was refined through iterative prototyping, laser welding, and tolerance strategies. Fabrication challenges—especially welding inconsistencies—underscored the need for tighter design-manufacturing coordination. Thermal simulations across five climate zones informed a custom visual programming tool for interactive temperature analysis and design guidance. The parametric workflow automates geometry, fabrication data, and assembly logic for applications from façades to yacht canopies. A full-scale Glasstec 2024 mock-up demonstrated both potential and fabrication sensitivity, highlighting the importance of iterative, feedback-driven development in frameless glass architecture.
Copyright (c) 2026 Gergana Rusenova, Julian Länge, Thiemo Fildhuth , Anna Buksak, Timon Peters, Isabell Ayvaz, Matthias Haller, Roman Schieber, Ulrich Knaack https://creativecommons.org/licenses/by/4.0
Dynamic Modeling of Triple Insulated Glazing Units under Blast Loading using WINGARD
Triple-insulated glazing units (TGUs) are an emerging class of architectural glazing systems offering compact configurations, superior energy efficiency, and enhanced thermal performance while exhibiting high blast resistance capabilities. Despite the growing adoption of TGUs in critical infrastructure and high-risk facilities, there remains a lack of widely available modelling tools capable of efficiently predicting their nonlinear dynamic response under blast loading. Although well-established for modeling monolithic and double-insulated glazing unit (DGU) systems to blast loading, WINGARD does not natively support TGU configurations, posing a significant barrier for engineers designing such blast-resistant façades. This study proposes a simplified methodology for representing a TGU as an equivalent DGU system within WINGARD to comply with General Services Administration (GSA) glazing hazard-rating criteria. The methodology preserves the mass, stiffness, and energy-dissipation characteristics of TGUs while remaining compatible with WINGARD’s input framework. Comparison made against limited experimental data demonstrates that the methodology captures the dominant blast response characteristics of TGU systems. The findings provide a practical, quick-running methodology for engineers to assess TGU blast performance using WINGARD.
Trends in Glass Sustainability in Small-Scale Artistic Businesses and Practices
As global demand for the high-emissions material of glass increases–especially in renewable energy infrastructure–there is a critical need to rethink and reform current practices. While large-scale industry adapts slowly, glass art presents a unique opportunity for agile innovation and leadership in sustainability. Sustainability in the artistic sector for smaller glass businesses is present in three sectors: production, innovation and themes/discourse. Trends in the increased usage of recyclable glass is most prominent in small businesses, often locally sourced. According to an ongoing survey - completed by glass artists, studios and educational institutions- sustainability practices include: providing any unusable glass waste to construction companies for usage as building material, providing glass offcuts to other local artists that can use the parts for mosaic or fusing, etc. Deterrents included coefficient of expansion (COE), cost and reliability. Innovative approaches include new designs in art itself and even the packaging. Arts allow for more unrestrained experimentation often achieving inconceivable results through the interdisciplinary collaboration with other agencies. Select case studies in this article will examine current trends, innovations, and challenges in sustainable glass-making. It will argue for the essential role of glass artists in shaping a more sustainable future—not only through material practice but also through their ability to engage audiences in critical environmental dialogue.
Copyright (c) 2026 Alise Stopina https://creativecommons.org/licenses/by/4.0
Structural Glass Columns in a World War II German Hangar
In the woods / heather fields north of Arnhem (NL) the German invaders built in 1941 a complete new airfield called Deelen. To allow the airplanes being driven into the maintenance hangars an ingenious wooden roof structure was developed that enabled the complete front wall of the hangar building to be removed. After the World War II this hangar functioned as a storage room for potatoes. Maintenance was minimal resulting in 2010 in a seriously endangered condition of this building. In the meantime the buildings of the old airfield were declared historic monuments. Minimal repairs were undertaken, one of them being the reduction of the roof span of 23 meter by two big steel supports in three parts. The building is now developed to be a centre for small cultural activities. To reduce the big temporarily steel support frames to a functional, and visible, minimum we suggested to replace them by glass columns. We had experimented with glass structures at the Delft University of Technology. Study lead to a bundled column of massive borosilicate glass bars, diameter 30 mm, all glued together in a bundle with a length of about 3.5 meter. Two glass columns, one with a square cross section and one with a hexagonal cross section, were produced by the firm G&SS. Both glass columns were tested in the Stevin laboratory of the University of Technology. The two glass columns could easily carry the maximum safety load of the roof of the old hangar. So they were certificated by the University in short report. In the summer of 2026 the two glass columns will be installed in monument.
Copyright (c) 2026 Rob Nijsse, Ate Snijder, Peter Eigenraam https://creativecommons.org/licenses/by/4.0
Vitroplena designed and installed an all glass pavilion serving as the entrance to a public school. The structure consists of a 3 m by 1.8 m glass box with a height of 2.5 m, constructed from 1010.2 (TTG,sPVB) laminated glass panels—combining thermally toughened glass (TTG) with structural PVB interlayers (sPVB)—that were adhesively bonded on site using a black structural silicone. One side of the pavilion is connected to the existing school façade, while the opposite side remains free standing, and a door is integrated into one of the side panels. The roof panel is slightly inclined to facilitate rainwater drainage. The pavilion is entirely self supporting: all acting loads are transferred through the glass walls and roof via the structural adhesive joints, allowing the box to behave as a single stable entity. Transparency is maximised by eliminating steel connectors and relying solely on glass and adhesive bonds. The design of the glazing and joints was carried out using finite element analyses that accounted for the viscoelastic behaviour of both the interlayers and the structural silicone. This paper presents the design process, structural calculations, and on site installation, and discusses the key challenges encountered. The resulting all glass pavilion establishes a new benchmark in advanced structural glass engineering.
Copyright (c) 2026 Bert Van Lancker, Kenny Martens https://creativecommons.org/licenses/by/4.0
Conjugate Heat Transfer in an Adaptive Façade
As a boundary between interior and exterior, the building envelope and its thermal properties are crucial for heat lost and indoor comfort. Dynamic building envelopes offer the potential to optimize buildings in terms of energy efficiency, save resources, and adapt to the needs of users. EnergySkin is a designed dynamic building envelope, that actively controls heat flow through existing façades by regulating the external wall temperature. Developed as a serial solution, it comprises a mounting system and façade modules. The basic element of the façade modules is an insulated glass unit (IGU). A contacted low-emissivity glass coating functions as an electrical heater. The necessary energy is obtained from photovoltaics integrated into the IGU and from supporting battery storage units included in the mounting system. This paper presents the analysis of internal heat flows, temperatures profiles and fluid flows using numerical methods and computational fluid dynamics. Partial investigations focus on the subsystems of the glazing centre and edge as well as the mounting system. The overall system is examined analysed as a conjugate heat transfer between EnergySkin, the existing structure and an airgap required to compensate for unevenness in the façade. The total results are discussed in regards to its thermal behaviour in the context of heat loss and output demand. Finally, directions for future development of Energy Skin are outlined.
Copyright (c) 2026 Max Stoppel, Pietro Di Biase https://creativecommons.org/licenses/by/4.0
Load Bearing Performance and Breakage Response of Laminated Anticlastic Cold Bent Glass Plates
Anticlastic cold bent glass plate plays a significant role in the design of free-form glass facades. Residual stresses will be introduced in the plate during the cold forming process which may influence the subsequent load bearing capacity. Current research on load-bearing performance of anticlastic cold bent glass plates primarily focuses on the influence of support conditions, cold bending degree, and load patterns. However, effective support conditions for post-cold-bent loading have not yet been determined, and effective failure criteria have yet to be established. In this paper, a series of load bearing tests have been conducted to explore the mechanical properties and failure mechanisms of anticlastic cold bent glass plates. Then, the effective finite element models have been built to systematically investigate the effects of support conditions, cold bending extent, width-thickness ratio and aspect ratio.
Copyright (c) 2026 Xiaohan Hao, Suwen Chen https://creativecommons.org/licenses/by/4.0
Curved architectural glass is becoming central to contemporary façades, enabling designers to move beyond planar surfaces toward more fluid, expressive forms. This paper examines its aesthetic and geometric potential and shows how high-precision forming using controlled curvature adjustment during strengthening supports large-radius cylinders, tight-radius panels requiring high accuracy, and customized double-curved units. Such capability enables smooth 3D transitions, continuous reflections, and dynamic light effects that significantly enhance architectural identity compared with flat glazing. The study evaluates how curvature accuracy affects optical quality and structural reliability, focusing on deformation control, thermal uniformity, and post-strengthening stress behaviour. Multi-curvature geometries receive special attention because precise tuning is essential for dimensional stability and consistent visual appearance across complex surfaces. Selected outstanding projects by NorthGlass illustrate how advanced forming technologies, large-format production capacity, comprehensive measurement, and multi-stage inspection enable complex façade elements that meet strict requirements for strength, transparency, and optical flatness. As architecture advances toward more organic and performance-driven envelopes, curved glass offers the aesthetic flexibility, engineering reliability, and scalable industrialization needed for next-generation façades.
Copyright (c) 2026 Nancy Wang, Bill Gao, Joe Xu https://creativecommons.org/licenses/by/4.0
Analysis of the Life Cycle Energy Impacts of Vacuum Insulated Glass in Manufacturing and Sustainable Buildings
Building energy efficiency targets have sharpened focus on the embodied costs of high-performance products. Vacuum Insulated Glass (VIG) offers a centre-of-glass U-value in the range 0.4–1.2 W/m²K — well below that of conventional Insulated Glazing Units (IGU) — but its manufacturing is more energy and process intensive. This paper presents a hybrid Life Cycle Assessment (hLCA) of VIG production across six manufacturing scenarios, combining process-level expenditure data, based on US manufacturing, with the GLORIA multi-regional input-output (MRIO) database. The hLCA base case — high-temperature solder glass edge sealing — yields a total embodied energy of 543.3 MJ/m² and GreenHouse Gas (GHG) emissions of 108.6 kg CO₂-eq/m², approximately 5.1 and 2.3 times the IGU reference values, respectively. Alternative sealing processes (and the respective materials), including ultrasonic soldering/welding, reduce these burdens by up to 37.5% in energy and 28% in GHG. An operational payback analysis across four US climate zones (ASHRAE 1A–5A) shows energy recovery in as little as 0.6 years and an Energy Return on Investment (EROI) of 7.6:1 to 46.1:1 over a 30-year service life. VIG recovers its manufacturing energy investment many times over, where the magnitude of that return depends directly on the sealing technology implemented in manufacturing.
Copyright (c) 2026 Cenk Kocer, Asiyath Ibrahim, Amanda Irwin, Arunima Malik Malik https://creativecommons.org/licenses/by/4.0
Bespoke Solid Oak Rooflight in a London Listed Building
In 2026, RH will open its first gallery in London, in 7 Burlington Gardens, a grade II* Georgian Mansion. The project, designed by Foster + Partners, involved the renovation of a historic building, including the installation of several bespoke glass rooflights and a scenic lift shaft. Bellapart was in charge of the detailed design and engineering of these specialist works, as well as its fabrication and site assembly. The main rooflight consists of a hipped roof, with a central section composed of triangular insulating glass panels supported by a framework that includes solid oak timber beams and flitch beams. All used timber was visually graded solid oak, rather than laminated, as it is common practice, in order to achieve the natural aesthetics required by the client. The dimensions of the central glazed area are 24.4 × 4.2 m, while the overall dimensions of the rooflight are 27.9 × 10.9 m, with a total height of 4.8 m. Beneath the main rooflight lies the “Oculus” — a walkable glass floor composed of a single laminated glass panel with an elliptical shape, measuring 3.4 × 2.4 m. Additionally, four more rooflights are installed on the terrace of the building. Each features a circular insulating glass panel at the top and a mirror-polished stainless steel inverted funnel at the bottom, consisting in a cylinder on top of a quarter of a torus, which reflects the natural sunlight throughout the entire space. The rooflight set is completed by on composed of six fire-resistant insulating glass panels supported by a steel frame. The insulating glass panels from all rooflights were tested according to CWCT standards, achieving fragility classes 1 and 2. Beyond the rooflights, the scenic lift shaft is constructed from flat and curved laminated glass panels, structurally bonded to a powder painted steel structure.
Copyright (c) 2026 Francesc Sánchez Fontserè, Núria Guitart https://creativecommons.org/licenses/by/4.0
The Structural Design and Wind Dynamic Analysis of the New Glass Envelope for Campo Marzio Railway Station in Trieste
The retrofit and requalification of the historic Campo Marzio railway station in Trieste (Italy) includes the reconstruction of its former vaulted glass roof, a suspended pedestrian walkway to host a restaurant, and a new main façade. The new steel and glass structures reinterpret the original early-20th-century layout through lightweight reticular arches and cold-bent laminated glass panels. The structural verification of the glass components involved seven different typologies for curved and planar panes, which were designed by means of dedicated FEM analyses. The dynamic response of the roof subjected to wind loading represents indeed an important step of the analysis, as the building is in the city of Bora wind. This issue is assessed through coupled CFD and structural simulations. RWIND 2 is first used to evaluate the spatial distribution of external and internal pressures, while nonlinear dynamic analyses are carried out in ABAQUS to capture the vibration modes and the possible aeroelastic amplification effects under turbulent flow. The integrated numerical approach ensures the structural safety and serviceability of the transparent envelope while preserving its architectural lightness and historical identity within a contemporary structural concept.
Copyright (c) 2026 Chiara Bedon, Massimo Ciocca, Gerardo Masiello, Sabato Gargiulo, Nicola Cella https://creativecommons.org/licenses/by/4.0
Residual Risk of NiS Spontaneous Breakages after the Heat Soak Test
Spontaneous glass breakage of thermally toughened glass due to Nickel Sulphide (NiS) inclusions can be largely prevented by a preliminary Heat Soak Test (HST) (Kasper 2018a). This well-established test has been standardised in the EU Norm EN 14179-1:2005. However, according to literature (Kasper – Rubbert 2020), there is a small theoretical probability, that a potentially dangerous inclusion could lead to a breakage even after a well-conducted HST-test. In this paper, a statistical approach will be used to explain the level of residual risk of having a spontaneous breakage of heat soaked, thermally toughened, soda lime silicate safety glass due to the presence of critical nickel sulphide inclusions.
Copyright (c) 2026 Francis Serruys, Philippe Letocart https://creativecommons.org/licenses/by/4.0
Seismic Performance of Point-Fixed Glass Façade Systems
Point-fixed glass façade systems (PFGFSs) are widely used as modern building envelopes. This type of façade is particularly susceptible to seismic action; however, its seismic performance hasn’t been sufficiently quantified. To address this challenge, the seismic behaviour of a 3D steel moment-resisting frame (SMRF) with PFGFS was evaluated. The model includes the SMRF, laminated glass panels (LGP), spider arms, and substructure. The numerical model was analysed for 15 pairs of earthquake acceleration spectra at three levels of intensity. The results clearly indicate that the PFGFS experiences substantially higher seismic demands than the main structural frame. Specifically, inter-storey drift ratios (IDRs) and peak floor accelerations (PFA) values in the façade system were up to 70% and 80% greater than those of the SMRF, respectively, particularly at upper storeys and under Near Collapse (NeC) level earthquakes. These results indicate that the PFGFS does not simply follow the response of the primary structural frame. Instead, the façade system experiences amplified dynamic effects under seismic loading. Therefore, façade systems require independent seismic assessment rather than relying solely on structural frame response.
Copyright (c) 2026 Seyed Amin Hosseini, Sandra Jordão, Carlos Rebelo, Chiara Bedon, Rohola Rahnavard https://creativecommons.org/licenses/by/4.0
Cyclic Out-of-Plane Bending Response of 2-ply Annealed Laminated Glass in the Partially Cracked Stage
The post-breakage security and structural safety analysis and quantification for laminated glass (LG) elements in constructions is a critical issue, and a rather challenging task, due to many influencing parameters and interconnected aspects that are hard to control and quantify. From a practical point of view, among many others, the glass type (and thus the associated size and shape of shards) is one of the most important influencing parameters for the residual capacity assessment in case of damage. The quantification of this residual capacity is carried out in this paper by introducing a sound estimation of the equivalent modulus of elasticity for cracked glass. To this aim, small-scale 2-ply LG specimens are investigated in a cyclic 3-point-bending (3PB) setup, with partial fracture corresponding to the “STAGE 2” of damage propagation for 2-ply LGs. A total of 57 tests is carried out, considering different parameters, such as the interlayer type and thickness, the glass thickness, the imposed deformation rate and amplitude. The comparative analysis of experimental results gives evidence of rather interesting mechanical performances in out-of-plane bending, which are certainly affected by the presence of a broken glass layer in STAGE 2, but still ensuring (even under a cyclic protocol) an interesting residual capacity for the damaged LG section.
Copyright (c) 2026 Chiara Bedon, Nicola Cella, Luca Cozzarini https://creativecommons.org/licenses/by/4.0
Review of Glass Testing Data Sets and Design Strength Models
The design strength models in glass standards have evolved through a range of methodologies, each shaped by the assumptions and data sets available at the time. As there is no ideal model for all situations, new strength prediction models continue to evolve. This paper explores why stress probability integrals are useful for window glass and peak-stress based approaches are more suitable for structural applications, as well as why there is such a range of criteria published. (Can the mean modulus of rupture be 41 MPa (AAMA CW-19) if the 5% fractile characteristic strength is 45 MPa -- EN 16612, CEN/TS 19100, DIN 18008 etc. -- in the same material, and both be right?). Window glass is generally loaded out-of-plane and is thin relative to the target displacement. The resulting failure criterion is complex because the distribution of ‘stressed area’ to total area and biaxial vs uniaxial stress is a function of the load, aspect ratio and deflection to thickness ratio. The second order effects result in the system stiffening with increasing load and the 90% maximum stress profiles change in area and location with increasing load. The maximum stress often occurs on the surface of the panel. By contrast, structural glass applications are generally loaded in-plane, typically slender, with second order effects increasing stress as the combination of initial imperfections and load interact to generate secondary (minor axis) stresses which increase rapidly as the load approaches buckling. The maximum stress often occurs at the edge or connection point of the panel. Key considerations include Griffith flaws, Brown’s integral, flaw orientation, environmental effects such as weathering and self-healing, float glass characteristics, edge processing, and stress distribution patterns across system types. Statistical distributions examined include Normal (Gaussian), Weibull, and Lognormal. In selecting design strength criterion for the Structural Glass Design Manual, the approaches of ASTM E1300, CEN/TS 19100, AS1288 and AAMA CW-12 were examined and conclusions drawn for the merits and limitations of each approach considered relative to its intended purpose.
Copyright (c) 2026 Richard Green, Terrence McDonnell, Andrew Crosby https://creativecommons.org/licenses/by/4.0
Structural silicone glazing (SSG) design typically neglects the adhesive contribution of silicone bonding to glass laminate interlayers, leading to conservative assumptions and increased material use. This study investigates the adhesion characteristics of a commercially available high-performance silicone structural glazing (SSG) sealant to two widely used laminated glass interlayer materials: polyvinyl butyral (PVB) and ionoplast (silicone-interlayer bond strength and durability were experimentally assessed under tensile and shear loading using both non-aged and artificially aged H-shaped specimens. The results indicate that silicone–interlayer adhesion exceeds the intrinsic strength of the silicone, contributing to load transfer in SSG joints. These findings suggest that accounting for interlayer adhesion could improve structural efficiency in applications such as glass fins by increasing the effective bite, thereby eliminating the need for additional glass thickness reduction of silicone volume.
Copyright (c) 2026 Graham Coult, Efstratios Volakos, Valérie Hayez, Allan Gibson https://creativecommons.org/licenses/by/4.0
Innovation in façade design and material efficiency is essential to meeting stringent sustainability targets and reducing the embodied carbon of building envelopes. This study presents full-scale structural testing of unitised façade panels incorporating advanced glass–aluminium bonding technology, in which adhesive connections are utilised to enhance flexural stiffness. Tests conducted under controlled laboratory conditions demonstrate that the system enables structural optimisation while satisfying serviceability and strength criteria, allowing up to a 15% reduction in aluminium framing without compromising performance or service life. In addition, the technology enhances transparency by reducing frame depth, thereby improving daylighting and increasing usable floor area. When combined with appropriate design detailing, it also accommodates glass replacement and allows recycling, minimising non-reusable waste.
Copyright (c) 2026 Andrea Pilla, Pedro Galvez, Andreas Doppmeier, Kiran Kumar Tripathy, Ulli Mueller https://creativecommons.org/licenses/by/4.0
Experimental research on human–façade interaction is essential for advancing user-centered façade and glazing technologies, particularly in relation to serviceability of glass and façade technologies, multi-domain comfort and resilience and acceptance with novel technological approaches. Yet only a limited number of laboratories worldwide provide flexible, reconfigurable, and realistically scaled test environments capable of hosting human participants. The MATELab—originally inaugurated in 2018 in Cambridge (UK)—is one such facility. In 2024, the lab underwent a full relocation and upgrade when the laboratory was disassembled and moved at Delft University of Technology. This paper presents the lessons learned from the relocation process, highlighting both the logistical and scientific challenges of transferring a human–subject testing laboratory across contexts. Beyond documenting the practical constraints of reassembling complex façade test rigs, we discuss how the move enabled significant functional and methodological improvements to better support research on human responses under changing climatic conditions and emerging societal challenges. The insights provided aim to inform future efforts to establish human–facade interaction laboratories and research directions.
Copyright (c) 2026 Alessandra Luna Navarro, Marcel Bilow, Pablo Martinez-Alcaraz, Pedro de la Barra, Tim Jonathan, Atze Boerstra https://creativecommons.org/licenses/by/4.0
Evaluating the Tensile and Shear Properties of an Epoxy for Hybrid Glass-Concrete Structures
The use of adhesives in architectural glass applications is steadily increasing. To date, these applications have primarily focused on structural glass-to-metal or glass-to-glass connections in façades, typically employing flexible adhesives such as silicones and polyurethanes. Recently, however, there has been a growing interest in stronger adhesives, such as acrylates and epoxies, for all glass assemblies and for hybrid structures combining glass with materials including timber, plastics, and concrete. This emerging trend forms the basis of the present research in which glass is combined with concrete. To develop and optimise such hybrid components, finite element simulations can be employed, provided that the adhesive behaviour is accurately represented. For this purpose, experimental testing of both bulk adhesive material and bonded glass–concrete interfaces is required to establish the relevant stress–strain relationships. In this study, the mechanical properties of an epoxy adhesive selected for glass–concrete bonding are characterised through tensile and shear testing. Tensile tests are performed on dumbbell specimens, while compressive double-lap shear tests are carried out on bonded glass–concrete specimens. This paper presents the adopted test procedures based on relevant standards, the fabrication of the specimens, the resulting experimental data, a simplified material model, and the implementation in finite element software for comparison purposes.
Copyright (c) 2026 Bert Van Lancker, Cas Maertens, Jérôme Van Alboom, Roman Wan-Wendner, Jan Belis https://creativecommons.org/licenses/by/4.0
Compliance of Pillars in a Vacuum Insulated Glass
This paper presents an analytical framework for characterising the lateral compliance of a cylindrical column constrained between deformable elastic substrates, with direct application to the contact mechanics of pillars used in vacuum insulating glass (VIG) units; these pillars support the glass panes as a set of discrete array points over the glass surface to maintain separation under atmospheric pressure. Under combined normal and lateral loading, four physically distinct deformation mechanisms were found to contribute to total pillar (column) compliance: column bending, column shear, rigid-body rotation driven by asymmetric substrate indentation, and surface shear of the substrate at the contact interface. Using Timoshenko beam theory for a column, Fabrikant's flat-punch tilting solution for rotational compliance, and contact mechanics solutions for surface shear, the total lateral compliance is expressed as a closed-form superposition. The analytical predictions are validated against three-dimensional finite element models across column heights of 0.1 to 0.5 mm and radii of 0.15 to 0.5 mm with excellent agreement over all cases. This framework will enable rapid parametric optimisation of the pillar geometry in VIG design for any external load configurations.
Copyright (c) 2026 Christian Alter, Cenk Kocer, David McKenzie https://creativecommons.org/licenses/by/4.0
Testing forms an important part of designing structural glass systems. Calculation generally only predicts failure of the mechanisms that are checked for, so rely on the experience and judgement of the designing engineer. However, glass systems lack ductility and are intolerant to incorrect assumptions, so validation testing, even when calculations are well prepared, performs an important role. Design standards with equations for the applicable limit states are available for most structural materials and are the most common approach. “Rational analysis” based on published papers and engineering fundamentals is another approach where there are gaps in the local codes and standards. Another method is “design by testing” which can be a great approach to optimize the design and calibrate the limit state if used correctly. However, as our standards have been advanced to cover more of the limit states with empirical formulas, practicing engineers have had less exposure to “design by testing” and we have seen inconsistencies in the application of this method in practice such as consideration of “validation by testing” to be equivalent to full justification. This paper is intended to walk through the “design by testing” method, highlighting on appropriate references, statistical analysis of the results and the appropriate reliability and safety factors to align with the standardized reliability objectives. The paper will also highlight the difference between “design by testing” and “validation by testing” and discuss the objectives of each approach, how they can be employed in practice, and how they are addressed within the Structural Glass Design Manual.
Copyright (c) 2026 Richard Green, Andrew Crosby, Terry McDonnell https://creativecommons.org/licenses/by/4.0
Glass design standards include an allowance for load duration but are silent on the capacity of glass immediately following a near-design-duration load event and the capacity to sustain subsequent loading. They treat loading events as isolated occurrences rather than cumulative phenomena. Typically, wind loads are treated as 3 second load duration, regardless of the type of storm or the associated gust patterns and cumulative duration. For this to be true, the glass must heal somewhat between the loading events, if not to the level of fresh glass, then healing to the level of surface flaw assumed in the design standard. This paper explores the dynamic nature of flaw-development in glass from fresh to weathered states and self-healing from design-duration-loaded state to re-establishment of design level resistance. In prior research these effects have mostly been treated separately; this paper examines both the mechanisms that contribute to “weathering” and “self-healing” of glass, as well as climatic data in the context of cumulative wind load event duration. Particular attention is given to evaluating appropriate load durations for atypical sustained-wind events such as hurricanes, cyclones, and typhoons. This paper reviews prior material from disparate areas and proposes revised design practices for areas prone to hurricane events. It contrasts window glass and structural glass assemblies and the implications for standardization and design of structural glass.
Copyright (c) 2026 Richard Green, Isabelle Green https://creativecommons.org/licenses/by/4.0
Vast quantities of post-consumer glass from commercial buildings are still lost to landfill due to contamination, logistics, and cost barriers. This paper shares key lessons from implementing a new, scalable pathway to recover end-of-life architectural glass and return it to new building glass. Through strategic partnerships with clients, upskilling the deconstruction supply chain, and stewardship of recovered material, Saint-Gobain has developed a cost- and time-effective closed-loop solution. This initiative is the Saint-Gobain Glass Recycling Process, summarised in a six-step circular flow: (1) Diagnosis – Classification of interior/façade types and glass types prior to dismantling; (2) Dismantling – Controlled breaking of glass to prevent contamination; (3) Sorting – Organisation of acceptable cullet types for recycling; (4) Collection – Arrangement of glass flows to ensure compatibility with flat glass production; (5) Melting – Acceptance and integration of cullet into new glass batches; (6) Projects – Reuse of recycled glass in new facades for construction and renovation. This closed-loop system is applicable across various building lifecycle stages—from demolition to new construction—and exemplifies how industrial innovation can drive climate resilience and material circularity in the built environment.
Copyright (c) 2026 David Entwistle, Hadrien Heuclin https://creativecommons.org/licenses/by/4.0
Recent developments in thin glass technology and flexible edge spacers present an opportunity to addresses notable fabrication challenges in conventional curved insulated glazing units, namely the undesirable visual distortions arising from hot bending the glass and the limited curvatures allowed by the glass strength. This study investigates the structural feasibility of flexible insulated glazing units (IGUs) incorporating chemically strengthened thin glass and a flexible spacer system, with the objective of enabling higher cold-bending curvatures than those achievable with conventional glass façades. And in doing so, the curvature imposed on the thin glass also provides the necessary stiffness to resist loads without excessive deflections. A combined methodological framework was adopted in this study, comprising finite element modelling to predict stress–strain behavior under controlled single-corner bending, alongside experimental validation through prototype fabrication and destructive testing. With additional material-scale mechanical tests to improve the accuracy of the numerical models. It was found that thin-glass IGUs can achieve a curvature ratio of 0.112, representing a 420% improvement on fully tempered IGUs with standard thickness glass. These findings demonstrate that thin-glass assemblies are capable of accommodating substantial geometric flexibility without compromising mechanical integrity, thereby reducing reliance on hot-bent glass in architectural applications.
Copyright (c) 2026 Koen van Deurzen, Mauro Overend, Marcel Bilow https://creativecommons.org/licenses/by/4.0