Glass is a highly durable and infinitely recyclable material, yet in practice only a small portion of architectural glass products re-enters the value chain after its first use. An increasing rate of energy retrofits of the EU building stock will result in replacement of 85% of existing windows in near future; in the current linear glass supply chain, this will generate large amounts of glass waste. Despite high recycling rates of container glass in Europe, window glazing is very rarely recycled into new glazing, and reuse is almost entirely unexplored. For aged glazing to be reused in construction, better knowledge of its surface quality and structural performance is needed. The main objective of this paper is to explore the effects of ageing and exposure to indoor and outdoor environment on the strength of glass. A comparative investigation is undertaken to evaluate the strength and surface quality of the internally, externally and cavity-facing glass surfaces of insulating glass units (IGUs) after 30 years of use in a building envelope in the Netherlands. The glass panes are separated from the IGU assembly and cut into specimens for microscopy and coaxial double ring tests. The study shows that the visual quality is best preserved on the cavity-facing surface, consequently exhibiting the highest bending strength. The internally and externally facing surfaces, with visibly more extensive damage, exhibited similarly lower strengths at low probabilities of failure. When compared to the design strength of new annealed glass acc. to EN 16612, all the surfaces showed a reuse potential, with considerable bending strength.@en

Smart buildings are equipped with automated control systems that provide a comfortable indoor environment, aiming simultaneously at energy savings. Control systems for shading devices applied in practice are mostly driven by a rule-based approach, that is usually tested under simplified conditions and hence its effectiveness in complex real-life cases is questionable. The present study develops an optimized glare-based control strategy for Venetian blinds in a real-life open-space building with totally transparent facades. The research is based on the case study of the Co-Creation Center at the TU Delft campus, which can host three different types of events: presentations, meetings and workshops. The control strategy is developed within Grasshopper, a tool for parametric and optimization problems. Radial Basis Function Optimization (RBFOpt) is utilized for the computation of the optimal blinds’ states. Within the developed control strategy, cylindrical illuminance (Ecyl) is used as a glare index, giving the opportunity to evaluate its performance. Results show that the optimized algorithm can improve the existing visual conditions in the building by an average of 80% for all activity types, although it leads to an average increase of 7% of the time when electric lighting is needed, in comparison to the current rule-based control. Finally, Ecyl displayed an overall agreement of 92.5% with DGP-based glare assessments, proving that in spaces with multiple windows and uncertain occupants’ view direction, a view-independent index can predict glare risks as well as a state-of-the-art view-dependent metric.@en

This article presents the metric avoided carbon for the reuse of aluminium unitised curtain wall façades, that are to be taken from a donor building an applied onto a receiving building. The metric is used to compare seven proposed circular reuse strategies, each showing a different level of reuse. Based on literature and reference studies, we identify those parts of the façade where reuse has the most impact and is technically feasible. The seven reuse strategies and the avoided carbon method are applied on a real case study building as donor project and a fictitious building as receiving project. We conclude that reuse is technically feasible, saves carbon, and that the proposed metric can help to incentivize building owners and project developers to adopt circular reuse.@en

This paper draws attention to the environmental impact of passive smart windows, a novel high-performance glazing technologies that can change their solar transmittance to control the amount of solar gain, thus reducing cooling energy demand. Despite the large influence of building envelope technologies on overall embodied carbon in buildings, the environmental impact of passive smart windows has been inadequately addressed, with a dearth of numerical data on various impact categories beyond energy consumption and Global Warming Potential (GWP). While current literature focuses on the advantages of these technologies in terms of operational energy savings, other critical environmental considerations are currently missing. This paper aims to bridge the existing gap by introducing a novel framework for evaluating the broader environmental impact of passive smart windows through a multi-category LCA method. By analysing the life cycle of these technologies, including production, usage, and disposal, the research seeks to provide a holistic understanding of their contribution to sustainability. The framework is based on systematic literature review on current state-of-art approaches and Interviews with key stakeholders in the dynamic glazing value chain. Literature review and interview results are presented, and then the framework is demonstrated through a case study of a thermochromic technologies for an office building in the Netherlands. Preliminary results show the critical areas where improvements on the methods or on the performance of the technology are required for the achievement of holistically sustainable high-performing glazing.@en

Since the beginning of 2021, CEN/TS 19100 Design of Glass Structures has been available in its first three parts. The fourth part is expected soon. This Technical Specification of the European standards organisation CEN is as a pre-standard of a corresponding future Eurocode. These documents constitute the first ever comprehensive design code for the entire structural glass engineering field on the European market for the first time. In addition to a clear outline, the Technical Specification has been drafted to be compatible with EN 1990 “Basis of Design” and to address glass-specific design matters, particularly related to robustness and redundancy. Although the standard still has the status of a CEN/TS, thereby allowing the European nations the option of whether to introduce it, either in full or in parts, it already contains national openings through which the European countries can adapt the design results to their own safety level by National Determined Parameters (NDPs). Such an approach already anticipates the future Eurocode, which is expected to be published as EN 19100—Design of Glass Structures. This article provides some context on the history and concept behind the new documents and gives an overview of the design rules and the corresponding technical background of the different parts of CEN/TS 19100.

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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 includes Computer-Aided Design (CAD), Engineering (CAE) and Manufacturing (CAM). The research shows a parametric design process to enable the seamless integration of digital analytic tools. Furthermore, this process shows the potentials and challenges of the digital manufacturing of a thin glass composite panel. Here, partial production steps executed by an industrial robot arm, such as large-format additive manufacturing, mechanical surface preparation, bonding and assembly process are explained. Finally, a first insight into mechanical properties of the composite panel are experimentally and numerically investigated and evaluated under surface load. The general concept of the digital design and manufacturing workflow as well as the results of the experimental study provide the background for the integration of further form-finding and analysis methods as well as the implementation of extensive mechanical investigations in future research.@en

Container glass is omnipresent and reuse can be observed all around the world. It can even be reused for the construction of structural components for buildings of which several examples exist around the world. However, research on the reuse of glass for structural components seems lacking. Therefore, this paper investigates the potential of reusing glass bottles for the construction of structural columns. Firstly, the compression strength of artificially abraded glass bottles was investigated in compression tests, revealing a compression strength between 10 and 20 kN. Secondly, alternative assemblies of multiple glass bottles were tested in compression, to determine their suitability for constructing a column. Finally, an exemplary column prototype constructed of glass bottles is presented. From the findings it is concluded that it is feasible to reuse glass bottles for the construction of structural columns that could carry small scale structures.@en

Thin glass is currently mainly used for displays on electronic devices, but it also offers interesting characteristics for architectural applications. Due to its high strength and small thickness the glass can easily be bent in architecturally appealing curvatures, while the small glass thickness (≤ 2 mm) offers a significant weight reduction compared to traditional window glazing. Research at TU Delft and TU Dresden focuses on exploiting these beneficial characteristics for the creation of lightweight composite façade panels. More specifically, composite panels are developed that consist of thin glass outer facings which are adhesively bonded to an inner stiffening 3D-printed open-cell polymer core. Besides the benefits of high strength, high stiffness and low weight, the composite panels also offer the potential to influence daylight entry through customisation of the 3D-printed core pattern. The current contribution highlights the current state of the research activities and describes the concept of the thin glass composite panels, their constituent components and the related digital fabrication process.@en

In the evolution of structural glass beam elements, the requirements for post-fracture load bearing capacity and safe failure behaviour have led to the development of reinforced and post-tensioned beams. Maximum bending capacity in the post-fracture state is normally associated with extensive yielding of the reinforcement, providing a safe failure mechanism through apparent ductility of the composite beam section. This can be achieved as long as the propagation of primary flexural cracks does not compromise the transfer of shear from the load points to the supports. Although shear failure is typically not critical for the ultimate limit state design of ’normal’ unreinforced glass beams, it may govern the load-bearing and deformation capacity in the post-fracture state for reinforced and post-tensioned glass beams. This paper presents exploratory experiments and initial analysis of the shear failure phenomenon in the post-fracture state of reinforced and post-tensioned glass beams. Potential shear transfer mechanisms are identified based on the critical shear crack theory developed for reinforced concrete members and applied in the analysis of shear failures observed in four-point bending tests of post-tensioned glass beams. The behaviour of fractured laminated glass under mixed-mode (tension+shear) loading is explored on a limited set of small-scale double-notched glass specimens, demonstrating the feasibility of the applied test methodology. Preliminary findings of the present study may serve as a basis for further investigations of shear resistance of glass beams. Typical shear failure kinematics and suitable constitutive laws of the applied materials need further investigation in order to provide design recommendations for the prediction of shear resistance of reinforced and post-tensioned glass beams.

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Purpose: Glass material is largely used for load-bearing components in buildings. For this reason, standardized calculation methods can be used in support of safe structural design in common loading and boundary conditions. Differing from earlier literature efforts, the present study elaborates on the load-bearing capacity, failure time and fire endurance of ordinary glass elements under fire exposure and sustained mechanical loads, with evidence of major trends in terms of loading condition and cross-sectional layout. Traditional verification approaches for glass in cold conditions (i.e. stress peak check) and fire endurance of load-bearing members (i.e. deflection and deflection rate limits) are assessed based on parametric numerical simulations. Design/methodology/approach: The mechanical performance of structural glass elements in fire still represents an open challenge for design and vulnerability assessment. Often, special fire-resisting glass solutions are used for limited practical applications only, and ordinary soda-lime silica glass prevails in design applications for load-bearing members. Moreover, conventional recommendations and testing protocols in use for load-bearing members composed of traditional constructional materials are not already addressed for glass members. This paper elaborates on the fire endurance and failure detection methods for structural glass beams that are subjected to standard ISO time–temperature for fire exposure and in-plane bending mechanical loads. Fire endurance assessment methods are discussed with the support of Finite Element (FE) numerical analyses. Findings: Based on extended parametric FE analyses, multiple loading, geometrical and thermo-mechanical configurations are taken into account for the analysis of simple glass elements under in-plane bending setup and fire exposure. The comparative results show that – in most of cases – thermal effects due to fire exposure have major effects on the actual load-bearing capacity of these members. Moreover, the conventional stress peak verification approach needs specific elaborations, compared to traditional calculations carried out in cold conditions. Originality/value: The presented numerical results confirm that the fire endurance analysis of ordinary structural glass elements is a rather complex issue, due to combination of multiple aspects and influencing parameters. Besides, FE simulations can provide useful support for a local and global analysis of major degradation and damage phenomena, and thus support the definition of simple and realistic verification procedures for fire exposed glass members.

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We are delighted to present you the special issue on Intelligent Construction and Automation as part of the Architecture, Structures and Construction journal. This issue covers a diverse range of topics related to the design, conception, and realisation of architectural structures and components, showcasing some of the latest developments in the broad field of Construction and Automation. The 10 papers collected over the past year focus on additive manufacturing (AM), robotic fabrication and assembly, computational design, and large-scale printing technologies. Process automation and 3D printing have been used to explore material and functional behaviour, design paradigms for AM, fabrication processes, and lightweight composite systems. Although Construction and Automation goes beyond 3D printing, these publications clearly demonstrate that additive manufacturing techniques currently hold a prominent place in the field. Moreover, with Artificial Intelligence (AI) gaining interest in the AEC industry, we expect it to appear prominently in future special issues of the Architecture, Structures and Construction journal.@en

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 the development of glass constructions, which had to be made increasingly slimmer over time in order to guarantee a high degree of transparency. Today, historical windows are often replaced by new glazing made of float glass, which can cause the authentic character of buildings to be lost. A team working on the research project at the Technical University of Dresden and the University of Bamberg has therefore set itself the goal of examining in detail the glass and its construction in the period from around 1880 to around 1970. The aim is to define the living character of industrially manufactured glass from the time before the introduction of float glass as an authentic and style-defining feature of the period. The present work focuses on the chronological presentation of the development of glass designs. Furthermore, the development and use of refined flat glass is analysed and presented. This includes wired glass, laminated glass, thermally toughened glass, insulating glass and curved glass. The significance of historical glass constructions for engineers and planners can be derived from the results and the evaluation.@en

Editorial@en

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 inducing an increasing curvature from flat until fracture. The curvature is to be constant along the length of the specimen at any time. The stress at fracture is calculated by knowing the corresponding radius or the applied bending moment. The equipment capable of performing this test is the clamp bender whereby the glass is held by two clamps at the specimen’s ends. Rotational and translational movement combine to uniaxially bend the glass as desired. This paper explores the validity of the clamp bender for testing thin glass by comparing the results generated by three different test setups developed at TU Darmstadt, TU Dresden and AGC. The three individually developed clamp bender setups follow the same principle, but present a few differences in actuation. Using these three clamp bender test setups, identical series of thin glass specimens were tested. The results showed that the glass fracture strength data coming from different setups match quite well one another. This paper discusses the different test setups and compares the obtained glass strength data. It contributes to the development of a universally applicable, simple and reliable test method for thin glass.

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