This paper is a review of methods to determine optical distortion in architectural glass, with a focus on the methods described in the current available standards and guidelines. Examples from building projects are used as reference points in the review of the methods. In addition to the review initials measurement studies are performed in a laboratory to determine the physical phenomena behind the optical distortion. The paper concludes on the different types of optical distortion seen, the methods which were used for the survey and how it corresponds to the current standards and guidelines, with a proposal for future research directions. Based on the findings in this paper it is suggested that the best method to determine optical distortion is to measure the changes in milli diopters, based on the current methods utilized for monolithic glass when measured in transmission. However, this method would need to be expanded to laminated glass, IGUs and potentially to curved glass, as well as a method to measure optical distortion in reflection. These methods will have to be developed through further research to better understand the causes behind the different optical phenomena. ... Read more

This study addresses the limited understanding of the structural performance of composite sandwich façade panels made with glass and pultruded glass fiber-reinforced polymer (GFRP), which represent a promising alternative to conventional aluminum glazed systems. These panels, measuring 1300 × 600 mm, were experimentally tested under monotonic flexural loading to explore the influence of adhesive type on structural performance, comparing assemblies bonded with silicone-based adhesives to those bonded with epoxy-based adhesives. An initial-stage ANSYS FE model was developed and validated against the experimental results, providing further confidence in the findings and enabling predictive analysis. Key focus areas include analyzing the flexural response and investigating shear lag effects, which are critical to understanding the effective widths and mechanical behavior of glazed composite sandwich panels. The findings highlight that epoxy-bonded panels demonstrate significantly greater stiffness and load-bearing capacity compared to silicone-bonded panels, underscoring the importance of adhesive properties in achieving optimal performance. This research contributes to the development of analytical models that can accurately predict the behavior of glass-GFRP composite panels, providing engineers and designers with essential insights into the mechanical performance of such systems. By demonstrating the feasibility of replacing traditional aluminum unitized curtain walls with glass-GFRP sandwich panels, this study illustrates the potential to create slimmer, stronger, and more durable façade systems with enhanced corrosion resistance. These findings support the transformative role of composite materials in advancing façade panel design for minimalist, sustainable, and architecturally innovative building exteriors. ... Read more

Existing buildings with large glazing ratios within subtropical Mediterranean climates face substantial challenges for thermal and visual control of their indoor environment. Previous research by the same authors has already identified the potential of incorporating both solar–PDLC (polymer-dispersed liquid crystal) and SPD (suspended particle device) switchable films within facades exposed to high solar insolation to provide a wide dynamic range of visual transparencies. This paper identifies a novel application for switchable laminates within a dynamic external shading device that permits the casting of a shadow on demand onto existing fenestration. This study compares the degree of glare within an enclosed space attained by a conventional opaque overhang over a window to that achieved with glass shading overhangs incorporating two types of switchable films. Using a scale model in a field test setting, indoor illumination and glare measurements are investigated under different states of switchable films and compared to those provided by conventional static glazing, with and without ordinary external overhangs under identical field test conditions. Results show that switchable overhangs in their transparent/bleached state can allow the ingress of daylight without creating excessive glare, whereas in their translucent/tinted state, switchable shades can deliver a level of glare protection similar to that provided by an opaque shading overhang. ... Read more

The authors wish to replace the flood hazard map in Fig. 11a with an updated map for the Acerra region. The legend has been revised to display only the minimum and maximum flood depth values.(Figure presented) Fig. 11. (a) Flood hazard map for the Acerra region (Pluvial flooding - RCP 8.5 for year 2050, 50th Percentile - 1000 years return period) overlayed on the case study buildings (highlighted in orange). ... Read more

This book provides a comprehensive overview of structural glass design, covering the entire process from material properties to conceptual and structural design, calculation methods, and real-world applications. It presents glass and its related products—such as polymer interlayers, adhesives, coatings, and supporting materials—as structural, load-bearing components in buildings and other engineering domains. Readers will find detailed insights into fracture mechanics, polymer mechanics, experimental methods, numerical analysis, reliability and risk assessment, and forensic engineering. The book presents both practical design information and detailed background information, thereby providing a bridge between research, engineering practice and education.

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Bio-based composites provide promising low embodied-carbon alternatives to technical materials, but they generally rely on virgin biomass which raises concerns about agricultural land use for non-food crops. Bio-composites made from organic waste address these concerns by providing high carbon-sequestration opportunities with fewer virgin resources. But the sourcing of these waste streams and their impact on the mechanical and functional properties of the bio-composite are poorly understood. This study investigates food industry waste as bulk fillers in bio-composites with a furan resin matrix. Six waste streams were selected based on local availability and current underutilisation. Firstly, bio-composite samples for each filler type were prepared and tested for strength, water absorption and freeze-thaw resistance. Secondly, the two most promising fillers, walnut shell and spent coffee ground, were investigated further, assessing the influence of filler particle sizes and filler content fraction on bending and impact strength. Finally, a carbon impact analysis of the primary production and fabrication was performed to evaluate the carbon footprint of the developed bio-composites, compared to conventional construction materials. With a mean bending strength up to 58 MPa the walnut shells and spent coffee fillers produced the highest performance bio-composites, while variants of cacao bean shells and cherry pits showed blisters and cracking, resulting in lower mechanical properties and higher water absorption. Walnut-based composites benefited from a blend of grain sizes by improving packing density, requiring less resin, while maintaining mechanical performance. The carbon impact analysis showed that a bio-composite with 55 % walnut shell filler is a low-carbon alternative to construction materials such as ceramics, aluminium and steel within the considered life-cycle phases and use case. The findings demonstrate the feasibility of utilising food-industry waste in bio-composites and present the further research needed in the development of these more sustainable materials. ... Read more

Initial material selection and connections between components significantly impact the feasibility of reuse in the built environment. Yet, the link between material selection and construction methods with the ability to reutilise recovered elements is rarely quantitatively assessed. In this study, a novel digitised assessment method to evaluate the environmental reclamation potential of building elements is applied to two contemporary façade systems. The systems are evaluated over a 75-year reference study period in terms of life-cycle embodied carbon and reclamation potential, with consideration for service life deterioration of components. The reclamation potential is evaluated in three recovery scenarios: system reuse; component reuse; and recycling and/or energy recovery. The reclamation potential through system reuse is shown to rapidly decrease in the first few years of the façade system lifetime due to the influence of service life dependencies and the incorporation of irreversible connection types. The findings of the applied assessment provide key insights into design decisions that lead to reduced life-cycle embodied carbon and enhanced reclamation potential over time. The applicability of the assessment to other construction products and future capabilities of the reclamation potential assessment method are discussed. ... Read more

Unitized curtain walls are widely adopted in contemporary architecture for their lightweight construction, aesthetic qualities, ease of installation and high operational performance. They are particularly used in high-rise buildings, where glazed facades are designed to meet a broad range of performance criteria. Well-designed systems tend to perform satisfactorily in normal service conditions, but are more problematic in extreme events. In fact, post-earthquake surveys in seismic-prone regions reveal functionality losses and moderate-to-severe damage to glazed facades, with significant financial, social and environmental consequences. Despite studies on the seismic behaviour of unitized curtain walls, research in this field remains limited. In particular, experimental studies to date rarely assess both serviceability and ultimate limit states, fail to fully characterize the sequence of damage states until collapse and overlook the influence of design choices on the façade performance. To address these gaps, an extensive experimental campaign on full-scale unitized curtain walls was conducted to investigate the seismic behaviour of façade units, including variations in geometry, joint aspect ratios and type (dry-glazed or wet-glazed), frame detailing. The experiments involved quasi-static and dynamic loading, considering in-plane, out-of-plane and vertical movements. Air infiltration, water leakage and wind resistance tests were conducted before and after low-intensity shaking to assess the post-earthquake façade serviceability. Analysis of experimental data highlighted the significant influence of silicone joints on glass rotations and the structural strength hierarchy. Fragility curves were derived from damage observations, which revealed weather-tightness loss at a 0.71% drift ratio and silicone failure in specimens with low-displacement capacity frames. ... Read more

Building energy prediction models expedite performance assessment and assist in decision making, from early-stage design to retrofit planning at single- or multi-building scales. However, the number of parameters involved in the energy performance evaluation often impede the prediction process requiring the assimilation of high-dimensional, uncertain input. This is compounded further at multi-building scale e.g. urban energy modelling, due to the increased complexity of evaluating diverse building geometries. While single-building sensitivity and uncertainty analysis is well-established for identifying the most influential input parameters and evaluate the uncertainty effects on energy demand, these are hard to generalize at multi-building scale which remains relatively unexplored. The present study advances existing research by applying a variance-based sensitivity analysis to assess the impact of varying (i) building façade layout, (ii) envelope thermal properties, (iii) envelope air tightness and (iv) building occupancy. The analysis is conducted for multiple buildings under two future climate variations, while also considering the degradation of material thermal properties. The latter is derived from known deterioration models for single-building uncertainty propagation, relying on experimental and simulated data. The approach is applied to a temperate oceanic climate with particular focus on the Dutch building stock, including a sample of buildings with diverse geometric characteristics in Rotterdam. First-order Sobol indices are computed to evaluate the impact with respect to the heating, cooling and total energy demand. Our findings indicate that infiltration is the most influential factor for heating energy demand, whereas cooling is mostly affected by the envelope thermal properties and, particularly, window solar heat gain coefficient. Common patterns regarding the impact of insulation across different envelope components can be identified among buildings with similar orientation and compactness ratio indicating the importance of considering these geometric properties in retrofit decision-making workflows. ... Read more

The built environment is vulnerable to climate-induced extreme events and natural disasters, which are repeatedly exposing communities to severe consequences and market disruptions. In response, the construction industry is developing resilient technologies for buildings, but the proposed solutions are often not cost-effective, rarely eco-friendly and typically fail to address multiple hazards present in many locations. These shortcomings stem from the absence of a clearly defined framework for quantifying holistic multi-hazard resilience. As a result, investment decisions are ill-informed and technical solutions are sub-optimal. This paper redresses this issue by proposing quantitative indicators and introducing the Resilience Readiness Levels to assess the resilience of buildings, considering multi-domain factors (physical, social, economic, environmental) in single or multi-hazard contexts (heat, seismic, wind, flood). The proposed resilience indices and calculation methods are based on a diverse set of scientific literature and real-world practices, and are demonstrated on Dutch and Italian urban blocks with different local hazards and building layouts. The results show that the multi-domain resilience approach can support informed early-stage building design and retrofit decision-making for single hazards, while aiding prioritization and intervention planning for improving building disaster preparedness in multi-hazard scenarios. ... Read more

Ongoing research at TU Delft focuses on recycling low-quality glass by casting it into volumetric elements, under the assumption that bulk flaws, and thus compatible contamination, have little influence on the volumetric component's strength. However, to validate the structural behavior of volumetric glass with significant bulk flaws, a corresponding uniform tensile testing method is needed that is not governed by the surface quality of glass and thus, can trigger bulk flaws. This research explores the applicability of the Theta-specimen (Durelli et al. 1962), as a method for measuring tensile strength of volumetric cast glass, while avoiding the main drawbacks of a direct uniaxial tensile test. Three theta-sample geometries are evaluated using FEA, and by mechanical testing of 4-5 CNC waterjet cut float glass specimens per geometry. Polarized light is used to visualize the development of stresses within each sample. Post-fracture fractographic analysis is performed to identify the origins of fracture, and to estimate failure stresses based of the fracture mirror radius using Orr's formula. The photo-elastic patterns closely match the FEA prediction, confirming that the largest tensile stresses occur within the intended central test strip. Polarized light reveals a sensitivity to eccentric loading for the two newly proposed designs, which can be minimized by introducing a neoprene interlayer between the sample and testing machine. All samples failed at multiple points; stress estimations based on fracture mirror size indicate that the lowest failure stresses consistently occurred within the test strip, further confirming that failure initiated within this area. It is concluded that the Theta-sample has potential as a uni-axial tensile testing method for brittle materials such as glass, though further research is required to fully confirm its reliability. ... Read more

The built environment is increasingly exposed to more frequent and intense climate-related extreme events. Although numerous frameworks exist to assess the impacts of extreme events - usually measured in terms of deaths, dollars and downtime - several authors have shown that indirect losses, often driven by the recovery phase rather than the response one, can represent most of community losses. Delays in initiating repairs significantly increase indirect losses but are often overlooked in frameworks focused only on immediate response. While recent resilience-based approaches aim to include both response and recovery, their indices often lack clear links to measurable physical outcomes. The definition of a clear, relatable, scalar index could better inform stakeholders and decision-makers about potential risks and guide them in planning mitigation strategies. This paper proposes a novel framework for quantifying socio-economic (direct and indirect) losses by considering both the response and recovery phases of extreme events. Building on resilience principles and functionality-time curves, this framework offers a comprehensive yet practical method for quantifying indirect losses. The approach is validated through a multistory building subject to earthquake and flood hazards, by employing a component-based probabilistic loss modelling approach. The framework was able to provide an estimation of indirect losses due to business interruption showing how indirect losses can match or even exceed the direct economic losses due to damage repairs. ... Read more

Glass is highly sensitive to damage accumulation during its service life, leading to a significant reduction in strength. Annealed glass used in glazing units of low-rise buildings can experience a 71–85% strength reduction after 20–30 years of natural weathering, which can be detrimental in structural applications. Despite these considerable reductions in strength, there are currently no well-established methods for repairing glass components, with hypothetical repair methods primarily limited to resin injection and little evidence on their durability or their efficiency in preventing water diffusion and subcritical crack growth. As glass panels increase in size, complexity and cost, the standard approach of replacing damaged components with new glass becomes unsustainable. This paper develops effective and durable thermal healing methods for damaged glass components. A systematic experimental investigation is undertaken involving controlled artificial aging of annealed glass, followed by thermal healing, microscopy and destructive flexural tests to assess the effectiveness of the repairs. Different thermal and hydrothermal profiles are explored showing that thermal treatment has potential for strength recovery. In fact, thermal healing for the flaws in this study, at high temperatures in the order of 300–500 °C, can fully restore and even increase the design strength of glass beyond new as-received strength. This suggests that thermal healing can support and promote repair and reuse of end-of-life glass, enhancing circularity in the architectural glass industry. ... Read more

Smart dynamic building technologies can help to significantly reduce operational energy and carbon emissions. However, human acceptance remains a significant barrier, particularly for switchable glazing used in smart windows. This study examines how users are affected by the speed and direction of transitions in the transparency of fast switchable glazing, specifically dynamic liquid crystal technology under overcast sky. Perceptual and behavioural data including facial action units, were collected through an experimental campaign in a semi-controlled environment where the glazing transparency was transitioned at two rates (1 and 10 s). It was found that user perception remained consistent regardless of transition speed or direction, but override behaviour was influenced by both factors. In the absence of glare, user overrides were primarily driven by the transition direction, with more users reacting to transitions from dark to clear. Faster transition rates led to an increase in user overrides for both transition directions. Unlike those who did not override, users who overrode the automated glazing control strategy had a negative perception of the visual environment and the window control system. Users directed their gaze more towards the glazing when this was transitioning, suggesting possible distractions. Users were clustered based on their background knowledge and reported preferences. These clusters showed a good correlation with the override delay times. However, the agreement with actual behaviour was low, indicating that a larger number of variables and clusters should be tested to predict user behaviour. Nevertheless, clustering users highlighted the importance of considering individual differences for interaction strategies. ... Read more

Composite glass sandwich panels, consisting of glass face sheets bonded to linear stiffeners (spines) in the core region, can provide significant benefits in material efficiency, reduced thickness, and greater overall transparency. However, current analytical models of their mechanical performance fail to account for the non-uniform longitudinal stress distribution caused by shear-lag effects in wide structural panels. This study redresses this by means of experimental research on composite glazing panels with different loading and geometrical configurations. Six 4-point bending experiments were performed on 34 mm thick, 1000 mm long, and 700 mm wide composite glazing panels, made from soda-lime silica glass face sheets bonded to glass fibre-reinforced polymer core spines. Two types of adhesives were tested: a relatively low stiffness silicone-based adhesive, and a relatively high stiffness epoxy-based adhesive. The shear-lag effects are quantified in terms of effective width ratios (EWR). The study showed that the epoxy-bonded panels provided a significant degree of composite action (DCA = 0.85) whereas the composite action in the silicone-bonded panels was negligible. Furthermore, it was found that applying the EWR values from this study in a recently published analytical model yields predictions of maximum strains at mid-span that deviate by no more than 16 % from the experimental results. ... Read more

Current multi-hazard risk approaches in seismic engineering primarily focus on structural performance under hazards such as earthquakes, floods, and wind. Despite the distinct risk due to their direct impact on human health, heatwaves receive limited consideration. This unbalanced and fragmented approach is particularly noticeable in facade retrofit design, which has a significant influence on both structural vulnerability during earthquakes and indoor thermal conditions during heatwaves. In this case, integrating seismic and heat risk considerations would help balance performance trade-offs across both domains and assist designers in the selection and combination of technologies that are effective under seismic and heatwave conditions. This study therefore proposes a simulation-based multi-objective methodology for facade retrofit decision making. The suggested approach is demonstrated through a case study: a reinforced concrete building retrofitted using a timber rocking-dissipative external exoskeleton and precast concrete sandwich facade panels. Key facade design parameters-component capacity and dimensioning-were varied to generate a multivariate response for both seismic and thermal performance. The simulation results revealed two challenges for optimization: a limited sample size and nonlinear relationships between design inputs and performance outcomes. To address both, a multivariate regression was applied within segmented performance ranges, defined by breakpoints where the relationship between parameters and performance shifted. The resulting segmented multivariate model enabled the identification of optimal technology combinations within specific performance ranges and the generation of multiple Pareto fronts. This broadened the viable solution space and better supported project-specific trade-off decisions. ... Read more

The growing demand for sustainable building materials is stimulating considerable research on bio-composites intended for the construction sector. Despite the technical challenges associated with their durability and fire resistance, bio-composites can provide environmentally friendly, load bearing components with useful mechanical properties. This paper provides an overview of the current research activities at TU Delft Department of Architectural Engineering and Technology in exploring five plant fibre reinforced polymer (PFRP) composites for various load-bearing applications. In addition to mechanical performance and durability, each bio-composite achieved one or more characteristic that improves the environmental sustainability of the bio-composite, namely: 100% bio-based; fabricated with simple low-tech equipment; sourced from bio-genic waste streams; assembled into a functional meta composite; formable into complex 3D shapes; and reformable at end of life. The findings presented in this paper provide useful insights of the material selection and manufacturing methods for each of the PFRPs and corresponding data from the performance testing. Moreover, the paper provides overarching observations across the five bio-composites and key recommendations for the future development of environmentally sustainable PFRP load-bearing components. ... Read more

The increasing frequency and intensity of heatwaves raises questions about the thermal vulnerability of buildings and, in particular, on how to assess their resilience to extreme heat. In this context, thermal fragility curves, which describe the probability of achieving or exceeding specific temperature thresholds for a building, serve as an effective measure to define the thermal vulnerability of existing buildings and identify tailored retrofit strategies. This study focuses on deriving thermal fragility curves for a case study: a 6-storey residential building constructed in the 1980s with a reinforced concrete structure and masonry infill walls. Dynamic thermal modeling and simulation were conducted over a one-year period using synthetic weather files generated to account for future heatwaves. The simulation results provide useful relationships in particular between: outdoor temperature and indoor Standard Effective Temperature (SET); and between outdoor daily maximum temperature and indoor SET. These relationships were finally analyzed to create and compare fragility curves using maximum likelihood fitting and the so-called Cloud methodology. ... Read more

Switchable glazing has made great strides to increase its potential of being deployed in adaptive building facades. These can provide shading solutions in climates with high solar insolation without compromising outlook and views, while allowing for privacy on demand. This paper further builds on previous knowledge and investigates the potential of a novel switchable assembly, comprising a dual dynamic solar-PDLC (Polymer Dispersed Liquid Crystal) and SPD (Suspended Particle Device) films, deployed in a side-lit, scale model setup for field testing. Using a comparative approach with static glazing, luminance photometry is used to determine the Daylight Glare Probability (DGP) provided by the different states of the switchable glazing. The measurements obtained assess the ability of this novel assembly of switchable films, to provide for privacy and glare control through the conversion of windows into opaque elements. ... Read more

Direct reuse and recycling of materials can significantly reduce the net environmental impact of the global construction sector. The feasibility of reuse and recyclability of building systems is affected by the materials used and the interfaces between constituent components. Yet there is a lack of quantitative methods for assessing the environmental benefits of alternative recovery strategies for multi-component and multi-material systems over the building lifetime. In this work, a novel assessment method was developed to enable a systematic and quantitative evaluation of the transient environmental reclamation potential (RP). The reclamation potential is a measure of the ability to disassemble and reuse recovered building systems at their end-of-life and is influenced by the constituent components and the interfaces between components. The proposed method accounts for the technical service lifetimes of components, including performance degradation over time, and can thus inform decisions on the most suitable recovery route for new and existing designs. The graphical outputs from the RP assessment are a network diagram which highlights the system components and connections between components, and an RP-graph which illustrates the embodied environmental impact and reclamation potential over time of alternative reuse/recycling strategies. The methodology is demonstrated on a glazed double-skin façade where the influence of component service lifetimes and replacements over time is quantified in terms of embodied energy and embodied carbon. The outcomes of the assessment can guide decision-making in design for disassembly (DfD) strategies and/or aid in the identification of high-value material recovery strategies at the end-of-life stage. ... Read more