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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The control of glare in office environments is often retrospectively improvised using shading devices, typically internal blinds. Despite the leap towards energy efficiency goals, visual comfort is still being compromised in climates with high solar insolation resulting in intolerable glare. This paper discusses the visual performance of a novel glazing assembly comprising of two, independently switchable (solar Polymer Dispersed Liquid Crystal and Suspended Particle Device) interlayers intended to control the visible light transmittance into an indoor space. Readings of DGP in a full-scale test cell are presented together with an analysis of the visual appearance of the glass.

In recent years, devastating earthquakes and climate-induced events have raised societal awareness of the urgent need to enhance resilience against extreme hazards. This becomes crucial when dealing with existing buildings. Many of these structures were built before the enforcement of modern seismic codes and energy regulations. Consequently, existing buildings are exhibiting a lack of resilience not only during earthquakes but also in case of extreme climatic conditions. Moreover, the energy inefficiency of the building stock should not be viewed solely as a problem related to its thermal vulnerability. It also requires an unprecedented effort to meet the goals outlined in the European Green Deal, specifically targeting energy savings and decarbonization by 2030 and 2050, respectively, to increase environmental sustainability. This work explores the feasibility of employing external low-damage exoskeletons consisting of rocking-dissipative structural connections for seismic strengthening. The implementation of exoskeletons is nowadays crucial, given the possibility of carrying out the intervention from the outside with limited disruption for occupants. Moreover, the exoskeleton serves as a support for a “double-skin” facade system offering opportunities to enhance the envelope energy performance, thereby enabling an integrated (i.e., seismic and energetic) rehabilitation. This paper discusses the advantages of using external exoskeletons compared to more traditional strategies (e.g., seismic local interventions combined with thermal coatings) by a case study application. The overall performance of as-built and retrofitted configurations is assessed through seismic and energy dynamic analyses as well as integrated loss modeling for resilience evaluations. The findings provide evidence of the efficiency of the proposed strategy and its potential.

Recent technological developments make perovskite solar cells (PSCs) particularly suitable for building integrated photovoltaic (BIPV) applications on vertical building envelopes, but the relatively short lifespan of PSCs requires frequent replacement, thereby generating substantial waste. Careful consideration of circularity credentials of this novel technology is therefore essential prior to the extensive implementation of vertical PSCs in building envelopes. This paper provides a circular economy approach for the implementation of PSCs in vertical envelopes and assesses its economic feasibility by life cycle cost analysis in Europe. The process of recycling PSC is developed. The economic performance of PSC envelopes is provided and compared to that of the conventional rigid BIPV system. Uncertainty analysis and sensitivity analysis of economic indicators are then performed to identify the influential parameters. The findings indicate that the PSC envelope has a significant potential for circular BIPV components and that PSCs applied on vertical envelope are economically viable.

Visual defects, in particular haze, in glass and façade technologies can significantly impact the aesthetic quality and human experience of daylight and views in buildings. The glass and façade industry increasingly requires methods that can objectively predict and measure the subjective user experience of haze. This is required to appropriately inform the manufacturing process, ensuring optimal functionality and performance, and avoiding material waste and economic losses due to the replacement of defective glazing. Existing methods for measuring haze are not appropriate for assessing large samples, either at manufacturing sites or in-situ. However, haze defects are often only exhibited and visible when glazing is produced in large samples or installed under real luminous conditions. This paper introduces a novel luminance-based method that measures haze by evaluating the halo around a light source that is observed through the glazing. This method is initially tested in a controlled laboratory setting on small glazing samples with varying level of haze. The halo serves as a proxy for haze severity and it is quantified by using luminance-based measurements. In this work, the newly-proposed method is verified by comparing the ranking in haze severity of different samples as performed by means of a standard haze meter and the newly proposed method. Additionally, the paper examines the dependence of this ranking on factors such as camera setup distance and light intensity. It was found that the proposed method was able to effectively ranks samples differing in haze intensity by more than 0.1 orders of magnitude. Positioning the camera closer to the glazing and using higher light intensity yielded more accurate results. However, for haze levels below 1% and differences smaller than 0.1 orders of magnitude, the accuracy is insufficient. To define the expected level of accuracy of methods for haze characterisation in-situ, the sensitivity of the human eye to haze under varying luminous environments and view content needs to be quantified.

Creating safer and more resilient building facades has become a primary concern in contemporary design, particularly in earthquake-prone regions, where there is a potentially high impact on financial, social and environmental losses. Glazed curtain wall systems are widely used in modern architecture. Yet, despite decades of research efforts aimed at enhancing the understanding of their seismic behaviour, it is not clear how design choices affect the response of glazed facades. This is crucial given the wide range of glass, framing and joint variations that are at our disposal. With a focus on unitized curtain walls, this paper provides insights into the influence of design variables on façade seismic response by means of an extensive experimental campaign and an associated parametric study to test alternative designs under both quasi-static and dynamic loading conditions. The variables considered included variations in unit dimensions, glass and joint aspect ratios, joint and framing detailing, and support conditions. This research delves into a statistical analysis of the experimental results, in order to define parameters such as glass and façade unit rotations, frame elongations and distortions, utilization factors at different intensity levels. The results provide insights that guide façade design decisions for achieving desired seismic performance levels.