Fragile yet Ductile: Structural Aspects of Reinforced Glass Beams

This dissertation investigates the structural aspects of reinforced glass beams. The concept of these beams, which are intended for building applications, is to provide redundancy even if the glass is broken. This redundancy is obtained through a small reinforcement section that is bonded at the tensile edge of the glass beam. Upon glass failure the reinforcement section bridges the crack and carries the tensile forces over the crack, thereby creating a post-breakage load-carrying mechanism. Various parameters that may influence the structural performance of the reinforced glass beams are experimentally investigated in this dissertation, namely: bond system, temperature, thermal cycling, humidity, load duration, reinforcement material, reinforcement percentage and beam size. This is done by means of pull-out tests, to investigate the pull-out strength of the reinforcement, and by means of bending tests, to investigate the structural response of the reinforced glass beams. Furthermore, analytical and numerical investigations are performed into the modelling of the structural response of reinforced glass beams. The analytical model has been developed in this research in analogy with reinforced concrete. The numerical model makes use of a novel sequentially linear analyses (SLA) scheme and saw-tooth reduction diagrams to simulate cracking of the glass and yielding of the reinforcement and to describe the overall structural response of the beams.Building TechnologyArchitectur

Dünnglaskonzepte für architektonische Anwendungen

Dieser Beitrag untersucht das Potenzial von Dünnglas für architektonische Anwendungen und berichtet über zwei Dünnglaskonzepte, die an der TU Delft in einer Reihe von Masterarbeiten unter der Leitung des Autors entwickelt wurden. Das erste Konzept thematisiert flexible und adaptive Dünnglasscheiben, die ihre Form als Reaktion auf externe Parameter verändern können. Das zweite Konzept untersucht dünne Glasverbundplatten, bei denen dünne Glasverkleidungen mit (3Dgedruckten) Kernelementen kombiniert werden, um starke, steife und dennoch leichte Glasfassadenplatten herzustellen. Von ersten Designstudien bis hin zur Entwicklung von Prototypen zeigt sich, dass beide Konzepte sehr vielversprechend und für weitere vertiefende Untersuchungen geeignet sind. Dieser Beitrag ist weitestgehend aus [1] übersetzt.Also published as Special Issue CE/papers, Volume 3, Issue 1, Special Issue: Glasbau 2019 Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Design & Mechanic

Thin Glass Composites with 3D Printed Polymer Cores

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 architecturallyappealing 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 characteristicsfor 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.Applied Mechanic

Thermo-mechanical Numerical Modelling of Structural Glass under Fire - Preliminary Considerations and Comparisons

In this paper, careful consideration is paid for structural glass elements under fire loading. In particular, a thermo-mechanical Finite Element (FE) numerical investigation is carried out in ABAQUS on small-scale structural glass elements exposed to fire. Taking advantage of past literature efforts, major thermal effects on the material properties are taken into account in the form of key input parameters for numerical simulations. Further validation of the so calibrated FE models is then carried out towards past small-scale experimental fire tests on monolithic glass panels. A sensitivity FE study is hence proposed, giving evidence of major influencing parameters on the thermo-mechanical performance of the same structural glass elements, including variations in the fire exposure, thermal-to-mechanical loading ratio, geometrical and mechanical features of the specimens.OLD Structural Desig

Thermo-mechanical numerical analyses in support of fire endurance assessment of ordinary soda-lime structural glass elements

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.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Mechanic

Structural glass beams with embedded GFRP, CFRP or steel reinforcement rods: Comparative experimental, analytical and numerical investigations

The use of hybrid and composite solutions for structural applications represents a common approach for the development of safe design principles. Consolidated examples exist for concrete, steel and masonry structures. As a general rule, materials are combined so as to obtain an enhanced redundancy, strength and/or (lateral) stiffness for these systems. In this paper, structural laminated glass (LG) beams including reinforcement rods are investigated, and special attention is spent on the effect of embedded rod features, consisting of GFRP, CFRP or stainless steel reinforcement tendons. The examined embedded solution, as shown, can offer a certain benefit to the bending performance of traditional LG beams, including positive effects on stiffness, resistance and redundancy. The intrinsic properties of rods can otherwise largely affect the overall observations. To this aim, unpublished experimental tests are first briefly summarised for a set of 1 m span LG beams. Support for the preliminary discussion of the examined design concept is also derived from simple analytical calculations. Finite-Element (FE) numerical simulations are then presented, reporting on major expected behaviours due to variations in the geometrical/mechanical features of the rods, with respect to the experiments. A key role in the FE models is given by the reliable description of mechanical properties and interactions between the structural components. Comparative results are hence discussed for the post-fracture assessment of beam specimens. As shown, even a limited presence of reinforcing rods (≈100-to-400 the explored range for the ratio of glass-to-rods cross-sectional area) can provide ductility and redundancy to the LG beams. Maximum benefits (+30% residual resistance) are given by ductile steel rods, while positive effects can also be achieved with GFRP and CFRP tendon rods.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Design & Mechanic

Finite-element analysis of post-tensioned SG-laminated glass beams with mechanically anchored tendons

Based on past experimental research results, this paper aims to investigate the structural performance of laminated glass beams with post-tensioned, mechanically anchored tendons, via extended finite-element (FE) simulations. The post-tensioned glass beam concept offers the advantage of providing a certain amount of initial compressive stresses in glass, hence resulting in a marked increase of the initial fracture load and in a rather appreciable redundancy, compared to typically brittle, unreinforced glass beams. Due to the presence of the post-tensioned tendons, a significant level of residual strength can also be guaranteed, thus resulting in a structurally efficient and safe design concept. In order to fully optimize the expected resistance and redundancy potentialities, however, careful consideration should be paid for a multitude of geometrical and mechanical aspects. In this research contribution, both full 3D and shell models are implemented for post-tensioned laminated glass beams. Based on validation of these FE models towards the past full-scale experimental results, the effects of several mechanical parameters are emphasized (e.g. steel tendon percentage, level of the applied pre-stressing force and the presence of possible geometrical imperfections) under room temperature and quasi-static loads. It is expected, based on the current study, that the examined design concept could be further developed and optimized.OLD Structural Desig

Building and Testing Lenticular Truss Bridge with Glass-Bundle Diagonals and Cast Glass Connections

On the campus of Delft University the Glass and Transparency Research Group is preparing to build a pedestrian bridge as a low arch consisting of dry-stacked glass blocks. As temporary support for the arch, a lens-shaped truss has been constructed and placed on location. This truss has been fitted with as many glass components as was structurally feasible. The diagonals in the truss are glass bundle struts and the nodes of the truss are cast glass components. The lenticular truss will serve as a temporary bridge during the time the team needs to prepare for construction of the eventual Glass Arch Bridge. Due to the experimental nature of the truss, with its unusual and novel applications of structural glass, a number of demonstrative proof loadings were performed to ease concerns about the safety of the structure. The glass bundles have been proof-loaded to twice their maximum expected load just prior to their installation in the structure. The whole system has then been proof-loaded for several critical load combinations (static and dynamic) just after installation. During the proof-loading the strains in the glass diagonals have been measured. These lie easily within the acceptable limits. In the paper the structural design of the bridge, in particular the glass node connector and the glass bundle diagonals will be explained. Then the proof-loading of the bridge will be described. Then the results of the proof-loading are presented and discussed.OLD Structural DesignApplied Mechanic

Preface to the special issue on Intelligent Construction and Automation

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.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Mechanic

The mechanical behaviour of SentryGlas® ionomer and TSSA silicon bulk materials at different temperatures and strain rates under uniaxial tensile stress state

An innovative type of connections for glass components, called laminated connections, has been developed in the last years. Two materials have been used for laminated connections: the transparent ionomer SentryGlas® (SG) from Kuraray (former Dupont) and the Transparent Structural Silicon Adhesive (TSSA) from Dow Corning. In this paper, the mechanical behaviour of SG and TSSA bulk materials is studied under uniaxial tensile stress condition. The effects of strain rate and temperature variations are investigated. Particular attention is paid (i) to the study of these polymers in cured condition and (ii) to the computation of true stress and strain field during the tests. Firstly, it is observed that the mechanical behaviour of both SG and TSSA are temperature and strain rate dependent. These effects are quantitatively determined in the paper. Secondly, two additional phenomena are observed. For TSSA, it is observed that the material goes from fully transparent to white colour, exhibiting the so-called whitening phenomenon. For SG, instead, it is observed that the strain field distribution is dependent on the temperature. More specifically, the material exhibits a non-uniform strain field distribution due to the occurring of the necking phenomenon. Measurements along the specimens, using Digital Image Correlation techniques, showed that the localized strain propagates over the full specimen length, resulting in a cold-drawing phenomenon. Finally, it is also shown that engineering and true stress–strain definition exhibits large deviation indicating that the finite deformation theory should be used for the computation of the stress–strain curves to be implemented in numerical modelling.OLD Structural Desig