Publisher
Challenging Glass Conference 6 was held 17 & 18 May 2018 at TU Delft in The Netherlands.
The conference was organised by Dr. Christian Louter (TU Delft), Dr. Freek Bos (TU Eindhoven) and Prof. Jan Belis (Ghent University).
The conference proceedings have been published by TU Delft Open.
ISBN 978-94-6366-044-0
Published:
2018-06-01
Front matter
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CONFERENCE ORGANISERS
Dr Christian Louter Delft University of Technology, Delft, The Netherlands
Dr Freek Bos Eindhoven University of Technology, Eindhoven, The Netherlands
Prof. Jan Belis Ghent University, Ghent, BelgiumSCIENTIFIC COMMITTEE
Scientific Committee Chairs
Prof. Jan Belis Ghent University, Belgium
Dr Freek Bos Eindhoven University of Technology, The Netherlands
Dr Christian Louter Delft University of Technology, The NetherlandsScientific Committee Members
Prof. Paulo Cruz University of Minho,... -
Ulrich Hamann - Foster and Partners - London - UK
Michael Ludvik - M. Ludvik Engineering - New York - USA
Christian Grünler - Daimler AG - Sindelfingen - Germany
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Platinum Sponsor: Saint-Gobain
Gold Sponsors: Dow - Eastman - Eckersley O'Callaghan - Seen - Sedak - Trosifol - Tuchschmid
Silver Sponsors: Dip Tech - Octatube - Sika
Keynote Contributions
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Even with today’s technically advanced navigation systems, user experience situations where announcements are difficult to understand and misleading. Augmented reality – the integration of computer generated content into the vehicle surrounding – can provide an intuitive and unambiguous way to communicate navigation information; it can even serve as a novel user interface that allows interaction with the surrounding. In this paper, challenges, constraints, and possible solutions for AR in-vehicle applications are discussed. Details of the technical and design decisions of the “first...
Architectural Design, Geometries & Lighting
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This research investigates the potential of glass as a new design tool to highlight and safeguard our historic structures. Current restoration and conservation treatments with traditional materials bear the risk of conjecture between the original and new elements, whereas the high consolidation demands often result in visually invasive and irreversible solutions. Nowadays, aspects of materiality and aesthetics appear as integral parts of the restoration practices, indicating new materials and technologies in the form of...
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The economy globalizes. The industries concentrate. The productions become uniform. Cultural specificities disappear.
About architecture and glass in architecture, it is the same phenomenon. Is this movement good or not? It is too late to ask the question. This dynamic is irreversible. Nevertheless, in certain cases, on certain projects, it is possible to bring more esthetic, sensibility, humanity and culture. The 100 years of Ferro’s experience in material science provide such base for creativity with outstanding material solutions like s1de... -
Serrated building envelopes are a very eye-catching element of contemporary architecture. This type of façade in plan resembles the edges of a serrated blade, hence the name. Serrated facades substantially influence the building’s tectonics understood as the relationship between the structural and the artistic form. They also have a major impact both on building physics (increased surface of heat exchange compared to flat facades, solar avoidance – decreased solar gains if properly designed) and on visual appeal. This article examines façade morphology and analyzes the influence of its...
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Defined by the building law in each publicly accessible building (e.g. schools, administration etc.) emergency exit routes have to be marked usually by means of active or passive lightening systems. The use of passive lightening systems require comprehensive components with an independent, battery-powered energy-supply that produces light even in the case of an energy black-out (e.g. disaster situations). The use of powerlines plus the frequently service of battery-powered systems is complicated and expansive. Alternatively after-glowing, phosphorescent signs, attached on walls,...
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The purpose of this paper, as part of a MSc graduation project, has been to explore to which extent the kinematic potential of folded geometries can benefit from the structural and architectural properties of glass plates. Using as a case study the covering in an adjustable way an outdoor swimming pool area, the course of this paper consists of form evolution based on structural performance and development of a dual purpose connection and deployment principle developed through experimental testing. Both aspects are examined independently, in...
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Cast glass components are a promising solution for engineering pure glass structures of high transparency and load-carrying capacity due to their large cross-sectional area and monolithic nature. Currently, the few realized structures employing cast glass components rely either on a steel substructure or on an adhesive of high bonding strength and typically less than 2 mm thickness, to ensure the stiffness and stability of the construction. Whereas the first solution compromises the overall level of transparency, the second results to a permanent construction requiring intensive and...
Curved & Bended Glass
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Significant progress has been made during the past two decades to advance the use of cold warped glazing (glass that has been elastically twisted out of plane) to achieve architectural vision. As with most new technologies, a full understanding of the mechanics of elastic cold warping has lagged its adoption and increasing specification for use in new construction. As a contractor whose aim is to turn vision into reality, Enclos has been invested in research and development related to the structural and performance implications of cold warped glazing. One of the most recent...
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Research has shown that the general approach to determine the bending strength of thermally curved glass with the aid of the four-point bending test for flat glass according to EN 1288-3 is applicable. At the moment, however, there is no statutory method available for directly extrapolating the breaking strain from the breaking load without the use of expensive strain gauges. Such a method is developed by means of an experimental and numerical study in a research project between the Bundesverband Flachglas e.V. (Federal Flat Glass Association) and the Fachverband Konstruktiver Glasbau...
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The owner of a 1970s, 24-story commercial office tower in Ottawa, Canada sought to rejuvenate their main lobby with a new glass entry wall. The wall’s purpose is to provide a notable, grand entryway for the re-development of a commercial podium on a main thoroughfare. The final design featured a 12 m tall by 35 m long curving glass fin wall. The height of the wall is broken up into two sections. The first is a 9 m tall section between the ground floor and a third-floor terrace that provides the main building with a new front entrance, including a double-height space....
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Use of cold-bent and warped glass units in unitized curtain walling is becoming a state-of-the art application. During the last years, such a global trend has challenged the design and engineering of glass units, frame elements as well as bonding joints in Structural Sealant Glazing (SSG) applications and has pushed for the investigation of material performance and calculation concepts, beyond available standards and guidelines. It is clear today that in SSG systems cold bending retention forces and differential displacements play a major role in...
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Chemically strengthened thin glass (t < 2 mm) is a material that is stronger and due to its small thickness, more flexible than conventional window glass. As such, thin glass offers the possibility for lightweight and flexible glass façades that could change shape depending on external conditions. This paper explores this concept and presents an MSc study on the use of this material in adaptive façade panels. The behavior of thin glass in this context depends on different factors. The glass thickness and strength define its bending limits, while the desired geometry and movement...
Glass in Facades
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Although in theory glass can be endlessly remelted without loss in quality, in practice only a small percentage gets recycled, mainly by the packaging industry. Most of the discarded glass fails to pass the high quality standards of the prevailing glass industry -due to coatings, adhesives, other contaminants or incompatibility of the recipe- and ends up in the landfill. However, employing discarded glass in cast components for building applications can be a way to reintroduce this waste to the supply chain. Such components can tolerate a higher percentage of...
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Facades are a crucial interface between exterior and interior conditions and greatly influence the architectural quality of buildings. Glass plays an important role in the building envelope by providing daylight, views and ventilation and hence can contribute significantly to indoor environmental quality and impact occupants’ comfort and well-being. Glass also plays an important role in the energy balance of the envelope and hence in both energy loads and environmental performance of a building. In order to avoid high energy consumption, reduce...
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Curtain wall design commonly uses insulating glass units for vision and spandrel glazing to provide better visual harmonization of building façade glass. Risks with this design approach include higher thermal stresses, especially when low-emissivity coatings are used on insulating glass units in spandrel areas. Ceramic enamel frit – commonly used to opacify spandrel glass – is known to induce a bending strength reduction of up to 50%. The ability of ceramic enamel frit coated glass to resist thermal stress is similarly reduced. Multiple incidences of thermal stress related fracture have...
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Façades play an important role in the control of energy flow and energy consumption in buildings as they represent the interface between the outdoor environment and the indoor occupied space. The option of regulating internal and external conditions acquires great relevance in new approaches to sustainable building solutions. Studies on climate adaptive façades show a very high potential for improved indoor environmental quality conditions and energy savings by moveable façades. A number of movable façades were realized in the past, but the use of...
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The use of ceramic fritted architectural glazing is becoming increasingly popular. “Fritted glass”, which is also known as “enamelled glass”, is defined as glass with a surface covering made of glass frit[1] that is applied by a printing method and fused to the glass substrate at elevated temperatures. The enamel coating may be continuous or consist of a discontinuous pattern such as spots or stripes. Functional thin-film coatings on glass have been used in standard glazing units for many years to improve thermal insulation or for solar...
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Glazing facades generally represent one of the most critical building components, from a structural point of view, since providing a physical separation and barrier for the building occupants. In this regard, especially under the action of
extreme loads, they require specific design concepts voted to protect the building occupants. In this paper, the feasibility and potential of special mechanical connectors interposed at the interface between a given multi-storey primary building
structure and the glazing facade are investigated via accurate finite-element models, under the action...
Hybrid & Composite Glass Components
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Glass, particularly in architectural design, expresses lightness and modernity. By rising glass surfaces of facades in buildings with high safety requirements, glass works as security glazing. Requirements of security glazing increase constantly. However, single glass panes do not fulfil the demands on these high technology products. Thereby, laminated glass or insulated glass are used to solve problems of the specifications in view of fire, heat, noise, sound and sun protection as well as safety, energy, design or media. The combination of different materials in a composite panel...
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The European RFCS project “S+G” has developed innovative steel-glass composite systems for high-performance building skins, meeting requirements of structural and energetic efficiency, as well as aesthetical value and versatility of applications. The aim of the project has been the design, prototype and testing of unitized cells composed by a glass panel and a contouring metallic frame, twisted by cold bending into a hyperbolic paraboloid shape, to be used in free-form curved building façades. To achieve large curvatures while maintaining the stress...
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This paper focuses on a recently developed concept, in which glass is combined with timber to provide post-breakage strength and ductility. This combination allows for good post-breakage performance and overall robustness of timber-glass composite beams and wall elements, which has been reported in several publications. The application of timber-glass elements in practice, however, raises important issues related to structural fire performance. The paper elaborates on this issue and provides general information about the behavior of glass, timber...
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This paper discusses alternative numerical approaches to the analysis of the structural behaviour of glass beams reinforced with GFRP laminates adhesively bonded, which were calibrated and validated from four-point bending tests available in the literature. For this purpose, smeared crack and damaged plasticity models were used to simulate the non-linear behaviour of glass, available in FEMIX and ABAQUS finite element softwares. The interaction between the materials in the composite beams, using polyurethane or epoxy adhesives, was defined thought...
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This paper describes the engineering steps taken in order to investigate the potential of glass sandwich elements, made of 2 glass skins separated by a glass core in the form of spacers, as a way to create planar elements with a high stiffness to weight ratio, reducing material consumption in structural glazing applications. The aim is to explore and evaluate the optical quality and the structural performance of those elements. In this research, 7 core topologies are explored in order to define which parameters influence the behaviour of a sandwich...
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An extensive parametric numerical study was performed after completed experimental campaign of timber-glass hybrid walls (TGW and TGWE). 36 timber-glass models (TG) with different outer dimensions were built and analysed using the commercial code SAP2000. Timber frame was modelled using linear beam elements with hinges in all four corners, an IGU was modelled as composite shell and finally a layer of adhesive was modelled with linear and nonlinear springs, which were distributed circumferentially around the edge of IGU and connected onto a timber frame. Normal and shear stiffness...
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Reinforcement and pre-compression of concrete beams results in a ductile response and allows for the design of structures that are more reliable and efficient. Therefore, this approach has been adapted to structural glass producing reinforced and post-tensioned glass beams. Unbonded tendons in Spannglass Beams are one structural example for realising this idea and are the subject of the presented study. Two individual laminated safety glass packages connected locally by metal dividers characterise these beams. A gap between the packages was used to guide tendons in a either...
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In contemporary architecture, glass is more and more applied not only to make up the cladding of the building, but also for structural members such as beams and façade fins. The trend to increase the scale of these structural entities makes it increasingly structurally efficient to apply statically indeterminate beam systems. For these systems to be approved, contemporary building codes require them to provide structural safety on an element and system level. Therefore, a lot of hybrid glass beam concepts, in which glass is combined with another material that provides post-fracture...
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The current rise of wooden constructions, which is encouraged by a strong trend towards sustainability of our buildings, also engenders innovation in facade design and materials. Timber-glass composite elements are a novel interpretation of the structural sealant glazing concept aiming at a reduction of the carbon footprint of facades by using materials from renewable resources. Already available facade systems based on the principle of timber-glass composite construction are applied in curtain walls, which is a rather conventional way. This paper assesses the feasibility of cold...
Insulating Glass Units
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Glass is an increasingly used material in construction and buildings. Despite its large application as load-bearing construction material, several aspects related to safe and optimal design are still under investigation and exploration, towards the full implementation of standardized rules of practical use. One of the main concerns in the design of this typically tensile brittle material is the rational estimation of static fatigue phenomena, under the effects of multiple design loads. In this paper, following earlier efforts, careful consideration is paid to the ultimate...
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Insulated glass units (IGUs) are employed in modern buildings as a substitute for monolithic glass to reduce heat loss through windows. In the past decades, the pursuit of higher aesthetic design drives glazed products evolving from conventionally flat into more creative and dynamic curved shapes. The call for curved IGUs brings up a series of challenges, and one remarkable issue is the determination of load sharing and glass stress when evaluating its structural performance. Even though many national codes worldwide have established mature design approaches for load sharing of...
Joints, Fixings & Adhesives
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The brittle material behaviour of glass means the inefficiency of contemporary mechanical connection technologies hampers the exploitation of full potential of glass for delivering energy efficient buildings. This paper presents the results of an experimental investigation of the use of adhesively bonded Glass Fibre Reinforced Polymer (GFRP) strips as a mean improving strength and ductility of bolted joints in glass. The peak load and the post-peak ductility of GFRP reinforced joints in annealed glass in double-lap tension joint configurations were experimentally investigated and...
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The German research team FABIG develops a bioenergy building skin including modules of glass which contain a liquid medium processing biomass. Inside the facade modules, load-bearing adhesives were applied that are subject to permanent water exposure. Water is known as a major hazard for adhesives because water molecules diffuse into the adhesive polymer matrix and into the interface between adhesive and substrate. As a result, material characteristics as well as the adhesion properties may change significantly. Additionally, the adhesive is exposed to conventional aging in building skin...
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Adhesive connections offer a number of benefits in structural applications, especially in the case of brittle adherends such as glass. There, a multitude of materials can be used to provide structural bonding between glass and/or metal components, giving evidence of different mechanical behaviours as well as structural performances. This paper reports on a Finite Element numerical investigation carried out on small-scale adhesive joint specimens. Taking advantage of a past experimental study performed at CTU in Prague - focused on both material tests and small-scale adhesive connections...
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Historically, silicone joint dimensioning is calculated with a simplified equation implemented in various standards for structural glazing. This equation assumes homogeneous stress distribution along the sealant bite whilst high local stress peaks, structure deformation or material ageing are included in a global safety factor. Safeguards such as a maximum authorized deflection (1%) and aspect ratio to respect (between 1 and 3) have been given to ensure the validity of the used equations. However new trends in commercial buildings such as the use of...
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In the design of blast resistant glazing systems, gluing the laminate glass to the window frame with a structural adhesive is an attractive option to maintain it attached to the frame while, because the large deflection of the broken laminate, it could potentially escape from a mechanical fixing. Actually, it does not exist a simple method that provides guidelines to the facade maker to design a joint that will resist to a blast. The complexity to develop such a method is due to 1) the blast load is time dependent and the phase shift between the...
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The demand for transparent but robust designs in architecture is still enormous. One of the most complex points of the application of glass is the use of efficient and appropriate connection details. The article examines a modular glass system about its architectural possibilities with a special focus on the connection methodology. We constructed a 2 x 2 x 1m prototype of specially laminated glass sheets with integrated connection details in the framework of a Master of Science programme on digital fabrication with support from Seele and Bischoff Glastechnik, which was also featured in...
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The connections between glass components are very critical aspects of structural glass design. Laminated steel-to-glass connections have recently been developed that combine high strength and transparency. This work focuses on the Transparent Structural Silicone Adhesive (TSSA), produced by Dow Corning. TSSA is typically used for the realization of circular point connections on the glass surface. An alternative approach of using TSSA is considered in this study, by laminating stainless steel connectors on the edge of the glass. These connections are...
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The current European standard for dimensioning silicone adhesive joints in structural glazing applications is defined in the ETAG 002. Although there are several decades of field experience with this standard it still has some major limitations and mainly uses an empirical concept based on an average force by area tension engineering approach. In addition there are a number of other restrictions for example the limitation of specific substrates and rectangular shaped joints with defined aspect ratios as well as the exclusion of joints with non-coplanar surfaces. The presented...
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Glass is an indispensable material in the building industry. The combination of transparency, strength and durability makes it to an unparalleled and desirable material. The technology additive manufacturing (AM) has a potential in the building industry, based on a relatively small amount of repetitions of particular building components and the tendency of applying technology innovations for buildings. Therefore, there is an interest for additive manufacturing with glass. This paper presents and summarizes the results of the preliminary research regarding additive manufacturing of glass...
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A trend towards adhesive connections instead of mechanical ones can be observed for transparent facades in recent years. Furthermore, research efforts are made to increase the efficiency regarding material use by designing systems with composite structural behavior. In this article, experimental and numerical results obtained for linear structural silicone joints between glass and stainless steel substrates, investigated separately under tensile and under shear loading, are discussed. The two selected adhesives, Dow Corning® 993 and...
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Cavitation in rubber-like materials describes sudden void growth of an initially voided material under hydrostatic tension until the material fails. To study the cavitation effect numerically, classical cavitation criteria are coupled with a continuum damage formulation of a Neo-Hookean material. A cavitation criterion defines a failure surface in threedimensional stress or strain space, which represents the onset of excessive void growth and therefore the strong degradation of the bulk modulus. To account for this special case of material softening, a novel continuum damage formulation...
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The main advantage of solid bricks over hollow blocks is substantially higher compressive strength. On the other hand, solid bricks have much higher thermal conductivity, which would lead to major heat loss when used for exterior walls. Masonry pillars and walls are usually loaded by compression and/or bending resulting from the eccentricity of vertical load or wind load. In case of solid glass bricks, compressive strength is about ten times higher than tension strength therefore the limiting factor of the glass masonry is tensile stress resulting from the bending. Whether compared to...
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Steel-to-glass laminated connections, which have recently been developed, limit stress intensifications on the glass and combine strength and transparency. Transparent Structural Silicone Adhesive (TSSA) connections have been used in several projects worldwide; however, the hyperelastic and viscoelastic nature of the material has to date not been fully investigated. In this work, the first objective is to investigate the mechanical response of TSSA connections under static and cyclic loading by means of experimental tests. Firstly, the shear behaviour of TSSA circular connections is...
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This paper investigates the use of bolted and brittle/ductile adhesive connections in glass structures. Two benchmark designs of shear connections are introduced and tested experimentally in quasi-static tensile tests. The designs consist of
tempered glass and aluminium substrates while steel splices are used for the load application. In addition, material characterisation testing for the glass and the adhesive is performed and the outputs are used for the numerical simulation of the same joints. Pressure-sensitive, plasticity and failure models are introduced and calibrated to... -
Structural sealant glazing systems (SSGS), currently also known as bonded glass, for façades originated over 50 years ago. Although a lot of new developments were introduced and essential experience was gained, the design of the continuous adhesive glass-metal connections used in conventional SSGS did not undergo significant changes ever since. To optimise the design of such connections and to enable the development of new and innovative concepts of adhesive connections in building construction, fundamental research on the structural performance of adhesive glass-metal connections is,...
Laminated Glass & Interlayer Properties
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Laminated glass, composed by glass plies sandwiching polymeric interlayers, can provide a safe post-glass breakage response, in compliance with the fail-safe approach used in the structural design. In fact, when glass breaks, shards remain attached to the polymer, preventing danger from falling materials and imparting a "tension stiffening" effect to the interlayer, so that the broken panel maintains a certain residual load-bearing capacity. Here, a homogenized approach is presented to describe the mechanical properties of broken heat-treated laminated glass under tensile...
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Laminated safety glass has become an indispensable component in building construction, automotive and solar industry. It consists of at least two glass panes, that are laminated together with a polymeric interlayer. Mechanically speaking, the polymeric interlayer enables a shear transfer between the two glass panes. Here, the difficulty lies in the understanding of the real shear transmission. On the one hand, polymeric interlayers show a time dependent material behaviour, which can be described with a ‘Prony-series’ in the linear viscoelastic area. On the other hand, polymeric...
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Polymeric interlayers used in laminated glass show viscoelastic material behaviour. Therefore, the precise design of laminated glass structures is dependent on temperature and the load duration. For the determination of the abovementioned material behaviour of the interlayers different small and big scale test setups exist. One of these tests is the torsional test in which the shear modulus of the interlayer can be calculated from measured data during a relaxation test. In this test, a laminated glass plate is conditioned at a certain temperature of interest and then isothermally twisted...
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This abstract relates to the recent publication [Viverge K., Boutin C., Sallet F. : Model of highly contrasted plates versus experiments on laminated glass, IJSS, 102-103, 238-258 (2016)]. This contribution provides a synthetic analytic formulation describing the behaviour of laminated glass under static and dynamic loadings, that is validated by experiments. We only give here a synoptic overview and for in depth reading one may refer to the above mentioned publication.
As the laminated glass is made of stiff glass layers pasted with soft viscoelastic interlayers a...
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The subject area "structural strength of materials" is defined generally as а complex of strength characteristics of materials and structural elements, obtained under special mechanical tests. It is shown that these tests should take into account not only the physical and mechanical properties of the material, but technology, blank processing, sphere of application, the influence of shape and sizes of elements as well as of their specific loading and operating conditions. Methods for evaluating the structural strength of glass as a linearly elastic material with high sensitivity to...
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In the long run laminated glass interlayers are sensitive to weather conditions. Several studies have been carried out that aim at understanding the consequences of moisture and solar radiation on adhesion to glass and on the mechanical response of the composite pane. In particular, solar radiation seems to produce the strongest effects on the bulk properties of PVB, modifying the coupling capability of laminated glass plates exposed to the direct sunlight. Such problem has been already studied by the authors via dynamic tests on small laminated...
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Laminated glass provides safety in an impact or explosion event by way of a polymer interlayer to which glass fragments adhere upon fracture. The mechanical deformation of the interlayer defines how the impact energy can be absorbed to prevent calamities by flying glass debris, penetration of a blast wave, lacerations, etc. The PVB interlayer used in safety glass shows highly nonlinear viscoelastic material behaviour, with a great sensitivity to temperature and deformation rate. Although various material models for PVB can be found in literature, few publications discuss the full range...
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Slender glass panels are widely used as storefronts and indoor separating walls in shopping malls and public buildings. To ensure that the design and construction is technically safe for general use and that it meets current and accepted technical standards, in-situ testing is required by the building administrator or authorities. A case study was performed of an indoor glass lantern in a public building made from slender two-side supported glass panels with a complex geometry. It provides structural assessments and results of in-situ experiments...
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Engineers and designers are using glass in increasingly demanding applications such as stairs, floors, and bridges, large minimally supported facades and overhead glazing. The use of laminated glass in structural applications has become more recognized and preferred as safer choice to monolithic tempered or heat strengthen glass. Structural interlayers are stiff interlayers that increase the strength of the laminated glass enabling the glass structure to handle higher loads with thinner glass. The use of structural interlayers enables laminated glass use in the most demanding...
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Modern façade glass elements need to meet high standards of solar performance, as well as thermal insulation, while maintaining transparency requirements. These requirements are key to provide comfort for the building users and minimize energy requirements for heating and/or cooling. In today’s urban environment, likely additional requirements for reflectivity, glare and acoustic performance are in place. Advanced glass coatings have come a long way in meeting many of the requirements, and have developed to the extent that further development provides diminishing returns, either in their...
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Laboratory testing data concerning the full sized laminated glass panel with different glass make-ups under impact is limited. An experimental investigation on the impact resistance of LG panels under hard body impact is reported in this paper. A test approach namely, mean minimum breakage velocity approach, is adopted to capture the minimum impact energy that triggers each glass breakage. The crack morphology of glass panels is firstly investigated. Results indicate that the intersection angle of the radial crack edges increases when the...
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Looking at a current architecture, there are many examples of glass load bearing structures such as beams, panes, balustrades, columns or even stairs. These elements are mostly made of laminated glass panels. Panels are bonded together with polymer interlayer significantly influencing a shear forces transfer between them. There is still overall lack of knowledge in the task of shear forces transfer between these panels. It principally depends on the polymer stiffness, which is affected by an ambient temperature, humidity and load duration. Civil engineers currently tend to design...
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Laminated glass fulfills the demands on safety and security in transparent structural elements used in architecture and other fields of engineering. It can be constructed as forced-entry, bullet, or blast resistant. The basic three-layer configuration consists of two glass panes connected with a polymer or ionomer interlayer; the advanced products contain also other layers. The foil ensures shear coupling and provides post-breakage resistance and damping. For the design of laminated glass structures and their analysis, knowledge of mechanical properties of interlayers is essential. In...
Numerical Modeling & Experimental Validation
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This study aims to investigate and assess the analytical calculation methods which are applicable to glass parapets. Specifically it is focused on glass parapets, which are continuously clamped along their lower edge in an aluminium profile, without the addition of a (structural) handrail. The starting point of the research are the current codes of practice regarding glass parapets. The objectives are to investigate the limitations of the current methods, to develop new methods and to test whether these are applicable, taking into account the standards of several European countries....
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In the last decade there has been an increased usage of cast glass as structural element. Within this respect, a 14 m span glass masonry arch bridge is planned to be constructed at the TU Delft Campus. This paper focuses on part of the experimental analysis that was executed to develop the concept of this bridge. Since it is an arch, the applied loads will be transferred as compressive forces, hence the suitability of glass. Adhesive bonding is not required, since the arch is
in compression under its own weight. Application of cast glass bricks in a bridge is a new concept, therefore... -
The paper is focussed on partition walls assembled from hollow glass blocks. These blocks gained popularity recently because of new development: new decors, wide range of colours, variable surface finishing and wide range of accessories make it attractive for architects. In addition, improvements in acoustic and thermal properties, improved fire resistance and further innovations lead to new applications. The traditional method of assembling is based on using of cement mortar and steel reinforcement leading in kind of reinforcement concrete...
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The growth of the industrial production generates a high volume of waste materials. These products have a significant impact on the environment. Therefore, the valorization of industrial wastes, especially those produced in huge quantities, is an important social and ecological issue. Waste reuse and recycling could help to develop new products and aggregate value to materials that would have been previously discarded. Furthermore, it could reduce the consumption of natural resources and pollution. Blast furnace slag and fly ash are waste materials largely used in concrete production,...
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Wind induced pressure is a major design consideration for glazing design. However, the effects of façade geometry and urban terrain on wind loading are often difficult to quantify without costly and time-consuming wind tunnel testing. Accurate 3-dimensional data, covering most major cities, is becoming increasingly accessible, and such models are ideal to support numerical modelling of environmental effects on the built environment, especially if such modelling attempts to capture the geometric effects of the cityscape. A new methodology to assess the effects of wind loads on...
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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...
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Modern building envelopes are typically high-technological systems that need to meet strict requirements regarding architectural intent, structural capacity, energy-efficiency and durability. The study presented in this paper is based on recent research performed at the Glass & Façade Technology Research Group (University of Cambridge) that investigates high-performance engineered unitised systems as an alternative to traditional curtain-walls for building facades. The proposed unitised systems has a sandwich design made of two outer glass face sheets separated by, and bonded to,...
Projects & Case studies
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Sarah Oppenheimer is an artist whose work with glass challenges our perception of space. David Bott (PE, SE, AIA) of Heintges Consulting Architects & Engineers assisted Oppenheimer in developing structural solutions that do not always conform to traditional architectural parameters, often when there are no precedents in building codes. Bott highlights the apparent lack of clear glass engineering guidance in both the International Building Code and the ASTM E1300 standard. He goes on to explore the importance of utilizing information hidden deep within E1300 or contained in other...
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La Maison des Fondateurs in Le Brassus Switzerland is going to represent the watch making manufacture Audemars Piguet. Audemars Piguet stands for the finest quality, precision as well as innovation based on traditional watchmaking expertise and craftsmanship. La Maison des Fondateurs has been developed from a competition proposal to the execution project by the architects BIG – Bjarke Ingels Group. The created interlocking all glass spiral evolves the building volume out of the rough, natural landscape providing a perfect linear museum path for the building program. Despite the severe...
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The iconic Torre Europa building in Madrid is currently under refurbishment. The envisaged works include the construction of a new entrance hall composed of two structural glass façades and a steel canopy above them. This paper focuses on the design and construction of the two structural glass façades, which are connected together at an angle of 100∘. These are made up of a number of laminated glass panels standing on the ground floor slab and stabilised by vertical glass fins. The connection between the cladding panels and the fins is resolved with embedded metal connectors. The top end...
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Revolving entrance doors - usually built as some kind of all glass structure - are part of many publicly accessible buildings. As the architectural demands rise regarding transparency and slenderness of façade members, the entrance doors have to and do go along with these demands. But even if the façade is designed carefully and verified according all relevant standards, the revolving doors are usually considered as a machine, coming with some certificate. This point of view is mostly shared by the manufacturer and the basis for the call for proposals. The certificates provided by the...
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The state owned building of the Land Registry in Ravensburg, South Germany, got a new glass façade in front of the staircase. The artistic design, which is inspired by a crumpled piece of paper, is realized by laser treatment and digital printing with ceramic enamels. It is integrated in nine panels of insulating glass.
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This paper will describe the design, detailing, testing and construction of the structural glass beams which make up the load bearing grid shell structure of the newly built Zaryadye Park in Moscow, Russia. The canopy structure is situated short distance from Red Square and the Kremlin. Structural glass beams, 72 in total, are connected into the main undulating steel grid shell structure which measures approximately 120m long and 60m wide. The beams themselves vary in length according to the geometry but are generally 3m long, 0.2m deep. The beams meet each other and the main steel...
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An all-glass balustrade’s continuous handrail enables a horizontal load transfer from more flexible glass panes into adjacent elements with higher stiffness and thereafter – as the case may be – into even more rigid parts of the structure. As all the glass units are interconnected thus supporting each other mutually, a safe and economic design either requires taking a holistic view of the entire structural system or to make appropriate assumptions for the boundary conditions of the handrail in order to assess precisely the stress state of a single...
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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...
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The plan of the glass group of the TU Delft to realize a 14m span dry-stacked glass arched masonry bridge led to investigation of stability of glass arches in more general. Analytical and numerical analysis are done to compare results. Analytical analyses are based on methods developed for traditional stone arches. A graph is plotted in which the relationship between rise-to-span ratio and thickness-to-span ratio is derived and presented such that the relevant instability mechanism(s) can be determined. The required thickness of a stable arch can be...
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The paper illustrates the design project of the main laminated glass balustrade of a steel staircase installed in the historical Margherita Theatre in Livorno, Italy. After its final closure, almost 15 years ago, the new owners decided to refurbish the building and to convert it into a shopping center. The entire project was developed with particular attention to the conservation of the building style. In order to join the ground level to the former gallery level a new steel staircase has been placed and three laminated glass balustrades were added. The bigger one is a big rectangular...
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Laminated safety glass with structural PVB interlayer is suitable for a variety of challenging applications in building construction and façade design. Especially in areas with increased static requirements, stiffer interlayer materials are preferred to standard PVB films. This results in a reduction in the number of glass panes or pane thicknesses while maintaining comparable properties. The attainment of relevant safety properties in combination with advantages in both processing and economic terms often allows a more reasonable application than...
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Future smart cities are demanding for new infrastructures and networks. Novel multifunctional objects should be able to acquire, store and transmit information, generate their own energy need, light up the surroundings and more. Thanks to their transparency, glass structures are ideal support for hi-tech components because of the inherent opportunity offered by laminated glass to embed PV cells, sensors, OLEDs and lighting devices. The project HYbrid GLAss-Steel Stele (HYGLASS) aims at the realization of a cantilevering hybrid vertical structure working as a stand-alone or a...
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The aim of this paper is to explain how the design intent of a bespoke glazed façade develops from the point of view of the façade consultant BIFF SA. The explanation of this concept development is not only interesting because of the different phases of the process, but also because of the unusual specifications and demands established by the architects and the Client, and for the project evolution trough several technical solutions up to final project state. During the concept development materials like stone, steel, aluminum or fabric are normally combined with glass. This challenging...
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Modern cities and their architectural structures undergo significant functional and physical changes. In recent years, the interventions on building envelopes have increased. Therefore, it is necessary to analyze potential remodeling of glass facades, along with applying the concept of smart technologies, in order to increase energy efficiency of the existing buildings. This paper analyzes the modernization process of devastated glass façade of the tall Slavija hotel, built in 1960s in Belgrade, Serbia, taking into consideration some positive...
Strength & Stability
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Glass, a brittle material, fractures under tensile stress acting over a time duration. Lateral loads, such as wind, acting on a simply supported rectangular glass lite, put one surface of the lite primarily into tension. ASTM E 1300 defines load resistance of glass as the uniform lateral loading acting over a duration of 3 seconds that is associated with a probability of breakage of 8 lites per 1000 at the first occurrence of the loading. To determine load resistance, the underlying window glass failure prediction model facilitates determination of a probability distribution of 3 second...
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Cold bent glass is nowadays of primary importance both for industrial and civil applications. In fact, thin glass with a maximum thickness of 1.5 mm is often part of a wide range of technological devices and architectural surfaces (e.g. touchscreens, displays, mirrors, optical instruments, claddings and building interiors). The manufacturing process of cold bent glass is generally considered faster and less demanding in terms of necessary equipment with respect to hot bending or casting techniques. On the contrary, both the design of the manufacturing procedure and of the products are...
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A numerical method is applied to model the fracture stress and failure location in glass panes subjected to various bending arrangements. The method assumes the weakest-link principle and the existence of surface microcracks. The fracture stress and failure origin are revealed through a search algorithm. The magnitude of strength and the location of fracture are stochastic in nature and can be predicted based on a suitable representation of the surface flaws condition. When the crack size distribution is assumed to be Pareto, the strength distribution is found to be very similar to a...
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The paper correlates the data recorded in Stazione Sperimentale del Vetro, in many years. The aim is to define a correlation between the following parameters in heat treated glass: 1) bending strength tested according EN 1288-3 ; 2) fragmentation tested according relevant Standards [EN 1863-1 2004, EN12150-1 2015, EN 14179-1 2016]; 3) surface compression stress measured with laser Gasp [ASTM C1279 2013]. For heat strengthened glass the fragmentation correlation due to the different crack path ("island" fragments instead of small fragments) is only related to conformity: Y/N. The research...
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Thin glass is currently widespread in mobile devices and has great potential for applications in buildings. However, presently there is no standard method to determine the strength of thin glass for building applications and there is little experimental data available on its mechanical behaviour. Hence, this paper presents experimental and numerical investigations developed with two main goals: (i) to assess and (eventually) adapt existing test setups in order to determine the strength of thin glass; and (ii) to characterize thin glass using those tests, focusing on the ultimate strength...
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The use of glass in windows and curtain walls, in residential as well as in high-rise buildings, is something that requires great care in design and execution. Apart from complying with typical structural engineering practices and ensuring, for example, that the glass thickness is sufficient to withstand wind loads, impact loads etc. it is necessary always also to consider the thermal-stress resistance of the glass employed as well as the temperature distribution across glass and façade components. This topic is not new as it began to be analysed with the emergence of the first body...
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In present-day practice, monitoring the installation process and the utilisation of glass and hybrid components, e.g. glass/steel or glass/plastic, has become increasingly important. To date, the quality control options for built-in glass is limited. It is not yet possible to provide a clear short-term statement regarding a potential irregular stress; this may arise due to the incorrect assembly of a glass fitting, for example. There are no accepted standard procedures to evaluate the in-situ stress condition of a built-in glass. The intention of this paper is to address this gap with...
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An analytical approach based on the on the sequential partitioning of the data and Weibull Statistical Distribution for inhomogeneous - defective materials is proposed. It allows assessing the guaranteed strength of glass structures for the low probability of fracture with a higher degree of reliability. Parameters of equations for the piecewise linear approximation for Weibull statistical distribution have been defined on the example of processing of bending tests results for float glass. The advisability of using this approach to structural elements of different size is proved. It was...
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The classical image of glass is that of a rigid, transparent brittle material characterized by a non-crystalline microstructure. This 19th and 20th century image however is mostly based on the contrast between soda lime glass and metals. It does not really make sense in the 21th century where more modern testing methods have increased our understanding of the physiochemistry of glass. Based on recent results and the development of computational molecular dynamic software modelling a new approach to the physiochemistry of glass is outlined. The...
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The results from a new numerical method for simulating the strength and fracture locations of small glass specimens subjected to double ring bending are compared with experimental data. The method implements the weakest-link
principle while assuming the existence of Griffith flaws. A Weibull distribution for the strength is simulated based on a single population of Pareto distributed crack sizes. The effect of using different fracture criteria is investigated. An alternative distribution is simulated based on two populations of flaws. This distribution models the apparent bimodality... -
Glass strength is very sensitive to damage accumulation during its service life. Repair methods for glass have been proposed over the last decades to volumetrically fill or remove existing flaws from the surface of glass. However, the lack of information on the strength recovery attributable to glass repair methods restrict their use to low consequence class applications in buildings thereby making replacement of damaged installed glass the only safe and practical solution when dealing with damaged glass. Repair methods involving volumetric filling of visible flaws with resins, removal...
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In structural design the bending strength of heat-treated glass is in general calculated as the simple sum of the characteristic values of the strength of annealed glass and of the thermally-induced prestress, considered as the 5% quantiles of the corresponding statistical distributions. However, the probability that two stochastic variables attain small values simultaneously is quite low; therefore, it is expected that the 5% quantile of the heat-treated glass strength is higher than the simple sum of the 5% quantiles of the two constituent distributions. Here, we theoretically confirm...
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Many glass applications require laminated glass to achieve a safe load-bearing behaviour. Beside the structural aspect, glass elements have to meet high aesthetic demands. Laminated glasses often feature an offset between the individual glass panes resulting from the lamination process. With regards to visible or exposed edges, this displacement reduces the aesthetic quality of the glass component. The regrinding of the edge after lamination equalises the offset and thus creates a smooth surface. However, regrinding tempered glass leads to a reduction of the surface compression zone at...
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This work presents the relation between the fragment density and the permanent residual stress in fragmented tempered glasses of various thicknesses. Therefore, fracture tests were carried out on tempered glass plates and the fragments in observation fields of 50 mm × 50 mm were counted. The average fragment density in the observation fields was set in correlation with the average measured residual stress of each specimen. Furthermore, the average particle weight of 130 particles per specimen chosen by random was determined. The relation between the average particle weight and the...
Structural Glass Design Philosophy & Structural Safety
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Due to the recent terrorist attacks, the market demand for security glazing has rapidly grown and turned from a “bank counters” market to a facade market. In this context, it appears to be legitimate to ask the question of the applicability of current standards to this changing environment: Are they still adapted to fulfil the security requirements of the market ? If not, which adaptations could be performed ? In the present talk, the current European standards dedicated to the security glazing resistance against explosion pressure - EN 13541 - is...
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In this paper authors will summarise current design approaches for hybrid glass structures. Our past and present projects will be used to demonstrate how such structures can be justified using finite element analysis, analytical solutions in context of prescriptive national and international regulations, industry guidance’s developed and accumulated over past decades. General methods will be distilled, relevant for future hybrid glass structures.
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Current design codes and standards provide limited indications for advanced analysis and earthquake engineering of structural glass applications in seismic regions. This work provides an energy-based approach for efficient design and structural performance evaluation of structural glass systems in seismic regions. The analytical formulation of the energy-based approach for dissipative non-linear structural glass systems is firstly presented. A practical application is then described by means of analytical and numerical studies. The results show that...
