Structure glass technology : systems and applications

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (leaves 70-73).Glass cannot compete with steel in terms of strength or durability, but it is the only structural material that offers the highly sought after qualities of translucency and transparency. The use of glass has evolved from purely decorative or architectural to structural, encouraging glass technologies to advance concurrently with increased demand. As a result, contemporary methods used to produce structural glass provide excellent strength characteristics, particularly after treatments including annealing, tempering, and heat-strengthening, which reduce its vulnerability to cracking and sudden brittle failure. Its modulus of elasticity is roughly equal to that of aluminum-greater than both wood and concrete-but doesn't allow any plastic deformation. Lamination dramatically improves both the strength and durability of glass by joining strengthened layers of glass using resin or a polyvinyl butyral foil. No comprehensive design code is currently available to aid in the design of structural glass members. The behavior of glass is examined through a variety of structural applications including beams, columns, walls, roofs and floors, and domes. Case studies are explored to underscore the technical principles discussed for each structural glass element utilized in place of more traditional building materials.by Katherine K. Leitch.M.Eng

Experimental study on the torsional mechanics of laminated structural glass beams

This thesis presents an experimental study on the torsional-mechanical behaviours of laminated structural glass beams. Glass structures are in increasing demand due to many favourable characteristics such as high compressive strength, flexibility, aesthetics, sustainability, and their positive effects on human mood and performance. However, monolithic glass is brittle in nature and fails instantaneously so laminated glass building elements are preferred, which have complex composite behaviours. An additional challenge is the lack of a finalised glass design code. This PhD study takes aim specifically at laminated glass beams and their torsional mechanics, which are crucial for supporting floor and roof plates, glass walls and other applications that enable fully transparent structures to be realised. A concise concept for quantifying the torsional stiffness of laminated glass beam elements is introduced – the Equivalent-Sectional Shear Modulus (ESSM), which is directly measured from the torque and sectional-rotation correlation in non-destructive torsion experiments. This method is advantageous as it allows for the measurement of overall rotation to torque response of laminated glass beams compositely rather than their individual components, resultantly decreasing the uncertainties of commonly adopted analytical approximations. A tailor-made, non-contact displacement measurement system based on the principles of binocular stereo-vision was developed, tested, verified, and employed to the torsion test procedure to increase the accuracy of photogrammetric measurements to be acquired. This incorporates the use of dense displacement sample targets on the glass beam which are measured and extracted using basic machine vision techniques, providing flexible, accurate, and non-intrusive measurements. Experimental torsion studies were performed on multiple samples of monolithic, two-layer, and three-layer polyvinyl butyral (PVB) and SentryGlas Plus (SGP) beams. The experimental setup, equipment, and procedures were continually improved and refined in a step-wise process throughout this work. The monolithic beams experimental ESSM results were validated against theoretical calculations from their elastic moduli relationship. Furthermore, the experimental ESSM results for two-layer and three-layer laminated beams were also compared with existing analytical solutions based on sandwich theory. Further experimental studies were also performed to evaluate the effects of ‘eccentric-torque’, where the effect of an eccentricated torsional load path on the overall torsional rigidity of the beam is studied, and on the effect of lengthened load-durations for SGP laminates. A variety of interesting and remarkable results were obtained regarding the composite torsional-mechanical behaviours of laminated structural glass beams and the optimisation of a first-of-its-kind glass beam torsion test approach. The results of this PhD thesis may help to support the further development of structural glass design codes and practices

Design and Performance of Cold Bent Glass

The demand for flat glass is high and increasing significantly in the building industry as a direct result of architectural requirements for lightness, transparency and natural light. Current architectural trends require glass in curvilinear forms for smooth free-form façades. Two principal challenges arise from this: to cost-effectively produce the desired curvature and; to ensure its safe performance after exposure to ageing. The recent availability of high strength glass provides an opportunity to address the first challenge by developing cold bent glass. Cold bending involves the straining of relatively thin glass components, at ambient temperatures, and is a low energy and cost effective manner of creating curvilinear forms. However, cold bending is not yet widely established as a reliable method. The aim of this thesis is to develop the understanding of cold bent glass during the bending process and to evaluate its post-ageing performance. This thesis, firstly, investigates the mechanical response of monolithic glass plates during the cold bending process. The stability of cold bent glass is investigated experimentally by bending it in double curved anticlastic shapes. A parametric numerical analysis involves different boundary conditions, geometrical plate characteristics and bending parameters. The principal outcome is that a local instability, now termed cold bending distortion, occurs when certain displacement limits are exceeded and could degrade the optical quality of the glass. An evaluation procedure is also formulated to set limits and aid designers/manufacturers to predict the mechanical response and the optical quality of the glass. Cold bent glass is subjected to permanent bending stresses throughout its service life and therefore, its strength degradation after ageing needs to be quantified. Analytical, experimental and numerical investigations are undertaken in this thesis to identify the most effective method for estimating glass strength (evaluation of destructive tests, required number of specimens, statistical analysis methods and sub-critical crack growth). The limited availability of naturally aged toughened glass and the absence of a reliable ageing standard impede the evaluation of its aged performance. Therefore, a parametric experimental investigation of artificial ageing methods on glass is undertaken in this thesis. A procedure for the evaluation of the strength of aged glass is finally, formulated to allow the selection of artificial ageing parameters that correspond to a target level of erosion. The knowledge on artificial ageing and strength prediction acquired above is finally implemented on different types of glass to determine their strength after ageing and assess their safe use in cold bending / load bearing applications. The investigation showed that fully toughened glass has a superior performance to chemically toughened or annealed glass. Overall, the research presented in this thesis demonstrates that high quality cold bent toughened glass can be created when certain applied displacement limits are respected. These can be used as a safe, cost-effective and energy efficient replacement to the more conventional hot bent glass. However, cold bending / load bearing applications in which the stressed glass surface is exposed to ageing, require glass with a relatively high case depth such as fully toughened or bi-tempered glass.Engineering and Physical Sciences Research Council UK (EPSRC), Eckersley o’Callaghan, Onassis Foundatio

Environmental impact and performance of transparent building envelope materials and systems

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Building envelopes are elements with a long lifetime, which provide a barrier between internal and external space and contribute to the internal environmental conditions provision. Their complex role ensures a large impact on the environmental and energy performance of a building and the occupant perception of a space. This study looks at the use of novel materials and processes to help reduce the environmental impact of buildings by improving facade and transparent roof design. There are three main strands to the work. First, novel building components, ETFE foil cushions were examined. Physical testing has shown that ETFE foil cushions compare favourably to double glazing in terms of thermal and daylighting performance which was also noted as one of the most likeable feature by occupants. Environmental impact analysis has indicated that ETFE foils can reduce the environmental impact of a building through reduced environmental burden of both the construction and operation of the building. Secondly, a cradle-to-gate Life Cycle Analysis (LCA) was carried out for float glass, which considered the environmental impacts of glass manufacture. The embodied energy was calculated to be 13.4 ± 0.5 GJ per tonne while the total number of eco-points 243 ± 11 per tonne. It is shown that float glass is comparable to the use of steel, and highly preferable to the use of aluminium as a cladding panel. Finally, a concept design tool (FACADE) was developed by defining a large number of office facade models and employing dynamic thermal, daylighting and environmental impact modelling to create a database which can be accessed through a user friendly interface application. A parametric analysis has indicated that using natural ventilation where possible can reduce the environmental impact of offices by up to 16%. Improving the standard of the facade and reducing the internal heat loads from lighting and equipment can reduce environmental impact up to 22%. This study makes a significant contribution to understanding the environmental impact of building envelope individual and integrated components.EPSR

Advanced fibre reinforced material : non-crimp composites

Abstract: Non-crimp fabric (NCF) composites combine the superior in-plane properties of unidirectional pre-impregnated tape (UDPT) and excellent out-of-plane properties of woven fabrics without their associated drawbacks of high manufacturing cost and crimping respectively. Research on such novel composite materials have mostly been parochial and focused on improving either the matrix or the reinforcement. The aim of this thesis is therefore to present a holistic and multifaceted study (in a life cycle vision of the composite) addressing the critical factors of matrix modification, dispersion quantification, testing optimisation and fibre reclamation from waste...D.Phil. (Mechanical Engineering

Numerical analysis of fatigue crack growth in welded joints with multiple defects

In the case of welded steel structures (such as pressure equipment), welded joints are often critical location for stress concentrations, due to different mechanical properties and chemical composition compared to the parent material, and due to changes in geometry. In addition, the presence of imperfections (defects) in welded joints can contribute to the increase in local stress, resulting in crack initiation. Recently, standards that are related to acceptable dimensions of various types of defects in welded joints started taking fatigue loading into account as well. For the purpose of this research, a 3D numerical model was made, of a welded joint with different types of defects (linear misalignment and a crack in the weld metal), based on the previous work, which involved static loading of the same specimen. In this case, fatigue was taken into account, and the simulation was performed using ABAQUS software, as well as Morfeo, an add-on used for determining the fatigue behaviour of structures via XFEM (extended finite element method). The welded joint was made using steel P460NL1 as the parent material, and EPP2NiMo2 wire was used for the weld metal. An additional model was made, whose defects included a crack and an overhang. Fatigue crack growth analysis was performed for this model as well, and the results for stress intensity factors and stress/strain distribution were compared in order to obtain information about how different defects can affect the integrity of a welded joint