1,720,966 research outputs found
Experimental and numerical investigation of float glass–GFRP hybrid beams
No full textDespite the great potentials of glass as a construction material, its brittle material behaviour poses major challenges to structural engineers when designing load-bearing glass structural members. This paper presents the load response and the failure behaviour of float glass–GFRP hybrid beams, when used as a mean of improving strength and ductility of float glass. Hybrid beams made from two layers of float glass sheets and an adhesively-bonded semi-transparent pre-cured GFRP interlayer were tested in four-point bending. The experimental results showed that double layer hybrid beams continued to take load even after the formation of the first major crack, and the beams were stronger and ductile than conventional single and multilayer float glass beams. Once the bottom glass layer has cracked the combination of the GFRP and the top glass layer carried the applied load whilst the gradual decrease in the stiffness due to the formation of new cracks ensures a ductile failure. Experimentally-validated finite element (FE) models that predict the evolution of stresses, stiffness and failure load of single and double layer glass beams, and glass– GFRP hybrid beams are also presented
Modelling residual stress in glass: Incorporation of the full stress field using a few stress measurements
No full textA comprehensive modelling technique for incorporating the effects of residual stresses (RS) in commercially available float glass (annealed glass and thermally-strengthened glass) is presented. RS are developed in glass due to the differential cooling experienced by glass during manufacturing (i.e. outer regions of glass cool and solidify first while the inner regions remain hot). Glass manufactures expect compressive surface RS of magnitude of ~80-150 MPa in thermally-strengthened glass. Surface compressive prestress enhances resistance against the development and propagation of surface cracks in thermally-strengthened glass. Although no RS are expected in annealed glass, research showed some RS in annealed glass, albeit of small magnitudes (usually <10 MPa). The effects of RS are critical for the structural performance and failure behaviour of glass structures. But, there is no accurate method to incorporate RS in stress analysis. Accurate stress analysis is required for design since glass is brittle and failures trigger at locations where high tensile stresses present. Therefore, the existing design practice of the ignorance of RS in annealed glass, and limiting the maximum design surface tensile stress determined from an analysis without incorporating RS to the surface RS specified by the manufactures of heat-strengthened glass usually result in structurally inefficient and cost expensive structures. Analysis of RS in glass by explicitly modelling differential cooling and the complex multi-physics process of glass manufacturing is virtually impossible, since the exact details of the thermal parameters and the viscous response of glass at different temperatures are unknowable. These parameters are difficult to be determined as they depend on complex phenomena, such as convection, radiation, thermal vibration and microstructural rearrangements. Rather than attempting to model the unknowable multiphysics phenomena of the generation of RS, we propose to model the RS distribution as the static elastic response of glass if a misfit strain (i.e. eigenstrains) representing the effects of all the mechanisms that contribute to the generation of RS in glass.Knowledge of a representative eigenstrains distribution in a given glass is a prerequisite in the proposed RS modelling technique. However, the representative eigenstrains distribution cannot be known at the beginning of an analysis and the determination of the eigenstarins is not trivial. We propose to determine a representative eigenstrains distribution by matching (in a least squares sense) the resultant RS distribution for an sensibly chosen initial assumed eigenstrains distribution with experimentally measured RS values at a finite number of locations. Finite element (FE)-based analyses are proposed for the stress analysis given the complex nature of the problem. In the present study, a scattered-light-polariscope (SCALP) was used to experimentally obtain RS values at a few selected locations in a given glass specimen. The recent advances in the SCALP techniques enable accurate measurements of RS in glass, in particular close to the surface regions. After an accurate estimate of the eigenstrain distribution has established, the full RS distribution in the glass specimen can be determined from a FE analysis by incorporating the estimated eigenstrains as a misfit strain distribution. The solution formulated this way satisfies equilibrium, compatibility, boundary conditions of the glass specimen, and the resultant RS distribution is entirely self-consistent. The step-by-step procedure of the proposed RS modelling technique is presented in Figure 1. Figure 2a shows the RS values measured at seven discrete points (up to 2 mm deep from the surface) of a 10 mm thick annealed glass specimen. The stress values were measured using a SCLAP with an accuracy of ±2MPa (as reported by the manufacture). Using the eigenstrains analysis described above, an estimate of the actual eigenstrains in the glass specimen was determined (Figure 2b). The estimated eigenstrains distribution was then incorporated in a 3D FE model to determine the full RS distribution. Figure 2c shows the full RS distribution in the middle region of the mid-plane (xz plane) of the glass specimen. Figure 2a also shows the comparison between the RS depth profile predicted from the eigenstrain analysis and the experimentally measured values. As can be seen from Figure 2a, the stresses predicted by the proposed model compared well with the measured values. Using the eigenstrains technique the RS distribution in thermally-strengthened glass were also determined. For example, Figure 3d shows the comparison between the predicted RS depth profiles in 10 mm thick annealed and fully-tempered glass. The eigenstrains technique of RS modelling was extended to analyse stress states in practical applications of glass structures, For example, Figure 3 shows the predicted RS distribution around a central hole (e.g. a hole drilled in glass for a bolted connection) in a fully-tempered glass piece. A 3D FE model was used in the analysis, and only a quarter of the specimen is modelled due to symmetry. The results showed a clear interaction between the geometry and the RS distribution. For example, RS distribution is not uniform over the internal surface of the hole, and this suggests the actual spatial distribution of RS must be taken into account in design in order to ensure structurally efficient, safe structures. The finding of this paper shows RS distributions in annealed and thermally-strengthened glass can be modelled using the knowledge of eigenstrain depth profile that may be determined from an inverse eigenstrain analysis using RS values measured at a few location of a given glass specimen. The paper also shows that the eigenstrain analysis can be implemented in FE models for accurate stress analysis of glass structures
Mechanical prestressing of annealed glass beams using pretensioned GFRP: characterisation and potentiality
No full textThis paper presents the results of an experimental investigation on the mechanical behaviour of annealed glass beams prestressed using adhesively-bonded pretensioned Glass Fibre Reinforced Polymer (GFRP) strips. The results show that the glass beams prestressed using pretensioned GFRP showed an increased load capacity compared to equivalent glass beams reinforced with unprestressed GFRPs. The prestressed glass beams showed a notable ductile post-cracked behaviour similar to annealed glass beams reinforced with unprestressed GFRP strips. The results also show that the proposed glass prestressing technique prevented premature debonding of the GFRP strips from the glass beams and explosive final failure of the glass beams, unlike in the mechanically-prestressed glass beams investigated in the literature where these failures were commonly observed
Characterisation of the mechanical behaviour of annealed glass–GFRP hybrid beams
No full textThis paper presents the results of a combined experimental and numerical investigation on the mechanical behaviour of annealed glass–Glass Fibre Reinforced Polymer (GFRP) hybrid beams. The experimental results showed that an adhesively-bonded GFRP interlayer significantly improved the strength and ductility of annealed glass beams. The paper also presents the post-breakage behaviour and the response of damaged beams in unloading. The paper numerically investigates the degree to which the strength and stiffness of the hybrid beams can be modelled by using finite element (FE) analyses. The novelty of work also includes numerical modelling and validating the through-thickness stress profiles in the hybrid beams
Glass–GFRP hybrids: from brittle glass to ductile and high strength structural glass
No full textThis paper presents selected findings from a research programme that aimed to exploit the use of adhesively-bonded Glass Fibre Reinforced Polymer (GFRP) laminates as a mean of improving strength and ductility of glass structural elements. In the first half of the paper, using the results of an experimental investigation of the load response and failure behaviour of annealed glass beams reinforced with GFRP laminates, it is shown that the load resistance and the ductility of the glass beams can be enhanced. In the latter half of the paper, it is shown that the stress concentration geometries and bolted joints in annealed glass can sustain greater loads with greater ductility, even after microcracks formed, if the glass is reinforced with adhesively-bonded GFRP laminates
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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