1,720,963 research outputs found
Particle-based modelling of cortical meshes for soil retaining applications
No full textMetallic cortical wire meshes are extensively used to protect slopes and infrastructures in mountain regions. These structures are constituted by periodic patterns of steel wires and have a ductile non-linear behaviour. The installed mesh panels generally experience non-trivial boundary conditions which combined with their high deformability and the chance of local ruptures make these structures difficult to be modelled as a contin-uum. The Discrete Element Method (DEM) is particularly well suited for modelling the soil-mesh interaction problem, taking advantage of its potentials in handling large deformation, contact-detachment and interlock-ing between particles and the mesh. The mesh is modelled with two approaches and a puncture test on a single mesh panel is used for calibration. After that a simplified soil-mesh problem with a single mesh panel is con-sidered and compared with the results of a punch-mesh problem. The force-displacement behaviour experi-enced by anchors and edges of the panels are also discussed
Discrete element modelling of a soil-mesh interaction problem
No full textThe design strategies of metallic cortical meshes used for slope protection are mostly linked to the application of empirical and semi-empirical methods. This limitation is due to the difficulties in representing such complex large-deformation rock-soil-structure interaction problems: the intrinsic complexities of these structures is combined with the difficulties in describing the geometry both the mechanical and physical properties of the rock and soil behind. The Discrete Element Method proved their effectiveness in describing the non-linear and large strain behaviour of the soil, and recently also the mechanical response of steel wire meshes which are represented as regular patterns of remote interactions between nodes. In this work, a discrete element model of a double-twisted hexagonal wire mesh is calibrated on the base of experimental tensile tests on two wire types. The validation of the model is performed using the results of a standard punch test. The same mesh is then loaded by a granular layer constituted by discrete element particles mimicking the soil earth pressure. A comparison between the two load types is discussed with reference to the force-displacement curve and the distribution of the tensile stresses on the mesh panel. The effect of the boundary conditions is also analysed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Discrete element modelling of punch tests with a double-twist hexagonal wire mesh
Get PDFMetallic wire meshes are commonly used for rockfall protection and rockfall mitigation. Their design is mostly based on empirical results and experience. Due to the significant importance of these structures, their design needs to be more accurate and, therefore, numerical methods are nowadays used for improving and optimising the design. The most common approaches are the finite element method (FEM) and the discrete element method (DEM). The latter is used in this work as it is particularly well suited for studying discontinuous problems, including failure, with high accuracy. The study focuses on the validation of a numerical model of a double-twisted hexagonal wire mesh subject to punch tests. The numerical model is represented by a set of spherical particles at the physical nodes of the mesh. Remote interactions are implemented to represent the wires. The numerical predictions are compared to the results of experimental tests to calibrate and validate the model. In particular, the influence of the stress-strain curves of the single wire and double-twist on the punch tests are investigated by using deterministic and stochastic models
Design of Seismic Tests on Post-installed Anchors for Concrete and Masonry Applications
No full textThis paper discusses the design of an experimental campaign with the aim of studying the seismic behaviour of different types of post-installed anchors for concrete and masonry applications. The laboratory tests involve the study of fasteners with different functioning principles, namely bond, expansion and undercut. A preliminary literature review of actual codes and guidelines focused on this topic led to select a tri-axial shaking-table test.
These norms has been also considered to define both the dynamic input to be applied and the testing procedure. A FE model has been developed to define the layout of structures to be tested. This led to select two cross-shaped structures – four walls each – in order to reproduce different support conditions for the considered fixtures: full RC structure and RC frame with infill masonry walls. The influence of cracks on the behaviour of anchors are also considered in the design of the RC structure. The numerical model has been also used to define the mass to be applied on each anchor. Both selection and design of fasteners were also based on the actual guidelines on this field. Finally the paper presents the definition of quantities to be monitored and adopted instruments to analyse relevant accelerations and displacements
Variations on the Author
Get PDF“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
Shaking-table tests on post-installed anchors for concrete and masonry applications
No full textThe paper discusses the results of an experimental campaign carried out on different typologies of post-installedanchors. Tri-axial shaking table tests were performed in order to study the seismic behaviour for applications on concrete and masonry supports. Two cross-shaped structures were built at real scale, one with concrete walls and one as concrete frame with masonry infill panels. Two different conditions were investigated in the case of fasteners on concrete, namely uncracked and cracked support.
The tests were designed on the basis of US guidelines AC156 for seismic certification of nonstructural components by shaking table tests. The experiments were performed with input at increasing acceleration to study the effects induced at different seismic levels.
The results allowed the overall seismic behaviour of each fastening element to be studied, especially in terms of maximum sustained acceleration, anchor slippage from support and failure mode. The influence of cracks on these parameters was also investigated. The test plan also allowed a complete comparison among different anchoring methodologies, such as mechanical, chemical and undercut fasteners
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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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