1,720,964 research outputs found
3D collapse mechanisms of masonry bridges subjected to horizontal actions
Full text linkA large number of existing masonry arch bridges are still in use in the Italian roadway and railway networks. Most of them were built more than one hundred years ago, designed considering only gravitational loads without any seismic analysis. To keep these works in service, it is necessary to have tools that can describe and predict the structural behavior of the bridge when subjected to extreme actions. For this reason, a threedimensional rigid-block analysis for masonry arch bridges has been developed. In the model, the main structural masonry elements (vault, pier, abutments, spandrel wall) are discretized as an assemblage of rigid blocks, which interact via no-tension contact surface with Coulomb friction. This approach allows reproducing with good accuracy the tri-dimensional collapses mechanisms of some real masonry arch bridges recently collapsed due to extreme events
The thrust line in masonry arches: a new simplified algorithm
No full textMasonry arches and vaults have been widely used in the past to construct horizontal structural elements using materials with low tensile strength. Initially, the design methods used were mostly based on empirical rules derived from the experience of builders. In more recent centuries, however, analytical theories and graphical methods have been developed to formalize the static behaviour of the masonry arch. Although computational methods for evaluating masonry arch structures have been widely developed in recent decades, graphical and analytical methods are still simple and clear tools for understanding the structural behaviour of these structures. Therefore, a simplified method for identifying the thrust line in masonry arches is presented in this paper. The proposed algorithm is then applied to several case studies, and the results obtained are compared with those derived from finite element models
Damaged masonry arch bridges strengthened with external post-tensioning: Experimental and numerical results
No full textThis paper deals with the structural performance and strengthening of damaged masonry arch models representative of two longitudinal sections typical of existing single-span masonry railway bridges. The two masonry arch models were tested in laboratory under loading-unloading cycles of increasing vertical loads applied at 26% of the net span. The arch models previously damaged by imposing loading-unloading histories were tested in the strengthened condition. The strengthening used is an external post-tensioning system composed of two cables anchored to the arch intrados. Experimental results have shown an increase in the bearing capacity and ductility of the arch models after the application of the post-tension. Finally, the results obtained from the experimental campaign have been compared with the numerical ones, obtained by implementing a rigid-block analysis
Post-tensioning system as a strengthening solution for masonry arch bridges: numerical and experimental results
Full text linkOne of the most common bridge typologies in roadway and railway networks in Italy is the masonry arch bridge, typically built more than a hundred years ago. To keep these structures operatives with increasing traffic load, strengthening interventions are required in some cases. The solution investigated in this work is the external post-tensioning system, which consists of applying external loads to the arch by means of tensioned cables, resulting in a better configuration of internal forces. An experimental campaign was conducted on pre-damaged single span masonry arches by anchoring the cables to the intrados of the arch. The results of cyclic eccentric vertical load tests show an increase in displacement and load-carrying capacity. Numerical tests were performed to validate the experimental results using the rigid-block analysis method. The comparison between the experimental and numerical results is reported in terms of limit load capacity
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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