1,720,960 research outputs found
Preliminary Assessment of the Seismic Vulnerability of Three Inclined Bell-towers in Ferrara, Italy
No full textThree inclined historical masonry towers, located in the city of Ferrara (North-East region of Italy), are analyzed under seismic loads employing advanced numerical models. This study provides a critical review on the conservation state, present vulnerabilities, influence of peculiar structural features, and future need for strengthening interventions. Three scenarios were performed, mimicking the seismic severity of earthquakes for three different return periods: 50y, 200y, and 500y. The mechanical properties adopted for the models were extracted by tuning the dynamic response of the models with ambient vibrations test results. A concrete damage plasticity material, with a simplified multilinear softening in both tension and compression, is here adopted. Three parameters are investigated for an insight into the seismic performance estimation: (i) the damage pattern, (ii) the dissipated plastic energy, and (iii) the top displacement. Nonlinear dynamics simulations show the dissemination of structural damages for relatively low magnitude of ground acceleration, where clear failure mechanisms are prone to be activated. The present case studies exhibit unsymmetrical failure mechanisms due to the geometrical features, favoring the crack propagation in in-tension sidewalls, or stability loss of compressed walls. From a preliminary estimation of their seismic vulnerability, it is deduced that a relatively high risk is still present
Implementation of pushover analysis for seismic assessment of masonry towers: Issues and practical recommendations
Full text linkSeismic assessment is a paramount issue and a valuable instrument towards the conservation of vulnerable structures in seismic prone regions. The past seismic events have highlighted the vulnerability of masonry towers that is exhibited by severe structural and nonstructural damages or even collapses. The preservation of existing structures, mainly focused on the built heritage, is emerging and imposing substantial enhancements of numerical methods, including pushover analysis approaches. The accuracy of the estimated seismic capacity for these structures is correlated with the assumed strategies and approximations made during the numerical modeling. The present paper concerns those aspects by exploring the limitations and possibilities of conceiving pushover analysis in the finite element method environment. The most crucial target is tracing in a pushover capacity curve the corresponding initiation of structural damages, maximum load-bearing capacity, and the ultimate displacement capacity. Different recommendations for achieving this target have been proposed and illustrated for practical utilization. Three representative geometrical towers, adopting three different materials and five different load patterns, are investigated in this study. The load pattern’s role and necessity of the displacement-like control approach for the pushover analysis are exploited. This paper highlights the load-bearing capacity overestimation when the force-controlled are implemented. The material model influences the achievement of softening branch with a distinguishable displacement 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
Seismic assessment of a venetian bell tower taking into account soil-structure interaction
No full textThe paper gives a preliminary insight into the seismic vulnerability of bell towers, discussing a real case study, namely a masonry tower built in XIX century and located in the Province of Venice (Italy). Such a case study is fully investigated using different advanced FE strategies. The case study shows structural features often common in other cases, such as the foundation rotation due to soft soils, which causes the tower to lean. Both these parameters, the soil-structure interaction and the inclination, are expected to play a crucial role in the dynamic response and the lateral bearing capacity reduction. The present literature suggests different approaches to model and to account for such parameters, whereas technical codes mostly seem to propose simplified procedures that result in an underestimation of the real effect. The role of the soil is observed to be crucial in the shape and excited mass changes of the natural modes, thus implicitly modifying the seismic response. Furthermore, in general, the out-of-verticality of a tower causes the concentration of the vertical stresses and a significant capacity drop. In the present paper, different FE simulations are performed in order to investigate the actual dynamic behavior of the tower under study, to be compared with standard modeling used for bell towers
Limit analysis approach for the seismic vulnerability reduction of masonry towers through strengthening with traditional and innovative materials
Full text linkThe paper investigates the possibility and the effectiveness of reducing the seismic vulnerability of masonry towers by means of composite materials and traditional steel bands. Masonry towers are very widespread in Italy, both as bell towers for churches and defense towers in medieval cities and castles. Masonry material, presenting low mechanical properties, is not suitable to withstand significant tensile and compression stresses induced by earthquake loading. The slenderness of these structures is another factor that can reduce the bearing capacity when significant stresses are present in specific structural parts. The seismic vulnerability of masonry towers is very high, as a consequence of both poor material properties in tension and high compression levels at the base of the structure. Moreover, Italy is characterized by a high potential risk to be stricken by moderate/high seismic events, as experienced in the last decades. In such a situation, the seismic upgrading of masonry towers could appear rather important. Seismic upgrading by introducing both traditional steel bars and composite materials as strips or rebars is analyzed in detail for different towers. Based on some a priori assumed failure modes (one proposed by Heyman), simplified models from a limit analysis approach are here discussed and used to define the most suitable retrofitting solution. The retrofitting possibilities consist of: a) horizontal hooping rings; b) vertical pre-stressed tie rods; c) vertical composite strips. A simplified straightforward relationship is found between the retrofitting requirements and seismic hazard. The procedure is applied for a wide range of geometrical properties and appears to be fast and reliable
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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