1,720,997 research outputs found
Experimental Damage Identification in Masonry Structures by OMA
No full textThis paper presents a study carried out in different types of masonry structures to identify existing damage through dynamic identification techniques using operational modal analysis. A cross vault, a masonry wall and a simple clay brick construction have been analyzed. The three cases have been tested on a full scale in the laboratory. The cross vault has been subjected to a settlement of one of its supports, the damage has occurred and then it has been repaired by using Textile Reinforced Mortars (TRM). In the case of the wall and the simple construction, the damage has been generalized by means of horizontal loads simulating a seismic action by a cyclic incremental load, after the generation of the damage, it has been repaired using TRM. In all cases, a dynamic identification has been carried out prior to the generation of the damage, after the generation of the damage and later after its repair, finally after a new process of damage the structural health changes have been monitored. In the four phases, an identification of the dynamic characteristics of the structures has been carried out, both main frequencies and damping factor associated with each mode shape. Regarding operational modal analysis, the first vibration modes have been identified. Singular Value Plot have been obtained through the EFDD technique. In general terms, the results of the investigation showed that the effect of cracking generated by both horizontal cyclic loads and vertical displacements located in one of the supports generated a decrease in the vibration frequencies and an increase in the structural damping factors for the different vibration modes. On the other hand, in relation to the effect of the reinforcement techniques employed, the results showed the feasibility of recovering or even slightly increasing the stiffness of the original damaged structure. However, the results for the strengthened structures also showed that the intervention on the damaged structure tended to reduce the structural damping factors with respect to the unreinforced structure. In addition, it was also observed that after the tests the reinforced and newly damaged structures showed dynamic characteristics very similar to the unreinforced damaged structures
Analysis of a Metallic Pedestrian Bridge under Dynamic Human Loads in Pre and Post Reinforcement Phases
No full textThe purpose of this work is to study the dynamic
behavior of a pedestrian bridge in Alicante, Spain. It is a very
slender footbridge with vertical and horizontal vibration
problems during the passage of pedestrians. Accelerations
have been recorded by accelerometers installed at various
locations of the bridge. Two scenarios, in free vibration (after
the passage of a certain number of pedestrians on the bridge)
and forced vibration produced by a fixed number of
pedestrians walking on the bridge at a certain speed and
frequency. In each test, the effect on the comfort of the
pedestrians, the natural frequencies of vibration, the mode
shapes and damping factors have been estimated. It has been
found that the acceleration levels are much higher than the
allowable by the Spanish standards and this should be
considered in the restoration of the footbridge
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
Dynamic Behavior of a Pedestrian Bridge in Alicante (Spain)
No full textThe purpose of this paper is to study the dynamic behavior of a pedestrian bridge in Alicante, Spain, which showed vertical and horizontal vibration problems. Moreover, the deck’s structural steel showed severe corrosion damage. Hence, two cases were analyzed: before retrofitting the structure using glass fiber–reinforced composites (GFRPs) and after. While the GFRP was designed for esthetic and durability purposes only—and not for structural retrofitting—it changed the mass and stiffness of the footbridge, affecting its dynamic characteristics. The natural frequencies, mode shapes, and modal damping factors of the bridge were calculated based on accelerations recorded at 11 points on the bridge under different conditions—i.e., ambient vibration and forced vibration produced by a fixed number of pedestrians
walking on the bridge at a certain speed and frequency. A numerical model was also designed in order to compare the experimental and numerical result
Dynamic Identification of a Pedestrian Bridge using Operational Modal Analysis
No full textPostiguet footbridge in Alicante is a very sensitive structure to vertical vibrations and it has been restored with fiber glass composite materials to improve the response to dynamic loads. This article describes the studies carried out on the walkway in the conditions prior and after to the intervention of structural restoring. This allowed identifying the characteristic parameters of the dynamic behavior of the footbridge. The values of the natural frequencies of vibration and the damping coefficients of the structure have been determined for the different modes of vibration in the two structural conditions. Operational Modal Analysis (OMA) techniques for the modal identification have been utilized and a numerical model has been built to clearly identify the vibration modes and to compare the results
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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