1,720,960 research outputs found
A parametric numerical study on the behavior of large precast tunnel segments during TBM thrust phase
No full textDuring the last two decades, Fiber Reinforced Concrete (FRC) was adopted in several segmental tunnel linings. The benefits related to the inclusion of fiber reinforcement in cementitious composites are mainly related to the increase of post-cracking tensile residual properties. FRC allows to reduce or avoid conventional reinforcement leading to a more efficient segment production process. The application of Tunnel Boring Machine (TBM) thrust jack forces during the lining construction stage is one of the most demanding loading conditions, since high-concentrated forces are introduced in last installed segments, especially for large diameter lining. Hence, special attention should be devoted to this phase by considering parameters which may affect segment structural response. To this aim, the behavior of a lining having large diameter during TBM operations was investigated by means of a broad parametric numerical study concerning segment configuration, irregularities and lining slenderness. The following reinforcement solutions were also considered: traditional steel rebars only, steel fibers reinforcement only and a combination of them (hybrid solution). The study clearly proved that segment configurations as well as irregularities strongly affect the structural behavior of segments. The hybrid reinforcement or FRC only solution having high post-cracking performance may guarantee the same response of RC solution
A model for predicting the splitting bearing capacity of Fiber Reinforced Concrete elements under partially loaded areas
No full textConcrete elements are frequently subjected to partially loaded areas; a typical example is represented by precast tunnel segments. In fact, during the excavation process, the hydraulic jacks of the boring machine exert, on the last assembled ring, high forces concentrated on small areas with respect to the size of ring joint. Similarly, when lining is embedded in ground, high hooping forces are transmitted through longitudinal joints, which present a contact zone smaller than the segment cross section. In both cases, spreading these loads into tunnel segments result in tensile transverse stresses which may cause splitting cracks. In the last decades, the growing desire to find more economic and sustainable solutions has driven enormous efforts in the tunnel industry to find new design solution such those based on Fiber Reinforced Concrete (FRC) or a combination of FRC and traditionally steel rebars. Research studies have already demonstrated the ability of fibers in controlling splitting crack phenomena. However, there is a lack of knowledge on reliable analytical approaches to quantify these benefits. The main aim of this paper is to develop a new model for determining the bearing capacity of FRC elements under partially loaded areas when splitting failure occurs. The analytical model herein reported allows a good prediction of the maximum loads exhibited by FRC prisms tested under high concentrated loads, whose data were selected from the literature
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Precast tunnel segments for metro tunnel lining: A hybrid reinforcement solution using macro-synthetic fibers
No full textThe addition of fibers has been proven successful to simplify reinforcement in precast tunnel segments, allowing as a function of both segment typology and fiber reinforced concrete (FRC) toughness a total or partial replacement of the conventional reinforcement. Results from an experimental research aimed at comparing the structural behavior of segments made with conventional (only rebars, RC) or hybrid (rebars + fibers) reinforcement are presented. The experimental program consisted of flexural and point load tests (which reproduces the jack actions during TBM operations) carried out on four large-scale precast tunnel segments representative of a metro tunnel lining characterized by an internal diameter of 5.80 m and a thickness of 0.30 m. The main goal of the experimental program was to evaluate the possibility of using macro-synthetic polypropylene fibers (Polypropylene Fiber Reinforced Concrete, PFRC) in combination with a lower amount of conventional rebars (optimized reinforcement, RCO) for guaranteeing the required segment performance. Experimental results indicate that macro-synthetic fibers may be very effective in combination with conventional rebars to withstand the main stresses that arise in a segment both at initial and final phases, proving that the adoption of hybrid reinforcement solution using macro-synthetic fiber is possible for metro tunnel lining
- …
