1,721,156 research outputs found
INFLUENZA DELLA RUGOSITÀ SUPERFICIALE SULLA RESISTENZA ALLA DELAMINAZIONE DI RINFORZI ESTERNI IN FRP
No full textIl potenziale dei rinforzi in FRP (Fiber Reinforced Polymer) su elementi in cemento armato è
fortemente dipende dal legame tra il substrato di calcestruzzo e l’FRP. Quando la resistenza di
I. Iovinella, A. Prota, G. Manfredi, C. Mazzotti
tale legame viene superata si innesca nell’elemento un meccanismo definito delaminazione
che essendo un evento fragile deve essere sempre preceduto da meccanismi dovuti a flessione
o taglio. Tale meccanismo può innescarsi a causa della perdita di aderenza tra il calcestruzzo e
la resina, tra la resina e la fibra o tra i diversi strati di fibra. Dalle ricerche condotte è emerso
che il legame di aderenza dipende da una serie di fattori tra cui le proprietà dei materiali e le
caratteristiche del substrato di calcestruzzo. In particolare quest’ultime, ovvero la pulizia, la
rugosità e la compattezza del substrato, sono quelli che influenzano la forza di adesione tra la
resina ed il calcestruzzo.
Per tale motivo, prima di procedere all’applicazione di FRP, è uso comune trattare la
superficie del calcestruzzo attraverso una serie di operazioni mediante le quali esso viene
risanato, pulito, e reso adeguatamente ruvido. Alcuni dei più comuni trattamenti superficiali
sono smerigliatura, idroscarifica, bocciardatura, sabbiatura, ciascuno con vantaggi e svantaggi
associati a diversi fattori quali livello di rugosità raggiungibile, costi e tempi di elaborazione.
Dei molteplici studi condotti in merito alle problematiche legate all’applicazione dell’FRP
pochi si sono soffermati sullo sviluppo di metodi quantitativi per la descrizione dello stato
superficiale del calcestruzzo ed in particolare nella misura della rugosità superficiale
relazionando tale misura con la resistenza alla delaminazione del rinforzo.
Il Consiglio Nazionale delle Ricerche, nel DT-200/2004, in merito all’applicazione di FRP su
elementi di calcestruzzo in opera suggerisce, previa rimozione del calcestruzzo ammalorato,
trattamento delle armature e ripristino del copriferro, di eseguire una sabbiatura della
superficie del calcestruzzo al fine di ottenere una ruvidità di almeno 0,3 mm misurata con
strumenti idonei (ad esempio un profilometro laser). L'International Concrete Repair Institute
ha pubblicato delle linee guida per la preparazione delle superfici in calcestruzzo destinate
all’applicazione di compositi in FRP, che descrivono con cura diversi metodi di trattamento
superficiale indicando per ciascuno di essi vantaggi e svantaggi.
La mancanza di ricerche adeguate in tale campo determina la necessità di utilizzare
coefficienti di sicurezza elevati quando si ha a che fare con meccanismi di delaminazione.
Nel seguito del presente lavoro vengono illustrati i primi risultati di una campagna
sperimentale dedicata allo studio dell'influenza della preparazione superficiale sul legame
FRP-Calcestruzzo
Influence of surface roughness on the bond of FRP laminates to concrete
No full textThe potential of Fiber Reinforced Polymer FRP in the reinforcement of concrete structures has been shown in many studies and practical applications. However, few works have been focused systematically on the development of quantitative criteria to measure surface roughness and relate this parameter to the debonding stress. Roughness has a direct influence on the FRP performance in terms of bond to concrete, which is important to ensure the effectiveness of the external FRP reinforcement.Currently, there is not much evidence about the parameters related to surface state of concrete structures nor many guidelines about assessing the optimal conditions of concrete surface for the application of the FRP. To respond to these needs, the presented study deals with the effects of the surface characteristics of concrete on debonding strength of the FRP; this objective has been pursued by means of experimental tests on about 40 specimens characterized by different levels of roughness of the concrete surface. The paper describes the experimental campaign outlining the analyzed surface preparation procedures (i.e., sandblast, bush-ammering, grinding, brushing) and the subsequent tests performed on the installed FRP by means of two different test methods. The former is a laboratory method which performs shear tests to evaluate the debonding shear strength of the FRP reinforcement; the latter is pull-out test which is a typical method used for in situ check of quality of the FRP application. The results of these experimental tests are discussed in the paper with emphasis on the correlation between the roughness of the surface and the outcomes of both shear and pull-out tests; this information can be used in design in order to prescribe the minimum roughness level necessary to attain the expected debonding strength of the reinforcement
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
An effective measurement of the concrete roughness and its role on the definition of the debonding strength of external FRP reinforcement
No full textThe potential of Fiber Reinforced Polymer FRP in the reinforcement of concrete structures has been shown in many studies and practical applications. However, few works have been focused systematically on the development of quantitative criteria to measure surface roughness and relate this parameter to the debonding stress. Roughness has a direct influence on the FRP performance in terms of bond to concrete, which is important to ensure the effectiveness of the external FRP reinforcement.Currently, there is not much evidence about the parameters related to surface state of concrete structures nor many guidelines about assessing the optimal conditions of concrete surface for the application of the FRP. To respond to these needs, the presented study deals with the effects of the surface characteristics of concrete on debonding strength of the FRP; this objective has been pursued by means of experimental tests on about 40 specimens characterized by different levels of roughness of the concrete surface. The paper describes the experimental campaign outlining the analyzed surface preparation procedures (i.e., sandblast, bush-ammering, grinding, brushing) and the subsequent tests performed on the installed FRP by means of two different test methods. The former is a laboratory method which performs shear tests to evaluate the debonding shear strength of the FRP reinforcement; the latter is pull-out test which is a typical method used for in situ check of quality of the FRP application. The results of these experimental tests are discussed in the paper with emphasis on the correlation between the roughness of the surface and the outcomes of both shear and pull-out tests; this information can be used in design in order to prescribe the minimum roughness level necessary to attain the expected debonding strength of the reinforcement
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
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