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A review on the bond behavior of FRP composites applied on masonry substrates
No full textThe need of repairing and retrofitting masonry buildings, typical of Italian and European built heritage, determined a growing interest towards the development of effective and cost efficient innovative strengthening solutions. Among the different techniques currently available, the adoption of composite materials, such as Fiber Reinforced Polymers (FRPs), proved to be one of the most viable solutions for the strengthening of masonry structures. If not properly fixed, a common failure mode of this system is the early debonding of the reinforcement from the substrate. For this reason, several experimental tests and numerical analyses are currently available in the literature, clarifying and predicting the bond behavior of FRP glued to masonry substrates. The purpose of this paper is to provide an overview of the results obtained by the different experimental works, of the numerical analyses performed both for evaluating and validating experimental results and of the simplified analytical models currently available for the prediction of the maximum capacity of the strengthening systems. Results of extended experimental campaigns, carried out also within different Round Robin Test (RRT) series, with several laboratories involved, and recent model calibrations will be discussed together with the approach proposed by the actual guidelines
Rinforzo di pareti per azioni fuori dal piano con materiali compositi FRCM
No full textDiversi terremoti avvenuti nel corso
degli ultimi decenni hanno
mostrato la vulnerabilità degli
edifici in muratura, tipici del patrimonio
culturale italiano ed europeo, nei
confronti delle azioni simiche. In particolare,
l’analisi dei danni post-sisma ha evidenziato
una manifesta sensibilità delle pareti
in muratura alle azioni orizzontali agenti
fuori dal piano, con conseguenti collassi
parziali o totali dell’edificio. Per far fronte
alla necessità di ripristinare e rinforzare
le costruzioni in muratura, nell’ottica di incrementarne
la sicurezza, nel corso degli
ultimi anni sono state proposte ed impiegate
diverse tecniche di rinforzo tradizionali
o innovative. Tra queste ultime, il rinforzo
strutturale basato sull’impiego di materiali
compositi sta diventando sempre più
diffuso, in virtù dei diversi vantaggi che
questi offrono rispetto a quelli tradizionali.
In questo contesto, l’uso di materiali
compositi FRP (Fiber Reinforced Polymers)
o FRCM (Fiber Reinforced Cementitious
Matrix) ha dimostrato di essere
una delle soluzioni più adatte, ma la
conoscenza relativa all’utilizzo della seconda
tipologia di sistemi di rinforzo, in
particolare, una volta applicati a pareti in
muratura, è ancora limitata, soprattutto
se si analizza il loro comportamento per
azioni fuori dal piano [1-3].
L’obiettivo dell’articolo è analizzare il comportamento
di pareti in muratura rinforzate
con materiali compositi FRCM sollecitate
da sforzo assiale e azioni orizzontali
fuori dal piano (in modo da simulare la
loro risposta nei confronti di azioni sismiche),
riportando le prime evidenze di una
campagna sperimentale in corso presso
l’Università di Bologna. A tale scopo, è
stato sviluppato un nuovo set-up in cui
poter testare campioni di pareti in muratura
in scala reale, rinforzate con diverse
tipologie di fibra di vetro e acciaio.
Verrà presentata una breve analisi relativa
al comportamento dei muri rinforzati
testati, verificando l’efficacia dei sistemi
impiegati e descrivendo modalità di crisi
e aspetti peculiari emersi nel corso dei
test sperimentali. La disponibilità di risultati
relativi a prove di flessione fuori piano,
insieme ai risultati di prove di trazione
e aderenza tradizionali, condotte sulla
stessa tipologia di materiali, ha consentito
di indagare l’estendibilità delle evidenze
sperimentali ottenute su campioni in
scala ridotta a campioni in scala reale.
La campagna sperimentale in corso ha
come obiettivo quello di ottenere dati utili
allo sviluppo di future formule di progetto
e prescrizioni normative da applicare per
questa categoria di materiali compositi
Retrofitting with FRCM composites: shear and flexural behaviour of strengthened masonry walls
No full textStructural strengthening using composite materials is nowadays one of the most interesting techniques to overcome weaknesses of masonry structures constituting large part of the building heritage. The use of FRCM composites is becoming more and more widespread due to some limitations of FRP retrofitting systems. In this framework, the presented experimental study is aimed at evaluating the in-plane and the out-of-plane behaviour of masonry walls strengthened with different types of FRCMs, analyzing in detail failure modes, capacity increments and efficiency of the strengthening systems when tested using two different configurations. To this purpose, bidirectional basalt grids and unidirectional steel fiber sheets, coupled with a lime based mortar, were used for retrofitting clay brick masonry walls subjected to diagonal compression tests and out-of-plane flexural tests. Experimental outcomes, when considering the in-plane or the out-of-plane direction, show that the different layout adopted strictly influences the flexural and shear strengthening efficiency of the reinforcement
Bond behavior of FRCM composites applied on concrete and masonry
No full textI materiali compositi FRCM (“Fiber Reinforced Cementitious Matrix”) sono stati recente-mente introdotti nelle applicazioni di ingegneria civile per il rinforzo di elementi in muratura e c.a. Lo scopo dello studio sperimentale è quello di valutare il comportamento, in termini di aderenza, di materiali compositi FRCM in carbonio e vetro, nella forma di reti bidirezionali o tessuti unidirezionali, applicati su diversi supporti utilizzando una malta cementizia e un promotore di adesione. Le evidenze sperimentali ottenute sulla muratura utilizzando malta a base cementizia sono state confrontate con i risultati derivanti dagli stessi sistemi di rinforzo applicati con malta a base calce. Tutti i campioni sono stati sottoposti a prove di aderenza, in modo da valutare le possibili modalità di crisi, la capacità massima e il comportamento globale in termini di spostamenti e deformazioni (grazie alla tecnica della Digital Image Correlation). I risultati sperimentali hanno evidenziato le buone prestazioni dei sistemi di rinforzo testati se applicati in combinazione con il promotore di adesione.Fiber Reinforced Cementitious Matrix (FRCM) composite materials have been recently introduced in civil engineer-ing applications for the strenthening of masonry and reinforced concrete elements. The aim of the presented experimental study is to evaluate the bond behavior of carbon and glass FRCM composite materials, in the form of bidirectional grids or unidirectional sheets, applied on different substrates by using a cementitious mortar together with an adhesion promoter. Experimental outcomes obtained on masonry using a cementitious mortar have also been compared with the results coming from the same strengthening sys-tems applied with lime mortar. All specimens were subjected to single-lap shear tests until failure, in order to evaluate failure modes, maximum bond capacity and the whole samples behavior in terms of displacement and strain maps (thanks to Digital Image Correla-tion technique). Experimental outcomes highlighted the good performance of the strengthening systems tested when applied in com-bination with the adhesion promoter
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
FRCM composites for the out-of-plane retrofitting of masonry walls
No full textSeveral earthquakes occurred during the last decades have shown the seismic vulnerability of masonry buildings,
typical of Italian and European built heritage. Post-earthquake damage assessment has often highlighted the
weakness of masonry walls when subjected to out-of-plane actions, with a consequent partial or total collapse of
the building. To this purpose, different strengthening techniques have been proposed in recent years for repairing
and retrofitting masonry constructions in order to extend their service life and improve their structural safety.
Among them, structural retrofitting with innovative techniques, such as those based on FRP and FRCM
composites, is becoming increasingly widespread, thanks to the significant advantages of these materials with
respect to the traditional ones. Despite the growing use of these innovative systems, the knowledge about FRCMs
when applied on masonry structures is still quite limited, in particular if their out-of-plane behavior is concerned. In
this framework, the aim of the present paper is to analyze the out-of-plane behavior of masonry walls strengthened
with different types of FRCM composite materials subjected to axial force and horizontal out-of-plane actions. In
order to test full-scale masonry panels, a purposely designed experimental set-up was used for evaluating their
behavior under seismic actions. Experimental outcomes will be presented in terms of failure modes, maximum
capacity and analyzing differences with reference to an unreinforced wall. The availability of results coming from
tensile and bond tests performed on the same materials allowed also to evaluate and compare the out-of-plane
capacity of masonry walls with the results of simple theoretical models. The experimental campaign, still in
progress, is also aimed at obtaining useful data for the calibration of design formulas suitable for this type of
strengthening system
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