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Rinforzo di colonne murarie a sezione quadrata e circolare mediante confinamento con materiali compositi
No full textCircular Masonry Columns Confined with FRP
No full textEmerging techniques that use fibre reinforced polymer (FRP) composites for strengthening and conservation of historic masonry are becoming increasingly accepted. Structural
enhancement of masonry elements built with natural stones is frequently needed for columns which are prone to brittle failure under seismic forces or static overloads.
External confinement techniques are commonly used to strengthen compression members. In this work an extended experimental work is presented in order to show the mechanical behaviour of circular masonry columns built with calcareous blocks that may be commonly found in Italy, especially in historical buildings. Carbon FRP sheets were used for external reinforcement, different amount of FRP reinforcement and different schemes of FRP reinforcement were studied.
Strengthening was applied on specimens that were damaged under different levels of load.
Different stacking schemes were used to build the columns. A new reinforcement technique was also tested using FRP bars for columns with cross section formed by four different blocks.
Experimental results revealed the effectiveness of confinement also for damaged columns that were loaded with 80% of ultimate load before strengthening.
A computation of the ultimate load was conducted using the Italian CNR recommendations to show the proposed design approach. A previously developed analytical model was applied for
computation of expected experimental values
Duttilità di travi iperstatiche in C.A. rinforzate con materiali FRP
No full textL’impiego dei materiali compositi fibrorinforzati a matrice polimerica (FRP) per il rinforzo flessionale di travi in
calcestruzzo armato (C.A.) è generalmente concepito con riferimento alla domanda di resistenza dell'elemento
strutturale. Nelle travi continue tuttavia la presenza del rinforzo flessionale sotto forma di lamine in FRP produce
importanti implicazioni anche sul comportamento flessionale in termini di fessurazione, dunque deformabilità, e di
duttilità. Al momento le linee guida progettuali dedicate non forniscono strumenti di calcolo, per tener conto della
eventuale ridistribuzione delle sollecitazioni nelle travi continue rinforzate dall'esterno con materiali FRP. Talvolta
i codici nazionali trascurano gli effetti di alcuni parametri che determinano la effettiva ridistribuzione del momento
flettente, producendo in tal modo delle previsioni eccessivamente conservative.
Nel caso di travi continue rinforzate con materiali FRP un calcolo con ridistribuzione deve tenere in conto della
ridotta capacità rotazionale della sezione, in corrispondenza dello stato limite ultimo. Dunque si deve considerare
una riduzione della duttilità strutturale, intesa come rapporto tra la rotazione ultima e la rotazione in corrispondenza
dello snervamento dell’armatura in zona tesa, sebbene i primi studi teorici e sperimentali sull’argomento abbiano
già dimostrato che una significativa ridistribuzione della sollecitazione flettente è possibile anche in presenza di
rinforzo esterno con materiali FRP. Nel presente lavoro è presentato uno studio sul comportamento flessionale di
travi continue in C.A. attraverso una analisi sperimentale e la verifica di un modello teorico sviluppato dagli autori
e presentato in precedenti lavori
FRP-Confined Masonry: from Experimental Tests to Design Guidelines
No full textHistorical masonry construction are prone to brittle failures under seismic or static overloads. Thus retrofit and strengthening of masonry structures, in order to furnish structural ductility and additional strength, is of primary importance for the maintenance of the European Architectural Cultural Heritage. Confinement with Fibre Reinforced Polymer (FRP) materials demonstrated to be an effective solution in a large number of cases. In this research program extensive experimental tests were conducted to calibrate design guidelines for FRPconfined masonry columns, which were introduced in the CNR DT-200 Italian document. Columns built with lime or with calcareous blocks, commonly found in Italy in historical buildings, were tested under compression static loads. Rectangular masonry columns were tested taking into account the influence of several variables: different strengthening schemes, curvature radius of the corners, number of composite layers, cross-section aspect ratio and height of the specimens. Materials characterization was carried out to study the properties of plain masonry. For all cases the experimental tests evidenced a significant increase in load carrying capacity and ductility after FRP-strengthening, which identified the columns as ductile elements despite to the brittle nature of the unconfined masonry. Differences in mechanical behavior due to the geometry of the columns, to the nature of different materials, to different strengthening schemes and to the amount of reinforcement are presented and discussed in the paper. The calibration of design equations recently developed by Italian CNR was conducted by using experimental results
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Effects of CFRP strengthening on the moment redistribution of reinforced concrete continuous beams
No full textThe use fibre reinforced polymer (FRP) composites for flexural strengthening of reinforced concrete beams was the first application for these materials, studied in the last decades. Nowadays real applications are found worldwide. Nevertheless, the issues concerning the strengthening of continuous RC beams are currently an interesting research field, since the largest part of the past studies was done on simply supported beams.
This paper presents the results of experimental tests on continuous reinforced concrete (RC) beams tested on real scale dimensions. The internal flexural steel reinforcement was properly designed in order to allow steel yielding before the collapse; the shear reinforcement was designed in order to prevent shear failures by using steel stirrups. Tests included un-strengthened control beams; the other specimens were strengthened with different strengthening schemes using externally epoxy-bonded carbon fiber reinforced polymer (CFRP) sheets. Discontinuous transverse wrapping was provided in order to prevent premature debonding of the FRP flexural sheets on tension sides.
The key-issue of a possible loss in ductility due to the presence of FRP, that may take to failure before a sufficient amount of moment redistribution was monitored.
The experimental results show that it is possible to achieve a sufficient grade of redistribution if the strengthening configuration is properly chosen, confirming the expected results provided by two simple numerical models
Analysis and Seismic Retrofit of Historical Masonry Buildings under Earthquake Loading: a Case Study
No full textHistorical masonry buildings generally show a high level of vulnerability to seismic actions, due to different reasons, as the lack of effective connections between structural elements, the absence of rigid planes, the dimensions and specific arrangements of masonry panels and the mechanical properties of masonry itself. The need of retrofitting to achieve adequate levels of safety on the basis of the more recent design approaches guarantying at the same time the architectural preservation is a difficult task. In this study a historical masonry structure, located in the South of Italy (Lecce), has been analysed in terms of vulnerability evaluation to seismic actions and possible retrofitting solutions. The case study presented aims to contribute to the complex problems of seismic retrofitting approach of masonry structures. The degree of seismic vulnerability of the structure under examination was evaluated on the basis of different numerical analyses, once the structural modelling was defined. A finite element method was adopted for a linear dynamic 3D analysis and an non-linear 3D pushover analysis. In particular the push-over approach allowed to evaluate the non linear capacity of the structure, the obtained results were compared with codes provisions as regard the “q”
factor indications. The analysis of more suitable and opportune seismic retrofit actions have been performed with the support of Italian CNR recommendations, and on the basis of some experimental results. In particular strengthening techniques using FRP materials have been proposed
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
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