1,720,992 research outputs found
Flexural Behavior for External Beam–Column SFRC Joints: Experimental Investigation and Design Suggestions
No full textExperimental research was carried out on the flexural behavior of full-scale external beam–column concrete joints cast with plain and steel fibrous reinforced concrete (SFRC) with hooked steel fibers, subjected to cyclic reversal loading. Four beam–column sub-assemblages were cast. Two of them, denoted as control specimens, were made of plain concrete (RC) and were reinforced with longitudinal bars and transverse stirrups, and two were made of hooked steel fiber-reinforced concrete (SFRC) with same longitudinal steel reinforcements of control specimens but with higher spacing of stirrups in the beam. The experimental results show that it is possible to avoid brittle failure of external beam to column joint assigning, as it is well-known, high percentage of transverse steel in joint region or utilizing less stirrups in all critical regions and replacing plain concrete with SFRC. In this case, it is possible also a more efficient control in the opening of the cracks. From the analytical point of view, experimental results were reproduced numerically by using a non-linear finite-element program (ABAQUS). With ABAQUS constitutive laws in compression and in tension able to include post-cracking resistance of material were adopted. In addition, utilizing a simplified closed-form softened strut-and-tie macro-model, it was possible reproduce the load-deflection curves of beam to column sub-assemblages. Analytical results were in a good agreement with monotonic response observed experimentally. Finally, design guides for ductile behavior of SFRC beam to column joints are give
Steel jacketing of RC columns: Reliability of capacity laws for concrete
No full textIn the seismic assessment of framed R.C. structures reinforced by steel angles and battens (steel jacketing) the use of proper confinement models for concrete is still a main topic. Really, the capacity of reinforced concrete columns under concentric and eccentric loads strongly depends on confinement exerted by the external reinforcement. Further a proper attribution of concrete stress-strain laws allows obtaining reliable estimations of inelastic capacity of reinforced elements. Moreover the presence (or not) of connections of the angles with the end joints influences their capacity to support vertical loads. In the two cases the mechanical models have to account for buckling or frictional effects. In this frame this paper presents a selected review of literature confinement models for steel jacketed concrete elements, presenting a parametric study in which the main confinement parameters predictable by each of them are compared. The reliability of the models in object is finally tested comparing analytical predictions of the ultimate vertical capacity with experimental results coming from several literature compressive tests of reinforced column specimens
Influenza dei Fenomeni Attritivi nella Risposta Strutturale di Colonne in c.a. Rinforzate con Incamiciatura in Acciaio: Confronto numerico-sperimentale e Predizione Analitica della Capacità
No full textL'incamiciatura metallica di pilastri in c.a. mediante angolari e calastrelli (steel jacketing) è una tecnica comunemente adottata, per migliorare la capacità resistente e deformativa di edifici esistenti. Nel caso in cui gli angolari non siano direttamente posti in contatto con le zone nodali (in corrispondenza di travi e solai), la definizione del modello computazionale della sezione trasversale deve essere gestita con cautela poiché differente è il regime di trasferimento degli sforzi che si instaura. Nel caso di applicazione di uno strato intermedio di malta fra acciaio e calcestruzzo, l'effettiva capacità di carico degli angolari è funzione della pressione di laterale confinamento, della la coesione e del coefficiente di attrito fra i materiali. L'attribuzione di tali parametri meccanici non è immediata e la definizione del modello computazionale richiede accorgimenti specifici. Il presente studio è dedicato all'implementazione di un modello numerico per le sezioni in c.a. rinforzate, includente gli effetti dell'interazione attritiva di interfaccia. Il modello è calibrato e validato attraverso il confronto con i risultati di una campagna sperimentale su campioni di colonne rinforzate soggette a compressione e pressoflessione. Sulla base dei risultati viene infine proposta una procedura analitica semplificata per la definizione dei domini di resistenza delle sezioni rinforzate, fornendo i parametri di taratura del legame stress-block per il calcestruz
Mechanical behavior of a total chest wall prosthesis with rib-like features
No full textThe Department of Thoracic Surgery of the National Institute of Cancer in Milan developed a new rib-cage prosthesis which tries to combine flexibility, protection and bio-compatibility. This new replacement concept has been implanted in many patients, showing cheering results in term of reconstructions simplicity, postoperative complications reduction and patients comfort. This paper investigates and discusses in detail the mechanical behavior of the innovative rib cage prosthesis. Mechanical strength and stiffness are numerically evaluated in order to asses its limits and if it is fully compatible with patients ânormalâ life
Optimal design algorithm for seismic retrofitting of RC columns with steel jacketing technique
Full text linkSteel jacketing (SJ) of beams and columns is widely employed as retrofitting technique to provide additional deformation and strength capacity to existing reinforced concrete (RC) frame structures. The latter are many times designed without considering seismic loads, or present inadequate seismic detailing. The use of SJ is generally associated with non-negligible costs depending on the amount of structural work and non-structural manufacturing and materials. Moreover, this kind of intervention results in noticeable downtime for the building. This paper presents a new optimization framework which is aimed at obtaining minimization of retrofitting costs by optimizing the position and the amount of steel jacketing retrofitting. The proposed methodology is applied to the case study of a 3D RC frame realized in OpenSEES and handled within the framework of a genetic algorithm. The algorithm iterates geometric and mechanical parameters configurations, based on the outcomes of static pushover analysis, in order to match the optimal retrofitting solution, intended as the one minimizing the costs and, at the same time, maintaining a specified safety level. Results of the proposed framework will provide optimized location and amount of steel-jacketing reinforcement. It is finally shown that the use of engineering optimization methods can be effectively used to limit retrofitting costs without a substantial modification of structural safety
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
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