1,720,982 research outputs found
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
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
Vibration Tests and Structural Identification of the Bell Tower of Palermo Cathedral
Full text linkBackground: The recent seismic events in Italy have underlined once more the need for seismic prevention for historic constructions of architectural interest and in general, the building heritage. During the above-mentioned earthquakes, different masonry monumental buildings have been lost due to the intrinsic vulnerability and ageing that reduced the structural member strength. This has made the community understand more that prevention is a necessary choice for the protection of monuments. Objective: The paper aims at demonstrating a strategy of investigation providing the possibility of health judgment, identifying a computational model for the assessment of structural capacity under service and exceptional loading like/due to high-intensity earthquakes. Considering its cost, the proposed approach is applicable only for monumental buildings. In detail, activity regarding the Bell Tower of the Palermo Cathedral is described. This investigation is framed in a huge campaign aimed at assessing the health of monuments in Palermo and their capacity to resist expected seismic actions. Methods: The process of the dynamic identification of the Bell Tower of Palermo Cathedral is discussed starting from the measurement of the response by high sensitivity seismometers and the analysis of the response signals. Then, the formulation of a Finite Element (FE) model of the tower is proposed after the identification of the main modal shapes. Once the Finite Element (FE) model was assessed, it was possible to evaluate the Bell Tower safety level in service and faced with exceptional loads. Results: The structural signals recorded along the height of the tower were analyzed to recognize the variation of the frequency content varying the external environmental loads. The signals were processed to obtain the experimental modal shapes. An FE model was defined whose mechanical parameters were successfully calibrated to give the experimental modal shapes. Conclusion: The analysis of the response signals made it possible to identify the actual behavior of the structure and its compatibility with the service loads. Further, an effective structural model of the Bell Tower of Palermo Cathedral was possible for assessing its capacity level
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
Simplified equivalent finite element modelling of concrete-filled steel tubular K-joints with and without studs
No full textConcrete Filled Steel Tubular (CFST) K-joints employed for truss structures gained high interest in the last years due to their widespread use in engineering practice. The overall performances of these joints can be efficiently improved by using steel studs welded in the inner surface of the steel chord filled with the concrete, avoiding punching shear failure, and improving the overall strength and ductility. However, a reliable prediction of the structural behavior of the joints is outmost of importance for the assessment of the capacity of new and existing structures, and there are no standardized design methods nowadays. In this paper, the structural performances of CFST K-joints with and without steel studs are investigated by Finite Element Modelling (FEM) approach with the aim to provide a predictive tool for the design. A comprehensive discussion of the key parameters that govern the FEM procedure as well as the calibration of the FE models was provided to give the basis for a reliable modelling of CFST K-joints with and without studs for the predictions of the load–displacement/strain response and the strength, considering the main failure mechanisms. In this context, in addition to the detailed FEM of CFST K-joints with steel studs, a simplified equivalent FEM approach is proposed to reduce computational effort keeping the same accuracy
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