1,720,961 research outputs found
Post‐tension retrofitting of RC dapped‐end beams: A numerical investigation
No full textDapped-end beams are frequently used in roofing and flooring systems of precast
reinforced concrete buildings as well as in bridge constructions. Due to
design flaws, deterioration, and construction mistakes, they may have unsatisfactory
structural performance. Past experimental studies investigated the
effectiveness of post-tension strengthening techniques applied to dapped-end
beams, revealing them as effective solutions, even though a limited range of
influencing parameters were considered. This paper numerically investigates
the performance improvement provided by post-tension interventions applied
to dapped-end beams. Numerical models were built through a refined FEM
software simulating two experimental tests found in the literature. After the
models' calibration, a post-tension intervention was designed and implemented
in the models, considering the level of prestressing as the main intervention's
parameter. Afterwards, the behavior in the post-intervention condition
was analyzed to find changes in the failure modes and highlight the performance
improvement concerning cracking phenomena and ultimate loadbearing
capacity. It is found that the level of tendons' prestress significantly
improves the cracking load, which increases almost linearly with respect to
it. Conversely, the significant gain in terms of ultimate load-bearing capacity
(up to 53%) shows only slight variations when the prestress level changes.
Finally, accounting also for the reduction of deformation capacity for high prestressing
levels, practical suggestions are provided regarding the optimal posttension
choice
MODELLAZIONE, ANALISI E OTTIMIZZAZIONE DELLE TECNICHE DI RINFORZO PER L’INCREMENTO DELLA SICUREZZA STRUTTURALE E DELLA RESILIENZA DEI PONTI IN CALCESTRUZZO ARMATO CON SELLE GERBER
Full text linkLe selle Gerber rappresentano elementi critici per la sicurezza strutturale dei ponti in calcestruzzo armato, poiché sono caratterizzate da concentrazioni di fenomeni di degrado e di sforzi che possono comprometterne l'integrità strutturale, causando, nel peggiore dei casi, il collasso dell’intera struttura. Tali criticità sono state sottolineate anche all’interno delle Linee Guida italiane per la classificazione e gestione del rischio, la valutazione della sicurezza e il monitoraggio dei ponti esistenti. La presente tesi di dottorato si propone di approfondire il comportamento strutturale delle selle Gerber, nonché analizzare le diverse tecniche di intervento disponibili, con l'obiettivo di proporre strategie ottimizzate che considerino aspetti strutturali, pratici ed economici, in un’ottica di aumento della sicurezza strutturale e della resilienza delle infrastrutture. La ricerca è stata condotta attraverso un approccio metodologico definito in più fasi. Inizialmente, un'analisi approfondita dello stato dell'arte ha evidenziato le principali criticità delle selle Gerber, illustrando, poi, i principali dettagli costruttivi e i meccanismi di rottura caratteristici, nonché i principali metodi di calcolo per la loro analisi. Successivamente, la costruzione e l'analisi dettagliata di un database di test sperimentali di letteratura hanno permesso di identificare i meccanismi di rottura più frequenti anche in relazione ai dettagli costruttivi presenti. Sulla base dei risultati ottenuti, l'analisi approfondita delle tecniche di intervento ha condotto alla proposta di un percorso logico per l'individuazione delle strategie di intervento ottimali, considerando sia gli aspetti puramente strutturali sia quelli pratici, legati alla applicabilità in opera e all’impatto sull’operatività del ponte. Particolare attenzione è stata dedicata alla tecnica basata sulla post-tensione esterna, risultata efficace dal punto di vista strutturale, economica e poco invasiva. Proponendo un metodo di progettazione dell’intervento, attraverso analisi numeriche non lineari, è stata ottimizzata l'applicazione della post-tensione esterna fornendo indicazioni sull’aumento delle prestazioni strutturali delle selle Gerber in funzione dei livelli di pretensione all’interno dei tiranti esterni. Infine, l'applicazione preliminare di tecniche di Machine Learning per la previsione della resistenza delle selle Gerber, a partire dai dati collezionati all’interno del database di test sperimentali, ha sottolineato le potenzialità di questi metodi per la realizzazione di rapide ed accurate valutazioni di sicurezza strutturale. I risultati offrono una panoramica dettagliata sul comportamento meccanico delle selle Gerber nonché strumenti utili per la pratica ingegneristica, aprendo la strada ad ulteriori ricerche verso l’approfondimento dell’influenza di differenti scenari di degrado sulle prestazioni strutturali delle selle Gerber, sull’utilizzo di configurazioni alternative di rinforzo basate sulla post-tensione, nonché verso ulteriori applicazioni avanzate di intelligenza artificiale nel campo dell'ingegneria strutturale.Gerber saddles represent critical elements for the structural safety of reinforced concrete bridges, as they are characterized by concentrations of both degradation phenomena and stresses that can compromise their structural integrity, potentially leading to the collapse of the entire structure. These criticalities have also been highlighted in the Italian Guidelines for risk classification and management, safety assessment, and monitoring of existing bridges. This doctoral thesis aims to deepen the structural behaviour of Gerber saddles and analyse the various available intervention techniques, to propose optimized strategies that consider structural, practical, and economic aspects, in a perspective of enhancing structural safety and infrastructure resilience. The research was conducted through a methodological approach divided into multiple phases. Initially, an in-depth state-of-the-art analysis highlighted the main critical issues of Gerber saddles, illustrating key construction details, typical failure mechanisms, and the main design methods for their analysis. Subsequently, the creation and detailed analysis of a database of experimental tests from the literature allowed the identification of the most frequent failure mechanisms in relation to the existing construction details. Based on the obtained results, a thorough analysis of strengthening techniques led to the proposal of a logical framework for identifying optimal intervention strategies, considering both purely structural aspects and practical factors related to on-site applicability and the impact on bridge operation. Particular attention was given to the technique based on external post-tensioning, which proved to be structurally effective, cost-efficient, and minimally invasive. By proposing a design method for the intervention through nonlinear numerical analyses, the application of external post-tensioning was optimized, providing guidelines on the enhancement of Gerber saddles' structural performance as a function of the pre-tensioning levels within the external tendons. Finally, the preliminary application of Machine Learning techniques for predicting the resistance of Gerber saddles, based on the data collected in the experimental test database, highlighted the potential of these methods for rapid and accurate structural safety assessments. The results provide a detailed overview of the mechanical behaviour of Gerber saddles as well as useful tools for engineering practice, paving the way for further research on the influence of different degradation scenarios on their structural performance, the use of alternative reinforcement configurations based on post-tensioning, and advanced applications of artificial intelligence in structural engineering
Sustainable Renovation of Public Buildings through Seismic–Energy Upgrading: Methodology and Application to an RC School Building
Full text linkThere are many existing buildings for which seismic rehabilitation interventions are required, especially in earthquake-prone areas like Italy. At the same time, the deep energy crisis that Europe is facing highlights the need for sustainable techniques that are able to increase the energy efficiency of buildings. In order to mitigate the social and cultural obstacles for deep renovations of buildings, effective techniques and methods are required to avoid relocating users, which often discourages such interventions. To this purpose and as the main novelty, this research is aimed at presenting a new strengthening technique for reinforced concrete buildings that is able to integrate structural seismic strengthening and energy efficiency improvements. It is made up of new framed structures connected from the outside to the existing building, thus reducing the intrusiveness and relocation needs of users. At the same time, the seismic strengthening technique is conceived for an optimal coupling with energy saving interventions like high-performance external insulation finishing systems. In this study, these techniques are described and applied to a reinforced concrete (RC) school building designed only for gravity loads, according to outdated standards. The results show that the considered strengthening technique increases the seismic performance of the building with respect to both life safety and damage limitation requirements, avoiding any further local interventions to the building’s interior. On the other hand, the energy renovation allows for significant savings, since the resulting reduction in the total non-renewable energy consumption is larger than 80%
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
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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