1,720,957 research outputs found
Monitoring and Self-diagnosis of Civil Engineering Structures: Classical and Innovative Applications
Full text linkEventi estremi come esplosioni o terremoti possono avere un profondo impatto nella sicurezza degli edifici. Le zone sismiche devono convivere con questi tragici eventi, per questo monitorare in maniera continua le condizioni di salute di una struttura è necessario e auspicabile in molti casi.
Il monitoraggio strutturale (Structural Health Monitoring – SHM) rappresenta un potente strumento per la valutazione del comportamento dinamico della struttura monitorata. Fino a pochi anni fa queste tecniche erano impiegate prevalentemente in ambito meccanico, aeronautico e nell’ingegneria aerospaziale.
Al giorno d’oggi, la riduzione dei costi della strumentazione, sistemi di acquisizione dati di nuova generazione e l’incremento continuo dell’efficienta nelle analisi numeriche hanno reso possibile l’applicazione di queste tecniche anche a strutture civili ordinarie.
Le tecniche di monitoraggio strutturale vengono applicate non solo in grandi infrastrutture come ponti, dighe o grattacieli, ma anche in strutture storiche o edifici residenziali.
In questo contesto questa tesi tenta di esaminare differenti aspetti del monitoraggio strutturale, in particolar modo riferite a edifici ordinari.
Attraverso tecniche Output-Only (Operational Modal Analysis – OMA) sono state monitorate diverse strutture civili con reti di sensori cablate, al fine di ottenere il comportamento dinamico strutturale nelle reali condizioni operative.
Particolare attenzione è stata focalizzata in un altra importante tematica dell’ingegneria strutturale: il danneggiamento strutturale. Attraverso un approccio numerico viene presentato un nuovo metodo per la localizzazione e quantificazione del danno a seguito di un evento sismico.
In alternativa alla classica rete cablata, è stato sviluppato un sistema di acquisizione con sensori wireless (Wireless Sensor Network – WSN). I principali risultati ottenuti con questa applicazione vengono riportati nella presente tesi, unitamente al design dei sensori low-cost. Con l’ausilio della sensoristica sviluppata è stato monitorato un edificio storico in muratura, mostrando i risultati positivi ottenuti a seguito della campagna di acquisizione di rumore ambientale (Ambient Vibration Survey -AVS)
TECNICHE DI IDENTIFICAZIONE MODALE PER L’ANALISI STRUTTURALE. L’evoluzione del comportamento dinamico di un edificio scolastico in cemento armato soggetto a miglioramento sismico
No full textThis work deals with the structural retrofitting of a Reinforced Concrete (RC) building school and illustrates the results of a structural monitoring campaign performed on this. The examined school building presents typical and specific vulnerabilities of Italian building stock - of which RC buildings currently represent the greatest portion - mostly built in 60’s and 70’s Because of its vulnerabilities, the structure was subjected to a deep structural retrofitting intervention based on increasing of original columns cross-sections with introduction of new longitudinal steel bars and stirrups, and application of shear reinforcement on beams using Fiber Reinforced Polymers (FRP). The building was monitored using Operational Modal Analysis (OMA) technique, that offers the possibility of describing structural dynamics at small vibration amplitudes in real operating conditions with unknown excitation inputs. The long-term Ambient Vibration Survey (AVS) - performed before, during and after the works, in a campaign lasted one year - highlighted the increasing of building performance in terms of natural frequencies following the retrofitting works. Moreover, the paper shows how infill panels influence the dynamic response of this typical RC structure. This relevant data collection, in addition to confirm the potentil of OMA technique in gathering the real structure behavoiur, could be very helpful in the calibration of other similar retrofitting interventions
Tracking modal parameters evolution of a school building during retrofitting works
No full textDuring a seismic improvement intervention that lasted more than one year, a reinforced concrete (RC) school building had been surveyed through dynamic monitoring, granting continuous updates on its global response. Operational Modal Analysis (OMA) was carried out to have a proper understanding of the structure’s dynamic evolution, using a Finite Element Model (FEM) to perform a non-invasive and quantitative structural assessment taking into account the interactions with the surroundings.
During the whole restoration works, the long-term (periodic) monitoring campaign showed the increment of the building performance remarked by the variation of natural frequencies. Also, the experimental assessment of the influence of infill masonry panels on the dynamics of RC frame is shown at each upgraded configuration. Additional restoration works, that may eventually occur, could benefit from the data collected during the present Ambient Vibration Survey (AVS), providing useful parameters to enhance the retrofitting and the dynamic behavior of the structure
Integrated survey approaches for monitoring procedures during yard phases
Full text link[EN] Buildings, construction sites and civil structures need an accurate, continuous, and real time monitoring system. This necessity arises to detect dangerous situations for the structures and any occupant, especially during natural or anthropogenic events such as earthquakes or delicate phases of invasive operations such as excavations for piling. During these situations, the static and dynamic conditions of a structure and everything related to it could be impaired. The analysis and evaluation of significant displacements and deformation parameters, which are fundamental for structural controls and health monitoring, can be approached following different exchangeable procedures. Among the non-destructive monitoring techniques used in recent years, such as in this research, wireless sensors, are having a remarkable development in detecting anomalies. The acquisition of significant deformation parameters is obtained starting from the traditional topographic survey by total station and using static and dynamic sensors. Monitoring equipment concerns three-axial wireless tiltmeters which allow to measure accurately any angle of inclination in the points where they are installed in order to monitor kinematic movements during yard phases. The main purpose of this experiment is to compare data collected by tiltmeters with those obtained by the robotic total station. Three-axial accelerometers are also installed to obtain the acceleration value of the different reference points. By processing the collected data, it is proved that the final results are comparable, despite using different and completely independent monitoring systems. These integrated survey approaches demonstrate the effectiveness and efficiency of designing a monitoring system based on sensors that are installed to observe changing phenomena over the time, especially during delicate phases of invasive operations, which may represent a more widespread low-cost and reliable solution.Rahali, A.; Malinverni, E.; Pierdicca, R.; Pierdicca, A.; Potenza, G.; Lucesoli, M. (2023). Integrated survey approaches for monitoring procedures during yard phases. En 5th Joint International Symposium on Deformation Monitoring (JISDM 2022). Editorial Universitat Politècnica de València. 121-128. https://doi.org/10.4995/JISDM2022.2022.13753OCS12112
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
Structural health monitoring applications with wireless sensors on an historical masonry building
No full textIn the last decades, the need for an effective seismic protection and vulnerability reduction of cultural heritage buildings and sites determined a growing interest in Structural Health Monitoring (SHM) as a knowledge-based assessment tool to quantify and reduce uncertainties regarding their structural performance. Monitoring can be successfully implemented in some cases as an alternative to interventions or to control the medium- and long-term effectiveness of already applied strengthening solutions.
Traditional monitoring systems are composed of grids of sensors distributed along the structure to be monitored and connected to a central acquisition and processing unit through cables, and then post-processed in order to determine structure’s condition and assess a safety level. Recently, the use of wireless sensor networks (WSN) as an alternative base infrastructure for structural monitoring systems has been explored. A wireless sensor network is usually a more flexible solution (in facts, it does not require any cable deployment if the nodes are battery powered) with minor costs associated especially if the network is composed by low cost devices (e.g., MEMS sensors). Respect to a wired solution, new problems should however be considered: the synchronization between sensor nodes, the short transmission distance, the optimization of energy consumption and the selection of adequate low-cost sensors.
In this framework, this work details the main results obtained in the context of the “Palazzo Comunale of Castelfidardo” monitoring project with WSN, with the aim to get an accurate numerical model that simulates the dynamic behaviour of the whole structure.
A comparison between the structural responses obtained from the preliminary and an updated numerical model is proposed
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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