Dissertations / Theses on the topic 'Settore costruzioni'
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Barducci, Federica. "3D printing: l’evoluzione della tecnologia nel settore costruzioni." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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L’architettura nei suoi svariati settori di studio è sempre stata strettamente influenzata dalle innovazioni tecnologiche che ogni periodo storico ha presentato. All'inizio degli anni Ottanta questo sviluppo ha portato un salto da un approccio “analogico” ad approccio “digitale”.
La modellazione tridimensionale ha conquistato una posizione importante nel mondo dell’architettura, sia come sostegno nella progettazione e produzione di edifici ex-novo che nel supporto per l’analisi e gestione dei manufatti esistenti.
Lo sviluppo della modellazione tridimensionale ha trainato con se lo sviluppo di software dedicati, strumentazioni tecnologiche e tecnologie innovative sempre più accurate.
Solo recentemente è stato compiuto un cambio di direzione, un’evoluzione tale da permetterci la materializzazione, per di più rapida, dei modelli che prima erano solo visualizzabili tramite uno schermo di un computer.
La materializzazione rapida di tali modelli è nata con la comparsa delle prime tecniche di stampa tridimensionale o stampa 3D, tecnologia che sta riscuotendo un enorme successo e di conseguenza un notevole sviluppo in numerosi settori e discipline scientifiche, non solo nell’ambito dell’architettura.
Questa tecnologia permette di modificare il paradigma produttivo fornendo vantaggi significativi come la diminuzione degli sprechi, la produzione di oggetti unici a costi molto inferiori rispetto ai metodi tradizionali e la possibilità di produrre oggetti con geometrie interne precedentemente impossibili da realizzare.
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Rossi, Filippo. "Il controllo di gestione di commessa nel settore delle costruzioni." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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L'obiettivo dell'elaborato è quello di analizzare le tematiche inerenti il controllo di gestione di commessa realizzato all'interno di realtà che operano nel settore delle costruzioni con focus sulle opere civili.
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Pagano, Nicola. "Innovazione e produttività nel settore delle costruzioni: applicazione dell'approccio Lean Construction." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
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Negli ultimi decenni il settore dell’edilizia è stato oggetto di una attenta fase di riesame che si è posta l’obiettivo di ottimizzare il processo di costruzione, minimizzando le risorse necessarie e, di conseguenza, massimizzando il profitto. La metodologia tradizionale risulta inefficacie ed inefficiente, diversi studi di settore riportano che la produttività delle costruzioni è fortemente ridotta se paragonata a quella di altri settori.
A partire dagli anni ’90, la diffusione nel settore edilizio della filosofia Lean ha cercato di innovare la pratica tradizionale consistente nella mera conversione di un input in un output. L’introduzione di concetti come flusso e valore permette sia una visione d’insieme che la considerazione di tutti i fattori impattanti sul processo edilizio.
La studio qui presente consiste nell’analisi e nell’applicazione della metodologia Takt time, pratica di Lean Management, alla ristrutturazione di un edificio residenziale costituito da otto unità immobiliari risalente alla fine degli anni ’60. L’intervento si inserisce nell’ambito delle recenti iniziative di agevolazione fiscale per la riqualificazione del patrimonio edilizio nazionale. Lo strumento presentato, derivante dal settore industriale, propone una differente organizzazione dell’attività lavorativa. Esso si basa sull’individuazione di singole aree nelle quali le attività vengono raggruppate in pacchetti di lavorazioni di uguale durata, la definizione di tale valore limite, definito proprio come tempo di takt, rappresenta la scelta progettuale principale. Attraverso la variazione delle aree, delle lavorazioni e della manodopera per esse necessaria si ha il rispetto del parametro di progetto prescelto. Infine, il cronoprogramma dei lavori, risultante dalla simulazione di applicazione della metodologia, è stato valutato e confrontato rispetto alla pratica tradizionale.
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Deppieri, Gaia <1997>. "REVERSE CHARGE E SPLIT PAYMENT: L’IMPATTO SULLA FINANZA DEL SETTORE DELLE COSTRUZIONI." Master's Degree Thesis, Università Ca' Foscari Venezia, 2021. http://hdl.handle.net/10579/19768.
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Nel 2020 la Commissione Europea ha concesso all’Italia la proroga dello Split Payment fino al 30 giugno 2023. Tale istituto, così come quello del Reverse Charge, nei casi in cui è applicabile, prevede che l’Imposta sul Valore Aggiunto non sia dovuta dal soggetto che effettua la cessione di un bene o la prestazione di un servizio, ma dal soggetto che la riceve. Reverse Charge e Split Payment sono due istituti nati al fine di ridurre l’evasione fiscale, che, però, comportano anche effetti sulla finanza delle aziende a cui sono destinati.
L’elaborato tratterà di questi due istituti, soprattutto in relazione al settore delle costruzioni, da essi interessato. Innanzitutto, se ne esaminerà la disciplina e si farà una panoramica di tale settore, per poi concentrarsi sull’effetto che tali istituti hanno sulla sfera finanziaria delle imprese, andando anche a svolgere un’analisi di tipo quantitativo con l’obiettivo di indagare e valutare effettivamente l’impatto di tali fenomeni sulle imprese appartenenti al settore delle costruzioni.
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Gastaldello, Davide. "Spazi confinati: una proposta metodologica per l'assoggettabilita' e l'applicazione al settore delle costruzioni." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6796/.
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La presente Tesi di Laurea non solo propone una soluzione innovativa ai fini di garantire una corretta definizione e procedura di lavoro all'interno di spazi confinati, ma fornisce anche una metodologia di identificazione, analisi e valutazione dei rischi specifici, e correlate misure di protezione e prevenzione, unica ed originale.
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De, Marco Domenica. "L'importanza della classificazione merceologica nell'ambito industriale:studio di un caso applicativo nel settore delle costruzioni meccaniche." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amslaurea.unibo.it/984/.
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TORRE, STEFANO. "Experimental tests and full-scale monitoring of the wind effects on moored ships." Doctoral thesis, Università degli studi di Genova, 2022. https://hdl.handle.net/11567/1097556.
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The recent growth of cruise and container ships size, which is involving the shipping industry, determines the greater and greater importance of evaluating properly the wind actions on such big ships, especially during the mooring. Accidents and damages may occur in port areas during extreme wind events due to the breakage of mooring clamps, jeopardizing the safety of human beings and vessels as well as producing significant economic losses.
In order to better highlight the possible reasons of such events, a research PhD project has been developed in collaboration between Civil, Chemical and Environmental Engineering Department (DICCA) and PSA Genova Prà, Cetena S.p.A. (Fincantieri Group) and “Gruppo Antichi Ormeggiatori del Porto di Genova” and it has funded by Regione Liguria under the Operational Program Liguria Region - European Social Fund 2014-2020, ASSE 3 "Education and training". The research has been developed through an intensive wind tunnel tests campaign, in order to verify the requirements of best industry practices for the wind loads assessment also for a new generation of giant ships, and field measurements in the area port finalized, to measure the real conditions affecting the moored ships in term of wind conditions, mooring loads, and displacements. In particular, an innovative monitoring system for the ship motion detection, completely designed and realized during this research, will be described in the manuscript.
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Di, Toro Mammarella Fabio. "Valutazione della propensione all'automazione e robotizzazione del settore delle costruzioni: un caso di studio di edilizia specialistica." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23372/.
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Il settore delle costruzioni è caratterizzato da tempo da una bassa produttività, le cui cause sono da ricercarsi nelle caratteristiche e nell’approccio attuale. Domanda ciclica, lavoro a prevalenza manuale, modesti investimenti in ricerca e sviluppo, frammentazione del mercato e bassi margini di guadagno a fronte di rischi elevati, sono solo alcune delle cause che descrivono la situazione odierna. Gli studi di settore consultati concordano sulla necessità di un cambio radicale nel modo di concepire la costruzione attraverso l’adozione di tecnologie avanzate nel campo della robotica. In quest’ottica diventa fondamentale l’adozione di conseguenti strategie progettuali che mirano al co-adattamento tra processo e prodotto, come il Robot-oriented design. L’obbiettivo del lavoro di tesi di laurea è quello di valutare l’attuale distanza tra la costruzione tradizionale e le costruzioni basate sull’Automation in Construction tramite l’analisi di un caso studio di edilizia specialistica. Nel caso studio preso in esame si propone una metodologia di valutazione volta a stimare la propensione dei diversi processi di costruzione ad essere automatizzati e la cantierizzazione di soluzioni tecnologiche evolute presenti ad oggi sul mercato. La prospettiva è quella di aumentare produttività, qualità e sicurezza all’interno del cantiere, nel più ambizioso obbiettivo di ottimizzazione dell’intero settore. I risultati discussi nel corso della trattazione si inseriscono nel vivace dibattito sul futuro delle costruzioni e incentivano una riflessione profonda sul modo di concepire il processo costruttivo.
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GARBERI, ROBERTO CARLO. "STORIA DELLA COSTRUZIONI AERONAUTICHE GIOVANNI AGUSTA. IMPRESA, TECNOLOGIE E ORGANIZZAZIONE 1908-1975." Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/172632.
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A company history of the italian helicopter's manufacturer site in Cascina Costa of Samarate - Varese. The study covers a period that runs from the first prototype built by Giovanni Agusta until the middle of 70's when many different changes involved the technology, owner's asset and the structure of the company. All the aspects connected with the acquired licences from North American manufacturers are in details analyzed and the governance of the company too. In the background has been also analyzed the evolution of rotorcraft machines in Italy with a brief history of their technology. The study takes care also of the local factors that involved the conducts of the company.
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MICHELI, Maria Silvia. "Composizione italiana in diacronia. Le parole composte dell'italiano nel quadro della Morfologia delle Costruzioni." Doctoral thesis, Università degli studi di Bergamo, 2019. http://hdl.handle.net/10446/128637.
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This thesis provides a diachronic analysis of Italian compounding within the framework of Construction Morphology. On the basis of data extracted from both synchronic and diachronic corpora, it outlines an overview of Italian compound words and sheds light on their development from the Origins to the present age.
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BRESSANELLI, Michele Egidio (ORCID:0000-0002-6582-6845). "Sistemi strutturali ricentranti per strutture resilienti al sisma: rocking walls e rocking columns." Doctoral thesis, Università degli studi di Bergamo, 2022. http://hdl.handle.net/10446/227576.
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Nella progettazione antisismica si tende a realizzare costruzioni resilienti in grado di incassare danni progressivamente più consistenti al crescere dell’intensità sismica, conservando in ogni caso una ragionevole distanza dal collasso strutturale. Perché ciò sia possibile è necessario che le strutture siano in grado di mantenere un comportamento stabile in campo inelastico. Un metodo per ottenere edifici resilienti è l’utilizzo di sistemi ricentranti ottenuti con l’inserimento di cavi post-tesi non aderenti all’interno di elementi strutturali. Tali sistemi sono noti con il termine di rocking systems e possono essere affiancati a dispositivi isteretici e/o viscosi per aumentare la dissipazione energetica. Queste tipologie strutturali sono molto vantaggiose perché caratterizzate da un basso livello di danno e da un’elevata operatività post-sisma.
L’obiettivo della ricerca è lo sviluppo di metodi di progettazione e analisi per sistemi ricentranti con l’obiettivo di rendere il patrimonio edilizio più sostenibile, sicuro e resiliente. Lo studio si focalizza sulla definizione di criteri di progetto per la definizione dei dissipatori e dei cavi post-tesi dei sistemi ibridi e sullo studio della modellazione di tali sistemi al fine di promuoverne maggiormente l’utilizzo. La progettazione sismica è condotta sfruttando il metodo displacement-based design proposto da Priestley. Tale approccio è stato esteso al progetto di sistemi multi-rocking e nel caso di elementi dissipativi di tipo viscoso in alternativa a quelli di tipo isteretico, grazie allo sviluppo di una procedura specifica.
A livello di modellazione, sono state sviluppate e confrontate varie soluzioni i cui risultati analitici sono stati validati con quanto ottenuto da test sperimentali: nello specifico dal progetto di ricerca DSDM svoltosi nel 2008 presso l’Università della California a San Diego riguardante i test su tavola vibrante di un edificio prefabbricato di tre piani in scala 1:2 con setti rocking e dal progetto di ricerca riguardante una pila da ponte ricentrante testata presso il laboratorio dell’Università della California a Berkeley e oggetto del 2017 PEER Blind Prediction Contest. È stata inoltre analizzata l’influenza dei picchi di accelerazioni orizzontale e verticale, originati dall’apertura e dalla chiusura del gap all’interfaccia parete-fondazione, oltre che le risposte locali e globali, rispettivamente della singola parete e dell’intera struttura oggetto di studio. I risultati ottenuti a seguito della modellazione, confrontati con quanto ottenuto sperimentalmente, hanno permesso di definire dei parametri ottimali da utilizzare durante la modellazione di tali sistemi. Nello specifico, l’inserimento di un elemento dissipativo alla base ha consentito di eliminare parte dei disturbi sulle accelerazioni orizzontali riscontrati durante le fasi di apertura e chiusura del gap alla base e mitigare l’effetto delle vibrazioni ad alta frequenza dovute agli impatti. Sono state sviluppate tre differenti tipologie di modellazione: con elementi a fibre, con molla rotazionale alla base e con molle traslazionali reagenti solo a compressione nell’interfaccia parete-fondazione. Ciascuna modellazione è stata effettuata sia su modelli semplificati sia su modelli più complessi.In the anti-seismic design there is a tendency to realize resilient constructions able to take progressively greater damage as the seismic intensity increases, preserving in any case a reasonable distance from structural collapse. For this to be possible it is necessary that the structures are able to maintain a stable behaviour in the inelastic field. One method of achieving resilient buildings is the use of re-centring systems obtained by inserting unbounded post-tensioned cables within the lateral force resisting system structural elements. These systems are known as rocking systems and can be coupled with hysteretic and/or viscous devices to increase energy dissipation. These structural types are very advantageous because they are characterized by a low level of damage and high post-earthquake operability. The objective of the research is to develop design strategies and analysis methods for re-centring systems. The study is focused on the definition of design criteria for dissipators and post-tensioned cables of hybrid systems and on the study of the modelling of such systems in order to further promote their use. The seismic design is conducted by exploiting the displacement-based design procedure proposed by Priestley. This approach has been extended to the design of multi-rocking systems and in the case of viscous dampers as an alternative to hysteretic devices. At the modelling level, various solutions have been investigated and compared with the results obtained from experimental tests: specifically from the DSDM research project carried out in 2008 at the University of California at San Diego concerning the shake table tests of a three-story 1:2 scale precast building with rocking and hybrid walls and from the research project of a re-centring bridge pier tested at the laboratory of the University of California at Berkeley and object of the 2017 PEER Blind Prediction Contest. The influence of horizontal and vertical accelerations spikes originating from gap opening and closing at the wall-foundation interface was also analysed, as well as the local and global responses of the individual wall and of the entire structure under study, respectively. The results allowed to define the optimal parameters to be used during the modelling of such systems. Specifically, the insertion of a dissipative element at the base has made it possible to eliminate part of the disturbances on the horizontal accelerations found during the opening and closing phases of the gap at the base and to mitigate the effect of high frequency vibrations due to impacts. Three different types of modelling strategies were developed: with fiber elements, with lumped rotational springs at the base and with distribute compression-only translational springs at the wall-foundation interface. Each modelling strategy was performed on both simplified and more complex models.
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ARIZZI, Fabio. "Integrated Experimental and Modelling Approach for the Characterization of Thermo-Tribological Phenomena in Hot Rolling Processes." Doctoral thesis, Università degli studi di Bergamo, 2015. http://hdl.handle.net/10446/72271.
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RAVIZZA, Gabriele. "Modal dynamic identification of civil structures via inverse analysis based on Heterogeneous Data Fusion and post-processing." Doctoral thesis, Università degli studi di Bergamo, 2021. http://hdl.handle.net/10446/183099.
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The present Doctoral Thesis belongs to the Scientific-Disciplinary Sector of Mechanics of Solids and Structures (ICAR/08 - Scienza delle Costruzioni), and falls within the broader research field of Structural Health Monitoring (SHM), with specific reference to the civil engineering context.
Nowadays, SHM-based approaches and the attached development of consistent numerical modeling, with related model updating, may constitute fundamental tools to pursue the goal of engineering structural safety, preventing possible causes of damage that may even lead to structural failure.
In particular, this research work proposes complementary post-processing approaches to address the issue of noise cleaning on dynamic structural response signals typically encountered in structural engineering applications (specifically, acceleration and displacement signals). Two approaches are mainly presented, especially aiming at enhancing displacements response signals, since they are commonly affected by higher levels of noise, also due to the low-cost monitoring instrumentation that may possibly be employed. Heterogeneous Data Fusion (HDF) procedures, which involve a Kalman Filter (KF)-based implementation, are primarily investigated, by integrating data acquired from different types of sensors, so that the resulting information turns out to be characterized by a lower degree of uncertainty. A denoising approach is also inspected, as the process through which a source signal may be reconstructed, starting from a recorded, noise-affected one, by removing its noisy part, without losing the useful information incorporated within it.
A HDF procedure and a denoising approach are then combined within an integrated strategy, in an effort to enhance the reliability of the monitoring process, for assessing the health conditions of bridges.
Aspiring at providing a comprehensive research framework on these topics, both synthetic response signals and real response signals are considered, as well as signals displaying a different nature (non-stationary vs. stationary). These processed response signals are finally employed toward modal identification purposes, for extracting the modal properties of the monitored structure.The present Doctoral Thesis belongs to the Scientific-Disciplinary Sector of Mechanics of Solids and Structures (ICAR/08 - Scienza delle Costruzioni), and falls within the broader research field of Structural Health Monitoring (SHM), with specific reference to the civil engineering context. Nowadays, SHM-based approaches and the attached development of consistent numerical modeling, with related model updating, may constitute fundamental tools to pursue the goal of engineering structural safety, preventing possible causes of damage that may even lead to structural failure. In particular, this research work proposes complementary post-processing approaches to address the issue of noise cleaning on dynamic structural response signals typically encountered in structural engineering applications (specifically, acceleration and displacement signals). Two approaches are mainly presented, especially aiming at enhancing displacements response signals, since they are commonly affected by higher levels of noise, also due to the low-cost monitoring instrumentation that may possibly be employed. Heterogeneous Data Fusion (HDF) procedures, which involve a Kalman Filter (KF)-based implementation, are primarily investigated, by integrating data acquired from different types of sensors, so that the resulting information turns out to be characterized by a lower degree of uncertainty. A denoising approach is also inspected, as the process through which a source signal may be reconstructed, starting from a recorded, noise-affected one, by removing its noisy part, without losing the useful information incorporated within it. A HDF procedure and a denoising approach are then combined within an integrated strategy, in an effort to enhance the reliability of the monitoring process, for assessing the health conditions of bridges. Aspiring at providing a comprehensive research framework on these topics, both synthetic response signals and real response signals are considered, as well as signals displaying a different nature (non-stationary vs. stationary). These processed response signals are finally employed toward modal identification purposes, for extracting the modal properties of the monitored structure.
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Capanna, Ilaria. "Simplified multicriteria method for seismic assessment of unreinforced masonry buildings." Doctoral thesis, Università degli Studi dell'Aquila, 2022. https://hdl.handle.net/11697/198067.
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The aims and motivations that were driven this PhD thesis arise from the common interest on the mitigation of the seismic risk, wide field of continuous relevance and of interest for different disciplines. The scientific community, specially in engineering field, reserves attentions on the mitigation of the seismic risk. The human and economic losses, caused by fragilities of the urban centres, manifested in the aftermath of a seismic event, confirm the need of research effort. The PhD thesis presents a multi criteria method for seismic assessment of unreinforced masonry buildings, URMs. The majority of the built environment consists of URMs. The study of their seismic behaviour is exasperated by the ageing of materials, the lack of anti-seismic criteria, construction process, architectural alterations or restorations, and the poor mechanical properties of used materials. Nevertheless, URMs are unique constructions for their historical and architectural value, that need to be protected against earthquakes. The knowledge of structural fragilities of urban centres is a prerequisite to face the mitigation of the seismic risk. Simplified assessment methods arise to overcome the effort and time consuming of analysis at a large scale of the built environment, by means the introduction of several simplifications.
The proposed multi criteria vulnerability method provides a quick assessment based on few structural parameters, known from field observations and geometric survey, to overcome excessive computational demand, thanks to two different levels of evaluation. The first level of the vulnerability assessment method bases on the evaluation of few structural parameters to perform a first screening of the seismic fragilities. The second level predicts the seismic capacity of masonry walls more accurately respect to the empirical one, to establish strengthening measures or strategies more accurately. Therefore, the multi criteria method could support the activities of authorities and stakeholders in the mitigation of the seismic risk of the built environment. The thesis consists of eight chapters. The first chapter introduces an overview on the seismic risk, as field of the research activity. The second chapter concerns the state of the art of structural vulnerability, the structural vulnerability. An in-depth classification of seismic vulnerability assessment methods is reported. The third chapter regards the test-site of the research activity. The fourth chapter reports the dynamic campaign on a URM, chosen as representative of the structural class. The aim of this activity was to investigate the influence of a suite of structural parameters influencing the building behaviour. The fifth chapter introduces the first level of the predictive multi-criteria method. The empirical method aims to estimate the seismic vulnerability through the evaluation of a few structural parameters, ensuring a quick application. The derivation and validation of the formulations' method are reported. The last part of the chapter compares the method with others available from the literature, to highlight its reliability and advantages. The sixth chapter illustrates possible applications of the empirical predictive method. The seventh chapter discusses the second level of the proposed method. It aims to grasp the seismic vulnerability of buildings, with a higher accuracy than the first level. The eighth chapter completes the PhD thesis, with a broader point of view, to explain the results and future developments.
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Cirella, Riccardo. "The use of subspace-based methods for damage detection in civili structures: a machine learning approach." Doctoral thesis, Università degli Studi dell'Aquila, 2022. https://hdl.handle.net/11697/198068.
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Events in recent years have shown how important it is to monitor the structural health of existing civil works. Structural Health Monitoring systems are a useful tool to provide an objective and automatic valuation of the state of health of a structure, in order to detect the emergence of anomalies in its behavior. They are also an auxiliary tool in the decision-making phase for maintenance work or after extraordinary events. The Thesis work explores the topic of damage detection based on the analysis of subspaces of dynamical systems matrices. The aim of the research was to investigate a method for the development of levels in the damage diagnosis scale, ranging from the identification of the anomaly to the localization and subsequent assessment of the entity of the damage occurred. The study is carried out following two approaches: in the first, damage indices present in the literature are considered, and a newly developed one is presented. In the second approach, the identification issue is addressed by introducing the most recent Machine Learning tools: the goals are achieved through the supervised training of a classifier, with the task of localizing and quantifying the damage. In both cases, the methods used are model-driven type, based on simulations of the damage scenarios through Finite Element modeling. The thesis work therefore aimed to evaluate the effectiveness of the same subspace- based indices as objective functions in the optimization process related to the model updating process of the FE model, such that the simulated response in subsequent analyses would be as close as possible to the real one. The findings of the tests, both numerical and experimental, confirm the effectiveness of both proposed methods, highlighting their shortcomings and strengths. The concepts developed were subsequently applied to a case study, represented by the Basilica of Santa Maria di Collemaggio, in L'Aquila. In the first stage, the dynamic behavior of the Basilica was investigated, over the years of monitoring. Subsequently, traditional and Machine Learning algorithms have been implemented for the purpose of anomaly detection: the procedure has been performed considering as damaged a case, one produced after a structural intervention subsequent to the installation of the monitoring system. The studies on the Basilica showed a complex dynamic behavior, strongly influenced by environmental factors: nevertheless, the implemented algorithms proved to be effective for the defined purpose.
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PAGLIARO, STEFANO. "MODELLI E ANALISI DI SISTEMI ACCOPPIATI PER IL MIGLIORAMENTO DINAMICO E SISMICO DI STRUTTURE INTELAIATE." Doctoral thesis, Università degli Studi dell'Aquila, 2022. http://hdl.handle.net/11697/192061.
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La presente tesi studia l’uso di sistemi accoppiati per migliorare il comportamento dinamico e sismico di strutture intelaiate. La tesi è divisa in quattro capitoli.
Il primo capitolo contiene un introduzione alla tesi. Esso mostra la letteratura classica dei sistemi studiati nella tesi, quali il Tuned Mass Damper, l’isolamento alla base, il blocco rigido e i dispositivi inerter.
Il secondo capitolo studia la discontinuità intermedia, spesso chiamato anche isolamento a piani intermedi. La discontinuità divide l’edificio in due componenti, la parte inferiore è chiamata sottostruttura e la parte superiore è chiamata sovrastruttura. La discontinuità accoppia le risposte dinamiche della sottostruttura e della sovrastruttura.
Il terzo capitolo studia l’accoppiamento tra due differenti tipi di strutture, in particolare tra un telaio ed un blocco rigido. Il blocco viene accoppiato, attraverso un dispositivo visco-elastico, al piano inferiore del telaio. Sono anche considerati dispositivi inerter applicati sia al blocco sia al telaio.
Il quarto capitolo indaga l’accoppiamento tra un telaio ed un esoscheletro. Differentemente dall’approccio tradizionale, l’esoscheletro è collegato solo alla parte inferiore della struttura, così riducendo sia l’impatto estetico che il costo della strategia di protezione.
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CASTORO, CHIARA. "DEVELOPMENT OF NEW WIRELESS SENSORS AND METHODS FOR CIVIL ENGINEERING APPLICATIONS." Doctoral thesis, Università degli Studi dell'Aquila, 2022. http://hdl.handle.net/11697/190999.
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In the proposed research, effective and innovative monitoring solutions inspired by the principles of low cost, miniaturization, system energy autonomy, and measurement reliability, for remote and widespread monitoring of historical and civil structures in general, have been developed and tested. The advantages of new wireless measuring methods over traditional wired technologies and devices have been investigated. New methods and devices have been proposed for different monitoring purposes. These methods and devices have been developed and tested through experimental campaigns, in laboratory and in situ, and have been validated with wired traditional techniques for comparison. The new measuring principle of a new RFID-enabled wireless strain gauge has been tested in static and dynamic conditions, respectively by measuring the elastic modulus of three different materials and by measuring induced environmental vibrations on a steel cantilever. The accuracy of the proposed new technique has been proved to be high, reaching a maximum interrogating distance of 20 meters in laboratory and outdoor, very suitable for structural monitoring. The use of commercial UHF-RFID tags for civil engineering purposes has been investigated, specifically for the monitoring of out-of-plane displacements,
representing an application novelty since commercial tags are usually used in logistics and other purposes. The feasibility of the application of this technique was assessed by laboratory and in situ experimental campaigns. The response of the Tags in laboratory environment demonstrated to be very satisfactory, proving that the application of these wireless RFID tags is feasible, potentially very reliable. In situ experiments showed a weaker response of the Tags due to environmental interference caused by the high presence of metal which affected negatively the transmission of the electromagnetic signal, and consequently the indirect measurements of displacements. Despite some limits, the application is promising and opens up
new scenarios for the design of new wireless tags suitable to meet the required needs.
A new wireless RFID sensor for crack width monitoring has been developed and tested in laboratory through a three-point bending tests on different materials. Compared to traditional crack-width measurement procedures, the proposed new technique results to be potentially more suitable, with an interrogation distance up to 1.5 m in this raw state, which could be extended more to allow the positioning of these devices in points difficult to access by traditional wired sensors. The devices are currently in a raw form and require technological development in order to be applied on large scale. Some critical aspects related to the strong influence of metal can be overcome in future steps of design of the sensors and further investigation is surely required. In this thesis a large-scale approach to wireless structural monitoring has been also investigated. A sensor network with commercial wireless tri-axial MEMS accelerometers was deployed on the deck of a butterfly-arch stress-ribbon pedestrian bridge located in Fuzhou, Fujian, China, to record the structural response under ambient vibration and perform dynamic identification, finite element modelling and parametric updating. A satisfactory agreement between the model prediction and the experimental data was achieved. The most accurate model has been chosen to be used as baseline for long-term monitoring of the bridge. In the SHM field, this last study demonstrates the importance of the modelling strategy in simulating the dynamic behaviour of complex structures, as the one considered in this research, in comparison to traditional ones which can be modelled following simplified modelling procedures.
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SCAFATI, FEDERICO. "Monitoraggio strutturale e comportamento dinamico di edifici e viadotti dotati di isolamento sismico." Doctoral thesis, Università degli Studi dell'Aquila, 2020. http://hdl.handle.net/11697/157358.
Full textAbstract:
I terremoti che hanno colpito l’Italia negli ultimi anni (Terremoto in Molise 2002, terremoto in Abruzzo 2009, Terremoto in Emilia 2012, Terremoto nel Centro Italia 2016, Terremoto di Ischia 2017, etc.) hanno evidenziato l’estrema fragilità delle strutture e delle infrastrutture presenti sul nostro Territorio nei confronti dell’azione sismica. Troppo spesso gli edifici che evidenziano carenze strutturali a seguito dell’evento sismico, sono anche quelli che dovrebbero svolgere un ruolo strategico nella gestione delle emergenze (ospedali, scuole, caserme, etc.). Allo stesso modo, accade che spesso tali criticità vengono a manifestarsi anche sulle infrastrutture, che rappresentano un’indispensabile rete di collegamento con le aree colpite e che svolgono un ruolo strategico per l’arrivo dei soccorsi.
Contemporaneamente, e cosa ancor più grave, negli ultimi anni una serie di eventi hanno evidenziato che tali strutture ed infrastrutture, risultano spesso carenti anche in condizioni statiche.
Negli edifici, alcuni recenti accadimenti hanno confermato che spesso tali criticità sono dovute a errori di progettazione e di realizzazione, sciagurati interventi di riqualificazione degli spazi con indebolimento della struttura portante, sovraccarico dei solai, degrado e mancata manutenzione. Quando, per cause del tutto analoghe, tali criticità vengono a manifestarsi in strutture quali ponti, viadotti, cavalcavia o gallerie, gli effetti possono risultare anche più gravosi. C’è senza dubbio la necessità di invertire tale tendenza. Una delle possibili strade è senza dubbio quella di sfruttare l’evoluzione tecnologica in atto e fare tesoro dei risultati ottenuti dalla ricerca nel campo delle moderne tecniche di prevenzione e di protezione delle strutture: il MONITORAGGIO STRUTTURALE. D’altra parte, per resistere efficacemente ai terremoti, è oramai ampiamente dimostrato dall’evidenza sperimentale che, dotare una struttura di SISTEMI DI ISOLAMENTO SISMICO può significare salvaguardare vite umane e mantenere adeguati livelli di operatività della stessa subito a seguito dell’evento, con un notevole risparmio economico legato al non danneggiamento della struttura. In particolare tale ultimo aspetto risulta fondamentale per tutte le strutture strategiche e che svolgono un ruolo primario nella gestione delle emergenze. L’attività di ricerca condotta nel corso del triennio di Dottorato e riassunta in tale Tesi, vuole essere una conferma dei concetti fin qui espressi, circa l’importanza del monitoraggio strutturale e dell’efficacia di un sistema di isolamento correttamente progettato. I risultati ottenuti hanno permesso di approfondire gli aspetti specifici del problema, evidenziando che, nel momento in cui le ipotesi di progetto differiscono sensibilmente dalle condizioni reali, il comportamento statico e/o dinamico sperimentale della struttura può essere sensibilmente differente da quello atteso. Tali differenze di comportamento tra progetto e realtà, che spesso non sono visibili ad occhio nudo o attraverso le classiche metodologie di indagine, possono essere preventivamente messe a risalto grazie all’ausilio di dati sperimentali ricavati dal monitoraggio strutturale.
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ANGIOLILLI, MICHELE. "Sviluppo di nuovi materiali, modelli e tecniche innovative per la conservazione e il rafforzamento sismico del patrimonio edilizio monumentale storico." Doctoral thesis, Università degli Studi dell'Aquila, 2020. http://hdl.handle.net/11697/160483.
Full textAbstract:
Historically, masonry structures have exhibited, despite the intrinsic fragility of the material, extraordinary stability withstanding the effects of aging, human settlements, and natural elements over the centuries. This has led to the thinking that such structures would be eternal. However, most architectural and artistic heritage, such as castles, churches, monuments, lighthouses, mosques, arch bridges, vaults, and domes have been destroyed. Each year, we witness the further collapse of remaining historic masonry structures.
In the last decade, there has been a growing demand for protecting heritage structures around the world. This demand reflects humanity’s deep awareness, responsibility, and necessity to maintain the existing architectural heritage and to pass it on to future generations. Furthermore, restoration initiatives have increased, in part, because of new technologies that produce new materials and strengthening systems. The development of a fiber-based strengthening system began in the 1960s, when the potential for adding steel fibers to enhance the ductility of concrete material was recognized. However, this technology has been commonly adopted for the reinforcement of masonry structures only in the last decade as an alternative to traditional systems, such as mortar injections, reinforced drilling, and reinforced concrete plaster.
The study of historic masonry structures, especially if coupled with a sophisticated strengthening system, is a challenging task because of the difficulties encountered in the description of the complex geometry, morphology, material heterogeneity, material properties characterization, and material variation. Despite its simple composition, masonry is characterized by a composite material that leads to a complex prediction of its mechanical behavior.
The theme of the proposed research is in line with the priorities of the Beni Culturali and co-financed by the Project “2014-2020 PON”, which was approved by the Research Directorate of the Italian Ministry of Education (MIUR) and co-funded by the European Social Fund (ESF). The project was realized through the correspondence of interests between the University of L'Aquila (Italy), the industrial partner “Aquilaprem s.r.l.'” (Italy), and the research partner “Northwestern University” (U.S.A.). The project aimed to characterize the existing innovative technologies as well as to identify new material for the conservation and development of the vast historical and architectural heritage that nowadays are particularly vulnerable to the environmental actions. In particular, the development of a new type of natural hydraulic lime mortar, reinforced by short fibers randomly arranged in the mortar matrix, was performed. Both experimental tests and numerical simulations were detailed discussed in the thesis. For the latter case, a sophisticated numerical framework, the so-called Lattice Discrete Particle Model, was proposed for the first time to stone masonry aiming to capture fracture, damage localization, and frictional shearing, occurring at weak locations in the internal material structure that coincide with interfaces among particles. Indeed, numerical continuum-based models, which homogenize material behavior, are inherently limited in capturing the mesoscale interactions, fracture propagation, and damage evolution of quasi-brittle materials.
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DE, ANGELO MICHELE. "Sviluppi dell'ingegnerizzazione del metamateriale pantografico: modelli, fabbricazione, esperimenti e caratterizzazione meccanica." Doctoral thesis, Università degli Studi dell'Aquila, 2021. http://hdl.handle.net/11697/168330.
Full textAbstract:
In the last decade, investigating the exotic properties of microstructured materials has gathered increasing attention and contributions. Among various fascinating typologies of engineered materials, the class of pantographic metamaterials has demonstrated theoretical and mechanical peculiarities. Their development is a dense fusion of theoretical knowledge of the most advanced theories in continuum mechanics and their application through modern manufacturing and measuring techniques. The present work aims to present some of the modeling solutions of such novel materials and how a full understanding of their theoretical framework can realize physical structures with unconventional and specifically designed mechanical behavior. Additionally, the work provides some experimental evidence in the field of pantographic metamaterials, focusing on significant results of 2D specimens of pantographic metamaterial printed using metallic powder and preliminary analysis on the pantographic microstructure’s elementary module. Lastly, a constitutive parameters identification of a discrete model for a millimetric pantographic unit cell is attempted and achieved. With novel measurement techniques such as Digital Image Correlation, it was possible to obtain a complete characterization of a Hencky-type discrete pantograph model, which is closely linked to continuous models widely treated in the recent bibliography.
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DI, BATTISTA LUCA. "Indicatori di danno subspace-based: dai test di rilevamento danni all'analisi di affidabilità strutturale." Doctoral thesis, Università degli Studi dell'Aquila, 2021. http://hdl.handle.net/11697/170119.
Full textAbstract:
It is common practice in Structural Health Monitoring (SHM) to perform damage detection by detecting changes in subspace-based damage indicators.
They are computed by comparing a reference state with the current (possibly damaged) state through a matrix based on the computation of residuals originated from the orthogonality defect of projected subspaces.
In the last decades, several scalar indicators have been proposed based on the residual matrix. Still, a multivariate sensitivity analysis was not carried out to estimate the sensitivity of each indicator to the excitation changes.
In this thesis, a covariance-based sensitivity analysis applied to a spatial truss structure is carried out to evaluate the sensitivity of eight damage indicators to ambient excitation covariance, damage severity, and damage location.
The analysis aims at identifying the ranges of applicability of damage indicators within a simple statistical framework, possibly extendable to more general applications. It is argued whether any equivalent class of indicators can be obtained from the manipulation of the residual matrix. The role of damage location in the probabilistic assessment of damage is discussed: a methodological Bayesian approach, based on the results of the sensitivity analysis, is proposed for the development of a structural reliability analysis driven by damage indicators. An real-case application of damage detection tests is further presented for the Santa Maria di Collemaggio basilica.
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ALOISIO, ANGELO. "Risposta sismica delle strutture in legno lamellare incrociato." Doctoral thesis, Università degli Studi dell'Aquila, 2021. http://hdl.handle.net/11697/169275.
Full textAbstract:
La presente monografia si incentra sulla stima della risposta sismica di edifici in Cross-Laminated Timber. I primi sforzi di ricerca hanno maturato un modello di isteresi della classe Bouc-Wen, concepito per la modellazione della risposta isteretica di pareti in CLT. I risultati delle analisi svolte con questo modello hanno portato alla definizione delle curve di fragilità, fattori di struttura e smorzamento viscoso equivalente di archetipi trutturali in CLT. Gli archetipi strutturali sono rappresentativi di particolari aggregati strutturali, i quali identificano delle strutture elementari modellate attraverso l'uso del modello in parola.
La monografia dedica poi una estesa discussione al ruolo delle connessioni, mettendo a confronto i risultati della risposta sismica con quella c.d. operativa.
Il primo capitolo introduttivo descrive lo stato della letteratura nella stima della risposta sismica di edifici in CLT. Il secondo capitolo è dedicato alla descrizione del modello di istersi adottato per la modellazione delle pareti di taglio in CLT. Il terzo capitolo riporta i risultati delle curve di fragilità e dei fattori di struttura. Il quarto capitolo riporta invece i risultati della stima dello smorzamento viscoso equivalente dei medesimi archetipi strutturali. Il quinto capitolo presenta una discussione sui fattori di sovraresistenza, proponendo un metodo probailistico per la loro stima. Il sesto e ultimo capitolo è dedicato alla analisi della risposta in condizioni operative di un edificio reale in CLT.
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RINALDI, VINCENZO. "The seismic behaviour of Cross-Laminated Timber buildings: Evaluation of the behaviour factor for the revision of the Eurocode 8." Doctoral thesis, Università degli Studi dell'Aquila, 2021. http://hdl.handle.net/11697/169273.
Full textAbstract:
Over the last 15 years, the wood-based structural industry has achieved general growth around the world. This positive trend is due to many reasons: the awareness of the importance of sustainable development and the high structural performance of timber structures in seismic-prone areas. Several researches were conducted in these years, leading to a deeper knowledge of seismic timber design. In particular, the Cross-Laminated Timber (CLT) system was widely investigated, becoming a competitive choice in seismic areas compared to other structural materials. Starting from 2015, the revision process of the overall structural Eurocodes is leading to a significant change even in the section dedicated to timber buildings’ seismic behaviour.
The aim of this thesis is to evaluate and to propose the behaviour factors of CLT structures designed with dissipative behaviours for the revision of EN 1998:2004 (Eurocode 8). The work combines the review process of Eurocode 8 and of EN 12512. The two norms are linked since Eurocode 8 defines the demand whereas the EN 12512 describes the metodology to estimate the capacity of dissipative joints. The results, which came from ongoing studies, have been obtained using the Eurocode 8 version-prEN1998-1-2:2020 (EC8 draft) dated 30/04/2020.
The motivations of a new estimation of the q-factor for CLT buildings are highlighted within a critical review of the current Eurocode 8. In specific, the behaviour factor will be divided into three contributions due to the new material independent formulation, and new seismic design rules will be introduced in the EN 1998 for CLT buildings. The definition of the intrinsic q-factor component has been carried out via numerical investigations based on experimental results on traditional CLT connections analysed with the EN 12512 draft. A significant amount of analysis has been done to define the conservative values. At the beginning, static non-linear analyses have been performed on several 2D configurations, and subsequentially, dynamic non-linear analyses have been done on some of the previous configurations. The obtained outcomes propose conservative values of the q-factors for the moderate and high ductility classes. Moreover, a new finite element (FE) strategy has been developed, starting from a state-of-the-art for practice-oriented purpose. The FE model allows integrating into a linear-elastic model the non-linearities of the seismic behaviour of CLT buildings, often neglected.
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FRATTARI, LUCA. "THE STRUCTURAL FORM: Topology Optimization in Architecture and Industrial Design." Doctoral thesis, Università degli Studi di Camerino, 2011. http://hdl.handle.net/11581/401848.
Full textAbstract:
The expression Structural Form is used to define the co-existence of two aspects: Form and Structure. In the constructive practice, form and structure are not always integrated and can appear separately; the skin of a building can hide a different inner structure or the style of an object is often independent from its structural system. In many cases the Structural Form is the result of man's adaptation to special conditions: climatic, historical, economical, cultural. In nature that definition is adopted by the life forms following the evolutionary principles that rule the development of biological forms. In mostly of life-forms, structure and form tend to be coincident. Branches of trees and skeleton bones have a specific Structural Form which define their function and design. In this sense Structural Form has a natural meaning. The natural meaning of Structural Form can be adopted in special forms of structural elements, created to build specific architectures. This concept was applied in the past to build architectures based on empirical knowledge and it has been abandoned in the last century to follow abstract forms. The experiences shown in the present work have demonstrated how structural optimization procedures, like topology optimization, are able to mimic natural processes in defining architectural structures and industrial design objects with an aesthetic added-value that might represent an alternative and attractive vision.
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LEVI, FRANCESCA. "Variational principles for evolution problems." Doctoral thesis, Università degli studi di Brescia, 2023. https://hdl.handle.net/11379/571585.
Full textAbstract:
Lo studio di fenomeni che evolvono nel tempo è spesso condotto attraverso la loro modellazione come sistemi dinamici, la cui formulazione matematica, in genere, richiede la risoluzione di sistemi di equazioni differenziali a condizioni iniziali.
Risolvere le equazioni che governano un fenomeno fisico evolutivo significa determinarne l'evoluzione nel tempo a partire da un insieme di condizioni iniziali; ad esempio, considerando i sistemi meccanici, attraverso una legge matematica che ne determina la posizione e la velocità in funzione del tempo.
Tuttavia, le equazioni che governano il moto spesso non possono essere risolte analiticamente e quindi vengono utilizzate tecniche di integrazione numerica per ottenere un'approssimazione accurata della soluzione.
Trattare il problema dello studio di un sistema fisico da un punto di vista variazionale può essere un approccio diverso, motivato dalla formulazione Lagrangiana della meccanica classica.
L'idea di sostituire un dato problema con uno equivalente in forma variazionale non è certo nuova: l'interesse per questa formulazione è infatti giustificato dalla validità dei cosiddetti metodi diretti del calcolo delle variazioni.
Questi metodi sono validi sia per uno studio qualitativo del problema (verifica dell'esistenza e unicità della soluzione, la sua regolarità, ecc.), sia per uno studio quantitativo, cioè da
un punto di vista numerico (valutazione della convergenza, stima dell'errore della soluzione approssimata).
In questa tesi vengono analizzati problemi evolutivi di interesse ingegneristico, formulati per via variazionale.
In primo luogo, il problema viscoelastico lineare viene risolto numericamente utilizzando tre diverse formulazioni variazionali: la formulazione di Gurtin, la formulazione di Gurtin splittata e la formulazione di Huet.
Il metodo degli elementi finiti viene utilizzato per la discretizzazione spaziale e il metodo Ritz viene utilizzato per la discretizzazione temporale.
Successivamente, si prende in considerazione il problema della conduzione del calore. Vengono considerate due formulazioni: la prima basata su una forma bilineare convolutiva, la seconda su una forma bilineare biconvolutiva. Numerosi esperimenti numerici mettono in luce la bontà dei due diversi approcci.
Viene poi affrontato il tema della determinazione di upper e lower bounds per le proprietà meccaniche di materiali compositi costituiti da fasi aventi legami costitutivi viscoelastici.
Successivamente viene analizzato il problema dell'evoluzione di una frattura sia in un mezzo elastico sia in un mezzo viscoelastico. Nel primo caso viene proposta una formulazione estremale analoga a quella di Capurso e Maier, valida in ambito elastoplastico.
Infine, viene considerata la stabilità dinamica di sistemi piani con una sola massa concentrata e soggetti a forze follower.The study of phenomena that evolve over time is often conducted through their modelling as dynamic systems, whose mathematical formulation generally requires the resolution of systems of differential equations with initial conditions. Solving the governing equations of a physical phenomenon means determining its evolution over time starting from a set of initial conditions; for example, considering mechanical systems, through a mathematical law that determines its position and speed as functions of time. However, the equations governing motion cannot be often solved analytically and therefore, numerical integration techniques are used in order to obtain an accurate approximation of the solution. Treating the problem of studying a physical system from a variational point of view may be a different approach, motivated by the Lagrangian formulation of classical mechanics. The idea of replacing a given problem with an equivalent one in variational form is certainly not new: the interest in this formulation is in fact justified by the validity of the so-called direct methods of the calculation of variations. These methods are valid both for a qualitative study of the problem (verification of existence and uniqueness of the solution, its regularity, etc.), and for a quantitative study, namely from a numerical point of view (evaluation of convergence, estimation of the error of the approximate solution). In this thesis, evolution problems of engineering interest are analyzed, formulated in a variational way. Firstly, the linear viscoelastic problem is numerically solved using three different variational formulation, such as Gurtin's variational formulation, Split Gurtin formulation and the Huet formulation. The Finite Element Method is used for the space discretization and the Ritz method is used for the time discretization. Then, the heat conduction problem is taken into account. Two formulations are considered: the first one based on a convolutive bilinear form, the second one based on a biconvolutive bilinear form. Several numerical examples highlight the goodness of the two different approaches. Next, the problem of the determination of upper and lower bounds for the mechanical properties of composite materials, consisting of phases having viscoelastic constitutive laws, is addressed. Subsequently, the problem of the evolution of a fracture is analyzed both in an elastic medium and in a viscoelastic medium. In the first case, an extremal formulation, similar to that of Capurso and Maier, is proposed, valid in the elastoplastic field. Finally, the dynamical stability of plane systems with just one lumped mass, subjected to follower forces, is considered.
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Arricca, Matteo. "Finite strain chemo-thermo-electro-mechanics with applications in mechanobiology." Doctoral thesis, Università degli studi di Brescia, 2022. https://hdl.handle.net/11379/567425.
Full textAbstract:
La tesi proposta nasce da ben definite motivazioni biologiche, con lo scopo di fornire una caratterizzazione del comportamento delle cellule endoteliali nel processo di angiogenesi tumorale. Diversi framework multi-fisici vengono introdotti per applicazioni nel campo della meccanobiologia, così come in altre aree di ricerca.
L’angiogenesi è un noto processo progressivo, fisiologico o patologico, caratterizzato dalla formazione di nuovi vasi sanguigni che si originano da quelli pre-esistenti. Le cellule endoteliali, le quali rivestono le pareti interne dei vasi sanguigni, vengono influenzate da stimuli extra-cellulari rilasciati dalle cellule tumorali, e rispondono tramite rilocazione di recettori (proteine) sulla loro membrana, migrazione cellulare collettiva e riorganizzazione in nuovi vasi sanguigni. Il ruolo della dinamica recettoriale e della meccanica cellulare in risposta agli stimuli extra-cellulari è dunque oggetto di grande interesse, in quanto processi cruciali nelle fasi iniziali dell’angiogenesi. Le funzioni strutturali della cellula, le quali permettono l’avvenimento di processi ben noti come l’adesione e l’accasciamento cellulare, la motilità e la migrazione, sono attribuite alla generazione e la riorganizzazione della macchina contrattile citoscheletrica. Il citoscheletro è una rete interconnessa di proteine e polimeri filamentosi, soggetto ad un imponente riarrangiamento che permette la generazione di diverse strutture polimeriche, fornendo le forze e il supporto strutturale necessari per il movimento cellulare.
Il ruolo della meccanica nei processi biologici è dunque di inconfutabile rilevanza, così come la responsabilità della meccanobiologia di fornire un supporto ad una caratterizzazione esaustiva dei sistemi viventi.
Modell multi-fisici con applicazioni in meccanobiologia richiedono di tener conto degli svariati fenomeni coinvolti nel processo sotto investigazione. La teoria della meccanica del continuo in grandi deformazioni rappresenta certamente il miglior candidato per descrivere la risposta strutturale delle cellule soggette a massicce deformazioni durante i processi di adesione cellulare, accasciamento e migrazione. Ciononostante, la sola meccanica è evidentemente insufficiente.
Nonostante l’accoppiamento tra la meccanica in grandi deformazioni e la termodinamica sia alla base di innumerevoli modelli multi-fisici, è indubbia la necessità di considerare altri processi quali il trasporto di massa con appropriate leggi di diffusione, e di tenere conto delle reazioni chimiche. L’accoppiamento tra termodinamica, meccanica e chemo-diffusione conduce alla realizzazione dei così definiti chemo-transport-mechanical frameworks. Inoltre, e così come ben noto nel campo della termodinamica, la necessità di fornire una caratterizzazione statisticamente basata di alcuni fenomeni è frequente. È il caso della modellazione dei reticoli polimerici nel campo della fisica dei polimeri. Si presentano di conseguenza sfide aggiuntive nel tener conto di eventi multi-fisici a differenti scale spazio-temporali.
In questa tesi, i modelli teorici multi-fisici proposti trovano applicazioni che non sono puramente ristrette al campo della meccanobiologia. Termodinamica e meccanica in grandi deformazioni, meccanica dei continui statisticamente basata, e la teoria dell’elettromagnetismo Galileiano, rappresentano i principali temi investigati nella tesi e adottati per la realizzazione di diverse formulazioni multi-fisiche.The proposed thesis comes from well-defined biological motivations, aiming at providing a characterization of endothelial cell behavior in tumor angiogenesis. Several multi-physics frameworks are introduced for applications in the realm of mechanobiology, as well as in many other research areas. Angiogenesis is a well known physiological or pathological multistep process that consists in the formation of new blood vessels from preexisting ones. Covering the inner walls of blood vessels, endothelial cells are affected by extracellular stimuli released by tumor cells, and respond via relocation of receptor proteins along their membrane, collective migration and reorganization in novel vessels. The role of receptor dynamics and cell mechanics in response to extracellular stimuli is therefore object of great interest, as they are pivotal processes at the early stages of angiogenesis. Cell structural functions, allowing the occurrence of well known processes such as cell adhesion and spreading, motility and migration, are ascribed to the generation and reorganization of the cytoskeletal contractile machinery. The cytoskeleton is an interconnected network of regulatory proteins and filamentous polymers that undergoes massive rearrangements to generate different biopolymer structures, providing the necessary forces and structural support for cell movements. It is therefore of unquestionable relevance the role of mechanics in biological processes, as well as the responsibility of mechanobiology to provide a support for an exhaustive characterization of alive systems. Multi-physics models with applications in mechanobiology require to account for several phenomena involved in the process under investigation. The finite strain theory in continuum mechanics certainly represents the best candidate to describe the structural response of cells undergoing massive deformations during cell adhesion, spreading, and migration. However, mechanics itself is evidently not sufficient. Despite the coupling between finite strain mechanics and thermodynamics stands for the basis of a countless amount of multi-physics models, the necessity to consider other processes such as mass transport with proper diffusion laws, and to account for chemical reactions, is beyond doubt. The coupling between thermo-mechanics and chemo-transport phenomena leads thus to design the so-termed chemo-transport-mechanical frameworks. Furthermore, and as well known in the realm of thermodynamics, insightful models often need to provide a statistically-based characterization of phenomena. It is the case of cross-linked polymer networks modeling in the field of polymer physics. Additional challenges therefore arise in accounting for multi-physics events that occur at different space-time scales. In this thesis, general and theoretical multi-physics models are proposed for applications that are not only restricted to the realm of mechanobiology. Finite strain continuum thermo-mechanics, diffusion laws and phase segregation, chemical reactions with trapping, statistically-based continuum mechanics, and the Galilean electromagnetic theory, represent the main topics investigated in this thesis and adopted for designing several multi-physics formulations.
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BASAK, APU. "Topology optimization in modelling and design of the endplates of Proton Exchange Membrane Fuel cells." Doctoral thesis, Università degli studi di Brescia, 2022. http://hdl.handle.net/11379/563083.
Full textAbstract:
When individual proton exchange membrane fuel cells (PEMFCs) are assembled together to form a stack and provide energy for practical applications, an appropriate clamping load is usually required for better efficiency, high reliability, and excellent durability. Smaller clamping force increase ohmic resistance. In terms of the losses within proton exchange membrane fuel cells, the ohmic loss alone carries a significant portion. The ohmic loss occurs due to mainly the contact resistance between the GDL and the bipolar plate (BPP). On the other hand, excessive clamping force breaks the carbon fibers of the GDL results lifetime reduction and ultimately efficiency drop. That’s why the Endplates of the proton exchange membrane fuel cell (PEMFC) need to be well designed as their strength and rigidity directly affect the uniform clamping pressure distribution and thus affect the performance and lifetime of fuel cell stacks.
This paper presents a methodology to design, analyze, and improve the mechanical responses of a practical proton exchange membrane fuel cell (PEMFC) stack. A practical assembly is analyzed with finite element analysis (FEA) to study the stress distribution and clamping pressure loss. To minimize the clamping pressure loss, the design criteria are proposed. And finally, topology optimization is carried out and the endplate is redesigned to obtain a lightweight optimized structural design.When individual proton exchange membrane fuel cells (PEMFCs) are assembled together to form a stack and provide energy for practical applications, an appropriate clamping load is usually required for better efficiency, high reliability, and excellent durability. Smaller clamping force increase ohmic resistance. In terms of the losses within proton exchange membrane fuel cells, the ohmic loss alone carries a significant portion. The ohmic loss occurs due to mainly the contact resistance between the GDL and the bipolar plate (BPP). On the other hand, excessive clamping force breaks the carbon fibers of the GDL results lifetime reduction and ultimately efficiency drop. That’s why the Endplates of the proton exchange membrane fuel cell (PEMFC) need to be well designed as their strength and rigidity directly affect the uniform clamping pressure distribution and thus affect the performance and lifetime of fuel cell stacks. This paper presents a methodology to design, analyze, and improve the mechanical responses of a practical proton exchange membrane fuel cell (PEMFC) stack. A practical assembly is analyzed with finite element analysis (FEA) to study the stress distribution and clamping pressure loss. To minimize the clamping pressure loss, the design criteria are proposed. And finally, topology optimization is carried out and the endplate is redesigned to obtain a lightweight optimized structural design.
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Tubaldi, Enrico. "Probabilistic seismic response and fragility assessment of steel-concrete composite bridges with dual load path." Doctoral thesis, Università Politecnica delle Marche, 2010. http://hdl.handle.net/11566/242260.
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Pace, Giuseppe. "Analisi non lineare di struttura a telaio spaziale in c.a. con rinforzo in gfrp." Doctoral thesis, Università Politecnica delle Marche, 2009. http://hdl.handle.net/11566/242136.
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MARCHEGGIANI, LAURA. "Synchronization phenomena in complex dynamical systems." Doctoral thesis, Università Politecnica delle Marche, 2010. http://hdl.handle.net/11566/242227.
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Clementi, Francesco. "Modellazione e problematiche dei materiali compositi "moderni" e "antichi"." Doctoral thesis, Università Politecnica delle Marche, 2010. http://hdl.handle.net/11566/242251.
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GENOVESE, DARIO. "Considerazioni sulla dualità statico-cinematica. Modelli teorici e applicazioni numeriche." Doctoral thesis, Università Politecnica delle Marche, 2012. http://hdl.handle.net/11566/242104.
Full textAbstract:
Gli ultimi decenni sono stati protagonisti di un rapido sviluppo dell'informatica e dell'elettronica con importanti conseguenze in tutto il mondo tecnico e scientifico. In meccanica strutturale i principi energetici variazionali sono diventati la base teorica di molte procedure di analisi numerica.
La tesi è uno studio sul Principio dei Lavori Virtuali e sul suo utilizzo pratico per dedurre modelli teorici strutturali in vari ambiti. Particolare enfasi viene inoltre posta sull’approccio numerico a questi modelli, visto che la diffusione dell'uso dei Personal Computer in qualsiasi applicazione ingegneristica è ormai capillare.
Il principale obiettivo raggiunto è sicuramente l'aver dimostrato che anche teorie strutturali a prima vista molto complesse e le relative metodologie di analisi numerica si basano in realtà su un semplice principio il cui enunciato occupa poche righe, rimanendo da definire nello specifico solamente l'ambiente in cui tale principio opera e l'implementazione su elaboratore di un buon algoritmo solutore.
Come originali esempi di applicazione pratica del PLV sono stati proposti:
- Un metodo di analisi per strutture reticolari, usato concretamente per studiare una struttura reticolare pretesa in acciaio
- Una cinematica del secondo ordine per la trave curva, di cui si è data anche un'interpretazione fisica e geometrica
- Un modello tridimensionale di tipo Cosserat per definire il comportamento dei materiali ferroelettrici, insieme alla relativa interpretazione fisica a livello atomico
- Un metodo generico per trasformare un modello continuo monodimensionale in discreto tramite la definizione di opportuni elementi finiti, valido per ogni cinematica non lineare del secondo ordine
- Una generalizzazione del PLV in dinamica che coinvolge l'idea di dualità anche quando entra in gioco la dimensione tempo.The last decades have been involved in a rapid development of computer science and electronics with major worldwide scientific and technical consequences. In structural mechanics the variational energetic principles have become the theoretical basis of many numerical analysis procedures. The thesis is a study on the Principle of Virtual Work and its practical use to deduce structural and theoretical models in various fields. Particular emphasis is also placed on the numerical approach to these models, since the widespread use of personal computers in any engineering application has become very common. The main aim reached is definitely to have shown that even at first sight very complex structural theories, and related numerical analysis methods, are actually based on a simple principle whose utterance occupies a few lines, remaining in the specific only to define the environment in which this principle operates and the implementation on a computer of a good solver algorithm. As original examples of practical application of the PVW has been proposed: - An analysis method for pin-jointed structures, practically used to study a prestressed pin-jointed steel structure. - A second order kinematics for curved beams, of which has also been given a physical and geometrical explanation. - A threedimensional Cosserat-like model to define the behavior of ferroelectrics materials, together with its physical interpretation at atomic level. - A generic method to transform a monodimensional continuous model in a discrete one, through the definition of suitable finite elements, usable for each non linear second order kinematics. - A PVW generalization for dinamics, which involves the notion of duality even when comes into play the time dimension.
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MORETTINI, MATTEO. "Criteri di calcolo di un impalcato a sezione bitrave composta acciaio-calcestruzzo secondo gli Eurocodici." Doctoral thesis, Università Politecnica delle Marche, 2009. http://hdl.handle.net/11566/242283.
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DEZI, GABRIELE. "La verifica dei ponti a cassone composti acciaio-calcestruzzo secondo gli Eurocodici." Doctoral thesis, Università Politecnica delle Marche, 2009. http://hdl.handle.net/11566/242139.
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Roia, Davide. "Dynamic response of piles under lateral loading: full scale field test and numerical analysis." Doctoral thesis, Università Politecnica delle Marche, 2011. http://hdl.handle.net/11566/241933.
Full textAbstract:
Negli ultimi anni il tema dell’interazione terreno-struttura ha suscitato un’attenzione
particolare nel campo dell’ingegneria geotecnica e strutturale. Le caratteristiche dinamiche del sistema terreno-fondazione possono condizionare fortemente il comportamento sismico della struttura di elevazione. Questo problema è particolarmente importante nel caso di
fondazioni profonde: le proprietà meccaniche e la geometria del terreno e delle fondazioni,così come la loro mutua interazione, possono influenzare le caratteristiche di rigidezza e
smorzamento del sistema suolo-palo durante il moto sismico.
Sia nella ricerca che nella progettazione avanzata questo problema può essere studiato in modo diretto, modellando l’intero sistema dinamico suolo-palo con un modello 3D agli
elementi finiti, o utilizzando metodi teorici. I risultati di questi approcci sono molto sensibili al grado di dettaglio del modello e a molti parametri che definiscono le caratteristiche dinamiche del sistema terreno-palo. In questo contesto, i risultati di test
sperimentali in situ, in vera grandezza o in scala ridotta, e i risultati di test di laboratorio rappresentano uno strumento essenziale per fornire i parametri necessari ai modelli numerici e analitici e per validarne i risultati. Tuttavia, in letteratura non sono molti i lavori
che riguardano prove in situ in vera grandezza su fondazioni profonde.
Questo lavoro presenta un esteso programma di prove sperimentali in situ in vera grandezza condotto su un gruppo di tre pali in acciaio al porto turistico di La Spezia, in Italia. Il programma comprende tre tipologie di prove dinamiche con differenti livelli di eccitazione:
prove di impatto, prove di vibrazione libera e di vibrazione forzata. I pali sono vibro-infissi in argilla marina soffice in una configurazione ad L e non sono vincolati in testa. Il programma di prove è stato eseguito in due tempi: la prima campagna una settimana dopo la vibro-infissione dei pali e la seconda dopo dieci settimane. I pali sono stati strumentati
con accelerometri disposti in testa a ciascun palo e con strain gages e trasduttori di pressione disposti lungo il palo d’angolo, utilizzando una tecnica non convenzionale per prove in sito in ambiente marino. Viene presentato e discusso il comportamento dinamico
del complesso sistema suolo-acqua-palo soggetto a diversi livelli di forza. Con riferimento al palo singolo, ne viene presentata la risposta in termini di frequenze naturali, smorzamenti
e forme modali dei primi due modi flessionali. Con riferimento al gruppo di pali sono valutati gli effetti dell’interazione palo-palo dovuti alla propagazione di diversi tipi di onde,
in relazione alla direzione dell’azione. Si discute la variazione del comportamento dinamico del sistema nel tempo (per le due campagne di prove) dovuta alla ri-consolidazione del terreno vicino ai pali susseguente la vibro-infissione. Inoltre, viene effettuata una stima
della velocità delle onde di taglio dello strato di terreno superficiale sulla base della misurazione dei ritardi temporali dei segnali accelerometrici alla testa dei pali. I risultati sperimentali sono inoltre confrontati con quelli ottenuti mediante differenti approcci numerici: in particolare sono stati sviluppati due differenti modelli 3D agli elementi finiti in ABAQUS, considerando elementi di tipo solido o di tipo shell per la modellazione dei pali,
i cui parametri sono calibrati sulla base dei risultati sperimentali. Infine si mostrano i confronti con i risultati ottenuti mediante il modello 3D per l’analisi cinematica di
fondazioni su pali formulato da Dezi et al. (2009), opportunamente modificato al fine di
simulare le prove della campagna sperimentale.The topic of soil-structure interaction has received large attention in recent years. The seismic performance of a superstructure can be significantly affected by the behaviour of soil and foundation and their mutual interaction under an earthquake motion. This problem is particularly significant in the case of deep foundations; mechanical properties and geometrical characteristics of soil and piles as well as their mutual interaction may affect the stiffness and damping characteristics of the soil-pile system during earthquake motion.In both research and advanced practice, this problem may be approached with a direct method, modelling the whole dynamic soil-pile system with a 3-D finite element model, or by using theoretical approaches. However, the results of these approaches are very sensitive to the degree of the model refinement and to many parameters that define the dynamic characteristics of the soil-pile system. In this context, experimental results of full- or smallscale in situ and laboratory tests represent an essential instrument to provide parameters for and to validate numerical and analytical methods. However, few full-scale in-situ tests on pile foundations have been reported in the open literature to date. The present work presents an extensive experimental program of full-scale field tests carried out on a group of three steel pipe piles at the tourist port of La Spezia, Italy. Three typologies of dynamic tests are carried out at different level of force: impact load test, free vibration test, and forced vibration test. The piles are vibro-driven into marine soft clay, with a L-shaped plan layout, kept free at the head. Two test campaigns have been carried out, the first 1 week and the second 10 weeks after vibro-driving of the piles. The piles are instrumented with an unconventional technique for field tests in marine environment which includes accelerometers at the head of each pile, strain gages and pore pressure gages along the fully instrumented corner pile. The dynamic behaviour of the complex soil-water-pile system at different levels of force is discussed. In particular the response of the single pile, in terms of natural frequencies, damping and mode shapes of the first and second pile bending modes is presented. Effects of the input direction in the pile-to-pile interaction are also evaluated. The variation in time of the dynamic behaviour of the system (for the two campaigns), due to re-consolidation of the soil close to the pile subsequent to the vibrodriving, is observed. An average shear wave velocity of the upper soil is estimated from the time delays of the accelerometer signals recorded at the head of piles. The experimental results are then compared with numerical results obtained with different approaches: two 3-D finite element models are developed in ABAQUS, considering solid or shell elements for the piles, and calibrated on the basis of experimental results; and a 3-D model for the kinematic interaction analysis of pile groups, formulated by Dezi et al. (2009) is here specialized to simulate the tests of the experimental campaign.
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Monni, Francesco. "Materiali innovativi per il recupero strutturale del costruito storico: il basalto e l'idea delle cuciture continue per la muratura." Doctoral thesis, Università Politecnica delle Marche, 2012. http://hdl.handle.net/11566/242066.
Full textAbstract:
L’evoluzione tecnologica e lo sviluppo di tecniche di produzione hanno portato il mondo
delle costruzioni a poter fare affidamento su un repertorio di materiali da costruzione con
valenza strutturale ben lontano da quello conosciuto fino a qualche anno fa. In particolare,
dall’inizio degli anni Novanta hanno trovato spazio nell’edilizia i cosiddetti materiali
compositi, creati dall’unione di fibre (solitamente di carbonio, vetro o aramidiche) annegate
in una matrice (solitamente una resina). I compositi precedentemente venivano utilizzati
solo in quei settori dove era richiesta una elevata resistenza o rigidezza specifica e dove il
costo del materiale non costituiva un problema rilevante (applicazioni aeronautiche, navali,
industria sportiva, ecc.). Nel corso degli ultimi anni, in ambito civile, si è assistito alla
comparsa di nuove matrici e nuovi tipi di fibre. Tra i nuovi tipi di fibre vanno menzionate le
fibre (o meglio “mini-trefoli”) in acciaio, le fibre naturali (canapa, lino, ecc.) e le fibre di
basalto. In questo lavoro è stata posta l’attenzione proprio su queste ultime. Il basalto è una
roccia derivata dalla solidificazione della lava vulcanica con un punto di fusione di circa
1400°C, usata fin dall’antichità, per la sua durezza, per lastricare le strade. Una volta fusa e
riportata allo stato liquido, la roccia basaltica consente l’estrusione di filamenti continui di
esiguo spessore: le fibre di basalto. Con semplici lavorazioni le fibre di basalto possono
essere assemblate per realizzare prodotti destinati al mondo delle costruzioni, in particolare
barre e corde, che in questo lavoro saranno caratterizzate dal punto di vista fisico, chimico e
meccanico. In particolare le corde, per la loro estrema leggerezza e versatilità, sono il
prodotto che ha fornito lo spunto per un’innovativa applicazione delle stesse per il
consolidamento delle murature storiche. Dalla constatazione che una delle vulnerabilità più
pericolose per una muratura è la mancanza di monoliticità, nasce l'idea di conferire questa
importante caratteristica attraverso un sapiente gioco di trama e ordito, in cui elementi
flessibili in fibra di basalto tengono assieme i vari conci. La tecnica proposta e testata
attraverso test in laboratorio, in situ e successive analisi numeriche, ha l’obiettivo di
consolidare i pannelli murari, confinandoli e al tempo stesso collegandone le facce
attraverso cuciture continue flessibili. In pratica, un elemento continuo e flessibile cinge la
muratura sui due lati dopo averne attraversato lo spessore in più punti, proprio come se
venisse “cucita” dal “filo” di rinforzo. Il sistema così ideato integra ma non sostituisce o
trasforma la materia originaria. È reversibile e può essere messo in opera anche “a secco”.
In questo caso non contempla l’uso di sostanze tossiche o dannose per la salute, non
necessita di particolari accorgimenti per lo smaltimento dei residui delle lavorazioni o
all’atto della dismissione per fine servizio. Risulta così all’avanguardia sia dal punto di
vista della sostenibilità ambientale che della sicurezza dei lavoratori. È compatibile con il
supporto in muratura (la pietra che cuce la pietra), è rispettoso del minimo intervento
(impiegabile quindi su murature delle quali si voglia salvaguardare l’aspetto “faccia a
vista”, può essere localizzato anche nei giunti di malta). È economico: anche se applicato su
murature irregolari, prevede fasi di lavorazione e tempi di applicazione ridotti rispetto a
tecniche alternative, è durevole e con elevata resistenza al fuoco. Vantaggi, rispetto alle
tecniche oggi utilizzabili, che proiettano questo sistema come utilizzabile con profitto nel
campo del restauro e del consolidamento.Due to technology evolution, a lot of innovative techniques are today available in constructions field for structural purposes. In particular, from the early nineties, composite materials, created through the union between fibres (usually carbon, glass or aramidic ones) and matrix (usually a resin) have been used in building industry. Previously composites were used only in several fields such as automotive, aviation industry and sporting equipment, where great stiffness and strength are required and cost is not a problem. Recently, innovative reinforcing fibres, like steel, and basalt ones, are emerging in FRP field. This work focuses on basalt fibre products. Basalt is a natural material that is found in volcanic rocks originated from frozen lava. Continuous basalt fibers are obtained by melting basalt and are characterized by high modulus, heat resistance, good resistance to chemical attack and they seem to be a good alternative to glass fibers. Continuous basalt fibers can be processed with classic textile transformation to obtain also ropes, unlike other kinds of reinforcing fibers. This work presents a physical, chemical and tensile characterization of BFRP rods and BF ropes, in particular ropes are evaluated to be used in masonry strengthening. From the awareness that one of the worst structural defects of an historic masonry wall is the lack of monolithic behavior, arise the idea of a strengthening technique able to connect the several masonry elements, stitching them. The proposed technique, based on the reinforcement and connection of masonry component using basalt fiber ropes, is able to change the failure mode of masonry wall, exploiting material properties, and it is able to impart to masonry monolithic behavior. Compared to traditional techniques, best advantages are represented by the fact that the application is very fast (and so cheap), the material used (basalt) presents an high compatibility with masonry (stone stitches stone) and the intervention is almost totally reversible. Moreover it is invisible and so respectful of masonry original aspect, it improves but not replaces original materials and, finally, it is fire and chemical resistant. To assess the effectiveness of proposed technique, laboratory test (on “three-leaf” masonry samples) and in situ test (on rubble stone masonry) have been performed, above all that also FEM analysis has been developed to better understand experimental results.
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Carbonari, Sandro. "Seismic response of structures on pile foundations." Doctoral thesis, Università Politecnica delle Marche, 2009. http://hdl.handle.net/11566/242284.
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DOTTORE, ALEXANDRO. "FINITE ELEMENT FATIGUE ASSESSMENT OF STEEL TUBULAR JOINTS IN OFFSHORE STRUCTURES." Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1460427.
Full textAbstract:
Background: Fatigue analysis is a very complex process, which is still today not fully under-stood. This thesis numerically investigates the advantages and limitations of the employment of the Finite Element (FE) method in actual standard fatigue design procedure. Two studies are conducted to validate the SCF calculation and the application of Hot-Spot Stress (HSS) method to fatigue design.
Study I: The Stress Concentration Factor is a magnification factor introduced to account for geometrical or material discontinuities in structural joints. In these locations the stress may reach values several times higher than the nominal stress and may lead to the premature collapse of the structure when subjected to fatigue loading. However, current methodologies to compute the SCF cover only a limited number of joint types and configurations. The aim of this study is to investigate the SCFs in tubular joints through the application of empirical formulas and an extensive numerical analysis campaign. SCFs are assessed for several types of tubular joints and loading conditions according to current standards and literature. Obtained results are compared together to highlights the weaknesses and strengths of each approach and to investigate their implications for the design of tubular joints.
Study II: Fatigue is one of the most frequent causes of steel structures failures, particularly in offshore platforms. Thus, the fatigue life assessment is one of the most relevant procedures for the comprehensive evaluation of both the load-carrying capacity and service life of the structure. The standard fatigue procedure consists of the method of local stress, the so-called Hot-Spot Stress (HSS) applied on a global analysis model. HSS method consists in calculating the stress occurring in the cross sections of the whole elements and applying them a multiplying factor to account for the geometry of the detail. At present, the use of Finite Element makes possible looking for more accurate fatigue stress ranges calculation. This study presents fatigue assessment of representative types of tubular joints in welded offshore platform. Joint fatigue damages are calculated performing global and local FE analyses. The obtained results are com-pared together to evaluate the limits and advantages of the different approaches and model types.
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MORANDINI, CHIARA. "Integrated nonlinear modelling strategies for the seismic analysis of masonry structures." Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1460433.
Full textAbstract:
In the last decades, significant interest has raised in modelling and analysing the structural response of unreinforced masonry (URM) buildings. This aims at conceiving and designing effective interventions to reduce the vulnerability towards seismic actions. Studies based on costly structural testing are often limited to few benchmark cases, making numerical modelling an excellent option to extend experimental results and a valid solution for understanding URM structural behaviour. Advanced discrete models are widely employed among the available numerical strategies to predict the URM dynamic response, thanks to their ability to account for the heterogeneous nature of masonry and to simulate its behaviour up to the complete collapse. If, on the one hand, the low degree of idealisation of discrete models allows their employment for the extension of experimental tests, on the other hand, they require expert users, the definition of a large number of mechanical parameters and a high computational effort. This last drawback often limits the use of advanced discontinuum models in the engineering practice or for seismic risk studies, which require the execution of multiple analyses.
In this work, a modelling approach, based on the Applied Element Method (AEM), was combined with more simplified models to exploit the discrete model potential and overcome its limits. To this aim, the AEM was employed as a benchmark to calibrate/validate simplified modelling strategies, improving their reliability when compared to advanced model outcomes. In this context, AEM models were used as a reference to enhance the Equivalent Frame Model (e.g. the presence of irregular distribution of openings) and to validate a new strength criterion associated with the failure mechanism encountered in a new masonry typology. In the absence of a large suite of experimental tests exploring all the possible setup or configurations, the AEM can provide precious information. On the other hand, the AEM can help to investigate situations requiring a higher level of detail, such as the design of the timber retrofitting system analysed in this work. The ability of the AEM to simulate the structural behaviour up to the complete collapse was also used to investigate the effect of different percentages of ground floor opening on the dynamic response of Dutch terraced houses, performing benchmark analyses to calibrate SDOF models employed for the development of fragility functions associated with the different layouts. Finally, AEM models were employed for substructuring façade models of masonry buildings whose global response was effectively studied by equivalent frame models. The aim of the study was to predict the debris extent involved in the collapse of URM façades in case of earthquake loadings. Such an integrated numerical procedure allowed considering a large suite of seismic inputs, overcoming the time-consuming issue.
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MORANDINI, CHIARA. "Integrated nonlinear modelling strategies for the seismic analysis of masonry structures." Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1460429.
Full textAbstract:
In the last decades, significant interest has raised in modelling and analysing the structural response of unreinforced masonry (URM) buildings. This aims at conceiving and designing effective interventions to reduce the vulnerability towards seismic actions. Studies based on costly structural testing are often limited to few benchmark cases, making numerical modelling an excellent option to extend experimental results and a valid solution for understanding URM structural behaviour. Advanced discrete models are widely employed among the available numerical strategies to predict the URM dynamic response, thanks to their ability to account for the heterogeneous nature of masonry and to simulate its behaviour up to the complete collapse. If, on the one hand, the low degree of idealisation of discrete models allows their employment for the extension of experimental tests, on the other hand, they require expert users, the definition of a large number of mechanical parameters and a high computational effort. This last drawback often limits the use of advanced discontinuum models in the engineering practice or for seismic risk studies, which require the execution of multiple analyses.
In this work, a modelling approach, based on the Applied Element Method (AEM), was combined with more simplified models to exploit the discrete model potential and overcome its limits. To this aim, the AEM was employed as a benchmark to calibrate/validate simplified modelling strategies, improving their reliability when compared to advanced model outcomes. In this context, AEM models were used as a reference to enhance the Equivalent Frame Model (e.g. the presence of irregular distribution of openings) and to validate a new strength criterion associated with the failure mechanism encountered in a new masonry typology. In the absence of a large suite of experimental tests exploring all the possible setup or configurations, the AEM can provide precious information. On the other hand, the AEM can help to investigate situations requiring a higher level of detail, such as the design of the timber retrofitting system analysed in this work. The ability of the AEM to simulate the structural behaviour up to the complete collapse was also used to investigate the effect of different percentages of ground floor opening on the dynamic response of Dutch terraced houses, performing benchmark analyses to calibrate SDOF models employed for the development of fragility functions associated with the different layouts. Finally, AEM models were employed for substructuring façade models of masonry buildings whose global response was effectively studied by equivalent frame models. The aim of the study was to predict the debris extent involved in the collapse of URM façades in case of earthquake loadings. Such an integrated numerical procedure allowed considering a large suite of seismic inputs, overcoming the time-consuming issue.
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DOTTORE, ALEXANDRO. "FINITE ELEMENT FATIGUE ASSESSMENT OF STEEL TUBULAR JOINTS IN OFFSHORE STRUCTURES." Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1460428.
Full textAbstract:
Background: Fatigue analysis is a very complex process, which is still today not fully under-stood. This thesis numerically investigates the advantages and limitations of the employment of the Finite Element (FE) method in actual standard fatigue design procedure. Two studies are conducted to validate the SCF calculation and the application of Hot-Spot Stress (HSS) method to fatigue design.
Study I: The Stress Concentration Factor is a magnification factor introduced to account for geometrical or material discontinuities in structural joints. In these locations the stress may reach values several times higher than the nominal stress and may lead to the premature collapse of the structure when subjected to fatigue loading. However, current methodologies to compute the SCF cover only a limited number of joint types and configurations. The aim of this study is to investigate the SCFs in tubular joints through the application of empirical formulas and an extensive numerical analysis campaign. SCFs are assessed for several types of tubular joints and loading conditions according to current standards and literature. Obtained results are compared together to highlights the weaknesses and strengths of each approach and to investigate their implications for the design of tubular joints.
Study II: Fatigue is one of the most frequent causes of steel structures failures, particularly in offshore platforms. Thus, the fatigue life assessment is one of the most relevant procedures for the comprehensive evaluation of both the load-carrying capacity and service life of the structure. The standard fatigue procedure consists of the method of local stress, the so-called Hot-Spot Stress (HSS) applied on a global analysis model. HSS method consists in calculating the stress occurring in the cross sections of the whole elements and applying them a multiplying factor to account for the geometry of the detail. At present, the use of Finite Element makes possible looking for more accurate fatigue stress ranges calculation. This study presents fatigue assessment of representative types of tubular joints in welded offshore platform. Joint fatigue damages are calculated performing global and local FE analyses. The obtained results are com-pared together to evaluate the limits and advantages of the different approaches and model types.
42
DOTTORE, ALEXANDRO. "FINITE ELEMENT FATIGUE ASSESSMENT OF STEEL TUBULAR JOINTS IN OFFSHORE STRUCTURES." Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1460432.
Full textAbstract:
Background: Fatigue analysis is a very complex process, which is still today not fully under-stood. This thesis numerically investigates the advantages and limitations of the employment of the Finite Element (FE) method in actual standard fatigue design procedure. Two studies are conducted to validate the SCF calculation and the application of Hot-Spot Stress (HSS) method to fatigue design.
Study I: The Stress Concentration Factor is a magnification factor introduced to account for geometrical or material discontinuities in structural joints. In these locations the stress may reach values several times higher than the nominal stress and may lead to the premature collapse of the structure when subjected to fatigue loading. However, current methodologies to compute the SCF cover only a limited number of joint types and configurations. The aim of this study is to investigate the SCFs in tubular joints through the application of empirical formulas and an extensive numerical analysis campaign. SCFs are assessed for several types of tubular joints and loading conditions according to current standards and literature. Obtained results are compared together to highlights the weaknesses and strengths of each approach and to investigate their implications for the design of tubular joints.
Study II: Fatigue is one of the most frequent causes of steel structures failures, particularly in offshore platforms. Thus, the fatigue life assessment is one of the most relevant procedures for the comprehensive evaluation of both the load-carrying capacity and service life of the structure. The standard fatigue procedure consists of the method of local stress, the so-called Hot-Spot Stress (HSS) applied on a global analysis model. HSS method consists in calculating the stress occurring in the cross sections of the whole elements and applying them a multiplying factor to account for the geometry of the detail. At present, the use of Finite Element makes possible looking for more accurate fatigue stress ranges calculation. This study presents fatigue assessment of representative types of tubular joints in welded offshore platform. Joint fatigue damages are calculated performing global and local FE analyses. The obtained results are com-pared together to evaluate the limits and advantages of the different approaches and model types.
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PATTON, ALESSIA. "Advanced isogeometric methods with a focus on composite laminated structures." Doctoral thesis, Università degli studi di Pavia, 2021. http://hdl.handle.net/11571/1431634.
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CASTROGIOVANNI, ALFREDO. "Reduced Order Homogenization for Multiscale Analysis of Nonlinear Composites." Doctoral thesis, Università degli studi di Pavia, 2021. http://hdl.handle.net/11571/1447832.
Full textAbstract:
Heterogeneous materials are nowadays used in several fields of structural engineering.
Such materials, regarded as composites, have a heterogeneous microstructure
in which two or more constituents are combined in order to reach
improved mechanical properties. Most of the composites include constituents
characterized by a nonlinear behaviour, hence, it is important to consider the
inelastic phenomena arising at the microscale, to accurately predict the macroscopic
response of the heterogeneous material.
A modeling approach allowing for the heterogeneous nature of the composite to
be considered during the design process is provided by the Multiscale Analysis,
in which both the macroscopic scale and the microscopic scale are involved. At
the microscale, a Unit Cell, being a representaive sample of the heterogeneous
nonlinear material, is studied in order to derive the behaviour of an equivalent
homogeneous macroscopic material. In the scale transition process, usually regarded
as homogenization, efficient numerical tools are needed in order to reduce
the computational cost due to the large quantity of internal variables, coming
from the evaluation of the elastoplastic material models at the microscopic level.
Reduced Order Models (ROM) are introduced with the aim of lowering the number
of internal variables of the problem and to provide accurate solutions with
reasonable computational cost and time.
This thesis is mainly dedicated to the development of a ROM for the homogenization
of nonlinear heterogeneous materials; starting from the Hashin-Shtrikman
analytical homogenization scheme, a piecewise uniform distribution of the microscopic
quantities is assumed, and thus, the proposed ROM is referred as
PieceWise Uniform Hashin-Shtrikman (PWUHS) technique. In particular, the
PWUHS is developed for the solution of homogenization problems of nonlinear
composites and extended to Mises plasticity with linear hardening.
Numerical results demonstrate the accuracy of the proposed homogenization
scheme, which is compared to the well known PieceWise Uniform Transformation
Field Analysis (PWUTFA) in order to investigate the similarities and the
advantages of both reduced order models. PWUHS is implemented in the framework
of Multiscale Analysis for studying the response of auxetic composites and
numerical results are compared to the experimental counterpart to assess the
efficiency of the proposed multiscale scheme.
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MURER, MAURO. "Computational Fluid Dynamics simulations of Laser Metal Deposition process exploring open source software." Doctoral thesis, Università degli studi di Pavia, 2021. http://hdl.handle.net/11571/1447833.
Full textAbstract:
Laser Metal Deposition (LMD) is an innovative technology adopted in Additive Manufacturing (AM) processes and its use is becoming more and more popular in various application fields, such as part manufacturing, repair, and prototype fabrication. This technique is capable of creating several layers of solidified material, by the simultaneous delivery of metal powders and the laser beam, and offers an effective way to produce complicated geometries thanks to its high flexibility. However, complex physical phenomena occur during the additive process, which have a great impact on the success of the process, and many of these have yet to be fully understood. With the aim of shedding light on these aspects, a detailed numerical study, focused on LMD technology, will be conducted using three-dimensional models based on Com- putational Fluid Dynamics (CFD).
The particle flow problem regarding the coupling between the fluid phase (i.e., the carrier gas) and the solid phase (i.e., a metallic material powder) is first investigated using OpenFOAM, an open source software widely used in the CFD community. In particular, two different numerical approaches are investigated: the first approach is based on an Eulerian method to describe the carrier gas flow combined with a Lagrangian method to describe the particle flow (LE method), and the second approach is based on a pure Eulerian method to model both the carrier gas and the particle flow (EE method). Simulations results show the main features of the two approaches considered in terms of reliability in reproducing the key geometrical and physical features of the LMD process, together with a comparison with experimental evidences.
On the other hand, the thermal problem, that describes the interaction between particles flow and the laser beam, play a crucial role and cannot be neglected. For this purpose, the time-dependent Navier-Stokes equations for incompressible flows are coupled with the energy equation in order to represent the temperature field, whereas the Lagrangian description of the particle dynamic is enriched accounting the thermal evolution, and the consequent phase changing of the metallic powder due to the particle-laser interaction. This model is developed in a C++ in-house code using the open source Finite Element library deal.II and it is validated through consolidated results available in the literature. Furthermore, different schemes able to solve the Navier-Stokes equations, coupled with the heat transfer equation, are implemented and compared, so as to prove both accuracy and efficiency.
Then, with the aim of investigating the LMD process in detail, and in particular the thermal behaviour of the powder exiting from the nozzle, a sensitivity analysis is performed in terms of the parameters most meaningful from a technological viewpoint, i.e., the nozzle inclination, the carrier gas and powder flow rate, and the laser power. The results of such an analysis show that it is possible to predict both the configuration and the energy distribution that character- izes the flow of the powder leaving the nozzle until it reaches the substrate. In particular, the influence of both laser power and nozzle geometry to phase change conditions of powder flux are analyzed in order to improve the set up of the printing process, which can lead to increased productivity and less material waste.
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LAKSHMANAN, KAYALVIZHI. "Predictive Maintenance of an External Gear Pump using Machine Learning Algorithms." Doctoral thesis, Università degli studi di Pavia, 2021. http://hdl.handle.net/11571/1447613.
Full textAbstract:
The thesis describes a novel computational strategy of Predictive Maintenance (fault diagnosis
and fault prognosis) with ML and Deep Learning applications for an FG304 series external gear
pump, also known as a domino pump. Due to the unavailability of a sufficient amount of
experimental data, a novel approach of generating a high-fidelity in-silico dataset via a
Computational Fluid Dynamic model of the gear pump in a healthy and various faulty working
conditions (e.g., clogging, radial gap variations, viscosity variations, etc.). The synthetic data
generation technique is implemented by perturbing the frequency content of the time series to
recreate other environmental conditions. These synthetically generated datasets are used to train
the underlying ML metamodel. In addition, various types of feature extraction methods considered
to extract the most discriminatory information from the data. For fault diagnosis, three types of ML
classification algorithms are employed, namely Multilayer Perceptron (MLP), Support Vector
Machine (SVM) and Naive Bayes algorithms. For prognosis, ML regression algorithms, such as
MLP and SVM, are utilised. Hyper-parameters of the ML algorithms is optimised with a staggered
approach. In addition, a real case study of fault diagnosis and fault prognosis of an external gear
pump considering noisy measurements to understand the sensitivity of the employed ML
algorithms by adding noise on the training dataset and test dataset. A series of numerical examples
are presented, enabling us to conclude that for fault diagnosis, the use of wavelet features and a
MLP algorithm can provide the best accuracy and for fault prognosis, the use of MLP algorithm
provides the best prediction results.
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MURUGAN, VARUN. "Optimized Material Deposition for Extrusion-Based Additive Manufacturing of Structural Components." Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1464786.
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MORANDINI, CHIARA. "Integrated nonlinear modelling strategies for the seismic analysis of masonry structures." Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1460435.
Full textAbstract:
In the last decades, significant interest has raised in modelling and analysing the structural response of unreinforced masonry (URM) buildings. This aims at conceiving and designing effective interventions to reduce the vulnerability towards seismic actions. Studies based on costly structural testing are often limited to few benchmark cases, making numerical modelling an excellent option to extend experimental results and a valid solution for understanding URM structural behaviour. Advanced discrete models are widely employed among the available numerical strategies to predict the URM dynamic response, thanks to their ability to account for the heterogeneous nature of masonry and to simulate its behaviour up to the complete collapse. If, on the one hand, the low degree of idealisation of discrete models allows their employment for the extension of experimental tests, on the other hand, they require expert users, the definition of a large number of mechanical parameters and a high computational effort. This last drawback often limits the use of advanced discontinuum models in the engineering practice or for seismic risk studies, which require the execution of multiple analyses.
In this work, a modelling approach, based on the Applied Element Method (AEM), was combined with more simplified models to exploit the discrete model potential and overcome its limits. To this aim, the AEM was employed as a benchmark to calibrate/validate simplified modelling strategies, improving their reliability when compared to advanced model outcomes. In this context, AEM models were used as a reference to enhance the Equivalent Frame Model (e.g. the presence of irregular distribution of openings) and to validate a new strength criterion associated with the failure mechanism encountered in a new masonry typology. In the absence of a large suite of experimental tests exploring all the possible setup or configurations, the AEM can provide precious information. On the other hand, the AEM can help to investigate situations requiring a higher level of detail, such as the design of the timber retrofitting system analysed in this work. The ability of the AEM to simulate the structural behaviour up to the complete collapse was also used to investigate the effect of different percentages of ground floor opening on the dynamic response of Dutch terraced houses, performing benchmark analyses to calibrate SDOF models employed for the development of fragility functions associated with the different layouts. Finally, AEM models were employed for substructuring façade models of masonry buildings whose global response was effectively studied by equivalent frame models. The aim of the study was to predict the debris extent involved in the collapse of URM façades in case of earthquake loadings. Such an integrated numerical procedure allowed considering a large suite of seismic inputs, overcoming the time-consuming issue.
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LAORENZA, Carmine. "Sulla prevenzione dal rischio sismico del costruito storico." Doctoral thesis, Università degli studi del Molise, 2012. http://hdl.handle.net/11695/66236.
Full textAbstract:
Il tema della tutela del paesaggio alla luce dei più recenti sviluppi della normativa in materia presenta aspetti di notevole complessità, che richiede necessariamente un approccio interdisciplinare. Tra i beni ambientali soggetti a tutela, come è noto, sono ricompresi le ville, i giardini, i parchi, le bellezze panoramiche e i “complessi di cose immobili che compongono un caratteristico aspetto avente valore estetico e tradizionale” (legge del 29 giugno 1939 n° 1497, art. 1, comma 3).
L’ultima categoria di beni, insieme alle ville, rivela tra l’altro un ruolo molto importante di quelle discipline tecniche focalizzate sulle prestazioni strutturali e funzionali del patrimonio costruito e si interessano di valutare l’impatto dei rischi naturali, come quello sismico, sui beni oggetto di tutela. Gli eventi occorsi negli ultimi anni hanno, infatti, evidenziato da un lato l’estrema vulnerabilità di alcune classi di costruzioni all’azione sismica, dall’altro la grande sensibilità dell’opinione pubblica al tema della sicurezza degli ambienti urbani, del territorio e della conservazione integrata dei beni tutelati.
Il lavoro di tesi, muovendo da tali osservazioni, si colloca nell’ambito disciplinare ampio dell’Ingegneria Sismica ed ha come tema portante proprio la protezione dal rischio sismico del costruito storico, dunque della tutela di uno degli elementi che compongono uno specifico paesaggio, “il cui carattere deriva dall'azione di fattori umani e dalle loro interrelazioni”.
Lo spunto di partenza è costituito dai paesaggi caratterizzati dagli Edifici Monumentali, i quali, per legge, vanno tutelati dal rischio sismico e per i quali sono disponibili gli strumenti necessari, con l’obiettivo di estendere gli strumenti a tutto il costruito, per “Integrare il paesaggio nelle politiche … che possono avere un'incidenza diretta o indiretta sul paesaggio”. Lo studio è rivolto alle procedure di analisi di vulnerabilità sismica su scala territoriale.
Il lavoro tiene conto delle problematiche di carattere territoriale, relative sia al territorio nazionale che specificamente per la regione Molise, cercando di evidenziare la rilevanza che tali problematiche, nell’ambito di processi integrati di protezione e salvaguardia del paesaggio, possono rivestire.Landscape protection is a complex task, which requires an interdisciplinary approach, especially after the recent code developments. Such a protection concerns villas, gardens, parks, natural beauties and all those things having aesthetic and traditional relevance (L. 1497/1939). In this framework it is worth pointing out the primary role of technical disciplines which study structural and functional performance of existing buildings, including the effects of natural hazards such as earthquakes. The seismic events occurred in the last years have remarked both the extreme vulnerability of certain classes of buildings and an increasing attention to this issue in the general public. This thesis is therefore focused on Earthquake Engineering and seismic protection of historical buildings, that is the one element of a specific landscape protection "whose character derives from the human factors and their interrelationships”. The attention, in particular, is focused on monumental buildings, which must be protected from seismic risk, as required by the codes. The available tools can be extended to all existing buildings "to integrate the landscape in policies... which can have a direct or indirect effects on landscape”. The study concerns procedures for seismic vulnerability assessment at a territorial scale. The work takes into account territorial issues, both at the national and regional level, trying to highlight their relevance in the context of landscape protection.
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LERONNI, ALESSANDRO. "Modeling the electrochemo-poromechanics of ionic polymer metal composites and cell clusters." Doctoral thesis, Università degli studi di Brescia, 2021. http://hdl.handle.net/11379/544093.
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