1,720,977 research outputs found
Soluzioni integrate con componenti in legno per la protezione sismica del patrimonio architettonico
No full textI campi dell’Ingegneria e del Recupero del patrimonio esistente hanno visto, negli ultimi anni, una crescita costante dell’attenzione verso le tematiche della protezione sismica e, nel contesto dei cambiamenti climatici in atto, della sostenibilità, vista l’ormai palese necessità di migliorare, da tale punto di vista, il panorama delle costruzioni e del costruito, sia in termini di materiali impiegati che di consumi.
In tale contesto, le componenti costruttive in legno sono state rivalutate grazie alle loro ottime caratteristiche strutturali accompagnate da una massa ridotta, che le rendono idonee all’impiego in zone sismiche, e alla loro sostenibilità, sia in funzione della valutazione del ciclo di vita, che delle proprietà di isolamento termico. Tra queste, il cosiddetto Cross Laminated Timber (CLT) ha avuto un notevole successo, legato anche alla sua velocità di assemblaggio, che si basa su connessioni a secco in acciaio. Tuttavia, queste sono anche legate a possibili riduzioni del comfort acustico dell’edifico, il cui superamento viene in genere realizzato mediante l’interposizione di una guaina elastomerica isolante.
L’attività di ricerca, sperimentale e numerica, presentata in questa tesi, riguarda l’implementazione di nuove soluzioni integrate in legno (CLT), da implementarsi sia nei sistemi di nuova costruzione che all’interno del patrimonio architettonico esistente. Il tema dell’integrazione ha una duplice valenza, sia dal punto di vista delle prestazioni (strutturali, energetiche, acustiche), che della eventuale collaborazione con altri sistemi esistenti.
Le prestazioni delle connessioni, tradizionali e ad isolamento acustico, sono caratterizzate sperimentalmente a scala locale e a scala globale, mediante prove distruttive a taglio e prove di identificazione dinamica su campioni a scala di edificio reale. La calibrazione di modelli numerici su tali prove ha permesso di indagare l’interazione tra la scala locale ed il comportamento globale dell’edificio.
A partire dalla caratterizzazione locale delle connessioni, è stato progettato un sistema di collegamento dissipativo, la cui efficacia è stata valutata mediante l’applicazione numerica ad una parete di riferimento da letteratura.
La conoscenza acquisita circa le componenti in legno, e la loro simulazione, ha permesso di validare una metodologia per il recupero di edifici esistenti in muratura. Questa è basata sulla valutazione delle prestazioni integrate strutturali ed energetiche di pareti accoppiate legno-muratura e la loro estensione ad un edificio. Tale approccio è stato definito Nested Building ed applicato ad un edificio esistente in muratura del XVII secolo, la cosiddetta ‘Cattedra’ nella zona alpina veneta, oggetto di numerose trasformazioni ed interventi nel corso degli anni.The research activities of Engineering and Restoration have recently moved towards the topics of seismic protection of buildings and selection of sustainable materials, from both hygrothermal performances (i.e., energy consumptions) and material points of view (e.g., Life Cycle Assessment).
In such a contest, timber components have gained a renewed interest, thanks to their optimal structural characteristics per low mass, which make them suitable for seismic prone areas, and sustainability. Among these, Cross Laminated Timber (CLT) has a strong success in the construction market, mainly due to the dry assembling technique of such prefabricated panels, based on dry steel fasteners and brackets. Unfortunately, these are also related to possible reductions of acoustic comfort. To overcome it, insulation of joints is usually applied.
The experimental and numerical research activity discussed in this Doctoral Thesis concerns the implementation of new timber-based integrated solutions, to be adopted in both new systems or built heritage. Integration theme concerns a double value, with reference to multiple performances addressed (structural, hygrothermal or acoustic) and potential embedment within other (existing) systems.
Traditional and insulated connections have been characterized by junction-scale and building-scale specimens, through shear testing and dynamic identification, respectively. The updating of numerical model by mode parameters has led to the detection of joints influence on the overall behavior.
Following, based on such local characterization, a yielding connection system has been designed, and its effectiveness assessed by pier-scale cyclic simulations.
The acquired knowledge about timber (CLT) components and their simulation has led to the validation of a methodology for the refurbishment of masonry existing buildings. This is based on the assessment of integrated hygrothermal-structural performances of coupled CLT-masonry walls, and the further extension to a structural system. Such approach was named ‘Nested Building’ and applied to a masonry construction of XVII century, the so-called ‘Cattedra’ in the Italian Alpine region, which underwent various alterations during years
Impact of sound-insulated joints in the dynamic behavior of Cross-Laminated Timber structures
Full text linkCross-Laminated Timber (CLT) has gained an increasing success and widespread diffusion among
wood products. Due to the novelty of the components and the dry-assembling techniques, certain
aspects of its behavior and performance remain unexplored; among these, the use of soundinsulated joints and brackets, along with their possible drawbacks on mechanical performance.
In this paper the authors discuss the results of dynamic identification (ID) tests carried out on
twin full-size CLT mockups (two-story), one of which was furnished with sound-insulation details
based on an elastomeric interlayer. Ambient (white noise and random excitations) and forced
vibration (mass shaker) tests were carried out to identify modal parameters.
The paper mainly aims at: i) assessing potential differences in the overall dynamic behavior of
the two mockups, likely due to the introduction of acoustic insulation, ii) detecting possible
drawbacks of insulation layers on mechanical performances, iii) increasing the knowledge about
dynamics of CLT structures.
The results of Operational Modal Analysis (OMA) are presented and the variations in the dynamics between the mockups are discussed. The construction of finite element (FE) models and
their calibration – with joint properties variations – are then presented. The outcomes revealed a
drop of modal frequencies values (at least 20 %) upon the introduction of elastomeric insulation,
whilst no significant alteration was observed in the mode shapes. Model updating based on the FE
models demonstrated that the dynamic response and the frequency variations were mostly
associated with wall-to-wall and wall-to-diaphragms joints, and hold-down connections
Numerical Prediction of the Seismic Behavior of Reassembled Columns in Ancient Structures: An Anastylosis Model for the Temple of Apollo Pythios in Gortyn (Crete)
Full text linkThe Temple of Apollo Pythios in Gortyn (Crete, Greece) dates back to the mid-7th century BC. The temple underwent several transformations and an ultimate destruction over time that resulted in the current remains of a Roman colonnade composed of six fragmented stone columns lying on the ground within the naos. In addition, the region was struck by several earthquakes which contributed to the various changes. The analysis of the fragments composing the column portions and their geometric features provided a possible outline for their standing repositioning. Based on the current seismic hazard of the region, a predictive numerical model of the colonnade in the anastylosis conditions suggested the need for proper connections between the fragments and the bases to ensure their overall conservation as a compound structure. The comparison of various configurations of intervention and the simple superimposition of the fragments also provided details on the accomplishment of minimal and compatible solutions
AN INTEGRATED APPROACH AIMED AT THE PROTECTION OF CULTURAL HERITAGE: FROM THE GEOMATIC SURVEY TO HBIM AND AR REPRESENTATION OF VILLA PISANI (STRA, ITALY)
Full text linkRepair and conservation of masonry structures
No full textNumerical modeling of repair and strengthening techniques aimed at improving the mechanical behavior of masonry structures is a challenging task. The complexity of proper models to represent the great variability of existing masonry types and their constituent materials, the variety of aggregations in types of construction, and their possible current deteriorated state are combined with the uncertainties of interventions in terms of design, installation, and effectiveness. According to the main parameters characterizing common interventions on masonry constructions, this chapter describes the modeling strategies applicable to a series of enhancing techniques to reestablish overall collaboration among building components and then to repair and strengthen structural elements. The techniques are applied one by one, and then in combination, in order to have a proper overview of the possibilities of intervention and their effects on building behavior. Examples of the application of such a process on buildings damaged by earthquakes are provided, and the results obtained by equivalent frame and finite element numerical approaches are compared
Dynamic behavior of a two-storey cross laminated timber mockup
No full textTimber constructions have gained an increasing attention in the last years, due to the limited installation time and the reduced expertise in manpower required, since panels assemblage is mainly based on dry mounting techniques. Among these, Cross Laminated Timber (CLT) products are extensively used in constructions, as they allow to overcome the main weaknesses of hardwood artifacts. Moreover, CLT components are also being tested within the restoration and re-use of existing buildings. Since these timber products are relatively new in the construction market, experimental data and site investigations are still limited and some aspects still unknown. Among the many, dynamic characterization of CLT structures, and related model updating, is rare in literature. In such a context, an experimental campaign aimed at assessing the linear dynamic behavior of CLT structures was carried out. A building-scale specimen (mockup) was constructed; it was made of C24 CLT walls and diaphragms (floor and roof) with 10- and 14-cm thick panels, respectively, connected through steel brackets and screws. The mockup was investigated via dynamic identification tests, by implementing 12 piezoelectric accelerometers, i.e., 4 on the first floor and 8 on the roof. The experimental characterization was aimed at: (i) assessing the structural dynamic behavior and identifying the role of structural details on it; (ii) evaluating the experimental stiffness, compared to analytical predictions. At last, a finite element (FE) model was implemented and updated based on the experimental outcomes
LA CLASSIFICAZIONE IN TIPOLOGIA A E B DEGLI ELEMENTI IN CLT SECONDO LA UNI EN ISO 12354-1
No full textLa norma UNI EN ISO 12354-1 prevede l’utilizzo di differenti metodologie di calcolo per la valutazione della trasmissione laterale a seconda del comportamento vibro-acustico delle strutture edilizie, la norma le classifica in tipologia A e B. Alcuni elementi costruttivi, sebbene siano composti dallo stesso materiale, possono appartenere alla prima o seconda tipologia, in funzione della tecnologia di assemblaggio o posa in opera. I pannelli in CLT, genericamente appartenenti alla tipologia A, possono in alcuni casi comportarsi come elementi di tipo B. Il presente studio tratta alcuni di questi differenti casi
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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