1,721,274 research outputs found
Design and modelling strategy for cold-formed steel exoskeletons for the seismic-energy retrofit of reinforced concrete structures
No full textRecent seismic events have highlighted the vulnerability of reinforced concrete (RC) buildings constructed before the enforcement of seismic design codes. This study is focused on a cold-formed steel exoskeletons, known as the Resisto 5.9 Tube system, used to enhance both seismic and thermal performance of existing structures. The main focus is the application of a simplified design and modelling strategy to elementary reinforced concrete structures with different heights. The design strategy is aimed to optimize the elements of Resisto 5.9 Tube according to the specific building under investigation. The modelling strategy is developed to reduce the computational effort when implementing the reinforcement system in structural software without negatively affecting the reliability of the results
Una strategia di Text Mining basata su regole di associazione
No full textQuesto lavoro propone una strategia per affrontare l'analisi di corpora di grandi dimensioni che presentino una strutturazione interna, con il duplice vantaggio, da un lato, di un notevole risparmio del peso computazionale dell'analisi e, dall'altro, di introdurre elementi relativi al contesto in cui le singole parole sono utilizzate. La strategia si avvale di un modesto intervento preliminare da parte di esperti al fine di pervenire, grazie all'utilizzo di metodi statistici di segmentazione, alla categorizzazione del testo e alla costruzione, sulla base di un training set, di regole di associazione, Queste regole, applicate all'intero corpus, consentono si sottoporre ad analisi soltanto i frammenti individuati come di interesse diretto per gli obiettivi conoscitivi perseguit
Hardness Tests on New and Existing Steel Structures
No full textNon-destructive tests represent a valuable resource to achieve a higher knowledge of existing structures without excessively compromising its safety with the sampling operations. In this framework, the Leeb hardness test allows to measure the hardness value of steel elements directly in-site with portable devices without taking samples from the structure for laboratory tests. The purpose of the research is to find a relationship between the Leeb hardness values and the tensile strengths of steel elements to obtain reliable results that can allow to disseminate the use of this test type
Integrated seismic-energy retrofit systems for preventing failure of a historical RC school building: Comparison among metal lightweight exoskeleton solutions
No full textItalian built heritage is highly vulnerable due to old public and private buildings designed without recent seismic and energy regulations. In particular, school buildings represent a critical typology that should be retrofitted to guarantee safety and comfort to the users. In this framework, interventions from building outside able to avoid interruption of school activities should be required. A solution to solve this issue can be found in the retrofit solution with exoskeletons. In this scenario, the paper presents the comparison among three similar solutions of metal lightweight exoskeletons for the integrated seismic-energy retrofit of a RC school building assumed as a case study. The RC structure of the school is firstly modelled with a finite element software and then subjected to pushover analysis before and after retrofit interventions to assess the benefit of each exoskeleton solution. The comparisons among intervention techniques are made in terms of the seismic safety index (ζE) provided by the Italian technical standard. The results show the more or less efficacy of the different inspected systems, even if integrative local interventions are needed to reach the minimum safety index (0.60) required for school buildings. As a conclusion, these novel light metal exoskeletons have proven to be efficient retrofitting systems for residential buildings or even for school buildings with regular façades and plan layouts
Leeb hardness tests for mechanical characterisation of carpentry steels
No full textSeismic vulnerability assessment requires a sufficient knowledge of existing buildings. In order to preserve existing metal structures, studies on non-destructive tests assume fundamental importance. The Leeb test performed with a portable tester is herein investigated as a method to indirectly estimate tensile strength of carpentry steels by measuring the surface hardness. The current work aims to identify a theoretical correlation between Leeb hardness values and the tensile strengths of steel deriving from direct tensile tests. Two sets of samples were analysed: existing steel profiles and new ones. The experimental results achieved were compared with the standard curves in the guidelines to evaluate the effectiveness of the latter theoretical provisions to foresee the mechanical behaviour of carpentry steels
Seismic Design and Analysis of a Cold-Formed Steel Exoskeleton for the Retrofit of an RC Multi-Story Residential Building
Full text linkThe awareness of the vulnerability of existing structures under both seismic and energy perspectives highlights the need for integrated retrofit solutions that combine structural and thermal enhancements. From this perspective, this study explored the efficacy of the Resisto 5.9 Tube system, which is a seismic retrofit solution for masonry and reinforced concrete (RC) structures that also improves the energy performance by integrating a thermal coat integrated within its basic steel framework. This research involved application to a RC building of a design procedure specifically developed for this system that was aimed at facilitating its adoption by designers involved in seismic retrofitting analysis. After designing the system components, nonlinear static analyses were performed using finite element software to compare the building’s seismic performance before and after the application of the Resisto 5.9 Tube. The results demonstrate a significant increase in the seismic safety coefficient ζE from 0.26 to 0.42, which proved the potential of this intervention to enhance the seismic safety of existing RC buildings
A text mining strategy based on local contexts of words
No full textAim of the paper is to propose a Text Mining strategy based on statistical tools, which make more efficient the extraction of information buried in massive quantities of documents. Usually, in Text Mining procedures (such as in textual data analyses) we deal with a corpus consisting of a set of documents. In order to build the data structure to be processed, each document is encoded in a document vector, according to the bag-of-words model, which associates words and their frequencies for the given document. Documents are considered as a whole. The proposed mining strategy identifies interesting sentences in the corpus we deal with, where to concentrate the knowledge extraction. The sentence interest will depend on the researcher’s objective. The proposed procedure is useful when we are interested in local contexts for words. Prior information, i.e. expert knowledge, is included, as an input for the procedure, but differently to content analysis, the key-word system is automatically built. The strategy can be applied in any case we can introduce information for partitioning documents in lower order grammatical units (e.g. sentences, but also paragraphs, etc.). The mining procedure consists in two steps: first of all the Text Categorisation, i.e. the recognition of the interesting sentences, by means of a statistical segmentation procedure, and then the knowledge extraction from the identified sub-texts. The procedure first step produces association rules useful in filtering e-mail, chat, or Web access, too. The paper aims at contributing to the day-by-day wider literature on Text Mining, devoted to go beyond the "bag-of-words" model of structuring the data set in document vectors, enhancing the role of a statistical perspective. An application on Italian on-line job offers ends the paper, showing the effectiveness of the proposal
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