1,721,564 research outputs found
Investigation strategy for structural assessment of historic towers
Full text linkHistorical masonry towers are relevant architectural heritage often in a strategic position within city centres. Their height and position require specific controls in order to define the state of preservation. The paper describes the investigation procedures developed by the authors in selected case studies. According to the timing and to the complexity of the structure, the approach requires preliminary visual inspections, geometric, crack pattern survey supplemented by historical research and stratigraphic survey. Operational modal testing evaluates the overall structural behaviour, indicating eventual local (or global) problems to study in depth by monitoring or further local tests. Emergency operations, such as controls after earthquakes, could require prompt procedures. In this case, the combination of visual inspection, geometric and damage survey with dynamic testing is a reliable procedure for structural assessment. Additional investigation increases the knowledge of local problems or gives information for further activity such as structural modelling. For instance, relevant data are the evaluation of the masonry quality or the control of the local state of stress to estimate through non-destructive or minor destructive testing in selected positions. Nevertheless, such activities require accurate projects of the investigation too, planning and localising several tests in order to solve the problems detected in the preliminary steps of the diagnosis process
Development and application of automated OMA algorithms
Full text linkWithin the contest of vibration-based monitoring, the paper summarizes the conceptual development of automated procedures of modal parameter estimation (MPE) and modal tracking (MT). The performance of the proposed algorithms is demonstrated using data collected both in single data-sets and over a period of continuous monitoring. The MPE process, based on the automated interpretation of the stabilization diagram associated to any parametric identification methods, is exemplified by using the SSI-Cov technique and consists of three key steps: (1) filtering a high number of spurious poles in the stabilization diagram (2) clustering process and (3) improving the accuracy of the estimates. Eventually, the mean modal parameters are computed for each clustered mode. The MT task is based on the definition of: (a) a pre-selected list of baseline modes with adaptive thresholds and (b) a dynamic reference list of modes associated to fixed thresholds
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
Estimating the Tensile Force in Ancient Metallic Tie-Rods from Vibration Tests
No full textOne of the distinctive characteristics of the Milan Cathedral is the presence of iron ties under the vaults of all 5 naves: those tension bars date back to the age of construction and still have an important role in supporting the lateral thrust exerted by vaults and arches.During the maintenance interventions preceding EXPO 2015, almost all the tie-rods of the cathedral underwent visual inspection, geometric characterization and hammer tests to evaluate their dynamic characteristics. After a brief summary of the experimental procedures, the paper focuses on presenting and exemplifying the structural identification approach adopted in the vibration-based assessment of the tensile force in the metallic ties. The presented procedure differs from the one proposed by Tullini and Laudiero (2008) since: (a) the Young's modulus of the metallic material is assumed to be unknown and (b) the resonant frequencies of higher modes are used to solve the inverse problem.The application of the proposed procedure is mainly exemplified with reference to the tension bars exhibiting the higher stress level (larger than 100 MPa) as those elements are now permanently instrumented with vibrating wire extensometers. Selected results from the long-term monitoring of the tie-rods are briefly discussed as well
One-Year Dynamic Monitoring the Main Spire of the Milan Cathedral
No full textOne of the most remarkable structural elements characterizing the Milan Cathedral is its main spire, reaching the height of about 108 m and supporting the statue of the Virgin Mary. The Main Spire, built in Candoglia marble and completed in 1762, is about 40 m high and stands on the tiburio of the cathedral (i.e., the prismatic structure with octagonal base built around the main dome). The spire consists of a central column which is connected through a spiral staircase to 8 perimeter columns, with each column being stiffened by a flying buttress. The structural arrangement is completed by (i) metallic clamps and dowels, connecting the marble blocks, and (ii) metallic rods, connecting the perimeter columns to the central core. A large monitoring system has been recently designed and installed in the Milan Cathedral, aimed at enhancing the knowledge and assisting the condition-based structural maintenance of the historic building. The new monitoring system includes temperature sensors and seismometers (electro-dynamic velocity sensors) at 3 levels of the Main Spire as well as a weather station at the top of the same spire. After a concise historic background on the Main Spire of the Milan Cathedral and the description of the sensing devices installed in this sub-structure, the paper focuses on the dynamic characteristics of the spire and their evolution during the first year of monitoring
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Environmental effects on the dynamic characteristics of a historic cathedral
No full textThe maintenance and preservation of the Milan Cathedral is traditionally performed through well-established and time-scheduled programs of visual inspection and architectural restoration of surfaces, decorations, and statues in Candoglia marble. On the other hand, the structural condition assessment and preservation turns out to be a challenging task due to the dimensions and complexity of the building, the usual uncertainties on the material properties and also the difficulty in inspecting several structural elements. Therefore, a structural monitoring system was recently designed and installed in the Milan Cathedral to assist the condition-based structural maintenance of the monument. The monitoring system includes different sensing technologies to allow appropriate tracking of different long-term structural behavior. The dynamic monitoring of the horizontal response of selected piers is complemented by the static monitoring of the tilt of the same piers and of the strain in selected tie-rods. In addition, the indoor and outdoor environmental parameters are extensively measured as well. After a concise historic background on the historic monument and the description of the dynamic monitoring system installed in the Milan Cathedral, the paper focuses on the dynamic characteristics of the monument, that were identified in the first hours of continuous monitoring, Subsequently, the results of the first year of dynamic monitoring are presented and discussed, with special attention being given to the influence of environmental parameters on the variations observed in the resonant frequencies and mode shapes. In more details, the presented results highlight that: (a) 8 global vibration modes are automatically detected in the frequency range 1.0-5.0 Hz; (b) the variations observed in the resonant frequencies are mainly driven by temperature, with the effect of thermal changes being very peculiar; (c) the mode shapes and the related mode complexity do not exhibit appreciable fluctuations associated to the environmental changes, so that an appropriate strategy of SHM should be based also on the time invariance of those parameters
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