1,720,967 research outputs found
Fragility functions for local failure mechanisms in unreinforced masonry buildings: a typological study in Ferrara, Italy
No full textUnreinforced masonry buildings undergoing seismic actions often exhibit local failure mechanisms which represent a serious life-safety hazard, as recent strong earthquakes have shown. Compared to new buildings, older unreinforced masonry buildings are more vulnerable, not only because they have been designed without or with limited seismic loading requirements, but also because horizontal structures and connections amid the walls are not always effective. Also, Out-Of-Plane (OOP) mechanisms can be caused by significant slenderness of the walls even if connections are effective. The purpose of this paper is to derive typological fragility functions for unreinforced masonry walls considering OOP local failure mechanisms. In the case of slender walls with good material properties, the OOP response can be modeled with reference to an assembly of rigid bodies undergoing rocking motion. In particular, depending on its configuration, a wall is assumed either as a single rigid body undergoing simple one-sided rocking or a system of two coupled rigid bodies rocking along their common edge. A set of 44 ground motions from earthquake events occurred from 1972 to 2017 in Italy is used in this study. The likelihood of collapse is calculated via Multiple Stripe Analysis (MSA) from a given wall undergoing a specific ground motion. Then, the single fragility functions are suitably combined to define a typological fragility function for a class of buildings. The procedure is applied to a historical aggregate in the city center of Ferrara (Italy) as a case study. The fragility functions developed in this research can be a helpful tool for assessing seismic damage and economic losses in unreinforced masonry buildings on a regional scale
An enhanced corotational Virtual Element Method for large displacements in plane elasticity
No full textAn enhanced virtual element formulation for large displacement analyses is presented. Relying on the corotational approach, the nonlinear geometric effects are introduced by assuming nodal large displacements but small strains in the element. The element deformable behavior is analyzed with reference to the local system, corotating with the element during its motion. Then, the large displacement-induced nonlinearity is accounted for through the transformation matrices relating the local and global quantities. At the local level, the Virtual Element Method is adopted, proposing an enhanced procedure for strain interpolation within the element. The reliability of the proposed approach is explored through several benchmark tests by comparing the results with those evaluated by standard virtual elements, finite element formulations, and analytical solutions. The results prove that: (i) the corotational formulation can be efficiently used within the virtual element framework to account for geometric nonlinearity in the presence of large displacements and small strains; (ii) the adoption of enhanced polynomial approximation for the strain field in the virtual element avoids, in many cases, the need for ad-hoc stabilization procedures also in the nonlinear geometric framework
Effect of uncertainties on seismic fragility for out-of-plane collapse of unreinforced masonry walls
No full textA new approach for the evaluation of fragility curves of UnReinforced Masonry (URM) walls is proposed. Uncertainties on geometrical and mechanical properties, as well as on magnitude and position of the applied loads, are considered using fuzzy set theory. Fuzzy set theory has been broadly applied to civil engineering problems, particularly to reinforced concrete structures, though its application to masonry, to the authors’ knowledge, is investigated here for the first time to evaluate the seismic response of masonry walls in the presence on vague and imprecise information. The proposed procedure allows computing fragility curves based on available typological databases, integrated with experimental tests and survey data. One of the main advantages of this procedure is that it can account for the variability of structural typologies on a territorial scale. The effectiveness of the method is shown through numerical examples concerning walls made of fired clay bricks and lime mortar, which are typical construction materials in the Po River Plain, in Northern Italy. Linear kinematic and nonlinear time-history analyses are used to calculate the seismic response. The computed fuzzy-like fragility curves include both aleatory and epistemic uncertainties. An extensive sensitivity analysis based on suitable sets of representative input parameters is carried out to validate the proposed procedure
Stochastic seismic assessment of bridge networks by matrix based system reliability method
No full textInfrastructure systems cover an important role for economic activities and emergency response after a disaster, such as an earthquake. Within these systems, bridges represent a crucial component. However, they are often considered a weak link because of their vulnerability to hazards. Indeed, the structural damage of a bridge can create a disconnection in a transportation network or reduce its functionality. A probabilistic approach is the natural environment in which to analyze a complex network system and carry out risk/loss assessment estimations and decision-making processes. This problem presents various computational challenges and usually, sampling-based approaches are used to account for the uncertainty. In this contribution, a pri-oritization methodology is developed using the matrix-based system reliability (MSR) approach. This method is capable of delivering component failure probabilities and estimating the probabilities of complex system events with parameters sensitivities through efficient matrix calculations
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
A machine learning approach to the seismic fragility assessment of buildings
No full textEvaluating the likelihood of damage in buildings undergoing earthquake actions is a difficult and timeconsuming
task. In the context of Performance-Based Earthquake Engineering (PBEE), an intensity measure
(IM) provides a link between the probabilistic seismic hazard analysis and the probabilistic structural response
analysis [1-2]. The purpose of this study is to develop a structural damage classifier and improve current
prediction on the basis of a given intensity measure and different supervised machine learning algorithms [3]:
Support-Vector Machine (SVM), Logistic Regression (LR) and Random Forest (RF)
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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