1,721,058 research outputs found
Closed-form expressions for the macroscopic elastic constants of Flemish bond masonry walls
No full textThe problem of obtaining reliable closed-form expressions for the macroscopic elastic coefficients of Flemish bond brickwork according to the mechanical properties and the geometry of joints and units is dealt with. Unlike most similar existing works, which are limited to single-wythe walls, here the coexistence of headers and stretchers is taken into account, together with the presence of collar joints. Similarly to the so-called Method of Cells for fiber-reinforced composites, any Representative Volume Element (RVE) of the wall is divided into sub-cells. A piecewise-differentiable 3D strain-periodic displacement field, depending on a limited number of degrees of freedom (d.o.f.s), is formulated over the RVE. Suitable boundary conditions are prescribed at the interfaces between the sub-cells, thus reducing the number of independent d.o.f.s. The remaining d.o.f.s can be related to the macroscopic strains of the RVE. Upon integration of the microscopic stress and strain fields, the homogenized elasticity matrix can be obtained. The accuracy of the theoretical predictions is assessed by comparison with the results of Finite Element analyses of the RVE subjected to elementary macroscopic stresses, and with other benchmarks available in the literature
Optimal fiber-reinforcement of no-tension masonry walls through a stress-based formulation
No full textA topology optimization problem is dealt with, which aims at distributing a prescribed amount of fiber-reinforcement over any masonry wall, so as to maximize the overall stiffness of the strengthened element. A no-tension (NT) model is adopted to account for the negligible tensile strength of brickwork. The equilibrium of the NT body is enforced through an energy-based method, which replaces brickwork by an equivalent orthotropic medium with constraints on the stress state. The inability if the reinforcement to carry compressive stresses is also taken into account in a similar way. The stress analysis of the reinforced NT body can be straightforwardly embedded within the topology optimization formulation, with no need for demanding incremental approaches. Both the regions to be strengthened and the local orien-tation of the optimal FRP strips are identified. To improve accuracy in the enforcement of the stress constraints, an efficient formulation that uses stresses as main variables of the elastic problem is implemented. Also, the structural compliance is computed through the evaluation of the complementary strain energy. A preliminary numerical example is shown, to assess the capabilities of the proposed procedure
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
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
Fragility analysis of masonry structural units by Response Surface method
No full textStructural masonry aggregates include a set of inhomogeneous structural units that
can interact under seismic action; therefore the seismic analysis cannot ignore the inevitable
interactions resulting from structural contiguity between adjacent buildings [1,2]. The study
of a masonry aggregate cannot neglect the unavoidable uncertainties related to geometries
and material characteristics of their components. In this work the first results of a research
focused on the fragility analysis of masonry structural units by statistical procedures are presented.
In order to take the structural and geometrical variabilities and uncertainties involved
in the problem into account, the Response Surface (RS) statistical method is used, where the
expected value of a response parameter (for instance the acceleration corresponding to the
attainment of a prescribed limit state of the building) is approximated through a polynomial
function of a set of selected variables [3]. The RS model is calibrated through numerical data
obtained by non-linear static analysis, with reference to a masonry building (structural unit)
whose geometrical and mechanical properties are varied in prescribed ranges. The number of
simulations and the values of the variables to be used to obtain the data for the RS calibration
are defined by applying the Design of Experiments Theory [3]. Finally, fragility curves are
evaluated through the RS obtained from the numerical simulation data.
The results have highlighted the importance of the probabilistic procedures as methods able
to consider the variabilities and the uncertainties involved in the problem of the fragility of
masonry structures
An innovative approach for the finite element modelling of masonry cracking
No full textThe performance of masonry structures under seismic conditions is strongly influenced
by cracking phenomena that have to be taken into account to obtain a reliable evaluation
of mechanical resources. An innovative finite element procedure is presented to simulate
initiation and propagation of in-plane tensile crack in masonry material. The material is studied
at the macro-level and modelled as a homogenous continuum by means of triangular shell
elements. The cracks are considered as localized inelastic deformations in the frame of the
classical theory of plasticity. Control of tensile stress is formulated and implemented along
possible cracking lines, corresponding to the mesh edges, in terms of generalized forces at the
nodes. When the limit tension is reached at one node and the crack starts to open, the activated
inelastic constitutive law is taken as a single-branch softening curve. A Parametric Linear
Complementarity Problem is solved to evaluate the cracking evolution of the structure until
collapse. Some numerical examples are presented to validate the formulation
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
Damage control, preservation procedures and durability studies: an investigation approach through the Milan Duomo Cathedral archives
No full textSince the long collaboration between Veneranda Fabbrica del Duomo and Politecnico di Mi-lano (VFD) was renewed, the Duomo Cathedral has been investigated from different points of view in order to enhance the continuous care procedures, which can be understood in the theo-retical frame of preventive and planned conservation [1].
Among the different study approaches, the collaboration with the historical archive of the VFD showed the potentialities for recording the main pathologies afflicting the building during dif-ferent periods and for classifying the intervention criteria set for facing specific problems affect-ing the main loadbearing structures and their materials.
The archive documents provided precious indications concerning the restoration works and strategical measures adopted for the common decay problems presented by the building mate-rials [2], [3]. A turning point in the intervention philosophy, observed in the archives docu-ments, occurred in the beginning of the 1960s, when the Cathedral was concluded, and the VFD had to move from construction and maintenance activities to the conservation issues [4]. On behalf of the large amount of interventions that became a constant care for the building, from the second half of the last century, the VFD promoted interesting efforts in the mainte-nance policy by experimenting new technological solutions [5]. With the aim to protect the dif-ferent features of the Cathedral, new special mixtures were introduced in the common interven-tion criteria, experimenting on site new resins for repairing. At an impressive extension, these practices produced new systems made up of different materials, namely marble and stones, iron, mortars and resins, whose compatibility on the long run is still to be evaluated. This work fo-cuses on the consequences observed after the development of a clear common practice for the care requested by such a complex building
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