1,720,972 research outputs found
Experimental Behavior of Concrete Joint Interfaces under Reversed Cyclic Loading
No full textA large scale test on concrete joints subjected to constant compressive confinement and reverse cyclic shear load is performed. Shear strength, dilatancy degradation, and overall response are reported. A description of roughness as composed by two orders of asperities with different sizes is used to analyze the results and prompts the extension of an existing generalized joint model. The validity of the interpretation and the role of the proposed extension are pointed out by means of comparisons between numerical simulations and experimental results
Experimental Behaviour of Concrete Joints Under Reversed Cyclic Loading
No full textInterface joints play an important role in the seismic response of masonry and concrete
structures especially for large and unreinforced ones.. Despite their different origin, all these
discontinuities can be generically characterized as “joint” to be modelled through a single
generalized formulation, Puntel et al. (2006). Joint models abound in the literature and have
reached levels of significant sophistication and maturity specially when examined through the
prisms of fracture, plasticity or damage mechanics. However, most of them are inherently
developed under the assumption of monotonic loading conditions thus disregarding specific
features of reversed cyclic loading; in some cases this can lead to gross mistakes such as
unsafe overestimation of joint opening. This deficiency is partly explained by the
comparatively small number of test data and by the concurrent lack of experimentally derived
relationships.
As such, this paper addresses the scarcity in relevant tests. First, a complex experimental set-
up is described and results reported of large scale tests on concrete joints subjected to constant
compressive confinement and reverse cyclic shear load. After the analysis and discussion of
the results, many evidences have prompted an interpretation based on a description of joint
roughness as composed by two orders of asperities each with its own size and degradation
properties. In view of these findings, an enhancement of the aforementioned generalized
model previously developed by the authors has been motivated. Finally the numerical
response of both the existing and the updated joint models has been compared with the
experimental one. Thus the role of the proposed extension is clarified showing in particular
the effectiveness of the asperity description in explaining at the same time both the shear
strength and the dilatancy behaviour
A Fracture Mechanics Based Model for Joints Under Cyclic Loading
No full textA generalized interface model for joints and cracks in quasi-brittle materials is formulated. The proposed model marries an existing fracture mechanics based one developed for monotonic loading of concrete with another frictional based model developed for the cyclic response of rock joints to address the (reverse) cyclic response of rough surfaces in the presence of cohesive stresses. The properties of the model and its capability to capture several experimentally observed behaviors are shown by the numerical simulations performed. This joint constitutive model is particularly suitable to simulate the seismic response of dam/rock joints subjected to seismic excitation, or of concrete joints under reverse cyclic loading
Implementation of Lumped Plasticity Models and Developments in an Object Oriented Nonlinear Finite Element Code
Full text linkNumerical simulation tools capable of modeling nonlinear material and geometric behavior are important to structural engineers concerned with approximating the strength and deformation capacity of a structure. While structures are typically designed to behave linear elastic when subjected to building code design loads, exceedance of the linear elastic range is often an important consideration, especially with regards to structural response during hazard level events (i.e. earthquakes, hurricanes, floods), where collapse prevention is the primary goal. This thesis addresses developments made to Mercury, a nonlinear finite element program developed in MATLAB for numerical simulation and in C++ for real time hybrid simulation. Developments include the addition of three new constitutive models to extend Mercury's lumped plasticity modeling capabilities, a constitutive driver tool for testing and implementing Mercury constitutive models, and Mercury pre and post-processing tools.Mercury has been developed as a tool for transient analysis of distributed plasticity models, offering accurate nonlinear results on the material level, element level, and structural level. When only structural level response is desired (collapse prevention), obtaining material level results leads to unnecessarily lengthy computational time. To address this issue in Mercury, lumped plasticity capabilities are developed by implementing two lumped plasticity flexural response constitutive models and a column shear failure constitutive model. The models are chosen for implementation to address two critical issues evident in structural testing: column shear failure and strength and stiffness degradation under reverse cyclic loading. These tools make it possible to model post-peak behavior, capture strength and stiffness degradation, and predict global collapse.During the implementation process, a need was identified to create a simple program, separate from Mercury, to simplify the process of implementing a new constitutive model. A constitutive driver tool with a graphical user interface is developed to address this issue, providing benefits for Mercury development and classroom learning.A Mercury pre and post-processor graphical user interface is also implemented. The developed tool is a standalone application which allows Mercury users to visualize numerical models for verification and view analysis results without the need to transfer information. Mercury analysis may also be run from within the application. All necessary pre-process, analysis, and post-process procedures are, therefore, combined into the program, collectively referred to as Mercury++
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
Implementation of Lumped Plasticity Models and Developments in an Object Oriented Nonlinear Finite Element Code
Full text linkNumerical simulation tools capable of modeling nonlinear material and geometric behavior are important to structural engineers concerned with approximating the strength and deformation capacity of a structure. While structures are typically designed to behave linear elastic when subjected to building code design loads, exceedance of the linear elastic range is often an important consideration, especially with regards to structural response during hazard level events (i.e. earthquakes, hurricanes, floods), where collapse prevention is the primary goal. This thesis addresses developments made to Mercury, a nonlinear finite element program developed in MATLAB for numerical simulation and in C++ for real time hybrid simulation. Developments include the addition of three new constitutive models to extend Mercury's lumped plasticity modeling capabilities, a constitutive driver tool for testing and implementing Mercury constitutive models, and Mercury pre and post-processing tools.Mercury has been developed as a tool for transient analysis of distributed plasticity models, offering accurate nonlinear results on the material level, element level, and structural level. When only structural level response is desired (collapse prevention), obtaining material level results leads to unnecessarily lengthy computational time. To address this issue in Mercury, lumped plasticity capabilities are developed by implementing two lumped plasticity flexural response constitutive models and a column shear failure constitutive model. The models are chosen for implementation to address two critical issues evident in structural testing: column shear failure and strength and stiffness degradation under reverse cyclic loading. These tools make it possible to model post-peak behavior, capture strength and stiffness degradation, and predict global collapse.During the implementation process, a need was identified to create a simple program, separate from Mercury, to simplify the process of implementing a new constitutive model. A constitutive driver tool with a graphical user interface is developed to address this issue, providing benefits for Mercury development and classroom learning.A Mercury pre and post-processor graphical user interface is also implemented. The developed tool is a standalone application which allows Mercury users to visualize numerical models for verification and view analysis results without the need to transfer information. Mercury analysis may also be run from within the application. All necessary pre-process, analysis, and post-process procedures are, therefore, combined into the program, collectively referred to as Mercury++
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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