1,720,957 research outputs found
Response spectrum analysis of frame structures: reliability-based comparison between complete quadratic combination and damping-adjusted combination
No full textIn the framework of seismic design of structures, response spectrum analysis (RSA) is the
most commonly used approach in practice. The most popular combination rule is the complete
quadratic combination (CQC) which is also prescribed by the most of seismic design
codes and is based on the assumptions that the seismic acceleration is a white noise process
and the peak factor ratios associated to the total and modal responses are unitary. Recently,
the damping adjusted combination (DAC) rule has been developed for base-isolated structures
to overcome the aforementioned simplified assumptions. Although it has been proved
that the simplifications about peak factors lead to noticeable errors in the case of baseisolated
structures, the accuracy gain of DAC with respect to CQC in the case of fixed-base
structures is still unknown. Therefore, the paper presents an in-depth study on the RSA of
three-dimensional frame structures, aimed to evaluate the accuracy of the above methods.
Two reference classes of frame structures having different degree of complexity are considered.
Average interstorey drift and floor torsion responses, obtained from a set of Time
History Analyses are compared with those of the modal combination rules. Lognormal
joint probability density functions of the predictive errors from CQC and DAC are finally
evaluated for a reliability assessment of the two combination rules under bidirectional seismic
excitations
Simplified analytical models for compressed concrete columns confined by FRP and FRCM system
Full text linkIn order to consider the response of concrete columns confined by FRP and FRCM system, proper models have to be formulated. In this context the present paper shows a generalized criterion for the determination of the increase in strength, in ductility and in dissipated energy for varying corner radius ratio of the cross section and fiber volumetric ratio. The procedure is based on the best fitting of several experimental data and unlike the usual empirical approaches available in the literature, the proposed technique relates the confinement effectiveness to a single parameter representative of the relative stiffness between the original concrete core and the reinforcement system. Furthermore, the proposed analytical models overcomes the limit of many empirical or semi-empirical models given in the literature that are applicable only to specific cases. A comparison with same available models confirm the reliability of the proposed procedure
Numerical calibration of a simplified model for FRP confinement of columns
No full textThis paper presents the calibration of a simplified analytical model for concrete columns confined by fiber reinforced polymer (FRP) jackets. The model allows evaluating the increase of strength, ductility and dissipated energy without defining the lateral confinement pressure and it can be easily extended for the assessment of FRP confinement in design applications. This model was obtained by a simplified procedure based on the best fit of experimental data available in the literature and the coefficient of determination (R2) was evaluated in order to estimate the accuracy of the regression analysis. A numerical database resulting from finite element (FE) analyses was compiled and reported for integrating the model’s calibration obtained by the few experimental data. The FE models are built based on results of experimental tests available in the literature and several FE simulations are carried out. The experimental results are then integrated with numerical results and new forms of the simplified expressions are obtained by new best fit. The new values of R2 confirm an improvement of the accuracy of the regression analysis. Finally, the performance of the simplified model is compared with existing formulas available in the literature
Incremental dynamic based fragility assessment of reinforced concrete structures: Stationary vs. non-stationary artificial ground motions
No full textArtificial and natural records are commonly employed by researches and practitioners to perform refined seismic assessments of structures. The techniques for the generation of artificial records and their effectiveness in producing signals which are significantly representative of real earthquakes are still debated as well as results of the consequent seismic assessment to expect from their application. The paper presents an in-depth comparative study highlighting the effect of employing different typologies of artificial ground motion records on seismic assessment results, especially addressing seismic fragility curves. Three sets of 50 stationary, nonstationary evenly modulated and fully nonstationary accelerograms are generated based on design spectrum compatibility criteria. Standard nonlinear time history analyses of 4 reference structural models of reinforced concrete (RC) structures having different degree of complexity are firstly carried out monitoring results in terms significant engineering seismic demand parameters. So far, incremental dynamic analysis (IDA) is used to derive fragility curves. Peak ground acceleration and spectral acceleration are used as possible intensity measures in order to compare results of seismic fragility assessment. The combination of structural irregularity, severe damage and input typology is finally analyzed and discussed in order to assess the degree of dependence of fragility assessments on the typology of signal adopted
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
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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