1,720,987 research outputs found
Effects of soil-structure interaction on inelastic seismic response of bridge piers
No full textThe investigation reported in the paper is an attempt to assess the relevance of soil-structure interaction (SSI) effects on the dynamic response of bridge piers responding in the inelastic range and, in particular, on the maximum required ductilities in the critical regions of the superstructure. The problem is dealt with reference to a simple structural configuration: a vertical cantilever carrying a mass at the top, representing realistic cases of bridge piers of common geometry with spread footing foundations. A relatively large number of parameters has been considered in the analysis, with a total of 240 cases examined, and with ductility demands on the piers ranging between 1.5 and 7. The results indicate that although in most cases SSI produces an increase of the maximum displacements, this effect is not very significant, and the inelastic demand in terms of curvature essentially remains unaffected by soil-structure interaction, showing a tendency to decrease. Finally, the stability of these conclusions against rather extreme variations of the parameters is confirmed by the results of additional bounding analyses, characterized by unusually soft soil conditions and by a seismic excitation multiplied by a factor of two
Validating IM-based methods for probabilistic seismic performance assessment with higher-level non-conditional simulation
No full textProbabilistic seismic performance assessment of structures can be carried out with different methods. One possible classification of the latter is into two main classes: IM-based methods (with IM being the well-known acronym for Intensity Measure, a scalar or vector quantity expressing the local intensity of ground motion at a site) and full-blown simulation methods. Two different probabilistic representations of the ground motion are employed in the two classes. In the former case, real recorded motions are used to determined the fragility curve, or more generally the structural response given the IM. Then an hazard curve for the chosen IM is used with the fragility curve to determine the mean annual frequency (MAF) of exceedance of any performance level of interest. In the latter case, a synthetic ground motion model is employed to produce time-series starting from basic (random) macro-seismic parameters that are part of the simulation, such as event magnitude and location.
Whether the two classes of approaches lead to the same results is a question first asked in Jalayer and Beck (2008), where the Atkinson and Silva synthetic ground motion model and the subset simulation methods where employed.
This paper presents a comparison along the same lines but using the importance sampling with K-means clustering method (Jayaram and Baker 2010) for the analysis and, most importantly, the parametrized random process model by Rezaeian and Der Kiureghian (2010) to generate ground motion time series. This latter model claims to reproduce not only the mean of real ground motions but also their natural variability. This is instrumental in evaluating the correct MAF of structural response, which depends on the total variability (including that of ground motion). Indeed, the lower than natural variability exhibited by the Atkinson and Silva model was to reason for Jalayer and Beck (2008) to introduce a "correction term" that inflated ground motion variability.
F. Jalayer and J. L. Beck ‘Effects of two alternative representations of ground-motion uncertainty on probabilistic seismic demand assessment of structures’, Earthquake Engng Struct. Dyn. 2008; 37:61–79
Jayaram N and Baker J W (2010), ‘Efficient sampling and data reduction techniques for probabilistic seismic lifelines assessment’, Earthquake Engineering and Structural Dynamics, 39, 1109-1131.
S. Rezaeian and A. Der Kiureghian ‘Simulation of synthetic ground motions for specified earthquake and site characteristics’ Earthquake Engng Struct. Dyn. 2010; 39:1155–118
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
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