1,720,971 research outputs found
Recenti sviluppi nei metodi di analisi strutturale per la valutazione della vulnerabilità sismica degli edifici
No full textNon-linear Correlation Coefficients for pushover analysis
No full textAiming to put forward an improvement on Multimodal Pushover Analysis, a modified version of the
modal correlation rule that takes into account the non-linear behavior of structures is proposed. The modification
is primarily based on using the correlation coefficients consistent with the mechanical and dynamical properties
of the hysteretic oscillators utilized in the MPA method, i.e. determined taking into account the second order
statistics pertinent to the non-linear oscillators. Initially, the new correlation coefficients are evaluated by Monte
Carlo Simulations (MCS), assuming a spectrum-compatible representation of the seismic input. The results of a
large numerical parametric analysis are shown. Moreover, analytical expressions for the proposed correlation
coefficients are derived on the basis of the stochastic linearization technique. Lastly, the results provided by the
modified MPA for a simple 2DOF system are compared with Non-linear Response History Analysi
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
Combination of modal responses consistent with seismic input representation
No full textThe well-known modal superposition method for the evaluation of seismic response by the complete quadratic modal combination rule (CQC) is revisited. The most widely used version of the CQC rule utilizes correlation coefficients derived for white-noise excitation and neglects the influence of peak factor variation on the response. Here a simplified procedure for evaluation of correlation coefficients and peak factors consistent with the power spectral density of seismic excitation is proposed. The procedure is based on an approximate analytic expression for direct evaluation of the power spectral density of the excitation consistent with any prefixed response spectrum, and the evaluation of the consistent correlation coefficients and peak factors by using analytical expressions. The ranges of system dynamic parameters for which the correlation coefficients derived for white-noise excitation are not adequate are pointed out. Then the influence of the assumptions for CQC rule derivation on the evaluation of nodal response parameters is investigated, and the role played by the correlation coefficients and peak factors is pointed out
Stochastic sensitivity of steel frames with connection dampers by modal analysis
No full textA procedure for evaluation of dynamic response sensitivity of multistory steel frames with added viscoelastic beam to column connections by modal analysis is presented. The connection behavior is modeled by a Kelvin-Voigt element, consisting of a rotational spring and a dashpot connected in parallel. Consistent mass, stiffness and damping matrices of the multistory frame are utilized, leading to a structure modeling as a non-classically damped system. The procedure is based on the dynamic modification method, that allows to evaluate the response of non-classically damped structure by modal superposition, without transformation in the complex space. The differential equations governing the evolution of the derivatives of the responses (the so-called sensitivity equations) with respect to the stiffness and damping of the connections are derived in the modal subspace by a time domain approach. By means of an extensive employing of the Kronecker algebra the formulation is extended for evaluation of stochastic sensitivity of the dynamic response to a white noise excitation. The effectiveness of the proposed procedure in aiding the structural design is shown by evaluation of the response sensitivity of a eight-stow steel frame with added visco-elastic connections. The analysis allows to evaluate the parameter ranges for which the uncertainty in their evaluation results to a small risk level, due to a small sensitivity of the response
A modal approach for the evaluation of the response sensitivity of structural systems subjected to non-stationary random process
No full textA method for the evaluation of the response sensitivity of both classically and non-classically damped discrete linear structural systems under stochastic actions is presented. The proposed approach requires the following items: (a) a suitable modal expansion of the response; (b) the derivation in analytical form of the equations governing the evolution of the derivatives of the response (the so-called sensitivity equations) with respect to the parameters that define the structural model; (c) an extensive use of the Kronecker algebra for determining the analytical expressions of the sensitivity of the structural response statistics to non-stationary random input processes. Moreover, a step-by-step integration scheme able to solve the sensitivity equations is also studied. Handy expressions for the cross-correlations between the input process and the response sensitivities are also derived. A numerical application shows that the proposed approach is suitable to cope with practical problems of engineering interest
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
Combination coefficients for modal pushover analysis
No full textConventional non-linear static analysis estimates the response peak value by evaluating the pushover
curve adopting a distribution of invariant forces proportional to the fundamental vibration mode. In order
to include the effect of higher modes, multi-modal push-over analysis has been proposed in literature. Nodal response peak values are obtained by combination of “modal” responses usually by the traditional CQC method, requiring cross correlation coefficients defined for linear systems. In this paper, the accuracy of correlation coefficients for linear systems in predicting the statistical correlation of hysteretic oscillator responses is investigated by the Monte Carlo Simulation conducted on non-dimensional non-linear oscillators. Furthermore, new correlation coefficients determined through a pertinent statistical linearization are introduced, and the results provided by the classical and the proposed approach for two illustrative frames are compared with non-linear time history analysis, showing the effectiveness of the new procedure
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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