1,721,019 research outputs found
Shaking-table tests on reinforced concrete frames with different isolation systems
No full textThe effectiveness of seismic isolation in protecting structural and non-structural elements from damage has been assessed in an extensive programme of shaking-table tests, carried out on four identical 1/3.3-scale, two-dimensional, reinforced concrete (R/C) frames. Four different isolation systems were considered, namely: (i) rubber-based, (ii) steel-based, (iii) shape memory alloy (SMA)-based and (iv) hybrid, i.e. based on both SMA and steel components, isolation systems. This paper presents a comprehensive overview of the main results of the experimental tests on baseisolated models, whose structural response is described through: (i) maximum base displacements; (ii) maximum interstorey drifts; (iii) maximum storey accelerations and (iv) maximum storey shear forces. The evolution of the fundamental frequency of vibration of the R/C frame during the tests is also described. The beneficial effects of using base isolation resulted in no or slight damage, under strong earthquakes, to both structural and non-structural members, as well as to the internal content of the building. The comparison with the experimental results obtained in shaking-table tests on similar fixed-base models emphasizes these positive aspects. Finally, advantages and drawbacks related to the use of each isolation system are discussed in the paper
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
Lateral Force Distributions for the Linear Static Analysis of Base-Isolated Buildings
No full textThis paper presents a new approach for the evaluation of accurate lateral force distributions for the Linear Static Analysis (LSA) of Base Isolated (BI-) buildings. In essence, the proposed lateral force distributions depend on a factor measuring the degree of nonlinearity of the Isolation System (IS) and on the ratio between the effective period of the BI-structure (Tis) and the fundamental period of the Fixed Based (FB-) structure (Tfb). The proposed approach is fully compatible with the Direct Displacement-Based Design (DDBD) method, recently developed by Priestley and co-workers. The proposed lateral force distributions have been derived from the results of a large number of Nonlinear Time-History Analyses (NTHA), carried out on six numerical models of multi-storey buildings, differing in storey number (3, 5 and 8, respectively) and fundamental period of vibration (from 0.25 to
0.8 s) in the fixed-base configuration. A great variety of Isolation Systems (ISs), characterised by either Elasto-Plastic with Hardening (EPH) or Flag-Shaped (FS) force-displacement behaviour, have been considered in the NTHA. The numerical parameters of the IS models have been varied in such a way as to reproduce the actual mechanical behaviour of the main currently used ISs, including: (i) Lead Rubber Bearings (LRB), (ii) High-Damping Rubber Bearings (HDRB), (iii) Friction Pendulum Bearings (FPB), (iv) combinations of flat Sliding Bearings (SB) and Low-Damping Rubber Bearings (LDRB) and (v) Combinations of flat SB
and re-centring devices based on Shape Memory Alloys (SMA). Comparisons between the storey shear forces derived with the proposed method and those obtained from NTHA clearly show the great improvements in the accuracy of LSA predictions, when using the proposed lateral force distributions
Frictional behavior of steel-PTFE interfaces for seismic isolation
No full textThe widespread use of sliding bearings for the seismic isolation of structures requires detailed knowledge of their behavior and improved modeling capability under seismic conditions. The paper summarizes the results of a large experimental investigation on
steel–PTFE interfaces, aimed at evaluating the effects of sliding velocity, contact pressure, air temperature and state of lubrication on the mechanical behavior of steel-PTFE sliding bearings. Based on the experimental outcomes, two different mathematical models have been calibrated, which are capable of accounting for the investigated parameters in the evaluation of the sliding friction coefficient. The first model is basically an extension of the model
proposed by Constantinou et al. (1990) Journal of Earthquake Engineering, 116(2), 455–472, while the second model is derived from the one proposed by Chang et al. (1990) Journal of
Engineering Mechanics, 116, 2749–2763. Expressions of the model parameters as a function of bearing pressure and air temperature are presented for lubricated and non-lubricated sliding surfaces. Predicted and experimental results are finally compared
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