1,720,976 research outputs found
On the application of the yield-line method to masonry infills subjected to combined in-plane and out-of-plane loads
Full text linkThe influence of infills on the seismic response of frame structures has been long recognised. On the one hand, the presence of infills may be beneficial, due to their contribution to dissipate energy. On the other hand, irregular infill distributions in plan or elevation can lead to concentration of the displacement demand in localised parts of the building. It is noted that the lack of one or more panels may depend on the original building layout or may be generated by the infill collapse during a seismic event. It is therefore of interest the assessment of their capacity to resist out-of-plane loads. In this paper, the use of the yield-line theory for the estimation of the out-of-plane infill strength is investigated. The method is described in detail and an example of derivation of the related equations is presented. Afterward, a modification of such equations is suggested to account for different contact conditions at the infill-frame interface. Moreover, specific attention is paid to the assessment of the masonry flexural strength, which is a basic parameter for the application of the method. Finally, a reduction factor is calibrated to extend the method to those cases in which previous in-plane damage is present. Experimental tests available in the literature are used to verify and calibrate the proposed equations and coefficients
Evaluation of optimal lateral resisting systems for tall buildings subject to horizontal loads
Full text linkThe tendency of modern designs towards optimal structures often leads to the lightest and best performing choice among a large set of design alternatives. In a similar scenario, the introduction of automated tools to further guide designers in achieving efficient solutions has been a recurrent topic for mechanical and structural engineers, over the past decades. Nowadays, topology optimization is considered a powerful preliminary design tool to determine the optimal material distribution in a design domain, i.e. the most effective configuration that satisfies a given set of prescribed constraints while reducing the consumption of structural material. Among different applications in the field of Civil Engineering, this work focuses on the definition of optimal layouts of lateral resisting systems for multi-storey steel building frameworks subject to lateral loads using topology optimization techniques. The objective of the research is to illustrate the benefits deriving from the introduction of automated routines within the preliminary design stage and establish reliable guidelines for performing accurate and objective optimization procedures. Since the optimal material distribution follows the load flow within the structure, optimal topologies are especially sensitive to the alteration of support and loading conditions: different loading scenarios naturally lead to distinct optimal layouts. In order to avoid the loss of objectivity and preserve the optimality of the results, the effects that preliminary modelling and loading assumptions produce on final layouts are investigated. Numerical applications to high-rise building models are presented and discussed
Comparison of the effects of traditional and innovative tie-rods in reducing the seismic vulnerability of church façades: the case of San Francesco in Mirandola (Italy)
No full textThis contribution discusses the effect of steel tie-rods installed in a church façade subjected to 60 recorded earthquakes. The church façade is firstly analysed as a two-sided and a one-sided rocking SDOF system. For the one-sided rocking, sidewalls are modelled through either elastic or rigid contact to compare the two modelling techniques. Secondly, two configurations of tie-rods are investigated: (i) traditional tie-rods with a specific elasto-plastic constitutive law and (ii) innovative tie-rods with a dissipative component. The chosen case study is the San Francesco Church located in Mirandola, hit by the 2012 Emilia Romagna earthquake. The results of nonlinear dynamic analyses are presented in terms of median and standard deviation of maximum normalised displacements for each of the 60 seismic inputs. The results show the great benefit introduced by both traditional and dissipative tie-rods, with remarkable reductions of maximum rotations up to an order of magnitude with respect to the unrestrained façade. Moreover, the increment of damping coefficient is associated to a reduction of the standard deviation of the amplitude peaks, which is a positive aspect for the reliability of the response of the damped wall. Finally, the two models, rigid and elastic contact, of sidewalls provide results in excellent agreement in terms of median and standard deviation of the maximum normalised rotations
Quantification of energy-related parameters for near-fault pulse-like seismic ground motions
Full text linkAn energy-based approach facilitates the explicit consideration of the damage associated with both maximum displacements and cumulative plastic deformations under earthquakes. For structural systems that can undergo pulse-like seismic ground motions close to causative faults, an energy-based approach is deemed especially appropriate with respect to well-established force-or displacement-based strategies. In such a case, in fact, most of the damage is attributable to the dominant pulse-like component, which usually occurs into the velocity time history of the seismic ground motion, thus implying high energy levels imparted to a structural system. In order to enable the implementation of an energy-based approach in the analysis and design of structures under near-fault pulse-like seismic ground motions, this study presents a comprehensive numerical investigation about the influence of seismological parameters and hysteretic behavior on the spectra of the following energy-related parameters: inelastic absolute and relative input energy; input energy reduction factor; hysteretic energy dissipation demand; hysteretic energy reduction factor; dimensionless cumulative plastic deformation ratio. Closed-form approximations are proposed for these spectra, and the numerical values of the corresponding parameters have been also calibrated (with reference to both mean and standard deviation values) as functions of earthquake magnitude, type of hysteretic behavior (i.e., non-degrading or degrading) and ductility level. The outcomes of this study are meant to support the derivation of design spectra for the energy-based seismic design of structures under near-fault pulse-like seismic ground motions
EQUIVALENCE OF DAMPING PROPERTIES OF DISSIPATIVE DEVICES FOR MITIGATING THE SEISMIC RISK OF RIGID BLOCKS
No full textNon-structural elements, such as infill walls, precast r.c., timber panels, machines, cabinets, art objects, etc. can be considered as rigid rocking blocks whose seismic vulnerability may be reduced by means of dissipative and recentering devices. These devices can be installed in dif-ferent positions of the rigid block. This paper proposes an equivalence criterion to compare dashpots installed either at the base or at the top of rocking blocks in terms of damping coef-ficients. An analytical expression is obtained and validated through deterministic and stochas-tic approaches. The first aims to compare the two scenarios' performances, while the second introduces a probabilistic assessment in terms of fragility curves and seismic demand hazard. The comparisons exhibit an optimal agreement, making the analytical formulation reliable for design purposes
Shake table testing of a low-impact technology for the seismic protection of stone masonry
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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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