1,721,272 research outputs found
Homogenization limit analysis
No full textFour approaches for the determination of the homogenized strength domain of running or header bond masonry walls, either in-plane or transversely loaded, are proposed and compared. The first one yields a lower bound, where the elementary cell is subdivided into a few rectangular subdomains and the microstress field is expanded using polynomial expressions. The second one is also based on the safe theorem of limit analysis, but joints are reduced to interfaces and bricks are subdivided into a few constant stress triangular elements. The third one is a “compatible identification” procedure, which belongs to the upper bound family, where joints are reduced to interfaces and bricks are assumed to be infinitely resistant. The last approach is also a kinematic (upper bound) procedure based on the so called Method of Cells, where the elementary cell is subdivided into six rectangular subcells with preassigned polynomial velocity fields fulfilling suitable periodic conditions. The first and last models have the advantage of taking the finite thickness of the joints into account. Although in the second approach joints are reduced to interfaces with frictional behavior, failure inside units (bricks or blocks) can be captured as well. In the framework of the upper bound theorem of limit analysis, simple linear programming optimization problems are derived to estimate the homogenized strength domains of masonry. The main advantages of the proposed approaches are the following: (1) the homogenized failure surface can be directly estimated, without the need for performing expensive step-by-step elasto-plastic finite element nonlinear analyses; (2) as the linear programming problem involves very few variables in all approaches, it is intrinsically very robust and allows, at the same time, the failure surface to be easily estimated. An insight into pros and cons of the utilization of the different approaches is provided, with reference to realistic examples
The Challenge of Gender Equality and Women's Rights in Francophone SubSaharan Africa. Brief notes from the Constitutional Courts of Madagascar and Senegal
No full text: The contribution addresses the issue of gender equality and protection of women's rights in
Francophone sub-Saharan Africa, analysing it in the prism of three decisions on the subject by the
constitutional courts of Madagascar and Senegal
Seismic assessment of historical masonry structures through advanced nonlinear dynamic simulations: applications to castles, churches, and palaces
No full textThe preservation of architectural heritage against earthquakes is currently a topic of increasing interest in Italy and requires an accurate seismic response assessment of the structures. Recent Italian seismic events have shown that severe damage or partial collapse can be caused to historical buildings even by low-to-moderate intensity earthquakes. Structural analysis is a fundamental tool to better evaluate the seismic response and vulnerability of historical buildings and define effective strengthening interventions: in particular, the use of advanced numerical tools to perform three-dimensional (3D) nonlinear dynamic analyses allows obtaining a thorough detailed knowledge of the seismic behavior of such a typology of structures. This chapter investigates the seismic response and damage distribution of three important historical masonry constructions of the outstanding cultural heritage in Mantua (Northern Italy) after the 2012 Emilia earthquake: the recent seismic sequence and the consequent significant crack patterns observed in the postearthquake survey phase pointed out their vulnerability to small seismic actions. Detailed and representative 3D finite element models of the historical masonry constructions are developed and nonlinear dynamic analyses are carried out to gain a deep numerical insight into the seismic response of the three structures, identifying the damage patterns and the most vulnerable parts for different seismic intensity levels
Modellazione numerica sperimentale a supporto della Artificial Neural Network: valutazione predittiva della resistenza all’accelerazione di collasso tramite curve di progetto degli edifici in muratura
Full text linkThe aim of this research is to develop an innovative and efficient methodology for the expedited
assessment of seismic vulnerability in masonry buildings, leveraging the capabilities of
artificial neural networks (ANN) integrated with an experimental numerical modeling
approach. Following catastrophic seismic events, masonry structures are often significantly
compromised, resulting in their classification as unsafe and uninhabitable. Traditionally, the
evaluation of such buildings relies on qualitative assessments performed by inspectors, who
provide preliminary estimates of structural reliability based on visual inspection and
experience. However, this process is inherently subjective and prone to inaccuracies, leading to
potential misclassifications that can either overestimate or underestimate the actual risk posed
by these structures.
To overcome these limitations, the proposed research adopts a machine learning framework,
specifically an ANN, to estimate the seismic response of masonry buildings with rectangular
geometries. This method allows for a comprehensive and data-driven evaluation of structural
vulnerability by incorporating a wide range of building geometries and material properties. The
study considers twelve distinct building geometries, twenty-four unique combinations of
mechanical parameters, and five different seismic loading directions, resulting in the simulation
of 34,560 configurations. These extensive simulations were then summarized through a
synthetic polynomial representation, which efficiently encapsulates the complexity of the
dataset while enabling streamlined analysis.
The ANN was trained, tested, and validated using results from an experimental numerical
approach grounded in the Distinct Element Method (DEM), a well-established analytical
method for the assessment of structural behavior under seismic loads. The performance of the
ANN, when compared to DEM-generated results, demonstrated a high level of accuracy, with
predictions differing by approximately 10%.
This confirms the viability of using machine learning techniques for the reliable prediction of
seismic performance in masonry structures. The primary outcome of this research is the
development of a comprehensive database of design curves, which can be employed for the
rapid assessment of the seismic vulnerability of masonry buildings. These design curves offer
a practical tool for engineers and decision-makers in the aftermath of earthquakes, providing a
quantitative and objective basis for classifying buildings as safe or unsafe.
The proposed methodology represents a significant advancement over traditional assessment
techniques, which are often limited by their reliance on subjective judgment. By combining
machine learning with established numerical methods, this research contributes to the
development of more reliable and scalable tools for the assessment of building safety in seismicprone areas
Experimental and numerical study of vibro-impact systems with two-sided constraints
No full textVibro-impact dynamics has been, and still is, the subject of growing interest for its practical and theoretical significance. Many practical engineering problems involve mechanical components or structures repeatedly colliding with one another or with obstacles during their motion. From a theoretical point of view, impact dynamics is highly interesting for the complex nonlinear behaviors and phenomena exhibited by vibro-impact systems, even the simplest. Despite the vibro-impact dynamics has been the subject of intense study, few works deal with the topic resorting to both experimental and numerical analyses. Furthermore, there are still some aspects that, to date, have been little deepened and deserve more attention.
The aim of this Ph.D. thesis is to characterize, in a systematic and transversal way, the nonlinear non-smooth response of vibro-impact systems with two-sided constraints. The study was inspired by the practical problem of large horizontal seismic-induced displacements in base-isolated structures. These displacements can damage the isolation system itself or can lead to pounding with surrounding moat walls or adjacent structures if the available seismic gap is not sufficient.
The problem was studied considering a single-degree-of-freedom (SDOF) system with two-sided deformable and dissipative constraints (bumpers) under harmonic base excitation and resorting to extensive parametric analyses, of both experimental and numerical nature, continuously interacting and feeding each other throughout the doctoral course. Shaking table tests were carried out on a small-scale physical model, using a rich sensor apparatus, and considering different values of gap amplitude, peak table acceleration and different bumpers. The numerical simulations were performed considering a relatively simple model, in which the impact phenomenon was modeled by a viscoelastic law, and using a Matlab code, specifically created for this purpose. This made it possible to carry out extensive parametric investigations. The adoption of a soft impact model allowed to describe the deformation and the recovery of the bumpers, otherwise not observable by resorting to the coefficient of restitution.
The influence of the fundamental parameters which characterize the problem on the system's response was first investigated. The numerical model, despite its relative simplicity, satisfactorily reproduced the experimental results and allowed to extend the range of investigation, compared to the experimental tests. A wide variety of behaviors and phenomena was observed. Different types of primary resonance (without hysteresis, with right or left hysteresis), secondary resonances (without hysteresis, with right or left hysteresis or of non-regular type), non-symmetric responses, multiple impacts, periodic, quasi-periodic and chaotic motion, were highlighted and investigated resorting to different types of representations. The occurrence of the (primary and secondary) grazing phenomenon, and its relationship with some of the observed scenarios, was also highlighted. The transition from a hardening-like to a softening-like behavior was experimentally observed passing from positive to small negative gaps, through the zero-gap configuration.
The study of the scenarios, besides being interesting from a theoretical point of view, highlighted possible issues associated with the occurrence of impact. This enabled to make interesting considerations on vibration control. By properly selecting the bumpers' parameters (gap and mechanical properties), it is possible to guide the system's response to reach specific objectives, avoiding some undesirable scenarios and encouraging others, and thus exploiting the occurrence of impact with beneficial effects. Some indications of optimal design of the bumpers are provided to reduce both the displacement and the acceleration of the mass, compared to the case without obstacles, without possibly reducing the vibration isolation frequency range
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
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