1,721,132 research outputs found
Experimental study on hybrid control of multimodal cable vibrations
No full textThe effectiveness of a hybrid control policy in mitigating the linear and non-linear multimodal cable vibrations is investigated by means of a numerical analysis and a campaign of laboratory tests. The proposed control method is a hybrid solution combining wrapped shape memory alloy wires and an open-loop actuation. By operating in this way, a robust and economical control strategy is obtained which overcomes the damper/actuator localization and the state-tracking difficulties that significantly impair the overall control effectiveness of most of the control solutions already investigated in the literature. The proposed approach has shown, in a separate study, promising vibration mitigation capabilities when the motion was essentially dominated by the first in-plane mode. Here, the capability of the hybrid control policy in mitigating also the nonlinear vibrations of the second in-plane mode is under specific investigation
Dispersive phenomena in bridges by time-frequency analysis
No full textThis paper reports on frequency splitting phenomena, also called “dispersive phenomena”, observed in the response of two bridges. The former is a reinforced concrete arch bridge that was tested in February 2012, while the latter is an historical iron arch bridge that has been permanently monitored since November 2011. The analysis of ambient vibration response data was performed through classical techniques and a more advanced time-frequency distribution. Because dispersive phenomena are typically originated by some structural damage, the presented results might contribute to the discussion towards the definition of reliable vibration-based health assessment techniques
Nanotechnology in Cement-Based Construction
No full textNew smart materials are developing thanks to nanotechnology. Many books are on the market, but the demand for specialized analyses of particular topics still remains. This multiauthor book focuses on the application of nanotechnology to cement-based materials for engineering applications. The addition of novel smart nanofillers allows the development of multifunctional composite materials and not just with respect to higher mechanical strength, as investigated in the past. Special attention is given to types of nanoinclusions, novel techniques to mix components, and analysis of properties that can be achieved by paste, mortar, or concrete if they are added with nanofillers. Among these properties, the capability of self-sensing is very promising. Moreover, the use of phase-changing materials improves energy efficiency of nanocomposites, with important applications in the field of engineering, and new nanomodified composites have applications in energy harvesting and electromagnetic shielding
Strengthening of Masonry Walls Using Jute Fiber: Merging Structural and Thermal Upgrading/Retrofitting
No full textIn the past five decades, man-made and synthetic fibers have dominated the market and have been used to strengthen masonry structures. This study explores the feasibility of using natural fibers, specifically jute fiber-based materials, to improve masonry walls' structural and thermal performance through integrated upgrading/retrofitting. It thoroughly examines the application of jute nets (with mesh dimensions of 2.5 cm × 1.25 cm), jute fiber diatons, and jute fiber-reinforced composite mortar (containing 1% jute fiber by dry mortar weight) in masonry strengthening. The research assesses the impact of these materials on both the structural integrity and thermal efficiency of upgraded masonry walls. Remarkably, the use of Natural Fiber Textile Reinforced Mortar (NFTRM) led to an increase of more than 500% in the walls' load-bearing capacity and improved insulation by 36%. Additionally, the study incorporates detailed crack pattern analysis under in-plane cyclic loading using advanced DIC techniques. Therefore, integrated upgrading/retrofitting has been demonstrated to be an ideal solution against seismic action while enhancing the energy efficiency of a building
Natural Fiber TRM Systems for Sustainable Seismic Retrofitting of Masonry Walls: An Experimental Study Using Jute Fibers
No full textThe increasing demand for sustainable and resilient construction practices in seismic areas calls for innovative retrofitting solutions utilizing renewable resources. This study presents an experimental investigation on the structural performance of masonry walls upgraded using a Natural Fiber Textile Reinforced Mortar (NFTRM) system based on jute fibers. Hollow brick masonry walls were strengthened through the application of jute fiber nets, jute-based diatons (transverse connectors), and a composite mortar incorporating 1% jute fibers by weight. In-plane cyclic shear tests were performed under constant vertical loads to evaluate the improvement in shear strength ultimate capacity. The results show that the NFTRM system significantly enhances the load-bearing performance compared to unreinforced walls, reaching an ultimate shear strength of approximately 2.7–2.9 MPa. The outcomes highlight the potential of bio-based reinforcement systems to provide an eco-friendly and effective alternative for masonry strengthening in seismic regions, promoting both sustainability and resilience
Algorithm for damage detection in wind turbine blades using a hybrid dense sensor network with feature level data fusion
Full text linkDamage detection in wind turbine blades requires the ability to distinguish local faults over a global area. The implementation of dense sensor networks provides a solution to this local-global monitoring challenge. Here the authors propose a hybrid dense sensor network consisting of capacitive-based thin-film sensors for monitoring the additive strain over large areas and fiber Bragg grating sensors for enforcing boundary conditions. This hybrid dense sensor network is leveraged to derive a data-driven damage detection and localization method for wind turbine blades. In the proposed method, the blade's complex geometry is divided into less geometrically complex sections. Orthogonal strain maps are reconstructed from the sectioned hybrid dense sensor network by assuming different bidirectional shape functions and are solved using the least squares estimator. The error between the estimated strain maps and measured strains is extracted to define damage detection features that are dependent on the selected shape functions. This technique fuses sensor data into a single damage detection feature, providing a simple and robust method for inspecting large numbers of sensors without the need for complex model driven approaches. Numerical simulations demonstrate the proposed method's capability to distinguish healthy sections from possibly damaged sections on simplified 2D geometries.This is a manuscript of an article published as Downey, Austin, Filippo Ubertini, and Simon Laflamme. "Algorithm for damage detection in wind turbine blades using a hybrid dense sensor network with feature level data fusion." Journal of Wind Engineering and Industrial Aerodynamics 168 (2017): 288-296. DOI: 10.1016/j.jweia.2017.06.016. Posted with permission.</p
Dynamic characterization of a soft elastomeric capacitor for structural health monitoring applications
Full text linkA novel thin film sensor consisting of a soft elastomeric capacitor (SEC) for meso-scale monitoring has been developed by the authors. Each SEC transduces surface strain into a measurable change in capacitance. In previous work, the authors have shown that the performance of the SEC compares well with conventional resistive strain gauges, providing a resolution of 25 με using an inexpensive off-the-shelf data acquisition system for capacitance measurements. Here, we further the understanding of the thin film sensor by characterizing its dynamic behavior. The SEC is subjected to dynamic loads in bending mode. The study of Fourier and wavelet transforms indicates that the sensor can be used to identify dynamic inputs. Overall results demonstrate the promising capabilities of the thin film sensor at dynamic monitoring of civil structures.This proceeding is published as Hussam Saleem, Simon Laflamme, Filippo Ubertini, "Dynamic characterization of a soft elastomeric capacitor for structural health monitoring applications", Proc. SPIE 9061, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2014, 906115 (8 March 2014); doi: 10.1117/12.2045324. Posted with permission.</p
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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