1,720,974 research outputs found
A prediction-error-based method for data transmission and damage detection in wireless sensor networks for structural health monitoring
No full textIn this work, a prediction-error-based method that aims to reduce the amount of data transmission and storage in structural health monitoring wireless sensor networks (WSN) while keeping the damage detection capabilities intact is presented. WSNs offer tremendous promise for accurate and continuous structural monitoring using a dense array of inexpensive sensors and possess many advantages over conventional wired systems, particularly for large civil infrastructures. This paper validates the studied approach with the data collected during a test on a three-story steel frame mounted at the ELSA laboratory of the EU Joint Research Center in Ispra, Italy. The frame is tested with and without steel bracing, which results in non-sway behavior and sway frame responses. The excitation is provided by a shaker mounted on top of the frame. Accelerometer signals are collected by a multi-channel data acquisition system. The proposed method has been tested extensively via recorded experimental data and it offers considerable saving in transmitted energy while at the same time keeping the ability to detect changes or damage in the structure
Active and semi-active control of structures - theory and applications: A review of recent advances
No full textIt is internationally recognized that structural control was introduced in civil engineering through a pioneering article by Yao and through the implementations promoted by Kobori. The concepts of active and semi-active structural control in civil and infrastructure engineering date back 40 years and much progress has been recorded during these four decades. Periodically, state-of-the-art manuscripts have been published and technical books were also printed to testify the maturation of the topic. This article only covers the period from the second semester of 2009 to the first semester of 2011, emphasizing the developments in terms of theoretical, numerical and experimental studies, as well as the use of control algorithms and devices in actual implementations. It is observed that there are still several operational limitations
to prevent from the expected growth of the applications in standard design. Nevertheless, some innovative concepts help to foresee future developments within special sectors of applications
Digital Testing of a Control Law for an Active Mass Damper
No full textWithin this contribution, attention is focused on a laboratory frame model already
investigated in previous papers. It mounts on the top an active mass damper which is driven by two
controller: the first uses the feedback of accelerometers to elaborate a driven signal, the second
controller drives the engine to follow the path provided by the first controller. The second
controller was originally of the analogical type and is now replaced by a digital substitute. The first
controller was conceived as wired to the accelerometers, but several wireless solutions for it are
proposed. The goal is to assess the performance achieved in different excitation situations
Removing Analog Links In Structural Control
No full textWireless technology is herein applied to implement a real-time communication link between the nodes of a control system. The purpose of this paper is to introduce a wireless embedded technology which enables to successfully implement the control system, to improve the expected structural safety, and to re-duce the high-costs of the current solutions. A prototype of the wireless structural sensing and control system was implemented and its performance is verified and validated by analyzing the results of shaking table tests carried out on a reduced-scale structure. The feasibility of employing different control strategies is investi-gated. The feedback control algorithms are embedded between the wireless sensors and the actuator devices
An Active Mass Damper Based on Wireless Sensors and Digital Control
No full textWith the increasing demand on structural safety, the concept of structural control is conceived to protect the controlled structure by reducing the response due to external excitation, such as earthquake and strong wind. An active mass damper (AMD), i.e., the active form of the passive device known as tuned mass damper (TMD), is a typical way to implement structural control.
An existing laboratory three-storey steel frame was used to validate different control schemes. The frame is mounted on a single-axis shaking table simulating the ground excitation. Four single-axis wired accelerometers were mounted on each level (ground and floors of the frame). A mass cart driven by a DC motor, a DC motor position analog controller, and a controller board complete the early bed-test realization. Recently wireless sensors and a digital position controller were introduced to update the AMD performance.
In this paper the frame specimen is simulated by a numerical model allowing the authors to design and test the control laws without any risk of damaging the physical model. Such a modeling is pursued by an approach different from the one adopted in early studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Distribution of large-earthquake input energy in viscous damped outrigger structures
No full textThis article provides an analytical framework to assess the distribution of seismic energy in outrigger structures equipped with viscous dampers. The principle of damped outriggers for seismic control applications lies on the assumption that the total earthquake energy will be absorbed by the dampers, as the rest of the structure remains elastic during the seismic event. Nevertheless, under large or severe earthquake-induced motion, some plastic hinges or failures may be produced in the structure before the dampers are able to dissipate the total input energy. Therefore, hysteretic behaviour of the host structure need to be evaluated along the dampers’ performance in order to determine how the earthquake input energy is distributed by all the components. In order to effectively assess the inter-dependency between structural properties of tall buildings equipped with damped outriggers and ground motion characteristics of large earthquakes in the control performance, a parametric study -considering building predominant period, position of the outrigger, damping coefficient, and stiffness ratio core/perimeter columns- on the nonlinear behaviour of two building models –fixed and with viscous damper - is examined under two large-earthquake records. The results show that the use of passive control –viscous dampers- gradually reduce the potential of damage in the building structure as they reduce both the input and the hysteretic energy demands, and thus eventually extending the capabilities of the damped outrigger to large-earthquake induced motion control.Accepted Author ManuscriptOLD Structural Desig
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