To see the other types of publications on this topic, follow the link: Passive damper.
Dissertations / Theses on the topic 'Passive damper'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Passive damper.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Chey, Min Ho. "Passive and Semi-Active Tuned Mass Damper Building Systems." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2007. http://hdl.handle.net/10092/3431.
Full textAbstract:
This thesis explores next generation passive and semi-active tuned mass damper (PTMD and SATMD) building systems for reducing the seismic response of tall structures and mitigating damage. The proposed structural configuration separates the upper storey(s) of a structure to act as the 'tuned' mass, either passively or semi-actively. In the view point of traditional TMD system theory, this alternative approach avoids adding excessive redundant mass that is rarely used. In particular, it is proposed to replace the passive spring damper system with a semi-active resetable device based system (SATMD). This semi-active approach uses feedback control to alter or manipulate the reaction forces, effectively re-tuning the system depending on the structural response. In this trade-off parametric study, the efficacy of spreading stiffness between resetable devices and rubber bearings is illustrated. Spectral analysis of simplified 2-DOF model explores the efficacy of these modified structural control systems and the general validity of the optimal derived parameters is demonstrated. The end result of the spectral analysis is an optimally-based initial design approach that fits into accepted design methods. Realistic suites of earthquake ground motion records, representing seismic excitations of specific return period probability, are utilised, with lognormal statistical analysis used to represent the response distribution. This probabilistic approach avoids bias toward any particular type of ground motion or frequency content. Statistical analysis of the performance over these suites thus better indicates the true overall efficacy of the PTMD and SATMD building systems considered. Several cases of the segregated multi-storey TMD building structures utilising passive devices (PTMD) and semi-active resetable devices (SATMD) are described and analysed. The SATMD building systems show significant promise for applications of structural control, particularly for cases where extra storeys might be added during retrofit, redevelopment or upgrade. The SATMD approach offers advantages over PTMD building systems in the consistent response reductions seen over a broad range of structural natural frequencies. Using an array of performance metrics the overall structural performance is examined without the typically narrow focus found in other studies. Performance comparisons are based on statistically calculated storey/structural hysteretic energy and storey/structural damage demands, as well as conventional structural response performance indices. Overall, this research presents a methodology for designing SATMD building systems, highlighting the adaptable structural configuration and the performance obtained. Thus, there is good potential for SATMD building systems, especially in retrofit where lack of space constrains some future urban development to expand upward. Finally, the approach presented offers an insight into how rethinking typical solutions with new technology can offer dramatic improvements that might not otherwise be expected or obtainable.
2
Sallar, Grace A. "Modeling and Validation of the Resettable Semi-Passive Stiffness Damper." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1417079222.
Full text
3
Bigdeli, Kasra. "Optimal placement and design of passive damper connectors for adjacent structures." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43015.
Full textAbstract:
Passive coupling of adjacent structures is known to be an effective method to reduce undesirable vibrations and structural pounding effects. Past results have shown that reducing the number of dampers can considerably decrease implementation costs and does not significantly decrease the efficiency of the system. The main objective of this thesis is the optimal design of a limited number of dampers to minimize the inter-story drift. In this thesis, we present a bi-level optimization algorithm to find the optimal arrangement and mechanical properties of dampers placed between two adjacent buildings to minimize the maximum inter-story drift during (simulated) earthquake conditions.
Under the assumption of equal damping coefficients for all dampers, the optimal damping configuration is found via five different approaches: exhaustive search, inserting dampers, inserting floors, locations of maximum relative velocity, and a genetic algorithm. Through several numerical tests, efficiency and robustness of each optimization method is examined. It is shown that the inserting damper method is the most efficient and reliable method, particularly for tall structures. It is also found that, assuming equal damping coefficients for all dampers, increasing the number of dampers can exacerbate the dynamic response of the system.
Finding an efficient method to optimize dampers’ locations, we focus on the optimization of the damping coefficients. Letting the dampers have varying damping coefficients, the optimization problem of damping coefficients is an n-dimensional optimization problem, whose objective function is provided via a simulation. Therefore, we use non-gradient based techniques for the inner-loop of the algorithm. We compare three different methods: a genetic algorithm (GA), a mesh adaptive direct search (MADS) algorithm, and the robust approximate gradient sampling (RAGS) algorithm. RAGS is a derivative free optimization (DFO) method that exploits the structure of the finite minimax problem. Using these techniques, we show that there exists a threshold on the number of dampers inserted with respect to the efficiency of the retrofitting system. Furthermore, we show that using a structured internal subroutine (such as RAGS) for the inner-loop of the bi-level problem greatly increases the efficiency of the retrofitting system.
4
Gutierrez, Soto Mariantonieta. "INVESTIGATION OF PASSIVE CONTROL OF IRREGULAR BUILDING STRUCTURES USING BIDIRECTIONAL TUNED MASS DAMPER." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354596462.
Full text
5
Kim, Hyeong Gook. "New passive damper systems for vibration control of residential houses and building structures." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/161001.
Full text
6
Chen, Chen. "Simulation, design and experimental validation of a passive magnetic damper for ultra-fast actuators." Thesis, KTH, Elektroteknisk teori och konstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153639.
Full textAbstract:
A contact system driven by a high energetic Thomson actuator requires to be decelerated from full speed down to zero. The forces originated from the interaction between a stationary copper tube and a moving array of magnets combined with plastic or ferromagnetic material are used to generate eddy-current damping. Five different configurations of small but strong (N52) neodymium magnets and spacers were benchmarked for simple free-fall damping. A comparison between experimental results and simulations (using COMSOL) has shown that the most effective damping is reached by two consecutive permanent magnets with opposite magnetization directions ,separated by low-carbon content steel concentrators(SN - Fe concentrator- NS). The proposed damper design is the result of the balance between various parameters such as magnet orientation topology in the array, spacer material and its dimensions, copper tube thickness and the air gap between copper tube and array. Furthermore, the design was scaled up and an actuator-drive system was added to perform more realistic tests, which demonstrated the damping effectiveness on a fast moving armature actuated by a Thomson coil energized by a capacitor bank. All models in the simulation predicted the damping effect in advance. Investigations were conducted with two cases: (1) A solid copper rod was supposed to pass through the magnet array; (2) A plastic shaft was applied to support the magnet array. Finally a damping prototype with a plastic shaft was built for completing damping tests. The results of these tests validated the numerical model with a high degree of accuracy.
7
Marian, Laurentiu. "The tuned mass damper inerter for passive vibration control and energy harvesting in dynamically excited structural systems." Thesis, City University London, 2016. http://openaccess.city.ac.uk/14884/.
Full textAbstract:
A novel passive vibration control configuration, namely the Tuned-Mass-Damper-Inerter (TMDI) is proposed in this work. The TMDI combines the “inerter”, a mechanical two-terminal flywheel device developing resisting forces proportional to the relative acceleration of its terminals, with the well-known and widely used in various passive vibration control applications Tuned-Mass-damper (TMD). Introduced as a generalization of the TMD, the TMDI takes advantage of the “mass amplification effect” of the inerter to achieve enhanced performance compared to the classical TMD. For linear harmonically excited primary systems, analytical closed-form expressions are derived for optimal TMDI design/tuning parameters using the well-established and widely applied for the case of the classical TMD semi-empirical fixed-point theory. It is shown that for the same attached mass the TMDI system is more effective than the classical TMD to suppress vibrations close to the natural frequency of the uncontrolled primary system, while it is more robust to de-tuning effects. Moreover, it is analytically shown that optimally designed TMDI outperforms the classical TMD in minimizing the displacement variance of undamped linear single-degree-of-freedom (SDOF) white-noise excited primary systems. For this particular case, optimal TMDI parameters are derived in closed-form as functions of the additional oscillating mass and the inerter constant. Furthermore, pertinent numerical data are furnished, derived by means of a numerical optimization procedure, for classically damped mechanical cascaded chain-like primary systems base excited by stationary colored noise. This exemplifies the effectiveness of the TMDI over the classical TMD to suppress the fundamental mode of vibration for linear MDOF structures. It is concluded that the incorporation of the inerter in the proposed TMDI configuration can either replace part of the TMD vibrating mass to achieve lightweight passive vibration control solutions, or improve the performance of the classical TMD for a given TMD mass. The TMDI is further applied for passive vibration control of seismically excited building structures. An input non-stationary stochastic process compatible with the elastic design spectrum of the European aseismic code provisions (EC8) is assumed. The effectiveness of the proposed TMDI configuration over the classical TMD is assessed by performing response history analyses for an ensemble of EC8 spectrum compatible field recorded strong ground motions. The optimally tuned TMDI solution achieves considerable reduction of the peak average top floor displacement and peak average top floor accelerations of the considered primary structures compared to the one achieved by the optimally designed classical TMD, assuming the same additional mass in both cases. Furthermore, the TMDI configuration achieves significant reduction in the maximum displacement of the additional oscillating mass. In this study, the primary structures are assumed to behave linearly in alignment with current trends in performance based requirements for minimally damaged structures protected by passive control devices. Furthermore, optimally designed TMDI is applied for vibration suppression and energy harvesting via an electromagnetic device which transforms the mechanical kinetic energy into electrical energy. Unlike the case of traditional energy harvesting enabled TMD systems, the amount of available energy to be harvested by the herein proposed TMDI-based harvester is leveraged by changing the intensity of the mass amplification effect of the inerter, through mechanical gearing, without changing the weight of the TMDI system. Therefore, the inclusion of the inerter adds a “degree of freedom” or a design parameter to the classical TMD-based harvesters allowing to control the trade-off between vibration suppression and energy harvesting in a more flexible manner. Overall, the herein reported numerical data and analytical work provide evidence that the TMDI offers a novel promising solution for passive vibration control and energy harvesting. Most importantly, it opens several new research paths involving numerical/parametric work, as well as, prototyping, experimental testing and field deployment.
8
Kline, Eric S. "Replacement of an active metatarsophalangeal joint with a passive spring-damper system for implementation in an ankle prosthesis." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105695.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (page 22).
Analytical modeling was used to determine the optimal configuration of a replacement metatarsophalangeal (MTP) joint to be used in a prosthetic ankle. A spring was added to the joint to store energy and release it during the part of the gait cycle where the highest torque is required, reducing the torque the motor must exert. A linear spring-damper system adapted for use on a rotational joint was found to exhibit similar behavior to the biological joint for the range of motion required. The optimal gear ratio for the ankle motor, spring constant, and damping constant for the MTP joint were found using a MATLAB program written for this purpose. A physical prototype was fabricated, and testing was performed on an Instron machine to validate the results.
by Eric S. Kline.
S.B.
9
Malher, Arnaud. "Amortisseurs passifs non linéaires pour le contrôle de l’instabilité de flottement." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLY010/document.
Full textAbstract:
Cette thèse est consacrée à l'étude d'amortisseurs passifs non linéaires innovants pour le contrôle de l'instabilité de flottement sur un profil d'aile à deux degrés de libertés. Lorsqu'un profil d'aile entre en flottement, il oscille de façon croissante jusqu'à se stabiliser sur un cycle limite dont l'amplitude peut être significative et détériorer sa structure. Le contrôle a ainsi deux objectifs principaux : retarder l'apparition de l'instabilité et réduire l'amplitude des cycles limites. Avant d'étudier l'influence des amortisseurs passifs, l'instabilité de flottement, et notamment le régime post-flottement, a été étudié. Une expérience de flottement sur une plaque plane a été menée et sa modélisation, prenant en compte le phénomène de décrochage dynamique, a été réalisée. Concernant le contrôle passif, le premier type d'amortisseur étudié est un amortisseur hystérétique réalisé à l'aide de ressorts en alliage à mémoire de forme. La caractéristique principale de tels amortisseurs est que leur force de rappel étant hystérétique, elle permet de dissiper une grande quantité d'énergie. L'objectif principal est ainsi de réduire l'amplitude des cycles limites provoqués par l'instabilité de flottement. Cet effet escompté a été observé et quantifié expérimentalement et numériquement à l'aide de modèles semi-empiriques. Le second type d'amortisseur utilisé est un amortisseur non linéaire de vibration accordé. Il est composé d'une petite masse connectée au profil d'aile à l'aide d'un ressort possédant une raideur linéaire et une raideur cubique. La partie linéaire de ce type d'amortisseur permet de retarder l'apparition de l'instabilité tandis que la partie non linéaire permet de réduire l'amplitude des cycles limites. L'influence de l'amortisseur non linéaire de vibration accordé a été étudiée analytiquement et numériquement. Il a été trouvé que l'apparition de l'instabilité est significativement retardée à l'aide de cet amortisseur, l'effet sur l'amplitude des cycles limites étant plus modesteThe aim of this thesis is to study the effect of passive nonlinear absorbers on the two degrees of freedom airfoil flutter. When an airfoil is subject to flutter instability, it oscillates increasingly until stabilizing on a limit cycle, the amplitude of which can be possibly substantial and thus damage the airfoil structure. The control has two main objectives : delay the instability and decrease the limit cycle amplitude. The flutter instability, and the post-flutter regime in particular, were studied first. A flutter experiment on a flat plate airfoil was conducted and the airfoil behavior was modeled, taking into account dynamic stall. Regarding the passive control, the first absorber studied was a hysteretic damper, realized using shape memory alloys springs. The characteristic of such dampers is their hysteretic restoring force, allowing them to dissipate a large amount of energy. Their main goal was thus to decrease the limit cycle amplitude caused by the flutter instability. This expected effect was observed and quantified both experimentally and numerically, using heuristic model. The second absorber studied was a nonlinear tuned vibration absorber. This absorber consists of a light mass attached to the airfoil through a spring having both a linear and a cubic stiffness. The role of the linear part of such absorber was to repel the instability threshold, while the aim of the nonlinear part was to decrease the limit cycle amplitude. It was found, analytically and numerically, that the instability threshold is substantially shifted by this absorber, whereas the limit cycle amplitude decrease is relatively modest
10
Rai, Tannaw. "Parametric study of offshore structures with magneto-rheological tuned liquid column damper." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Find full textAbstract:
The master thesis work involved the implementation of Magneto-rheological tuned liquid damper for the mitigation of undesired vibration caused in offshore structures. The research begins with the study of passive tuned liquid column damper with uniform and non-uniform cross-section, coupled with an offshore structure under random wave force. The results show that increasing the density of the liquid used in the TLCD system gives better results, which provides an opportunity to use fluids with varying density and possibility to modify the conventional passive system into a semi-active damping system. Therefore, the normal fluid is switched with a magnetic fluid which has the ability to change its yield strength under an applied magnetic field.
There are two different approaches used in the study to formulate the mathematical model of the semi-active MR-TLCD. The first approach is based on using the magnetic force as an additional stiffness while the second approach is based on using the yield strength of the liquid as an additional damping force in the system. As a result, the efficiency of the semi-active MR-TLCD system was found to be better than the conventional passive TLCD system.
11
Valdebenito, Galo E. "Passive Seismic Protection of Cable-Stayed Bridges Applying Fluid Viscous Dampers under Strong Motion." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/6264.
Full textAbstract:
Terremotos recientes han demostrado la gran vulnerabilidad de algunos puentes ante movimiento fuerte. Los de tipo atirantado constituyen una tipología estructural muy atractiva, y que actualmente es empleada para muchos fines prácticos, por lo que es necesaria su protección sísmica. Entre las actuales estrategias de protección, el uso de dispositivos pasivos es la más robusta, económica y apropiada opción para mejorar el desempeño sísmico de estructuras, de entre los que destacan los sistemas de disipación de energía adicional como una buena alternativa. Debido a sus capacidades, fácil recambio y mantención, así como su buen comportamiento mecánico, los amortiguadores de fluidos viscosos son un excelente sistema de disipación de energía para proteger grandes estructuras contra eventos sísmicos intensos. Es por ello que el análisis, evaluación y comparación de la respuesta sísmica no lineal de puentes atirantados de hormigón, con y sin la incorporación de amortiguamiento viscoso suplementario, con el propósito de investigar su efectividad ante eventos sísmicos, es el principal objetivo de esta investigación aplicada. Para alcanzar lo antes expuesto, se definieron previamente ocho modelos teóricos de puentes atirantados basados en los internacionalmente conocidos puentes de Walter [Walter, 1999], considerando variaciones del esquema de atirantamiento, nivel del tablero, tipo de tablero y espaciamiento de los cables. Como punto de partida para el análisis dinámico no lineal, se realizó un análisis estático no lineal para todos los casos. Luego, se llevó a cabo una caracterización dinámica de los puentes mediante un análisis modal. Como primera aproximación a la respuesta sísmica de los modelos, se ejecutó un análisis mediante espectros de respuesta para cada caso, con el propósito de comparar el comportamiento sísmico en función de las principales variaciones consideradas, y para seleccionar los dos modelos más representativos para ser analizados usando análisis no lineal paso-a-paso. En seguida, se analizaron las estructuras elegidas en el paso previo mediante uso de análisis temporal no lineal por integración directa, sin la consideración de amortiguamiento viscoso suplementario, y tomando en cuenta sismos de campo lejano y campo cercano. En este sentido, se aplicaron cinco eventos sísmicos artificiales para el análisis de campo lejano, y cinco eventos reales que incorporasen pulsos de velocidad de período largo para el análisis de campo cercano, según el Capítulo 3. Finalmente, el análisis de la ubicación óptima de los amortiguadores, un estudio paramétrico tendiente a seleccionar los parámetros óptimos de los mismos, y el análisis paso-a-paso no lineal considerando los amortiguadores viscosos definitivos, fueron investigados con la idea de comparar las respuestas en función de la naturaleza del evento sísmico y el tipo de atirantamiento de los cables, considerando los mismos eventos sísmicos antes expuestos.
Los resultados de la investigación muestran que la aplicación de amortiguamiento viscoso suplementario es una eficiente estrategia para incrementar el amortiguamiento de una estructura, absorbiendo una gran cantidad de la energía de entrada, y controlando la respuesta de estructuras de período largo, sobre todo en la dirección longitudinal, en donde se manifiestan las mayores respuestas. Más de un 55% de la energía de entrada puede ser disipada usando éstos dispositivos, los cuales resultan ser igualmente efectivos para sismos de campo lejano y campo cercano, con independencia del esquema de atirantamiento empleado, por lo que constituyen una excelente estrategia de protección pasiva. Debido a la gran no linealidad de éstas estructuras, el método del espectro de respuesta debe ser considerado sólo como primera aproximación al problema, y para propósitos comparativos. Para resultados más precisos, y para aplicaciones de diseño, el análisis no lineal paso-a-paso es siempre la mejor opción. Por otro lado, ésta investigación prueba el despreciable efecto del esquema de atirantamiento en la respuesta sísmica, así como el importante aumento de la respuesta cuando son tomados en cuenta los efectos tipo pulso de la directividad de la falla, característicos de sismos de fuente cercana.
Recent seismic events have demonstrated the vulnerability of some bridges under strong ground motions. Cable-stayed bridges are an attractive bridge typology currently used for many practical purposes, constituting important structural systems to be protected against earthquakes. Amongst the current seismic protection strategies, the use of passive devices is the most robust, economic and well-suited option to improve the seismic performance of structures, in which additional energy dissipation systems is good choice. Because of their capacities, easy replacement and maintenance, as well as their interesting mechanical properties, fluid viscous dampers could be an excellent additional energy dissipation system to protect large structural systems against strong earthquakes. For that reason, the analysis, assessment and comparison of the nonlinear seismic response of concrete cable-stayed bridges, with and without the incorporation of nonlinear fluid viscous dampers in order to investigate their effectiveness for seismic protection purposes, is the main objective of this applied research.
To reach the proposed objectives, firstly, eight theoretical cable-stayed bridge models based on the well-known Walter's Bridges [Walter, 1999] were defined; considering variations of the stay cable layout, deck level, deck type and stay spacing. As a starting point of the nonlinear dynamic analysis, a nonlinear static analysis was performed for all the cases. After that, the dynamic characterization of the models was carried out by means of a modal analysis. As a first approach of the seismic response of the bridges, response spectrum analysis was performed in order to compare the seismic behaviour as function of the main variations considered, and to select the two most representative bridges to be analyzed using nonlinear time history analysis. The following stage was the seismic analysis of the selected bridge models from the previous step, applying nonlinear direct integration time history analysis, without additional energy dissipation devices, and considering both far-fault and near-fault ground motions. In these sense, five artificially generated earthquake events were considered for the far-fault analysis, as long as five real earthquake events containing long-period velocity pulses were included for the near-fault analysis, according to Chapter 3. Finally, the analysis of the optimal layout of the dampers, a parametric study to select the optimal damper parameters and the nonlinear step-by-step analysis considering the incorporation of the definitive fluid viscous dampers were investigated in order to compare the seismic responses as a function of the earthquake nature and stay cable layout, taking into account the same earthquake events before mentioned.
Results of this investigation show that application of fluid viscous dampers as additional passive energy dissipation systems is a very efficient strategy to increase the damping of a structure, absorbing a significant amount of the seismic input energy, and controlling the seismic response of long-period structures, mainly in the longitudinal direction, where the main responses occur. More than 55% of the input energy can be dissipated with these devices, being equally efficient for far-fault and near-fault ground motions, independent on the stay cable layout, which constitutes a very promising strategy to protect cable-stayed bridges against earthquakes. Because of the highly nonlinear behaviour of those structures, response spectrum analysis must be considered only as first approach to the seismic response and for comparative purposes. For more accurate analysis results, and for design applications, nonlinear time-history analysis is a necessary choice. Likewise, it is demonstrated that the effect of the stay cable layout on the nonlinear seismic response of the bridges is not very important, as well as an important increase of the seismic response when forward rupture directivity pulse effects are considered, a characteristic of near-source ground motions.
12
Malher, Arnaud. "Amortisseurs passifs non linéaires pour le contrôle de l’instabilité de flottement." Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLY010.
Full textAbstract:
Cette thèse est consacrée à l'étude d'amortisseurs passifs non linéaires innovants pour le contrôle de l'instabilité de flottement sur un profil d'aile à deux degrés de libertés. Lorsqu'un profil d'aile entre en flottement, il oscille de façon croissante jusqu'à se stabiliser sur un cycle limite dont l'amplitude peut être significative et détériorer sa structure. Le contrôle a ainsi deux objectifs principaux : retarder l'apparition de l'instabilité et réduire l'amplitude des cycles limites. Avant d'étudier l'influence des amortisseurs passifs, l'instabilité de flottement, et notamment le régime post-flottement, a été étudié. Une expérience de flottement sur une plaque plane a été menée et sa modélisation, prenant en compte le phénomène de décrochage dynamique, a été réalisée. Concernant le contrôle passif, le premier type d'amortisseur étudié est un amortisseur hystérétique réalisé à l'aide de ressorts en alliage à mémoire de forme. La caractéristique principale de tels amortisseurs est que leur force de rappel étant hystérétique, elle permet de dissiper une grande quantité d'énergie. L'objectif principal est ainsi de réduire l'amplitude des cycles limites provoqués par l'instabilité de flottement. Cet effet escompté a été observé et quantifié expérimentalement et numériquement à l'aide de modèles semi-empiriques. Le second type d'amortisseur utilisé est un amortisseur non linéaire de vibration accordé. Il est composé d'une petite masse connectée au profil d'aile à l'aide d'un ressort possédant une raideur linéaire et une raideur cubique. La partie linéaire de ce type d'amortisseur permet de retarder l'apparition de l'instabilité tandis que la partie non linéaire permet de réduire l'amplitude des cycles limites. L'influence de l'amortisseur non linéaire de vibration accordé a été étudiée analytiquement et numériquement. Il a été trouvé que l'apparition de l'instabilité est significativement retardée à l'aide de cet amortisseur, l'effet sur l'amplitude des cycles limites étant plus modesteThe aim of this thesis is to study the effect of passive nonlinear absorbers on the two degrees of freedom airfoil flutter. When an airfoil is subject to flutter instability, it oscillates increasingly until stabilizing on a limit cycle, the amplitude of which can be possibly substantial and thus damage the airfoil structure. The control has two main objectives : delay the instability and decrease the limit cycle amplitude. The flutter instability, and the post-flutter regime in particular, were studied first. A flutter experiment on a flat plate airfoil was conducted and the airfoil behavior was modeled, taking into account dynamic stall. Regarding the passive control, the first absorber studied was a hysteretic damper, realized using shape memory alloys springs. The characteristic of such dampers is their hysteretic restoring force, allowing them to dissipate a large amount of energy. Their main goal was thus to decrease the limit cycle amplitude caused by the flutter instability. This expected effect was observed and quantified both experimentally and numerically, using heuristic model. The second absorber studied was a nonlinear tuned vibration absorber. This absorber consists of a light mass attached to the airfoil through a spring having both a linear and a cubic stiffness. The role of the linear part of such absorber was to repel the instability threshold, while the aim of the nonlinear part was to decrease the limit cycle amplitude. It was found, analytically and numerically, that the instability threshold is substantially shifted by this absorber, whereas the limit cycle amplitude decrease is relatively modest
13
Ontiveros, Pérez Sergio Pastor. "Otimização simultânea de posições e forças de amortecedores de vibração por atrito para controle de vibrações de estruturas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/96355.
Full textAbstract:
A otimização de amortecedores é uma área nova que vem sendo explorada nos últimos anos. Existem vários métodos clássicos e outros mais recentes que estão disputando em confiabilidade, eficiência e rapidez na obtenção de um resultado ótimo. Os algoritmos de otimização são classificados em determinísticos, que utilizam a informação do gradiente, ou seja, usam os valores das funções e suas derivadas, e os meta-heurísticos são algoritmos aleatórios que são métodos probabilísticos não baseados em gradiente, utilizando somente a avaliação da função objetivo. O Firefly Algorithm é um algoritmo meta-heurístico relativamente recente inspirado no comportamento da luz dos vagalumes. Este trabalho propõe um método para a otimização de amortecedores por atrito utilizando algoritmo meta-heurístico. O método proposto é testado em dois edifícios, de nove e dezesseis andares, submetidos a duas excitações sísmicas cada. A otimização tem um objetivo principal: diminuir a resposta dinâmica em termos do deslocamento máximo no topo das estruturas obtido através de um algoritmo programado baseado no método das diferenças finitas centrais, otimizando o local de um número máximo de amortecedores e as forças de atrito dos mesmos. Para o caso da estrutura de nove andares o número máximo de amortecedores é de quatro e para o caso da estrutura de dezesseis andares o número máximo é seis. Os resultados demostraram que, para os dois casos estudados, o deslocamento no topo da estrutura diminui em mais de 50%, concluindo-se que o método programado é eficaz assim como o Firefly Algorithm é adequado para obter as posições e as forças de atrito ótimas. Portanto, acredita-se que o método proposto poderá ser utilizado como uma ferramenta útil para auxiliar no projeto de amortecedores por atrito.The damper’s optimization is a new area that has been explored in recent years. There are several classics and newer methods that are competing in reliability, efficiency and speed in achieving a great result. The algorithms are classified as deterministic, using gradient information, or use the function values and their derivatives, and meta- heuristic optimization algorithms are random probabilistic methods that are not based on gradient using only the evaluation of the objective function. The Firefly Algorithm is a relatively new meta-heuristic algorithm inspired on the behavior of the light of fireflies. This work proposes a method for the friction damper’s optimization using meta-heuristic algorithm. The proposed method is tested in two structures: a nine story building and a sixteen story building. They were submitted to two seismic excitations each. The optimization has one main goal: to reduce the dynamic response in terms of the maximum displacement at the top of the structures obtained by a programmed algorithm based on the central finite difference method, optimizing the location of a maximum number of dampers and their friction’s forces. In the case of the nine story building, the maximum number of dampers is four, and in the case of the sixteen story building the maximum number is six. The results showed that for the two cases studied, the displacement at the top of the structure decreases by more than 50%, concluding that the programmed method is effective and the Firefly Algorithm is appropriate to get the positions and friction’s forces optimal. Therefore, it is believed that the proposed method can be used as a tool to aid in the design of friction dampers.
14
Allani, Anissa. "Conception et optimisation d'amortisseurs à masse accordée pour les structures du génie civil." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1137/document.
Full textAbstract:
Le travail de thèse s’appuie sur un recueil exhaustif des travaux effectués dans le domaine du contrôle des vibrations auxquels sont soumis les ouvrages génie civil. Une contribution innovante et originale est apportée et permet de classifier, de généraliser et d’optimiser certains critères dans le but d’assurer une conception optimale de divers dispositifs d’atténuation des vibrations, et ce, selon leur application. L’un des objectifs de la thèse a donc consisté à traiter ces critères de manière originale. Après avoir résolu le problème dit « direct » s’appuyant sur la modélisation des systèmes dotés d’un ou de plusieurs AMAs, nous nous sommes intéressés au problème dit « indirect » en envisageant divers critères d’optimisation. Ainsi, plusieurs critères d’optimisation des paramètres mécaniques de plusieurs AMAs appliqués à un système principal comportant 1 ou plusieurs degrés de liberté peuvent être utilisés. L’excitation du système principal est envisagée de deux manières, soit à sa base (en vue d’une application à la sismique), soit au niveau de la structure (en vue d’une application aux effets du vent).Des simulations numériques sont réalisées dans le but d’étudier la performance de chaque modèle optimisé en se fondant sur des approches fréquentielles et temporelles. La robustesse de chaque critère d’optimisation face aux incertitudes liées au changement des paramètres physiques de la structure principale a été examinée. Nous avons également étudié la sensibilité des critères par rapport aux incertitudes des paramètres optimisés des AMAs. La conception et l’optimisation de p AMAs placés en parallèle pour un système principal à Nddl, a constitué une nouvelle contribution originale dans le cadre de cette thèse. Dans ce contexte, lors d’une sollicitation sismique, nous estimons la contribution de chaque mode dans la structure principale et nous conservons seulement les modes de vibrations qui ont un rapport de masses modales cumulées supérieur à 90%. Le choix du critère d’optimisation s’appuie seulement sur les étages les plus sensibles aux modes conservés et permet ainsi de tenir compte des modes élevés de la structure principale. Dans le but de limiter les dommages subis par les constructions du génie civil lors de sollicitations sismiques, nous cherchons à évaluer l’efficacité des AMAs afin d’atténuer les réponses temporelles sismiques. Ainsi une étude comparative est réalisée en appliquant quatre séismes réels sur les modèles optimisés. Afin d’illustrer les résultats obtenus, des tests de caractérisation d’un AMA utilisant un amortissement par courants de Foucault et un ajustement de la rigidité, ont été menés. Ils ont permis d’obtenir une validation expérimentale du modèle et du critère d’optimisation adoptéThe architectural demand and the desire to reduce costs permit the construction of light structures with innovating shapes. The great flexibility of these structures makes them increasingly sensitive to the external dynamic loads such as traffic, wind and earthquakes. Vibration control techniques allow to construct modern buildings increasingly slender, and, whether they are economic or architecturally audacious. Instead of modifying the geometrical and mechanical characteristics of a structure, vibration control consists in producing reaction forces which are opposed to the negative effects of the external excitations when they appear. This technological advance has the great advantage to not influencing planners and architects’ work and it provides them with additional creative options in both geometrical and mechanical characteristics of buildings. We restrict our focus to passive vibration control. Among available passive vibration absorber systems, Tuned Mass Dampers (TMDs) were selected for their simplicity and reliability. A TMD consists of a mass, a dashpot, and a spring, and is commonly attached to a vibrating primary system to suppress undesirable vibrations. The performance of TMDs is strongly affected by the adjustment of their parameters. The problem is the optimization of the mechanical parameters of TMD and their location in order to attenuate vibrations of the main structure. This thesis is based on understanding the dynamic characteristics of TMD. It aims to make an innovative and original contribution to classify, generalize and optimize some criteria in order to ensure an optimal design of TMDs, depending on their application. Our work consisted to treat these criteria in an original way. After solving the direct problem based on the modelling of systems with one or several TMD, we tackled the indirect problem by considering various optimization criteria. Thus, several optimization criteria of the mechanical parameters of TMDs applied to a main system (single (SDOF) or multiple degrees of freedom (MDOF)) are used. The excitation of the main system can be done in two different ways; either on the base (for seismic application) or on the structure (for wind effects).Numerical simulations based on a time and frequency approach are used to examine the performance of each optimized model. The robustness of each optimization criterion is assessed by taken into account the uncertainties related to the change of the physical parameters of the main structure. Such problems can be discussed by considering sensitivity analysis for criteria under uncertainty of the optimum TMD parameters. A new and original contribution of this thesis is the design and optimization of multiple TMDs in parallel with a MDOF main structure. In this context, during seismic loads, modes in the main structure with relatively high effective masses can be readily excited by base excitation. Afterwards, optimization criterion can be developed based on the most sensitive storeys to vibration modes which are a cumulative modal effective mass fraction exceeding 90%. To protect structures under earthquake loads, we seek to assess the effectiveness of TMDs in mitigating the response of structure under different real earthquakes. A comparative study is then achieved with four real earthquakes applied on systems with TMD optimized parameters. To illustrate the results obtained, characterization tests are conducted on a TMD with damping by eddy currents effect and adjustable stiffness. They allow the validation of the model and optimization criterion adopted
15
Eltaeb, Mohamed A. "Active Control of Pendulum Tuned Mass Dampers for Tall Buildings Subject to Wind Load." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton150343994189116.
Full text
16
Zhou, Shaoyi. "Advances in passive and active damping techniques." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI066.
Full textAbstract:
Les systèmes mécaniques (e.g. structures flexibles) sont généralement peu amortis, et par conséquent des vibrations de fortes amplitudes peuvent apparaitre. Il apparait nécessaire de développer des stratégies de contrôle vibratoire pour atténuer ces vibrations mécaniques. Cette thèse a pour objectif de développer plusieurs techniques d'amortissement de vibration passives ou actives. La première partie porte sur l'utilisation d'un “inerter” pour améliorer les performances de contrôle vibratoire de deux dispositifs existants, l'amortisseur à masse accordée (TMD) et deux TMDs placés en série (SDTMD). Dans le cas avec un TMD, on considère un système mécanique avec incertitudes ainsi que son optimisation H-infinity (worst-case optimization) en adoptant une approche purement algébrique. Dans le cas de SDTMD, on vise à contrôler la vibration d'un système déterministe. Son optimisation H-infinity s'effectue ici en utilisant une version étendue de la théorie de points fixes (FPT). Dans une seconde partie, on cherche à améliorer les performances de ce type de dispositif en positionnant un élément linéaire de raideur négative entre la base et la masse accordée. Deux cas d'étude sont menés: le TMD seul et celui basé sur l'inerter (IDVA). Les deux dispositifs ont une configuration non-traditionnelle, dont la masse accordée est liée à la base par l'intermédiaire d'un amortisseur visqueux ou un réseau mécanique basé sur l'inerter. La réalisation de ces dispositifs non-traditionnelles avec ou sans raideur négative et leurs shunts piézoélectriques sont étudiés et une analogie électromécanique est établie. Cette analogie permet d'étendre l'applicabilité des amortisseurs mécaniques et de faciliter les réglages. Dans la dernière partie, deux techniques d'amortissement actif et semi-actif sont développées. La première stratégie concerne une loi de contrôle hybride applicable au TMD et à l'IDVA. Le contrôleur proposé est composé d'un seul ou plusieurs compensateurs identiques, qui est caractérisé par un pôle à l'origine et deux zéros coïncidents réels. Les expressions analytiques sont développées dans les deux cas. La seconde technique de contrôle s'appuie sur l'atténuation de vibration par shunt électromagnétique (EMSD), pour laquelle aucun capteur est requis. Une inductance négative (NI) est employée dans les shunts électromagnétiques afin d'améliorer l'amortissement. Trois architectures possibles de NI dans un EMSD sont évaluées à travers le facteur de couplage électromécanique, qui quantifie l'efficacité de conversion énergétique entre les domaines mécanique et électrique. Finalement, six shunts électromagnétiques utilisant des NIs sont optimisés et analysésMechanical systems (e.g. flexible structures) are usually lightly damped so that they vibrate severally in response to dynamic loads. Therefore, vibration control strategies should be adopted in order to reduce the undesired vibration of mechanical systems. The objective of this thesis is to develop multiple vibration control techniques, which are either passive or active. The first part focuses on the application of inerter to enhance the vibration control performance of two existing control devices, the tuned mass damper (TMD) and the series double TMD (SDTMD). The inerter is employed to relate the tuned mass to the ground. In the case of TMD, a mechanical system under stiffness uncertainty is considered and the worst-case H-infinity optimization is addressed by means of an entirely algebraic approach. In the case of SDTMD, the vibration of a deterministic mechanical system is to be controlled and the H-infinity optimal design is carried out via an extended version of fixed points theory (FPT). Instead of using the inerter, the second part consists in improving the control effect by incorporating a linear negative stiffness between the ground and the tuned mass. Two case studies are conducted based on the non-traditional TMD and inerter-based dynamic vibration absorber (IDVA), whose tuned mass is related to the ground by a viscous damper or an inerter-based mechanical network, respectively. Later, the exact electrical realization of non-traditional configurations with or without negative stiffness is proposed, which is based on the piezoelectric transducer enclosed by a particular shunt circuit. This electromechanical analogy enables to extend the applicability of mechanical control devices and to facilitate the precise tuning. In the last part, active and semi-active vibration control techniques are developed. The first strategy consists in enhancing the control capability of passive TMD and IDVA by feeding back the displacement signal of mechanical system to the electromagnetic actuator. The proposed controller can be regarded as one or multiple basic units arranged in series, which is featured by one pole at the origin and two coalesced zeros on the real axis. Distinguished from the previous strategy, the semi-active control technique is based on electromagnetic shunt damping (EMSD), therefore, no additional sensor is required to measure the information of mechanical system. In order to artificially increase the shunt damping performance, the employment of negative inductance (NI) in the shunt circuit is considered. Three possible layouts of NI in the EMSD are assessed in terms of the electromechanical coupling factor, which quantifies the energy conversion efficiency between mechanical and electrical domains. Finally, six types of shunt circuits are optimally tuned according to the FPT and the beneficial effect of NI and the influence of its layout can be underlined
17
GIOIELLA, LAURA. "External Dissipative Rocking System." Doctoral thesis, Università Politecnica delle Marche, 2017. http://hdl.handle.net/11566/245410.
Full textAbstract:
Questa tesi ha l'obiettivo di indagare il comportamento dinamico e sismico di edifici esistenti protetti con un sistema esterno di dissipazione basato sul rocking; esso è costituito da una struttura reticolare in acciaio, incernierata a livello di fondazione, il cui movimento oscillante attiva la dissipazione di energia, per mezzo di smorzatori viscosi situati alla base. Nell'ipotesi di comportamento elastico lineare sia del telaio, che della struttura dissipativa, vengono presentate l'equazione del moto del sistema accoppiato ed una generalizzazione del sistema ad un grado di libertà. Per risolvere il problema dinamico è possibile condurre analisi sia nel dominio del tempo, che in quello delle frequenze.
La soluzione nel dominio del tempo si basa su una formulazione alle variabili di stato che, tramite analisi modale complessa del sistema telaio da proteggere-struttura esterna di protezione passiva, permette di valutare l'influenza, sia sul comportamento dinamico che in termini di risposta sismica, dello smorzamento e della linearizzazione degli spostamenti forniti dalla struttura dissipativa. In particolare, la formulazione proposta, consente di valutare separatamente il contributo di ciascuno dei modi di vibrazione complessi del sistema sulla risposta sismica globale. Le analisi armoniche nel dominio delle frequenze, invece, sono particolarmente utili in quanto consentono di lavorare con un sistema algebrico piuttosto che differenziale. Inoltre, scegliendo di rappresentare l'input sismico come un processo stocastico stazionario, è possibile stabilire una relazione tra la densità spettrale di potenza (PSD) dell'input esterno e quella dei parametri di risposta di interesse, tramite analisi armonica del sistema.
Le prestazioni di due casi di studio sono valutate mediante analisi parametriche, riguardanti diversi livelli di smorzamento e rigidezza del sistema di protezione, sia con analisi nel tempo che in frequenza. Infine vengono presentati alcuni aspetti che necessitano di ulteriore approfondimento. Tra di essi la valutazione ed il confronto della performance sismica di smorzatori viscosi a comportamento lineare e non, dimensionati attraverso il criterio di uguaglianza dell'energia dissipata. Le prestazioni del sistema di protezione passiva indagato, vengono confrontate con un'altra configurazione esterna, che prevede l'accoppiamento del telaio con una struttura rigida di contrasto, nota in letteratura come sistema di smorzamento proporzionale alle masse. Infine viene condotta una prima analisi degli effetti dell'interazione terreno-struttura (SSI), mediante l'approccio alle sottostrutture.In this thesis the seismic performance of existing buildings frames coupled with an external dissipative rocking system is investigated; the arrangement consists of a steel truss, hinged at the foundation level, whose rocking motion promotes the dissipation of energy via viscous dampers located at the base. Under the assumption of linear elastic behaviour of both the frame and the dissipative structure, the equation of motion of the system are presented, together with a generalized Single Degree of Freedom (S-DOF) approximation of the system. This way, analysis through time-domain and frequency-domain are allowed for the investigation of the system dynamic behaviour. Time-domain analysis, based on a state space approach, leads to the complex modal analysis of the coupled system, which allows the evaluation of the influence of the added damping and of the displacements linearization, promoted by the external dissipative rocking system, on both the dynamic behaviour and the seismic response. In particular, the proposed formulation permits to evaluate separately the contribution of each of the complex vibration modes of the system to the global seismic response. On the other hand frequency-domain analysis is particularly useful for the problem under investigation because it allows to work with an algebraic system rather than a differential one. Furthermore by representing the seismic input in terms of a stationary stochastic process, a relation can be established between the Power Spectral Density (PSD) of the input and that of the response parameters of interest via harmonic analysis of the system. The performance of two case studies is evaluated by means of parametric analysis, involving added damping and stiffness, either through time- and frequency-domain. Finally, some aspects which need a deeper investigation are presented. Among them the evaluation and comparison between linear and non-linear fluid viscous dampers, dimensioned through dissipated energy criterion. The performance of the analyzed dissipative system, is compared with an alternative retrofitting configuration, consisting in the coupling with external stiff contrasting structure, known in literature as mass proportional damping system. At the end a first insight on the effects of Soil-Structure-Interaction (SSI), through the substructure approach, is provided.
18
Bauw, Grégory. "Amélioration des performances acoustiques et vibratoires des machines asynchrones par enroulement amortisseur." Thesis, Artois, 2018. http://www.theses.fr/2018ARTO0206.
Full textAbstract:
Ce travail présente une nouvelle technique permettant la réduction passive des bruits et vibrations d’origine magnétique des machines asynchrones triphasées grâce à un enroulement amortisseur connecté à des condensateurs. Les éléments nécessaires à la compréhension des phénomènes électromagnétiques, mécaniques et acoustiques, ainsi qu’un état de l’art des différentes techniques de réduction de bruit et vibrations sont d’abord donnés. Une partie de l’étude est ensuite consacrée au modèle de la machine asynchrone à enroulement amortisseur. Cette modélisation est basée sur le schéma monophasé équivalent de la machine et permet de mettre en évidence la réduction des harmoniques d’induction à l’origine des bruits et vibrations. Deux types de réduction de bruit sont décrits dans ce mémoire : celle du bruit provenant d’une alimentation de type M.L.I, d’une part, et du bruit provenant de phénomènes internes à la machine, d’autre part, comme les phénomènes d’encoches, la saturation ou l’excentricité. Pour chacun des deux cas, le schéma équivalent permettant de traduire le comportement de la machine est adapté et permet de choisir de manière optimale la valeur de condensateur à connecter à l’enroulement amortisseur. Une étude de dimensionnement permet également de discuter de l’impact de l’ajout de l’amortisseur sur l’encombrement, la masse et les performances de la machine. Des résultats expérimentaux montrent la validité et l’efficacité du système en termes de réduction des bruits et vibrations. La réduction du niveau de bruit global de la machine étudiée atteint 5dB(A) en alimentation réseau, et jusqu’à 10dB(A) en M.L.IThis work presents a new method allowing the passive reduction of magnetic noise and vibrations of three-phase induction machines using a damper winding connected to capacitors. The elements required for the understanding of the electromagnetic, mechanical and acoustic phenomena, as well as a state of the art of the different noise and vibrations reduction techniques are first given. A part of the study is then dedicated to the model of the induction machine with damper winding. This modeling is based on the equivalent single-phase circuit of the machine and makes it possible to highlight the reduction of the flux density harmonics responsible for noises and vibrations. Two types of noise reduction are described in this thesis: that of the noise due to PWM power supply on the one hand, and on the other, the noise due to internal phenomena such as slotting effects, saturation or eccentricity. For each case, the equivalent circuit allowing to translate the behavior of the machine is adapted and makes it possible to optimally choose the capacitor value to be connected to the damper. A design study also allows to discuss the impact of the addition of the damper on the size, weight and performances of the machine. Experimental results show the validity and effectiveness of the system in terms of noise and vibrations reduction. The global noise level reduction of the studied machine reaches 5dB(A) when the machine is fed by sine voltage, and up to 10dB(A) when PWM-fed
19
Přikryl, Matěj. "Hydrodynamické tlumiče na principu magnetické kapaliny." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318383.
Full textAbstract:
This diploma thesis covers the topic of magnetic fluids and their utilisation in hydrodynamic dampers. The first part of the work consists of research on the current state of technology in hydraulic dampers with the focus on dampers using magnetorhelogical fluid. This chapter is followed by research on magnetic fluids with regard to their physical properties and mathematical description, which is used for CFD simulation of flow. The second part deals with the computational simulation of the flow of MR liquid in real MR damper in order to determine the damping characteristic and it's comparison with the experimental data.
20
Ljumanovic, Lea. "Low cost passive dampers for highway traffic signs." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/702.
Full textAbstract:
A low cost passive mass-rubber damper is introduced in this work to mitigate damage of highway signs caused by ground motion and wind gusting. The damper is designed and constructed to alleviate stresses due to bending, shear, and fatigue loading. Lab experiments based on sign responses and strains were conducted in order to evaluate the damper effectiveness in extending the life of the sign structure. Experimental Modal Analysis was performed to deduce the modal parameters of the structure using Easy Analyst and ME'scope commercial software. Ground motion was simulated using a shaker table and lighten earthquake signals. The wind gusting is simulated by simply pulling the tip of the sign and then releasing it. The results have shown that the proposed damper was able to minimize the horizontal relative ground motion between the base of the structure and the ground, which is an indication of smaller shear forces. Strain results have shown that the proposed damper was able to lower the maximum strain by up 73 percent. Finally, the damper was very effective in filtering the high frequency components of the signals entering the system, minimizing by that failure due to high cycle fatigue.
21
Hendrix, Christopher (Christopher M. ). "Feasibility of passive electromagnetic dampers as energy harvesters in large structures." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82816.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 44).
There has been a trend in structural design toward energy efficient design and motion based design. The strategy of motion based design is controlling the movement of structures to meet certain dynamic response requirements by damping the structure. Structural damping dissipates the energy of external loads internally within the structure. A simple idea is to connect the two design strategies to control the motion of a structure while harvesting this dissipated energy by transducing it to electrical energy via passive electromagnetic damping. This study will attempt to determine the feasibility of using passive electromagnetic damping to control the motion and harvest the energy of damping of large scale structures.
by Christopher Hendrix.
M.Eng.
22
Paknejad, Seyedahmadian Ahmad. "Passive and Active Strategies for Vibration Control of Lightly Damped Structures." Doctoral thesis, Universite Libre de Bruxelles, 2021. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/325768.
Full textAbstract:
Lightweight designs in engineering applications give rise to flexible structures with extremely low internal damping. Vibrations of these flexible structures due to an unwanted excitation of system resonances may lead to high cycle fatigue failure and noise propagation. A common method to suppress the vibrations is to increase the damping of the system using one of the classical control techniques i.e. passive, active, and/or hybrid. Passive techniques are those control systems that are simply integrated into the structures with no need of external power source for their operations, like viscoelastic damping, piezoelectric and electromagnetic shunt damping, tuned mass damper, etc. However, the control performance of these systems, in terms of the damping ratio and the robustness to uncertainties, is highly limited to the system properties. For example, viscoelastic damping may not perform well at low frequencies and the performance of shunt damping is dependent on the electromechanical coupling between the structure and the transducer. To overcome the limitations associated with passive controls, it has been proposed to use active control systems, which are less sensitive to the system's parameters, to improve the control performance. It requires an integration of sensors and actuators with a feedback loop containing control laws. However, the high requirement of the external power source is not favorable for engineering applications where energy efficiency is the key parameter. The combination of active and passive strategies, known as hybrid control systems, can provide a fail-safe configuration with a high control performance and low power consumption. The price to pay for such configurations is the complexity of the design. This doctoral thesis first investigates the conceptual designs of all kinds of classical control systems for a simplified mechanical system. They include 1) the passive shunt using an electromagnetic transducer, 2) the active control system using positive and negative feedback, and 3) the hybrid electromagnetic shunt damper using both an active voltage source as well as an active current source. The next part of this thesis is focused on bladed structures as real-life applications which highly require vibration control due to their low internal damping. Because of practical reasons, piezoelectric transducers are used for the application of control systems. The finite element model of the structure is made first without piezoelectric patches to optimize the best locations of piezoelectric patches. Then, the model is updated with the piezoelectric patches to numerically simulate different control strategies. The experiments are performed to validate the numerical designs.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
23
Karunaratne, Nivithigala Polgaswatte Kasun Viraj. "Use of semi-active dampers in seismic mitigation of building structures." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/93350/1/Nivithigala%20Polgaswatte%20Kasun%20Viraj_Karunaratne_Thesis.pdf.
Full textAbstract:
This research provides information for providing the required seismic mitigation in building structures through the use of semi active and passive dampers. The Magneto-Rheological (MR) semi-active damper model was developed using control algorithms and integrated into seismically excited structures as a time domain function. Linear and nonlinear structure models are evaluated in real time scenarios. Research information can be used for the design and construction of earthquake safe buildings with optimally employed MR dampers and MR-passive damper combinations.
24
MOORHEAD, ALEX PATTEN. "THE DAMPED OSCILLATIONS OF PASSIVE LIMBS AND THEIR ROLE IN HUMAN LOCOMOTION MECHANICS." Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/605781.
Full textAbstract:
The mechanics of locomotion classically take into account the work done by muscle force to raise and accelerate the body center of mass and to accelerate limbs with respect to it at each step. This last component, named Internal Work (W_INT), considers only the cost to overcome segment inertia, inherently assuming frictionless joints. Thus, the unavoidable damping opposing segmental oscillation due to anatomical structures within or around the pivoting centers has never been measured so far.
The frictional coefficient (b, N.m.s.rad-1) of such a biological rotational damper has been here assessed by sampling the time course of passive oscillation (with respect to the vertical axis) of upper and lower limbs and by analyzing its motion. This experiment (straight pendulum) was performed to assess joint energy dissipation during the swing phase of locomotion. A custom mathematical model, leading to a 2nd Order Non-Linear Ordinary Differential Equation, allowed to infer b values for upper (bUU = 0.39 ± 0.08) and lower (bUL = 2.24 ± 0.56 N.m.s.rad-1) limbs in 16 healthy males. Phase planes ensured that no muscle activity was involved. In the same population, the passive swing of a lower limb, behaving as an inverted pendulum after a push (body upside-down), was also sampled while loading the leg as to replicate the compressive stress to which the hip joint is exposed during stance phase. Loads ranged from 0 N (mass of leg only) to 118 N. Damper values (b) for the inverted swing of a loaded lower limb increased with the load and ranged from 4.89 ± 1.29 to 8.92 ± 1.74 N.m.s.rad-1.
The influence on locomotion mechanics has been here evaluated. In walking, for instance, each step includes 3 'passively' swinging, unloaded segments (2 upper limbs and the swinging lower limb with joints under tensile stress) and 1 'actively' oscillating, almost fully loaded segment (stance lower limb, joint under compressive stress). The actual experimental results have been combined to provide an estimate of the internal mechanical work due to tissue and joint damping. In walking that is comparable (and should be added) to the estimate obtained by means of a kinematics-based model (Minetti, 1998) and experimental data from the literature of the traditional ‘kinematic’ W_INT. In the discussion, the potential overestimation and underestimation of those two types of internal work are presented, together with the implications of the presented additional work (and its metabolic equivalent) to the energy balance and efficiency of human locomotion.
25
Tell, Sarah. "Vibration mitigation of high-speed railway bridges : Application of fluid viscous dampers." Licentiate thesis, KTH, Bro- och stålbyggnad, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-205672.
Full textAbstract:
At the moment of writing, an expansion of the Swedish railway network has started, by constructions of new lines for high-speed trains. The aim is to create a high-speed connection between the most populous cities in Sweden - Stockholm, Göteborg and Malmö, and the rest of Europe. Thereby, the likelihood of faster, longer and heavier foreign trains crossing the Swedish lines is increased. However, this could be problematic since the dynamic response in railway bridges and, consequently, the risk of resonance increases with increasing train speeds. Bridges are usually designed based on contemporary conditions and future requirements are rarely considered, due to e.g. cost issues. Prospectively, the dynamic performance of existing bridges may become insufficient. Hence, the current expansion of the high-speed railway network results in an increased demand of innovative design solutions for new bridges and cost-efficient upgrading methods for existing lines. The aim of the present thesis is to propose a vibration mitigation strategy suitable for new and existing high-speed railway bridges. The main focus is a retrofit method with fluid viscous dampers installed between the bridge superstructure and the supports, which is intended to reduce the vertical bridge deck acceleration below the European design code limits. Furthermore, the intention is to investigate the efficiency of such a system, as well as to identify and analyse the parameters and uncertainties which could influence its functionality. In order to examine the applicability of the proposed retrofit, case studies, statistical screenings and sensitivity analyses are performed and analysed. Two different models, a single-degree-of-freedom system and a finite element model, are developed and compared. From the different models, it is possible to study the influence from the damper parameters, the variability of the material properties and different modelling aspects on the bridge response. After the installation of the fluid viscous dampers, it is found that the acceleration level of the bridge deck is significantly reduced, even below the design code requirements.I skrivande stund har en utbyggnad av det svenska järnvägsnätet initierats. Målet är att skapa en höghastighetsanslutning mellan de folkrikaste städerna i Sverige - Stockholm, Göteborg och Malmö, och vidare ut i Europa. Därmed ökar sannolikheten att snabbare, längre och tyngre utländska tåg korsar de svenska järnvägslinjerna. Dock kan detta bli problematiskt i och med att järnvägsbroars dynamiska respons och, följaktligen, risken för resonans ökar med ökad tåghastighet. Broar dimensioneras ofta utifrån nuvarande förutsättningar och hänsyn tas sällan till framtida hållbarhetskrav, exempelvis p.g.a. kostnadsbesparingar. Ur ett framtidsperspektiv kan därför det dynamiska beteendet hos befintliga broar komma att bli otillräckligt. Utbyggnaden av höghastighetsnätverket ökar därmed behovet av innovativa konstruktionslösningar för nya broar och kostnadseffektiva uppgraderingsmetoder för befintliga sträckor. Syftet med föreliggande avhandling är att föreslå en metod för att minska de vibrationsnivåer som kan uppstå i både nybyggda och befintliga järnvägsbroar för höghastighetståg. Huvudfokus är en eftermonteringsmetod med viskösa dämpare, som har installerats mellan brons överbyggnad och landfästen, för att minska brobanans vertikala acceleration under gällande europeiska dimensioneringskrav. Vidare avses att undersöka effektiveteten av ett sådant system, samt att identifiera och analysera de parametrar och osäkerheter som kan påverka dess funktionalitet. Fall- och parameterstudier, samt statistiska metoder används och utvärderas för att undersöka tillämpbarheten av den föreslagna vibrationsdämpningsmetoden. Två olika modeller, ett enfrihetsgradssystem och en finit elementmodell, har skapats och jämförts. Utifrån dessa modeller kan påverkan av dämparens parametrar, variabiliteten hos materialegenskaperna och behandlingen av olika modelleringsaspekter studeras. Från resultaten är det tydligt att brobanans accelerationsnivå avsevärt reduceras efter monteringen av viskösa dämpare, till och med under dimensioneringskraven.
QC 20170425
26
Ibrahim, Yasser El-Husseini. "A New Visco-Plastic Device for Seismic Protection of Structures." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/26193.
Full textAbstract:
A new visco-plastic damper for seismic protection is introduced. This device combines and enhances many of the proven characteristics of both displacement-dependent and velocity-dependent devices.
The device consists of a block of a high-damping viscoelastic material sandwiched between two steel shapes (plates or channels) bent in a certain configuration to amplify the deformations in the device in order to obtain large tensile and compressive strains in the viscoelastic material. Under low levels of vibrations, the device dissipates energy through amplified strains in the viscoelastic material only; however, under moderate to strong levels of vibrations, a new source of energy dissipation is added through the yielding of the steel elements. The inelastic behavior of the steel elements is controlled by the rigidity of the viscoelastic material. In addition to the energy dissipation, the device provides stiffness through the steel elements as well as the viscoelastic material. Moreover, one of the main advantages of the device is that its behavior is fully controlled through different parameters.
First, a nonlinear time history analysis was conducted on structures with a preliminary model of the device using SAP2000 program to check the effectiveness of the device on the response of different structures under ground excitations. The device resulted in better improvement in the structural response compared to the existing viscoelastic dampers.
A three-dimensional finite element model was developed for the device using the finite element package, ABAQUS. The hyperelastic and viscoelastic behavior of the block of the viscoelastic material were considered. The inelastic behavior of the steel elements was considered as well using the Von Mises yielding criterion. The device was analyzed under different dynamic loadings with different frequencies.
Three simplified models were developed using SAP2000 program in order to facilitate the modeling of the device for structural engineers. These models were compared to the detailed finite element model to check their accuracy. The best model was used in the analysis of a multi-story steel frame with the visco-plastic devices under different ground excitations. Two different arrangements of the device were considered. The devices caused significant reduction in the story displacements, base shear and bending moment at column bases.Ph. D.
27
Prucz, Jacky C. "Analytical and experimental methodology for evaluating passively damped structural joints." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/11987.
Full text
28
Gong, Zheng Li. "Passive motion control of super tall buildings : tuned mass and viscous dampers in Taipei 101." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51575.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Includes bibliographical references (leaves 50-51).
As tall buildings keep becoming taller, they become more susceptible to dynamic excitations such as wind and seismic excitations. One way to reduce structural vibration under dynamic excitations is by placing damping devices in the buildings. In this thesis, the design concept, design procedure and some current applications of tuned mass and viscous dampers are discussed. Taipei101 was used as an example to compare the performance of the two damping schemes. It was modeled in a two-dimensional scheme in SAP2000 and a TMD was placed on its top to study its effect on the structural response due to wind and seismic excitations and confirm with the actual results. A sensitivity study was then performed to study the effect of varying the mass ratio on the structural response. A second TMD was then placed at the location where the maximum deflection occurs for the second mode to evaluate its effectiveness in reducing structural response. Finally, twelve viscous dampers were placed in the model to study their effects on the structural response. Time-history and steady-state analysis in SAP2000 were used for the wind and seismic analyses.
M.Eng.
29
Kalyanam, Sujatha. "Optimal design of passive fluid viscous dampers for controlling vibrations in seismically-excited truss towers." Tallahassee, Florida : Florida State University, 2009. http://etd.lib.fsu.edu/theses/available/etd-05112009-031200/.
Full textAbstract:
Thesis (M.S.)--Florida State University, 2009.Advisor: Michelle Rambo-Roddenberry, Florida State University, College of Engineering, Dept. of Civil and Environmental Engineering. Title and description from dissertation home page (viewed on Oct. 27, 2009). Document formatted into pages; contains viii, 61 pages. Includes bibliographical references.
30
Allan, Stu. "Passive be damned : the construction that wouldn't be beaten : a thesis submitted in partial fulfilment of the requirements for the Degree of Master of Arts in Linguistics at the University of Canterbury /." Thesis, University of Canterbury. Languages, Cultures and Linguistics, 2009. http://hdl.handle.net/10092/2265.
Full textAbstract:
This thesis brings together two different lines of research, the nature of passive voice, the nature of readability. Commonly, languages have a range of tools for detransitivisation, topicalisation, and impersonalisation, of which passivisation is one (Givón, 1981). Passives have important roles in our language, and prescribing against their use lacks a full understanding of these roles. Much of the concern around passives from writers, editors, and teachers is no more than folklore that has not clearly analysed various writing and reading problems. Many awkward sentences are not awkward because they use passives but because they are wordy, clumsy, or pretentious. Most criticisms have little basis in linguistic theory, and rarely is there more than passing mention of the important role that passives play in communication.
Some uses of passives are inappropriate, being vague, ambiguous, or even deceitful. These inappropriate uses of passive voice give the construction a bad name. They have become ammunition for prescriptive grammarians to fire at all uses of passives, often with weak analysis and minimal reference to linguistic theory. ‘Avoid passives’ has become a mantra.
I tentatively suggest that there is unlikely to be a cost to processing passives. Given the speed at which the brain processes clauses, any differences in readability (if they exist) must be miniscule. Consequently, I suggest that any differences are unimportant relative to the benefits that appropriately used passives bring to readability. Furthermore, appropriately used passives may actually improve readability, especially when there is greater interest in the passive subject than the active subject, and when the passive serves to connect clauses or sentences.
31
Patel, Hardik D. "Use of Permanent Magnets to Improve the Seismic Behavior of Light-Framed Structures." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/42707.
Full textAbstract:
Light-framed wood structures generally have satisfied the life safety objective of
the current seismic design approach. The main source of energy dissipation in such
structures is the inelastic behavior of the connectors connecting framing and sheathing
elements. Wood framed structures when subjected to strong ground excitations experience
structural and non-structural damage which may incur large repair/replacement costs or
may even render the structure out of service. Thus, it is very important to apply
techniques to mitigate the seismic response of the light-framed structures and avoid large
monetary losses.
It is proposed to use commercially available permanent magnets, incorporated in
the form of passive friction dampers, to dissipate a part of input energy induced due to
strong ground motions, thereby reducing the inelastic energy dissipation demand of the
lateral load resisting system. The force of attraction between the permanent magnet and
ferromagnetic material like steel was utilized to produce the required friction resistance. A
sliding wall configuration consisting of flexible permanent magnets and steel plates
sandwiched between the plywood sheets was analyzed for its effectiveness in mitigating
the response of a two story wood shear wall structure. The structural analysis program
SAP2000 was used to perform nonlinear dynamic analysis of the finite element models
generated using the meshing algorithms incorporated into â WoodFrameMeshâ . Nonlinear
link elements available in SAP2000 were used to model the friction between the flexible
magnet sheet and the steel plate. The effects of various modeling parameters on the
solution of the nonlinear analysis were studied so as to arrive at appropriate values to
represent the friction problem. Also the friction damped structure was analyzed to study
its forced and free vibration characteristics. Further, the responses of the friction damped
structure and the undamped structure were compared when subjected to different ground
accelerations. The response of the friction damped structure was also compared to that of
the structure in which the proposed friction dampers were replaced by normal shear walls.
A huge reduction in the response of the friction damped structure was observed when
compared to the response of the undamped structure. The friction damped structure was
also analyzed for different values of modal damping ratios. Over all about 60-80% of the
input energy was dissipated by friction damping in all the cases. The slip resistance of a
flexible permanent magnet sheet was also verified in the laboratory. Above all the
magnetic properties of commercially available permanent magnets and the effects of
strong permanent magnets on human health were also studied.Master of Science
32
Chittur, Krishna Murthy Anantha Narayan. "Application of visco-hyperelastic devices in structural response control." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/32910.
Full textAbstract:
Structural engineering has progressed from design for life safety limit states to performance based engineering, in which energy dissipation systems in structural frameworks assume prime importance. A visco-hyperelastic device is a completely new type of passive energy dissipation system that not only combines the energy dissipation properties of velocity and displacement dependent devices but also provides additional stability to the structure precluding overall collapse.
The device consists of a viscoelastic material placed between two steel rings. The energy dissipation in the device is due to a combination of viscoelastic dissipation from rubber and plastic dissipation due to inelastic behavior of the steel elements. The device performs well under various levels of excitation, providing an excellent means of energy dissipation. The device properties are fully controlled through modifiable parameters.
An initial study was conducted on motorcycle tires to evaluate the hyperelastic behavior and energy dissipation potential of circular rubber elements, which was preceded by preliminary finite element modeling. The rubber tires provided considerable energy dissipation while displaying a nonlinear stiffening behavior. The proposed device was then developed to provide additional stiffness that was found lacking in rubber tires.
Detailed finite element analyses were conducted on the proposed device using the finite element software package ABAQUS, including parametric studies to determine the effect of the various parameters of device performance. This was followed by a nonlinear dynamic response history analysis of a single-story steel frame with and without the device to study the effects of the device in controlling structural response to ground excitations. Static analyses were also done to verify the stabilizing effects of the proposed device. Results from these analyses revealed considerable energy dissipation from the device due to both viscoelastic as well as plastic energy dissipation.
Detailed experimental analyses on the proposed device, finite element analyses of the device on multistory structures have been put forth as the areas of future research. It may also be worthwhile to conduct further research, as suggested, in order to evaluate the use of scrap tires which is potentially a very valuable structural engineering material.Master of Science
33
Delamare, Jérôme. "Suspensions magnétiques partiellement passives." Grenoble INPG, 1994. http://www.theses.fr/1994INPG0004.
Full textAbstract:
Les suspensions magnétiques permettent la lévitation d'un corps sans contact. Un mobile peut ainsi être déplacé à grande vitesse sans engendrer de frottement ni d'usure. Les applications de ces systèmes sont essentiellement circulaires (turbines, volant d'inertie, centrifugeuse, machine outils. . . ) mais peuvent ainsi être linéaires (train. . . ). Les suspensions magnétiques sont déjà utilisées dans l'industrie mais leur prix de revient, dû à l'asservissement de tous les degrés de liberté de la partie suspendue, freine leur expansion. L'étude porte sur les suspensions magnétiques dont une partie des degrés de liberté est contrôlé par des paliers autonomes à aimants permanents. Les associations de paliers permettant de réaliser une suspension sont décrites ainsi que les motorisations possibles et les systèmes d'amortissement. La réalisation d'un prototype a mis en évidence les avantages et les inconvénients d'une suspension ne possédant qu'un seul axe asservi
34
Kruep, Stephanie Jean. "Using Incremental Dynamic Analysis to Visualize the Effects of Viscous Fluid Dampers on Steel Moment Frame Drift." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/34122.
Full textAbstract:
This thesis presents the details of a study regarding both the use of linear viscous fluid dampers in controlling the interstory drift in steel moment frames, and the use of incremental dynamic analysis as a method of visualizing the behavior of these moment frames when subjected to seismic load effects. Models of three story and nine story steel moment frames were designed to meet typical strength requirements for office buildings in Seattle, Washington. These models were intentionally designed to violate seismic interstory drift restrictions to test the ability of the linear viscous fluid dampers to reduce these drifts to the point of code compliance. Dampers were included in one bay of every story in each model. These devices were used to produce total structural damping ratios of 5%, 10%, 20%, and 30% of critical. Undamped, traditional stiffness controlled models of both three stories and nine stories were also created for comparison purposes. Incremental dynamic analysis was used to subject these models to ten ground motions, each scaled to twenty incremental levels. Two new computer applications were written to facilitate this process. The results of these analyses were studied to determine if the linear viscous fluid dampers were able to cause compliance with codified drift limits. Also, incremental dynamic analysis plots were created to examine the effects of the dampers on structural behavior as damping increased from inherent to 30% of critical. It was found that including linear viscous fluid dampers in steel moment frame design can satisfactorily control interstory drift, and incremental dynamic analysis is a beneficial tool in visualizing dynamic structural behavior.Master of Science
35
Tomlinson, Charles M. "Design and construction of a three degree-of-freedom lightweigh passively-damped robot arm." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/17094.
Full text
36
Vincent, Rémy. "Identification passive en acoustique : estimateurs et applications au SHM." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT020/document.
Full textAbstract:
L’identité de Ward est une relation qui permet d’identifier unmilieu de propagation linéaire dissipatif, c'est-à-dire d'estimer des paramètres qui le caractérisent. Dans les travaux exposés, cette identité est utilisée pour proposer de nouveaux modèles d’observation caractérisant un contexte d’estimation qualifié de passif : les sources qui excitent le système ne sont pas contrôlées par l’utilisateur. La théorie de l’estimation/détection dans ce contexte est étudiée et des analyses de performances sont menées sur divers estimateurs. La portée applicative des méthodes proposées concerne le domaine du Structural Health Monitoring (SHM), c’est-à-dire le suivi de l’état de santé desbâtiment, des ponts... L'approche est développée pour la modalité acoustique aux fréquences audibles, cette dernière s'avérant complémentaire des techniques de l’état de l’art du SHM et permettant entre autre, d’accéder à des paramètres structuraux et géométriques. Divers scénarios sont illustrés par la mise en oeuvre expérimentale des algorithmes développés et adaptés à des contraintes de calculs embarqués sur un réseau de capteurs autonomeWard identity is a relationship that enables damped linear system identification, ie the estimation its caracteristic properties. This identity is used to provide new observation models that are available in an estimation context where sources are uncontrolled by the user. An estimation and detection theory is derived from these models and various performances studies areconducted for several estimators. The reach of the proposed methods is extended to Structural Health Monitoring (SHM), that aims at measuring and tracking the health of buildings, such as a bridge or a sky-scraper for instance. The acoustic modality is chosen as it provides complementary parameters estimation to the state of the art in SHM, such as structural and geometrical parameters recovery. Some scenarios are experimentally illustrated by using the developed algorithms, adapted to fit the constrains set by embedded computation on anautonomous sensor network
37
Kabiri, Far Bardia. "Application of the Equivalent Static Analysis method to the design of a steel frame structure with added viscous dampers." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10647/.
Full textAbstract:
All the structures designed by engineers are vulnerable to natural disasters including floods and earthquakes. The energy released during strong ground motions should be dissipated by structural elements. Before 1990’s, this energy was expected to be dissipated through the beams and columns which at the same time were a part of gravity-load-resisting system. However, the main disadvantage of this idea was that gravity-resisting-frame was not repairable.
Hence, during 1990’s, the idea of designing passive energy dissipation systems, including dampers, emerged. At the beginning, main problem was lack of guidelines for passive energy dissipation systems. Although till 2000 many guidelines and procedures where published, yet most of them were based on complicated analysis which was not so convenient for engineers and practitioners.
In order to solve this problem recently some alternative design methods are proposed including 1. Lopez Garcia (2001) simple procedure for optimal damper configuration in MDOF structures 2. Christopoulos and Filiatrault (2006) trial and error procedure 3. Silvestri et al. (2010) Five-Step Method. 4. Palermo et al. (2015) Direct Five-Step Method. 5. Palermo et al. (2016) Simplified Equivalent Static Analysis (ESA). In this study, effectiveness and differences between last three alternative methods have been evaluated.
38
Feitosa, Luiz Claudio Sales. "Controle por impacto de vibrações estruturais excitadas por carregamentos não-ideais." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-27032006-213252/.
Full textAbstract:
Apresentam-se modelos matemáticos de poucos graus de liberdade para o estudo de vibrações estruturais não lineares excitadas por fonte não-ideal de energia, amortecidas por impacto, para duas aplicações: um pórtico que serve de apoio para um motor elétrico e uma torre de suporte a uma turbina eólica. Considera-se a existência de interação entre o fornecimento de energia e o movimento da estrutura de suporte. Se a potência fornecida pela fonte de energia não é suficiente, a rotação do rotor pode ficar estagnada à freqüência de ressonância da estrutura, impossibilitando o mesmo de alcançar regimes de rotação mais altos. Isso é uma manifestação do chamado Efeito Sommerfeld. No primeiro modelo, somente dois graus de liberdade são considerados: o movimento horizontal da estrutura, na direção perpendicular ao eixo do rotor, e a rotação do rotor. Depois, adiciona-se outro grau de liberdade, representando o movimento de uma pequena massa que se desloca livremente dentro de uma câmara (amortecedor por impacto). As equações de movimento desses modelos são obtidas via formulação Lagrangiana. Por intermédio de simulações numéricas, procurou-se estudar os parâmetros do amortecedor por impacto que produzem a melhor eficiência do dispositivo. Nota-se que o impacto da massa com as paredes do recipiente fornece controle da amplitude de vibração da estrutura e da largura da banda de freqüências em que o Efeito Sommerfeld ocorre.We present mathematical models with few degrees of freedom for the study of nonlinear structural vibrations excited by a non ideal energy source, with impact damping, for two applications: a portal frame that supports an electric motor and a tower structure supporting an aeolian turbine. We consider that there is interaction between the energy supply and the motion of the supporting structure. If the power supplied by the energy source is not enough, the rotation of the engine may get stuck at a resonance frequency of the structure, disabling the engine to reach higher regimes of rotation. This is a manifestation of the so-called Sommerfeld Effect. In the first model, only two degrees of freedom are considered: the horizontal motion of the structure, in the transverse direction to the axis of the rotor, and the rotation of the rotor. Next, another degree of freedom is added to the model, representing the motion of a rolling small mass, free to bounce back and forth inside a chamber (impact damper). The equations of motion of these models are obtained via a Lagrangian approach. The parameters that produce the greatest effectiveness of the impact damper were studied through numerical simulations. One notices that the impact of the mass with the walls of the container supplies control of the vibration amplitude of the structure and the width of the band of frequencies where the Sommerfeld Effect occurs.
39
Michael, Robert Joseph. "DESIGN AND DEVELOPMENT OF A SEISMIC ISOLATIONSYSTEM FOR COMMERCIAL STORAGE RACKS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1370342677.
Full text
40
Cridland, Jennifer. "Late prehistoric Indian subsistence in northeastern Newfoundland : faunal analysis of Little Passage Complex assemblages from the Beaches and Inspector Island sites /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ34174.pdf.
Full text
41
Simon, Madrenas Enric. "Predicción de la fatiga de disipadores de energía elastoplásticos para estructuras sismorresistentes." Doctoral thesis, Universitat de Girona, 2021. http://hdl.handle.net/10803/673931.
Full textAbstract:
Elastoplastic energy dissipators are used in earthquake-resistant design in order to dissipate a substantial part of the seismic energy acting on a building. They are elements that are not part of the load-bearing structure and, therefore, are easily replaceable in case of damage. Their behaviour is usually stable and their degree of degradation difficult to appreciate visually. To assess their degree of degradation, damage indices are used which estimate their remaining dissipative capacity through the combination of a number of variables such as, for example, the number of cycles sustained and their amplitude, the energy dissipated, accumulated deformation and maximum deformation.
In the first part of this doctoral thesis, the current state-of-the-art in terms of existing damage models is reviewed.
The second part of this thesis brings together a wide experimental foundation based on data obtained in previous research works complemented with new tests carried out within the present thesis. In its third part, the validity of various fatigue models is assessed through the experimental foundation brought together in the second part of this thesis.
In its fourth and final part, the validity of some of the best-known hysteretic models has been analyzed in order to reproduce the experimental response of the dissipators tested.
Notable as the most important contribution of this thesis is the attainment of two models of mixed fatigue and dimensionless variables, which demonstrate excellent validity considering, in the same fatigue curve, dissipators of different types and geometry based on low carbon steel and uniform plastification in uniaxial states of stressEls dissipadors d’energia elastoplàstics s’utilitzen en el disseny sísmic per dissipar una part substancial de l’energia sísmica introduïda en una construcció. Són uns elements que no formen part de l’estructura portant i, per tant, fàcilment reemplaçables en cas de quedar danyats. El seu comportament sol ser estable i el seu grau de degradació difícilment apreciable de forma visual. Per avaluar el seu grau de degradació es recorre als índex de dany, que estimen la capacitat dissipativa romanent a partir de la combinació de variables diverses com són, per exemple, el nombre de cicles suportats i la seva amplitud, l’energia dissipada, la deformació acumulada i deformació màxima. A la primera part d’aquesta tesi doctoral es revisa l’estat de l’art relatiu a models de dany existents. La segona part d’aquesta tesi recull una àmplia base experimental basada en dades obtingudes en treballs previs de recerca, complementats amb nous assajos realitzats a la present tesi. En una tercera part es valora la bondat de diversos models de fatiga mitjançant la base experimental recollida a la segona part. En la seva quarta i última part s’ha analitzat la bondat d’alguns dels models histerètics més coneguts per a reproduir la resposta experimental dels dissipadors assajats. La conclusió més important que s’extreu de la tesi és l’obtenció de dos models de fatiga mixtes i variables adimensionals, els quals demostren una excel·lent bondat considerant, en una mateixa corba de fatiga, dissipadors de diferent tipologia i geometria, basats en acers de baix contingut en carboni i plastificació uniforme en estat uniaxial de tensions
Programa de Doctorat en Tecnologia
42
Guillemette, Gaétane. "Un tournant à risque--Le difficile passage de la décomposition à la recomposition de la congrégation des soeurs de Notre-Dame du Perpétuel Secours." Thesis, Université Laval, 2003. http://www.theses.ulaval.ca/2003/20835/20835.pdf.
Full textAbstract:
Quel avenir pour les congrégations religieuses au Québec ? Cette interrogation nous introduit à la problématique de l'évolution sociohistorique des communautés religieuses féminines au Québec particulièrement depuis les années 1960 avec la Révolution tranquille et l'aggiornamento de Vatican II. Une transition majeure s'opère à l'intérieur d'un processus de décomposition et de recomposition d'un ensemble social qui se voit affecté dans sa morphologie, sa structure, sa culture et sa dynamique psychosociale.
L'étude d'un cas type permet l'analyse des processus de décomposition et de recomposition de ces groupes, à partir du concept du cycle de vie d'une organisation arrivée au point de crise où le tournant aboutit à un changement de paradigme ou à l'extinction du groupe. Cette dynamique de transition s'avère par ailleurs un lieu de confusion et de déstabilisation propice à la création de nouvelles conditions d'existence, à la refondation d'un institut et au renouvellement de la vie religieuse dans son ensemble.What future for the religious congregations in Quebec ? Such a question invites us to look into the socio-historical evolution of religious women communities in Quebec, since the 60's, along with the « Révolution tranquille » and the Vatican II aggiornamento. A major transition occurs inside a decomposition recomposition process of a whole society entity affected in its morphology, structure, culture and psychosociological dynamism. A case study allows the analysis of the decomposition recomposition process of those groups based on the organizational life cycle concept of one arrived at a critical point where the issue is a paradigmatic change or the group extinction. This transition dynamics gives rise to a confused and destabilized situation from which could emerge the creation of a new life style, the institute refounding and the whole religious life renewal.
Inscrite au Tableau d'honneur de la Faculté des études supérieures
43
Yan, Linjuan. "Contrôle de vibrations large bande à l’aide d’éléments piézoélectriques utilisant une technique non-linéaire." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0107/document.
Full textAbstract:
Afin de limiter les contraintes dans les matériaux pour accroître leur durée de vie et améliorer la sécurité des structures (par exemple dans les transports), ainsi que d’améliorer le confort des utilisateurs, le contrôle de vibrations mécaniques et leur amortissement a fait l’objet de nombreuses recherche scientifiques depuis de nombreuses décennies. De plus, la prolifération récente des matériaux dits « intelligents » couplant plusieurs disciplines de la physique telles que la mécanique et l’électricité a permis l’élaboration de techniques de contrôle de vibration fiables, robustes et performantes tout en étant très intégrables, permettant ainsi de disposer de méthodes totalement adaptées aux système embarqués ou aux structures où les contraintes d’encombrement sont relativement restrictives. Notamment, il a récemment été proposé l’utilisation de techniques non linéaires basées sur une commutation synchronisée d’éléments piézoélectriques sur une impédance afin d’amélioration la conversion d’énergie mécanique sous forme électrique et ainsi de disposer de systèmes de contrôle de vibrations très performants et intégrables. Néanmoins, du fait du principe de cette commutation synchronisée avec la déformation, le contrôle de vibrations large bande, très présents dans les environnements réels, conduit à une dégradation des performances de ces techniques. L’objectif des travaux rapportés dans cette thèse consiste à proposer et à étudier théoriquement et expérimentalement des approches dérivées de ces techniques mais totalement adaptées au large bande. Ainsi, après une introduction relatant l’état de l’art en termes de contrôle vibratoire, la première technique exposée dans cette thèse propose d’utiliser un filtrage spatial permettant de séparer les modes de vibrations pour ensuite connecter de manière appropriée des éléments piézoélectriques afin de pouvoir simultanément contrôler plusieurs modes de vibrations en flexion. La deuxième méthode pour disposer de systèmes de contrôle de vibrations efficaces se base sur la combinaison d’amortisseurs à masse accordée avec l’approche non-linéaire afin d’améliorer le pouvoir d’amortissement par un contrôle supplémentaire des transferts énergétiques via le couplage électromécanique, conduisant à une méthode efficace, robuste et pouvant être installée facilement. La troisième et dernière approche consiste à utiliser les propriétés remarquables des structures périodiques en les couplant avec l’approche non-linéaire, cette dernière permettant une augmentation de l’amortissement et un élargissement significatif des bandes fréquentielles réduisant significativement l’amplitude de l’onde. Enfin, une conclusion générale exposera les principaux résultats obtenus et proposera des pistes d’évolution des concepts exposésIn order to protect structures, extend their lifespan and decrease the incomfort resulting from undesired vibrations, many works have been reported for reducing vibrations. Along with the development of smart materials such as piezoelectric materials which are extensively used for vibration control and noise reduction due to their unique features (high integrability, compactness, light weight and high bandwidth), control systems can be designed in a more compact and simple form. Additionally, due to the conversion between mechanical energy and electrical energy, vibrations can be effectively attenuated by electromechanical approaches. Synchronized Switch Damping on Inductor (SSDI) technique attracted lot of attentions as an effective semi-passive technique which can artificially increase the converted energy by nonlinear voltage inversion process, thus allowing superior control performance compared to passive technique with low power requirement and simple control algorithm. Based on this semi-passive control technique, the objectives of this work are threefold. The first aim is improving the multimodal/broadband control performance of SSDI. An enhanced strategy based on spatial filtering according to the mode shapes of the vibrating structure is proposed. In order to separate the uninterested modes and effectively damp the targeted modes, sum and different switches respectively based on the sum of the piezovoltages of two anti-symmetrically bonded patches and the voltage difference of the two symmetrically bonded piezoelectric elements are introduced. Since the vibration modes can be spatially filtered by these connections, multimodal vibrations can be damped significantly and simultaneously as the sum and difference switches are employed, with an increase of total inversion coefficient. Then, electromechanical TMD (tuned mass damper) featuring piezoelectric materials combined with the semi-passive nonlinear technique SSDI is presented. Using this electromechanical semi-passive nonlinear TMD, the mechanical energy is not only transferred between host structure and TMD device but also converted as electrical energy stored in the piezoelectric patches and/or dissipated in the connected circuit, which allows excellent damping performance for limiting the vibrations. The last investigated method consists in electromechanical periodic structures featuring the nonlinear switching interface. Such a structure can effectively attenuate the elastic waves and damp the vibration in a wider frequency band since it has the capability of filtering propagative waves within stop bands attributed to the structural periodicity and the superior damping ability which is attributed to the nonlinear voltage inversion process that increases the voltage amplitude and decreases the phase between voltage and speed. Finally, a conclusion proposes a summary of the main results obtained in this thesis, as well as new extensions and ways of the proposed techniques
44
Nuh, Ilsiona. "Le texte dans le codex : émergence poétique et images sociales (Marie dans le théâtre du Moyen Âge)." Thesis, Université Clermont Auvergne (2017-2020), 2020. http://www.theses.fr/2020CLFAL012.
Full textAbstract:
Dans notre corpus d’étude : La Présentation de Marie au Temple, Les Miracles de Nostre Dame par personnages et Le Mystère de la Passion d’Arnoul Gréban, le personnage de Marie se présente à l’intersection des langues, des genres et des lieux où se réinvente le théâtre. Ces aspects hétérogènes se dissolvent dans la mesure où le personnage de Marie s’ancre dans la logique de la foi chrétienne : au sein de la Vierge fut incarnée la Parole de Dieu qui, sous sa forme humaine, en la personne du Fils, parla aux hommes ; telle est l’affirmation fondamentale du christianisme qui souligne l’importance du Verbe. Néanmoins, les écrits néotestamentaires qui rapportent la parole divine sont discrets sur Marie, tandis que les jeux à sujet religieux donnent à voir et à entendre un personnage caractérisé par un langage théâtral. En écho avec les écrits scripturaires, le personnage de Notre Dame est composé à partir des écrits pieux en latin et en langue vernaculaire, des textes littéraires et rhétoriques, et sous l’influence des réalités sociales. Son personnage est en effet à la confluence de ces courants qu’il transcende et, à leur interstice, il modèle une nouvelle façon d’exprimer la foi à laquelle la forme dramatique donne une dimension collective. Appuyée sur l’analyse matérielle et poétique des manuscrits, cette thèse s’attache à montrer les dynamiques qui donnent vie au personnage de Marie et ses répercussions sur la composition du texte dramatique, ainsi que sur les communautés qu’il engendreThe dramatis personae of Mary in La Présentation de Marie au Temple, Les Miracles de Nostre Dame par personnages and Le Mystère de la Passion d’Arnoul Gréban is at the intersection of languages, poetical genres, and places where drama is performed. Her character is inspired by the Christian faith in the Incarnation: within the Virgin was incarnated the Word of God who, in his human form, in the person of the Son, spoke to men. The fundamental affirmation of Christianity underlines the importance of the Word. Nevertheless, the New Testament is discreet about Mary, while the religious plays show the mother of Lord characterized by a self-expression, a mainly lyrical one. Inspired by texts in Latin and in vernacular, from literary and rhetorical texts, and under the influence of social realities, the character of Mary is at the confluence of these currents that she transcends and, at their interstice, models a new way of expressing faith, to which the dramatic form gives a collective dimension. Based on the material and poetical analysis of the manuscripts, this thesis aims to show the dynamics that give life to Mary in theatre and the repercussions of her character on the poetry of the dramatic text, as well as on the communities it engenders
45
Carlisle, Meaghan. "Experimental investigations into a passive auto-tuning mass damper." Thesis, 2014.
Find full textAbstract:
A passive auto-tuning mass damper (PATMD) is a vibration control device that consists of a mass which is suspended in the top region of a structure and is forced into motion, due to inertia, when the structure is excited. A steel test structure is used to carry out the experimental investigation. The PATMD is connected to the structure to be controlled by a group of inelastic ropes and is free to move in any translational direction. It moves relative to the structure, utilising and dissipating large amounts of energy as it swings from side to side, and in this way, the vibrational energy of the structure is absorbed and consequently the vibrations of the structure are controlled.
First, the ‘PATMD efficiency tests’ are carried out, whereby the test model is subjected to translational, torsional and coupled free vibration tests, initially without the PATMD and then with the PATMD, in order to determine the damping effects of the PATMD. The test model is then subjected to forced harmonic vibration tests similar to those described above and the damping effects are again analysed. These tests aim to demonstrate the PATMD’s effectiveness in controlling the translational vibration in two directions, torsional vibration and coupled vibration, under both free and forced excitation, without being tuned.
Secondly, a parameter study is carried out whereby the dynamic properties of the primary test model are varied whilst the PATMD is left unchanged. The free and forced vibration tests are repeated. Finally, the properties of the PATMD are varied whilst the primary model remains unaltered. Again, the tests described above are repeated, without any tuning of the system taking place.
The results of the ‘PATMD efficiency tests’ demonstrate its capability of providing significant control to translational, torsional and coupled vibrations of the structure without being tuned in any way. Furthermore, the parameter study demonstrates the PATMD’s effectiveness under very different conditions of the system, without having undergone any tuning or specific adjustment. The tests reveal that the PATMD is robust, uncomplicated and versatile making it an ideal application for engineering structures.
46
Wang, Chiu-Wen, and 王秋文. "Seismic Behavior of Structures with Passive Tuned Mass Damper." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/41079979533761226129.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
95
This thesis reviews the passive tuned mass damper design methods and seismic performance under structures yield. The results of shaking table test which is a 3 story steel frame equipped bilinear-elastic tuned mass damper are proposed. The EL Centro and TCU129 excitations are used for the test. Summarizing the results of a parametric study performed to understand some important characteristics of passive tuned mass damper. The effect of structures equipped three different passive tuned mass damper while prime structures before and after yield. The contribution of the equivalent damping ratio which is from the linear optimal passive tuned mass damper for a SDOF structure before and after prime structure yield. Using the substitute structure approach, the evaluation of seismic performance of structures with passive tuned mass damper is proposed, and the results are verified by dynamic inelastic time history analyses.
47
Tai, Chun-yang, and 戴君仰. "Active and Passive Vibration Control Using Electromagnetic Damper Systems." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/67137328152275058299.
Full textAbstract:
碩士國立臺灣大學
應用力學研究所
96
In accordance with electromagnetic theory, when a conductive wire moves in a uniform magnetic field. It will generate an inductive current. And the charges of this induced current under the action of applied magnetic field experience a Lorentz force, and pass this Lorentz force whose direction is opposite to the moving direction of the wire, to the wire. According to this counteracting phenomenon, we make an electromagnetic damper and apply it to vibration control of cantilever beam. In this thesis, we first establish equations of vibration and simulate numerical active and passive. Next, we perform experimental test of passive vibration control and study the effect of system parameters on the alleviating the vibration amplitude. This agrees will with simulation results. In the active vibration control experiment, we add an electric circuit which can amplifier Lorentz force and therefore improve the control result. Finally, we also perform the experimental test of noise control and find that the result of amplitude reducing is very good.
48
Wang, Jer-Fu, and 王哲夫. "Optimal Design and Application of Passive Tuned Mass Damper." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/99817522214522572493.
Full text
49
Yang, Jiain Ban, and 楊健邦. "Parametric Analysis of Passive Tuned Mass Damper for Torsionally-Coupled Buildings." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/52640869859197944813.
Full text
50
Liu, Chien Hung, and 劉建宏. "Optimal Design of Passive Tuned Damper for Buildings under Wind Excitation." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/34156106216294810668.
Full textAbstract:
碩士國立中興大學
土木工程學系
89
Wind-induced vibration affects structural safety and comfort of occupants greatly. Passive Tuned Mass Dampers (PTMD) as an energy dissipating device can be used to increase the overall damping of the main structure and accordingly to reduce the wind-induced building vibration. In this study, PTMD is utilized to reduce aerodynamic response of structures. In the past, simplified formulas for determining the optimal parameters are proposed so that the design of a PTMD can be carried out easily. With the considerations of the power spectral density function of wind force, the optimal PTMD’s system parameters are determined by minimizing the mean-square acceleration response ratio of the controlled degree-of-freedom between the building with and without PTMD. Lead into wind excitation, optimal design of wind-induced vibration control of frame structures is investigated. The calculated results show that the difference between the optimal design and simplified formulas design is not significant. Furthermore, PTMD still has high efficiency in reducing vibration when structure and wind excitation are in resonance. For a given PTMD’s mass ratio, it is found that the PTMD’s optimal parameters change slightly for structures with different period.