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 adopté / The 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

The master thesis deals with computational modeling of a turbocharger vibrations and and assessment of influnce of passive dynamic vibration absorber on vibrations of actuator bracket. The use of dynamic vibration absorber was summarized in the research study. The analysis were performed using finite element method in ANSYS. Several computational models of turbocharger were created with different ways of modeling bolted joints between turbocharger parts. Modal analysis of each model was performed and the results were compared. For the selected model, the response to the kinematic excitation from the internal combustion engine for two load conditions was calculated using harmonic analysis. A simple model of vibration dynamic absorber was applied to the turbocharger model with reduced degrees of freedom and its influnce on vibrations of actuator bracket was investigated. Significant decrease of the maximum acceleration amplitude was achieved in a given frequency range when absorber parameters were optimized.

No description available.

Over the past decade, offshore wind has positioned itself as one of the most promising renewable energy markets. While this field is currently dominated by fixed-bottom wind turbines located within a limited depth range, floating turbines are showing promise as a way to capture the more developed wind profiles available in deeper waters. Currently, the main challenge with floating offshore wind is that the systems experience larger ultimate loads compared to fixed bottom turbines. These larger loads are caused by the increased motion inherent with floating structures. This study looks to analyze the effects that traditional and inerter based structural control methods can have on vibration reduction of floating offshore wind turbines. Models are developed adding tuned mass dampers (TMD) and tuned inerter dampers (TID) into the three main columns of a semisubmersible platform. Results showed that for free decay tests, heave and pitch root mean square (RMS) values were reduced significantly by the addition of passive structural control. The inerter based structural control consistently outperformed traditional TMD and also allowed for similar performance with significantly reduced physical mass values. For regular wave excitation both control methods resulted in significant reductions to the heave and pitch RMS values compared to the baseline, with the TID outperforming the TMD . And for an irregular wave analysis, it was found that both control configurations were still able to provide meaningful reductions to the baseline model. / Master of Science / Over the past decade, offshore wind has positioned itself as one of the most promising renewable energy markets. While this field is currently dominated by fixed-bottom wind turbines located within a limited depth range, floating turbines are showing promise as a way to capture the more developed wind profiles available in deeper waters. Currently, the main challenge with floating offshore wind is that the systems experience larger ultimate loads compared to fixed bottom turbines. These larger loads are caused by the increased motion inherent with floating structures. This study looks to analyze the effects that traditional and enhanced motion reduction technology can have on floating offshore wind turbines. Models are developed adding the traditional and enhanced motion reduction technology into the three main columns of a semisubmersible platform. Results showed that for several different tests, the motion reduction technology has a positive effect on the turbines. For test dropping the system from a set height, the motion reduction technology allowed the system to come to rest much faster. Moreover, the enhanced technology performed better than the traditional technology. The same results were found when the system was excited by simulated waves.

No description available.

The transition from internal combustion engine to battery electric cars is accompanied by a shift on the NVH issues damaging the passenger comfort. The rolling noise generated by the wheels and tyres is in particular characterized by an increasing attention from OEMs and car manufacturers. Among the causes of the rolling noise are the vibrations generated at the wheel, which are transmitted to the vehicle interior through its structure. To limit these vibrations at their source, a new innovative concept has been proposed at Stellantis. This idea is based on the use of a specific type of vibration absorber known by the acronym MTMD (Multiple Tuned Mass Damper).First, the existing literature about vibrations absorbers and optimisation techniques has been reviewed. Then, initial simulations on a global model comprising the wheel and beam-like resonators have shown how this system can effectively reduce a resonant peak.Optimisation processes have then revealed an important attenuation of a wheel resonance, even when the peak frequency is shifted. This demonstrated how important the distribution of resonators resonance frequencies are and their damping ratios when designing a robust and efficient MTMD.Finally, local resonators have been designed and modelled by considering the constraints for an integration on a wheel. A satisfactory design for resonators able to vibrate at the wanted frequency has been found. The beam-like resonators used in the first global model have then been replaced by these real resonators, confirming the possible gain with this device in a vehicle. / Övergången från förbränningsmotorer till batterielektriska bilar åtföljs av en övergång till NVH-frågor som kan påverka passagerarnas komfort. Det rullningsljud som genereras av hjul och däck får i synnerhet ökad uppmärksamhet från OEM:er och biltillverkare.Bland orsakerna till rullningsljudet finns de vibrationer som genereras vid hjulet och som överförs till fordonets inre genom dess struktur. För att begränsa dessa vibrationer vid källan har ett nytt innovativt koncept föreslagits av Stellantis. Idén bygger på användningen av en särskild typ av vibrationsdämpare som kallas MTMD (Multiple Tuned Mass Damper).Först har den befintliga litteraturen om vibrationsdämpare och optimeringstekniker gåtts igenom. Därefter har inledande simuleringar på en global modell som omfattar hjulet och balkliknande resonatorer visat hur detta system effektivt kan minska en resonanstopp.Optimeringsprocesserna har sedan bekräftat att hjulresonansen är kraftigt dämpad, även när toppfrekvensen är förskjuten. Detta visade hur viktig fördelningen av resonansfrekvenser och dämpningsförhållanden för resonatorer är när man utformar en robust och effektiv MTMD.Slutligen har lokala resonatorer utformats och modellerats genom att beakta begränsningarna för en integrering i ett hjul. En tillfredsställande utformning av resonatorer som kan vibrera vid den önskade frekvensen har hittats. De balkliknande resonatorer som användes i den första globala modellen har sedan ersatts av dessa riktiga resonatorer, vilket bekräftar den potentiella förbättringen med denna anordning i ett fordon.

Liquid sloshing in a 2D tank applied on a wave energy capture system and reducing the oscillation of an offshore platform are discussed in this study. A fully nonlinear time-independent finite difference method and the forth-order Runge-Kutta method are implemented to solve the coupled motions of liquid sloshing in a 2D tank with a floating platform. When the external forcing frequency of the Dynamic Vibration Absorber System composed by a tuned liquid damper and a tuned mass damper is identical to the fundamental frequency of the tank, the external force can be effectively diminished by the sloshing-induced force. In the meantime, the maximum effect of tuned mass damper on reducing the amplitude of the floating platform appears. When the frequency of external forcing is close to the first natural frequency of the liquid tank, the coupled effect between the motions of both the tank and the platform can effectively reduce the vibration of the platform and the total energy of the whole system. The Eigenfrequency of a wave capture system is formed by the coupled effect of a liquid tank and a wave capture system. When the excitation frequency of the wave capture system is near its Eigenfrequency, the sloshing-induced force is much larger than that of external and the maximum displacement of the wave energy capture system occurs. As a result, the wave energy capacity of the wave capture system can be averagely increased to 150% by the influence of liquid sloshing in the tank.

Offshore wind turbines have the potential to be an important part of the United States' energy production profile in the coming years. In order to accomplish this wind integration, offshore wind turbines need to be made more reliable and cost efficient to be competitive with other sources of energy. To capitalize on high speed and high quality winds over deep water, floating platforms for offshore wind turbines have been developed, but they suffer from greatly increased loading. One method to reduce loads in offshore wind turbines is the application of structural control techniques usually used in skyscrapers and bridges. Tuned mass dampers are one structural control system that have been used to reduce loads in simulations of offshore wind turbines. This thesis adds to the state of the art of offshore wind energy by developing a set of optimum passive tuned mass dampers for four offshore wind turbine platforms and by quantifying the effects of actuator dynamics on an active tuned mass damper design. The set of optimum tuned mass dampers are developed by creating a limited degree-of-freedom model for each of the four offshore wind platforms. These models are then integrated into an optimization function utilizing a genetic algorithm to find a globally optimum design for the tuned mass damper. The tuned mass damper parameters determined by the optimization are integrated into a series of wind turbine design code simulations using FAST. From these simulations, tower fatigue damage reductions of between 5 and 20% are achieved for the various TMD configurations. A previous study developed a set of active tuned mass damper controllers for an offshore wind turbine mounted on a barge. The design of the controller used an ideal actuator in which the commanded force equaled the applied force with no time lag. This thesis develops an actuator model and conducts a frequency analysis on a limited degree-of-freedom model of the barge including this actuator model. Simulations of the barge with the active controller and the actuator model are conducted with FAST, and the results are compared with the ideal actuator case. The realistic actuator model causes the active mass damper power requirements to increase drastically, by as much as 1000%, which confirms the importance of considering an actuator model in controller design.

Platinautvinning är antagligen en av the farligaste gruvindustrierna. På följd av det har gruvmaskiner som Slotborer utvecklats för att göra utvinningsprocessen säkrare. Slotborern är ett ganska nytt koncept och har problem med vibrationer i borrsträngen när den blir längre.Den här rapporten föreslår fyra koncept för att dämpa/stabilisera dessa vibrationer och ett av dessa koncept var sedan vidare utvecklat efter en evaluering. Det koncept som vidareutvecklats använder sig av massdämpare för att dämpa/stabilisera borrsträngen. Massdämparna är justerbara vilket gör dem effektiva över ett större frekvensområde. Några mätvärden från riktiga borrningar var analyserade och analytiska och matematiska modeller var utvecklade att ha ett liknande beteende som det från mätningarna. Modellerna var sedan utvidgade och massdämparna var implementerade in i modellerna för att analysera deras effekt på systemet. När de analytiska modellerna för massdämparna vara klara nog, började konstruktions- och dimensioneringsarbetet av projektet. Dämparen/stabilisatorn var från början konstruerad för att direkt dämpa vibrationer på 2 – 5 Hz, men på grund av väldigt höga spänningar i massdämparna var frekvensspannet ändrat till 3,5 – 6-7 Hz. Ingen verifiering genom empiriska studier var gjorda men några bra analytiska resultat åstadkoms. / Platinum excavation is probably one of the most dangerous mining businesses. Because of that machines like the Slotborer has been developed to make the excavation process much safer. The Slotborer is a pretty new concept and has problems with oscillations in the drill string when it gets extended.This paper suggests four concepts for dampening/stabilizing these oscillations and one of these concepts was then further developed after an evaluation. The further developed concept uses mass dampers to dampen/stabilize the drill string. The mass dampers are adjustable making them effective for a wider range of frequencies. Some measurements from actual drilling operations was analyzed and analytical and mathematical models were developed to have a similar behavior of that from the measurements. The models was then extended and the mass dampers was applied into the models to analyze their impact of the system. When the analytical models for the mass dampers where done enough, the construction and dimensioning of the project took place. The damper/stabilizer was initially design to directly dampen oscillations between 2 – 5 Hz, but due to very high stresses in the mass dampers the dampening frequency span was changed to 3,5 – 6,7 Hz. No verification through empirical studies was made but some good analytical results of damping was achieved.

Atualmente as estruturas estão sendo avaliadas para um maior número de ações em relação há algumas décadas. Esta melhoria ao longo da fase de concepção é dada devido ao fato de que está se tornando mais competitivo o fornecimento de estruturas leves e esbeltas, sendo solicitados, cada vez mais, projetos com menor custo de implantação. Devido a isto, é necessário avaliar as estruturas não apenas sujeitas a cargas estáticas, mas também a carregamentos dinâmicos. As ações dinâmicas que atuam sobre uma estrutura podem ser muito mais prejudiciais do que as estáticas quando não são bem consideradas e dimensionadas. Ações dinâmicas podem ser provenientes de tremores de terra, vento, equipamentos em funcionamento, deslocamento de pessoas, veículos em movimento, motores desbalanceados, entre outras fontes, o que pode causar vibrações na estrutura, podendo levar a mesma ao colapso. A fim de controlar e reduzir as amplitudes de vibração, entre outras alternativas é possível a instalação de amortecedores de massa sintonizado (AMS), que é um dispositivo de controle passivo. O AMS tem várias vantagens, tais como a grande capacidade de reduzir a amplitude de vibração, fácil instalação, baixa manutenção, baixo custo, entre outras. Para se obter a melhor relação custo-benefício, ou seja, a maior redução de amplitude aliada a um menor número de amortecedores ou a uma menor massa, a otimização dos parâmetros do AMS tornase fundamental. Neste contexto, este trabalho visa, através de simulação numérica, propor um método para otimizar parâmetros de AMSs quando estes devem ser instalados em edifícios submetidos à excitação sísmica. Inicialmente é considerado apenas um único AMS instalado no topo do edifício e em seguida também são feitas simulações com múltiplos AMSs (MAMS), e por fim são descartados os AMSs desnecessários, obtendo assim a melhor resposta da estrutura. Para tanto, uma rotina computacional é desenvolvida em MatLab usando o método de integração direta das equações de movimento de Newmark para determinar a resposta dinâmica da estrutura. Para fins de análise podem ser considerados tanto sismos reais quanto artificiais. Os acelerogramas artificias são gerados a partir do espectro proposto por Kanai e Tajimi. Primeiramente, a estrutura é analisada somente com o seu amortecimento próprio para fins comparativos e de referência. Em seguida, a otimização do ou dos AMSs é feita, na qual a função objetivo é minimizar o deslocamento máximo no topo do edifício, e as variáveis de projeto, são a relação de massas (AMS - Estrutura), rigidez e amortecimento do ou dos AMSs. Para a otimização são utilizados os algoritmos Firefly Algotithm e Backtracking Search Optimization Algorithm. De acordo com as configurações do AMS, após a otimização dos seus parâmetros são determinadas as novas respostas dinâmicas da estrutura. Finalmente, pode-se observar que o método proposto foi capaz de otimizar os parâmetros do ou dos AMSs, reduzindo consideravelmente as respostas da estrutura após a instalação do mesmo, minimizando o risco de dano e colapso do edifício. Desta forma, este trabalho mostra que é possível projetar AMS e MAMS de forma econômica e eficaz. / Currently, structures are being evaluated for a greater number of actions when compared to a few decades ago. This improvement in designing stage is happening because projects providing lightweight and slender structures, with lower implantation costs, are being more requested. Thus, evaluating structures not only subjected to static loads, but also to dynamic loads has become necessary. Dynamic loads acting on a structure are more damaging than static loads, if they are not well considered and dimensioned. Dynamic loads could occur from earthquakes, wind, equipment, movement of people or vehicles, among other sources, which cause vibrations in structures and may lead to a collapse. Tuned mass damper (TMD), a passive control device, can be installed as an alternative to reduce vibration amplitudes. TMD has several advantages, such as large capacity to reduce amplitude of vibration, easy installation, low maintenance, low cost, among others. Optimizing TMD parameters is fundamental for obtaining best cost-benefit relation, i.e., greater amplitude reduction along with lower number of dampers or lower mass. In this context, this study aims at proposing, through numerical simulation, a method for optimizing TMD parameters when installing them on buildings under seismic excitation. Initially, a single-TMD case is considered, then simulations with multiple-TMDs (MTMDs) are run; lastly, unnecessary TMDs are discarded, obtaining the best structural response. For this purpose, a computational routine is developed on MatLab using Newmark direct integration method for equations of motion to determine the dynamic structural response. Both real and artificial earthquakes are considered for purposes of analysis. Artificial accelerograms are generated from proposed Kanai-Tajimi spectrum. First, structure is analyzed only with its own damping for comparison and reference. Second, a single or multiple-TMD optimization is carried out, in which the objective function is to minimize the maximum displacement at the top of the building, and the design variables are modal mass ratio (Structure-TMD), stiffness and damping of a single or multiple-TMD. Firefly and Backtracking Optimization algorithms are used for optimization. According to TMD settings, new dynamic structural responses are determined after optimizing parameters. Finally, the proposed method could optimize parameters of single or multiple-TMDs, considerably reducing structural responses after their installation, minimizing the risk of damage and building collapse. Thus, this study shows the possibility of designing TMDs or MTMDs both economically and effectively.