Dissertations / Theses on the topic 'Fluid viscous damper'

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. <br/><br/>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. <br/><br/>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.<br>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. <br/><br/>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. <br/><br/>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.

This dissertation was aimed at revisiting and integrating energy-based design criteria of dissipative bracing systems incorporating fluid-viscous spring-dampers as protective devices, for the seismic retrofit of frame structures. This objective was pursued by means of two main contributions. The first one concerned the introduction of an additional pre-sizing criterion of these systems aimed at guaranteeing a prompt activation of the spring-dampers starting from the early stages of the seismic response of the buildings where they are installed. The second one consisted in the evaluation of the influence of masonry infills and partitions in the assessment analysis in current state of the examined buildings, as well as in their verification analysis in retrofitted conditions, in order to evaluate the pre and post-intervention seismic performance of these non-structural elements, and the correlation with the response of the frame skeleton members. For this second objective, a no-tension strut model with multilinear “pivot”-type hysteretic behaviour was adopted as substitute element for the infill and partition panels. A trilinear axial force-displacement backbone curve was generated for the equivalent struts, and transformed in the lateral force-drift curve of the panels. The latter was then scanned in terms of sequential performance limits and ranges, so as to accurately follow the damage evolution in the panels. By collecting the results of the activity carried out during the Doctorate, this dissertation was written by presenting and discussing criteria and models, after short introductory notes, directly with the application to a series of demonstrative case studies concerning real buildings with different characteristics. This allowed substantiating the conceptual aspects of the examined topics with their practical implementation and possible use for other scholars and professional engineers operating in the same fields of interest.<br>This dissertation was aimed at revisiting and integrating energy-based design criteria of dissipative bracing systems incorporating fluid-viscous spring-dampers as protective devices, for the seismic retrofit of frame structures. This objective was pursued by means of two main contributions. The first one concerned the introduction of an additional pre-sizing criterion of these systems aimed at guaranteeing a prompt activation of the spring-dampers starting from the early stages of the seismic response of the buildings where they are installed. The second one consisted in the evaluation of the influence of masonry infills and partitions in the assessment analysis in current state of the examined buildings, as well as in their verification analysis in retrofitted conditions, in order to evaluate the pre and post-intervention seismic performance of these non-structural elements, and the correlation with the response of the frame skeleton members. For this second objective, a no-tension strut model with multilinear “pivot”-type hysteretic behaviour was adopted as substitute element for the infill and partition panels. A trilinear axial force-displacement backbone curve was generated for the equivalent struts, and transformed in the lateral force-drift curve of the panels. The latter was then scanned in terms of sequential performance limits and ranges, so as to accurately follow the damage evolution in the panels. By collecting the results of the activity carried out during the Doctorate, this dissertation was written by presenting and discussing criteria and models, after short introductory notes, directly with the application to a series of demonstrative case studies concerning real buildings with different characteristics. This allowed substantiating the conceptual aspects of the examined topics with their practical implementation and possible use for other scholars and professional engineers operating in the same fields of interest.

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.<br>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.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.<br>The addition of fluid viscous dampers to structures increases damping and reduce the lateral displacements due large earthquake loads, being an effective technique for seismic control of responses specially by severe earthquakes events and structures at high seismic hazard zone, safeguarding them from possible collapse. The objective of this research is to compare the structural performance of essential structures of confined masonry older than 50 years, asbuilt and retrofitted with viscous dampers. Additionally, the structure is analyzed with a traditional reinforcement technique such as reinforced concrete walls, in order to evaluate the feasibility of the first proposal. It was found that including dampers the drifts are reduced from 0.6% to its half, better performance that implementing concrete walls with 0.45% drift response. Besides stresses levels at masonry walls have been reduced better than retrofit building new concrete walls. It is shown the feasibility of the proposal in structural responses using fluid viscous dampers,

Nonstructural damage has been found to critically influence economic losses and building downtime following earthquakes. Attaining a target level of seismic performance mandates the harmonisation of structural and nonstructural performance. Retrofitting buildings with fluid viscous dampers (FVDs) can improve interstorey drifts and floor accelerations, parameters which characterise seismic demands. The distribution of dampers within a building and the amount of supplemental damping are critical decisions. Many placement methods have been proposed, however no conclusive optimal method has been identified. The objectives of the thesis included benchmarking the performance of code-compliant buildings, investigating the optimal amount of damping, and comparing major damper placement methods. The seismic performance of Eurocode-compliant concentric braced frame buildings was benchmarked. Structures were modelled in OpenSees and the FEMA P-58 procedure was used to assess seismic performance in repair costs, a comprehensive measure of total-building performance. Buildings may be demolished following an ultimate limit state earthquake due to high repair costs. Storeys satisfying the Eurocode drift limit for nonstructural protection nevertheless experienced drift- and acceleration-sensitive damage. Most damage was attributed to nonstructural systems. Acceleration-sensitive damage is of comparable or greater consequence than drift-sensitive damage. These findings should be more appropriately reflected in structural design procedures. The optimal amount of damping to minimise repair costs was identified as 30-40%, larger than previously suggested levels based on structural parameters. Six damper placement methods were evaluated using linear FVDs. No method produced optimal results for both drifts and accelerations. Iterative methods that purport to optimise performance did not achieve that objective: local rather than global parameters are considered, and optimising for a single parameter may worsen another that impacts damage. The storey shear strain energy method and uniform damping produced repair costs more favourable than, or equal to, the other placement methods. Damper placement optimisation may be successful for high-rise or irregular structures.

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.<br>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.<br><p>QC 20170425</p>

E’ stato indagato il comportamento degli edifici equipaggiati con un sistema di protezione sismica passivo basato sull’utilizzo di dissipatori fluido viscosi non lineari. L’elaborato vede una prima parte nella quale si individuano i metodi per lo svolgimento dell’analisi di risposta sismica locale. La seconda parte si concentra sui metodi di protezione sismica degli edifici e in particolare sul controllo dello smorzamento con dissipatori fluido viscosi. Ne è stato studiato il comportamento meccanico e sono stati analizzati i criteri di progettazione ed integrazione all’interno del sistema strutturale. L’ultima parte della presente tesi, svolta in collaborazione con lo Studio Tassinari e Associati di Ravenna, raccoglie le elaborazioni ed i risultati ottenuti dall’applicazione degli aspetti presentati nelle precedenti parti alla progettazione dell’ampliamento previsto per il complesso ospedaliero di Maria Cecilia Hospital di Cotignola (RA) del Gruppo Villa Maria. E’ stato sviluppato il confronto in termini di danni attesi a seguito di sisma e di costo di realizzazione tra diverse strategie progettuali: con dissipatori, a comportamento dissipativo e a comportamento non dissipativo. I risultati ottenuti con i metodi di predimensionamento sono stati verificati attraverso analisi dinamiche non lineari con impiego di storie temporali, come previsto dalla normativa vigente. I risultati hanno fornito una soluzione strutturale con dissipazione aggiuntiva vantaggiosa dal punto di vista della sicurezza degli elementi strutturali e non strutturali, che comporta un investimento poco superiore alla soluzione tradizionale. Il vantaggio rilevante è che a seguito di sisma non sono previsti danni e plasticizzazioni agli elementi strutturali inoltre la riduzione delle accelerazioni e degli spostamenti ai quali si sottopone la costruzione permette di salvaguardare gli elementi non strutturali e, aspetto fondamentale nell’ambito di strutture sanitarie e di ricerca, i contenuti.

The acoustics of small cavities raises interest of the scientific community since it involves particular damping mechanisms. In fluid dynamics, when a small perturbation is propagating within a Newtonian and heat-conducting fluid bounded by a rigid and isothermal surface, viscous and thermal dissipative mechanisms are generated near the walls. Such effects can have significant impact on the acoustic behaviour of the system.<p>Several types of practical applications can be cited, among which: hearing aids, micro-electro-mechanical systems (transducers, microphones and loud-speakers), absorbing materials made of thin capillary nets or small pores, dissipative silencers, thermo-acoustic heat exchangers, or any kind of device bringing into play small resonant cavities filled with a dissipative fluid (micro-acoustics).<p><p>This study focuses on appropriated reductions of the physical equations, in order to enhance the efficiency of the numerical resolution without adversely affecting the accuracy. Moreover, the proposed strategies lead to numerically stable systems as they involve only one scalar partial order differential equation (or equivalent fluid equation). The emphasis is put on the physical aspect of those reductions, their range of applicability, benefits and drawbacks.<p>Two new reduced models are proposed to estimate the visco-thermal acoustic wave propagation. A first extension deals with waveguide geometries and relax the hypothesis of the fluid at rest. The second original formulation addresses visco-thermal acoustics in 3D arbitrary geometries. This model is based on different considerations coming from existing techniques as well as the estimation of a wall-distance field.<p><p>A second part aims at studying the acoustic behaviour of biphasic materials and more specifically poro-elastic materials. This type of acoustic component is widely used in industry because of their good absorbing properties in the medium- and high-frequency <p>ranges.<p>A preliminary bibliographic research deals with the derivation of the set of partial order differential equations that account for both fluid/structure interactions and the anisotropy of a given poro-elastic material. It has been shown that transversely orientated capillary materials (for instance catalyst substrates) can be simulated using the proposed reduction technique.<p>At last, the modelling of the acoustic transmission between two domains separated by perforated or micro-perforated plates or thin plates of poro-elastic materials is discussed. The analogy between the rigid perforated plate models with an equivalent fluid formulation has been presented. As a result, this model has been extended in order to account for flexural effects of the solid part.<p><p><p>Ce travail porte sur l'étude de certains phénomènes d'amortissements intervenant dans l'acoustique des petites cavités. En méchanique des fluides, lorsqu'une petite perturbation se propage au sein d'un fluide newtonien et caloporteur borné par un mur rigide et isotherme, ces mécanismes dissipatifs particuliers se localisent aux abords des parois et jouent un rôle significatif dans certaines situations.<p>Parmi les exemples d'applications pratiques, il est possible de citer les appareils d'aide auditive, les systèmes microélectromécaniques (transducteurs, microphones et haut-parleurs), les matériaux absorbants constitués de fins réseaux capillaires ou de pores aux dimensions réduites, les systèmes de silencieux, d'échangeurs de chaleur thermo-acoustiques ou tout autre appareil mettant en jeu des cavités résonantes aux dimensions réduites (micro-acoustique).<p><p>L'étude proposée ici se focalise sur des stratégies de réduction appropriées des équations physiques, ceci afin d'améliorer l'efficacité du modèle tout en conservant une précision acceptable. Les techniques présentées aboutissent à des systèmes numériquement stables mettant en jeu une seule équation scalaire (ou équation fluide équivalent). Ainsi, l'accent est porté sur l'aspect physique des réductions, leurs domaines d'application, avantages et inconvénients.<p>Deux modèles originaux sont proposés afin de prédire la propagation acoustique visco-thermique. Une première extension permet d'évaluer la pression acoustique au sein de géométries particulières de type guides d'onde en présence d'un écoulement hydrodynamique. La seconde formulation présentée s'intéresse à l'acoustique dans des domaines 3D arbitraires. Cette méthode se base sur des considérations conjointes de modèles réduits existants ainsi que sur l'estimation d'un champ de distance à la plus proche paroi.<p><p>Dans une seconde partie, nous nous proposons d'étudier le comportement acoustique de matériaux biphasique et plus précisément les matériaux poro-élastiques (très utilisés dans l'industrie en raison de leurs caractéristiques absorbantes dans les domaines des moyennes et hautes fréquences).<p>Une étude bibliographique préliminaire nous a permis d'exprimer l'ensemble des équations aux dérivées <p>partielles modélisant à la fois les interactions fluide/structure et l'anisotropie générale des matériaux. <p>Cette réflexion nous a permis d'aboutir à un modèle de matériau isotrope transverse intéressant, combinant le modèle fluide proposé et la formulation acousto-élastique équivalente. Ainsi la modélisation de structures capillaires orientées (comme les matériaux utilisés dans les catalyseurs automobiles) s'en trouve grandement simplifiée.<p>Enfin, la transmission acoustique intervenant entre deux domaines fluides séparés par une plaque perforée ou micro-perforée ou bien une couche de matériau poreux a été étudiée. L'analogie entre les modèlisations existantes et un modèle générique de fluide équivalent a été mise en évidence. Pour finir, cette formulation a été étendue afin de prendre en compte les effets de flexion de la partie solide.<br>Doctorat en Sciences de l'ingénieur<br>info:eu-repo/semantics/nonPublished

Thesis (M.S.)--Florida State University, 2009.<br>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.

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.<br>Master of Science

The first purpose of this research is to investigate the effect of added viscous fluid dampers on a nine story special steel moment frame designed for strength in Seattle. At the initial stages of the work, knowing the fact that moment frames are almost always controlled by drift, it was thought that two different moment frames, controlled by strength or controlled by drift (stiffness), could be designed in Seattle and the effect of additional dampers on the structural behavior of the strength controlled design could be studied. <p> However, since ASCE 7 permits determining the elastic drifts by using the seismic design forces based on the computed fundamental period of the structure, without the upper limit (CuTa), the strength controlled design satisfied the drift limit requirements of ASCE 7. Although the strength controlled design meets the drift requirements, the stability checks of both ASCE 7 and the AISC Seismic Design Manual were not satisfied. Thus, the strength controlled frame was redesigned to meet the stability requirements, and the process is called stability controlled design.<p> By adding supplemental dampers to the strength controlled design, it was expected that the seismic drift would be controlled and a better structural behavior would be obtained in terms of dynamic stability. Incrementral Dynamic Analysis (IDA) was implemented to investigate the benefits of the dampers on the structural behavior. Using ten different earthquakes scaled up to a maximum target multiplier two, with ten increments, damage measures such as interstory drift, residual displacement, IDA dispersion, base shear, and roof displacement were studied. Using IDA dispersion, the effect of dampers on dynamic instability was also investigated in this study. <p> As a result, it was found that as the damping of the structure increases with the help of added dampers, the structural response gets better. Maximum and residual roof displacements, interstory drifts, and IDA dispersion decreases with increasing damping. In addition, by using supplemental damping, most of the collapses that occur for the inherently damped frames are prevented. <p> The second purpose of this research is to develop an improved â Hybridâ moment frame without added damping but by controlling the inelastic behavior. Hybrid Frames were designed as the combination of three different moment frames: Special, Intermediate and Ordinary Moment Frames (SMF, IMF, OMF). The design procedure of each bay, which corresponds to different moment frame systems, follows the rules of the related moment frame for that bay. By varying the plastic hinge capacities across the same level stories, four different Hybrid Frame designs were obtained. Nonlinear static pushover analysis was applied to these frames, and as expected, the more reduction in the plastic capacity of the Hybrid Frame, the earlier the pushover curve starts yielding and the later the negative post yield stiffness of the pushover curve was reached. It was observed that the effect of early plastic hinge forming in the frame, which caused inelastic hysteretic damping, and the relatively late formation of negative post yield stiffness resulted in a better dynamic behavior. <p> As a result of the IDA studies, as the frames become more â hybridâ , the residual displacements decrease significantly and then collapses are even prevented. This is considered as the positive effect of reaching the negative post yield stiffness late. The residual displacement was reduced for low intensity gentle earthquakes. The ductility demand IDA study proves that as the frames become more hybrid, the ductility demand increases for the special detailing frame, where plastic capacity was reduced, and decreases for the ordinary detailing frame, where the plastic capacity was increased. The Hybrid Frame system is expected to perform better than the traditional special moment frame, and to be more economical than the special moment frame because of the limited amount of special detailing.<br>Master of Science

This thesis presents the results of a study that uses Incremental Dynamic Analysis to assess the seismic performance of steel moment-resisting frames with fluid viscous dampers subjected to earthquake ground motions. The study systematically investigated the effects of linear and nonlinear dampers on the response of steel moment-resisting frames to earthquakes that varied in intensity and type. Both near-field and far-field motions were considered. Two different types of nonlinear dampers were investigated; one had a hardening and the other had a softening force-velocity relationship. The nonlinear dampers were calibrated to the linear dampers so that there was a basis of comparison. Maximum damper displacement is one of the parameters of the calibration, and it was varied to investigate its effect on structural response. Several nonlinear inelastic time history analyses were performed to obtain responses, such as peak base shear, peak interstory drift, or residual displacement index, which were plotted versus earthquake intensity to create individual IDA curves. Sets of related IDA curves provide a useful summary of the structural behavior for a wide range of variables. IDA curves for the tests with different damping types are presented. The results show that for both near-field and far-field ground motions the nonlinear dampers with a hardening force-velocity relationship are best suited to reduce undesirable drifts and residual displacements; however, these reductions come at the cost of high base shear forces.<br>Master of Science

En la actualidad, existen muchas estructuras de gran importancia y funcionalidad (hospitales, colegios, entre otros) que albergan un gran número de personas y de las que se espera que ante un evento sísmico severo se mantengan operativas, sin embargo, muchas de estas edificaciones esenciales han sido construidas con códigos sísmicos antiguos, los cuales podrían no tener los requerimientos actuales de resistencia y rigidez. Por lo que podrían fallar o tener un comportamiento deficiente ante sismos moderados y/o severos. Entonces, es así como la investigación aborda como caso de estudio uno de los bloques del Hospital Luis Negreiros, en el que se desarrolla un análisis sísmico y se propone su reforzamiento con dispositivos de protección sísmica, en especial disipadores de fluido viscoso, los cuales absorben la energía de entrada del sismo y aumentan el amortiguamiento de la estructura, lo que permite lograr un buen comportamiento durante la acción de sismos leves o moderados. La investigación consta de 6 capítulos, en el primer capítulo se explica los antecedentes de la investigación, hipótesis y objetivos, en el segundo capítulo se desarrolla el marco teórico de la investigación, una compilación del estado del arte relacionado a protección sísmica, el tercer capítulo explica el modelo matemático de los dispositivos así como las configuraciones existentes, en el cuarto capítulo se desarrolla la metodología de la investigación, en el quinto capítulo se analiza el caso de estudio y se plantea una propuesta de reforzamiento. En el sexto y sétimo capítulo se desarrollan las conclusiones y recomendaciones, respectivamente.<br>Currently, there are many structures of great importance and functionality (hospitals, schools, among others) that are home to a large number of people and which are expected to remain operational before a severe seismic event; however, many of these essential buildings have been built with old seismic codes, which may not have the current requirements for strength and rigidity. So they could fail or have a deficient behavior against moderate and / or severe earthquakes. Thus, this is how the research deals with one of the blocks of the Luis Negreiros Hospital as a case study, in which a seismic analysis is developed and its reinforcement is proposed with seismic protection devices, especially viscous fluid dissipaters, which absorbs the input energy of the earthquake and increase the damping of the structure, which allows to achieve good behavior during the action of mild or moderate earthquakes. The research consists of 6 chapters, in the first chapter the background of the research, hypotheses and objectives is explained, in the second chapter the theoretical framework of the research is developed, a compilation of the state of the art related to seismic protection, the third chapter explains the mathematical model of the devices as well as the existing configurations, in the fourth chapter the research methodology is developed, in the fifth chapter the case study is analyzed and a reinforcement proposal is proposed. In the sixth and seventh chapter the conclusions and recommendations are developed, respectively.<br>Tesis

碩士<br>國立臺灣大學<br>土木工程學研究所<br>105<br>Taiwan, located on Pacific Rim seismic belt, frequently experience earthquakes; hence structures need to be not only designed with the consideration of earthquake hazard, but also need to remain functional after earthquakes. Further developments of technology have shown that ductility design is no longer the only way to resist earthquakes. Passive or semi-active control systems have been developed and are being widely used. Viscous dampers are widely utilized in buildings, bridges and structures as a passive damping energy dissipating elements. However, the dampers on the market adjust their mechanical behaviors through altering physical geometry, which have high-cost production and modification in both the developmental and manufacturing phases. Furthermore, dampers cannot be customized, thus engineers will be limited by the fixed damper size during structural design. This study is dedicated to the development of a passive-type nano-fluid viscous damper, which is a simple physical mechanism and only requires suitable compound ratio of the nano-fluids to achieve the purposes of controlling the damping coefficient C and non-linear coefficient α of the damper’s mechanical formula: F = CVα. Nano-fluid viscous dampers have three main advantages: First, due to uncomplicated physical geometry, the production cost is relatively low. It is also needless to produce new dampers for calibration after testing, just to replace the internal filling of the nano-fluid, which may save on considerable R & D funding. Second, according to the characteristics of variability viscosity of the nano-fluid, nano-fluid viscous dampers are dual-α value damper, matching α>1 and α<1 performance under small and large velocity respectively. If designed properly, the damper may ameliorate the existing bridge damper oil seal wear caused by daily temperature difference and vehicle vibration. Furthermore, the damper enhances isolation system performance during small earthquakes. Last, through the establishment of a full range nano-fluid database, the manufacturer can produce customized dampers in the future, and consequently meet the engineers’ design, which can improve the accuracy and security of the structure. In this research, the fluid solvent and solute filling in nano-fluid viscous dampers are poly propylene glycol (PPG) and silica nanoparticles. The independent variables of the nano-fluid are PPG molecular weight, different types of silica particles, and fluid concentration due to rheology testing. The numerical model was established to fit the test results, and further analysis of the parameters were gathered from nonlinear regression. We deduced the mechanical behavior of the nano-fluid viscous damper based on the material properties of nano-fluid and fluid dynamics theories. Finally, a damper with a double rod and annular gap were designed and manufactured. Afterwards, we verified the correctness of the theoretical and numerical models through a series of damper performance test with different nano-fluids.

碩士<br>逢甲大學<br>土木及水利工程研究所<br>89<br>Many types of supplemental energy dissipating devices have been proposed to mitigate the harmful effects of earthquakes on structures. The fluid viscous damper that belongs to one kind of energy dissipation devices, extensively utilized in the aerospace and military applications, has recently been seen an accelerated growth in the civil engineering applications as a means of lessening structural responses induced by ground motions. A series of component tests with various cyclic loadings have been performed to determine the mechanical characteristics and frequency dependencies of fluid viscous dampers. In addition, experimental results from component tests indicate that the energy-absorbing capacity of fluid viscous dampers relates to ambient temperatures. In this study, an innovative mathematical model has been developed to describe the macroscopic behavior of the fluid viscous damper accounting for the ambient temperature, loading frequency and amplitude effects. A good agreement has been observed between theoretical and experimental results. Moreover, earthquake simulation tests have been carried out on a scaled three-story steel structure with and without fluid viscous dampers. The addition of supplemental dampers significantly reduces the response of the structure. A nonlinear analysis computer program including this advanced model is also adopted to compare the results of the experimental and numerical studies. Numerical analyses show a good correlation with results obtained from shaking table tests.

碩士<br>中興大學<br>土木工程學系所<br>99<br>The plans from 2009 to 2012 of Ministry of Education are respectively promoting "the plan of accelerating the older buildings&apos;&apos; retrofitting and rebuilding in general and vocational high school" and "the plan of accelerating the older buildings&apos;&apos; retrofitting and rebuilding in junior high school and elementary school." This is to solve the problem, “lack of seismic capacity of school buildings". According to the "elementary and junior high schools and school capacity Seismic Reinforcement Design work standard" of the Ministry of Education, we suggested the traditional reinforcement engineering methods such as “expansion column", "wing wall", and "shear wall". However, in the actual design process of seismic capacity reinforcement, we found that it requires a lot of demolition and reconstruction operations when adopting the traditional reinforcement engineering method. Besides, we often require the use of "big size" for the reinforcement of the base. Therefore, it caused the major problems on the engineering practice, including the time-consuming of the construction, high noise, and more waste. Is there any "effective solutions"? It is worth to explore. 　　This essay selected the shock-absorbing method, "fluid viscous damper", as the research object. It explored the structural seismic capacities of school buildings of the "fluid viscous damper" and the traditional construction methods, "expansion column”, “wing walls ", and "shear wall", by comparing their economy, construction, and usability analysis. This is for understanding if the" fluid viscous damper" is another "effective solution” for the reinforcement of structural seismic capacity for school buildings or not.

碩士<br>中華大學<br>土木工程學系碩士班<br>99<br>As Taiwan aggressively advocates green buildings, how to avoid wasting of resources in planning and design is an important issue. After the 921 earthquake, the technology of passive energy dissipation system used in building structure in Taiwan has become mature. However, most of designs merely use passive energy dissipation system to reduce the lateral deformation and vibration of buildings under strong shock, with the aim to improve the comfort of buildings, they neglect that the damping ratio of buildings is increased when the passive energy dissipation system is added, and the bearable earthquake is reduced. Therefore, the component size and reinforcement can be designed for small earthquakes. This study aims to discuss the changes in the designed consumption of reinforced bars and shock resistance of buildings with fluid viscous damper device. This study used ETABS and DRAWRC to design a concrete-steel building containing fluid viscous damper, and conducted nonlinear time-history analysis to obtain the equivalent damping ratio of the structure. The structure was analyzed and designed again using the design seismic force at the equivalent damping ratio, and the variance in the consumption of reinforced bars was discussed. Finally, the non-linear static pushover analysis of SERCB for evaluating the shock resistance of concrete-steel buildings was used for discussing the difference in the shock resistance of hollow structure and buildings with fluid viscous damper device. The results showed that the shock resistance of the hollow structure system can be greatly enhanced when it is equipped with the fluid viscous damper system, and it is increased by 20% at most. For the structure with additional fluid viscous damper system, if its reinforcement is designed based on the seismic force design of high damping ratio, its shock resistance is not influenced significantly, but the reinforced bars for beams and columns can be reduced by 15%.

碩士<br>國立中興大學<br>土木工程學系所<br>100<br>According to the existing standard design, the building structure installation of linear fluid viscous dampers as energy dissipation devices. It is usually associated with bracing systems converge into a series such like Maxwell Model. The advantages of fluid viscous dampers are not have the storage stiffness. If the braces stiffness are not enough then this advantages will not the facts. Use the Empty framework to be the basis for comparison. And take the equivalent linear way to derive the effective stiffness and damping loop area. By the pushover curve to obtain performance point like Vmax or SDR= 0.5% of the first position. And also obtain the performance ground acceleration. Form the different of the column section or the damper constant with different configurations, and with the braces stiffness change to performance the damping effect. Also comment with the results of the iterative analysis comparison. Use the software Midas Gen to do pushover analysis for data simulation.And then by the results of the analysis that the damping coefficient of the damper should not adopt the uniform distribution. Also know the simulation range of values to braces stiffness, and as well as the greatest opportunity to play in fluid viscous dampers. Final according to seismic capacity evaluation of the value shows the best design method.

碩士<br>國立嘉義大學<br>土木與水資源工程學系研究所<br>98<br>Nonlinear fluid viscous dampers are the most widely used seismic energy dissipation devices currently. The increasing of damping is to prevent excessive displacement. The purpose of the study is to discuss the accuracy of the equivalent damping ratio of nonlinear viscous dampers, and it is focused on the modification of the existing design equation of equivalent damping ratio. Conventional equation of equivalent damping ratio is obtained by harmonic loads that are deterministic, but the real external force is the earthquake loads that are random. Thus, this research is to modify the equation of equivalent damping ratio according to the real ground motions recorded in California. Using SAP2000 to calculate the maximum displacement of single-degree-of-freedom (SDOF) systems and comparing it of equivalent linear system with it of nonlinear systems. The results show that the equivalent damping ratio overestimate the maximum displacement of the short-period structure, while it underestimate the maximum displacement of the long-period structure. Therefore, this study will modify criterion of computing equivalent damping ratio. Damping coefficient of the nonlinear system is adjusted by multiplying a modification factor to get better equivalent damping ratio. Then, regression equations of damping modification factors are obtained by nonlinear regression analysis. The study show that the proposed equations of equivalent damping ratio for various site classes and α values acceptable and stable.

碩士<br>國立成功大學<br>土木工程學系碩博士班<br>90<br>Aseismic design have being paid much attention in recent years. Much more of energy dissipation devices are installed in buildings. One of the most important task is to generate the available design code so that the energy dissipation devices can be economically and systematically designed in order to strengthen the seismic resisting ability of the structures. Focuses on the buildings installed with linear viscous fluid dampers, theoretical model is analysied via software package SAP2000 by considering different factors such as various coefficient of dampers, various installed locations, and various number of dampers installed in different floors .More over ,proper design procedure is trying to be developed herein. Basically, it is found that dampers would be firstly considered to be installed at the floor with the greatest floor displacement, and at the vertical plane with the greatest seismic displacement to obtain the best control efficiency .It is suggested to determine the installation floor first , and then the installation vertical plane.Meanwhile, the number of the dampers installed could be determined by the properness of the installed region.

碩士<br>國立中興大學<br>土木工程學系所<br>103<br>Recent years have usually used fluid viscous dampers to improve the seismic capability of the whole structure in newly-built constructions and reinforcement constructions. But as regards the design of nonlinear fluid viscous dampers, such as the influence of brace stiffness and damper parameter, there is a lack of specific research results supply to the engineering department as the reference of designing. First of all, this study proposes a seismic capability evaluation method of considering the brace stiffness influence on the structures with nonlinear fluid viscous dampers. Moreover, with regard to the structures which has kept in linear elastic and not to raise the performance ground acceleration, we also discuss the influence and the contrast with variations on the velocity index and the brace stiffness of the nonlinear fluid viscous dampers. The study use the numerical analysis software to proceed the nonlinear static pushover analysis as the simulation, from the analysis, we know that the higher the nonlinear fluid viscous dampers brace stiffness are, the better energy dissipation effect the dampers will provide, however, the fluid viscous dampers-brace system will provide less strength. Therefore, the brace stiffness exists a best value, the study follows the standard and provides a economical value of the brace stiffness. That is, while the dampers are in maximum output, the braces are still keep in the linear elastic. While in the same maximum output, nonlinear fluid viscous dampers can provide more energy dissipation effect than linear fluid viscous dampers. However, while the structures are in the same maximum displacement, nonlinear fluid viscous dampers will provide more axial force on the columns.

碩士<br>國立中興大學<br>土木工程學系所<br>101<br>It was generally agreed the building structure installation of fluid viscous dampers can enhance the seismic capacity, but after the installation the amount of enhancement is unclear. Therefore, this study investigates the effects of the fluid viscous damper on a building structure. And perform pushover analysis to assess the seismic capacity. And this study will use that building structure can not yield under the 475 years Return period of the earthquake as the design conditions to design building structure. And perform pushover analysis to assess the seismic capacity.

In the last decade, the philosophy of seismic design has change from the force-based design to performances based design due to the advantage that presents. Also, the performance based the design presents less simplification of the force method representing in a more accurate form the real behavior of the structure. One method of this new philosophy is the direct displacement-based design (DDBD); this method permits to take in count in more exact form the nonlinear behavior than the force method. The DDBD can be used to design new structures and analyze the retrofit of structures of concrete, steel, composed and timber. In the case of steel structure, the formulas used represent a bilinear behavior of the material and the yield displacement proper of the steel structural system. This displacement method can be used with deferent demands optimizing the design. Another technique used in the performed based design is the pushover analysis. This method can be used to design new structures, evaluated design, optimizing design and retrofit the structures. The pushover considers in a more accurate form the nonlinear behavior of the structure, and it show the fail mechanism; it can analysis if the structure presents the condition of strong column weak beam. Also, it can be determining the ductility and the damping of the structure. Another concert that engineers have nowadays is the design higher structures that satisfy high demands. In order to reaches the performance that require this demand seismic protection systems are used such as damper and insulators. In this project, the fluid viscous dampers are study; the advantages that present their used and the behavior faced a seismic event using time history analysis. Finally, it is designing a Fluid viscous dampers in study case to analysis the performance achieved and the advantage presented in the structure.

Highway bridges function as the arteries of our society. Hence, it is essential that they remain operational following an earthquake. Unfortunately, a significant number of bridges worldwide, including in Canada, were constructed prior to the development of modern seismic design provisions. In many cases, such bridges are expected to perform poorly during earthquakes. According to a report published in 2000 by Ministry of Transportation of Ontario (MTO), in eastern Ontario alone, there are over 70 bridges that are structurally deficient. Current methods to retrofit these bridges to bring them into compliance with the existing codes would entail substantial structural modifications. Examples of such modifications include the replacement of existing rocker bearings with elastomeric bearings, structural strengthening of piers, and enlarging the bearing surfaces. These methods involve substantial cost, effort, and materials. An alternative means to retrofit structurally deficient bridges is investigated in this thesis. This method involves using a combination of elastomeric bearings and fluid dampers to retrofit highway bridges. In principle, these devices work in the same way as shock absorbers in automobiles. They absorb shock and dissipate the vibration energy to the environment as heat. In the case of bridges, earthquakes impart the shock to the structure. Before these devices can be implemented in practice, there are many issues that need to be understood with respect to their performance and modelling. Moreover, a comparative assessment between popular retrofit options employing isolation systems needs to be undertaken to verify and provide a benchmark to assess their performance. The Mississippi River Bridge near Ottawa is chosen as a test structure to conduct this study. This bridge already contains an advanced isolation system, and has an extensive documentation available for modelling and verification. Various retrofit options will be studied and compared with the existing isolation design for this bridge. In all cases, the effect of soil-structure interaction is included. A comprehensive set of performance indices are used to evaluate the performance of various retrofit options. All the models are constructed in the open source software, OpenSees. The research demonstrates that the proposed approach is a viable retrofit method for highway bridges. Moreover, compared to advanced isolation systems, retrofit using elastomeric bearings with viscous dampers was successful on transferring lower loads to the substructure, and resulted in lower superstructure displacements. Though this study involved one bridge, it has provided a computational test bed to perform further studies and has provided valuable insight into the modeling and performance of retrofit solutions.

碩士<br>國立中興大學<br>土木工程學系所<br>106<br>These days, using dampers to improve earthquake resistance of buildings is quite common. Therefore, this study provides a summary and explanation of the design methods and earthquake resistance evaluation for fluid viscous dampers, which is often used in engineering. The design methods includes the selection of the parameter for damper elements and the section design of its supporting frame; Equivalent stiffness and damping ratio are two key points in earthquake resistance evaluation, so this study introduce the principle and calculation in detail. After the introduction of how to comply earthquake resistance evaluation for buildings containing fluid viscous damper, this study proposes an analysis method that close to the actual structural behavior of the evaluation method. Although the result is more accurate and close to the actual behavior of the structure, the time it takes is many times longer than the previous method, and the previous analysis method is relatively conservative compared to the method proposed in this study. Therefore, when evaluating the earthquake resistance of structures containing fluid viscous dampers, it is sufficient to use the original method which considers the equivalent stiffness for push-over analysis. This paper also integrates the retrofitting design method with fluid viscous dampers and studies the differences in the design of different installation types. The dampers design must first determine the speed index α of the damper to calculate the required value of the damping coefficient C, so how to choose α is also one of the focuses. At the same cost, the smaller α has a positive correlation effect on the energy dissipation and intensity contribution of earthquake resistance, but it results in a greater force burden on the structure; In the damper retrofitting design, the support frame is also one of the design objects, so this study discuss it. In the case of using the same damper, when the support frame is designed, if the stiffness of frame is designed to be greater than minimum requirement, the burden on structure can be reduced when the structure is affected by the earthquake. Last but not least, by applying the retrofitting design and earthquake resistance evaluation to an actual case, verifies the variations of damper parameters influence the structure is consistent with the conclusion of this study. In order to further understand the dampers, this study respectively use dampers of α is 1.0 and 0.2 to retrofit the actual case to the same earthquake resistance. Although the damper with α is 1.0 can effectively reduce the stress of the foundation at the performance point, the maximum stress may occur outside the performance point.

碩士<br>國立中興大學<br>土木工程學系所<br>104<br>Since the early seismic design specifications of buildings and the construction method were not as good as that of today’s standards, therefore the designed building seismic capacity is obviously insufficient and the reinforcement is needed. Now, the traditional construction method enhances the seismic capacity by using column jacketing, column with wing walls or increase of shear walls. To conform to the trend of the times, a combination of a building and energy reduction with shock absorption system can increase better seismic capacity and does not lower the amount of space, it can absorb more seismic energy as well compared to the traditional reinforcement. Nonlinear fluid viscous dampers are an energy reduction and shock absorption system often used in the structural system to increase strength of the damping force and to improve the seismic capacity of buildings to achieve a damping effect. Today’s engineers use Trial and Error Method to calculate an answer when designing the damping force. The designing duration would be too lengthy and leads to a low efficiency. This paper proposes a methodology to quickly find the desired damping force and apply to actual cases, using spectral acceleration Sa and acceleration value Ap, which are post-reinforcement seismic capability meeting the performance point, to apply the design equations to obtain the desired damping ratio, and further get the damping force needed to increase. In this way you will save computing time to complete the design of nonlinear fluid viscous dampers. Although the installation of the damper is effective for the designed building seismic capacity but it must to study for the affect on columns ,this article research the axial forces of low-rise buildings and high-rise buildings result in change of the bending on the structure columns ,whether to have an effect on seismic capacity of structural.

碩士<br>臺灣大學<br>土木工程學研究所<br>95<br>The purpose of this thesis was to study responses of bridges with sliding rubber bearings and restrainers or fluid viscous dampers under earthquakes. In this study, three earthquake time histories corresponding to the design spectrum were applied to nonlinear dynamic analysis of the structure. Subjects were the beam’s displacement (relative to the top of the column) and the force taken by the substructure. Variables used included period of structures, safety factors and gap of restrainers, damping exponent and coefficient of fluid viscous dampers. Four models were tested to study the effect of different variables on the behavior of a bridge with sliding rubber bearings and unseating prevention devices. Besides, the study also proposed simple design procedures for restrainers and fluid viscous dampers. Finally, collision between two superstructures was simulated in order to investigate if collision can effectively control the beam’s displacement (relative to the top of the column).

碩士<br>國立暨南國際大學<br>土木工程學系<br>99<br>The engineer’s purpose of installed the liquid viscosity dampers in the structures is energy dissipation, they prefer to use the liquid resistor which has smaller speed-index n, the reason is that when small earthquakes comes, it can produce output power to control structural’s vibration, but when the bigger earthquake comes, output power will not be too large to destroy structural. There are three methods to reduce n value of gap damper: high-speed, small gap and thick silicone oil, but using these methods will also have other adverse side effects. In this study, we excluded these three methods, but we started from the silicone oil. Through literature we can know that mixed silicone oil is more easily to become thinning, therefore, we use mixed silicone oil to experiments. Each groups are mixed by five kind of pure silicone oil, and each group’s viscosity is 1000 cps, finally, we analysis and comparison the test data of the damper. The result is that mixed silicone oil can reduce n value and about 0.1 lower than the pure Silicone oil of the damper.

碩士<br>國立交通大學<br>土木工程系所<br>105<br>The hi-tech industries of Taiwan were seriously damaged in an earthquake of Magnitude 6.6 on February 6, 2016 and suffered from a substantial financial loss estimated to be nearly a hundred billion NT dollars. Statistics shows that loss attributes mainly to the automated stocker system (STK) from which massive foups or cassettes were shaken off, and the core production lines were paralyzed as a result. This study proposes to mitigate the seismic response of the stockers for the display industry, based on the concept of structural control, by introducing viscous fluid dampers in between the ceiling and the top of the STK. The energy-dissipative mechanism will be activated passively by the relative motion during earthquakes to depress the vibration of the STK. A series of shake table tests has been conducted to verify the feasibility of the proposed scheme on a full-scale stocker provided by the industry under realistic earthquake scenarios, including Kobe Earthquake and Ji-Ji earthquake recorded at TCU017 station. Linear dampers with optimal damping coefficient determined from a previous study are considered and verified via component tests. Experimental results indicate a great success of the strategy that both the displacement and acceleration responses of the STK are simultaneously reduced to a iv large extent. The control efficiency increases with the earthquake intensity and the unbalanced torsional behavior of the STK is remarkably depressed. In this thesis, the ETABS is adopted for dynamic simulation of the shake table tests under the same excitations to predict the dynamic responses of the STK, steel frame and dampers for comparison. The amplitudes and trends of the dynamic responses from the simulations are well correlated with the experimental results, indicating sufficiency of the methodology in justifying adequacy of the control design, and therefore eligible to serve as a tool for seismic protective design and assessment of the STK for the TFT-LCD factories. Moreover, the seismic control design and evaluation of a STK for practical application has been carried out under bi-axial earthquake excitations to help a domestic corporation in the display industry planning the first demonstrative project on seismic retrofit of STK in Taiwan.

碩士<br>國立交通大學<br>土木工程系所<br>105<br>The hi-tech industries in the Science Park at Southern Taiwan were heavily damaged and suffered from substantial financial loss estimated to be over ten billion NT dollars in 206 Earthquake. Statistics shows that the loss of the semiconductor factories attributes mainly to the automated stocker system (STK in brief) from which massive foups were shaken off with products damaged. In view of strategic concerns on risk minimization, enhancing earthquake-resisting capability of the STKs has become the highest priority among others for semiconductor industry. Based on the concept of structural control, NCTU research team proposes to mitigate the seismic response of stockers by introducing small size linear viscous fluid dampers on top of the stockers against ceiling. With the dampers activated by the relative motion between them, the stocker is controlled in a way to reduce both its acceleration response and lateral displacement, and the seismic risk of the automated stocker system can be minimized as a result. As an effort to assist two domestic semiconductor companies (referred to as M fab and S fab) with seismic damage control of automation storage systems, including inter-story and intra-story STK of various types, this study has conducted a series of numerical simulations. Effectiveness of the seismic control strategy is assessed under various design considerations, such as combinations of the earthquake excitations from different imparting directions and of different intensities. Some of the stockers in S fab are implemented with aseismic links between the ceiling and the top of the STK. The feasibility and potential problems of using the links for earthquake protective design have also been assessed in this study. The optimum damping coefficient and desired specification of the fluid dampers corresponding to a reasonable configuration and number of dampers have been determined via parametric studies. The results indicate that, if the parameters of the viscous fluid dampers are properly determined, the proposed energy-dissipative scheme could significantly mitigate the displacement and acceleration responses of the stocker simultaneously, and therefore minimize the risk of the foups from being shaken off, regardless of the types of STKs. On the other hand, despite of that the displacement responses of the STK could be reduced by the aseismic links, the acceleration responses might be in many circumstances amplified to a large extent and therefore not worthwhile. Moreover, the forces generated in the links are excessive that the bolts could be damaged and the ceiling collapsed. On the contrary, the strategy by using the viscous fluid dampers in the proposed manner not only could achieve the expected seismic performance but also minimize the control force demand. Therefore, it is feasible for practical application. The proposed scheme by the NCTU research team for seismic control of the automated stocker systems has been adopted by M fab. To ensure that the products provided by the damper manufacturer meet the requirements, the specification for component testing of the viscous fluid dampers has been devised. The team has managed to help two domestic damper manufacturers successfully developing the desired products. Component tests of the viscous fluid dampers have been completed and justified in accordance with the specification. Meanwhile, two companies of the display industry have also agreed to use the proposed scheme. Planning and design of preliminary demonstrative projects are currently underway. It is believed that if the scheme could be extensively adopted, the seismic risk of domestic hi-tech industries would be appreciably reduced.

Στην εργασία αυτή διερευνάται η δυναμική απόκριση κρυογενικών δεξαμενών υγροποιημένου φυσικού αερίου υποκείμενων σε δράση σεισμού. Επειδή οι εν λόγω δεξαμενές αποτελούν κρίσιμα στοιχεία για τη λειτουργία ενός συστήματος διανομής φυσικού αερίου και επειδή ενδεχόμενη καταστροφική αστοχία τους θα είχε δυσβάστακτες κοινωνικές επιπτώσεις, ιδιαίτερα αυστηρές απαιτήσεις ισχύουν σχετικά με τον αντισεισμικό σχεδιασμό τους. Για το σχεδιασμό έναντι σεισμού προδιαγράφονται συνήθως ένα σεισμικό γεγονός με μέση περίοδο επαναφοράς της τάξης των 500 ετών, κατά το οποίο οι δεξαμενές απαιτείται να παραμένουν πλήρως λειτουργικές, και ένα σεισμικό γεγονός με μέση περίοδο επαναφοράς της τάξης των 5000 έως 10000 ετών, κατά το οποίο απαιτείται η εξασφάλιση της ασφαλούς διακοπής της λειτουργίας των δεξαμενών, ενώ ελάχιστη μόνο βλάβη είναι αποδεκτή στα δομικά στοιχεία τους. Οι εν λόγω δεξαμενές αποτελούνται από δύο κελύφη: Ένα εξωτερικό κυλινδρικό κέλυφος από προεντεταμένο σκυρόδεμα με θολωτή στέγη από οπλισμένο σκυρόδεμα και ένα εσωτερικό κέλυφος από κρυογενικό χάλυβα, εντός του οποίου αποθηκεύεται το προϊόν. Τα δύο κελύφη εδράζονται σε κοινή πλάκα βάσης. Στην εργασία αυτή εξετάζονται δύο εναλλακτικοί τρόποι έδρασης της πλάκας βάσης: α) απλή έδραση επί του διαμορφωμένου εδάφους και β) εφαρμογή κάποιας διάταξης σεισμικής μόνωσης επί της οποίας εδράζεται η πλάκα βάσης. Ειδικότερα, εξετάζονται τα ακόλουθα συστήματα σεισμικής μόνωσης: α) μόνωση με ελαστομεταλλικά εφέδρανα με ελαστομερές υψηλής απόσβεσης, β) μόνωση με ελαστομεταλλικά εφέδρανα με πυρήνα μόλυβδου, και γ) μόνωση με συνδυασμό γραμμικών ελαστομεταλλικών εφεδράνων και μη γραμμικών αποσβεστήρων. Στις ιδιαιτερότητες του δυναμικού προβλήματος περιλαμβάνονται, εκτός από την επίδραση της μόνωσης, η δυναμική αλληλεπίδραση των δύο κελυφών, η δυναμική αλληλεπίδραση υγρού-δεξαμενής, ο κυματισμός της ελεύθερης επιφάνειας του υγρού και η δυναμική αλληλεπίδραση εδάφους-δεξαμενής. Τα φαινόμενα αυτά λαμβάνονται υπόψη στην ανάλυση. Για τη μελέτη του κυματισμού της ελεύθερης επιφάνειας χρησιμοποιείται η γραμμική θεωρία κυμάτων. Για τη μελέτη της αλληλεπίδρασης υγρού-δεξαμενής εφαρμόζεται μια προσέγγιση τύπου Lagrange με χρήση πεπερασμένων στοιχείων υγρού. Για τη μελέτη της αλληλεπίδρασης εδάφους-δεξαμενής χρησιμοποιούνται συγκεντρωμένα στοιχεία δυσπαραμορφωσιμότητας και απόσβεσης. Επίσης, συγκεντρωμένα στοιχεία δυσπαραμορφωσιμότητας και απόσβεσης χρησιμοποιούνται για την προσομοίωση των συστημάτων μόνωσης. Τα χαρακτηριστικά των παραπάνω συγκεντρωμένων στοιχείων για την προσομοίωση της αλληλεπίδρασης εδάφους-δεξαμενής και των συστημάτων μόνωσης επιλέγονται με βάση ρεαλιστικές υποθέσεις για τις δυναμικές ιδιότητες του εδάφους θεμελίωσης και τα χαρακτηριστικά των συστημάτων μόνωσης. Δύο περιπτώσεις υφιστάμενων δεξαμενών υιοθετούνται προς ανάλυση. Οι δύο δεξαμενές διαφέρουν κυρίως ως προς τη χωρητικότητα και το λόγο ύψους προς ακτίνα. Και οι δύο δεξαμενές έχουν μελετηθεί και κατασκευαστεί χωρίς σεισμική μόνωση. Ένα συνθετικό επιταχυνσιογράφημα συμβατό με το φάσμα απόκρισης σχεδιασμού του Ευροκώδικα 8 για λόγο απόσβεσης 5%, για την αντίστοιχη κατηγορία εδάφους και για μέγιστη εδαφική επιτάχυνση λίγο μεγαλύτερη από αυτή για την οποία είναι σχεδιασμένες οι δεξαμενές περιγράφει τη διέγερση της κατασκευής στην οριζόντια διεύθυνση. Για την ανάλυση αναπτύσσεται ένα συνολικό παραμετρικό προσομοίωμα πεπερασμένων στοιχείων το οποίο περιλαμβάνει τα δύο κελύφη και το αποθηκευμένο υγρό. Στο προσομοίωμα συμπεριλαμβάνονται, ανάλογα με την περίπτωση που κάθε φορά αναλύεται, τα κατάλληλα στοιχεία για την προσομοίωση της αλληλεπίδρασης εδάφους-δεξαμενής ή των διαφόρων συστημάτων μόνωσης. Το προσομοίωμα χρησιμοποιείται για τον υπολογισμό των ιδιομορφών και την πραγματοποίηση δυναμικών γραμμικών και μη γραμμικών αναλύσεων με ολοκλήρωση στο πεδίο του χρόνου. Οι μη γραμμικές αναλύσεις είναι αναγκαίες για να ληφθεί υπόψη με ρεαλιστικό τρόπο η έντονα μη γραμμική συμπεριφορά των συστημάτων μόνωσης. Στην περίπτωση αυτή η μη γραμμικότητα είναι συγκεντρωμένη στα στοιχεία που προσομοιώνουν τη μόνωση ενώ για την υπόλοιπη κατασκευή γίνεται σε κάθε περίπτωση η παραδοχή γραμμικής συμπεριφοράς. Η παραδοχή αυτή προκύπτει από το γεγονός ότι για τις δεξαμενές αυτού του τύπου η αποδεκτή βλάβη, και επομένως μη γραμμικότητα στη συμπεριφορά, των δομικών στοιχείων είναι ελάχιστη. Παρουσιάζονται επιλεγμένα αποτελέσματα των αναλύσεων που πραγματοποιήθηκαν με χρήση του προσομοιώματος πεπερασμένων στοιχείων. Τα αποτελέσματα αυτά αναφέρονται κυρίως στην τέμνουσα βάσης, τη ροπή ανατροπής, τις οριζόντιες μετακινήσεις της κατασκευής σε διάφορες στάθμες και το ύψος του κυματισμού. Έμφαση δίνεται στην ποσοτικοποίηση της επίδρασης της αλληλεπίδρασης εδάφους-δεξαμενής και της σεισμική μόνωσης στα ανωτέρω μεγέθη. Η εργασία τελειώνει με γενικά συμπεράσματα.<br>In the present work the dynamic response of liquefied natural gas cryogenic tanks subjected to earthquake action is investigated. Since these tanks are critical elements for the function of a natural gas distribution system and because a potential failure of them could lead to a major disaster, very severe requirements concerning the seismic design of these tanks are imposed. For the design against earthquake action two seismic events are generally considered: an event with a mean return period of 475 years during which the tanks are expected to remain fully operational and an event with a mean return period of the order of 5000 to 1000 years during which the safe shut down of the tanks is to be ensured, while minimum damage is accepted at the structural parts of the tanks. The type of tanks under consideration is constituted of two shells: an outer one made of prestressed concrete and an inner one made of cryogenic steel in which the product is stored. Both shells rest on a common base slab. In these work two alternative ways for the support of this slab are examined: a) the slab lays directly on the ground and b) the slab lays on a number of devices which provide seismic isolation. The following isolation systems are examined. a) high damping rubber bearings, b) lead core rubber bearings and c) low damping rubber bearing in conjunction with non-linear viscous dampers. The examined structural dynamic problem is characterised by certain particularities, besides the one of the implementation of an isolation system. The most important of them are sloshing of the free surface, dynamic fluid-structure interaction, dynamic soil-structure interaction and interaction between the inner and outer shell. These phenomena are taken into consideration in the preformed analyses. For the modeling of the free surface effect the realistic assumption of small wave height is made and the linear wave theory is employed. For the modeling of the fluid-structure interaction a Lagrangian approach is applied using finite elements for the modeling of the liquid and the solid domain. The soil-structure interaction is simulated by using concentrated stiffness and damping elements. Concentrated stiffness and damping elements are used for the modeling of the isolation systems as well. Two cases of existing tanks are adopted for analysis. The two tanks differ mainly in capacity and in the height to radius ratio. Both tanks are designed and constructed without seismic isolation. A global parametric finite element model is developed for the analyses. In this model the appropriate elements are incorporated for the modeling of the soil-structure interaction and the seismic isolation system, depending on the analysed case. The model is used for the calculation of eigenmodes and eigenfrequencies and for performing linear and non-linear transient analyses in time domain. Non-linear analyses are necessary in order for the highly non-linear behavior of the isolation devices to be properly simulated. In these cases the non-linearity is concentrated at the elements which simulate the seismic isolation system while the rest of the structure is considered elastic in all cases. This consideration is justified by the fact that for these tanks the acceptable damage, and consequently non-linearity in the behavior of the structural part, is minimum. Selective results of the performed analyses are presented. These results refer mainly to base shear forces, overturning moments, horizontal displacements at different levels of the tank and sloshing heights. Emphasis is on the quantification of the impact of the soil-structure interaction and the implementation of the examined seismic isolation systems.