The objective of this thesis is to develop a dual-functional approach to effectively mitigate the earthquake induced vibrations of low- or mid-rise buildings, and at the same time to efficiently harvest utility-scale energy by using an optimally configured multi-resonant electromagnetic shunt in base isolation. In this research, two multi-resonant shunt configurations, parallel and series, were proposed and optimized based on the H2 criteria when the base isolation system is subjected to ground acceleration excitations. The performance of the proposed multi-resonant electromagnetic shunt was compared with traditional multiple tuned mass dampers (TMDs) applied to the base isolation system. It shows that, for multiple TMDs and multi-resonant electromagnetic shunt dampers with 5% total stiffness ratio, the parallel shunt electromagnetic shunt can achieve the best vibration mitigation performance among other types of multi-resonant dampers, including parallel TMDs, series TMDs and the series electromagnetic shunt damper. Case study of a base-isolated structure was analyzed to investigate the effectiveness of the proposed multi-resonant electromagnetic shunt. It shows that both multi-mode shunt circuits outperform single mode shunt circuit by suppressing the primary and the second vibration modes simultaneously. Comparatively, the parallel shunt circuit is more effective in vibration mitigation and energy harvesting, and is also more robust in parameter mistuning than the series shunt circuit. The time history response analysis shows that, under the recorded Northridge earthquake, the instant peak power and total average power capable to be harvested by the multi-resonant shunt can reach up to 1.18 MW and 203.37KW, respectively. This thesis further experimentally validated the effectiveness of the multi-resonant electromagnetic shunt on a scaled-down base-isolated building. The impact hammer test shows that the multi-resonant electromagnetic shunt can achieve enhanced vibration suppression by reducing the first resonant peak by 27.50dB and the second resonant peak by 22.57dB regarding the primary structure acceleration. The shake table test shows that under scaled Kobe and Northridge earthquake signals, the electromagnetic shunt can effectively reduce the vibration resonant peak value by 38.92% and 66.61%, respectively. The voltage simultaneously generated in the multi-mode shunt circuit was also obtained, which demonstrated the dual functions of the multi-resonant electromagnetic shunt in base isolation. / Master of Science

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

Basado en la idea de reducir la demanda sísmica en lugar de aumentar la capacidad resistente de las estructuras, el aislamiento sísmico es un método simple para mitigar o reducir los posibles daños producidos por los terremotos. La correcta aplicación de esta tecnología conduce a un mejor comportamiento de las estructuras, que sigue siendo esencialmente elástico durante los terremotos de gran magnitud. El núcleo de esta tecnología es el aislador. La mayoría de los aisladores sísmicos disponibles en la actualidad siguen teniendo limitaciones prácticas que impiden que funcionen según lo previsto e imponen restricciones a su uso efectivo y al nivel de protección proporcionado. En esta Tesis, se presenta un aislador sísmico avanzado llamado "roll-n-cage (RNC)". Se propone investigar su eficiencia a través de simulación numérica, en un intento de crear un sistema de aislamiento sísmico práctico, efectivo y económico, que tiene por objeto resolver los principales inconvenientes de los actuales sistemas de aislamiento sísmico, manteniendo sus principales ventajas. Este aislador incorpora aislamiento, disipación de energía, amortiguamiento y capacidad de fuerza recuperadora en una sola unidad. Además, ofrece una resistencia al viento significativa y una amplia gama de flexibilidad horizontal, por lo que es adecuado para proteger las estructuras de masa ligera, moderada y grande, así como para proteger equipos sensibles, hardware y / o antigüedades alojados en edificios. Por otra parte, las cuestiones relativas a la viabilidad, los costes de construcción y la disponibilidad de materiales, reducción o prevención de las respuestas de torsión y la resistencia a la elevación son abordados a fondo durante el diseño del aislador RNC. El aislador RNC propuesto es descrito en profundidad y sus principios de funcionamiento son presentados en detalle. La caracterización mecánica del dispositivo se ha llevado a cabo por medio de un código computacional sofisticado que simula la respuesta de los dispositivos como si estuvieran sujetos a una máquina de pruebas reales. A través de este esquema, se consigue analizar numéricamente el comportamiento del aislador RNC bajo el efecto simultáneo de cargas horizontales y verticales, como se da típicamente en situaciones prácticas. Además, se presenta una descripción matemática de las principales características asociadas a la rodadura de los aisladores RNC. Asimismo se obtiene un modelo matemático para describir en una forma razonable y manejable la relación fuerza desplazamiento exhibida por el aislador de RNC. Para evaluar la viabilidad del aislador RNC y para comprobar su capacidad para proteger los sistemas estructurales y no estructurales de los riesgos sísmicos, el dispositivo se implementa numéricamente en una variedad de estructuras con masas ligeras y grandes, además de en equipos sensibles alojados en los pisos superiores de dichas estructuras. Para extraer conclusiones de carácter relativamente general sobre el funcionamiento del aislador RNC, se estudia una amplia gama de terremotos y de características y propiedades de los aisladores y de las estructuras.Los resultados numéricos revelan que el aislador RNC propuesto puede reducir la respuesta sísmica frente a un amplio rango de excitaciones sísmicas, mientras que exhibe un rendimiento robusto para una gran variedad de estructuras. La Tesis incluye como apéndice un estudio en profundidad sobre el modelo de histéresis de Bouc-Wen. El estudio contiene una revisión de los primeros y últimos avances y aplicaciones de este modelo, que es ampliamente utilizado en la descripción de fenómenos de histéresis en las estructuras. / Based on the concept of reducing seismic demand rather than increasing the earthquake resistant capacity of structures, seismic isolation is a surprisingly simple approach to mitigate or reduce earthquake damage potential. Proper application of this complex technology leads to better performing structures that will remain essentially elastic during large earthquakes. The core of this technology is the isolator. Most currently available seismic isolators still have practical limitations causing them not to function as anticipated and impose restrictions to their proper use and to the provided protection level. In this dissertation, an advanced rolling-based seismic isolator, named roll-n-cage (RNC) isolator, is proposed and investigated via numerical simulation as an attempt to create a practical, effective, and economic seismic isolation system that aims to fix the main drawbacks of the current seismic isolation systems while keeping their main advantages. This isolator incorporates isolation, energy dissipation, buffer and restoring force mechanisms in a single unit. Further, it offers a significant wind resistance and a great range of horizontal flexibility making it ideal to protect light, moderate and heavy mass structures as well as precious housed motion-sensitive equipment, hardware and/or antiquities. Moreover, issues related to practicality, construction costs and material availability, reducing or preventing torsional responses and uplift resistance are thoroughly addressed during the RNC bearing design.The proposed RNC isolator is deeply described and its principles of operation are extensively highlighted. The mechanical characterization of the device has been carried out by means of a sophisticated computer code in a machine-like environment, which accurately simulates the response of the device subjected to a real testing machine. Through this machine-like environment, a general scheme is followed to numerically examine the behavior of the RNC isolator under simultaneous horizontal and vertical loads as in typical practical situations. Further, a mathematical description of the main features associated to rolling of the RNC isolator is presented. An input-output mathematical model is obtained to describe in a reasonable and manageable form the force-displacement relationship exhibited by the RNC isolator.To assess the feasibility of the RNC isolator and to check its ability to protect structural and nonstructural systems from seismic hazards, it is numerically implemented to a variety of structures having light to heavy masses, in addition to motion-sensitive equipment housed in upper building floors. Further, and to draw relatively general conclusions about the performance of the RNC isolator, a wide range of ground motions, isolator characteristics and structural properties is considered. The numerical results reveal that the proposed RNC isolation bearing can mitigate the seismic responses under a variety of ground motion excitations while exhibiting robust performance for a wide range of structures. The dissertation is appended with an in-depth survey, that contains a review of the past, recent developments and implementations of the versatile Bouc-Wen model of smooth hysteresis, which is used extensively in modeling the hysteresis phenomenon in the dynamically excited nonlinear structures. This survey is the first of its kind about the model since its origination more than 30 years ago. The objective is to present some of the popular approaches that have utilized and/or developed that model to capture the hysteretic behavior offered by a variety of nonlinear systems. Then, the evaluation of their results and contributions (if any) is carried out to highlight their assets and limitations and to identify future directions in this research area.

The objective of this study is to reduce the interstory drifts, floor accelerations, and shear forces experienced by masonry houses subject to seismic excitation. Ambient vibration testing was performed on a case study structure in Maip�, Chile, to identify characteristics of the system. Upon creating a multiple degree-of-freedom (MDOF) model of the structure, the effect of implementing several base isolation techniques is assessed. The isolation techniques analyzed include the use of friction pendulum systems (FPS), high-damping rubber bearings (HDRB), two hybrid systems involving HDRB and shape memory alloys (SMA), and precast-prestressed pile (PPP) isolators. The dynamic behavior of each device is numerically modeled using analytical formulations and experimental data through the means of fuzzy inference systems (FIS) and S-functions. A multiobjective genetic algorithm is utilized to optimize the parameters of the FPS and the PPP isolation systems, while a trial-and-error method is employed to optimize characteristic parameters of the other devices. Two cases are studied: one case involves using eight devices in each isolation system and optimizing the parameters of each device, resulting in different isolated periods for each system, while the other case involves using the number of devices and device parameters that result in a 1.0 sec fundamental period of vibration for each baseisolated structure. For both cases, the optimized devices are simulated in the numerical model of the case study structure, which is subjected to a suite of earthquake records. Numerical results for the devices studied indicate significant reductions in responses of the base-isolated structures in comparison with their counterparts in the fixed-base structure. Metrics monitored include base shear, structural shear, interstory drift, and floor acceleration. In particular, the PPP isolation system in the first case reduces the peak base shear, RMS floor acceleration, peak structural shear, peak interstory drift, and peak floor acceleration by at least 88, 87, 95, 95, and 94%, respectively, for all of the Chilean earthquakes considered. The PPP isolation system in the second case (yielding a 1.0 sec period) and the FPS isolation systems in both cases also significantly reduce the response of the base-isolated structure from that of the fixed-base structure.

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

In this thesis primarily structural induced liquefaction potential was aimed to be analyzed. Also the effect of base isolation systems both on structural performance and liquefaction potential was studied. FLAC software was chosen for the analyses so that structure and soil could be modeled together. By these means the soil structure interaction effects were also examined. Four different structures and three different sites were analyzed under two different input motions. All the structures were also analyzed as base isolated. It was mainly found that depending on the structural type and for a certain depth the liquefaction potential could be higher under the structure than the one in the free field. Also it was concluded that base isolation systems were very effective for decreasing the story drifts, shear forces in the structure and liquefaction potential in the soil. It was also found that the interaction took place between structure, soil and input motions.

This study presents information on the design procedure of seismic base isolation systems. Analysis of the seismic responses of isolated structures, which is oriented to give a clear understanding of the effect of base isolation on the nature of the structure / and discussion of various isolator types are involved in this work. Seismic isolation consists essentially of the installation of mechanisms, which decouple the structure, and its contents, from potentially damaging earthquake induced ground motions. This decoupling is achieved by increasing the horizontal flexibility of the system, together with providing appropriate damping. The isolator increases the natural period of the overall structure and hence decreases its acceleration response to earthquake-generated vibrations. This increase in period,together with damping, can reduce the effect of the earthquakes, so that smaller loads and deformations are imposed on the structure and its components. The key references that are used in this study are the related chapters of FEMA and IBC2000 codes for seismic isolated structures. In this work, these codes are used for the design examples of elastomeric bearings. Furthermore, the internal forces develop in the superstructure during a ground motion is determined / and the different approaches defined by the codes towards the &lsquo / scaling factor&rsquo / concept is compared in this perspective.

<p>Seismic isolation is a seismic design philosophy that aims to reduce the demand on structures as opposed to increasing their capacity to endure forces. Seismic isolation can be achieved by placing isolating bearings with relatively low stiffness compared to the structure itself beneath the superstructure. This low stiffness layer increases the structural period, shifting the structure into a period range of low seismic energy content.</p> <p>The objectives of this research were to investigate the dynamic properties, durability and limitations of stable unbonded fibre reinforced elastomeric isolator (SU-FREI) bearings. Vertical compression testing indicated the bearings possessed adequate vertical stiffness. Due to lack of bonding at the bearing interface surfaces rollover deformation was observed to occur during lateral cyclic testing. This response behaviour was found to result in advantageous effective lateral stiffness and damping properties. The bearings maintained stability during rollout testing while serviceability and fatigue testing both conformed to code specified test specimen adequacy limitations. Experimental shake table testing showed that the isolated structure behaved essentially as a rigid body during testing. Test results showed that a SU‐FREI isolation system significantly reduced the seismic demand on the structure.</p> <p>Modelling of the bearings dynamic properties was completed using a bilinear model and a backbone curve model. Both models showed adequate results in predicting experimental peak responses. A simplified design spectrum analysis was presented and used to model the structure in four Canadian cities. This design spectrum analysis approach showed adequate capabilities in predicting peak response values, such that the method could be used in preliminary analysis and design of isolated structures.</p> / Master of Applied Science (MASc)

Sliding isolation bearings are used widely around the world to minimize damage to structures and their contents during earthquakes. Past studies have typically focused on the behavior of sliding isolation bearing under design conditions; however, as the performance-based earthquake engineering advances, it is necessary and critical to understand the ultimate or even failure behavior, of structural systems under extreme conditions. Using a double friction pendulum bearing with non-articulated slider as an example, this thesis comprehensively investigates the extreme behavior of the sliding bearing components as well as steel frame buildings isolated using these bearings. This thesis is comprised of two major parts. The first includes numerical and experimental studies of double friction pendulum bearings at the component-level. Finite element investigation shows that depending on the superstructure mass there are two major failure modes for the double friction pendulum bearings. When the superstructure mass is sufficiently large, the failure mode is dominated by the restraining rim yielding; however, when the mass is relatively small, its failure mode shifts to bearing uplift. A simplified analytical model which can directly simulate the impact and uplift behavior of double friction pendulum bearing is also implemented, comparing well to the finite element analysis. Then, to validate the ability of the models to predict extreme behavior as well as to investigate the effect of the restraining rim design, which varies around the world, an experimental study was carried out. Uplift behavior and significant rim yielding were observed during the shake table tests. Moreover, other response parameters, including uplift and shear forces, are evaluated and compared among different rim designs. It is found the restraining rim design has a substantial influence on the bearing’s extreme behavior. The second part of the thesis investigates the system-level behavior of steel frame buildings isolated with double friction pendulum bearings. It is found that the stiffness of the superstructure largely dictates the system-level failure modes and collapse probability. Initially, bearings with rigid restraining rims are investigated. For flexible moment-resisting frames, the system-level failure modes are mixed: both the bearing uplift and superstructure yielding contribute; also, using current code-minimum design results in acceptably low probability of collapse. However, for stiff concentrically-braced frames, the impact force can impose large ductility demands on the superstructure regardless of its strength. As a result, the system-level failure comes exclusively from superstructure yielding, and only by increasing bearing’s displacement capacity beyond the minimum code allowed can the design meet as acceptably low collapse probability. When flat rims are used instead for the bearing design, the failure modes for both building types are exclusively bearing failure. Furthermore, while it is more apparent for concentrically-braced frames, using flat rims for the bearings can reduce the collapse probability compared to using rigid rims. / Thesis / Doctor of Philosophy (PhD)

[pt] O controle passivo de vibrações em edifícios usando absorsores pendulares tem sido bastante estudado na literatura técnica e usado na pratica em edifícios altos como o Taipei-101 em Taiwan. Como a frequência do pêndulo depende apenas do seu comprimento e da aceleração da gravidade, para sintonizar a frequência do pêndulo com a do edifício, tem-se como única variável de projeto o comprimento do pêndulo. Entretanto, em muitos casos, o comprimento necessário e o espaço requerido não se coadunam com o projeto. Nestes casos pode-se substituir o pêndulo clássico por um sistema pendular equivalente composto por uma massa que se movimenta sobre uma superfície curva, permitindo maior flexibilidade no projeto do absorsor, já que o comprimento do pêndulo torna-se irrelevante e a forma da superfície curva pode ser otimizada. Em virtude do movimento da massa sobre a superfície curva, novas forças de inércia e amortecimento não encontradas no pêndulo clássico podem aparecer. No presente trabalho um sistema pendular composto de uma massa que se desloca através de suportes rolantes sobre uma superfície curva é proposto para controle das oscilações de estruturas sob excitação de base. Este sistema pendular tem a vantagem de poder ser usado tanto como um amortecedor pendular de massa sintonizada (APMS) quanto como isolador de base pendular (IBP). Como o sistema pendular pode, em certos casos, apresentar grandes rotações, barreiras que limitam o movimento são propostas, gerando forças de impacto cuja eficiência no controle de vibrações é aqui investigada. / [en] The passive vibration control of buildings using pendulum absorber has been extensively studied in the technical literature and used in high buildings such as the Taipei-101 in Taiwan. Since the frequency of the pendulum depends only on its length and the acceleration of gravity, to tune the frequency of the pendulum to that of the building, its length is the sole design variable. However, in many cases, the pendulum length and the space required for its installation are not consistent with the design. In these cases one can replace the classic pendulum with an equivalent pendulum system comprising a mass that moves on a curved surface, allowing greater flexibility in the absorber design as the length of pendulum becomes irrelevant and the shape of the curved surface can be optimized. Because of the mass movement on the curved surface, new inertia and stiffness forces not found in the classic pendulum may appear. In the present work a pendulum system comprising a mass that moves through rolling bearings on a curved surface is proposed for control of the oscillations of structures under base excitation. This pendulum system has the advantage of being used both as a pendulum tuned mass damper (APMS) and as a base isolation pendulum system (IBP). As the pendulum system can, in certain cases, display large rotations, barriers which limit its movement are proposed, generating impact forces whose efficiency in vibration control is here investigated.