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1
Ozkaya, Cenan. "Development Of A New Seismic Isolator Named." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612712/index.pdf.
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The experimental research presented in this dissertation aims to develop a new rubber&ndashbased seismic isolator type on the basis of the idea that the damping of a conventional annular elastomeric bearing (EB) can be increased by filling its central core with small diameter steel balls, which dissipate energy via friction inside the confined hole of the bearing during their movements under horizontal loads. The proposed bearing type is called &ldquo
Ball Rubber Bearing (BRB)&rdquo
. A large set of BRBs with different geometrical and material properties are manufactured and tested under reversed cyclic horizontal loading at different vertical compressive load levels. Effect of supplementary confinement in the central hole of the bearing to performance of BRB is studied by performing some additional tests. Test results are used to develop design equations for BRB. A detailed non-linear finite element model is developed to verify the test results. The proposed analytical model is determined to simulate the structural hysteretic behaviour of the bearings. In design of BRBs, the proposed design guideline can be used in conjunction with the proposed non-linear finite element analysis. Extensive test results indicate that steel balls do not only increase the energy dissipation capacity of the elastomeric bearing (EB) but also increase its horizontal and vertical stiffness. It is also observed that the energy dissipation capacity of a BRB does not degrade as the number of loading cycles increases, which indicates remarkably reliable seismic performance.
2
Ismail, Mohd. "Shock isolation systems incorporating Coulomb friction." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/348953/.
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This study investigates a novel approach to the problem of shock isolation. The questions considered are whether friction produces a better performance in terms of reduced response during a shock compared to viscous damping and a lower residual response after the shock. To gain physical insight, a single degree of freedom model with friction applied to the isolated mass is analysed. It serves as a benchmark to the performance of a two degree of freedom model where friction is applied to a secondary mass. The isolation system performance is then quantified. For the two degree of freedom system with an intermediate secondary spring which connects the primary and secondary mass, it is possible to obtain the reduction in the displacement response as good as the single degree of freedom system and at the same time smoother acceleration response compared to the single degree of freedom system. For the purpose of further improvement, a control strategy is introduced to switch on and off friction in both models depending on some response parameters and this is compared to the passive systems. This is the semi active control strategy where friction is changed within a cycle of vibration (discontinuous). The control strategy provides more displacement reduction to ensure the maximum displacement response is much smaller than the base input which cannot be obtained with the passive systems. The practical implementation and experimental validation is presented only for the first stage of the response during the shock. For the practical implementation of the switchable friction, an electromagnet is applied to separate the friction surfaces. Good agreement with the simple theoretical models for both passive and switchable systems is obtained. The reduced displacement and smooth acceleration response were obtained from the experiments with the system used to represent the two degree of freedom model. The issues and limitations in the practical implementation are identified and discussed.
3
Jamali, Navid [Verfasser]. "On the numerical simulation of friction isolated structures / by Navid Jamali." Wuppertal : Inst. für Konstruktiven Ingenieurbau, 2008. http://d-nb.info/1000817172/34.
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4
Iliadis, Charalampos. "Friction-based control system for seismic energy dissipation with isolated stories." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66834.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 37-38).
The implementation of various structural control systems, such as passive, semi-active or active is not a new concept. They are incorporated in structures to increase the performance under seismic and/or wind loading either by adding stiffness or inducing counteracting forces which dissipate energy in various ways. In order to efficiently dissipate the seismic energy with existing schemes, large structural displacements are required. However, structures that are most vulnerable to earthquakes such as low-rise relatively stiff buildings, cannot experience significant displacements. Therein lies the challenge the author attempts to address by proposing a structural scheme which can be applied to low-rise concrete buildings to efficiently dissipate seismic energy and at the same time to considerably decrease the forces in the structural members for a given seismic excitation. In this thesis the design of this new structural scheme is described and a case study is performed in order to demonstrate its effectiveness and applicability.
by Charalampos Iliadis.
M.Eng.
5
Lodato, Alessio. "Analisi dell’affidabilità sismica delle strutture isolate mediante dispositivi Friction Pendulum Bearings System." Doctoral thesis, Universita degli studi di Salerno, 2016. http://hdl.handle.net/10556/2467.
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2014 - 2015The thesis investigates the seismic reliability of isolated structures with FPBs (Friction Pendulum Bearings) towards failure due to high vertical component excitation and friction coefficient variations. In the end, it has been studied the influence of the uncertainty of the input excitation on the vulnerability of complex structures such as viaducts in the case of different seismic isolation strategies application. The last seismic events (Christchurch 2011, L’Aquila 2009) have highlighted lacks in the actual design philosophies (PBD) due to the high structural damage experimented by structures. The Passive Control Technique of seismic response allows high structural performances respect to the one of fixed base structures, in this way making sustainable the repairing costs of structures in the case of medium high intensity seismic event. After introducing a rich bibliography on matemathical theory of base isolated structures, with some remarks on the state space formulation which allow to carry out modal analysis of non classically damped structures such as the one object of the study, on the mechanical and dynamical behavior of Friction Pendulum System device and on the current Technical Code in Italy (NTC08), it has been introduced the theme to be investigated. Being the FPS behavior related to the friction force, the seismic response can be affected by particular seismic event as near fault event characterized by high vertical component intensity of seismic excitation. Moreover the degradation of the sliding interface due to velocity, pressure and temperature variations can influence the seismic response of the device. To the scope of investigating the collapse phenomenon of the device, non linear dynamic analysis have been carried out through deterministic parametric methods with different near fault input excitations, on two different systems: the first described by a rigid superstructure and isolation system described by the Nagarajaiah model (1990), the second representative of a benchmark r.c. building of four levels (Almazan 2003). The subsequent stochastic analysis carried out by means of the use of Montecarlo simulation, taking advantage of the inversion method, on a system described by rigid superstructure and isolation system described by a rigid-plastic behavior with hardening, have highlighted the relation between the stochastic response and the uncertainty of the friction coefficient in the case of sinusoidal excitation. Finally, it has been investigated the vulnerability of bridge structures in different isolation system design configurations by using fragility analysis, carried out taking advantage of the Multi Stripes method (Baker 2014). Results show the probability of exceedance of the limit state considered variations taking into account the uncertainty of the input excitation. [edited by author]
Il lavoro di tesi ha indagato l’affidabilità sismica delle strutture isolate mediante dispositivi FPBs (Friction Pendulum Bearings) nei confronti dei fenomeni dello scalottamento e delle variazioni del coefficiente d’attrito che caratterizza l’interfaccia di scorrimento del dispositivo. In ultima analisi, è stata indagata l’influenza dell’aleatorietà dell’input in ingresso sulla vulnerabilità di strutture complesse quali viadotti nel caso di applicazione di differenti strategie di isolamento. Gli ultimi eventi sismici (Christchurch 2011, L’Aquila 2009) hanno evidenziato carenze nelle filosofie prestazionali attuali (PBD) a causa dell’elevato danneggiamento agli elementi strutturali sperimentato dalle costruzioni. Le tecniche di controllo passivo della risposta sismica consentono elevate prestazioni in termini di performance strutturali rispetto a quelle a base fissa, in tal modo rendendo sostenibili i costi di riparazione delle costruzioni in caso di eventi sismici di medio alta intensità. Dopo una ricca bibliografia sulla teoria matematica alla base delle strutture isolate, con cenni alla formulazione nello spazio degli stati che consente l’analisi modale di strutture non classicamente smorzate, sul comportamento meccanico e dinamico del dispositivo Friction Pendulum System e sulle attuali Norme Vigenti in Italia (NTC08), si è introdotta la problematica oggetto di studio. Essendo il comportamento del dispositivo FPS dipendente dalla forza d’attrito, la risposta sismica può essere affetta da particolari eventi sismici di tipo near fault caratterizzati da componenti verticali dell’eccitazione sismica di elevata intensità. Inoltre l’usura della superficie di scorrimento dovuta a variazioni di velocità, pressione e temperatura può influenzare la risposta sismica del dispositivo. Al fine di indagare il fenomeno dello scalottamento del dispositivo sono state condotte analisi dinamiche non lineari mediante metodologie deterministiche parametriche con differenti eccitazioni in ingresso di tipo near fault, su un sistema descritto da una sovrastruttura rigida e sistema di isolamento descritto dal modello di Nagarajaiah (1990), e su un sistema rappresentativo di un edificio benchmark in c.a. a 4 livelli (Almazan 2003). Inoltre, le successive analisi stocastiche condotte mediante l’utilizzo della simulazione Montecarlo, sfruttando il metodo dell’inversione, su un sistema descritto da sovrastruttura rigida e sistema di isolamento descritto da una legge attritiva rigido plastica con incrudimento, hanno messo in evidenza la dipendenza della risposta stocastica dall’aleatorietà del coefficiente d’attrito nei confronti di eccitazioni sinusoidali. Infine è stata indagata la vulnerabilità di strutture da ponte in differenti configurazioni di progetto del sistema di isolamento mediante analisi di fragilità condotte sfruttando il metodo Multi Stripes (Baker 2014). Esse mostrano le variazioni nella probabilità di superamento degli stati limite in considerazione dell’aleatorietà dell’input in ingresso. [a cura dell'autore]
XIV n.s.
6
Boral, Caner. "Desing Of An Engine Mount With Dry Friction Damping." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12612132/index.pdf.
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Automotive engine mounts are used to support engine weight, protect engine from road inputs and isolate transmission of vibrations created by the engine, which has a drastic effect on the noise generated inside the passenger cabin. Most common types of engine mounts are elastomeric and hydraulic mounts, the former having better vibration isolation characteristics whereas the latter displays better shock isolation. Elastomeric mounts are widely used for their low initial cost, while hydraulic mounts with inertia track and decoupler are chosen for their good vibration isolation and shock excitation characteristics. However, hydraulic mounts with inertia track and decoupler are not appropriate for small segment and commercial vehicles due their high initial cost. In this thesis, the effect of the addition of a dry friction damper on the performance of elastomeric automobile engine mounts is investigated. Friction dampers are used to attenuate vibration amplitudes in many applications such as gas turbine engines, railway vehicles, space structures and civil buildings. In this study, a friction element is added to the engine mount at its axial direction and its effect is studied. Results show that, the addition of dry friction damping to the original system increases vibration isolation performance significantly at low frequencieswhereas, due to the increased stiffness of the system, at high frequencies dry friction damper has a mitigating effect on performance. In order to overcome this problem, original system parameters are modified. In the modified system a softer mount that increase vibration isolation performance at high frequencies
but, which might cause excessive static deflection due to reduced stiffness of the system is used. On the other hand, addition of dry friction damping prevents excessive static deflections due to the increased stiffness effect and also increases the performance at high frequencies due to the soft mount. Final results showed that vibration isolation performance at low frequencies increases considerably while vibration isolation performance at high frequency is similar and even slightly better than the original system with addition of dry friction damping.
7
Mastricola, Nicholas Palma. "Nonlinear Stiffness and Edge Friction Characterization of Coned Disk Springs." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480346443676492.
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8
Dupeux, Guillaume. "Propulsion et friction d'objets non mouillants." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://pastel.archives-ouvertes.fr/pastel-00954334.
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Nous nous intéressons aux dynamiques spéciales engendrées par des objets non mouillants. Sur un substrat recouvert de rainures asymétriques en dents de scie, un liquide ou un solide en caléfaction est propulsé horizontalement. Les motifs rectifient l'écoulement de vapeur dans une direction privilégiée et le mobile est entrainé par viscosité. Sur un substrat lisse, si le solide est lui-même asymétrique, la répartition non homogène de masse incline la surface inférieure et avec elle la force de pression de l'écoulement de vapeur : sa composante horizontale met aussi l'objet en mouvement. Une goutte caléfiée entre deux plans parallèles montre également un comportement surprenant : au-delà d'un rayon critique, elle se déstabilise en formant un anneau qui s'agrandit et éclate en petits fragments. La grande mobilité de ces objets pose la question de la friction qu'ils subissent. Très faible sur un substrat lisse, on observe une dissipation inertielle dans l'air environnant et dans une couche limite liquide pour les gouttes. En revanche, sur un substrat crénelé, elle est fortement amplifiée par l'impact du liquide sur les textures. Pour terminer, nous nous intéressons à divers objets non mouillants naturels : l'argyronète aquatique et plusieurs plantes aquatiques superhydrophobes. Le premier est une araignée qui passe sa vie sous l'eau. Elle s'abrite dans une grande bulle d'air qu'elle crée en capturant, par un mouvement dynamique de son abdomen superhydrophobe et de ses pattes, de petites bulles à la surface de l'eau. Quant aux seconds, ils utilisent leurs surfaces non mouillantes pour survivre lors d'une immersion.
9
Thaijaroen, Woothichai. "Nonlinear dynamic modelling of rubber isolators using six parameters based on parabolic spring, springpot, and smooth-slip friction element." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492630.
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A time-domain six-parameter model is adopted to simulate the vibration behaviour of various rubber-isolators at constant temperature and preload over the frequency range of 0.05-25 Hz. The model consists of three components based on a nonlinear parabolic spring, a fractional-derivative-based springpot, and a smooth-slip friction element. The adopted mode working in one-dimensional manner is capable of generating force as a function of displacement.
10
Dueñas, Osorio Leonardo Augusto 1976. "Optimization of base isolation systems using low-cost bearings and frictional devices." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84275.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Vita.
Includes bibliographical references (leaves 52-53).
by Leonardo Augusto Dueñas Osorio.
M.Eng.
11
Han, Mengyu. "Application of Base Isolation Systems to Reinforced Concrete Frame Buildings." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35722.
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Seismic isolation systems are widely used to protect reinforced concrete (RC) structures against the effects of strong ground motions. After a magnitude 6.6 earthquake, the outpatient building of Lushan People’s hospital in China remained in good condition due to the seismic isolation technology, while the non-isolated older outpatient building nearby experienced major damage. The building provides a good opportunity to study and assess the contribution of isolation systems to seismic performance of RC structures. In the current research project, the isolated outpatient building was modelled and analyzed using computer software SAP2000. The post-yield behaviour of the structure was modelled by assigning multi-linear plastic links to frame objects. The rubber isolators were represented by rubber isolator link elements, assigned as a single joint element between the ground and the superstructure. The isolated structure was subjected to four earthquake records with increasing intensity. The performances of the isolated structure were compared with those of the fixed-base structures in terms of lateral inter-storey drifts, peak absolute floor accelerations, and residual drifts. The laminated rubber bearings, the high damping isolation devices, composed of rubber bearings and viscous dampers, and the hybrid isolation system of rubber bearings and friction pendulum bearings were analysed. The effectiveness of the three base isolation systems considered in enhancing structural performance was investigated. The results show the level of improvement attained in seismic response by each system. They also illustrate that the rubber bearings coupled with friction pendulum bearings produce the best drift control without causing excessive horizontal displacements at the base level and without adversely affecting floor accelerations.
12
Agarwal, Vivek Kumar. "Pounding and impact of base isolated buildings due to earthquakes." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/2217.
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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.
13
Marrs, Nicholas Reidar. "Seismic Performance Comparison of a Fixed-Base versus a Base-Isolated Office Building." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1004.
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The topic of this thesis is base isolation. The purpose of this thesis is to offer a relative understanding of the seismic performance enhancements that a typical 12-story steel office building can achieve through the implementation of base isolation technology. To reach this understanding, the structures of a fixed-base office building and a base-isolated office building of similar size and layout are designed, their seismic performance is compared, and a cost-benefit analysis is completed. The base isolation system that is utilized is composed of Triple Friction Pendulum (TFP) bearings.
The work of this thesis is divided into four phases. First, in the building selection phase, the structural systems (SMF and SCBF), layout, location (San Diego, CA), and design parameters of the buildings are selected. Then, in the design phase, each structure is designed using modal response spectrum analysis in ETABS. In the analysis phase, nonlinear time history analyses at DBE and MCE levels are conducted in PERFORM-3D to obtain the related floor accelerations and interstory drifts. Finally, in the performance assessment phase, probable damage costs are computed using fragility curves and FEMA P-58 methodology in PACT. Damage costs are computed for each building and seismic demand level and the results are compared.
14
Eroz, Murat. "Advanced models for sliding seismic isolation and applications for typical multi-span highway bridges." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19709.
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Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.Committee Chair: DesRoches, Reginald; Committee Member: Goodno, Barry; Committee Member: Jacobs, Laurence; Committee Member: Streator, Jeffrey; Committee Member: White, Donald.
15
Srinivasan, Vijay. "Mobility Analysis of Structure-borne Noise Paths in a Simplified Rotorcraft Gearbox System." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276884944.
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Chiriatti, Léon. "Etude de l'adhérence armature-béton, influence des granulats de béton recyclé et apport des mesures acoustiques." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAD040/document.
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L'introduction de granulats de béton recyclé (i.e. granulats produits à partir des gravats issus de la démolition d'ouvrages en béton obsolètes) dans les formulations de béton impacte de manière significative le comportement structurel des éléments en béton armé. Ce travail est consacré à l'étude de l'influence des granulats de béton recyclé sur l'adhérence armature-béton. Dans un premier temps, un modèle analytique de l'adhérence armature-béton est développé. L'originalité du modèle proposé réside dans le nombre limité de paramètres physiques sur lesquels il est fondé. Ces paramètres physiques sont ensuite déterminés expérimentalement via la réalisation d'une campagne d'essais d'arrachement. Trois types de bétons, dont deux bétons de granulats de béton recyclé, sont étudiés. Le suivi de l'arrachement de l'armature est complété par des mesures acoustiques permettant d'obtenir des informations provenant du coeur de l'échantillon, où l'armature se trouveThe use of recycled concrete aggregate (i.e. aggregate produced from concrete demolition rubble) has a significant impact on the mechanical behavior of reinforced concrete members. This work focuses on the influence of recycled concrete aggregate on rebar-concrete bond. First, an analytical madel of the rebar-concrete bond is developed. The original feature of this modellies in the limited number of non-free physically-based parameters on which it is based. These parameters are then experimentally determined through a pull out test campaign. Three types of concrete, including two recycled aggregate concretes, are studied. Pull-out test monitoring is completed by acoustic measurements in order to obtain data from inside the concrete bulk, where the reinforcing bar is located
17
Dung, Pei-Yi, and 董佩宜. "Isolated Bridges Using Polynomial Friction Pendulum Isolator." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/50894709471063959800.
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碩士國立中央大學
土木工程研究所
98
Conventional sliding isolators may be effective when the structures are subjected to far-field ground motions, but it may not be effective when the structures are subjected to near-field ground motions because the pulse periods of the near-field ground motions are usually close to the isolation periods of the isolators, and it may lead isolated structures to resonate with the ground motions. In order to improve the performance of seismic isolation under near-field ground motions, a various frequency isolator which is named Polynomial Friction Pendulum System (PFPI) is used in this study. The sliding surface of PFPI consists of six-order polynomial. The restoring stiffness possesses two sections: softening section and hardening section. The structural acceleration response can be reduced by decreasing the restoring stiffness, while the structural displacement response can be reduced by increasing the restoring stiffness of PFPI. Both theoretical and experimental studies were carried out in this thesis which includes: (1) A shaking table test for simplified isolated bridge model by using PFPI; (2) find out the optimal parameters of PFPI by using PSO-SA hybrid algorithm; (3) compare the isolation effectiveness between PFPI and Friction Pendulum System (FPS). The results show that PFPI has better performance than FPS. Because the multi-function of PFPI (softening section and hardening section), it offers us different choices to do a design.
18
WONG, PEI-SYUAN, and 汪沛玄. "Development of Polynomial and Conical Friction Pendulum Isolator system." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/t2py7r.
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碩士國立高雄科技大學
營建工程系
107
Countries in the earthquake zone often face earthquake problems from an client to modern times. With the rapid development of technology, the seismic technology is also changing with each passing day. The traditional single pendulum isolation is a widely used sliding type isolation with good isolation effect on general seismic waves, but low frequency resonance phenomenon still prone to happen under the long-period near-field fault seismic wave, which leads to the effect reduction. Inherent scholars have proposed Polynomial Friction Pendulum Isolation(PFPI) with variable curvature surface. Since isolation frequency of PFPI nonstationary, therefore this type of support can avoid the phenomenon of resonance with the near-field seismic wave. However, the sliding surface of the curved disc is divided into two performance stages softening section and hardening section according to recovery stiffness. The generation of structural acceleration is reduced, and the hardened section suppresses the bearing displacement, which causes the PFPI to rise sharply at the end of the hardening section to achieve the effect of suppressing the bearing displacement, simultaneously sacrifices the ability to suppress the structural acceleration and causes its acceleration rise on the contrary. This study intends to combine PFPI with Conical Friction Pendulum Isolator(CFPI) to develop a Polynomial and Conical Friction Pendulum Isolator(PCFPI) to improve the effect of the structural acceleration caused by the hardening of the PFPI hardening section, the effective restraining of the bearing displacement and the acceleration response of the upper structure are simultaneously achieved. Based on the theoretical formula, the theoretical and numerical analysis of the isolation effect of the near-field seismic wave is discussed. It can restrain the bearing displacement and reduce the acceleration response of the superstructure in addition. The theoretical formula is used to investigate the isolation effect of this theory and numerical analysis on the near-field seismic wave. With the discussion within energy dissipation effect of the Multi-functional Friction Damper (MFD) added to the two-stage start-up mechanism in the near-field seismic wave.
19
HUANG, DUN-BO, and 黃敦博. "Application of resilient-friction base isolator (R-FBI) upon bridges." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/32035936434067677577.
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Fang, Yen-chen, and 方嬿甄. "Analysis and Design of Polynomial Friction Pendulum Isolator with Vertical Effect." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/67541361067605776815.
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碩士國立中央大學
土木工程研究所
99
The sliding surface of Polynomial Friction Pendulum Isolator (PFPI) is defined by a sixth-order polynomial function. The restoring force possesses a softening section and a hardening section. In the softening section, the restoring stiffness is decreasing in order to mitigate the structural acceleration response, while in the hardening section, the restoring stiffness is increasing so as to reduce the isolator drift. It has been proven that PFPI is not only able to effectively mitigate the structural seismic response induced by either long period near-fault earthquakes or far-field earthquakes. However, if the PFPI surface curvature increasing rapidly, it may induce severe structural vertical response. For the purpose of simulating horizontal and vertical responses of the bridge with PFPI, the derivation of analysis method considering horizontal and vertical degree of freedom is developed in this study. Discussion on effects of considering vertical ground excitation and the nonlinear behavior of piers. Moreover, optimal parameter study of PFPI and Friction Pendulum System (FPS) and comparison the effectiveness between PFPI and FPS. The results show that the derivation of analysis method developed in this study does indeed simulates horizontal and vertical structural seismic responses. Moreover, PFPI is more effective to reduce structural seismic response than FPS.
21
Lu, Bao-Jyun, and 陸寶軍. "Optimal Coefficient Friction Design Formulas Considering Characteristics of Different Site and Theoretical Analysis of Polynomial Friction Pendulum Isolator with Bidirectional Experiment." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/03305668374120110835.
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碩士國立交通大學
土木工程系所
104
There are two parts of study in this paper. The first part is about the design formulas for the optimal coefficient of friction which considers the characteristics of different sites. The second part is about the Polynomial Friction Pendulum Isolators, including experiment on the shaking table, and the theory of bidirectional numerical analysis. The first part aims at the optimal coefficient of friction for the Friction Pendulum System. First of all, the motion equation was transformed into state space equation. Then we could obtain the state space equation in discrete-time system for dynamic analysis. Due to the literature of the optimal coefficient of friction for the FPS being analyzed under white noise, it did not consider the characteristics of different sites in Taiwan, so this paper used 177 records of earthquakes in Taiwan as input. After that, considered the structure system in rigid and non-rigid system with varying structure parameters. And the mean square of absolute structural acceleration had been minimized for obtaining the optimal coefficient of friction. Repeating the optimal process with various structural parameters, the proposed simple design formula was developed by regression of those optimal coefficient of friction from numerical simulations. Finally, we conducted the case analysis to verify the feasibility of the proposed optimal design formulas. The second part is Polynomial Friction Pendulum Isolators, including experiment on the shaking table, and the theory of numerical analysis in bidirection. According to the literature, when the FPS is subjected to low-frequency seismic wave, the FPS might lost its effectiveness. For this reason, some scholars invented the Polynomial Friction Pendulum Isolators (PFPI) for improving this problem. In order to prove the effectiveness of PFPI, there was an experiment about sliding isolation systems using PFPI and FPS as isolators to compare the PFPI and FPS. The restoring stiffness of PFPI is variable. Due to this, in different position of isolators, PFPI can reduce the structural acceleration or suppress the isolator drift. A lot of analysis about isolation is unidirectional, but the earthquake is not only in one direction, so this paper derived the theory of numerical analysis in bidirection and checked its accuracy by the result of the shaking table tests. Comparing numerical analysis in unidirection and bidirection, the results showed us two things, one thing is that unidirectional simulation can be used to analyze the structural acceleration in particular position of isolators, another thing is that drift of isolators must be analyzed by bidirectional simulation.
22
Wang, Xi. "Study on friction base isolators." Thesis, 1991. http://spectrum.library.concordia.ca/4353/1/MM64760.pdf.
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vy, pham duong uyen, and 潘葉桐. "ANALYTICAL STUDY ON BRIDGES WITH POLYNOMIAL FRICTION PENDULUM ISOLATORs." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6v5t2q.
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碩士國立中央大學
土木工程學系
107
ABSTRACT A conventional isolation system with constant isolation frequency such as FPS is usually a long-period dynamic system. However, this system has limitation due to constant isolator period and restoring force characteristics. This lead its seismic response is likely to be amplified in the earthquake with long-period wave components. A new isolator called the polynomial friction pendulum isolator (PFPI) that overcomes these limitations while retaining all the advantages has been described in this thesis. The PFPI has oscillation frequency decreasing with sliding displacement, and the restoring force has an upper bound so that the force transmitted to the structure is limited. A PFPI consists of a slider and a concave and axially symmetrical sliding surface which is defined by a six-order polynomial function. Nowadays, the analytical models proposed for a SIVC isolator were usually derived by using static equilibrium condition. This kind of models (also called simplified model) is not able to account for dynamic coupling effects between each vibration direction as well as the curvature effect such as centrifugal force. As a result, these models will lose their accuracy when the isolators are subjected to extreme earthquakes that produce large velocity or displacement. In addition, most of the existing models did not consider the effect the vertical ground motion on the isolation performance. In order to solve that problem, this thesis establish another analytical for the bearing and consider the effect of vertical ground motions. In addition, it also investigates the dynamic coupling effects on the isolator performance. Keywords: Variable curvature, sliding isolation, tri-axial ground motion, coupling effect.
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Jen, Wan-chun, and 任萬鈞. "The study of Friction Pendulum Bearing in Bridge Isolation." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/70000254745129182770.
Full textAbstract:
碩士國立中央大學
土木工程學系
86
The feasibility of using friction pendulum bearings(FPS) combined with the enhanced energy dissipation device system which consists of linear fluid dampers and relatively rigid linking numbers with leverage for seismic isolation of bridges is proposed in the present studies. Accordingly, an algorithm referred to as the〝multi-support shear balance method〞is used for the nonlinear dynamic analysis of bridges isolated with multiple sliding bearing. The dynamic responses of bridges with / without this systems, subject to strong ground motions, are computed numerically. The EL Centro earthquake, Kobe earthquake, Mexico earthquake and simulated Taipei Basin earthquake are used as excitations. It is found that not only the maximum relative displacement (of superstructure) but also the maximum base shear (of piers) can be reduced significantly when these devices are installed on the bridge.
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Wang, Sheng-Hsuan, and 王勝宣. "Optimal Design Procedures for Isolation Systems and Bidirectional Experiment on Friction Pendulum Isolation System." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/42675530296446156780.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
103
In the conventional isolation design procedures, the energy dissipation parameters, like equivalent damping ratio and friction coefficient, are not determined by some certain criteria but engineers’ pratical experience. Therefore, we attempted to integrate the optimal formula of dissipation parameters into the conventional design procedures called optimal design procedures, and chose a real case to do the time history analysis and then discussed the feasibility of optimal design procedures. Three earthquake types were utilized as input, one was the design earthquake, another was a non-design earthquake with PGA which was 1.5 times the design earthquake, the other was a near-fault earthquake. According to the analysis results, if the case utilized elastomeric isolators designed by optimal damping ratio design procedures, the isolation system could play a good result about isolation effect and displacement regardless of the types of input. If the case utilized friction pendulum system designed by optimal friction coefficient design procedures, the isolation displacement will be greater than the design displacement. For this reason, we tried to modify the logic of optimal friction coefficient design procedures, in order to obtain the required friction coefficient which would satisfy the demand of the non-design earthquake. Because the difference between the optimal design procedures and the conventional one is insignificant, engineers will feel comfortable to adopt the optimal design procedures. The optimal dissipation parameters formula will be the criteria in deciding the damping ratio and friction coefficient. In the previous researches about simulating bidirectional response of friction pendulum system, the isolation model was directly simplified without any verification. Therefore, we tried to verify the simplication through the mathematical derivation and experimental data, and then utilized the simplified model to simulate the unidirectional and bidirectional response. The comparison between experimental data and simulation results was conducted. On the basis of the comparison results, we firmly believe that the simplified isolation model is reliable. Finally, The comparison between unidirectional and bidirectional simulation was also executed, and then the advantage of bidirectional simulation is obvious.
26
Cheng, Yu-Fang, and 鄭伃芳. "Multi-functional Friction Damper for the Analysis of Isolation Systems." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/vbg3rx.
Full textAbstract:
碩士國立高雄科技大學
營建工程系
107
In the present empirical study, the traditional sliding isolation system has excellent isolation effect for far-field waves. On the other hand, the isolator displacement can be considerably enlarged in near-fault waves due to the long-period velocity pulse possessed in the near-fault waves. As a result, it may lead to a resonant motion that can reduce the effectiveness and safety of isolation. In order to improve the performance of the isolation system in near-fault waves,therefore, in this study, a multi-functional friction damper with two sets of activation mechanisms is added to the isolation system. After the numerical simulations and parameter analysis,the research shows that the isolation system with multi-function friction damper is beneficial to reduce the isolator displacement and structural acceleration under the near-fault waves. It can be proved that the addition of the multi-functional friction damper has good isolation effect in the isolation system.
27
Pall, Rashmi. "Study on friction base isolators for seismic control of low-rise buildings." Thesis, 1993. http://spectrum.library.concordia.ca/4354/1/MM90913.pdf.
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Chi-Fung, Chang, and 張豈凡. "Dynamic Analysis of Frictional Isolation Structures." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/39524097590415428576.
Full text
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Lin, Chen-Yu, and 林震宇. "Shaking Table Test and Analysis of a Controllable Friction Isolation System." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/10918096651994071624.
Full textAbstract:
碩士國立高雄第一科技大學
營建工程所
97
Base isolation technology is an effective earthquake resistance technique, since it can be used for protecting both the structural system and the internal equipment. Nevertheless, recent studies have revealed that an isolation system may induce an excessive response when subjected to a near-fault earthquake that contains a long-period pulse waveform. In order to improve isolation efficiency in near-fault earthquakes, a semi-active sliding isolation system called Piezoelectric Smart Isolation System (PSIS), which consists of a sliding isolation system and a semi-active piezoelectric friction damper, is proposed in this study. The semi-active damper functions as a supplementary energy dissipating device for the isolation system. Because of its low energy demand and quick response, a piezoelectric actuator was chosen as the control device for regulating the clamping force of the semi-active friction damper. In this thesis, both theoretical and experimental investigations were conducted for the proposed PSIS isolation system. Three kinds of control laws were employed to control the PSIS. These control laws are: (1) Seim-active optimal control (semi-LQR), (2) Non-sticking friction control (NSF), (3) Fuzzy friction controller. The test results show that the PSIS with NSF (��=20) or Fuzzy (rule=15555) controller has the best isolation efficiency and requires the less sensors. The test results also demonstrate that the dynamic responses of the PSIS with different kinds of the control laws are very consistent with the theoretical ones obtained from numerical simulation. This verifies the feasibility and efficiency of the PSIS system.
30
WEN-CHING, WANG, and 王文清. "Dynamic Behavior of Frictional Base Isolation Structures." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/21055762529198838273.
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Hsieh, Cheng-Hsin, and 謝姃馨. "Analytic Study on Nonlinear Rolling Isolation System with Viscous or Friction Damper." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/50273913944892375618.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
98
Abstract The vibration period of many linear isolation systems are 2 to 3 seconds which is close to the predominant period of near-fault earthquake, and resonance may occur. For this reason, nonlinear isolation systems are developed to avoid resonance. The frequency of nonlinear isolation system is not fixed, so it can keep the structure from resonance. Numerical simulation is conducted for nonlinear isolation system and the corresponding linear system under free vibration, sine wave, far-field and near-fault earthquake. The linear and nonlinear isolations performance of the system due to harmonic and seismic excitations will also be demonstrated and investigated in this study. In the proposed system, a mass block is pin connected to a set of circular rolling disk. If the pin is connected eccentrically to the center of the disk, the restoring force becomes nonlinear. In addition, energy is dissipated by adding viscous damper or friction damper. The nonlinear governing equation of motion for the eccentric rolling isolation system is derived based on Lagrange’s equation. The isolation frequency as a function of the eccentricity and initial angle will be investigated through free vibration analysis. By the numerical simulation of free vibration, the results show that if the eccentricity or initial angle is small, the dynamic behavior of the system is almost the same as the linear rolling behavior. When the ground excitation input is sine wave and its frequency equal to the linearized frequency, the numerical simulation results show that if no dissipation mechanism, the linear system will be divergent, but nonlinear systems will be stable because of its nonlinear behavior. When the viscous damper dissipation mechanism is adopted, under resonant frequency of the sine wave, linear isolation system is no longer divergent, but the maximan response of the nonlinear system is only about 50% of the linear system. When the PGA of El Centro and Chi-Chi earthquakes varies from 0.05 to 1 (g), the result shows that the superior of the nonlinear system over the linear system becomes more obvious as PGA increases. Therefore, with viscous damping, the nonlinear isolation system performs better than the linear one in both acceleration ratio and maximum displacement under sine wave, far field under or near fault earthquakes excitation. When isolation install friction damper, under far field and near-fault earthquake excitation, the best design of friction parameters are very close. Under resonant frequency of sine wave, the response of linear system will be divergent if the friction parameter is not big enough, while nonlinear system is stable and no resonance occurs at same dutam. Then change the PGA of two earthquakes, the range from 0.05 to 1 (g), the result shows that the displacement of the linear isolation system is closer to that of the nonlinear one.With the increases of PGA, nonlinear isolation display the better isolation effect, but linear system don’t have this advantage. Summarized above, with friction damper, the response of nonlinear systems and linear systems are similar, but if the PGA of near-field and far-field earthquakes becomes larger, nonlinear isolation system shows more and more effect than linear system. Thus, by appropriate design, the nonlinear rolling isolation system is feasible in this research.
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Teng, Min-Cheng, and 鄧敏政. "Experimental study of seismic isolation of storage tanks using friction pendulum bearings." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/78162705639989980794.
Full textAbstract:
博士國立交通大學
土木工程系
90
Storage tanks are vulnerable to earthquakes, as demonstrated recently in Chi-Chi earthquake (1999) of Taiwan, and numerous other major earthquakes worldwide. Development of cost-effective earthquake-resistant design and retrofit techniques for industrial tanks is imperative in Taiwan, as the seismic design standard has been significantly enhanced in the post-Chi-Chi revision. In this study, a series of shaking table tests has been conducted to assess the feasibility of seismic base isolation for liquid-filled storage tanks experimentally. The friction pendulum bearings (FPS) are considered rather than the elastomeric bearings as the dynamic characteristics of an FPS-isolated tank remain unchanged regardless of the storage level. Experimental results show evident reductions in dynamic pressure on the shell wall of the tank consistently while isolated. Effectiveness of FPS for seismic isolation of storage tanks is confirmed. Moreover, numerical simulations carried out using a hybrid structural-hydrodynamic model previously devised agree well with the test results, indicating adequacy of the analytical model
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Kao, Pei-Shiou, and 高培修. "Optimum Design Formulas for Isolation Systems with Viscous Dampers and Friction Dampers." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/45380946236751629383.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
99
The present study aims at developing optimum theory and design formula to find the optimum design parameter of two types of isolation systems : linear viscous energy dissipated isolation system and friction energy dissipated isolation system. For part of linear viscous energy dissipated system, minimize the mean square of absolute structural acceleration of single degree-of-freedom main system subjected to white-noise excitation, then the optimum design formula of linear viscous energy dissipated isolation system can be obtained. For part of friction energy dissipated system, the objective function is defined as the sum of squared structural absolute acceleration. Therefore, the optimal friction coefficient which minimizes the objective function can be obtained through numerical simulation under the five specific random ground excitations. Repeating the optimal process with various structural parameters, the proposed simple design formula is developed by regression of those optimal friction coefficients from numerical simulations. Finally, after the design formula is obtained, the feasibility is verified through implementing the proposed deign formula into a single-degree-of-freedom building with viscous and frictional isolation system under random, El Centro and 331 (TAP097) earthquakes. Comparing the performances of isolation system designed by two cases, the proposed design formula and directly optimized by each earthquakes, the performances between these two cases are very close. Consequently, the proposed design formula is simple and generally applicable.
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Yang, Cho-Yen, and 楊卓諺. "Study on Structural Isolation by Eccentric Rolling Isolation System with Passive and Semi-Active Friction Damping Control Strategy." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/72261107938813171795.
Full textAbstract:
博士國立臺灣科技大學
營建工程系
100
Base isolation has been popular by implemented in civil engineering. However, conventional isolation system possessing linear restoring force may be invalid under a near-fault earthquake which possesses low-frequency content and may induce resonance. Therefore, the eccentric rolling isolation system (ERIS) possessing nonlinear restoring is proposed. The base, which can be mounted on a structure or equipment, is eccentrically pinned on a circular isolator; and friction damping, which can be tuned by bolts, is considered. In passive case, the ERIS performs as good as conventional linear isolation system under far-field earthquake. Subjected to near-fault earthquake, the ERIS shows better reduction in acceleration than the corresponding linear one. The ERIS also reduced the amplification under resonant sinusoidal excitation due to nonlinearity. However, the passive isolation case under non-design earthquake may not perform as well as itself subjected to design earthquake. Thus, semi-active control is considered to improve the performances of ERIS. Several switch control laws with low and high gain are investigated. The gain mode is switched by appropriate switch logic. When the system is subjected to a small earthquake, the low gain mode is taken to make sure that the system is effective. When the system is subjected to a large earthquake, the high gain mode is taken to reduce the base displacement and provide more energy dissipation. Moreover, the continuous type switch control law can mitigate the chatter and jerk which may occur for some discontinuous switch control law.
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Lei, Kai-ming. "Response of equipment in resilient-friction base isolated structures subjected to ground motion." Thesis, 1992. http://hdl.handle.net/1957/36778.
Full textAbstract:
The response of lightweight equipment in structures supported on
resilient-friction-base isolators (R-FBI) subjected to harmonic ground motion and various
earthquake ground motions is examined. The equipment-structure base system is modeled
as a three degree-of-freedom discrete system (SDOF subsystems). An efficient
semi-analytical numerical solution procedure for the determination of equipment response
is presented. Parametric studies to examine the effects of subsystem frequency (isolator,
structure, equipment), subsystem damping, mass ratio, friction coefficient and frequency
content of the ground motion on the response of the equipment are performed. The
equipment response on a fixed-base structure subjected to ground motion is also
calculated. Friction type isolation devices can induce high frequency effects in the isolated
structure due to the stick-slip action. These effects on equipment response are examined.
The results show that the high frequency effect in the structure generated from a
friction-type base isolator doesn't, in general, cause amplifications in the response. The
R-FBI system appears to be an effective aseismic base isolator for protecting both the
structure and sensitive internal equipment.Graduation date: 1992
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Chan, Chen-Yu, and 詹鎮宇. "Development of bi-gradation velocity feedback for isolated structure with controllable friction damper." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/d9kr2a.
Full textAbstract:
碩士國立交通大學
土木工程系所
105
A semi-active isolation system, which is used for seismic protection of structural systems and generally has better control performance than a passive damper, is proposed. Traditional systems adjust their friction resistance force by directly controlling the normal force applied on the friction interface. However, this is not easy to accomplish. In order to avoid problems associated with active and passive systems, a previously developed semi-active system named Leverage-type controllable friction damper (LCFD) is used in this research. LCFD system combines a traditional passive friction damper and a leverage mechanism that has a movable central pivot. By controlling the position of the pivot in real time, the equivalent friction force of the LCFD system can be accurately adjusted. Nevertheless, this system requires the application of an appropriate control law to effectively reduce structural response during an earthquake. In this study, Bi-gradation velocity control (BGVC), which is based on the control law of proportional displacement control (PDC), is applied in the LCFD system in order to determine the pivot position. Both control laws have the same advantages, as they merely require the related-to-the-ground displacement or velocity, are simple and can be easily implemented in practice. By adapting BGVC, the excessive isolator drift induced by a near-fault earthquake can be significantly suppressed, and less control force is used in slight excitations to mitigate the acceleration response. The results of numerical analysis demonstrate that the seismic response of a structure using the LCFD with the BGVC yields a lower response. It also show that the semi-active system requires lower control energy than the active system.
37
Ke, Wei-Hao, and 柯韋豪. "Parametric study of nonlinear velocity feedback for isolation system with controllable friction damper." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/k8y28d.
Full textAbstract:
碩士國立交通大學
土木工程系所
106
A developed isolation system called Leverage-type controllable friction damper (LCFD) is used in this research, which could change the position of lever pivot in time to alter the equivalent friction force by using the principle of lever. The past research result proves that LCFD combining proportional displacement control (PDC) could reduce structural response especially for structural displacement under earthquake excitation. Two control law are used to combine with LCFD in this research, first of all the Bi-gradation velocity control (BGVC) which is based on the PDC, then the Anti-braking system velocity control (ABSVC) which is based on the ABS concept. Both control law only requires the structural velocity to calculate the equivalent friction force. The research also optimizes two parameters of BGVC to improve the result. The numerical result displays that the control law combining LCFD could reduce the response of structural displacement under major earthquakes, and retard the response of structural acceleration under minor earthquakes. The research also use ABSVC to compare with other type of control law, indicating that ABSVC could reduce much more the response of structural acceleration in far field earthquakes than BGVC.
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Tseng, Ya-Fang, and 曾雅芳. "Experimental Study of Light Weight Equipment Isolated with Multiple Direction Optimized-Friction Pendulum System." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/07510417032010415750.
Full textAbstract:
碩士逢甲大學
土木工程所
99
Proposed in this study is a Multiple Directional Optimized-Friction Pendulum System (MDO-FPS) which uses various friction coefficients, radii of curvature and displacement capacities on sliding interfaces to achieve self-adjusting the natural period, damping effect and displacement capacity of the base isolator. Therefore, it is not easy to resonate with the vibrations of the ground motions and can effectively provide good protection to equipment housed in a building by reducing its responses under near fault and severe earthquakes. In addition, an equivalent system, based on the series theory, has been derived to model the mechanical characteristic of the MDO-FPS isolator by using available commercial computer programs such as Etabs and Sap2000 software. Furthermore, in order to investigate the effectiveness of the MDO-FPS isolator on seismic mitigation, a series of shaking tables of isolated equipment was carried out in the National Center for Research on Earthquake Engineering, Taipei, Taiwan. Results from the uni-, bi- and tri-directional ground shaking tests reveal that the structural responses have been reduced significantly by more than 60%.
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Liau, Jian-Min, and 廖健閔. "A study on Seismic Capacity of Equipment with Sliding Frictional Isolator and Viscous Damper." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/45220260470965284260.
Full textAbstract:
碩士國立成功大學
建築學系碩博士班
92
Abstract Keywords: near and far field earthquake, floor response wave, damper ,sliding frictional isolator. Sliding frictional isolator is composed of a low-friction-coefficient sliding surface below the main structure in order to reduce earthquake forces delivered to the main structure. This mechanism can reduce the response of structure in earthquakes. The difference between installing a sliding frictional isolator for a structure and for an indoor equipment is that an equipment allows smaller space for displacement. Therefore, this thesis aims at reducing acceleration by applying sliding frictional isolator to an equipment and also minimizing displacement by viscous damper. Because building response may be amplified in EQ’s, isolators for equipment need to beware of this amplified floor motion. This thesis studies a type of sliding frictional isolator with flat surface. This mechanism can also disperse energy in an earthquake by added viscous dampers. According to the result of shaking table test and computer simulation, this thesis finds that when applying a sliding frictional isolator to an equipment in buildings of different heights, the following conclusions are drawn: 1. Low frequency vibration of near field wave transmitted into a building does not dissipate their magnitude. 2. Applying sliding frictional isolator to equipment can reduce equipment acceleration, whereas react displacement can be controlled by damper. 3. Lower friction-coefficient sliding surface can further reduce response acceleration , whereas sliding frictional isolator with damper is a complete system in controlling acceleration and displacement. 4. Low friction-coefficient sliding surface , together with a low damping coefficient and nonlinear coefficient greater than 1.0 damper , is suggested when a sliding frictional isolator is applied to equipment on a building with high vibration frequency. On the other hand, damper with higher damping coefficient and nonlinear coefficient smaller than 1.0 is suggested when applied on equipment in a low-vibration-frequency building.
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Ni, Chang Wan, and 張婉妮. "Effect of Near Fault Ground Motion on Structures with Frictional Seismic Isolators." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/96668309945006913034.
Full textAbstract:
碩士國立高雄第一科技大學
營建工程系
89
Presently, there are thousands of base isolated structures constructed worldwide. The number of the isolated structures has been increasing rapidly in the last few years primarily due to the maturity of the isolation technology itself and also human awareness of earthquake risk. Some of these constructed cases were even subjected to real-live earthquakes and proved the effectiveness of the technology. However, very few of them were ever subjected to near-fault ground waves that possess very different characteristics and response spectra from those of far-field waves. These characteristics include large vertical accelerations, long-period pulse-like velocity waves and strong PGA values. It is for these reasons that even though the seismic isolation has been proven of being effective for protecting structures from far-field earthquakes, further studies on the safety and effectiveness of near-fault base isolation are still required. Especially, given the fact that a near-fault earthquake is usually accompanied by sever ground shaking and can easily become a fatal disaster. By using several sets of near-fault records collected from Chi-Chi earthquake that attacked Taiwan in 1999, this study investigates and compares the seismic behaviors of structures with sliding isolators, such as FPS, when subjected to near-fault and far-field earthquakes. It is shown that the effect of the vertical acceleration component of the near-fault waves on the response of a sliding isolated structure is insignificant unless the vertical component becomes extremely large and in resonance with the vertical frequency of the superstructure. However, the horizontal displacement of the isolators and the horizontal acceleration of the superstructure can be considerably amplified by the pulse-like long-period wave possessed in most near-fault earthquakes. The conclusions drawn from this study will be helpful in modifying the design codes of near-fault seismic isolation. Strategy of mitigating the effect of long-period velocity waves and improving the effectiveness of near-fault isolation, such as using passive energy dissipation devices, low friction bearings or variable curvature isolators is also investigated.
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Lin, Jyun-Syong, and 林俊雄. "Seismic Behavior of Rocking Base-Isolated Bearings with Frictional-Hinge Dampers." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/76239022875846242510.
Full textAbstract:
碩士國立高雄第一科技大學
營建工程研究所
103
This research aims to verify that self-centering concept not only can be applied to beam column connections of building structure but also used in the base-isolation structures. Literatures proved that Rocking Base-Isolated Bearing can improve the weakness existing in the traditional sliding base-isolated bearing such as not enough stiffness under moderate earthquakes or extensive displacement under severe earthquakes. The experiment validated that damping ratio due to energy dissipation through the impact loss in rocking bearing was limited. It is proposed to install a damper on the structure to dissipate the seismic energy. In my experiment, Rocking Base-Isolated Bearing with friction damper utilizes brass or phosphor bronze sandwiched with steel plate to dissipate seismic energy. In this research, shaking table tests was performed to investigate the dynamic behavior of based-isolated structures with rocking bearing and friction damper. Totally 144 shaking table tests was conducted. Investigated parameters include material in damper (brass or phosphor bronze) and design damping ratio of 14%and 15%, corresponding to normal force18kN and 27kN for brass plate, and 12kN and 19kN for phosphor plate, aspect ratio (1:2.4 ,1:2.9) of the bearing, geometry of the rocking toe (line, spherical or higher order curve), and exciting wave forms. Test result showed that increase in the stiffness due to the damper caused of the acceleration at roof floor and the decrease the uplift at the base floor. Under the same design of damping ratio, specimens equipped with friction damper using phosphor bronze has larger structured response, energy dissipation but lower vibrating frequency then those of tests with brass damper, since phosphor bronze has higher friction coefficient applied with less normal force on the damper.
42
Chang-Chen, Chia-Shang, and 張簡嘉賞. "Analysis and Shaking Table Experiment of Near Fault Ground Motion onStructures with Frictional Seismic Isolators." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/03255204505903032892.
Full textAbstract:
碩士國立高雄第一科技大學
營建工程所
90
Presently, there are thousands of base isolated structures constructed worldwide. The number of the isolated structures has been increasing rapidly in the last few years primarily due to the maturity of the isolation technology itself and also human awareness of earthquake risk. Some of these constructed cases were even subjected to real-live earthquakes and proved the effectiveness of the technology. However, very few of them were ever subjected to near-fault ground waves that possess very different characteristics and response spectra from those of far-field waves. The response of a sliding isolated structure subjected to a set of near-fault and far-field earthquakes are simulated and compared. It is shown that the isolator displacement can be considerably enlarged in a near-fault earthquake due to the long-period velocity pulse possessed in the near-fault earthquake. Furthermore, in order to improve the performance of near-fault seismic isolation, three types of sliding isolators with the sliding surfaces of different geometry are studied and their advantages and disadvantages are discussed. The effect of using supplemental viscous damping together with these isolators is also investigated. The study shows that for a near-fault earthquake, sliding isolation with supplemental damping is beneficial in reducing both maximum base drift and structural acceleration, although the damping may have a negative effect in the isolation for far-field earthquakes. In order to study the effect of a near-fault ground motion on a sliding isolated structure, in this paper, a shaking-table test was conducted. Both near-fault and far-field ground accelerations were imposed on a full-scale model isolated by a friction pendulum system, so the structural response can be compared. Also, a set of artificially simulated pulse waves with variable pulse periods was also imposed on the isolated structure, in order to study the effect of pulse periods. Furthermore, in order to reduce the isolator displacements, a supplement viscous damper was added to the isolation system. The study shows that for a near-fault earthquake, sliding isolation with supplemental damping is beneficial in reducing both maximum base drift, even though the damping may increase the structural acceleration in a far-field earthquake.
43
Tsai, Yi-Yo, and 蔡易佑. "Bidirectional Simulation and Experiment on Friction Pendulum Isolation System and Research on Ratio between Bidirectional and Unidirectional Peak Responses." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/77867350177707740297.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
104
Seismic isolation is an effective way to reduce seismic force which transmits to superstructure. The most common sliding isolation system is friction pendulum system which (FPS). In isolation system previous research, unidirectional isolation behavior is more thorough than bidirectional isolation behavior. Therefore, we introduce bidirectional isolation simulation of FPS and combine two friction coefficient model. Base on shaking table experiment data, we check the assumption of bidirectional isolation simulation and accuracy of it. We also compare two friction coefficient model and offer some suggestions on them. By using unidirectional and bidirectional simulation, we plot figures of seven dimensionless parameters and normalized peak ground acceleration (PGA) relation respectively under six different earthquake record. Observe ratio between bidirectional and unidirectional peak responses and bidirectional isolation behavior. In ratio between bidirectional and unidirectional peak responses, we give conservative range of displacement and acceleration. Engineers can not only use the ratio to check their analysis but also utilize in static analysis. In bidirectional isolation behavior, we use input as sine waves that phase between two orthogonal direction is different and earthquake record. to analysis. The sine waves analysis results indicate energy dissipation in leading phase direction is better. According to earthquake record analysis, we determine determine one fourth of isolation period as threshold. If time interval between two orthogonal direction’s PGA arrived less than the threshold, the two orthogonal direction’s PGA arrived regard as at the same time. Base on shaking table experiment’s results, threre are good accuracy of the dimensionless parameter in acceleration. According to bidirectional experiment’s results, we can find out that isolation displacement and structural acceleration are smaller in direction which PGA happen first then the other direction and isolation effect of isolation building is worse when two orthogonal direction’s PGA arrived regard as at the same time of earthquake.
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Husfeld, Rachel L. "Base Isolation of a Chilean Masonry House: A Comparative Study." 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-05-2.
Full textAbstract:
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.
45
SEBASTIANI, PAOLO EMIDIO. "Performance-based seismic assessment for life-cycle cost analysis of existing bridges retrofitted with seismic isolation." Doctoral thesis, 2016. http://hdl.handle.net/11573/874444.
Full textAbstract:
This work adopts a probabilistic evaluation approach to investigate the effectiveness of isolation devices for bridges in terms of seismic performance, vulnerability and expected life-cycle cost-benefit. A novel procedure to evaluate a reliable structure-based IM for isolated bridges and an improved life-cycle cost analysis formulation with respect to the existing ones are the two main original contributions. This dissertation has an assessment approach, so for each step some assumptions on the design of intervention, types of modelling and analysis have been introduced. No design optimization is carried out since it was not the purpose of this work, however the assumptions are based on the state of the art and practice and they will be clearly explained together with the limitations that eventually result from them. In order to achieve the purposes, an existing bridge has been selected as case study to take into account the complexity of a real structure. Even though a single case study bridge can restrict the generality of the numerical results, the main contributions mentioned previously consist in procedures that are not conditioned on the case study and that can be readily applied to other bridges.
Damage to bridges during an earthquake event can lead to significant service breaks in the transportation system, causing primarily difficulties to the emergency operations. The main consequences due to bridge failure are a potential huge human's life loss and in addiction a wide economic impact on the transportation network, represented mainly by direct repair costs of intervention and indirect costs due to the loss of functionality of the bridge during repair.
With specific reference to the Italian transportation network, the majority of the bridges was built between 1960 and 1980, consequently these structures are to date suffering structural deterioration and a large number of them was built following antiquated design standards with deficient or missing design criteria against seismic actions, therefore the issue of retrofitting of bridges assumes a key role, and it needs to be addressed with also reference to the Life-Cycle Cost (LCC) analyses.
Between all the several design and retrofit strategies for improving the resistance of bridges to earthquakes, the seismic isolation is nowadays an effective choice for the protection of bridges that has been adopted in bridge design or retrofit for over 35 years in the United States and more recently it has been increasingly adopted also in Italy, especially towards the application of elastomeric bearings and friction-pendulum devices.
The modern design philosophies, based on probabilistic performance-based earthquake engineering (PBEE) approaches, provides useful tools to identify the best retrofits for non-seismically designed bridges not only in terms of vulnerability assessment but also in order to achieve goals such as risk mitigation or minimization of economic loss.
A primary objective of this work is the effectiveness evaluation of seismic protection devices for bridges following the probabilistic Intensity Measure (IM) based approach developed by the Pacific Earthquake Engineering Research (PEER). In fact, if IM-based approaches are well established and widely studied for bridges and buildings, there has been a very limited research to date regarding the performance assessment of bridges for evaluating the effectiveness of seismic isolation devices. This matter is then considered an actual topic implying a number of additional issues with respect to the case of non-isolated bridges.
The elastomeric bearings (ERB) and the friction pendulum system (FPS) are here considered as isolation solutions, and they are applied to an existing railway bridge as case study. The bridge has a continuous five-span steel truss deck with a total length of about 500 m carried by four concrete piers with height ranging from 50 to 130 m. Geometry, loads, structural materials and existing bearings are investigated in order to design and estimate the retrofit interventions in an executable manner which can actually be put into practice. The structural modelling is conducted by developing three-dimensional finite element (FE) models of three bridge configurations (as-built, with ERB and with FPS) and subjecting them to a suite of 80 recorded ground motions with a wide range of spectral properties that are appropriate for isolated bridges. The FE models are developed in OpenSees employing fibre beam column elements for bridge piers and bilinear hysteretic elements for isolation devices. The influence of isolation on the demand for various critical bridge elements is evaluated through the development Probabilistic Seismic Demand Models (PSDMs) with 'cloud' approach to derive analytical fragility functions by nonlinear time history analysis (NLTHA) of the models.
Peak ground acceleration (PGA) and Spectral Acceleration (Sa) calculated at different periods are adopted and compared as intensity measures (IMs) in terms of efficiency and sufficiency. To deal with the issue of adopting a reliable structure-based IM for isolated bridges, a novel procedure is introduced for the evaluation of the most appropriate period Ts which makes Sa(Ts) a reliable IM by maximizing its correlation to different components of a complex structure. The proposal of a new property for the IM, additional to efficiency and sufficiency, is addressed.
Moreover, after the definition of appropriate limit states, the analysis of vulnerability at component level is addressed, followed by the evaluation of the effectiveness of isolation in terms of total probabilities of failure after the convolution with a seismic hazard coherently evaluated with respect to the selected ground motion set. To prevent high level of damage, both isolation systems give better protection in small piers than high ones, while they give more benefits in high pier for slight level of damage. The ERB results to be the most efficient to reduce the expected damage in the piers' base, however in terms of probability of damage at 1/3 height of the pier the effect of the two isolation systems are comparable. The FPS isolation is more efficient for the small piers than higher ones, for all the limit states. Moreover, the ERB provides a more uniform effect on the piers and better results on high piers than FPS.
As mentioned above, life-cycle cost (LCC) analysis for bridges has gained widespread interest in recent years. Nevertheless, the effect of adopting seismic isolation devices for existing or new bridges, needs to be correctly addressed in terms of costs. The lack of knowledge regarding the correct estimation of LCC in presence of these kinds of devices needs to be covered by research, since in literature there are only few examples on how the isolation systems are producing cost-effective solutions for bridge owners.
In order to give a contribution in this direction, this work provides an insight regarding the damage restoration of bridge components. The nominal retrofitting costs (initial cost in case of intervention), restoration costs (due to the possible damages in bearings and piers) and indirect costs (due to the loss of functionality of the bridge during repair) are estimated in an executable manner. Finally statistical moments of seismic losses, such as the expected value and variance, are calculated for the three examined bridge configurations by different life-cycle cost formulations (Wen and Kang, 2001, Beck et al., 2002, Wen et al., 2003, Ghosh and Padgett, 2011). The proposal of an improved LCC formulation with particular attention to the issue of a correct evaluation of discount functions to commutate future costs into present values is presented. The benefits of isolation in terms of expected costs are calculated comparing the different solutions.