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Author: Publisher: ISBN: Category : Languages : en Pages : 200
Book Description
Aseismic design is the art and science of designing structures to withstand the forces they are subjected to in the event of an earthquake. Modern aseismic designs include the use of energy absorbing devices which are not permanently deformed when activated by earthquake motions. Analytical prediction of the response of these highly nonlinear systems to earthquake motions requires significant idealizations of the material, component, and structural behavior, and is not fully developed for all structural systems. Thus, to understand and evaluate the global behavior of structural systems with these aseismic devices, one needs to perform physical testing of complete structures subjected to earthquake motions. Because of the size limitations and expense of seismic simulators (shake tables) available and the need to test complete structures, small-scale models are often the only choice for testing. This research is an attempt to develop a procedure for designing and fabricating small scale models of base isolators which act as a passive control devices. Scale models of the laminated rubber bearings (with steel plates) and laminated rubber bearings with lead core are fabricated. A procedure to determine the stiffness properties and coefficient of damping for these bearings is presented in this study. An experimental procedure to study the effect of these bearings on the dynamic response of a 1/24 scale single story model test frame subjected to sinusoidal ground motions is also presented. The experimental results for the horizontal stiffness and coefficient of damping are regressed to formulate prediction equations which are used to develop a mathematical spring-dashpot damper model for the base isolators. The developed mathematical model is then validated by comparison of dynamic response of the test frame to sinusoidal ground motion obtained from the frame analysis using SAP 2000, version 10.0. The application of the mathematical model to a model frame subjected to scaled earthquake ground motion is also demonstrated. This part of the study is undertaken since the shake table used for testing could not simulate an actual earthquake ground motion. The displacement and acceleration responses of the test frame without and with the laminated rubber bearings and lead core rubber bearings when subjected to actual scaled earthquake ground motion record are investigated to evaluate the performance of each type of bearing as a base isolation system.
Author: Publisher: ISBN: Category : Languages : en Pages : 200
Book Description
Aseismic design is the art and science of designing structures to withstand the forces they are subjected to in the event of an earthquake. Modern aseismic designs include the use of energy absorbing devices which are not permanently deformed when activated by earthquake motions. Analytical prediction of the response of these highly nonlinear systems to earthquake motions requires significant idealizations of the material, component, and structural behavior, and is not fully developed for all structural systems. Thus, to understand and evaluate the global behavior of structural systems with these aseismic devices, one needs to perform physical testing of complete structures subjected to earthquake motions. Because of the size limitations and expense of seismic simulators (shake tables) available and the need to test complete structures, small-scale models are often the only choice for testing. This research is an attempt to develop a procedure for designing and fabricating small scale models of base isolators which act as a passive control devices. Scale models of the laminated rubber bearings (with steel plates) and laminated rubber bearings with lead core are fabricated. A procedure to determine the stiffness properties and coefficient of damping for these bearings is presented in this study. An experimental procedure to study the effect of these bearings on the dynamic response of a 1/24 scale single story model test frame subjected to sinusoidal ground motions is also presented. The experimental results for the horizontal stiffness and coefficient of damping are regressed to formulate prediction equations which are used to develop a mathematical spring-dashpot damper model for the base isolators. The developed mathematical model is then validated by comparison of dynamic response of the test frame to sinusoidal ground motion obtained from the frame analysis using SAP 2000, version 10.0. The application of the mathematical model to a model frame subjected to scaled earthquake ground motion is also demonstrated. This part of the study is undertaken since the shake table used for testing could not simulate an actual earthquake ground motion. The displacement and acceleration responses of the test frame without and with the laminated rubber bearings and lead core rubber bearings when subjected to actual scaled earthquake ground motion record are investigated to evaluate the performance of each type of bearing as a base isolation system.
Author: Dipesh Lalwani Publisher: ISBN: Category : Languages : en Pages :
Book Description
Seismic isolation is a technique used to shift the fundamental period of a structure to a long range period which reduces the forces a structure attracts during a seismic event. Two, widely used bearings in seismic base isolation of structures are elastomeric and lead rubber bearings. A typical elastomeric bearing consists of a number of layers of rubber alternated with steel shims bonded between two rubber layers. The addition of a lead core inserted in a central mandrel hole results in a lead rubber bearing (LRB). The lead enhances the bearings energy dissipating in an earthquake event. When elastomeric or LRBs are simultaneously subjected to vertical compressive load and increasing lateral displacement, the shear force equilibrium path can exhibit a critical point, beyond which the bearing exhibits negative stiffness. Semi-empirical models to simulate this behavior for elastomeric and LRB have been developed in the past. These models rely on experimentally calibrated parameters, making them impractical for design. Recently, a particular mechanics based model, developed for an elastomeric bearing only, approaches the modelling using vertical springs and a simple bi-linear constitutive relationship to represent the rotational behavior of an elastomeric bearing. Overarching goal of the present study is to build on the mechanics based elastomeric model to develop a LRB model. The elastomeric model is modified to include hysteretic behavior of LRB and also uses a Newton type numerical solution technique to solve for response of the bearing. The model, proposed in this study, utilizing vertical springs approach has shown to be capable of simulating the strength, stiffness and hysteretic behavior of LRB well.
Author: James M. Kelly Publisher: John Wiley & Sons ISBN: 1119972809 Category : Technology & Engineering Languages : en Pages : 217
Book Description
Widely used in civil, mechanical and automotive engineering since the early 1980s, multilayer rubber bearings have been used as seismic isolation devices for buildings in highly seismic areas in many countries. Their appeal in these applications comes from their ability to provide a component with high stiffness in one direction with high flexibility in one or more orthogonal directions. This combination of vertical stiffness with horizontal flexibility, achieved by reinforcing the rubber by thin steel shims perpendicular to the vertical load, enables them to be used as seismic and vibration isolators for machinery, buildings and bridges. Mechanics of Rubber Bearings for Seismic and Vibration Isolation collates the most important information on the mechanics of multilayer rubber bearings. It explores a unique and comprehensive combination of relevant topics, covering all prerequisite fundamental theory and providing a number of closed-form solutions to various boundary value problems as well as a comprehensive historical overview on the use of isolation. Many of the results presented in the book are new and are essential for a proper understanding of the behavior of these bearings and for the design and analysis of vibration or seismic isolation systems. The advantages afforded by adopting these natural rubber systems is clearly explained to designers and users of this technology, bringing into focus the design and specification of bearings for buildings, bridges and industrial structures. This comprehensive book: includes state of the art, as yet unpublished research along with all required fundamental concepts; is authored by world-leading experts with over 40 years of combined experience on seismic isolation and the behavior of multilayer rubber bearings; is accompanied by a website at www.wiley.com/go/kelly The concise approach of Mechanics of Rubber Bearings for Seismic and Vibration Isolation forms an invaluable resource for graduate students and researchers/practitioners in structural and mechanical engineering departments, in particular those working in seismic and vibration isolation.
Author: Publisher: ISBN: Category : Languages : en Pages : 312
Book Description
Elastomeric and lead-rubber bearings are two types of seismic isolation hardware widely implemented in buildings, bridges and other infrastructure in the United States and around the world. These bearings consist of a number of elastomeric (rubber) layers bonded to intermediate steel (shim) plates. The total thickness of rubber controls the low horizontal stiffness and the close spacing of the intermediate shims provides a large vertical stiffness for a given bonded rubber area and elastomer shear modulus. Conceptually, a lead-rubber bearing differs from an elastomeric bearing only through the addition of a lead-core typically located in a central hole. During earthquake ground shaking, the low horizontal stiffness of elastomeric and lead-rubber bearings translates into large lateral displacements, typically on the order of 100--200% rubber shear strain, that might lead to significant reductions in the axial load carrying capacity and vertical stiffness of the individual bearings. This dissertation presents an analytical and experimental investigation of the coupled horizontal-vertical response of elastomeric and lead-rubber bearings focusing on the influence of lateral displacement on the vertical stiffness. Component testing was performed with reduced scale low-damping rubber (LDR) and lead-rubber (LR) bearings to determine the vertical stiffness at various lateral offsets. The numerical studies included finite element (FE) analysis of the reduced scale LDR bearing. The results of the experimental and FE investigations were used to evaluate three analytical formulations to predict the vertical stiffness at a given lateral displacement. From component testing the vertical stiffness of the LDR and LR bearings was shown to decrease with increasing lateral displacement and at a lateral displacement equivalent to 150% rubber shear strain a 40--50% reduction in vertical stiffness was observed. One of the three analytical formulations, based on the Koh-Kelly two-spring model, was shown to predicted the measured reduction in vertical stiffness of the LDR and LR bearings at each lateral offset with reasonable accuracy. In addition, earthquake simulation testing was performed to investigate the coupled horizontal-vertical response of a bridge model isolated with either LDR or LR bearings. The results of simulations performed with three components of excitation were used to evaluate an equivalent linear static (ELS) procedure for the estimation of the vertical load due to the vertical ground shaking. The equivalent linear static procedure was shown to conservatively estimate measured maximum vertical loads due to the vertical component of excitation for most simulations.
Author: M. J. N. Priestley Publisher: John Wiley & Sons ISBN: 9780471579984 Category : Technology & Engineering Languages : en Pages : 704
Book Description
Because of their structural simplicity, bridges tend to beparticularly vulnerable to damage and even collapse when subjectedto earthquakes or other forms of seismic activity. Recentearthquakes, such as the ones in Kobe, Japan, and Oakland,California, have led to a heightened awareness of seismic risk andhave revolutionized bridge design and retrofit philosophies. In Seismic Design and Retrofit of Bridges, three of the world's topauthorities on the subject have collaborated to produce the mostexhaustive reference on seismic bridge design currently available.Following a detailed examination of the seismic effects of actualearthquakes on local area bridges, the authors demonstrate designstrategies that will make these and similar structures optimallyresistant to the damaging effects of future seismicdisturbances. Relying heavily on worldwide research associated with recentquakes, Seismic Design and Retrofit of Bridges begins with anin-depth treatment of seismic design philosophy as it applies tobridges. The authors then describe the various geotechnicalconsiderations specific to bridge design, such as soil-structureinteraction and traveling wave effects. Subsequent chapters coverconceptual and actual design of various bridge superstructures, andmodeling and analysis of these structures. As the basis for their design strategies, the authors' focus is onthe widely accepted capacity design approach, in which particularlyvulnerable locations of potentially inelastic flexural deformationare identified and strengthened to accommodate a greater degree ofstress. The text illustrates how accurate application of thecapacity design philosophy to the design of new bridges results instructures that can be expected to survive most earthquakes withonly minor, repairable damage. Because the majority of today's bridges were built before thecapacity design approach was understood, the authors also devoteseveral chapters to the seismic assessment of existing bridges,with the aim of designing and implementing retrofit measures toprotect them against the damaging effects of future earthquakes.These retrofitting techniques, though not considered appropriate inthe design of new bridges, are given considerable emphasis, sincethey currently offer the best solution for the preservation ofthese vital and often historically valued thoroughfares. Practical and applications-oriented, Seismic Design and Retrofit ofBridges is enhanced with over 300 photos and line drawings toillustrate key concepts and detailed design procedures. As the onlytext currently available on the vital topic of seismic bridgedesign, it provides an indispensable reference for civil,structural, and geotechnical engineers, as well as students inrelated engineering courses. A state-of-the-art text on earthquake-proof design and retrofit ofbridges Seismic Design and Retrofit of Bridges fills the urgent need for acomprehensive and up-to-date text on seismic-ally resistant bridgedesign. The authors, all recognized leaders in the field,systematically cover all aspects of bridge design related toseismic resistance for both new and existing bridges. * A complete overview of current design philosophy for bridges,with related seismic and geotechnical considerations * Coverage of conceptual design constraints and their relationshipto current design alternatives * Modeling and analysis of bridge structures * An exhaustive look at common building materials and theirresponse to seismic activity * A hands-on approach to the capacity design process * Use of isolation and dissipation devices in bridge design * Important coverage of seismic assessment and retrofit design ofexisting bridges
Author: 
Author: 
Author: Dipesh Lalwani
Author: Ioannis V. Kalpakidis
Author: James M. Kelly
Author: 
Author: Dynamic Isolation Systems, Inc
Author: Gianmario Benzoni
Author: Raymond George Tyler
Author: 
Author: M. J. N. Priestley