FINITE ELEMENT ANALYSIS OF BASE ISOLATED BUILDINGS SUBJECTED TO EARTHQUAKE LOADS
Author: MAR SALOM ON1 , SERGIO OLLER2 AND ALEX BARBAT2; | Size: 0.23 MB | Format:PDF | Quality:Unspecified | Publisher: INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Int. J. Numer. Meth. Engng. 46, 1741{1761 (1999) | Year: 1999 | pages: 21
A nite element formulation modelling hyperelastic quasi-incompressible rubber-like materials (elastomers) is
developed which takes into account large displacements and large elastic strains as well as inelastic e ects.
The capacity of laminated rubber-like materials to support high loads in compression and large displacements
in shear is the principal reason for their use in devices for seismic base isolation of structures. The energydissipation
capacity of these devices is increased by using high damping rubber, which is an elastomer
incorporating carbon black particles, or having lead-plug insertion. The Ogden strain energy function has
been used as a basis for the material model implemented in a total Lagrangian formulation, the strain being
decomposed into its deviatory and volumetric parts and the pressure variable being condensed at element level.
Mooney{Rivlin and neo-Hooke strain energy functions can also be used by simply changing the parameters of
the model. The stress{strain hysteresis, which appears when these devices are subjected to dynamic or quasistatic
cyclic loads, has been modelled by frequency dependent viscoelastic and plastic constitutive models. The
bearings have been modelled by means of an equivalent single element capable of describing the composite
behaviour of the actual isolation system. The proposed model is validated using available experimental results
and it is proved to be a powerful tool in dealing with di erent bearings. Finally, results for a six-storey base
isolated building subjected to the El Centro earthquake are given.
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Control of Seismic Energy Partitioning of Bridge Piers with Sliding Rubber Bearing
Author: Hirokazu Iemura1 , Yoshikazu Takahashi1 and Youzhen Chen1 1 Dept. of Civil Eng. Systems, Kyoto University, Kyoto, Japan | Size: 0.38 MB | Format:PDF | Quality:Unspecified | pages: 8
Base isolation bearings have many good properties for seismic protection of bridges. Recently a new sliding rubber bearing was developed, which has both characteristics of sliding and rubber bearings. When we install these seismic isolation systems, reasonable inelastic design method is required. But since the conventional inelastic design method takes into account only bridge piers, it is hard to design seismic isolators which can cope with the interaction between seismic isolators and bridge piers. The purpose of this study is to understand the relationship between the seismic isolation systems and piers with respect to their energy dissipation etc. and to attempt to propose a design procedure for isolated bridges.
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State Of Art Review - Base Isolation Systems For Structures
Author: S.J.Patil , G.R.Reddy | Size: 1.8 MB | Format:PDF | Quality:Unspecified | Publisher: International Journal of Emerging Technology and Advanced Engineering, Volume 2, Issue 7, July 2012) | pages: 16 | ISBN: 2250-2459
This paper presents an overview of the present
state of base isolation techniques with special emphasis and a
brief on other techniques developed world over for mitigating
earthquake forces on the structures. The dynamic analysis
procedure for isolated structures is briefly explained. The
provisions of FEMA 450 for base isolated structures are
highlighted. The effects of base isolation on structures located
on soft soils and near active faults are given in brief. Simple
case study on natural base isolation using naturally available
soils is presented. Also, the future areas of research are
indicated.
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Principles and Practices of Seismic Isolated Buildings
Author: Amin Abrishambaf | Size: 7.8 MB | Format:PDF | Quality:Unspecified | Publisher: Eastern Mediterranean University July 2009 Gazimagusa, North Cyprus | Year: 2009 | pages: 216
Earthquake design philosophy based on capacity, directs the following two unpleasant states:
1. The situation that continues to increase the elastic strength and stiffness; in fact this is not economical and also cause higher floor accelerations.
2. The situation that limits the elastic strength and increasing ductility by detailing; indeed this approach is the acceptance of non-repairable structural damages. Base isolation is a different approach than the mentioned ones. It is based on the concept, which reducing the seismic demands rather than increasing the earthquake resistance capacity of the structure. On the other hand, application of base isolators to the structure reduce elastic base shear by shifting period of the structure and provide better performing structure that will remain essentially elastic during large bearthquakes.
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Friction-based Control System for Seismic Energy Dissipation with Isolated Stories
Author: Charalampos Iliadis Diploma in Civil Engineering Aristotle University o f Thessaloniki, 2010 | Size: 3.7 MB | Format:PDF | Quality:Unspecified | Year: 2011 | pages: 119
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BASE ISOLATION FOR MULTISTOREY BUILDING STRUCTURES
Author: Peng-Hsiang, Charng | Size: 10 MB | Format:PDF | Quality:Unspecified | Publisher: UNIVERSITY OF CANTERBURY CHRISTCHURCH, NEW ZEALAND | Year: 1998 | pages: 311
Recent earthquakes, particularly the 1989 Lorna Prieta [E2] and 1994 Northridge [E3] earthquakes in California, and the 1995 Kobe [Kl] earthquake in Japan, have caused significant
loss of life and severe damage to property. Many aseismic construction designs and technologies
have been developed over the years in attempts to mitigate the effects of earthquakes on buildings and their vulnerable contents. Attenuating the effects of severe ground motions on the buildings and their contents is always one of the most popular topics in the area of civil and structural engineering and attracts the attention of many researchers and engineers around the world. The technique of base isolation has been developed in an attempt to mitigate the effects on buildings and their contents during earthquake attacks and has been proven to be one of the more effective methods for a wide range of seismic design problems on buildings in the past two decades. Seismic isolation consists essentially of the installation of mechanisms which decouple the structures and their contents from potentially damaging earthquake-induced ground motions. This decoupling is achieved by increasing the flexibility 'of the systems, together with providing appropriate damping. Careful studies have been made of structures for which seismic isolation
may find widespread application. This has been found to include common forms of new and existing multistorey building structures.
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The HAM-SAS Seismic Isolation System for the Advanced LIGO Gravitational Wave Interferometers
Author: Alberto Stochino | Size: 7.5 MB | Format:PDF | Quality:Unspecified | Publisher: Università di Pisa Facoltà di Scienze Matematiche Fisiche e Naturali Corso di Laurea Specialistica in Scienze Fisiche Anno Accademico 2006-2007 Tesi di Laurea Specialistica | Year: 2007 | pages: 132
The three LIGO interferometers are full operative and under science run since November 2005. The acquired data are integrated with those obtained by th Virgo experiment within an international cooperation aimed to maximize the e.orts for the detection of gravitational waves.
From 2001 LIGO I is expected to be shut down and the construction and commissioning of Advanced LIGO to start. The objective of the new generation interferometers is a ten times greater sensibility with the purpose to extend of a factor of a thousand the space volume covered and to increase of the same order of magnitude the probability to detect events.
To increase the sensibility in the band below 40 Hertz, the main source of noise that Advanced LIGO have to face is the seismic noise. In this perspective, the SAS group (Seismic Attenuation Systems) of LIGO has developed a class of technologies on which the HAM-SAS system is based. Designed for the seismic isolation of the output mode cleaner optics bench and more in general for all the HAM vacuum chambers of LIGO, HAM-SAS, with little variations, can be extended to the BSC chambers as well. In HAM-SAS the legs of four inverted pendulums form the stage of attenuation of the horizontal degrees of freedom. Four GAS filters are included inside a rigid intermediate structure called Spring Box which is supported by the inverted pendulums and provide for isolation of the vertical degrees of freedom. The geometry is such that the horizontal degrees of freedom and the vertical ones are separate. Each GAS filter carries an LVDT position sensor and an electromagnetic actuator and so also each leg of the inverted pendulums. Eight stepper motors guarantee the DC control of the system.
A prototype of HAM-SAS has been constructed in Italy, at Galli & Morelli and then transferred to Massachusetts Institute of Technology in the US to be tested inside the Y-HAM vacuum chamber of the LIGO LASTI laboratory.
The test at LASTI showed that the vertical and horizontal degrees of freedom are actually uncoupled and can be treated as independent. It was possible to clearly identify the modes of the system and assume these as a basis by which to build a set of virtual position sensors and a set of virtual actuators from the real ones, respect with which the transfer function of the system was diagonal. Inside this modal space the control of the system was considerably simplified and moree.ective. We measured accurate physical plants responses for each degree of freedom and, based on these, designed specific control strategies. For the horizontal degrees of freedom we implemented simple control loops for the conservation of the static position and the damping of the resonances. For the vertical ones, be
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Recommendations for the Design and Construction of Base Isolated Structures
Author: 1 2 3 R.W .G . Blakeie y , A. W . Charleso n , H.C. Hitchcoc k , L . M . M egge t M .J.N . Priestle y b f R.D . S h a r p e6 R.I . S k i n n e r7 | Size: 4.8 MB | Format:PDF | Quality:Unspecified | Publisher: BULLETI N OF THE NEW ZEALAN D NATIONA L SOCIET Y FOR EARTHQUAK E ENGINEERING , VOL. 12, NO. 2 JUN E 1979 | Year: 1979 | pages: 22
The philosophy of base isolation of structures, generally using
flexible mountings and mechanical energy dissipating devices, is reviewed. Applications of the approach to buildings, bridges, nuclear power plants, equipment and structures rocking on their foundations are described. Where possible, recommended code provisions and design rules are given. The characteristics of the mechanical energy dissipating devices developed to date are discussed and material specification provisions presented. The requirements for construction of base isolated structures and for maintenance of the devices are given. Finally, recommendations are made
on matters for future research.
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COMPARISON OF DESIGN SPECIFICATIONS FOR SEISMICALLY ISOLATED BUILDINGS
Author: EMRE ACAR | Size: 1.8 MB | Format:PDF | Quality:Unspecified | Publisher: A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES OF MIDDLE EAST TECHNICAL UNIVERSITY | Year: 2006 | pages: 123
This study presents information on the design procedure of seismic base isolation systems. Analysis of the seismic responses of isolated structures, which is oriented to give a clear understanding of the effect of base isolation on the nature of the structure; and discussion of various isolator types are involved in this work. Seismic isolation consists essentially of the installation of mechanisms, which vdecouple the structure, and its contents, from potentially damaging earthquake induced ground motions. This decoupling is achieved by increasing the horizontal flexibility of the system, together with providing appropriate damping. The isolatorvincreases the natural period of the overall structure and hence decreases itsvacceleration response to earthquake-generated vibrations. This increase in period,
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DEVELOPMENT OF NEW BAS E ISOLATI O N DEVI CES FOR APPLICATION AT REFINERI ES AND PETROCHEMI CAL FACILITI ES
Author: Paul SUMMERS , Paul JACOB , Joaquin MARTI , Guilia BERGAMO , Luis DORFMANN Gabriella CASTELLANO , Alessandro POGGIANT , Dimitris KARABALIS , Heiko SILBE and Stelios TRIANTAFILLOU | Size: 0.42 MB | Format:PDF | Quality:Unspecified | Publisher: 13th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 1036
The concept of seismic isolation is not new, but it has not generally been used in heavy industrial settings.
The European project, INDEPTH (Development of INnovative DEvices for Seismic Protection of
PeTrocHemical Facilities), supported by the Environment and Sustainable Development Programme of
the European Commission Research Directorate General (Contract EVG1-CT-2002-00065), has, as its
objective, the development of new base isolation devices, suitable for application at refineries, LNG and
petrochemical facilities beneath critical structures, such as cylindrical tanks and spheres. The intent of isolation to reduce seismic risk and enhance performance reliability, especially for beyondvdesign basis events, since many of these critical facilities are located in areas of high seismicity worldwide.
In conjunction with development of isolation devices, new flexible piping joints will also be developed in order to accommodate increased displacements beneath isolated structures.
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