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Isolation System (isolation + system)

Distribution by Scientific Domains
Engineering100%

Kinds of Isolation System

  • base isolation system
    		•

    Selected Abstracts

    Robust Design of Fault Detection and Isolation Systems

    QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 5 2006
    Daniele Romano
    Abstract Inspired by the rationale of Robust Design, a novel methodology is presented for the design of diagnostic systems for fault detection and isolation (FDI). Detection/isolation capability and robustness, i.e. sensitivity to faults and insensitivity to noise, are addressed in an integrated way within a fully stochastic framework. Although FDI is a classical problem in control engineering, this new approach improves the current state of the art both in terms of general applicability and optimality of the design solution. It demonstrates the potential of robust design in fostering innovation in a variety of technical sectors. For illustrative purposes, the methodology is applied to the design of a FDI system for a fluid mixer. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Java-powered virtual laboratories for earthquake engineering education

    COMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 3 2005
    Y. Gao
    Abstract This paper presents a series of Java-Powered Virtual Laboratories (VLs), which have been developed to provide a means for on-line interactive experiments for undergraduate and graduate education. These VLs intend to provide a conceptual understanding of a wide range of topics related to earthquake engineering, including structural control using the tuned mass damper (TMD) and the hybrid mass damper (HMD), linear and nonlinear base isolation system, and nonlinear structural dynamic analysis of multi-story buildings. A total of five VLs are currently available on-line at: http://cee.uiuc.edu/sstl/java and have been incorporated as a reference implementation of educational modules in the NEESgrid software (http://www.neesgrid.org/). © 2005 Wiley Periodicals, Inc. Comput Appl Eng Educ 13: 200,212, 2005; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20050 [source]

    Experimental performance evaluation of an equipment isolation using MR dampers

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2009
    Yu-Cheng Fan
    Abstract Critical non-structural equipments, including life-saving equipment in hospitals, circuit breakers, computers, high technology instrumentations, etc., are vulnerable to strong earthquakes, and the failure of these equipments may result in a heavy economic loss. In this connection, innovative control systems and strategies are needed for their seismic protections. This paper presents the performance evaluation of passive and semi-active control in the equipment isolation system for earthquake protection. Through shaking table tests of a 3-story steel frame with equipment on the first floor, a magnetorheological (MR)-damper together with a sliding friction pendulum isolation system is placed between the equipment and floor to reduce the vibration of the equipment. Various control algorithms are used for this semi-active control studies, including the decentralized sliding mode control (DSMC) and LQR control. The passive-on and passive-off control of MR damper is used as a reference for the discussion on the control effectiveness. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Performance of a guideway seismic isolator with magnetic springs for precision machinery

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2009
    George C. Yao
    Abstract This paper proposes the use of the nonlinear restoring force in an isolation system to improve the performance of a seismic isolator. Nonlinear magnetic springs applied to guideway sliding isolators (GSI) that protect precision machinery against seismic motion were studied. The magnetic springs use a non-contact magnetic repulsion force to achieve a nonlinear property. A numerical simulation model of the GSI system using step-by-step integration in the time domain was developed. A full-scale shaking table test was performed to verify the accuracy of the numerical model. Simulation and experimental results show that the GSI system with magnetic springs has good performance when subjected to floor vibrations during earthquakes. A parametric analysis of the magnetic springs in the GSI system under seismic motion was theoretically investigated. It was found that sufficient magnetic forces can diminish the system relative displacements. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Uplift-restraining Friction Pendulum seismic isolation system

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2006
    Panayiotis C. Roussis
    Abstract This paper extends the scope of seismic isolation by introducing an innovative uplift-restraining Friction Pendulum system. Termed the XY-FP isolator, the new isolation device consists of two orthogonal opposing concave beams interconnected through a sliding mechanism that permits tension to develop in the bearing, thereby preventing uplift. Owing to its distinct configuration, the XY-FP isolator possesses unique properties for a seismic isolator, including uplift restraint, decoupling of the bi-directional motion along two orthogonal directions, and capability of providing independent stiffness and energy dissipation along the principal horizontal directions of the bearing. The study concentrates on introducing the concept and establishing the underlying principles of operation of the new XY-FP isolator, formulating the mathematical model for the XY-FP isolator, and presenting its mechanical behaviour through a displacement-control testing program on a single XY-FP isolator. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Shake table tests on a mass eccentric model with base isolation

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2003
    Bijan Samali
    Abstract A mass eccentric structure is usually more seismically vulnerable than its concentric counterpart because of the coupled torsional,translational response of such structures. In this work, dynamic characteristics and response of a five-storey benchmark model with moderate mass eccentricity were investigated using a shake table, simulating four different ground motions. The effectiveness of laminated rubber bearings (LRB) and lead-core rubber bearings (LCRB) in protecting eccentric structures was examined and evaluated in relation to translational and torsional responses of the benchmark model. It was observed that both translational and torsional responses were significantly reduced with the addition of either a LRB or LCRB isolated system regardless of the nature of ground motion input. The LRB were identified to be more effective than LCRB in reducing model relative displacements, the relative torsional angle as well as accelerations, and therefore provided a better protection of the superstructure and its contents. On the other hand, LCRB rendered a smaller torsional angle and absolute displacement of the base isolation system, hence a more stable structural system. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Seismic isolation of buildings with sliding concave foundation (SCF)

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2003
    M. Hamidi
    Abstract In this paper, a new base isolation system, namely the sliding concave foundation (SCF), is introduced and the behaviour of the buildings using such a system is theoretically investigated. A building supported on the new system behaves like a compound pendulum during seismic excitation. The pendulum behaviour accompanied by the large radius of foundation curvature shifts the fundamental period of the system to a high value (e.g. more than 8sec), in a frequency range where none of the previously recorded earthquakes had considerable energy. This results in a large decrease in the structural responses. Since small friction forces are essential on the contact surfaces, PTFE sheets can be used as sliding surfaces. Although the pure frictional sliding systems have the same efficiency as the SCF, in reducing the responses of the superstructure, the main advantage of the new system is a significant decrease in sliding displacement. The performance of the SCF subjected to a number of harmonic and non-harmonic base excitations is studied and its ability to reduce the structural responses is examined. Some numerical examples are solved for a single-degree-of-freedom (SDOF) structure and the responses are compared with the responses of the same SDOF structure on a fixed base or a pure frictional sliding support system. The comparisons confirm the effectiveness of the new system. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Probabilistic seismic demand analysis of controlled steel moment-resisting frame structures

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2002
    Luciana R. Barroso
    Abstract This paper describes a proposed methodology, referred to as probabilistic seismic control analysis, for the development of probabilistic seismic demand curves for structures with supplemental control devices. The resulting curves may be used to determine the probability that any response measure, whether for a structure or control device, exceeds a pre-determined allowable limit. This procedure couples conventional probabilistic seismic hazard analysis with non-linear dynamic structural analyses to provide system specific information. This method is performed by evaluating the performance of specific controlled systems under seismic excitations using the SAC Phase II structures for the Los Angeles region, and three different control-systems: (i) base isolation; (ii) linear viscous brace dampers; and (iii) active tendon braces. The use of a probabilistic format allows for consideration of structural response over a range of seismic hazards. The resulting annual hazard curves provide a basis for comparison between the different control strategies. Results for these curves indicate that no single control strategy is the most effective at all hazard levels. For example, at low return periods the viscous system has the lowest drift demands. However, at higher return periods, the isolation system becomes the most effective strategy. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Approximate analysis methods for asymmetric plan base-isolated buildings

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2002
    Keri L. Ryan
    Abstract An approximate method for linear analysis of asymmetric-plan, multistorey buildings is specialized for a single-storey, base-isolated structure. To find the mode shapes of the torsionally coupled system, the Rayleigh,Ritz procedure is applied using the torsionally uncoupled modes as Ritz vectors. This approach reduces to analysis of two single-storey systems, each with vibration properties and eccentricities (labelled ,effective eccentricities') similar to corresponding properties of the isolation system or the fixed-base structure. With certain assumptions, the vibration properties of the coupled system can be expressed explicitly in terms of these single-storey system properties. Three different methods are developed: the first is a direct application of the Rayleigh,Ritz procedure; the second and third use simplifications for the effective eccentricities, assuming a relatively stiff superstructure. The accuracy of these proposed methods and the rigid structure method in determining responses are assessed for a range of system parameters including eccentricity and structure flexibility. For a subset of systems with equal isolation and structural eccentricities, two of the methods are exact and the third is sufficiently accurate; all three are preferred to the rigid structure method. For systems with zero isolation eccentricity, however, all approximate methods considered are inconsistent and should be applied with caution, only to systems with small structural eccentricities or stiff structures. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Base isolation for retrofitting historic buildings: Evaluation of seismic performance through experimental investigation

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2001
    Antonello De Luca
    Abstract An experimental test program on a full-scale model representing a sub-assemblage of the cloister facade of the Sao Vicente de Fora monastery, retrofitted through base isolation, has been recently carried out at the European Laboratory for Structural Assessment of the Joint Research Centre of the European Commission. In this paper an overview of the laboratory model and the experimental results is provided. In particular, firstly the test model is described, including the geometry and mechanical properties of the masonry specimen and the design of the isolation devices; then the testing method and the sub-structuring of the isolation system are described and the seismic inputs adopted for the pseudo-dynamic tests are defined. Finally, the experimental results are discussed and compared to the analogous results obtained on the ,as is', fixed-base sub-assemblage model. The implications of the test outcomes are emphasized and developments of this research line are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Simplified inelastic seismic analysis of base-isolated structures using the N2 method

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2010
    Vojko Kilar
    Abstract In the paper a simplified nonlinear method has been applied to the analysis of base-isolated structures. In the first part, a three-linear idealization of the capacity curve is proposed. The initial stiffness is defined based on the first yielding point in the superstructure, whereas the secondary slope depends on the failure mechanism of the superstructure. A consequence is a much more pronounced secondary slope, which does not correspond to the presumptions used in the originally proposed N2 method. A parametric nonlinear dynamic study of single degree of freedom systems with different hardening slopes and damping has been performed for an ensemble of seven EC8 spectrum-compatible artificial accelerograms. It was concluded that, in the long-period range, the equal displacement rule could be assumed also for the proposed systems with non-zero post-yield stiffness. In the second part, the proposed idealization was used for the analysis of isolated RC frame buildings that were isolated with different (lead) rubber-bearing isolation systems. The stiffness of the isolators was selected for three different protection levels and for three different ground motion intensities, which have resulted in elastic as well as moderately and fully damaged superstructure performance levels. Three different lateral load distributions were investigated. It was observed that a triangular distribution, with an additional force at the base, works best in the majority of practical cases. It was concluded that the N2 method can, in general, provide a reasonably accurate prediction of the actual top displacement, as well as of the expected damage to the superstructure. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Experimental investigation on the seismic response of a steel liquid storage tank equipped with floating roof by shaking table tests

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2010
    M. De Angelis
    Abstract In this paper, the effectiveness of the base isolation on steel storage tanks has been investigated through numerical models and then checked by shaking table tests on a reduced scale (1:14) model of a real steel tank, typically used in petrochemical plants. In the experimental campaign the floating roof has also been taken into account. The tests have been performed on the physical model both in fixed and isolated base configurations; in particular two alternative base isolation systems have been used: high-damping rubber bearings devices and sliding isolators with elasto-plastic dampers. Finally, a comparison between experimental and numerical results has also been performed. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Sensitivity of seismically isolated structures

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2009
    Ioannis Politopoulos
    Abstract In this paper we study the sensitivity of seismically isolated structures to a small variability of the earthquake excitation and of some structural properties with respect to the probability of failure and floor spectra. In particular, the influence of the nonlinear behaviour of the isolated superstructure on the vulnerability and on the floor spectra is investigated by means of a series of Monte Carlo simulations of simple two degrees-of-freedom systems. Several types of passive and active isolation systems are examined and three different idealized nonlinear constitutive laws are considered for the superstructure. It is found that, in general, the probability of failure does not depend on the specific cyclic behaviour of the assumed constitutive law and general trends regarding the impact of different isolation devices on vulnerability are established. As for the floor spectra, the influence of moderate nonlinear behaviour of isolated superstructures, with the exception of the case of a non-dissipative elastic nonlinear law, is negligible, contrary to the case of conventional structures. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Effect of variation of normal force on seismic performance of resilient sliding isolation systems in highway bridges

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2005
    Hirokazu Iemura
    Abstract In this study, a series of shaking table tests are carried out on scaled models of two seismically isolated highway bridges to investigate the effect of rocking motion and vertical acceleration on seismic performance of resilient sliding isolators. In addition, performance of RSI is compared with system having solely natural rubber bearings. Test results show that variation of normal force on sliders due to rocking effect and vertical acceleration makes no significant difference in response of RSI systems. In addition, analytical response of prototype isolated bridge and the model used in experiments is obtained analytically by using non-linear model for isolation systems. It is observed that for seismically isolated bridges, dynamic response of full-scale complex structures can be predicted with acceptable accuracy by experiments using a simple model of the structure. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Design of bilinear hysteretic isolation systems

    EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2003
    M. Fragiacomo
    Abstract This paper concerns the design of passive base isolation systems characterized by a bilinear hysteretic behaviour. The study refers to the case where the structure to be isolated (superstructure) vibrates according to the first mode. In this case the whole isolated structure can be modelled by a two-degree-of-freedom system. The base isolation effectiveness has been evaluated for different characteristics of the device, namely mass, strength, elastic and plastic stiffness, by using mainly energetic quantities. The optimum values for the base device have been obtained by minimizing the input energy and the displacement of the superstructure. Conclusions are drawn for superstructures with a fundamental period of 0.5s, a damping ratio of 5% and for three different kinds of earthquake ground motions. The study showed that the seismic input greatly affects the behaviour of the isolated structure, and therefore the design ground motion must be carefully chosen, dependent on the characteristics of the site. A simple procedure that involves mainly linear dynamic analyses is proposed for the design of base devices used in conjunction with superstructures of any fundamental vibration period. The procedure produces good results in spite of its simplicity, and therefore it is suitable for practical use by design engineers. Copyright © 2003 John Wiley & Sons, Ltd. [source]