The nonholonomic and chaotic nature of a rolling isolation system

Harvey, P. Scott; Gavin, Henri P.

doi:10.1016/j.jsv.2013.01.036

Cited by 43 publications

(34 citation statements)

References 27 publications

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“…7) allowing for the top frame to displace with respect to the bottom frame. The bowl profiles of the system studied in this paper are approximately quadratic near the bowl centers and are approximately cone-shaped at larger distances from the centers [19]. These bowl profile regimes dictate the restoring forces of the system.…”

Section: Assessment Of the Seismic Performance Of Rolling Isolation Smentioning

confidence: 77%

“…(19) by L À| and substituting the expressions (12) for u x and u y , the equations of motion are transformed back to absolute (relative-to-the-ground) coordinates:…”

Section: Treatment Of Biaxial Hysteresismentioning

confidence: 99%

“…The total acceleration floor responses at three heights -1st story, mid-height, and roof, as indicated in Fig. 2 -are evaluated and then applied to the validated models for lightly-and heavily-damped RISs [19,27]. The peak relative displacement (d max R ) and the peak total acceleration (a max T ) of the RISs are recorded.…”

Section: Response Analysismentioning

confidence: 99%

“…Previous studies have been carried out to assess the in-building performance of isolated objects, but were limited to planar structural responses and unidirectional excitations [13][14][15][16][17][18]. RISs are known to exhibit strong coupling between transverse (and rotational) responses [19]. Furthermore, ground motions, structural responses, and equipment responses are inherently multidirectional.…”

Section: Introductionmentioning

confidence: 99%

“…Finally (Section 5) the performance of RISs, located at varying heights within the buildings, is assessed. The bidirectional floor responses of the seismically excited building are applied to the experimentally-validated models for lightly-and heavily-damped RISs [19,27], and empirical cumulative distribution functions (CDFs) of peak equipment responses (accelerations and displacements) are compared and design guidelines are presented.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of a rolling isolation system using reduced order structural models

Harvey

Gavin

2015

Engineering Structures

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a b s t r a c tThis paper examines the performances of lightly-and heavily-damped rolling isolation systems (RISs) located within earthquake-excited structures. Six steel structures of varying height and stiffness are selected so as to represent a range of potential RIS installations. Computation models of representative frames from each of the six structures are reduced through dynamic condensation and assembled with models for biaxial isotropic hysteretic behavior within each floor. A novel reduced order modeling approach is presented in this paper. The method combines a dynamic condensation of a linear-elastic frame with the inelastic-push over curve for a detailed elastic-plastic frame model and a novel bi-axial hysteretic model for the net inter-story inelastic behavior. The reduced inelastic model combines stiffness and mass matrices from the reduced linear model with the bi-axial inelastic floor model, and is subsequently fit to push-over curves from the detailed hysteretic model. The resulting reduced order model has three coordinates per floor and provides a much simpler model for simulating the floor responses of inelastic structures. The resulting inelastic structural models are isotropic in plan and uniform along the height. Suites of recorded ground motions representative of near-fault and far-field hazards are scaled and inputted into these hysteretic reduced models. The bidirectional floor responses at varying heights are then applied to experimentally-validated models of lightly-and heavily-damped RISs. Empirical cumulative distribution functions of peak isolator responses (relative displacement and total acceleration) for the two systems are compared, from which installation guidelines are presented.

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Section: Assessment Of the Seismic Performance Of Rolling Isolation Smentioning

confidence: 77%

“…(19) by L À| and substituting the expressions (12) for u x and u y , the equations of motion are transformed back to absolute (relative-to-the-ground) coordinates:…”

Section: Treatment Of Biaxial Hysteresismentioning

confidence: 99%

Section: Response Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Assessment of a rolling isolation system using reduced order structural models

Harvey

Gavin

2015

Engineering Structures

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Experimental validation of a simplified model for rolling isolation systems

Harvey

Zéhil

Gavin

2013

Earthq Engng Struct Dyn

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Rolling isolation systems (RISs) protect mission-critical equipment and valuable property from earthquake hazards by decoupling the dynamic responses of vibration-sensitive objects from horizontal floor motions. These responses involve the constrained rolling of steel balls between bowl-shaped surfaces. The light damping of steel balls rolling between steel plates can be augmented by adhering thin rubber sheets to the plates, thereby increasing the rolling resistance and decreasing the displacement demand on the RIS. An assessment of the ability of lightly-and heavily-damped RISs to mitigate the hazard of seismically induced failures requires high-fidelity models that can adequately capture the systems' intrinsic nonlinear behavior. The simplified model presented in this paper is applicable to RISs with any potential energy function, is amenable to both lightly-and heavily-damped RISs, and is validated through the successful prediction of peak responses for a wide range of disturbance frequencies and intensities. The validated model can therefore be used to compute the spectra of peak floor motions for which displacement demands equal capacity. These spectra are compared with representative floor motion spectra provided by the American Society of Civil Engineers 7-10. The damping provided by rolling between thin viscoelastic sheets increases the allowable floor motion intensity by a factor of 2-3, depending on the period of motion. Acceleration responses of isolation systems with damping supplied in this fashion do not grow with increased damping, even for short-period excitations. Figure 1. Exploded view of a rolling equipment isolation system.level or return period is of particular importance in the probabilistic seismic hazard analysis of contents protected by isolation. Estimating the displacement demand for an equipment isolation system corresponding to a specific installation, building site, and hazard level requires, in part, a predictive model of the isolation system behavior.To date, researchers have focused primarily on the single-axis behavior of equipment isolation systems, neglecting the coupling between transverse responses. Experimental tests on equipment isolation systems are sparse [4,[8][9][10], especially for multi-axis disturbances [11]. The prediction of the response of equipment isolation systems and their ability to protect building contents requires models that can capture the observed nonlinear behavior of actual isolation systems subjected to multi-axis shaking. Accordingly, the focus of this paper is on the experimental validation of a multi-axis, nonlinear model of rolling isolation systems (RISs) to further attenuate responses.Rolling isolation systems [12] are widely used to isolate mainframes, LAN racks, electronics enclosures, telecommunications switches, and other mission-critical equipment and valuable property. Museums around the world have adopted isolation systems to protect objects (such as The Statue of Hermes and The Gates of Hell) from earthquake-induced floor motions [13]...

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Dynamics characteristics of geometrically nonlinear isolation systems for seismic protection of equipment

Hsu

Chang

2021

Earthq Engng Struct Dyn

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Earthquakes pose risks to sensitive equipment and may result in dramatic economic loss. A widely used control strategy is to install an isolation system underneath equipment; however, excessive isolation displacements may be induced during severe earthquakes. Viscous dampers are recommended to be placed along with the isolation layer and to reduce displacements. Indeed, this combination is designed for a certain earthquake level and may be less effective in other earthquake levels. In this study, an isolation system with viscous dampers, which is installed perpendicular to the motion direction at the equilibrium position, is proposed to enhance seismic performance of important equipment through this geometrically nonlinear configuration. This configuration provides a better reduction in absolute accelerations during small-to-moderate earthquakes, while isolation displacements can be effectively mitigated during severe earthquakes.To understand the dynamic characteristics of this system, a series of investigations are carried out. The features of the effective control force are explored by the effective damping, and the phase plane analysis is conducted to understand the isolation system behavior. Then, the averaging method is employed to obtain the frequency-amplitude relationship of the proposed system, and the results inform the frequency domain behavior. The geometrically nonlinear damping is experimentally explored. Control effectiveness of the proposed system is also evaluated under seismic excitation and compared with the conventional isolation system (i.e., viscous dampers installed parallel to the isolation motion direction). As a result, the viscous damper with geometric nonlinearity can be more adaptive to different earthquake levels and thereby improves seismic isolation performance. K E Y W O R D Sbase isolation systems, effective damping, geometrically nonlinear damping, passive structural control, seismic protection of equipment INTRODUCTIONEarthquakes not only imperil the structures of buildings but also pose risks to sensitive equipment that can induce significant economic loss. A number of nonstructural components are susceptible to threats of seismic excitation such as high-precision machines and storages for fragile products in high-tech factories, sensitive medical equipment in hospitals,

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The nonholonomic and chaotic nature of a rolling isolation system

Cited by 43 publications

References 27 publications

Assessment of a rolling isolation system using reduced order structural models

Assessment of a rolling isolation system using reduced order structural models

Experimental validation of a simplified model for rolling isolation systems

Dynamics characteristics of geometrically nonlinear isolation systems for seismic protection of equipment

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