Experimental Study of Active Control for MDOF Seismic Structures

Chung, Lap-Loi; Lin, Rong; Soong, T. T.; Reinhorn, A. M.

doi:10.1061/(asce)0733-9399(1989)115:8(1609)

Cited by 156 publications

(68 citation statements)

References 9 publications

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“…Chung et al (1998) applied this technique to an active control experiment by changing the interval time of earthquake records and defining the ratios for the structural parameters. In this research, the active isolation systems of the model buildings are small-scale buildings that should consider the similitude technique.…”

Section: Control Performance Evaluationmentioning

confidence: 99%

Multiaxial active isolation for seismic protection of buildings

Chang

Spencer

Shi

2013

Struct. Control Health Monit.

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Structural control technology has been widely accepted as an effective means for the protection of structures against seismic hazards. Passive base isolation is one of the common structural control techniques used to enhance the performance of structures subjected to severe earthquake excitations. Isolation bearings employed at the base of a structure naturally increase its flexibility, but concurrently result in large base displacements. The combination of base isolation with active control, i.e., active base isolation, creates the possibility of achieving a balanced level of control performance, reducing both floor accelerations as well as base displacements. Many theoretical papers have been written by researchers regarding active base isolation, and a few experiments have been performed to verify these theories; however, challenges in appropriately scaling the structural system and modeling the complex nature of control-structure interaction have limited the applicability of these results. Moreover, most experiments only focus on the implementation of active base isolation under unidirectional excitations. Earthquakes are intrinsically multi-dimensional, resulting in out-of-plane responses, including torsional responses.Therefore, an active isolation system for buildings using multi-axial active control devices against multi-directional excitations must be considered.The focus of this dissertation is the development and experimental verification of active isolation strategies for multi-story buildings subjected to bi-directional earthquake loadings. First, a model building is designed to match the characteristics of a representative full-scale structure.The selected isolation bearings feature low friction and high vertical stiffness, providing stable behavior. In the context of the multi-dimensional response control, three, custom-manufactured actuators are employed to mitigate both in-plane and out-of-plane responses. To obtain a highiii fidelity model of the active isolation systems, a hybrid identification approach is used which combines the advantages of the lumped mass model and nonparametric methods. Controlstructure interaction (CSI) is also included in the identified model to further enhance the control authority. By employing the H 2 /LQG control algorithm, the controllers for the hydraulic actuators promise high performance and good robustness. The active isolation is found to possess the ability to reduce base displacements, as well as producing comparable accelerations over the passive isolation. The proposed active isolation strategies are validated experimentally for a sixstory building tested on the six degree-of-freedom shake table in the Smart Structures Technology Laboratory at the University of Illinois at Urbana-Champaign.iv ACKNOWLEDGMENTS

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Section: Control Performance Evaluationmentioning

confidence: 99%

Multiaxial active isolation for seismic protection of buildings

Chang

Spencer

Shi

2013

Struct. Control Health Monit.

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“…0  R , t acc = 2 s, α = 10π rad/s 2 , and ω max = 20π rad/s 2 . The MDOF structure was studied by Chung et al (1989) and has the modal frequencies of 2.24, 6.83, and 11.53 Hz, respectively. As is observed, the fi rst two modes' frequencies are very different from the maximum frequency of the excitation, i.e., ω max = 20π rad/s 2 ; therefore, resonance does not occur by the mentioned excitation.…”

Section: Numerical Examplesmentioning

confidence: 99%

A novel semi-active TMD with folding variable stiffness spring

Rafieipour

Ghorbani‐Tanha

Rahimian

et al. 2014

Earthq. Eng. Eng. Vib.

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An innovative variable stiffness device is proposed and investigated based on numerical simulations. The device, called a folding variable stiffness spring (FVSS), can be widely used, especially in tuned mass dampers (TMDs) with adaptive stiffness. An important characteristic of FVSS is its capability to change the stiffness between lower and upper bounds through a small change of distance between its supports. This special feature results in lower time-lag errors and readjustment in shorter time intervals. The governing equations of the device are derived and simplifi ed for a symmetrical FVSS with similar elements. This device is then used to control a single-degree-of-freedom (SDOF) structure as well as a multi-degree-of-freedom (MDOF) structure via a semi-active TMD. Numerical simulations are conducted to compare several control cases for these structures. To make it more realistic, a real direct current motor with its own limitations is simulated in addition to an ideal control case with no limitations and both the results are compared. It is shown that the proposed device can be effectively used to suppress undesirable vibrations of a structure and considerably improves the performance of the controller compared to a passive device.

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“…For any given system, the desirable delay time pairs are extracted from the delay time pairs which are evaluated from Equation (9) and they should be located in the stable regions of that particular sys tem. Once the desirable delay time pairs and their corresponding frequency ratios are identified, one can calculate the desirable minimum steady-state magnification factors by using Equation (8).…”

Section: Trol (Ie K =K 2 =0)mentioning

confidence: 99%

“…Chung et al [8) also conducted experimental studies Effects of time delay on the stability and per on an MDOF system with equal delay times. Hou formance of control systems has drawn attention of and Iwan [4) conducted a study on the effect of time many investigators in different engineering disci delay on actively controlled SDOF model with plines, including structural systems [1-8), chemical equal delay times and subjected to harmonic exci processes [9][10][11][12][13][14][15], remotely controlled undersea and tation.…”

Section: Introductionmentioning

confidence: 99%

Stability and performance of feedback control systems with time delays

Ali

Hou

Noori

1998

Computers & Structures

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Abstract-This paper investigates the time delay effects on the stability and performance of active feed back control systems for engineering structures. A computer algorithm is developed for stability analy sis of a SDOF system with unequal delay time pair in the velocity and displacement feedback loops. It is found that there may exist multiple stable regions in the plane of the time delay pair, which contain time delays greater than the maximum allowable values obtained by previous studies. The size, shape and location of these stable and unstable regions depend on the system parameters and the feedback control gains. For systems with multiple stable regions, the boundaries between the stable and unstable regions in the plane of the time delay pair are explicitly obtained. The delay time pairs that forms these boundaries are called the critical delay time pairs at which the steady-state response becomes unbounded. The conclusions are valid for both large and small delay times. For any system with mul tiple stable regions, preliminary guidelines obtained from an explicit formula are given to find the desir able delay time pair(s). When used, these desirable delay time pair(s) not only stabilize an unstable system with inherent time delays, but also significantly reduce the system response and control force. For any system with multiple stable regions, these desirable delay time pair(s) are above the maximum allowable delay times obtained by previous studies. Numerical results, for both steady-state and transi ent analysis, are given to investigate the performance of delayed feedback control systems subjected to both harmonic and real earthquake ground motion excitations. ~O 1997 Published by

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Experimental Study of Active Control for MDOF Seismic Structures

Cited by 156 publications

References 9 publications

Multiaxial active isolation for seismic protection of buildings

Multiaxial active isolation for seismic protection of buildings

A novel semi-active TMD with folding variable stiffness spring

Stability and performance of feedback control systems with time delays

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