Browsing by Author "Chung, LL"

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Instantaneous control of structures with time-delay consideration
(1997-06-01)
Chung, LL
;
Wang, YP
;
Tung, CC
;
土木工程學系
;
Department of Civil Engineering
A modified instantaneous control algorithm with time-delay consideration for the active control of structures is developed in discrete-time formulation. The shift-invariant feedback gain matrix is obtained through an optimization process such that a prescribed instantaneous quadratic performance index is minimized. The effect of time-delay is taken into consideration by introducing a compensation scheme where the feedback gain matrix for the ideal control system is modified by the effective system matrix. It is proved that the real control system with time-delay compensation conserves the eigen-properties of the ideal control system with no time-delay. In the presence of time-delay, the equation of motion of the discrete-time control system remains a set of difference equations which makes the evaluation of the control system simple and straightforward. The feasibility of the proposed control algorithm is verified numerically through eigenvalue, frequency-domain and time-domain analyses by the tendon control of a structure. With the proposed control algorithm, the control system is still effective in spite of the presence of time-delay. (C) 1997 Elsevier-Science Ltd.
Instantaneous control of structures with time-delay consideration
(1997-06-01)
Chung, LL
;
Wang, YP
;
Tung, CC
;
土木工程學系
;
Department of Civil Engineering
A modified instantaneous control algorithm with time-delay consideration for the active control of structures is developed in discrete-time formulation. The shift-invariant feedback gain matrix is obtained through an optimization process such that a prescribed instantaneous quadratic performance index is minimized. The effect of time-delay is taken into consideration by introducing a compensation scheme where the feedback gain matrix for the ideal control system is modified by the effective system matrix. It is proved that the real control system with time-delay compensation conserves the eigen-properties of the ideal control system with no time-delay. In the presence of time-delay, the equation of motion of the discrete-time control system remains a set of difference equations which makes the evaluation of the control system simple and straightforward. The feasibility of the proposed control algorithm is verified numerically through eigenvalue, frequency-domain and time-domain analyses by the tendon control of a structure. With the proposed control algorithm, the control system is still effective in spite of the presence of time-delay. (C) 1997 Elsevier-Science Ltd.
Optimal design theories and applications of tuned mass dampers
(2006-01-01)
Lee, CL
;
Chen, YT
;
Chung, LL
;
Wang, YP
;
土木工程學系
An optimal design theory for structures implemented with tuned mass dampers (TMDs) is proposed in this paper. Full states of the dynamic system of multiple-degree-of-freedom (MDOF) structures, multiple TMDs (MTMDs) installed at different stories of the building, and the power spectral density (PSD) function of environmental disturbances are taken into account. This proposed method allows for a more extensive application and successfully releases the limitations based on simplified models. The optimal design parameters of TMDs in terms of the damping coefficients and spring constants corresponding to each TMD are determined through minimizing a performance index of structural responses defined in the frequency domain. Moreover, a numerical method is also proposed for searching for the optimal design parameters of MTMDs in a systematic fashion such that the numerical solutions converge monotonically and effectively toward the exact solutions as the number of iterations increases. The feasibility of the proposed optimal design theory is verified by using a SDOF structure with a single TMD (STMD), a five-DOF structure with two TMDs, and a ten-DOF structure with a STMD. (c) 2005 Elsevier Ltd. All rights reserved.
Seismic response analysis of bridges isolated with friction pendulum bearings
(1998-10-01)
Wang, YP
;
Chung, LL
;
Liao, WH
;
土木工程學系
;
Department of Civil Engineering
A systematic method is developed for the dynamic analysis of the structures with sliding isolation which is a highly non-linear dynamic problem. According to the proposed method, a unified motion equation can be adapted for both stick and slip modes of the system, Unlike the traditional methods by which the integration interval has to be chopped into infinitesimal pieces during the transition of sliding and non-sliding modes, the integration interval remains constant throughout the whole process of the dynamic analysis by the proposed method so that accuracy and efficiency in the analysis of the non-linear system can be enhanced to a large extent. Moreover, the proposed method is general enough to be adapted for the analysis of the structures with multiple sliding isolators undergoing independent motion conditions simultaneously. The superiority of the proposed method for the analysis of sliding supported structures is verified by a three-span continuous bridge subjected to harmonic motions and real earthquakes. In addition, the side effect of excessive displacement of the superstructure induced by the sliding isolation is eliminated by replacing one of the roller supports on the abutments with hinge support. Therefore, both reductions in the forces of the substructure and the displacements of the superstructure can be achieved simultaneously. (C) 1998 John Wiley & Sons, Ltd.
Seismic response analysis of bridges isolated with friction pendulum bearings
(1998-10-01)
Wang, YP
;
Chung, LL
;
Liao, WH
;
土木工程學系
;
Department of Civil Engineering
A systematic method is developed for the dynamic analysis of the structures with sliding isolation which is a highly non-linear dynamic problem. According to the proposed method, a unified motion equation can be adapted for both stick and slip modes of the system, Unlike the traditional methods by which the integration interval has to be chopped into infinitesimal pieces during the transition of sliding and non-sliding modes, the integration interval remains constant throughout the whole process of the dynamic analysis by the proposed method so that accuracy and efficiency in the analysis of the non-linear system can be enhanced to a large extent. Moreover, the proposed method is general enough to be adapted for the analysis of the structures with multiple sliding isolators undergoing independent motion conditions simultaneously. The superiority of the proposed method for the analysis of sliding supported structures is verified by a three-span continuous bridge subjected to harmonic motions and real earthquakes. In addition, the side effect of excessive displacement of the superstructure induced by the sliding isolation is eliminated by replacing one of the roller supports on the abutments with hinge support. Therefore, both reductions in the forces of the substructure and the displacements of the superstructure can be achieved simultaneously. (C) 1998 John Wiley & Sons, Ltd.