Browsing by Author "Wang, YP"

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A state-space approach for dynamic analysis of sliding structures
(2001-07-01)
Wang, YP
;
Liao, WH
;
Lee, CL
;
土木工程學系
;
Department of Civil Engineering
This study presents a numerical algorithm based on a state-space approach for the dynamic analysis of sliding systems. According to the proposed scheme, the equations of motion for the base-isolated structure in both the stick and slip phases are integrated into a single set of equations by treating the friction force as a Lagrange multiplier. The Lagrange multiplier is determined, with additional conditions of equilibrium and kinematic compatibility at the sliding interfaces, via a simple matrix algebraic calculation within the framework of state-space formulations. The responses can thus be obtained recursively from the discrete-time state-space equation using a one-step correction procedure. In addition, the integration step size is maintained constant throughout the analysis. The effectiveness of the proposed scheme is confirmed through tramples of sliding systems, under conditions of either free vibration or harmonic excitations, for which analytical solutions are available. Additionally, the novel algorithm is compared with a corrective psuedo-force iterative procedure for seismic response analysis of a FPS-supported five-story building. The novel algorithm is more systematic and easy to implement than conventional approaches. Moreover, by simplifying the task, the proposed algorithm also enhances accuracy and efficiency. (C) 2001 Elsevier Science Ltd. All rights reserved.
A study on seismic retrofit of multi-fab plants in Taiwan's hi-tech industry
(2004)
Wang, YP
;
Liao, WH
;
Lee, CL
;
土木工程學系
;
Department of Civil Engineering
This study investigates the seismic hazard potential of multiple-fab plants increasingly adopted by Taiwan's hi-tech industry. A typical double-fab plant for wafer foundry in Hsinchu Science-Based Industrial Park (HSBIP) is considered for case study. Dynamic analysis of the objective double-fab plant using the ground excitation recorded near the HSBIP during the 1999 Chi-Chi earthquake has been carried out. Analysis indicates that large story drifts and damages are concentrated in the soft stories where the clean-rooms are located. Seismic retrofit of the wafer foundry plant with soft-and-weak stories using a displacement-dependent metallic yielding damper is proposed to increase the stiffness and damping of the structure. Analysis shows that the peak reductions of the story drift can reach as high as 70 percent if properly designed. The proposed retrofit strategy using metallic yielding dampers proves to be effective and sufficient.
Analysis of AC electrical response for radio-frequency sputtered (Ba0.5Sr0.5)TiO3 thin film
(1999-06-01)
Wang, YP
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Through the measurement of dielectric dispersion as a function of frequency (100 Hz less than or equal to f less than or equal to 1 MHz), we investigated the trapping dielectric relaxation of r.f.-sputtered (Ba0.5Sr0.5)TiO3 film and proposed an equivalent circuit on the basis of the admittance and capacitance spectra. Admittance spectral studies in the temperature range of 200-420 K revealed the existence of a trap level. The trap, located at 0.05 eV, is envisaged to be responsible for the origin of dielectric relaxation and carrier concentration. The equivalent circuit, consisting of a series trapping resistance and capacitance combination in parallel with leakage resistance and high frequency limit capacitance, is adopted to explain satisfactorily the AC response and to identify the contribution of the shallow trap on the electrical properties of BST thin film. (C) 1999 Elsevier Science S.A. All rights reserved.
Degradation phenomena of multilayer ZnO-glass varistors studied by deep level transient spectroscopy
(1996-09-16)
Wang, YP
;
Lee, WI
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The degradation of non-Ohmic electrical characteristics of ZnO-glass chip varistors due to high-intensity impulse currents was correlated with the deep trap levels investigated by means of deep level transient spectroscopy. Three electron traps located at 0.11, 0.27, and 0.94 eV below the conduction band were observed for chip varistors before current impulse testing. These trap energy depths of the chip varistors after current impulse testing were found to be almost unchanged, but their trap densities and capture cross sections both decreased. The concentration of the trap at 0.94 eV was decreased and ascribed to oxygen vacancies existing at the grain boundaries of the varistor. The electrical degradation phenomenon of the chip varistors is closely related to the reaction between the trap at 0.94 eV and adsorbed oxygen ions at the grain boundaries. (C) 1996 American Institute of Physics.
Degradation phenomena of multilayer ZnO-glass varistors studied by deep level transient spectroscopy
(1996-09-16)
Wang, YP
;
Lee, WI
;
Tseng, TY
;
電子物理學系
;
電子工程學系及電子研究所
The degradation of non-Ohmic electrical characteristics of ZnO-glass chip varistors due to high-intensity impulse currents was correlated with the deep trap levels investigated by means of deep level transient spectroscopy. Three electron traps located at 0.11, 0.27, and 0.94 eV below the conduction band were observed for chip varistors before current impulse testing. These trap energy depths of the chip varistors after current impulse testing were found to be almost unchanged, but their trap densities and capture cross sections both decreased. The concentration of the trap at 0.94 eV was decreased and ascribed to oxygen vacancies existing at the grain boundaries of the varistor. The electrical degradation phenomenon of the chip varistors is closely related to the reaction between the trap at 0.94 eV and adsorbed oxygen ions at the grain boundaries. (C) 1996 American Institute of Physics.
Dynamic analysis of sliding structures with unsynchronized support motions
(2000-03-01)
Wang, YP
;
Liao, WH
;
土木工程學系
;
Department of Civil Engineering
The dynamic analysis of sliding structures is complicated due to the presence of friction. Synchronization of the kinematics of all the isolation bearings is often granted to simplify the task. This, however, may lead to inaccurate prediction of the structural responses under certain circumstances. Stepped structures or continuous bridges with seismic isolation are notable examples where unsynchronized bearing motions are expected. In this paper, a logically simple and numerically efficient procedure is proposed to solve the dynamic problem of sliding systems with unsynchronized support motions. The motion equations for the sliding and non-sliding modes of the isolated structure are unified into a single equation that is represented as a difference equation in a discrete-time state-space form and the base shear forces between the sliding interfaces can be determined through simple matrix algebraic analysis. The responses of the sliding structure can be obtained recursively from the discrete-time version of the motion equation with constant integration time step even during the transitions between the non-sliding and sliding phases. Therefore, both accuracy and efficiency in the dynamic analysis of the highly non-linear system can be enhanced to a large extent. Rigorous assessment of seismic structures with unsynchronized support motions has been carried out for both a stepped structure and a continuous bridge. Effectiveness of friction pendulum bearings for earthquake protection of such structures has been verified. Moreover, evident unsynchronized sliding motions of the friction bearings have been observed, confirming the necessity to deal with each of the bearings independently in the analytical model. Copyright (C) 2000 John Wiley & Sons, Ltd.
Electronic defect and trap-related current of (Ba0.4Sr0.6)TiO3 thin films
(1997-05-15)
Wang, YP
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
By employing a deep level transient spectroscopy (DLTS) technique, this work investigates the deep trap levels of rf-sputtered (Ba0.4Sr0.6)TiO3 (BST) thin films deposited at various temperatures. Arrhenius plots of DLTS spectra detect a single trap located at 0.45 eV in 450 degrees C deposited films, whereas two traps located at 0.2 and 0.40 eV appear in 550 degrees C deposited films. On the other hand, examining the I-V characteristics of the films at the temperature range of 298-403 K reveals the presence of two conduction regions in the BST him capacitors, having ohmic behavior at low voltage (<1V) and Schottky-emission or Poole-Frenkel mechanism at high voltage (>6V). The barrier height and trapped level are, respectively, estimated to be 0.46 and 0.51 eV, corresponding to the trap activation energy 0.4-0.45 eV obtained from our DLTS measurements. Compared with previous published reports, the trap distributed at 0.4-0.5 eV should be an intrinsic defect of BST and possibly ascribed to be oxygen vacancies. Meanwhile, the trap plays a prominent role in the leakage current of BST films. (C) 1997 American Institute of Physics.
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.
Modified state-space procedures for pseudodynamic testing
(2001-01-01)
Wang, YP
;
Lee, CL
;
Yo, TH
;
土木工程學系
;
Department of Civil Engineering
The existing on-line numerical integration algorithms are derived from the Newmark method, which is based on an approximation of derivatives in the differential equation. The state-space procedure (SSP), based on an interpolation of the discrete excitation signals for piecewise convolution integral, has been confirmed as more reliable than the Newmark method in terms of numerical accuracy and stability. In an attempt to enhance the pseudodynamic test, this study presents an on-line integration algorithm (referred to as the OS-SSP method) via an integration of the state-space procedure with Nakashima's operator-splitting concept. Numerical stability and accuracy assessment of the proposed algorithm in addition to the explicit Newmark method and the OS method were investigated via an eigenvalue, frequency-domain and time-domain analysis. Of the on-line integration algorithms investigated, the OS-SSP method is demonstrated as the most accurate method with an acceptable stability (although not unconditionally stable) characteristic. Therefore, the OS-SSP method is the most desirable method for pseudodynamic testing if the numerical stability criterion (Deltat/T less than or equal to 0.5) is ensured for every vibration mode involved. Copyright (C) 2001 John Wiley & Sons, Ltd.
Optical and structural properties of (Ba, Sr)TiO3 thin films grown by radio-frequency magnetron sputtering
(1999)
Wang, YP
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We studied the structural and optical properties of (Ba, Sr)TiO3 (BST) films deposited on the transparent substrates at various temperatures of 350-650 degrees C and annealed at 450-650 degrees C. Improved crystallization can be observed on 650 degrees C annealed film whose substrate temperature is 350 degrees C. The refractive index increased from 2.17 to 2.59 at lambda = 410 nm for the BST films deposited at 350-650 degrees C and it varied from 2.17 to 2.25 after annealing up to 650 degrees C. In addition, the refractive-index dispersion data related to the short-range-order structure of BST films obeyed the single-oscillation energy model. The indirect energy gap of the films deposited on Al2O3 and quartz substrates was found to be about 3.5 eV. According to the analysis of reflectance data, the optical inhomogeneity of films can be reduced by depositing the films at intermediate temperatures 450-550 degrees C. (C) 1999 Kluwer Academic Publishers.
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 isolation of rigid cylindrical tanks using friction pendulum bearings
(2001-07-01)
Wang, YP
;
Teng, MC
;
Chung, KW
;
土木工程學系
;
Department of Civil Engineering
Storage tanks are vulnerable to earthquakes, as numerous major earthquakes have demonstrated. The trend of recent revisions to make seismic design criteria for large-scale industrial storage tanks increasingly stringent has made development of cost-effective earthquake-resistant design and retrofit techniques for industrial tanks imperative. This study assesses the feasibility of seismic base isolation for making liquid-filled storage tanks earthquake resistant. The sliding-type friction pendulum seismic (FPS) bearings are considered rather than the elastomeric bearings because the dynamic characteristics of an FPS-isolated tank remain unchanged regardless of the storage level. This work has devised a hybrid structural-hydrodynamic model and solution algorithm, which would permit simple, accurate and efficient assessment of the seismic response of rigid cylindrical storage tanks in the context of seismic isolation. Extensive numerical simulations confirm the effectiveness of seismic base isolation of rigid cylindrical tanks using FPS bearings. Copyright (C) 2001 John Wiley & Sons, Ltd.
Seismic isolation of viaduct piers by means of a rocking mechanism
(2006-05-01)
Chen, YH
;
Liao, WH
;
Lee, CL
;
Wang, YP
;
土木工程學系
Rocking mechanism can be an effective means of seismic isolation, despite the fact that it is rarely conceived a possible alternative. In this study, the feasibility of utilizing a rocking mechanism for earthquake protection of slender viaduct pier structures is explored both analytically and experimentally. With a discontinuous interface between the pier footings and the underlying pile caps, a rocking system is designed to rock intermittently as the seismic overturning moment exceeds the restoring moment provided by gravity. During the rock mode, the resisting flexural moment in the pier is released while the earthquake load is counteracted by the rotational inertia with respect to the supporting foot, thus preventing the Columns from yielding. Analytical modelling of this non-linear dynamic system is derived with a numerical procedure developed based on the fourth-order Runge-Kutta-Nystrom method. A series of tests including the free rocking and seismic performance test, has been conducted using a 1:50 scaled-down model structure of a typical viaduct pier system. Both analytical and experimental results show that the rocking pier system (RPS) for seismic protection of viaduct pier structures is effective and stable, and the stronger the earthquake intensity the more pronounced the control efficiency. The concept of using rocking mechanism for seismic isolation of viaduct pier structures has been demonstrated feasible and promising. Nevertheless, practical issues such as prevention of overturning, foot damage due to impact, or possible sliding of the pier following impact need to be carefully dealt with in the design aspect. Copyright (C) 2006 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.
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 structural control using a novel high-performance active mass driver system
(2000-11-01)
Wang, YP
;
Lee, CL
;
Chen, KM
;
土木工程學系
;
Department of Civil Engineering
To resolve difficulties encountered by current technology in structural control against earthquakes, this study proposes a novel high-performance active mass driver (HP-AMD) system. Based on an active mass driver system, the device is integrated with a mechanical pulley system for stroke amplification to enhance simultaneously efficiency and save power. Meanwhile, an instantaneous optimal direct output feedback control algorithm is derived alongside the hardware development. Numerical simulation is performed using a five-storey steel frame as the object structure under the 1940 El Centro earthquake. To gain further insight into the HP-AMD system, the effects of stroke amplification as well as damper weight on system performance are explored. Analysis results demonstrate that the proposed HP-AMD system is a promising means to improving current active structural control techniques. Copyright (C) 2000 John Wiley & Sons, Ltd.
Seismic structural control using an electric servomotor active mass driver system
(2004-05-01)
Lee, CL
;
Wang, YP
;
土木工程學系
;
防災與水環境研究中心
;
Department of Civil Engineering
This Study investigates an electric-type active mass driver (AMD) system for structural vibration control. Composed primarily of an electric servomotor and a ball screw, the electrical AMD system is free from noise problems, oil leakage, and labor-intensive maintenance that commonly are associated with hydraulic AMD systems. The desired stroke amplification of the mass and the power demand of the servomotor can be adjusted via the ball screw pitch, which in turn affects the effectiveness and efficiency of the system. Meanwhile, an instantaneous optimal direct Output feedback control algorithm is adopted. Numerical simulation is performed using a five-story steel frame as the object structure under the conditions of the 1940 El Centro earthquake. The AMD system proves to be effective and efficient within a certain range of the ball screw pitch. The reductions of the peak responses can reach as high as 70% if properly designed. Requiring only the velocity measurement of the top floor for on-line feedback control. the proposed control algorithm is recommended for practical implementation. Copyright (C) 2004 John Wiley Sons, Ltd.
Self-organization phenomenon and the edge of chaos in traffic flow dynamics
(2003)
Lan, LW
;
Lin, FY
;
Wang, YP
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
According to the complexity theory, a self-organization phenomenon might exist when the phase shifts from order (non-congested) to chaos (congested) state within a system. In this paper, cellular automaton (CA) traffic simulator is applied to investigate the self-organization forming process as the traffic density grows. Real traffic data are used to examine whether the power law, an indicator of self-organization phenomenon, exists or not. Our empirical evidence on a two-lane freeway shows that self-organization phenomenon appears when the density exceeds 45% (or 60 pcu/km); however, the edge of chaos is at a density level of 33.8% (or 45 pcu/km), which should be the starting control point (e.g., ramp metering) for recurrent congestion.
Sum-frequency vibrational spectroscopic study of surface glass transition of poly(vinyl alcohol)
(2003-05-06)
Zhang, C
;
Hong, SC
;
Ji, N
;
Wang, YP
;
Wei, KH
Sum-frequency vibrational spectroscopy was employed to study surface glass transition of poly(vinyl alcohol) by monitoring the relaxation of rubbing-induced alignment of surface chains with increase of temperature. The observed chain relaxation is two-dimensional, parallel to the surface. The surface transition temperature is 58 +/- 2 degreesC, essentially the same as the bulk one.