Browsing by Author "Su, Wei Chih"

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Application of damage locating vectors approach on monitoring shock isolation system
(2016-01-01)
Quang Tuyen Le
;
Huang, Chiung Shiann
;
Su, Wei Chih
;
土木工程學系
;
Department of Civil Engineering
Structural damage detection based on the changes of dynamic properties is a major topic for structural health monitoring. In this paper, efforts are made to extend the flexibility-based damage localization methods, especially the damage locating vectors (DLVs) method, to the case of earthquake vibration, where the finite element model and mass matrices are not available. First, a new method using continuous Cauchy wavelet transform (CCWT) and ARX (autoregressive with exogenous input) model is applied to identify the modal parameters of a five-storey steel frame with seismic base isolation system LRB from its simulated acceleration responses under 10% and 100% of Chi-Chi Earthquake excitation (Taiwan, 1999). The DLVs, which determined from the change of flexibility matrix between two cases, are then used to monitor the shock isolation device in the structure through a weighted relative displacement index (WRDI). The proposed scheme is also proved to be superior to mode shape based methods (MAC, COMAC) in monitoring shock isolation system.
Applying Time-Frequency Analysis on Earthquake Inputs and Structure Responses
(2014-01-01)
Huang, Chiung Shisnn
;
Su, Wei Chih
;
Chen, Liane Jye
;
Di Wang, Shing
;
土木工程學系
This work presents the use of a short time Fourier transform to identify the modal parameters (such as natural frequencies, damping ratios and mode shapes) of a structure from its earthquake responses data. The short time Fourier transform is applied to the measured acceleration responses of a structural system, and to reconstruct the autoregressive with exogenous input (ARX) model in time-frequency domain. The accuracy of this procedure is numerically confirmed; the effects of the remove frequency band and noise on the ability to accurately estimate the dynamic characteristics are also investigated.
Combining subspace approach and short time Fourier analysis for locating structural damage storeys
(2015-08-01)
Huang, Chiung Shiann
;
Chen, Liane Jye
;
Hung, Shih Lin
;
Ding, Chun Ting
;
Su, Wei Chih
This study proposes a novel and efficient approach for locating the floors of a building whose stiffnesses change after being subject to a strong earthquake. The floors that may be damaged are determined by comparing the unitary stiffness matrix in different stages in the life cycle of a building. To evaluate the coefficient matrices of a state-space model, the proposed procedure applies a subspace approach in conjunction with the short time Fourier analysis. The dynamic characteristics of a structure are determined from the coefficient matrices. Next, the unitary stiffness matrix is constructed by identifying natural frequencies and mode shapes. The effectiveness of the proposed procedure is verified using the measured earthquake acceleration responses of a three-storey structure that sustains damage on one or two floors and an eight-storey steel frame under a 200 Gal and a 1200 Gal earthquake, such as the Chi-chi earthquake that shook Taiwan on September 1999. The proposed scheme is compared to mode shape based approaches in identifying damaged floors, and is demonstrated to be superior to both MAC (Modal Assurance Criterion) and COMAC (Coordinate Modal Assurance Criterion).
Identification of modal parameter of nonlinear system from seismic response data using amplitude-dependent time series model
(2014-06-01)
Su, Wei Chih
;
Huang, Chiung Shiann
;
Liu, Ching Yu
;
Le, Quang Tuyen
;
交大名義發表
The present work develops a novel procedure of establishing an amplitude-dependent time series model for a nonlinear system and estimating the instantaneous modal parameters of the system from the dynamical responses. The undetermined coefficient in an amplitude-dependent autoregressive with exogenous input (amplitude-dependent ARX) model are assumed as functions of amplitude and are expanded by shape functions constructing by moving least-squares with polynomial basis functions. The amplitude of dynamical responses could be obtained by Hilbert transform. The instantaneous modal parameters of the system are directly estimated from the coefficient in the amplitude-dependent ARX model. The feasibility of the procedure is demonstrated by processing numerically simulated dynamic responses of a nonlinear system. The proposed scheme is demonstrated to be superior to time-varying ARX model and recursive method in identifying modal parameters. Finally, the proposed approach is applied to process measured data for a frame specimen subjected to a series of base excitations in shaking table tests. The specimen was damaged during testing. The identified modal parameters are consistent with observed physical phenomena.
. Modal Identification Of Structures From Seismic Response Data Via Amplitude-Dependent Time Series Model
(2014)
Su, Wei Chih
;
Huang, Chiung Shiann
;
Liu, Ching-Yu
;
交大名義發表
;
National Chiao Tung University
The present work develops a novel procedure of establishing an amplitude-dependent time series model for a nonlinear system and estimating the instantaneous modal parameters of the system from the dynamical responses. The undetermined coefficient in an amplitude-dependent autoregressive with exogenous input (amplitude-dependent ARX) model are assumed as functions of amplitude and are expanded by shape functions constructing by moving least-squares with polynomial basis functions. The amplitude of dynamical responses could be obtained by Hilbert transform. The instantaneous modal parameters of the system are directly estimated from the coefficient in the amplitude-dependent ARX model. Finally, the proposed approach is applied to process measured data for a frame specimen subjected to a series of base excitations in shaking table tests. The specimen was damaged during testing. The identified modal parameters are consistent with observed physical phenomena.