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Now showing 1 - 8 of 8

Damage Detection of Structures Identified with Deterministic-Stochastic Models Using Seismic Data
(2014-01-01)
Huang, Ming-Chih
;
Wang, Yen-Po
;
Chang, Ming-Lian
;
土木工程學系
;
Department of Civil Engineering
A deterministic-stochastic subspace identification method is adopted and experimentally verified in this study to identify the equivalent single-input-multiple-output system parameters of the discrete-time state equation. The method of damage locating vector (DLV) is then considered for damage detection. A series of shaking table tests using a five-storey steel frame has been conducted. Both single and multiple damage conditions at various locations have been considered. In the system identification analysis, either full or partial observation conditions have been taken into account. It has been shown that the damaged stories can be identified from global responses of the structure to earthquakes if sufficiently observed. In addition to detecting damage(s) with respect to the intact structure, identification of new or extended damages of the as-damaged counterpart has also been studied. This study gives further insights into the scheme in terms of effectiveness, robustness, and limitation for damage localization of frame systems.
Identifications of symmetric ductile braced structure by pseudo-single-degree-of-freedom procedure
(2014-08-01)
Huang, Ming-Chih
;
Wang, Yen-Po
;
Lin, Tzu-Kang
;
Wang, Jer-Fu
;
土木工程學系
For energy-dissipation devices, identification of the physical behavior is a more difficult task than their design. This study develops an identification technique that is useful for the acquirement of the dynamic characteristics of buildings with symmetric ductile braces (SDBs) which exhibit bilinear behavior. The considered system is a linear multi-story building with SDBs regarded as a bilinear hysteretic model. The complex multi-degree-of-freedom problem was solved in the pseudo-single-degree-of-freedom domain, and the dynamic parameters of primary building as well as the SDBs are sequentially identified from top to bottom stories based on the input and output responses of floors. To simplify the nonlinear problem, a backbone curve, where the multi-values restoring force is transformed into a single-valued function, is applied to characterize the hysteretic model. A numerical study demonstrates that the proposed identification technique was able to extract the physical parameters of the primary building and the SDBs individually from the floor responses. It may be applied to the health monitoring of buildings protected by nonlinear energy-dissipation devices.
Damage identification of isolators in base-isolated torsionally coupled buildings
(2013-04-01)
Wang, Jer-Fu
;
Huang, Ming-Chih
;
Lin, Chi-Chang
;
Lin, Tzu-Kang
;
土木工程學系
This paper deals with the damage assessment for isolators of base-isolated building systems considering the torsion-coupling (TC) effect by establishing damage indices. The damage indices can indicate the reduction in lateral stiffness of the isolator story as explicit formulas in terms of modal parameters. In addition, the damage location, expressed in terms of the estimated damage index and eccentricities before and after damage, is also presented. Numerical analysis shows that the proposed algorithms are applicable for general base-isolated multi-story TC buildings. A procedure from the analysis of seismic response to the implementation of damage indices is demonstrated by using a numerical case. A system identification technique is employed to extract modal parameters from seismic responses of a building. Results show that the proposed indices are capable of detecting the occurrence of damage and preliminarily estimating the location of damaged isolator.
Development of physical-parameter identification procedure for in-situ buildings with sliding-type isolation system
(2013-06-24)
Huang, Ming-Chih
;
Wang, Yen-Po
;
Lin, Tzu-Kang
;
Chen, Yi-Hsuan
;
土木工程學系
A system identification procedure is developed to identify the physical parameters of structures with seismic isolation using the friction pendulum systems (FPSs). The superstructure is assumed to be linear on account of substantial reduction of seismic forces with the installation of FPS. Hysteretic models of both Coulomb's and Mokha's friction mechanism have been considered for the FPS. Simulation results indicate that the physical parameters of the FPS and superstructure can be successfully identified by the proposed scheme. Experimental verification has been conducted further via shaking table tests using realistic earthquake scenarios. The identified parameters from seismic response data indicate that the FPSs behave in better agreement with Mokha's friction mechanism than Coulomb's. Feasibility of the proposed scheme in the identification of FPS-isolated structures using seismic data has been verified. This may facilitate in-situ performance assessment of structures isolated with sliding-type isolation systems. (C) 2013 Elsevier Ltd. All rights reserved.
A Bandwidth Efficient Pairing Strategy for the MIMO-OFDM Based WLANs
(2009)
Lee, Tsern-Huei
;
Hsieh, Jing-Rong
;
Huang, Ming-Chih
;
Huang, Yu-Wen
;
電信工程研究所
The advanced MIMO (multiple-input multiple-output) system can provide higher capacity gain or higher diversity gain in modern wireless networks. The capacity gain is achieved by interference cancelation technique to fully utilize the spatial degree of freedom. In a multiuser wireless system, the increased degrees of freedom provide the chance to select multiple wireless stations (STAs) to maximize the throughput. In this paper, we consider a scenario where the access point (AP) equipped with two antennas to simultaneously communicate with two STAs, each with single antenna. After obtaining the statuses of the size of buffered traffic and the achievable transmission rate, the AP should pair compatible STAs to minimize the loss of spatial degree of freedom. Therefore, three pairing algorithms are proposed and are evaluated through computer simulations. The algorithms have much less implementation complexity than the brute force pairing algorithm and achieve satisfactory performance of throughput.
Bridge scour evaluation based on ambient vibration
(2012-09-01)
Lin, Tzu-Kang
;
Wang, Yen-Po
;
Huang, Ming-Chih
;
Tsai, Chen-An
;
土木工程學系
The vulnerability of bridges to hazards such as earthquakes, wind and floods necessitates special structural characteristics. To guarantee the stability of bridge structures, the precise evaluation of the scour depth of bridge foundation has recently become an important issue, as most of the unexpected damage to or collapse of bridges has been attributed to hydraulic issues. In this paper, a vibration-based bridge health monitoring system that utilizes only the response of superstructure to rapidly evaluate the embedded depth of a bridge column is proposed. To clarify the complex fluid-solid coupling phenomenon, the effects of embedded depth and water level were first verified through a series of static experiments. A confined finite element model simulated by soil spring effects was then established to illustrate the relationship between the fundamental frequency and the embedded depth. Using the proposed algorithm, the health of the bridge is able to be inferred by processing the ambient vibration response of the superstructure. To implement the proposed algorithm, a SHM prototype system monitoring environmental factors such as temperature, water level, and inclination was developed to support on-line processing. The performance of the proposed system was verified by a series of dynamic bridge scour experiments conducted in a laboratory flume and compared with readings from a water-proof camera. The results showed that using the proposed vibration-based bridge health monitoring system, the embedded depth of bridge column during complex scour processes is able to be reliably calculated.
Physical system identification of an isolated bridge using seismic response data
(2009-03-01)
Huang, Ming-Chih
;
Wang, Yen-Po
;
Chang', Jer-Rong
;
Chien, Chia-Shang Chang
;
土木工程學系
This paper develops a system identification process based on seismic response data to investigate the physical parameters of an isolated highway bridge equipped with the lead-rubber bearings (LRBs). The effects of soil-structure interaction (SSI) of the highway bridge built on pile foundations are taken into account in the analysis. Unlike many other identification methods that generally seek for the equivalent system parameters or modal parameters of the target structure, the proposed method aims at identifying physical parameters such as the pier stiffness or hysteresis of the LRB that are considered more critical and useful for health monitoring of bridges. In this study, a linear elastic model is used for the pier while a bilinear model is considered to characterize the hysteretic behavior of the LRB. The bilinear hysteretic model is in turn reduced to a backbone curve based on the Masing criterion by which the multi-valued restoring force is transformed into a single-valued function so that the computational effort of the identification process can be minimized. Numerical examples have been conducted, including the identification of Bai-Ho Bridge, which is the first seismic isolation bridge in Taiwan, to demonstrate the feasibility of the proposed technique for dynamic systems with inelastic components and SSL Copyright (C) 2008 John Wiley & Sons, Ltd.
Physical-Parameter Identification of Base-Isolated Buildings Using Backbone Curves
(2009-09-01)
Huang, Ming-Chih
;
Wang, Yen-Po
;
Chang, Jer-Rong
;
Chen, Yi-Hsuan
;
土木工程學系
In this paper, a simplified system identification procedure is developed to investigate the dynamic characteristics of base-isolated buildings equipped with lead-rubber bearings (LRBs). The multistory superstructure is assumed to be linear on the account of substantial reduction in seismic forces due to the installation of LRBs for which a bilinear hysteretic model is considered. The hysteretic model is in turn characterized by a backbone curve by which the multivalued restoring force is transformed into a single-valued function. With the introduction of backbone curves, the system identification analysis of inelastic structures is simplified to a large extent. The proposed algorithm extracts individually the physical parameters of each floor and the bearing system that are considered useful information in the structural health monitoring. A numerical example is conducted to demonstrate the feasibility of using the proposed technique for physical-parameter identification of partially inelastic based-isolated buildings.

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