Browsing by Author "Wang, Yen-Po"

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A study on AGV-induced floor micro-vibration in TFT-LCD high-technology fabs
(2012-04-01)
Lee, Chien-Liang
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Wang, Yen-Po
;
Su, Ray Kai Leung
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土木工程學系
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Department of Civil Engineering
This study explores vertical floor micro-vibration induced by the automated guided vehicles (AGVs) in thin-film-transistor liquid-crystal-display (TFT-LCD) fabs. The state-space procedure is adopted to compute the AGV-induced floor vibration as it preserves the desired numerical stability and accuracy in high-frequency responses. The dynamic analysis of an AGV moving on an equivalent three-span beam model of a TFT-LCD building is simulated by taking into account various AGV speeds and engine forces. Numerical simulations demonstrate that if proper engine forces and excitation frequency contents of the AGV moving loads are used, the peak AGV-induced floor micro-vibration level can be predicted by the proposed method. Moreover, the effectiveness of vibration control by span-reduction as well as energy-dissipation by viscoelastic dampers is also examined. In comparison with span-reduction, application of energy-dissipation devices is more effective in vibration suppression as they enhance the damping characteristics of the multi-span floor system whose natural frequencies are potentially in resonance with the excitation frequencies of the AGV moving loads ranging in a broad bandwidth. Copyright (C) 2011 John Wiley & Sons, Ltd.
A study on using pre-bent steel strips as seismic energy-dissipative devices
(2009-07-10)
Wang, Yen-Po
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Chien, Chia-Shang Chang
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土木工程學系
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Department of Civil Engineering
Buckling is usually conceived as an unstable Structural behavior leading to lateral instability of axially loaded members, if not properly supported. However, a pre-bent strip Would become an excellent seismic energy-dissipative device it it is deformed in a guided direction and ratio, e. Geometrically large lateral deformation of the steel strips in buckling leads to inelastic behavior of the material and dissipates energy as a consequence. The purpose of this study is to propose a new type of seismic damper in the form of braces based on pre-bent steel strips. The nonlinear elastic stiffness of monotonously loaded pre-bent strips in both compression and tension is derived. The energy-dissipative characteristics of the proposed damping device are investigated via component tests under cyclic loads. Experimental results indicate that the force-displacement relationship of pre-bent strips in cyclic loads exhibits mechanical characteristics of displacement-dependent dampers. A series of seismic performance tests has been conducted further to verify the feasibility and effectiveness of using the proposed device as seismic dampers. Encouraging test results have been obtained, suggesting feasibility of the proposed device for earthquake-resistant design. Copyright (C) 2008 John Wiley & Sons, Ltd.
An Experimental Study of DLV Method in Damage Detection of Frame Structures
(2010)
Wang, Yen-Po
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Chen, Yi-Hsuan
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Lee, Chien-Liang
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土木工程學系
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Department of Civil Engineering
A structural damage detection method integrating the damage locating vector (DLV) method and ARX model for system identification of frame structures from seismic acceleration responses has been explored in this paper. The concept of the DLV method is to identify the members with zero stress under some specific loading patterns derived from the changes in flexibility matrix of the structure before and after the damage state. Success of the DLV method requires clear identification of the flexibility matrix for at least the first few dominant modes. In this study, a five-storey steel frame with diagonal bracings is considered as the objective building. The damage condition of the structure is simulated by partially removing some of the diagonals. With the flexibility matrices of both the intact and damaged structure identified from seismic structural responses via shaking table tests, results indicate that the damaged locations can be successfully identified by the DLV method if sufficient modes of vibration are taken into account in the realization of the flexibility matrices. The feasibility of using DLV method for damage detection of frame structures using seismic response data is confirmed.
An experimental study of in-plane arch-shaped dampers
(2018-10-01)
Lee, Chien-Liang
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Wang, Yen-Po
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Cai, Meng-Yan
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土木工程學系
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Department of Civil Engineering
As an effort to minimize material utilization, seismic steel dampers designed to deform inelastically in an in-plane flexural mode have attracted serious attention recently. This paper presents a new type of metallic yielding damper referred to as the in-plane arch-shaped damper modified from its portal frame-shaped counterpart by replacing the straight beam with a circular arch to minimize the effects of stress concentration and warping, and therefore to avoid premature failure. Component tests of both the portal frame-shaped and arch-shaped in-plane dampers were conducted for comparison. Hysteresis loops obtained from the component tests under cyclic loads indicate substantial improvement on the energy-dissipative characteristics of the proposed damper. Moreover, seismic performance assessment of the proposed damper was carried out further via shaking table tests of a five-story model frame. Encouraging results have been achieved in terms of acceleration reduction, damping enhancement and peak suppression of the frequency response functions, suggesting the potential of the proposed device to be used in earthquake-resisting systems.
Assessment of vibrations induced in factories by automated guided vehicles
(2013-04-01)
Lee, Chien-Liang
;
Wang, Yen-Po
;
Su, Ray Kai Leung
;
土木工程學系
;
Department of Civil Engineering
This study proposes a simplified sub-structural model to explore the floor micro-vibration induced by automated guided vehicles in thin-film transistor liquid crystal display factories. Time history analyses of a sequence of automated guided vehicles moving loads considering various car spacings on an equivalent three-span continuous beam model of a thin-film transitor liquid crystal display factory were simulated. The effectiveness of vibration control using viscoelastic dampers was also examined. Numerical simulations demonstrate that the simplified method can predict the measured floor vibration spectra with satisfactory accuracy and that the automated guided vehicles induced floor vibrations without control exceed the acceptable VC-B level required for the installation of specific precision process tools. The application of energy dissipation devices has shown to be effective in vibration mitigations as they enhance the damping characteristics of a multi-span floor system. The maximum response of the whole continuous beam induced by a group of automated guided vehicles can be effectively suppressed to a desired VC-B level if multiple viscoelastic dampers are implemented along the automated guided vehicles moving bay and the spacing between each automated guided vehicle is properly adjusted. The simplified analytical method can help engineers quickly assess the level of automated guided vehicles-induced floor vibration and assist in the design of low-vibration floor systems in high-technology factories.
Bridge scour evaluation based on ambient vibration
(2012-09-01)
Lin, Tzu-Kang
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Wang, Yen-Po
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Huang, Ming-Chih
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Tsai, Chen-An
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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.
Damage Detection of Structures Identified with Deterministic-Stochastic Models Using Seismic Data
(2014-01-01)
Huang, Ming-Chih
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Wang, Yen-Po
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Chang, Ming-Lian
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土木工程學系
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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.
Damage Localization of Structures Identified with a Deterministic - Stochastic Model
(2014)
Wang, Yen-Po
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Chang, Ming-Lian
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Chang, Jia-Ge
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土木工程學系
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Department of Civil Engineering
In this study, a scheme integrated with deterministic- stochastic subspace system identification and the method of damage localization vector (DLV) is proposed for damage detection of structures based on seismic response data. A series of shaking table tests has been conducted in National Center for Research on Earthquake Engineering (NCREE), Taiwan. Damage condition is simulated by reducing the cross-sectional area of some of the columns at the bottom ends. Both single and multiple damage conditions at various locations have been considered. Full or partial observation conditions have been taken into account in the system identification analysis. It has been shown that local damages (stories) can be identified from global responses of the structure to earthquakes if sufficiently observed.
Design tables and charts for uniform and non-uniform tuned liquid column dampers in harmonic pitching motion
(2012-02-01)
Wu, Jong-Cheng
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Wang, Yen-Po
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Chen, Yi-Hsuan
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土木工程學系
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Department of Civil Engineering
In the first part of the paper, the optimal design parameters for tuned liquid column dampers (TLCD) in harmonic pitching motion were investigated. The configurations in design tables include uniform and non-uniform TLCDs with cross-sectional ratios of 0.3, 0.6, 1, 2 and 3 for the design in different situations. A closed-form solution of the structural response was used for performing numerical optimization. The results from optimization indicate that the optimal structural response always occurs when the two resonant peaks along the frequency axis are equal. The optimal frequency tuning ratio, optimal head loss coefficient, the corresponding response and other useful quantities are constructed in design tables as a guideline for practitioners. As the value of the head loss coefficient is only available through experiments, in the second part of the paper, the prediction of head loss coefficients in the form of a design chart are proposed based on a series of large scale tests in pitching base motions, aiming to ease the predicament of lacking the information of head loss for those who wishes to make designs without going through experimentation. A large extent of TLCDs with cross-sectional ratios of 0.3, 0.6, 1, 2 and 3 and orifice blocking ratios ranging from 0%, 20%, 40%, 60% to 80% were inspected by means of a closed-form solution under harmonic base motion for identification. For the convenience of practical use, the corresponding empirical formulas for predicting head loss coefficients of TLCDs in relation to the cross-sectional ratio and the orifice blocking ratio were also proposed. For supplemental information to horizontal base motion, the relation of head loss values versus blocking ratios and the corresponding empirical formulas were also presented in the end.
Development of physical-parameter identification procedure for in-situ buildings with sliding-type isolation system
(2013-06-24)
Huang, Ming-Chih
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Wang, Yen-Po
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Lin, Tzu-Kang
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Chen, Yi-Hsuan
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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.
Identifications of symmetric ductile braced structure by pseudo-single-degree-of-freedom procedure
(2014-08-01)
Huang, Ming-Chih
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Wang, Yen-Po
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Lin, Tzu-Kang
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Wang, Jer-Fu
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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.
Physical system identification of an isolated bridge using seismic response data
(2009-03-01)
Huang, Ming-Chih
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Wang, Yen-Po
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Chang', Jer-Rong
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Chien, Chia-Shang Chang
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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
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Wang, Yen-Po
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Chang, Jer-Rong
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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.
Wind-induced interaction of a non-uniform tuned liquid column damper and a structure in pitching motion
(2008-12-01)
Wu, Jong-Cheng
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Wang, Yen-Po
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Lee, Chien-Liang
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Liao, Pei-Hsuan
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Chen, Yi-Hsuan
Wind-induced interaction between a tuned liquid column damper (TLCD) and a structure (bridge deck) in pitching motion is investigated both theoretically and experimentally. Non-uniform cross-sections in TLCDs are considered in general. Theoretically, the interacted equations of motion under wind excitation were derived for a single-degree-of-freedom rotational structure equipped with a TLCD based on energy principles. An addition term, which had never been revealed in existing literature, was discovered. The second part in this study was to demonstrate the existence of this additional term through experimental verification. This task was carried out by conducting large scale tests on the system of a TLCD on a rotational structure (which is a spring-constrained steel beam pivoted at mid-span) and by making comparisons between the experimental and analytical responses of the interacted structure subjected to harmonic loading. To obtain all necessary parameters for computing the analytical responses in the interaction, the individual identification of the properties of the TLCD and structure using free vibration and forced vibration techniques was also performed. Comparison results show that analytical responses with the additional term included can represent the actual interaction more closely than those without the additional term. Therefore, the inclusion of the additional term in pitching interaction equations is essential. (C) 2008 Elsevier Ltd. All rights reserved.