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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Earthquake Engineering Society of Korea
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Journal DOI :
Earthquake Engineering Society of Korea
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Volume & Issues
Volume 9, Issue 6 - Dec 2005
Volume 9, Issue 5 - Oct 2005
Volume 9, Issue 4 - Aug 2005
Volume 9, Issue 3 - Jun 2005
Volume 9, Issue 2 - Apr 2005
Volume 9, Issue 1 - Feb 2005
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Performance Evaluation of MR Damper using Equivalent Linearization Technique
Lee, Sang-Hyun ; Min, Kyung-Won ; Lee, Myoung-Kyu ;
Journal of the Earthquake Engineering Society of Korea, volume 9, issue 2, 2005, Pages 1~6
DOI : 10.5000/EESK.2005.9.2.001
The purpose of this paper is to evaluate the performance of an MR fluid damper for seismic vibration control of a structure in terms of equivalent linear damping based on linearization technique and to experimentally verify the results from linearization technique by comparing them to those from system identification testing of a building structure with the MR damper. First, among various models for the MR damper, the equivalent damping is estimated for the Bingham model which is mathematically simple. Second, the transfer function of a building structure with the MR damper is obtained by performing shaking table tests and the damping matrices of the structure are constructed using the modal information obtained by the transfer function. It is observed that the damping mathematically estimated using linearization technique for the Bingham model matches well with the damping coefficient experimentally obtained by system identification.
Numerical Study of Hybrid Base-isolator with Magnetorheological Damper and Friction Pendulum System
Kim, Hyun-Su ; Roschke, P.N. ;
Journal of the Earthquake Engineering Society of Korea, volume 9, issue 2, 2005, Pages 7~15
DOI : 10.5000/EESK.2005.9.2.007
Numerical analysis model is proposed to predict the dynamic behavior of a single-degree-of-freedom structure that is equipped with hybrid base isolation system. Hybrid base isolation system is composed of friction pendulum systems (FPS) and a magnetorheological (MR) damper. A neuro-fuzzy model is used to represent dynamic behavior of the MR damper. Fuzzy model of the MR damper is trained by ANFIS (Adaptive Neuro-Fuzzy Inference System) using various displacement, velocity, and voltage combinations that are obtained from a series of performance tests. Modelling of the FPS is carried out with a nonlinear analytical equation that is derived in this study and neuro-fuzzy training. Fuzzy logic controller is employed to control the command voltage that is sent to MR damper. The dynamic responses of experimental structure subjected to various earthquake excitations are compared with numerically simulated results using neuro-fuzzy modeling method. Numerical simulation using neuro-fuzzy models of the MR damper and FPS predict response of the hybrid base isolation system very well.
Integrated Optimum Design and Cost Effectiveness Evaluation of Viscoelastically Damped Building Structures based on Life-Cycle Cost Minimization
Park, Kwan-Soon ; Hahm, Dae-Gi ; Koh, Hyun-Moo ;
Journal of the Earthquake Engineering Society of Korea, volume 9, issue 2, 2005, Pages 17~27
DOI : 10.5000/EESK.2005.9.2.017
This paper presents an integrated optimum design and a cost effectiveness evaluation method of a viscoelastically damped structural system. The criterion selected for the optimization is the minimization of the life?cycle cost which is a function of structural sizing variables and the amount of the viscoelastic damper. A genetic algorithm is used as a numerical searching technique in order to simultaneously find the optimum parameters of the integrated system. Optimal distributions of design variables according to various seismic characteristics are investigated by applying the proposed design method to a numerical example of a 10?story building structure. The cost effectiveness of viscoelastically damped structural system is also evaluated by comparing the life-cycle cost of the structure without viscoelastic dampers. The results show that the viscoelastic damper is effective in a region of low to moderate seismicity.
Analytical Study on Inelastic Behavior of RC Bridge Columns with Unbonding of Main Reinforcements at Plastic Hinge Region
Kim, Tae-Hoon ; Shin, Hyun-Mock ;
Journal of the Earthquake Engineering Society of Korea, volume 9, issue 2, 2005, Pages 29~36
DOI : 10.5000/EESK.2005.9.2.029
The purpose of this study is to investigate the inelastic behavior of reinforced concrete bridge columns with unbonding of main reinforcements at plastic hinge region. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. The effect of unbonding of main reinforcements at plastic hinge region has been also taken into account to model the concrete and reinforcing steel. The proposed numerical method for the inelastic behavior of reinforced concrete bridge columns with unbonding of main reinforcements at plastic hinge region is verified by comparison with reliable experimental results.
Fuzzy Control of Smart Base Isolation System using Genetic Algorithm
Kim, Hyun-Su ; Roschke, P.N. ;
Journal of the Earthquake Engineering Society of Korea, volume 9, issue 2, 2005, Pages 37~46
DOI : 10.5000/EESK.2005.9.2.037
To date, many viable smart base isolation systems have been proposed and investigated. In this study, a novel friction pendulum system (FPS) and an MR damper are employed as the isolator and supplemental damping device, respectively, of the smart base isolation system. A fuzzy logic controller (FLC) is used to modulate the MR damper because the FLC has an inherent robustness and ability to handle non linearities and uncertainties. A genetic algorithm (GA) is used for optimization of the FLC. The main purpose of employing a GA is to determine appropriate fuzzy control rules as well to adjust parameters of the membership functions. To this end, a GA with a local improvement mechanism is applied. This method is efficient in improving local portions of chromosomes. Neuro fuzzy models are used to represent dynamic behavior of the MR damper and FPS. Effectiveness of the proposed method for optimal design of the FLC is judged based on computed responses to several historical earthquakes. It has been shown that the proposed method can find optimal fuzzy rules and the GA optimized FLC outperforms not only a passive control strategy but also a human designed FLC and a conventional semi active control algorithm.
Seismic Response Analysis of a Floating Bridge with Discrete Pontoons
Kwon, Jang-Sup ;
Journal of the Earthquake Engineering Society of Korea, volume 9, issue 2, 2005, Pages 47~58
DOI : 10.5000/EESK.2005.9.2.047
Dynamic response analysis in time dimain is conducted for floating bridges with discrete pontoons subject to spatial variation of ground motions. The Spatial variation of ground motions is considered with the coherency function model which represents wave passage, incoherence and local site effects. The superstructure of the bridge is represented by space frame and elastic catenary cable elements, the abutment us modelde with the spring element of FHWA guideline for considering soil structure interaction and the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients which are obtainde by boundary element method. multiple support excitations considering the spatial variation. The noticeable amplification of the response can be shown when the spatial variation of ground motions is incorporated in the anallysis of floating bridges.
Re-evaluation of Force Transfer Mechanism of Welded Steel Moment Connections
Lee, Choel-Ho ;
Journal of the Earthquake Engineering Society of Korea, volume 9, issue 2, 2005, Pages 59~69
DOI : 10.5000/EESK.2005.9.2.059
Employing the classical beam theory for the design of welded steel moment connections has been brought into question by several researchers since the 1994 Northridge earthquake. In this study, the load transfer mechanism in various welded steel moment connections is comprehensively reviewed mainly based on recent studies conducted by the writer. Available analytical and experimental results showed that the load path in almost all the welded steel moment connections is completely different from that as predicted by the classical beam theory. Vertical plates near the connection such as the beam web, the web of the straight haunch, and the rib act as a strut rather than following the classical beam theory. The shear force transfer in the RBS connection is essentially the same as that in PN type connection. Some simplified analytical models that can be used as the basis of a practical design procedure are also presented.
Nonlinear Liquid Sloshing Analysis in a Cylindrical Container by Arbitrary Lagrangian-Eulerian Approach
Kwon, Hyung-O ; Cho, Kyung-Hwan ; Kim, Moon-Kyum ; Lim, Yun-Mook ;
Journal of the Earthquake Engineering Society of Korea, volume 9, issue 2, 2005, Pages 71~80
DOI : 10.5000/EESK.2005.9.2.071
The solution to a liquid sloshing problem is challenge to the field of engineering. This is not only because the dynamic boundary condition at the free surface is nonlinear, but also because the position of the free surface varies with time in a manner not known a priori. Therefore, this nonlinear phenomenon, which is characterized by the oscillation of the unrestrained free surface of the fluid, is a difficult mathematical problem to solve numerically and analytically. In this study, three-dimensional boundary element method(BEM), which is based on the so-called an arbitrary Lagrangian-Eulerian(ALE) approach for the fluid flow problems with a free surface, was formulated to solve the behavior of the nonlinear free surface motion. An ALE-BEM has the advantage to track the free surface along any prescribed paths by using only one displacement variable, even for a three-dimensional problem. Also, some numerical examples were presented to demonstrate the validity and the applicability of the developed procedure.