• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.190-195
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• 2001

In the present paper computational simulation of a concrete dam is performed to determine the effect of vertical ground motions on earthquake response of concrete dams. Cyclic and dynamic versions of the plastic-damage model proposed by Lee and Fenves are used to represent micro-crack development and crack opening/closing, which is important mechanism in nonlinear damage analysis of concrete structures subject to strong earthquake loading. The result shows that the vertical component of ground motion effects on final crack patterns and consequently, on displacement response.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.371.1-371
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• 1999

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.1
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• pp.27-33
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• 2005

In this study, the process parameters in ceramics powder compaction are optimized for getting high relative densities of ceramic products. To find optimized parameters, the analytic models of powder compaction are firstly prepared by 2-dimensional rod arrays with random green densities using a quasi-random multiparticle array. Then, using finite element method, the changes in relative densities are analyzed by varying the size of Al₂O₃ particle, the amplitude of cyclic compaction, and the coefficient of friction, which influence the relative density in cyclic compactions. After the analytic function of relative density associated process parameters are formulated by aid of the response surface method, the optimal conditions in powder compaction process are found by the grid search method. When the particle size of Al₂O₃ is 22.5 ㎛, the optimal parameters for the amplitude of cyclic compaction and the coefficient of friction are 75 MPa and 0.1103, respectively. The maximum relative density is 0.9390.

• Structural Engineering and Mechanics
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• v.35 no.1
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• pp.99-117
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• 2010

Beam-column joints are the key structural elements, which dictate the behavior of structures subjected to earthquake loading. Though large experimental work has been conducted in the past, still various issues regarding the post-yield behavior, ductility and failure modes of the joints make it a highly important research topic. This paper presents experimental results obtained for eight beam-column joints of different sizes and configuration under cyclic loads along with the analytical evaluation of their response using a simple and effective analytical procedure based on nonlinear static pushover analysis. It is shown that even the simplified analysis can predict, to a good extent, the behavior of the joints by giving the important information on both strength and ductility of the joints and can even be used for prediction of failure modes. The results for four interior and four exterior joints are presented. One confined and one unconfined joint for each configuration were tested and analyzed. The experimental and analytical results are presented in the form of load-deflection. Analytical plots are compared with envelope of experimentally obtained hysteretic loops for the joints. The behavior of various joints under cyclic loads is carefully examined and presented. It is also shown that the procedure described can be effectively utilized to analytically gather the information on behavior of joints.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.663-672
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• 2014

Recently, modular structural systems have been applicable to building construction since they can significantly reduce building construction time. They consists of several unit modular frames of which each beam-column joint employs an access hole for connecting unit modular frames. Their structural design is usually carried out under the assumption that their load-carrying mechanism is similar to that of a traditional steel moment-resisting system. In order to obtain the validation of this assumption, the cyclic characteristics of beam-column joints in a unit modular frame should be investigate. This study carried out finite element analyses(FEM) of unit modular frames to investigate the cyclic behavior of beam-column joints with the structural influence of access holes. Analysis results show that the unit modular frames present stable cyclic response with large deformation capacities and their joints are classified into partial moment connections. Also, this study develops a simple spring model for earthquake nonlinear analyses and suggests the Ramberg-Osgood hysteretic rule to capture the cyclic response of unit modular frames.

• Journal of the Korean Geotechnical Society
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• v.35 no.6
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• pp.5-15
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• 2019

Usually, the cyclic shear stress ratio (CSR) for the assessment of liquefaction has been determined by performing ground response analysis or adopting simplified method suggested by Seed & Idriss with some modifications. In order to analyze the applicability of the CSR evaluation methods, the present study performed one-dimensional equivalent linear analysis and evaluated CSR based on design codes from FHWA, JRA, and KDS. The comparison of the CSR obtained from each code showed that the CSR from KDS showed the largest error with the analysis results. The reason is because KDS has an error, which defines the stress reduction coefficient applying the maximum acceleration at each depth, not the maximum cyclic shear stress mobilized in the soil.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.1
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• pp.23-33
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• 1994

Liquefaction characteristics of the reclaimed marine sand deposits is studied by means of the dynamic response analysis and the cyclic triaxial compression test. 1) From the result of the dynamic response analysis. it was found that the amplification of ground surface maximum acceleration varied with input earthquake motions and soil data, and earthquake coefficients were proposed to be applicable in evaluating liquefaction potential by simplified prediction methods. 2) For upper and soft sand deposits with small N-value, liquefaction strengths estimated by Seed and Idriss's simplified method were lower than those by the cyclic triaxial test while those by Iwasaki & Tatsuoka's or Vs-method were not lower. 3) Simplified methods were inclined to overestimate liquefaction potential in comparison with the dynamic response analysis and the cyclic triaxial compression test Allowable depths of liquefaction(safety factor 1) were estimated to be 7-14m for 0.1 -0.2g of input maximum acceleration.

• Steel and Composite Structures
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• v.23 no.2
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• pp.143-152
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• 2017

This paper focuses on the seismic performance of pallet-type steel storage rack structures in their down aisle direction. As evidenced by experimental research, the seismic response of storage racks in the down-aisle direction is strongly affected by the nonlinear moment-rotation response of the beam-to-column connections. In their down-aisle direction, rack structures are designed to resist lateral seismic loads with typical moment frames utilizing proprietary beam-to-column moment-resisting connections. These connections are mostly boltless hooked type connections and they exhibit significantly large rotations resulting in large lateral frame displacements when subjected to strong ground motions. In this paper, typical hooked boltless beam-to-column connections are studied experimentally to obtain their non-linear reversed cyclic moment-rotation response. Additionally, a compound type connection involving the standard hooks and additional bolts were also tested under similar conditions. The simple introduction of the additional bolts within the hooked connection is considered to be a practical way of structural upgrade in the connection. The experimentally evaluated characteristics of the connections are compared in terms of some important performance indicators such as maximum moment and rotation capacity, change in stiffness and accumulated energy levels within the cyclic loading protocol. Finally, the obtained characteristics were used to carry out seismic performance assessment of rack frames incorporating the tested beam-to-column connections. The assessment involves a displacement based approach that utilizes a simple analytical model that captures the seismic behavior of racks in their down-aisle direction. The results of the study indicate that the proposed method of upgrading appears to be a very practical and effective way of increasing the seismic performance of hooked connections and hence the rack frames in their down-aisle direction.

• Structural Engineering and Mechanics
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• v.62 no.3
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• pp.281-289
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• 2017

Damping value has considerable influence on the dynamic and seismic behaviors of bridges. However, currently the constant damping ratios that are prescribed by most bridge seismic design codes can't truly represent the complicated damping character of actual structures. In this paper, a cyclic loading experiment was conducted to study the effect of stress amplitude on material damping of concrete to present an analyzing model of the material damping of concrete. Furthermore, based on the fundamental damping of structure measured under ambient vibration, combined with the presented stress-dependent material damping concrete, the seismic response of a bridge pier was calculated. Comparison between the calculated and experiment results verified the validity of the presented damping model. Finally, a modified design and analysis method for bridge was proposed based on stress-dependent damping theory, and a continuous rigid frame bridge was selected as the example to calculate the actual damping values and the dynamic response of the bridge under different earthquake intensities. The calculation results indicated that using the constant damping given by the Chinese seismic design code of bridges would overestimate the energy dissipation capacity of the bridge.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.350-355
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• 2008

A Rubber mount is widely used for mechanical parts or engineering materials. Especially, it plays an important role in reducing mechanical vibration due to cyclic loading. But, rubber mount is damaged due to the cyclic loading and resonance. Therefore, it is necessary to investigate evaluation of fatigue life considering vibration characteristics for rubber. In this study, a vibration fatigue analysis was performed and based on Power Spectral Density(PSD) and the stress-life curve and a result of frequency response analysis in the finite element method. The measured load history in experiment was transformed to PSD curve. The stress-life curve was obtained by nonlinear static analysis and fatigue test. In addition, frequency response analysis was conducted for mechanical part. In order to evaluate fatigue life of rubber mount, vibration fatigue test was conducted at the constant acceleration-level as well. Fatigue life was determined when the load capacity is reduced to 60% of its initial value. As a result, predicted fatigue life of rubber mount agreed fairly well with the experimental fatigue life.