• Journal of Korean Society of Steel Construction
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• v.29 no.3
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• pp.229-236
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• 2017

The purpose of this study is to investigate the behavior and characteristics of rubber springs and calculate the compressive stiffness by performing dynamic compression tests of rubber springs. In order to carry out the dynamic compression test of rubber spring, total 9 rubber springs were tailored by calculating the shape factor of L80-D55, L90-D58, and L100-D60, and used for the experiments. Experiments were performed by controlling the compression according to the length of the rubber spring, and the compression was increased in the order of 5%, 10%, 15%, 20% and 25% of the strain. From the experimental results, the force-strain curves were obtained and it was confirmed that strength decrease and strength increase phenomenon occurred as the strain increased. In addition, it was confirmed that the decrease of stiffness and the increase of stiffness were clearly observed according to the size and diameter of the rubber spring, and the effective compression stiffness was estimated using the slope of the force-strain curve. By using the effective compressive stiffness, design values that can be used in actual design were presented.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.335-343
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• 2003

In the previous experimental study, it is verified that the ultimate strain of concrete (${\varepsilon}$$_{cu}$=0.003) and coefficient of equivalent stress block (${\beta}$$_1$) can be used for the analysis of RC beams under biaxial and uniaxial bending moment. However, the characteristics of stress distribution of non rectangular compressed area in the RC columns are different to those of rectangular compressed area. The properties of compressive stress distribution of concrete have minor effect on the pure bending moment such as beams, but for the columns subjected to combined axial load and biaxial bending moment, the properties of compressive stress distribution are influencing factors. Nevertheless, in ACI 318-99 code, the design tables for columns subjected to axial loads with bidirectional eccentricities are based on the parameters recommended for rectangular stress block(RSB) of rectangular compressed areas. In this study the characteristics of stress distribution through both angle and depth of neutral axis are observed and formulated rationally. And the modified parameters of rectangular stress block(MRSB) for non rectangular compressed area is proposed. And the computer program using MRSB for the biaxial bending analysis of RC columns is developed and the results of MRSB are compared to RSB and experimental results respectively.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.263-270
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• 2016

Corrosion resistance steel has been widely used for port and offshore structures exposed to harsh coastal and oceanic environments, due to lower corrosion rate. New higher strength corrosion resistance steel tubes named STKM500 in KS D 3300 were recently developed by domestic technology and expected to replace foreign ASTM A690 steel. In this study, tensile test results are included to show higher yield and tensile strength of STKM500. Then, buckling test results obtained from 2m, 6m, and 12m steel tubes are demonstrated, based on which an allowable axial compressive stress curve for STKM500 steel tubes is suggested.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.5
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• pp.509-520
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• 2003

In this paper, we developed a new and robust algorithm for a practical and very efficient MPEG-4 video coding. The MPEG-4 video group has developed the video Verification Model(VM) which evolved through time by means of core experiments. And in the standardization process, MS-FDAM was developed based on the standard document of ISO/IEC 14496-2 and VM as a reference MPEG-4 coding system. But MS -FDAM has drawbacks in practical MPEG-4 coding and it does not have the VOP extraction functionality. In this research, we implemented a preprocessing system for a real-time input and the VOP extraction for a practical content-based MPEG-4 video coding and also implemented the motion detection to achieve the high compression rate of 180:1.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.331-340
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• 2011

The application of newly developed fiber-sheet and steel-plate composite plate (FSP) as a means of improving strength and ductility capacity of concrete cylinders under axial compression load through confinement is investigated experimentally in this study. An experimental investigation involves axial load tests of two types of FSP strengthening material, two anchoring methods, and three concrete strengths. The FSP-confined cylinder tests showed that FSP provided a substantial gain in compressive strength and deformability. The performance of FRP-confined cylinders was influenced by type of the FSP strengthening material, the anchoring method, and concrete compressive strength. The FSP failure strains obtained from FSP-confined cylinder tests were higher than those from FRP-confined cylinder tests. The magnitude of FSP failure strain was related to the FSP composite effectiveness. The effects of FSP confinement on the concrete microstructure were examined by evaluating the internal concrete damage using axial, radial, and volumetric strains. From the observations obtained in this investigation, it is believed that FSP is one of the best solutions for the confinement of concrete compressive members.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.501-509
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• 2004

The proposed model can predict the compressive behaviors of concrete confined with fiber reinforced polymer (FRP) jacket. To model confining concrete by FRP jackets, the hypoelasticity-based constitutive law of concrete In tri-axial stress states has been presented. The increment of strength of concrete has been determined by the failure surface of concrete in tri-axial states, and its corresponding peak strain is computed by the strain enhancement factor that is proposed in the present study, Therefore, the newly proposed model is a load-dependent confinement model of concrete wrapped by FRP jackets to compare the previous models which are load-independent confinement models. The behavior of FRP jackets has been modeled using the mechanics of orthotropic laminated composite materials in two-dimension. The developed model is implemented into the incremental analysis of compressive tests. The verification study with several different experiments shows that the model is able to adequately capture the behavior of the compression test by including better estimations of the axial responses as well as the lateral response of FRP-confined concrete cylinders.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.45-52
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• 2005

The object of this study was a cold-formed steel wall stud panel sheathed by gypsum boards. In the beam-analysis, the panel was treated as a simple beam with a uniform lateral loading. The deflections were calculated by considering the primary factors that reduced the stiffness of the panel. In the column-analysis, the panel was treated as a bearing wall with an axial load. By using an energy method, nominal axial strength could be evaluated by considering both flexural buckling and torsional-flexural buckling. All calculations were programmed and compared with the results of the experiment. In the beam-analysis, experimental deflections were close to theoretical deflections. In the column-analysis, the experimental values were also close to theoretical values in axial strength.

• Journal of Korean Society of Steel Construction
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• v.29 no.2
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• pp.147-158
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• 2017

The present study focused on the structural performance of newly developed prefabricated composite columns (PSRC composite column) using bolt-connected steel angles. Concentric axial loading tests were performed for four 2/3 scaled PSRC column specimens and two conventional SRC column specimens. The test parameters were the spacing and sectional configurations of lateral reinforcement, and width-to-thickness ratio of steel angles. The test results showed that the axial load-carrying capacity and deformation capacity of the PSRC column specimens were comparable to those of the conventional SRC column specimens. Closely spaced steel plates and Z-shaped steel plates for lateral reinforcement increased the deformation capacity of the PSRC column specimens. The load-carrying capacity was greater than the prediction by current design codes. Numerical analysis was performed for the specimens. The results agreed well with the test results in terms of initial stiffness, load-carrying capacity, except for strength degradation due to cover concrete spalling.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.2
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• pp.84-90
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• 1997

The turboshaft engine with the free power turbine has been used for various purposes, for instance electric power generator, emergency power source, helicopter powerplant and so on. Steady-state simulation program was developed and experimental tests was carried out for comparing with computer simulation results. The test unit was composed of 1-stage centrifugal compressor, the can type combustor chamber, 1-stage radial type compressor turbine, and radial type free power turbine, and its output power is obtained from 3-phase AC generator. Main component characteristics which was used for the steady state simulation program, were obtained from the manufacturer of the test unit, and modified from experimental results of test unit. In comparison between computer simulation and experimental test results even though the test unit has the operational limit, deviation of component performance characteristics in simulation were within 6％ range of experimental results.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.311-320
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• 2009

This paper presents the experimental results of an experiment on the current rectangular CFT columns and rectangular CFT columns additionally confined by carbon fiber sheets(CFS) under axial loading. The main experimental parameters were the layer numbers of the CFS and the depth-to-thickness ratio. Nine specimens were prepared according to the experimental parameter plans, and axial compression tests were conducted. From the tests, the failure procedure, the load-axial deformation curve, the maximum axial strength, and the deformation capacity of the CFT columns and the confined CFT columns were compared. Finally, it was seen that the maximum axial strengths of the CFT increased more significantly than that of the current CFT columns because of delayed local buckling.