• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.141-148
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• 2021

In this study, the technology to prevent lateral deformation of steel dampers was reviewed and applied to the clamp type dampers. As for the experimental method, the rocking behavior was applied as in the previous study. The evaluation variables are the existing research results (SV-260) without lateral deformation prevention details and the test results (V-1, V-1R) with lateral deformation prevention details. Where, V-1 is the lateral deformation prevention detail at the lower part of the damper, and V-1R is the lateral deformation prevention detail at the lower part and upper part of the damper. As a result of evaluating the moment, drift ratio, and energy dissipation capacity relative to SV-260 at the time of maximum load, the maximum moments of V-1 and V-1R were increased by 1.22 times and 1.36 times compared to SV-260, and the maximum drift ratio increased by 2.41 times and 2.92 times. In addition, the energy dissipation capacity also increased by 1.39 times and 1.52 times, respectively. Therefore, the application of lateral deformation prevention details to the steel damper was evaluated as appropriate.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.464-472
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• 1996

The mechanism of thin-film formation by Ionized Cluster Beam Deposition(ICBD) was investigated. A simulation program based on the Monte-Carlo method was developed in order to investigate the effects of the acceleration voltage, substrate temperature, activation energy for the surface migration, and critical nuclei size on grain size and surface roughness. Studies of the effect of kinetic energy of clusters on the film formation processes revealed that high acceleration voltage enhanced the surface-migration of adatoms and made it easier for an epitaxial film to be formed. The relaxation time of kinetic energy of adatoms increased with the substrate temperature, which in turn increased the grain size of the crystalline film. This effect was more clearly distinguished when the critical nuclei size was large. The surface-migration activation energy was found to affect the interaction between the adatoms and the substrate and thus the relaxation time of kinetic energy. Investigations of the surface roughness revealed that the acceleration voltage, the substrate temperature, and the surface-migration activation energy exerted a collective effect on the morphology of the film surface.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.151-159
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• 2015

In this study, experimental research was carried out to evaluate and improve the seismic performance of reinforced concrete beam-column joint regions using strengthening materials (CFRP sheet, AFRP sheet, embedded CFRP rod) in existing reinforced concrete structure. Therefore it was constructed and tested seven specimens retrofitting the beam-column joint regions using such retrofitting materials. Specimens, designed by retrofitting the beam-column joint regions of existing reinforced concrete structure, were showed the stable failure mode and increase of load-carrying capacity due to the effect of crack control at the times of initial loading and confinement of retrofitting materials during testing. Specimens LBCJ-CRUS, designed by the retrofitting of CFRP Rod and CFRP Sheet in reinforecd beam-column joint regions were increased its maximum load carrying capacity by 1.54 times and its energy dissipation capacity by 2.36 times in comparison with standard specimen LBCJ for a displacement ductility of 4 and 7. And Specimens LBCJ-CS, LBCJ-AF series were increased its energy dissipation capacity each by 2.04~2.34, 1.63~3.02 times in comparison with standard specimen LBCJ for a displacement ductility of 7.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.91-96
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• 2007

To improve the land use of urban, Construction of the circular steel column is required recently. The circular steel columns have a advantage for improving a load carrying capacity as wall as reducing a effective section area. However, the circular steel columns under service load, such as earthquake, shows a tendency to cause local buckling and large deformation. To prevent these phenomena, use of diaphragm is considered. It is reported that longitudinal stiffeners has a effect on improving a buckling and fatigue performance of steel structures. The research of effect on diaphragm is not sufficient. Under monotonic and cyclic loadings diaphragm make a important role to prevent local buckling and deformation of used steel structures. Therefore, influence of diaphragm on performance of used steel structures is investigated. In this study, the influence of diaphragm on seismic and deformation performance of circular steel piers was investigated by using elastic-plastic finite element analysis considered geometrical and material non-linearity. The seismic performance of circular steel columns was evaluated for analytical parameter of manufactured part. The seismic performance of circular steel columns was clarified by comparing an energy dissipation of circular steel piers.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.160-169
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• 2015

In this study, experimental research was carried out to improve the seismic performance of reinforced concrete exterior beam-column joint regions using replacing recycled coarse aggregate with hybrid fiber (steel fiber+PVA fiber) in existing reinforced concrete building. Therefore it was constructed and tested seven specimens retrofitting the beam-column joint regions using such retrofitting materials. Specimens, designed by retrofitting the beam-column joint regions of reinforced concrete building, were showed the stable failure mode and increase of load-carrying capacity due to the effect of crack control at the times of initial loading and bridge of retrofitting hybrid fiber during testing. Specimens BCJGPSR series, designed by the retrofitting of replacing recycled coarse aggregate with hybrid fiber in reinforecd beam-column joint regions were increased its maximum load carrying capacity by 1.01~1.04 times and its energy dissipation capacity by 1.06~1.29 times in comparison with standard specimen BCJS. Also, specimen $BCJGPSR_1$ were increased its energy dissipation capacity by 1.33~1.65 times in comparison with specimens BCJS, BCJP and BCJGPR series for a displacement ductility of 9.

• Journal of computational fluids engineering
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• v.6 no.1
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• pp.31-39
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• 2001

연소실 안으로 분출되는 스월 유동의 vortex breakdown mechanism에 대한 연구를 하였다. 3차원 유한 체적기법과 Runge-Kutta 시간 적분법이 적용되었으며, 난류모델은 dynamic large eddy simulation (DLES)이 적용되었다. 계산 시간의 효율성과 기억용량을 효과적으로 사용하기 위하여 message passing interface (MPI) 병렬계산 기법이 적용되었다. 스월 난류 유동에 있어서 vortex breakdown 거동을 가시적으로 표착 하였는데, 이는 스월 유동에 의한 난류 응력 증대, 난류 생성/소산율 증대 및 혼합율 증대에 대한 실험적 근거를 뒷받침하는 매우 중요한 결과이다. 또한 평균 속도와 난류 운동에너지에 대한 계산 결과도 실험 결과와 비교하였다.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.39.1-39.1
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• 2010

본 연구에서는 정하중 및 충격하중 하에서 FRP(fiber reinforced polymer) sheet의 보강 성능을 평가하기 위해 섬유와 레진의 종류, sheet 종류, 보강 방법에 따른 휨 실험을 실시하였다. 이를 위해 GFRP와 CFRP, AFRP sheets로 보강된 $100{\times}100{\times}400mm$ 각주형 콘크리트 공시체의 하면 보강, 중앙 U형 스트립, 그라고 이 둘을 동시에 보강한 시험체를 제작하였고, 정하중 휨 실험과 낙하식 충격하중 실험을 실시하였다. 정하중 실험에서 중앙부 U형 스트립으로 보강한 시험체는 섬유의 방향과 균열의 진전 방향이 일치하여 보강효과가 거의 없었지만 CFRP와 AFRP로 하면 및 이중 보강한 시험체는 높은 휨성능을 보였다. 반면 충격하중 실험에서는 중앙부 U형 스트립 보강이 다소 성능을 향상 시켰고, 하면 및 이중 보강한 시험체는 큰 변형과 높은 에너지 소산 능력을 보였다.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.265-274
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• 2007

A study has been conducted to clarify NO emission behavior through preferential diffusion effects of $H_2$ and H in methane-hydrogen diffusion flames. A comparison is made by employing three species diffusion models. Special concerns are focused on what is the deterministic role of the preferential diffusion effects in flame structure and NO emission. The behavior of maximum flame temperatures with three species diffusion models is not explained by scalar dissipation rate but the nature of chemical kinetics. The preferential diffusion of H into reaction zone suppresses the populations of the chain carrier radicals and then flame temperature while that of $H_2$ produces the increase of flame temperature. These preferential diffusion effects of $H_2$ and H are also discussed about NO emissions through the three species diffusion models.

• Proceedings of the KAIS Fall Conference
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• 2008.05a
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• pp.139-141
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• 2008

최근 우리나라는 국토면적을 넓히기 위하여 많은 지역에 준설 및 매립 공사를 수행하고 있다. 준설 및 매립공사 시 주재료로 사용되는 해성점토는 매립 초기에 매우 연약한 지반을 형성하게 된다. 이에 빠른 구조물 시공을 위하여 대상지반의 압밀을 촉진시키는 다양한 공법이 활발히 연구되고 있다. 본 연구는 새로운 압밀촉진 공법개발을 위한 기초시험으로써 초음파 에너지를 연약지반 처리에 활용하고자 자체 고안된 초음파 발생장치를 적용하여 소규모 및 대형시험을 수행하였다. 시험에 사용된 연약 지반 점토시료는 시험조건의 일관성을 유지하기 위하여 자체개발한 원심력 시료 성형기를 사용하였다. 초음파 적용에 따른 압밀시험결과 매우 큰 압밀량의 증가를 확인할 수 있었으며 대형 시험의 경우에도 빠른 간극수압의 소산을 확인 할 수 있었다. 연구결과 초음파가 점토의 압밀시간을 단축시키는데 효과가 크다는 것을 볼 수 있었고, 차후 초음파를 통한 다양한 압밀촉진공법이 개발될 수 있다는 가능성을 확인 할 수 있었다.

• Journal of Korean Society of Steel Construction
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• v.21 no.4
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• pp.343-350
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• 2009

In the present study, a new seismic retrofitting method that employs both a stainless steel wire mesh and a permeable polymer concrete mortar was proposed for reinforced concrete bridge piers with nonseismic design details. For this purpose, a total of six nonseismically designed bridge piers were tested under lateral load reversals. The test results reveal that nonseismically designed piers with lap splices need to be retrofitted to resist earthquake induced forces. In addition, it was proven that the proposed retrofitting method can be useful in improving the strength, stiffness, and energy dissipation capacities of bridge piers designed nonseismically. It is thus expected that the proposed method may provide an improved ductility capacity without sudden softening of strength for bridge piers excursing inelastic displacement range.