• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.57-65
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• 2022

This study investigated the electromechanical response of smart ultra-high performance fiber reinforced concretes (S-UHPFRCs) under flexural loading to evaluate the self-sensing capacity of S-UHPFRCs in both tension and compression region. The electrical resistivity of S-UHPFRCs under flexural continuously changed even after first cracking due to the deflection-hardening behavior of S-UHPFRCs with the appearance of multiple microcracks. As the equivalent bending stress increased, the electrical resistivity of S-UHPFRCs decreased from 976.57 to 514.05 kΩ(47.0%) as the equivalent bending stress increased in compression region, and that did from 979.61 to 682.28 kΩ(30.4%) in tension region. The stress sensitivity coefficient of S-UHPFRCs in compression and tension region was 1.709 and 1.098 %/MPa, respectively. And, the deflection sensitivity coefficient of S-UHPFRCs in compression region(30.06 %/mm) was higher than that in tension region(19.72 %/mm). The initial deflection sensing capacity of S-UHPFRCs was almost 50% of each deflection sensitivity coefficient, and it was confirmed that it has an excellent sensing capacity for the initial deflection. Although both stress- and deflection-sensing capacity of S-UHPFRCs under flexural were higher in compression region than in tension region, S-UHPFRCs are sufficient as a self-sensing material to be applied to the construction field.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.2
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• pp.149-156
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• 2023

Recently, concerns about natural disasters such as earthquakes, tsunamis and typhoons have increased. As the magnitude and frequency of earthquakes increase, research is needed to prevent structures from collapsing due to earthquake loads. Research is needed to increase the ductility of columns to prevent the collapse of structures. In this study, the ductility improvement of square columns achieved by applying spiral stirrups to square columns. Square columns reinforced with spiral stirrups are more resistant to repetitive loads such as seismic loads than columns reinforced with tie stirrups. Also, the spiral stirrups can apply better confinement to the concrete. In this study, an uniaxial compression test was conducted to evaluate the performance of columns reinforced with spiral stirrups. The results showed that the columns reinforced with spiral stirrups in both the circular and square columns showed higher compressive strength than the columns reinforced with the tie stirrups. In addition, the columns reinforced with spiral stirrups for both the square and circle columns, showed a tendency to endure the load even after the initial cracking and rebar yielding.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.391-398
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• 2010

The fire performance of RC slabs with half-depth precast panel after exposure to the ISO-834 fire standard without loading has been experimentally investigated. During heating, according to the ISO 834 fire curve, concrete spalling was observed for concrete without PP(polypropylene) fibers. No spalling occurred when heating concrete containing PP fibers. The maximum temperature of RC slabs with PP fibers with half-depth precast panel was lower than that of concrete without PP fibers. The ultimate load after cooling of the RC slabs that were not loaded during the furnace tests was evaluated by means of 3 points bending tests. The ultimate load of the RC slabs without PP fibers showed a considerable reduction (around 32.5%) of the ultimate load after cooling if compared with of RC slabs with PP fibers. The ultimate load of the RC slabs with half-depth precast panel with PP fibers is higher than that of a full-depth RC slabs with PP fibers. Also, the addition of PP fibers and the use of half-depth precast panel improve fire resistance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.11
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• pp.26-34
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• 2006

The thermo-mechanical analysis and test were performed for plate structure under mechanical and thermal loading conditions. Infrared heating system and hydraulic loading system were used to simulate mechanical and thermal environment for the plate structure which is similar to the fin of the airframe. Also, FEM analysis using plastic option was added to evaluate thermo-mechanical behavior. Thermo-mechanical tests were conducted at elevated temperature and rapid heating(10℃/sec) condition with external loading together. To investigate the effect of heating environment, the strength at room temperature was compared with that of elevated temperature and rapid heating condition. A methodology for test and analysis for supersonic vehicle subjected to aerodynamic loading and heating was generated through the study. These experimental and analysis results can be used for designing thermal resistance structures of the supersonic vehicle.

• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.189-199
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• 2011

Installation of a proper root barrier in a green roof system is very important in order to protect the concrete slab of roof and the root penetration in the waterproofing layer. To select the proper root barrier materials and methods, it is necessary to understand the environmental conditions affecting the waterproofing-root barrier system in green roof construction site. Therefore, we suggested as the environmental performance indexes four kinds of performance requirements; root penetration, chemical attack by chemical agent or fertilizer, load impact by soil depth and size of plant, and water pressure. The related four test methods were suggested for the inspection of these performance indexes. In this research, we could suggest for kinds of test methods as standard test methods to evaluate the environmental performance of waterproofing-root barrier for greening roof system.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2005.05a
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• pp.214-217
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• 2005

• Tribology and Lubricants
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• v.12 no.4
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• pp.1-6
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• 1996

냉간압연유는 종래보다 극심한 압연하중 및 압연속도 조건하에서도 Roll과 압연강판간의 균일한 윤활피막을 형성시켜 Heat Scratch를 방지시키고, 여러가지 종류의 압연기 특성과 압연조건에 맞는 윤활 및 마찰상태를 부여시켜 안정된 조업을 유지시켜야 한다. 또한 최근 우리나라뿐만 아니라 국제적인 환경 추세에 부응하여 기본적인 압연윤활성 및 마찰특성이외에 작업환경 개선(Mill Clean화, 폐수처리용이성, 생분해성), 보다 우수한 강판표면 품질(Oil Stain, 이물 Mark, 광택성 등)을 생산할 수 있는 특성을 나타내어야 한다. 본 보에서는 이와같은 철강용 냉간압연유의 전반적인 동향에 대해 기술코져 한다.

• Proceedings of the KGS Conference
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• 2003.11a
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• pp.8-12
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• 2003

범람원은 홍수시 하천의 유량이 급격하게 증가해서 하천의 운반물질인 부유 하중이 하도를 넘어 하천 양안에 범람하여 퇴적되면서 형성된 지형으로, 유량이 많고 하곡이 넓은 지역에서 잘 발달한다. 범람원 중 자연제방은 지면이 높아 홍수의 피해가 적고, 배수가 잘 되기 때문에 취락의 입지나 농경에 유리하고, 배후습지는 지하수위가 높아 배수가 불량한 지형으로 오늘날에는 농경지로 개간하여 활용하고 있다. (중략)

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.453-460
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• 2016

Offshore wind turbines are divided into an upper wind turbine and a lower support structure. Offshore wind turbine system is required to secure high reliability for a variety of external environmental conditions compared to ground wind turbines because of additional periodic loads due to ocean wave and current effects. In this study, extreme load analyses have been conducted for the designed offshore wind turbine foundation with weight control functionality using computational fluid dynamics (CFD) then structural analyses have been also conducted to investigate the structural design requirement.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.452-453
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• 2008

본 논문에서는 송전철탑에 작용하는 설계하중으로서 [송전철탑 설계풍속에 관한 연구]에 근거하여 1987년 6월 제정된 지역별설계 풍하중기준의 개정을 위한 연구결과를 수록하였다. 당시 제정된 송전설계기준은 이전에 전국적으로 통일시켜 적용되던 풍속압($76kg/m^2$)을 지역별 풍속을 구분하여 그 차이에 따라 I, II, III, 지역 및 울릉도로 구분하여 차등 적용하였으며, 본 연구에서는 국내 기상청이 생긴 이래 2005년까지 누적된 기상 DB의 분석을 통하여 최근의 기상 현상을 반영한 보다 현실적인 설계기준 개정과정을 수록하였다. 본 논문에서는 1980년대 후반부터 약 20년간의 기상청의 풍향, 풍속자료를 추가로 확보하여 이를 분석하고 재현기간을 반영한 지역별 설계하중을 재산정하여 최근의 기상자료를 포함하여 보다 정확한 분석을 도모하고, 사회 환경의 급변함에 따라 우려되는 기상이변 등을 고려한 안전성과 경제성이 향상된 설계기준의 산정과정을 고찰하고자 한다.