• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.252-253
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• 2019

Corrosion of rebars in reinforced concrete structures is a major factor that shortens the life of the structure. As corrosion progresses, the adhesion between the concrete tissues and the rebar decreases and the cracks in the concrete due to the expansion of the oxide intensify. Although it is necessary to measure corrosion behavior of rebars inside the concrete to measure degradation of structures due to rebar corrosion, no studies have been conducted to measure corrosion of rebars in In-situ state. In this study, corrosion of rebars in reinforced concrete specimens was attempted to be quantified using micro-computer tomography. Since corrosion of concrete takes several months per 10mm of cover, accelerated corrosion techniques were applied. Accelerated corrosion on the specimen was conducted by applying a 10 V magnetic field to the buried rebar and external electrodes with the specimen submerged in a 10% calcium chloride solution. The experiment found that within two weeks, more than 40% of rebar reduction occurred, and the cracks in the radial cracks occurred through the concrete structure, leading to the transfer of the oxide produced through the cracks to the surface of the specimen.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.575-578
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• 1999

The main objective of this study was to examine structural behavior of reinforced concrete column and steel beam joint. composite specimens about 3/4 of the actual beam column connection assembly were tested by applying cyclic load through actuators. Test variables include face bearing plate(FBP), extended face bearing plate(E-FBP), VIR, U-bar and sub beam. There is not much differenced between specimens with sub beam and without sub beam. Test results also show that the joint strength of test specimen is close to the predicted strength by ASCE guideline.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
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• pp.59-64
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• 1994

Following the previous research(7), a total of forty six specimens were tested to scrutinize the dowel action of reinforcing bars. Concrete cover, width of specimen and reinforcing bar size were taken as main test variables for constant compressive strength of concrete, based on the observation of the test results, the characteristic effects of the test variables on the dowel strength have been analyzed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 봄 학술발표회 논문집
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• pp.122-127
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• 1990

The transfer of forces across the interface by bond between concrete and steel is of fundamental importance to many aspects of reinforced concrete behavior. Bond stress - slip relationships were studied using a symmetrical tension test specimen. This type of test is intented to simulate conditions in the tension zone of a concrete beam between primary cracks and below the neutral axis. These relationships between local bond stress and local slip are quite different at different locations along the bar. The present study allows more accurate analysis of reinforced concrete structures by employing more realistic bond stress-slip relations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.973-978
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• 2002

This study was performed to verify the effect of various testing conditions affecting measured compressive strength of concrete core and to compute the correction coefficients for it. Conditions of specimens affecting test results include size(diameter), height-diameter ratio, humidity of specimen, amount and arrangement of bar, core direction from structure and method of end preparation. In testing core strength of concrete, special cares should be taken on various testing conditions whose effects have been latent in conventional concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.215-218
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• 2003

To analyze a bond stress-slip behavior between a reinforcing bar and concrete under repeated loading, pull-out fatigue test was performed. Major variables were repeated stress levels and cycle numbers. Test specimen was taken repeated constant amplitude loading before it was fractured by pull-out test. Increments of bond strength and slip according to repeated stress level and cycle numbers were analyzed. On the basis of test results, Local bond stress-slip relationship under repeated loading were formulated

• Corrosion Science and Technology
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• 제13권1호
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• pp.20-27
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• 2014

The structures of reinforced concrete has been extensively increased with rapid development of industrial society. Futhermore, these reinforced concretes are easy to expose to severe corrosive environments such as sea water, contaminated water, acid rain and seashore etc.. Thus, corrosion problem of inner steel bar embedded in concrete is very important in terms of safety and economical point of view. In this study, multiple mortar test specimen(W/C:0.4) with six types having different cover thickness each other was prepared and was immerged in seawater solution for five years to evaluate the effect of cover thickness and immersion years to corrosion property of embedded steel bar. And the polarization characteristics of these embedded steel bars was investigated using electrochemical methods such as measuring corrosion potential, cathodic polarization curve, and cyclic voltammogram. At the beginning of immersion, the corrosion potentials exhibited increasingly nobler values with increasing cover thickness. However, after immersed for 5 years, the thicker cover of thickness, the corrosion potentials shifted in the negative direction, and the relationship between corrosion potential and cover thickness was not in good agreement with each other. Therefore, it is considered that the thinner cover of thickness, corrosive products deposited on the surface of the embedded steel bar plays the role as a resistance polarization which is resulted in decreasing the corrosion rate as well as shifting the corrosion potential in the positive direction. As a result, it seemed that the evaluation which corrosion possibility of the reinforced steel would be estimated by only measuring the corrosion potential may not be a completely desirable method. Therefore, it is suggested that we should take into account various parameters, including cover thickness, passed aged years as well as corrosion potential for more accurate assessment of corrosion possibility of reinforced steel which is exposed to partially or fully in marine environment for long years.

• 해양환경안전학회지
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• 제28권6호
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• pp.1078-1085
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• 2022

선박에 부착된 수중생물은 선체에서 성장하면서 선박의 저항을 크게 증가시킬 뿐만 아니라 부착생물이 배와 함께 이동하면서 지역의 해양 생태계 교란을 야기시키기도 한다. 이에 따라 국제해사기구에서는 선체부착생물의 이동을 막기 위해 선체부착생물 제거 및 청소성능 평가 논의를 시작해 오고 있다. 본 연구에서는 소형선박에 사용되는 FRP(Fiber Reinforced Plastic), HDPE((High Density Polyethylene), CFRP(Carbon Fiber Reinforced Plastic) 재료의 시편을 격포항(전락북도)에 약 80일간 양생시킨 후 물 제트 노즐을 이용하여 부착생물 제거실험을 수행하였다. 그 결과 김과 같은 해조류는 노즐과 시편과의 거리가 1.8cm, 100bar 일 때 제거되었지만, 따개비의 경우 200 bar 이상은 되어야 청소가 되는 것을 확인하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제10권5호
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• pp.106-114
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• 2006

본 연구는 개발된 저수축 고성능 콘크리트를 대상으로 모의부재 시험체에 있어서 콘크리트의 기초적 물성과 수축특성에 대하여 검토한 것이다. 실험연구 결과, 콘크리트의 배합특성으로 제안 배합은 목표 슬럼프플로우 및 목표 공기량을 만족하기 위해 SP제량 증가, AE제량 감소의 배합보정이 필요하였다. 응결시간은 제안 배합이 8시간 정도 빠르게 나타났으며, 굳은 콘크리트의 압축강도는 60MPa 이상의 고강도로 나타냈다. 수축특성으로 제안 배합 자기수축의 경우 플레인 배합 자기수축에 비해 50% 정도 저감되었고, 제안 배합의 중심부 건조수축은 수분발산이 없는 것에 기인하여 자기수축과 유사한 경향이었으나, 표면부는 크게 수축하였다. 단, 철근배근 시험체인 경우는 철근구속에 의해 내부 및 표면의 수축량이 작게 나타났다.

• 대한기계학회논문집A
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• 제37권7호
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• pp.891-897
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• 2013

본 논문에서는, 고 변형률 속도에서의 알루미늄 합금의 압축 변형거동을 홉킨슨 압력봉 시험, SHPB 방법을 통해 연구하였다. 이와 함께 음향방출기법이 사용되었고, 웨이브 가이드선을 통해 시편에 연결된 AE 센서를 이용하여 충격 변형시 검출되는 AE 신호를 실시간으로 검출하였다. 검출된 AE 신호를 통해 진폭, 에너지 및 최대 주파수 특성을 분석하였다. 또한 손상 기구에 따른 음향방출신호의 특성을 분석하기 위하여 시험 수행 후 충돌 시험편 표면과 측면을 관찰하였다. 변형률이 높아질수록 AE 진폭과 AE 누적에너지는 증가하였고, AE 최대 주파수는 감소하였다. 각 신호의 특성은 재료의 손상 기구와 밀접한 관련이 있는 것으로 확인되었다.