• 한국농공학회지
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• 제27권2호
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• pp.47-56
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• 1985

Wasting fiberous residues from the cutting processes of steel materials at an iron-Works were mixed with concrete. The strength and toughness of steel fiber concrete with different steel contents were tested in a laboratory. The test results showed that the steel fiber residues can be used for the reinforcement of concrete. The potential applications of such product include floor constructions for facilities like dairy barns, grain storages, and machinery shops. The test results are as follows. 1. The compressive strengths of steel fiber concrete with one percent steel content by volume were 20 percent greater than that of plain concrete. The treatments also increased the concrete toughness by 96 percent. 2. When applied to tensile forces, the steel fiber concrete showed the increased strengths by 20 percent, and the toughness by 48 percent. 3. The steel content levels greater than or equal to 1.5 percent by volume resulted in the decreases of the compressive and tensile strengths of steel fiber concrete by 10 percent as compared to plain concrete. The concrete toughness increased with the steel contents. 4. The reinforcement effects of steel fiber depend on the quality of fiber material being used. Good steel fiber for concrete reinforcement appears to be uniform in shape and component, fine and long, and round-shaped.

• Steel and Composite Structures
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• 제32권1호
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• pp.59-66
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• 2019

Hollow steel-reinforced concrete-filled GFRP tubular member is a new kind of composite members. Firstly set the mold in the GFRP tube (non-bearing component), then set the longitudinal reinforcements with stirrups (steel reinforcement cage) between the GFRP tube and the mold, and filled the concrete between them. Through the axial compression test of the hollow steel-reinforced concrete-filled GFRP tubular member, the working mechanism and failure modes of composite members were obtained. Based on the experiment, when the load reached the ranges of $55-70%P_u$ ($P_u-ultimate$ load), white cracks appeared on the surface of the GFRP tubes of specimens. At that time, the confinement effects of the GFRP tubes on core concrete were obvious. Keep loading, the ranges of white cracks were expanding, and the confinement effects increased proportionally. In addition, the damages of specimens, which were accompanied with great noise, were marked by fiber breaking and resin cracking on the surface of GFRP tubes, also accompanied with concrete crushing. The bearing capacity of the axially compressed components increased with the increase of reinforcement ratio, and decreased with the increase of hollow ratio. When the reinforcement ratio was increased from 0 to 4.30%, the bearing capacity was increased by about 23%. When the diameter of hollow part was decreased from 55mm to 0, the bearing capacity was increased by about 32%.

• Geomechanics and Engineering
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• 제28권1호
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• pp.1-10
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• 2022

In Korea, accidents related to the collapse of deteriorated aging reservoirs occur every year. The grouting method is generally applied to reinforce an aging reservoir. However, when using this method, different reinforcing effects appear depending on the ground conditions. Thus, new construction methods and materials capable of providing consistent reinforcing effects are required. In this study, the direct shear test (DST), model test, and simulation analysis were performed to evaluate the impact of surface stabilizers, generally used to reinforce roads, rivers, and slopes of roads, applied using surface curtain walls on aging reservoirs. The DST results indicate that when the surface stabilizer was mixed with in-situ soil, the increase in cohesion was the highest at a mixing ratio of 9%. No changes in the friction angle were evident; therefore, 9% was determined to be the optimal mixing ratio. In addition, the model test and simulation analysis showed that when 9% of the surface stabilizer was mixed and applied to the aging reservoir, the seepage quantity of water and the saturated area were reduced by approximately 42% and 73%, respectively. Moreover, the comprehensive analysis of results showed that the grouting method could be completely replaced by surface stabilizers applied through surface curtain walls because the technique could secure stability by decreasing the seepage in the aging reservoir.

• Corrosion Science and Technology
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• 제4권4호
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• pp.130-135
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• 2005

In this study, accelerated corrosion tests were conducted on concrete specimens with and without accelerated carbonation beforehand for the purpose of elucidating the effects of carbonation, cover depth, and water-cement ratio (W/C) on the reinforcement corrosion. During testing, the corrosion current between the anode steel and cathode stainless steel was measured to continuously monitor the progress of corrosion throughout the test period, thereby investigating the mechanism of reinforcement corrosion and the relationship between corrosion and crack width, as well as other parameters.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.459-462
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• 1999

This paper presents a numerical study on the effect of live load pattern on RC flat plate under in-plane compression. Through the numerical study on various live load pattern, the load condition that governs the strength of the flat plate is determined. Effects of L.L/D.L. and arrangement of reinforcement on the behavior of the flat plate are also studied. And the efficient arrangement of reinforcement regarding to live load pattern is proposed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1041-1044
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• 2001

This study was performed to evaluate the effect of non-uniform corrosion distribution on the analysis of concrete cover failure. A series of experiments have been undertaken to measure the corrosion rate of reinforcement according to the concentration of chloride ion so as to suggest a relationship between the reinforcement corrosion rate and chloride ion density. The corrosion induced pressure depending on the density of chloride ion has been derived. And nonlinear analysis assuming nonlinear corrosion distribution for cover cracking was achieved and compared with other experimental results to verify the accuracy of the model. Analysis was also performed for various parameters to compare their effects.

• 한국터널지하공간학회 논문집
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• 제19권3호
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• pp.389-407
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• 2017

본 연구는 단독말뚝 또는 군말뚝 형태의 기초 하부를 터널이 근접통과할 경우 말뚝의 거동을 파악하기위해 3차원 유한요소해석을 수행하였다. 이때 터널과 말뚝기초 사이의 지반보강 조건별로 수치해석을 수행하여 결과를 분석하였다. 수치해석에서는 터널굴착으로 인해 유발된 말뚝침하, 축력, 전단응력 및 터널 주변지반의 전체변위를 고찰하였다. 단독말뚝의 두부침하는 지반보강의 범위가 가장 넓은 경우 지반보강을 고려하지 않은 말뚝에 비해 약 16% 감소하며, 말뚝의 최대 축력 또한 지반보강을 고려하지 않은 말뚝에 비해 약 30% 감소하는 것으로 분석되었다. 터널굴착에 따른 말뚝의 거동은 지반보강길이 (종방향 보강)보다는 보강각도(횡방향 보강)에 대해 더 크게 영향을 받는 것으로 분석되었다. 한편 오직 기초판 보강만을 실시한 군말뚝의 경우 선단부근 지반의 변위는 보강을 고려하지 않은 조건의 지반 변위와 비슷하게 나타났다. 이에 비해 말뚝두부에서는 기초판이 말뚝을 크게 구속하여 타 조건 말뚝의 경우에 비해 말뚝상부에서 축력이 약 2.5배 증가하는 것으로 분석되었다. 본 연구를 통해 보강조건에 따른 단독말뚝 및 군말뚝의 거동에 영향을 미치는 주요인자를 심도 있게 고찰하였다.

• 동의신경정신과학회지
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• 제21권2호
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• pp.87-101
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• 2010

Objectives : The aim of this experiment was to investigate the influences of Autonomic Nervous System and EEG by conducting Reinforcement-Reduction(補瀉) acupuncture stimulation to compare the changes in acupoints on the body before and after treatment of acupuncture at Xingjian(LR2) being referred as Fire-point(火穴) and Ququan(LR8) being referred as Water-point(水穴) of Yin Liver Meridian(足厥陰肝經). Methods : This study was carried out on 30 healthy female volunteers in their 20's. There were four tests conducted throughout and the period for each test was between 2 to 5days. HRV and EEG were measured for 5 minutes before acupuncture stimulation was conducted on LR2-Reinforcement, LR2-Reduction, LR8-Reinforcement and LR8-Reduction at random. During the 20 minutes of acupuncture treatment, same subjects were measured simultaneously to observe any significant changes in acupoints. Again, the same subjects were measured for 5 minutes after removing the acupuncture in order to perform a comparative analysis. Results : The measurement of HRV showed that LF, LFnorm and LF/HF ratio increased significantly(p<0.05) while HF, HF norm decreased significantly in case of LR2-Reinforcement & LR8-Reduction. Both LR2-Reduction and LR8-Reinforcement induced a significant increase in HFnorm. EEG measurement indicated low $\alpha$ wave decreased and high $\beta$ wave increased significantly at LR2-Reinforcement during post-acupuncture period compared with acupuncture stimulation period. Both LR2-Reduction and LR8-Reinforcement developed significantly low $\alpha$ wave and high $\alpha$ wave. High $\beta$ wave increased significantly at LR8-Reduction during the acupuncture stimulation in comparison with pre-acupuncture period. Conclusions : The manipulation of acupuncture stimulation at LR2-Reinforcement and LR8-Reduction enhanced the activity of sympathetic nerves and the state of arousal while that of para sympathetic nerves declined. On the other hand, LR2-Reduction and LR8-Reinforcement developed the levels of para sympathetic nerves and relaxation.

• 한국구조물진단유지관리공학회 논문집
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• 제22권5호
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• pp.82-90
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• 2018

원자력 발전소에는 No.36(D36)이상의 대구경 철근이 사용되는데 이러한 대구경 철근으로 갈고리 정착을 할 경우, 기준에서 요구하는 구부림 및 갈고리 길이로 인해 설계 및 배근에 있어 큰 어려움을 겪을 수 있다. 이러한 문제를 해결하기 위한 방안으로 확대머리 철근을 사용할 수 있다. 2008년 개정된 ACI 318에서는 확대머리철근의 정착길이식을 도입하였으며, 제정 배경 연구를 근거로 하여 횡보강근의 영향력을 무시하고 있다. 그러나 확대머리 철근이 겹침이음이나 컷오프 구간에서 사용될 경우, 인장재에 의해 피복 콘크리트를 밀어내는 힘이 발생하여 횡보강근에 작용하는 인장력이 크게 증가한다. 본 연구의 목적은 휨을 받는 부재 내에 정착된 확대머리 철근의 정착성능에 대한 횡보강근의 영향력을 평가하는 것으로, 이를 위해 횡보강근의 간격을 변수로 한 대구경 확대머리 철근의 정착실험을 수행하였다. 실험방법으로는 컷오프 구간을 모사한 실험을 수행하였으며, 확대머리 철근으로는 D43의 대구경 철근을 사용하였다. 실험 결과, 횡보강근이 없는 실험체의 경우 정착구간의 쪼갬파괴에 이어 단부의 하중이 확대머리 부근의 콘크리트에 직접적으로 작용하면서 상부 피복 콘크리트가 부재에서 탈락하는 취성적인 파괴형태가 나타났다. 또한 확대머리 철근의 발현강도가 항복강도의 절반밖에 못 미치는 매우 낮은 내력을 보였다. 이에 반해 횡보강근이 배근된 실험체의 경우 경우 횡보강근이 실험체 단부의 하중에 직접적으로 저항함에 따라 실험체 내력이 큰 폭으로 상승하였다.

• Geomechanics and Engineering
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• 제12권2호
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• pp.327-346
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• 2017

Laminated plates have many applications in different industrials. Buckling analysis of these structures with the nano-scale reinforcement has not investigated yet. However, buckling analysis of embedded laminated plates with nanocomposite layers is studied in this paper. Considering the single-walled carbon nanotubes (SWCNTs) as reinforcement of layers, SWCNTs agglomeration effects and nonlinear analysis using numerical method are the main contributions of this paper. Mori-Tanaka model is applied for obtaining the equivalent material properties of structure and considering agglomeration effects. The elastic medium is simulated by spring and shear constants. Based on first order shear deformation theory (FSDT), the governing equations are derived based on energy method and Hamilton's principle. Differential quadrature method (DQM) is used for calculating the buckling load of system. The effects of different parameters such as the volume percent of SWCNTs, SWCNTs agglomeration, number of layers, orientation angle of layers, elastic medium, boundary conditions and axial mode number of plate on the buckling of the structure are shown. Results indicate that increasing volume percent of SWCNTs increases the buckling load of the plate. Furthermore, considering agglomeration effects decreases the buckling load of system. In addition, it is found that the present results have good agreement with other works.