• 콘크리트학회논문집
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• 제11권6호
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• pp.89-100
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• 1999

Service life of concrete structures that are exposed to the environmental attack is largely influenced by the corrosion of reinforcing bare due to the chloride contamination. Chloride ions penetrate continuously into concrete from the environment, and chloride diffusion velocity is governed by a mechanical steady stage. In this study, a method is developed to predict corrosion initiation of reinforcing bars in the sea-shore structures, based on governing equations that take into account the diffusing of chloride ions and a mechanical steady state. As a result of this study, Corrosion Prediction System (CPS) is developed, and it can be used to determine an optimal time for repair and rehabilitation actions need to be taken. Futhermore, CPS assists the concrete mixing structures by predicting of chloride concentrations in concrete mixture, exposed to salt concentrations and service environment.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.43-48
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• 2001

To overcome the disadvantages of conventional excavation technology, various trenchless (or excavation free, or no-dig) repair-reinforcement technologies have been developed and tried. But trenchless technologies so fat developed have some brawbacks such as high cost and inconvenience of operation. In this study, a repairing-reinforcing process for underground pipes with glass fiber fabric polymer composites using VARTM(Vacuum Assisted Resin Transfer Molding) has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than those of the conventional trenchless technologies. For the reliable operation of the developed method, a simple method to apply pressure and vacuum to the reinforcement was devised and flexible mold technology was tried. Also, resin filling and cure status during RTM process were monitored with a commercial dielectrometry cure monitoring system, LACOMCURE. From the investigation, it has been found that the developed repairing-reinforcing technology with appropriate process variables and on-line cure monitoring has many advantages over conventional methods.

• 산업기술연구
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• 제33권A호
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• pp.73-80
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• 2013

This paper is results of numerical analysis on the behavior of colluvium slope with combinations of soil nails and earth anchors during excavation. In order to maintain the stability of the colluvium cut, being composed of gravel and boulder and thus local in stability being expected during slope cut, temporary reinforcing method of soil nailing with shotcrete might be used. Subsequent method of cast-in-place facing with earth anchors can be used to maintain cut slope stable permanently. For the cut slope where these methods had been applied, the numerical techniques were applied to their behaviors and investigate the stability of the slope. Limit equilibrium methods were used to confirm to maintain the slope stability during and after excavation and application of those reinforcing methods. Another numerical technique of FEM was also used to find the stress and strain as well as deformation distribution in reinforcing materials and slope ground during excavation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.143-144
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• 2016

The core drilling method is considered to be the most effective and common method of assessing the compressive strength of concrete in existing reinforced concrete buildings for structural repair and retrofit. In general, core specimens within reinforcing bars are not permitted in the regulations with regard to assessing concrete strength even if the core specimens can contain the bars in some cases. The purpose of this study is to investigate the effects of the reinforcement arrangement on the concrete compressive strength as a basic research to propose the quantitative criteria of strength for core specimens containing reinforcements. To complete the basic research, cylinder specimens inserted in a variety of reinforcement arrangements were prepared and tested.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.801-804
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• 2004

It should be noted that the critical chloride threshold level is not considered to be a unique value for all conditions. This value is dependent on concrete mixture proportions, cement type and constituents, presence of admixtures, environmental factors, steel reinforcement surface conditions, and other factors. In this study, the accelerated corrosion test for reinforcing steel was conducted by electrochemical and sea water-circulated method, respectively and during the test, corrosion monitoring by half cell potential method was carried out to estimate the critical chloride threshold value when corrosion for reinforcing steel in concrete was perceived. For this purpose, lollypop and beam test specimens were made for $31.4\%,\;41.5\%\;and\;49.7\%$ of w/c. respectively and then the accelerated corrosion test for reinforcing steel was executed. It was observed from the test that the time to initiation of corrosion was found to be different with water-cement ratio and the critical chloride threshold value was found to range from 0.91 to $1.27kg/m^3$.

• Journal of Acupuncture Research
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• 제17권1호
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• pp.43-54
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• 2000

Previously two papers dealing with YoungSu(against the meridian course and following the course of the meridian) Acupuncture were published by our group. Here we are reporting the further analysis of YoungSu and WonBang(by twisting and rotating the needle) acupuncture methods. It is very important to understand objectively the Qi variation induced by the reinforcing-reducing manipulation method in the acupuncture therapy. We decided the medical treatment by utilizing the PyongChi Method (a kind of method to figure out the way of treatment by observing the unbalanced state of five phases). The Qi variation in the meridian treated by YoungSu and WonBang, the recovery of five phases deviation were measured by choosing single acupoint instead of complex acupoints. By using Youngsu and WonBang, we increased or decreased the Qi of the phase which caused the unbalanced state. We observed whether the Qi of the treated meridian can be increased and if the state of unbalance can be recovered. To achieve the effect of reinforcing-reducing, we needed a correct choice of treating method and a selection of a proper meridian in advance. This study was carried out by adding another way of acupuncture from the previous paper. We discovered that the effects of reinforcing-reducing by each manipulation method could be superposed each other when two counteracting Youngsu and WonBang methods were treated at the left and the right side of human body which was correspondent with our previous paper. We found that the Qi variation of the treated meridian, which was induced by Youngsu and WonBang, was linearly proportional to the reduction of five phase deviations. The slope of Qi variation was almost similar (y = -0.413x - 0.138) as that of previous paper (y = -0.266x - 0.038, Y = -0.446x - 0.079). It is assumed that the addition of other basic methods on the top of reinforcing-reducing manipulation method would magnify the effect of acupuncture.

• 한국안전학회지
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• 제25권6호
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• pp.128-136
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• 2010

In according with concrete structural design standard, it is common designing flexure reinforcement concrete to induce tension failure. So reinforcing ratio is limited to inducing tension failure. And maximum reinforcing ratio is regulated to protecting concrete compression strength caused by over reinforced building. Minimum reinforcing ratio is also limited in designing standard to protecting brittle failure as extremely using less reinforcing bar. But in minimum reinforcing ratio it is extremely conservative or it is sometimes impossible to induce stable tension-failure because they are depending on yield failure and experienced method and concrete designing standard strength. Therefore the purpose of the present paper is to evaluate the flexural behavior of minimum steel ratio of reinforced concrete of beams and to propose the guide-line of equation of minimum steel ratio by performing static flexural test of 16 beams according to size effect, number of steel, yielding stress of steel, and concrete compressive strength which are presumed effective variables. From experimental results, the equation of minimum steel ratio was newly proposed considered size effect.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.883-887
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• 2009

In this study, a new soil retaining system was proposed by soil cement mixing method. The new soil retaining system is based on deep cement mixing method by large diameter reinforcing blocks (piles). Large diameter reinforcing blocks (usually $\varnothing$300-500 mm) have the advantage to make reinforcements over a relatively short depth and thus reduce the amount of reinforcement necessary. A field case has been reviewed for actual application of the soil retaining system at a downtown site. Research was conducted to evaluate the behavior of the installed soil retaining wall, with reinforcing blocks (400 mm in diameter and 4 m in length) placed into a 10 m excavation wall at a $20^{\circ}$ angle. As a result, the potential for applying this method to the downtown excavation site was confirmed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.245-248
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• 2005

It should be noted that the critical chloride threshold level is not considered to be a unique value for all conditions. This value is dependent on concrete mixture proportions, cement type and constituents, presence of admixtures, environmental factors, steel reinforcement surface. conditions, and other factors. In this study, the accelerated corrosion test for reinforcing steel was conducted by electrochemical and cyclic wet and dry seawater method, respectively and during the test, corrosion monitoring by half cell potential method was carried out to estimate the chloride corrosion threshold value when corrosion for reinforcing steel in concrete was perceived. For this purpose, lollypop and right hexahedron test specimens were made for 31.4$\%$, 41.5$\%$ and 49.7$\%$ of w/c, respectively and then the accelerated corrosion test for reinforcing steel was executed. It was observed from the test that the time to initiation of corrosion was found to be different with water-cement ratio and accelerated corrosion test method, respectively and the chloride corrosion threshold value was found to range from 0.91 to 1.43 kg/$m^{3}$.

• 한국안전학회지
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• 제23권5호
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• pp.125-130
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• 2008

PSC보의 보강 시에 안전도분석을 위한 신뢰성해석과 생애주기비용을 최소화하기 위만 최적설계를 실시하였다. 신뢰성해석은 현재 공용중인 표준단면을 변형시키면서 실시하며 자연적 불확실성과 인위적 불확실성을 고려하였다. 자연적(내재적) 불확실성을 고려하여 최소생애주기비용을 구한 후에, 인위적 불확실성을 최대 90%의 분산까지 고려하여 재해석을 실시하였다. 보강방법에 대한 신뢰성해석과 최소생애주기비용해석은 보강방법을 결정하는데 매우 합리적인 기준을 제시하였다.