• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.794-801
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• 2003

As it is important to measure the degree of the deterioration and predict service life caused by chloride in concrete structure the methods of measuring chloride in the concrete is raised important problems. This study is to set a new standard for using of the colorimetric method through grasping the character of the colorimetric distinction method, and measuring the chloride content at the place discolored. Also, to predict chloride content around embeded bar and time reaching limit chloride concentration through measuring the chloride content of concrete surface by colorimetric distinction method and this study presents the new concept of concrete degradation and diagnosis of the durability by salt damage. According the results, it is possible to use colorimetric distinction method as simplified measurement to measure the fixed quantity of the chloride concentration. What is more, it would make calculation of concrete surface chloride had a wide fluctuation at the general environment extended. Also, it would be make estimating durability of reinforced concrete structures applied to the basic data.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.231-242
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• 2016

Earthquake resistance of RC column-steel beam (RCS) joints with simplified details were studied. Simplified details are necessary for large columns to improve the productivity and constructability. To strengthen the beam-column joint, the effects of transverse beams, studs, and U-cross ties were used. Four 2/3 scale interior RCS connections were tested under cyclic lateral loading. The specimens generally exhibited good deformation capacity exceeding 4.0% story drift ratio after yielding of both beam and beam-column joint. Ultimately, the specimens failed by shear mechanism of the joint panel. The test strengths were compared with the predictions of existing design methods.

• Journal of Korean Society of Steel Construction
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• v.29 no.5
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• pp.353-359
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• 2017

The purpose of this study is to evaluate the strength and behavior of the composite member in case of concrete filled steel tube embedded in concrete for application concrete filled steel tube to steel rib support in tunnel. A total of six beam specimens were prepared for steel tube in-filled with plain concrete and aerated concrete, and static bending tests were performed. As a result, the member of concrete steel tube embedded with plain concrete showed higher strength than those with aerated concrete. However, it was found that the flexural strength of member with reinforcing bar around the steel tube is more influenced by the amount of the reinforcing bar than the type of the filled concrete.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.170-175
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• 2011

최근 고강도 콘크리트의 내화성능이 사회적 이슈로 부각되고 국토해양부에서 고강도 콘크리트의 내화성능 관리기준(안)이 고시되면서 국내에서도 고강도 콘크리트의 내화성능을 향상시키기 위한 연구가 활발히 진행되고 있다. 본 연구에서는 유기질 섬유인 폴리프로필렌섬유(PP섬유)와 강섬유를 하이브리드한 Fiber Cocktail를 혼입한 고강도 내화콘크리트 개발을 위한 연구를 수행하였다. PP섬유는 $160^{\circ}C$의 온도에서 용융되어 콘크리트 내부에 미세한 통로를 형성하여 고강도 콘크리트 부재 내의 수증기압 및 공극압을 효과적으로 배출하여 고강도 콘크리트의 폭렬발생을 억제시키는 데 효과적이며, 강섬유는 PP섬유가 용융된 후의 고강도 콘크리트 부재의 균열 발생을 억제하며 외부로부터 침투하는 열기를 차단할 수 있다. 100MPa 고강도 콘크리트의 내화실험을 실시하여 최적단면 조건을 도출하기 위해 철근온도를 분석한 결과, 단면이 커질수록 철근온도는 점차 낮아지는 경향이 나타났으며 $600{\times}600mm$, $800{\times}800mm$ 단면에서 내화성능을 확보할 수 있는 것으로 나타났으며, 이중 경제성을 고려할 경우 $600{\times}600mm$ 단면이 최적단면으로 도출되었다. 또한 도출된 $600{\times}600mm$ 단면에 대해서 철근의 온도를 분석한 결과 PP섬유 $1.5kg/m^3$와 강섬유 $40kg/m^3$를 배합한 Fiber Cocktail이 최적배합비로 나타났다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.1-9
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• 2015

This study is on the shear strength of the internal joints of RCS composite structure consisting of reinforced concrete column and steel beam. As a newly structure system, the composite system has been developed to fully utilize the advantages of reinforced concrete column and steel beam, which also include economic and practical joint detail. Nevertheless stress transfer mechanism and structural behavior of the joints had not been still clearly revealed and shown much difference from the proposed equation. In this study, by observing the crossing of reinforced concrete column through steel beam to the RCS structure beam type, thirty seven shear failure specimens were selected and applied to the 5 major equations which is used to calculate the shear strength of RCS joint. Through the regression analysis, modified equation which is more reliable and approximate results for shear strength of RCS joints was proposed.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.185-193
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• 2012

In this study, an estimation equation was proposed to predict the shear strength of RC interior beam-column connections. The proposed equation considered the effect of both truss and arch mechanisms, while the existing equations in the ACI and AIJ design codes consider only arch mechanism. In addition, the proposed equation estimates the shear strength of RC joints by considering the contribution of the vertical and horizontal steel bars on the effective compressive strength of concrete. The shear strength of RC joints calculated by the proposed equation was compared with the test results of 54 RC joints, which failed in shear before plastic hinges developed at the end of the adjacent beams. The comparison study showed that the proposed equation estimated the strength of the 54 specimens with a mean value of 1.14 and the coefficient of variation of 20%. The proposed equation provides improved prediction compared to those obtained from the equations in the ACI and AIJ design codes.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.153-156
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• 2008

The objective of the present study is to evaluate the flexural behavior of reinforced concrete columns externally strengthened with wire rope and T-shape steel plate units. Three strengened columns and a control unstrengthened column were tested under cyclic lateral load simultaneously subjected to a constant axial load. All columns had same section size, and the arrangement of longitudinal reinforcement and internal hoop. The spacing of wire rope range from 40 ${\sim}$ 80mm, which corresponds from 1.0 ${\sim}$ 0.5, respectively, times the minium amount of hoop specified in seismic design of ACI 318-05. Test results showed that the proposed unbonded-type strengthening procedure is very effective for improving the flexural ductility of reinforced concrete columns.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.161-164
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• 2008

In recent years, carbon fiber-reinforced polymer (CFRP) has been widely used for repairing and/or strengthening structural elements in concrete. Not enough test data, however, are available to predict the long-term performance of the repaired and improved structures exposed to weathering. The objective of this research is to study the effect of freeze-thaw cycling on the behavior of reinforced concrete (RC) beams strengthened in shear with carbon fiber sheet. Six small-scale RC beams (100mm${\times]$100mm${\times]$400mm) were strengthened with CFRP in shear, subjected to up to 400 cycles freeze-thawing from -17${\sim}4^{\circ}C$, and tested to failure in four-point bending. Test result, there was no significant damage to carbon fiber sheet strengthened concrete beams had been suffered 30 cycles of freeze-thawing, and more over 60 cycles of freezing-thawing brought about a reduction in resistance of only 25% of the initial level.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.41-44
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• 2008

Fiber Reinforced Polymers (FRPs) have recently been highly used for repairing and strengthening civil structures due to their superior material properties. By using FRPs, external bond method is the most used method in the construction industry. Although many researches on reinforced concrete externally strengthened with FRPs have been conducted, time-dependant behaviors of the beams have not been investigated yet. This paper documents a series of beam experiments that were carried out to evaluate time-dependant behavior. Three RC beams were built and the parameters considered in this experiment were types of FRPs. Through these experiments, it was proved that the beam strengthened with CFRP was more effective than that with GFRP in terms of time-dependant behavior.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.110-119
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• 2012

Fiber reinforced polymer (FRP) reinforcing rebar with non-corrosive property is suggested as an alternative replacement to steel reinforcing rebar due to its enhanced durability and non-corrosive characteristics. Currently, a limited number of glass fiber reinforced polymer rebar (GFRP) are sold commercially due to their high cost, relatively low performances, and brittle failure characteristics. Therefore, the performance enhancements and cost reduction of GFRP rebar are needed to increase its applications in construction fields. The intent of this study is to develop high performance GFRP rebar by improving its tensile and shear properties. Also, in order to reduce manufacturing costs, factors such as material composition and manufacturing process were evaluated to improve manufacturing efficiency. Finally a GFRP rebar with enhanced material properties and less expensive than the GFRP rebar currently sold in the market was manufactured and evaluated for its application possibility in construction fields.