• Magazine of the Korea Concrete Institute
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• v.6 no.2
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• pp.169-179
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• 1994

Recently the construction of residential buildings faces many difficulties due to the shortage of building materials and works. Simplifying the stage of processing and assembling reinforcing rods and increasing the efficiency of them in reinforced concrete construction can be used to settle the difficulties. In the respect, structural wire-fabric and loop wire-fabric is utilized. The purpose of this study, on condition of being $210kg/cm^2$ concrete strength, is to analyze the structural and flexural properties of one-way concrete slabs by testing with different reinforcing type, tensile steel ratio based with minimum steel ratio, boundary condition and splice length which affect the maximum width of crack and ductility factor. From the test results, the ductility factor is approved that the slabs using deformed bar were much better than that using wire-fabric, and 30D of splice length was appropriate in the slabs as splice length. In the control of the maximum crack width the slabs using wire-fabric and loop wire-fabric were much better than that using deformed bar.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.95-106
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• 1992

This paper presents a comparative evaluation of five different types of steel fibers used as reinforcing material in concrete beams. Two types of plain and RC beams were prepared to compare the relative flexural behavior. The fibers used were dog bone (paddled), both ends hooked. コ-type straight. crimped and wavy type with aspect ratio of 43 to 75. Fiber volume fraction of 1 to 2% were used while shear span to depth ratio (aid) and steel ratio p were fixed. Fiber reinforcement effect index Ef and effective toughness index Te were adopted to evaluate fiber reinforcing effects. The effect of fiber reinforcement on flexural strength is higher in plain beams than in RC beams. Hooked and dog bone type fibers were found to be more effective than the other type ones in enhancing the flexural strength and post-peak energy absorption capacity of concrete beams.

• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.213-220
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• 2005

Carbon fiber reinforced polymer (CFRP) sheets are becoming increasingly popular for strengthening deteriorated concrete bridges due to their excellent strength and stiffness-to-weight ratio, corrosion resistance, and convenience of construction work. The purpose of this study is to compare the performance of CFRP-strengthened reinforced concrete (RC) beams and to develop a new design formula. Simple beams with 3 m span length were tested to investigate the effect of reinforcing steel ratio and CFRP-reinforcing ratio on the flexural behavior of strengthened RC beams. The test results were analyzed with the special emphasis on the failure mode, the maximum load, and the strain distribution in the section. It is shown that the strain of the strengthened beams is not linearly distributed in the section. A new design formula based on the non-linear distribution of the strain has been derived and showed that it has a good agreement with the various domestic and foreign test results.

• Magazine of the Korea Concrete Institute
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• v.10 no.2
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• pp.119-126
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• 1998

본 연구는 철근비와 보강판비를 조정한 보강철근비를 변수로 탄소섬유쉬트 접착된 철근콘크리트 보에 대하여 그 변형특성과 강도특성 및 파괴모드를 실험적으로 고찰한 것이다. 철근비와 보강판비가 증가할수록 최대내력은 증가하는 경향을 보이지만 탄소섬유쉬트의 겹수가 증가할수록 철근비 증가의 경우와는 달리 에너지흡수능력이 저하된다. 철근비와 보강판비에 따른 파괴모드를 구분하고 시험결과와 비교, 고찰하였던 바 파괴모드와 연성의 측면에서 보강철근비 е의 한계값을 0.87 max으로 제안하였다．탄소섬유쉬트와 철근콘크리트 보의 합성작용이 철근항복이후까지 유지되어 비선형적인 거동을 보임으로써 구조적거동이 양호하게 나타나는 것으로 입증되었다.

• Steel and Composite Structures
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• v.17 no.4
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• pp.517-533
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• 2014

Experimental results of 39 specimens including concrete columns, RC columns, hollow steel tube columns, concrete filled steel tubular (CFT) columns, and reinforced concrete filled steel tubular (RCFT) columns are presented. Based on the experimental results, the load-carrying capacity, confined effect, ductility, and failure mode of test columns are investigated. The effects of the main factors such as width-thickness ratio (the ratio of external diameter and wall thickness for steel tubes), concrete strength, steel tube with or without rib, and arrangement of reinforcing bars on the mechanical characteristics of columns are discussed as well. The differences between CFT and RCFT are compared. As a result, it is thought that strength, rigidity and ductility of RCFT are improved; especially strength and ductility are improved after the peak of load-displacement curve.

• Journal of the Korea Concrete Institute
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• v.12 no.1
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• pp.33-44
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• 2000

Since the mechanism of chloride diffusion and its ratio in concrete depend on structural conditions and concrete as a micro-structure, if these are analyzed quantitatively, the long-term ageing of structures can be predicted. Although, a quantitative analysis of concrete micro-structure, in which the results are affected by various parameters, is very difficult, this can be done indirectly by the durability test of concrete. In this study, the compressive strength, void ratio and air permeability of concrete. In this study, the compressive strength, void ratio and air permeability of concrete are chosen as the parameters in concrete durability test, and these effects on test results are analysed according to changes of mixing properties. The relationships between parameters and chloride diffusion velocity is used for prediction models of chloride diffusion. The developed prediction models for the chloride diffusion according to mixing and physical properties, can be used to estimate the service life and corrosion initiation of reinforcing bars in marine structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.637-640
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• 2006

Corrosion from various causes of reinforcing steel in concrete structures not only shortened the life of structures but also it is necessary a great repair cost to return and protect to the health condition. Using Nitrite inhibitors is a typical protection method. But there is no materials for the study about corrosion protection using nitrite. Therefore it is important to evaluate the additional rate and influence on congealment using the nitrite inhibitors in cement paste which is originally the basic material and crucial factors consisting concrete. The purpose of this study is finding influence of the type of nitrite inhibitors and mixing ratio on congealment of cement paste, and finding best corrosion inhibitors and ratio in cement paste.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.86-89
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• 2003

It is recognized that reinforcement corrosion is the main distress behind the present concern regarding concrete durability. In this study, to confirm corrosion of reinforced concrete affected by thickness of cover, kinds of surface coating, measured electric potential, ratio of corrosion area, weight reduction, corrosion velocity of steel bar under environment of complex deterioration. The results showed that an increase in age also increases corrosion of steel bar. Ratio of corrosion area is largely related to ratio of weight reduction. as well, corrosion of steel bar by thickness of cover is superior to l0mm thick than 20mm thick. It showed that an increase in thickness of cover prevent steel bar from deteriorating. The results of this study showed that corrosion velocity was affected by thickness of cover, kinds of surface coating. data on the development of corrosion velocity made with none, organic B, organic A, inorganic B, and inorganic A is shown.

• International Journal of Concrete Structures and Materials
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• v.2 no.2
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• pp.115-122
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• 2008

Ductility is important in the design of reinforced concrete structures. In seismic design of reinforced concrete members, it is necessary to allow for relatively large ductility so that the seismic energy is absorbed to avoid shear failure or significant degradation of strength even after yielding of reinforcing steels in the concrete member occurs. Therefore, prediction of the ductility should be as accurate as possible. The principal aim of this paper is to present the basic data for the ductility evaluation of reinforced high-strength concrete beams. Accordingly, 23 flexural tests were conducted on full-scale structural concrete beam specimens having concrete compressive strength of 40, 60, and 70MPa. The test results were then reviewed in terms of flexural capacity and ductility. The effect of concrete compressive strength, web reinforcement ratio, tension steel ratio, and shear span to beam depth ratio on ductility were investigated experimentally.

• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.93-104
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• 2018

The seismic behavior of reinforced concrete (RC) short columns with limited transverse reinforcement is investigated in this paper through an experimental program. The experimental program consists of four small-scale RC columns with an aspect ratio of 1.7, which are tested to the axial failure stage. The cracking patterns, hysteretic responses, strains in reinforcing bars, displacement decomposition and cumulative energy dissipation of the tested specimens are reported in detail in the paper. The effects of column axial load are investigated to determine how this variable might influence the performance of the short columns with limited transverse reinforcement. Brittle shear failure was observed in all tested specimens. Beneficial and detrimental effects on the shear strength and drift ratio at axial failure of the test specimens due to the column axial load are found in the experimental program, respectively.