• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.151-159
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• 2015

In this study, experimental research was carried out to evaluate and improve the seismic performance of reinforced concrete beam-column joint regions using strengthening materials (CFRP sheet, AFRP sheet, embedded CFRP rod) in existing reinforced concrete structure. Therefore it was constructed and tested seven specimens retrofitting the beam-column joint regions using such retrofitting materials. Specimens, designed by retrofitting the beam-column joint regions of existing reinforced concrete structure, were showed the stable failure mode and increase of load-carrying capacity due to the effect of crack control at the times of initial loading and confinement of retrofitting materials during testing. Specimens LBCJ-CRUS, designed by the retrofitting of CFRP Rod and CFRP Sheet in reinforecd beam-column joint regions were increased its maximum load carrying capacity by 1.54 times and its energy dissipation capacity by 2.36 times in comparison with standard specimen LBCJ for a displacement ductility of 4 and 7. And Specimens LBCJ-CS, LBCJ-AF series were increased its energy dissipation capacity each by 2.04~2.34, 1.63~3.02 times in comparison with standard specimen LBCJ for a displacement ductility of 7.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.4
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• pp.38-44
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• 2012

This paper presents experimental studies aiming at evaluation of structural behaviors of RC (Reinforced Concrete) beams externally strengthened with taper ended CFRPs(Carbon Fiber Reinforced Polymers). Experiments are performed with RC beams having different numbers of CFRP layers and length of each layer. The beams are subjected to four point-bending with simply supported condition. Test results of taper ended CFRPs and non-tapered CFRPs are compared and the better strengthening effect is observed from tapered ended CFRPs.

• Journal of the Korean Institute of Rural Architecture
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• v.6 no.3
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• pp.106-115
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• 2004

In this paper, the compressive strength and ductility enhancement of concrete by lateral confinement of carbon-fiber sheets(CFS) have been studied experimentaly with cylinder specimens and square short columns reinforced externally by CFS. Test variables were amount of lateral reinforcement by CFS and space of hoop bars. Test results showed that lateral reinforcements by carbon-fiber sheets provided lateral confinement successfully for the concrete specimens and were more effective for ductility enhancement than for strength increase, and that the lateral confinement coefficient of cabon-fiber sheets increased according to narrowing the space of hoop bars in the double lateral confinement made by CFS and hoop bars.

• Magazine of the Korea Concrete Institute
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• v.14 no.2
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• pp.45-50
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• 2002

근년, 철근 콘크리트조 구조부재의 열화 및 건축물의 용도변경에 따라 건축물의 보수 및 보강에 관한 공법의 개발 및 그 효과를 검증하려는 연구가 활발히 진행되고 있다. 이에 따라, 보강공법으로서는 경제성ㆍ시공성 면에서 우수한 탄소섬유시트, 아라미드섬유 시트, 유리섬유시트 보강공법 및 FRP판 보강공법 등 합성수지 접착제를 사용하는 새로운 보강공법들이 폭넓게 연구되어 현장 실용화되어 사용 중에 있다. 그러나, 이들 보강공법에 관한 연구는 주로 구조적인 내력 보강효과 산정에 관한 것이 대부분이고 보강후의 내화성능 및 내구성능에 관한 연구는 매우 부족한 실정이다. 이들 보강공법은 주로 에폭시수지계 접착제에 의하여 콘크리트와 보강재의 접착력에 의하여 내력이 전달되는 메커니즘으로 되어있어 화재가 발생한 경우 내화피복이 없다면 접착제 자체의 연소에 의하여 유독가스의 발생 및 접착강도가 크게 저하되어 그 구조적인 보강성능은 급속히 저하할 것으로 판단된다. 또한, 현재 이들 보강공사는 내화성능의 검토 없이 실제 시공이 이루어지고 있으므로 화재시에는 대형참사를 일으킬 위험성이 있다.(중략)

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.359-362
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• 2003

Carbon fiber sheet is attractive due to its good tensile strength, resistance to corrosion, and low weight. The strengthening of concrete structures with externally bonded carbon fiber sheets is increasingly being used for repair and rehabilitation of existing structures. However CFS strengthened beams break down under the service loads. As rupture strain is not reached ultimate value, reduction of the tensile strength is recommended. This study evaluate CFS tensile strength reduction factor which is required to analyze bending moment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.147-156
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• 2004

The Rehabilitation and repair of structurally deteriorated, reinforced concrete structures will be highly demanded in the near future. The purpose of this study is to investigate whether damaged beams that crack and deflection are developed by bending moment are restored to the former state. In conclusion, when specimens strengthened with Steel Plate, CFS(Carbon Fiber Sheet) and CFRP-Grid(Carbon Fiber Reinforced Plastic-Grid) are compared with standard specimen, flexural capacity is increased and ductility and energy absorbtion capacity are similar with undamaged specimen. Therefore Steel Plate, CFS(Carbon Fiber Sheet) and CFRP-Grid (Carbon Fiber Reinforced Plastic-Grid) have highly efficiency as material of flexural strengthening.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.1
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• pp.23-27
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• 2016

This study investigates the effect of carbon fiber sheet (CFS) and carbon fiber strand sheet (CFSS) on the fatigue resistance and compressive strength of RC slabs. The results of a comparison of the number of equivalent cycles between the CFS- and CFSS-reinforced RC slab test specimens obtained from a fatigue test indicate that the CFSS-reinforced RC slab has 1.2~1.3 times greater effect of reinforcement than the CFS-reinforced RC slab. This study also indicates that the fatigue resistance of the CFS- and CFSS-reinforced RC slabs is ensured when the compressive strength of concrete is not lower than the specified design strength prescribed in the Specifications for Highway Bridges but is not ensured when the compressive strength of concrete is lower than the specified design strength, although the effect of reinforcement is secured.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.2
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• pp.133-139
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• 2003

In order to extend the life time of building and civil infra-structure, nowadays, patch type fibrous composite materials are widely used. Repaired concrete columns and beams gain the stiffness and strength, but they lose toughness and show brittle failure. Usually, the cracks of concrete structures are visible with naked eyes and the status of the structure in the life cycle is estimated with visible inspection. After repairing of the structure, crack visibility is blocked by repaired carbon sheets. Therefore, structural monitoring after repairing is indispensible and self diagnosis method with optical fiber sensor is very useful. In this paper, peel-out effects is detected with optical fiber sensors and the strain difference between main structure and repaired carbon sheets when they separate each other.

• The Journal of the Korea Contents Association
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• v.18 no.11
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• pp.455-461
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• 2018

This paper presents experimental investigations about flexural strength and durability of reinforced concrete beams repaired using ductile fiber reinforced cementitious composite (DFRCC) and carbon fiber sheet through freezing and thawing test. Total 14 RC beams of $100{\times}100{\times}400mm$ size were tested by 3-point bending and freezing and thawing test by KS F 2456. The beams were reinforced using 3D10 steels on both the tensile and compressive sides, and repaired on 3 sides expect on top cycle. Test results showed that the beams repaired using fiber carbon sheet revealed about 15% higher values of flexural strength compared than the cases of DFRCC motar. On the other hand, the results did not showed meaningful differences in the aspect of durability. For further research, consideration of the steel interference effect and real old specimens such as taken from real deteriorated structures are needed to be tested after repairing with DFRCC and carbon fiber sheet.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.134-141
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• 2007

A series of experimental work has been conducted to evaluate the capability of microstrip patch antenna system in detecting delamination in fiber reinforced Plastic (FRP) sheet reinforced concrete. For that purpose, a prototype microstrip patch antenna was developed with 15 GHz center frequency and 1 GHz bandwidth. For the comparison, a horn antenna with 15 GHz center frequency and 10 GHz bandwidth was used for the measurements of the same specimens. The laboratory sire specimens have the dimensions of 600 mm (length) $\times$ 600 mm (width) $\times$ 50mm (thickness) with a series of delaminations of 300 mm (length) $\times$ 300mm (width) $\times$ 5, 10, 15 mm (thickness). FRP of 1.5 mm thickness and epoxy of 3 mm thickness were placed on the top of artificially created delamination to represent actual FRP reinforced concrete condition. In all cases, the delamination has deen successfully identified. Also, it was shown that imaging results in microstrip patch antenna were improved by signal processing.