• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.36-41
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• 2011

This study proposes a experimental method to evaluate bonding strength of FRPs used for retrofitting concrete structures. Specimens are designed so that debonding failure of FRPs can be induced from reinforced concrete beams retrofitted with two layers of carbon and glass FRPs. And three-point loading tests are performed to see if debonding failure with proper debonding strength is observed from the specimens. The test results show that the tested beams are failed due to debonding of FRPs, therefore, the proposed test method is capable of evaluating debonding strength of FRPs using relatively small normal strength concrete beams.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.177-182
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• 1999

사용한 보수.보강재, Rod, Fabric, Strand 형상을 콘크리트 구조물등에 보강재로 사용되어왔다. 이 재료는 해양환경하에서 내식성과 내구성을 갖는 철근및 철골대체용 복합소재와 초고층 경량 연속섬유보강 시멘트 복합재료는 탄소섬유, 아라미드섬유, 유리섬유등의 쉬트(sheet)형상을 신건재, 비자성, 비전도성, 전파차폐용 재료등에 사용할수있다. 그러나 FRP Rod를 내식성이 요구되는 철근 및 철골대체재로 사용할 경우에는 폴리머 매트릭스의 열화, 섬유와 폴리머간 계면 접착강도의 한계, 화재시 내화성, 보강재의 인발성등의 단점들을 갖고있다[1]. (중략)

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.483-491
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• 2008

The effectiveness of a new fiber-steel composite plate designed specifically to be used for strengthening of reinforced concrete members has been investigated. Twelve reinforced concrete beams were tested. Seven of the beams were strengthened with carbon fiber-steel composite plate(CSP), four of the beams were strengthened with glass fiber-steel composite plate(GSP), and one beam was used as a control specimen. The experimental results showed that new strengthening system controls the premature debonding and provides a more ductile failure mode than other conventional strengthening systems. The observed ductility ratios were $3.01\sim3.81$ and $3.55\sim4.95$ for strengthened beam with CSP and GSP, respectively. The maximum load was increased by 115% and 107% for strengthened beam with CSP and GSP, respectively, comparing with control beam. In addition, experimental and analytical results were well agreed.

• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.113-120
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• 2005

The purpose of this study is to investigate the strength and ductility improvement of columns retrofitted by steel-fiber composite plate. Test specimens strengthened by three different materials - steel plate(SP), carbon fiber sheet(CF) and fiber-steel composite plate(CP) - were tested under cyclic lateral load with a constant axial load equal to $20\%$ of the axial compression capacity. The structural capacity of composite plate was good or better than that of other retrofitting materials. Test results from all retrofitted specimens showed that considerably higher retrofitting amount was required for strength enhancement. The ductility of retrofitted columns by composite plate was fairly improved. Also, energy ductility ratio was more effective than displacement ductility ratio for ductility estimation of retrofitted column.

• Journal of the Korean Geosynthetics Society
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• v.9 no.2
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• pp.41-50
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• 2010

The concrete lining of a tunnel constructed by NATM used to be regarded as facing material which does not support any load from the surrounding ground. But the recent appraisal of the decrepit tunnels revealed that rockbolts and shotcrete deteriorate with time resulting in loss of supporting capability. Consequently, concrete lining has to support part of the load which used to be supported by rockbolts and shotcrete, and thus should be regarded as the final supporting structure in a tunnel. One of the common, and perhaps the most serious problem in concrete lining is the longitudinal cracks taking place at the tunnel crown. The longitudinal cracks, mostly related to the construction procedures, can be developed by many reasons such as the lack of thickness, wrong materials, bad curing environment, and excessive external forces. Many efforts has been made to control and suppress these cracks but efficient and economic way is yet to be found. For efficient crack control in concrete lining, reinforcement by composite fibers, which is the mixture of steel fiber and nylon fiber, is suggested in this study.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.101-104
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• 2008

The cost of repairing the deterioration of concrete structures due to corrosion of the reinforcement steel has been the prominent figure in the maintenacne of the reinforced-concrete infrastructures. As an alternative material to steel reinforcement, the use of Fiber Reinforced Polymer (FRP) bar in concrete is being actively studied for the high resistance of chemical environment and high strength to weight ratio properties of FRP. However, there remain various aspects of FRP properties that still need to be studied before the standard design criteria can be established. One of the imminent issues is the bond between FRP and concrete. In this study, the bond-behavior of FRP bars in concrete is investigated via the pullout test with three varying parameters: surface condition of FRP bars, concrete compression strength, and cyclic loading patterns. As a result of experiment, the bond strength of GFRP increased with the concrete compression strength increasing and decreased with applying cyclic load.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.160-170
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• 2002

Many of aged and damaged concrete structure have been revitalized with composite reinforcement. Flexural behaviors of composite-patched concrete specimens are characterized by high-sensitivity moire interferometry. The three-mirror, four-beam interferometry system and a compact loading system are used for obtaining singe patterns representing whole-field contour maps of in-plane displacements. It is seen from the calibration test for the loading system that the measured bending displacement is in excellent agreement with the displacement calculated by the beam theory. The crack opening displacement as well as the bending and the horizontal displacement fur the notched and unnotched specimen are investigated. The results also show that the notched specimen reinforced by a composite sheet has sufficient stiffness and strength compared to the original concrete specimen.

• Land and Housing Review
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• v.15 no.3
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• pp.141-151
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• 2024

This paper presents the results of an experimental study to evaluate the shear behavior of reinforced concrete beams reinforced with FRCM composites using different types of textile grids. It was found that the shear behavior of reinforced concrete beams with FRCM composites was observed by comparing the strains measured in the stirrups and textile grids. It was found that the ultimate strength of the strengthened specimens increased compared to the basic specimens, and the failure mode at ultimate strength changed from shear failure to bending failure. When the shear strength design values of the KDS 14 20 22 and AIJ ultimate strength types were compared with the actual experimental values, it was found that the AIJ ultimate strength type was more accurate. In addition, the shear contribution of FRCM composites in the A and T models was compared, and the results showed that both models had similar trends. Reflecting these results, it is recommended that further studies should be conducted to calculate the shear performance of beam members with FRCM composites and the shear contribution of FRCM composites by using the stirrup reinforcement ratio and the type of textile grid as variables.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.133-136
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• 2008

The cost of repairing the deterioration of concrete structures due to corrosion of the reinforcement steel has been the prominent figure in the maintenacne of the reinforced-concrete infrastructures. As an alternative material to steel reinforcement, the use of Glass Fiber Reinforced Polymer (GFRP) bar in concrete is being actively studied for the high resistance of chemical environment and high strength to weight ratio properties of GFRP. However, there remain various aspects of GFRP properties that still need to be studied before the standard design criteria can be established. One of the imminent issues is the bond between GFRP and concrete. In this study, the bond-behavior of GFRP bars in concrete is investigated via the pullout test with varying parameters: surface condition of GFRP bars and concrete compression strength. And the local bond-stress model of GFRP rabars with applying monotonc load was also derived from the present test.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.2
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• pp.20-28
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• 2010

In this paper, new type CFFT (Concrete Filled FRP Tube) was suggested in order to improve the flexural stiffness. Since the existing CFFT was produced by filament winding process, re-bar for concrete may be necessary in order to ensure structural safety under flexure re-bar. In comparison with existing type CFFT, new type CFFT was reinforced by circular shaped pultrusion FRP without re-bar. Filament winding FRP was attached to the outer layer of pultrusion FRP. Structural behavior of new type CFFT filled with concrete (HCFFT) was investigated by the mechanical property test for the component element and the FE analysis. Furthermore, compressive strength of the HCFFT member based on the equation suggested in previous studies.