• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.141-144
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• 2006

The main purpose of this study is to develop a Sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing carbon or glass shot fibers and the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the Sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of Sprayed FRP, this study carried out tensile tests of the material specimens which are changed with the combinations of various variables such as the length of shot fiber and mixture ratio of shot fiber and resin. These variables are set to have the material strength equal to one layer of the FRP sheet. As a result, the optimal length of glass and carbon shot fibers were derived into 3.8cm, and the optimal mixture ratio was also deriver into 1:2 from each variable. And also, the thickness of Sprayed FRP to have the strength equal to one layer of FRP sheet was finally calculated.

• 비파괴검사학회지
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• 제27권2호
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• pp.115-123
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• 2007

본 연구에서는 탄소섬유로 보강된 콘크리트의 전기저항 변화를 모니터링하는 방법에 의해, 콘크리트의 파괴에 대한 자가진단 적용 특성을 검토하였다. 미분쇄 탄소섬유와 코크스 분체로 구성된 신형 리브재가 포함된 CFGFRP (탄소섬유 유리섬유 강화 플라스틱)와 콘크리트 보강용 CF(탄소섬유) 시트에 휨 하중 재하 단계별로 하중을 가할 때 균열 또는 파괴가 발생하기 전후의 탄소섬유의 전기저항 변화를 조사하여, 각 인자의 관계특성(각 하중단계별 전기저항, 변형률, 처짐 등의 변화)을 분석하였다. 그 결과, 콘크리트 인장측 파괴시 탄소섬유 보강근, 신형 리브, 시트가 파괴될 때, 전기저항은 크게 증가하지만, CFGFRP의 경우는 그 후 하이브리드 FRP 재료 중 탄소섬유를 보강하고 있던 유리섬유가 나머지 추가 재하 하중에 저항할 수 있어 콘크리트 시험체의 전 파괴단계에까지는 이르지 않았다. 따라서 CFGFRP의 보강근과 신형 리브, CF시트는 FRP로 보강된 콘크리트의 파괴를 사전에 감지할 수 있는 자가진단 재료로서의 적용이 가능함을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권5호
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• pp.1-9
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• 2022

이 연구에서는 Hwang et al.(2021a, 2021b)가 제시한 강봉 트러스 시스템과 FRP 시트로 보강된 조적벽체의 면내·외 내진성능을 비교평가하였다. 면내·외 가력에서 FRP 시트로 보강된 조적벽체의 최대 내력은 각각 무보강 조적벽체의 71% 및 85% 수준으로 순수 조적벽체의 내력을 발휘하지 못하고 더 낮은 내진 성능을 보였다. 강봉 트러스 시스템으로 보강된 조적벽체의 최대 내력은 무보강 조적벽체에 비해 약 1.8배 높았다. 강봉 트러스 시스템은 FRP 시트 부착 공법에 비해 최대 내력, 강성, 에너지 소산능력 향상에 뛰어났다. 하지만, FRP 시트로 보강된 조적벽체의 경우, FRP시트를 조적벽체의 전체에 보강함으로써 조적벽체가 과보강되었고, 실험체가 미끄러짐 파괴가 발생 강성발현 증가효과가 미미한 것으로 판단된다. 추후, FRP 시트를 조적벽체의 일부분만 보강한 실험체와 강봉 트러스 시스템으로 보강한 실험체의 내진성능을 비교하는 후속연구가 필요하다.

• Structural Engineering and Mechanics
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• 제72권3호
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• pp.305-312
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• 2019

This paper investigates the effect of utilizing vacuum bagging process to enhance the bond behavior between fiber reinforced polymer (FRP) composites and concrete substrate. Sixty specimens were prepared and tested using double-shear bond test. The effect of various parameters such as vacuum, fiber type, and FRP sheet length and width on the bond strength were investigated. The experimental results revealed that utilizing vacuum leads to improve the bond behavior between FRP composites and concrete. Both the ultimate bond forces and the maximum displacements were enhanced when applying the vacuum which leads to reduction in the amount of FRP materials needed to achieve the required bond strength compared with the un-vacuumed specimens. The efficiency of the enhancement in bond behavior due to vacuum highly depends on the fiber type; using carbon fiber showed higher enhancement in the bond strength compared to the glass fiber when vacuum was applied. On the contrary, specimens with glass fiber showed higher enhancement in the maximum slippage compared to specimens with carbon fibers. Utilizing vacuum does not affect the debonding failure modes but lead to increase in the amount of attached concrete on the surface of the debonded FRP sheet.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.84-87
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• 2004

Nominal flexural strength of RC members strengthened with FRP sheets is generally based on the tensile strength of composite materials obtained from coupon tests. This method is based on the assumption that bond failure does not occur until the FRP sheet reaches its rupture strength. According to the previous researches, however, bond failure often occurs before the FRP sheet reaches its rupture strength. Some attempts were made to control debonding failure by increasing the bonded length of sheet or wrapping the section around their side of the member(U-wrap). In this study, the flexural failure mechanism of RC beams strengthened with AFRP sheets with different bond lengths is investigated. Their strengthening details to prevent the premature debonding failure are also suggested and its effectiveness is verified.

• 비파괴검사학회지
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• 제27권2호
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• pp.134-141
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• 2007

중심주파수가 15 GHz이고, 대역폭이 1 GHz인 마이크로 스트립 패치 안테나를 이용하여, 탄소섬유시트로 보강된 콘크리트의 계면박리를 탐사하는 실험을 실시하였다. 개발된 안테나의 성능을 비교하기 위하여, 중심주파수 15 GHz, 대역폭 10 GHz인 상용 horn 안테나를 이용하여 비교실험을 실시하였다. 실험에 사용된 시편은 $600\;{\times}\;600\;{\times}\;50\;mm$의 크기를 가지며, 그 표면에 1.5 mm 두께의 FRP 시트를 3 mm 두께의 에폭시로 부착하였으며, 5, 10, 15 mm 두께의 박리를 인공적으로 형성하였다. 실험결과 5, 10, 15 mm 박리 모두 측정이 가능하였으며, 측정은 보강구역과 무보강구역을 구분하여 이루어 졌다.

• Structural Engineering and Mechanics
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• 제72권6호
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• pp.723-736
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• 2019

The efficacy of a technique for the rehabilitation and strengthening of RC beam-column connections damaged due to cyclic loading was investigated. The repair mainly uses epoxy resin infused under pressure into the damaged region to retrieved back the lost capacity and then strengthening using fiber reinforced polymer (FRP) sheets for capacity enhancement. Three common types of reduced scale RC exterior beam-column connections namely (a) beam-column connection with beam weak in flexure (BWF) (b) beam-column connections with beam weak in shear (BWS) and (c) beam-column connections with column weak in shear (CWS) subjected to reversed cyclic loading were considered for the experimental investigation. The rehabilitated and strengthened specimens were also subjected to similar cyclic displacement. Important parameters related to seismic capacity such as strength, stiffness degradation, energy dissipation, and ductility were evaluated. The rehabilitated connections exhibited equal or better performance and hence the adopted rehabilitation strategies could be considered as satisfactory. Confinement of damaged region using FRP sheet significantly enhanced the seismic capacity of the connections.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.185-188
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• 2006

Recently, an improved capacity for RC bridges is required by their deterioration or necessary to carry traffic increase. Strengthening is known as a better way to improve capacity of bridges than reconstructing. Fiber Reinforced Plastics (FRP) is introduced as one of the best strengthening structures in this paper. It is also known as an economical improvement. Therefore, FRP sheet and Glass Fiber-Steel Composite Plate (GSP) in this research were used in strengthening slab of RC bridges. Experimental data from the strengthening will be helpful to better understand the slab behavior and an effect of the strengthening.

• 한국구조물진단유지관리공학회 논문집
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• 제11권6호
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• pp.95-102
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• 2007

교량의 노후화와 교통량의 증가로 성능개선이 요구되어 질 경우, 경제적인 측면에서 신축 보다는 보수 보강을 통한 성능개선이 보다 바람직한 유지관리이다. 많은 보강공법중 시공방법의 편리와 빠른 시공기간으로 교량의 성능향상을 위해 FRP 재료를 이용한 표면부착공법이 많이 이용되고 있다. 특히, FRP 재료는 철근보다 경량이고 인장강도는 약 10배정도 우수한 재료이다. 이를 이용한 보강성능을 평가하기 위하여 CFRP 쉬트와 GSP를 이용하여 실험을 수행하였다.

• Structural Engineering and Mechanics
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• 제87권6호
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• pp.517-527
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• 2023

The severe deterioration of structures has led to extensive research on the development of structural repair techniques using composite materials. Consequently, previous researchers have devised various analytical methods to predict the interface performance of bonded repairs. However, these analytical solutions are highly complex mathematically and necessitate numerous calculations with a large number of iterations to obtain the output parameters. In this paper, an artificial neural network prediction models is used to calculate the interfacial stress distribution in RC beams strengthened with FRP sheet. The R2value for the training data is evaluated as 0.99, and for the testing data, it is 0.92. Closed-form solutions are derived for RC beams strengthened with composite sheets simply supported at both ends and verified through direct comparisons with existing results. A comparative study of peak interfacial shear and normal stresses with the literature gives the usefulness and effectiveness of ANN proposed. A parametrical study is carried out to show the effects of some design variables, e.g., thickness of adhesive layer and FRP sheet.