• 한국생산제조학회지
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• 제21권6호
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• pp.892-896
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• 2012

CFRP composites with light weight, high strength, and high elasticity by comparing with metal are widely used rather than previous steel plates. However, CFRP composite material has the weakness at hydrothermal and collapsed impact environment. Especially, moisture absorption into composite material can change molecule arrangement and chemical properties under hydrothermal environment. And static collapse experiment is the research in the differences of absorbed energy and deformation mode between moisture and non-moisture absorbed specimens. This study is compared and analyzed on the progress change of moisture absorption ratio after setting up the temperatures of 60 and 80 degrees C in order to comprehend how the change in the temperature influences on moisture absorption status inside CFRP composite materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.471-474
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• 2005

This thesis presents the results of a study on improvement in flexure capacities of reinforced concrete beams strengthened with prestressed CFRP plates. Test variables included the type of strengthening, steel ratio and prestressing level. The experimental results show that proposed methods can increase the flexure capacity such as strength, stiffness of the beam remarkably.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.323-327
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• 1996

Reinforced concrete(R/C) structures need repair and rehabilitation due to the deterioration such as a crack, spalling and disintergration. Numerous repair materials which are currently used in construction fields without any regulation are examined in terms of their serviceabilities and effectiveness. In this paper section of existing R/C beams are enlarged with repair materials, that is, epoxy, latex or premix. And then they are strengthened with rebar, steel poate of CFRP on the tension face. Structural behaviors of strengthened beams are investigated both statically and dynamically and they are compared with each. This paper summarizes the overall research plan.

• 콘크리트학회논문집
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• 제20권5호
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• pp.611-618
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• 2008

CFRP (carbon fiber reinforced polymer) 긴장재는 PS 강연선의 부식문제를 해결하기 위해 대안으로 사용될 수 있다. CFRP 긴장재는 횡방향 압력 및 응력집중에 취약하므로 기존의 PS 강연선에 적용되는 정착시스템의 적용은 조기파괴 등으로 인하여 믿을만한 내하성능을 주지 못한다. 따라서 CFRP 긴장재를 정착하기 위한 알맞은 정착장치의 개발이 필요하다. CFRP 긴장재용 정착구의 주된 형태는 쐐기형, 부착형 및 압착형으로 구분되며 이들 형태는 CFRP 긴장재에서 발생되는 조기파단을 방지하고 국부응력을 적절히 분산시키기 위한 목적으로 개발되고 있다. 본 논문은 CFRP 긴장재를 정착시키기 위해 압착형 정착방식을 적용하여 응력집중을 완화시키기 위해 슬리브 내외경에 변단면을 적용하고, 변단면 길이에 따른 압착형 정착구의 정착성능을 고찰하였다. 실험결과 정착구의 성능은 슬리브 제원과 압착력에 크게 좌우되는 것으로 나타났고, 응력완화구간을 갖는 슬리브는 응력집중을 감소시키는 것으로 나타났다.

• 한국기계가공학회지
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• 제16권4호
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• pp.83-88
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• 2017

Recently, the use of advanced materials with light weight significantly increases because of global regulation on CO2 emission. Especially, CFRP (carbon fiber reinforced plastics) one of the most promising advanced materials. Since CFRP has pretty higher strength per unit weight than steel, it is one of most popular materials in aviation industry and its application to automobile rises sharply. Especially, one of the frequent machining processes for CFRP is drilling to make a hole, however, CFRP drilling has troublesome limitations in hole quality and productivity induced due to delamination, splintering and severe tool wear. Particularly, cutting loads increase caused by tool wear makes delamination and splintering even severer. Therefore, tool wear monitoring or reduction in CFRP drilling must be considered seriously. In this study, we measured thrust force, flank wear, and tool surface temperature in drilling using various tools with different sizes and materials. Consequently, it was presented the effects of tool properties on drilled hole quality, thrust force and tool surface temperature.

• Advances in concrete construction
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• 제10권2호
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• pp.151-159
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• 2020

An experimental study on the stress-strain relation of PVC-CFRP confined reinforced concrete columns subjected to eccentric compression was carried out. Two parameters, such as the CFRP strips spacing and eccentricity of axial load, were considered. The experimental results showed that all specimens failed by compressive yield of longitudinal steel bar and rupture of CFRP strips. The bearing capacity of specimen decreases as the eccentricity or the CFRP strips spacing increases. The stress-strain relation of specimens undergoes two stages: parabolic and linear stages. In the parabolic stage, the slope of stress-strain curve decreases gradually as the eccentricity of axial loading increases while the CFRP strips spacing has little effect on the slope of stress-strain curve. For the linear stage, the slope of stress-strain curve decreases as the eccentricity of axial load or the CFRP strips spacing increases. A model for predicting the stress-strain relation of columns under eccentric compression is proposed and it agrees well with various test data.

• Steel and Composite Structures
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• 제11권3호
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• pp.207-223
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• 2011

The results of an experimental investigation are presented in this paper for retrofitting of shear damaged reinforced concrete beams by using U shaped CFRP strips. The experimental program is consisted of seven shear deficient T cross sectioned 1/2 scale simply supported beam specimens. One beam was used as reference specimen, and the remaining six specimens were tested in two stages. At the first stage, specimens were shear damaged severely, and then were retrofitted by using CFRP strips with or without fan type anchorages. Finally, retrofitted beams were tested up to failure. Three different CFRP strip spacing were used such as 125 mm, 150 mm, and 200 mm. The effect of anchorages on shear strength and behavior of the retrofitted specimens is investigated. CFRP strips without anchorages improved the shear strength, but no flexural failure mode was observed. Specimens showed brittle shear failure due to peeling of CFRP strip from RC beam surface. Shear damaged specimens retrofitted with anchoraged CFRP strips showed improved shear strength and ductile flexural failure. Maximum strains at anchoraged strips were approximately 68% larger than that of strips without anchorages.

• Computers and Concrete
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• 제33권4호
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• pp.385-398
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• 2024

As concrete dominates the construction industry, alternatives to traditionally used steel reinforcement are being sought. This study explored the suitability of carbon fiber-reinforced polymer (CFRP) as a substitute within rigid frames, focusing on its impact on section ductility and overall structural durability against seismic events. However, current design guidelines address quasi-static loads, leaving a gap for dynamic or extreme circumstances. Our approach included multiscale simulations, parametric study, and energy dissipation analyses, drawing upon a unique adaptation of modified compression field theory. In our efforts to optimize macro and microparameters to improve yield strength, manage brittleness, and govern failure modes, we also recognized the potential of CFRP's high corrosion resistance. This characteristic of CFRP could significantly reduce the frequency of required repairs, thereby contributing to enhanced durability of the structures. The research reveals that CFRP's durability and seismic resistance are attributed to plastic joints within compressed fibers. Notably, CFRP can impart ductility to structural designs, effectively balancing its inherent brittleness, particularly when integrated with quasi-brittle materials. This research challenges the notion that designing bendable components with carbon fiber reinforcement is impractical. It shows that creating ductile bending components with CFRP in concrete is feasible despite the material's brittleness. This funding overturns conventional assumptions and opens new avenues for using CFRP in structural applications where ductility and resilience are crucial.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.249-252
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• 2008

이 논문에서는 비부착 CFRP 판으로 긴장된 RC(Reinforced Concrete) 보의 비선형 해석방법을 제시하였다. 하중 재하 시 부재의 단면 내에서 변화하는 재료상태를 정확히 예측하기 위해 철근콘크리트 뼈대는 콘크리트와 보강철근 화이버로 구성된 화이버모델요소로 이상화하였다. 또한 CFRP 판의 비부착 거동을 모사하기 위해 CFRP 판을 뼈대요소의 각 절점에 연결되는 여러 개의 요소로 이상화하되, 연결부에서 슬립이 가능한 것으로 가정하여 슬립으로 인한 CFRP 판의 인장력을 반복적으로 보정함으로써 CFRP 판요소들의 응력이 같도록 하였다. 이 논문에서 제시한 해석방법의 정당성을 검토하기 위해 비부착 CFRP 판으로 긴장된 RC 보의 극한해석을 수행하여 해석결과를 타 연구자의 실험결과와 비교해 본 결과, 두 연구결과가 잘 일치함을 확인하였다.

• Computers and Concrete
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• 제27권1호
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• pp.41-54
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• 2021

This paper introduced three new strengthening systems for isolated footings: BFRP wrapping system, CFRP wrapping system, and steel jacketing system. The proposed systems are more practical than the current traditional methods, which involves installing many dowel bars and splicing reinforcing steels to join new and old concrete segments. In the proposed three new systems, BFRP wraps, CFRP wraps, or steel jackets are installed on the exterior surface of the enlarged footing, with construction adhesive or a few steel dowels being applied to the contact surfaces. To investigate the effectiveness of three systems, forty-four models were constructed in ABAQUS, with different parameters being considered. All footings investigated failed in punching shear, including original and retrofitted footings. According to FEA results and parametric studies, the three strengthening systems were capable of improving the punching shear resistance of footings. By introducing a new factor η, the punching shear equation in Eurocode 2 was modified to predict the punching shear resistances of the strengthened footings. A linear formula was developed to present the relationship between the new factor η and the investigated parameters.