• 한국안전학회지
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• 제25권3호
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• pp.71-77
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• 2010

This paper presents the results of a study on flexural capacity of large size RC slabs strengthened with carbon fiber reinforced polymer(CFRP) plates. A total of 5 specimens of 6.0m length were tested in four point bending after strengthening them with externally bonded CFRP plates. The CFRP plates were bonded without prestress and with two prestress levels, 0.4% and 0.6% of CFRP plate strain. Test variables included the type of strengthening, prestressing level, and the effects according to each test variables are analysed. The experimental results show that proposed methods can increase significantly the flexural capacity such as strength, stiffness of the beam and the increase ranged between 36.2% and 63.2% of the load-carrying capacity of the control beams. The non-prestressed specimen failed by separation of the plate from the beam due to premature debonding while most of the prestressed specimens failed by CFRP plate fracture. And the cracking loads and maximum loads were increased proportionally to the prestress level.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.262-265
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• 2006

This paper presents results on static and cyclic loading tests of anchorage system for externally prestressed CFRP plate. A total of 6 specimens have been tested. The specimens can be classified into the concrete surface specimens and the concrete near surface mounted specimens. Static test results before and after cyclic loading test reveal that anchorage system for externally prestressed CFRP plate has static capacity more than CFRP tensile strength.

• Carbon letters
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• 제23권
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• pp.1-8
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• 2017

Polycrystalline diamond (PCD) tools possessing high hardness and abrasive wear resistance are particularly suited for drilling of carbon fiber reinforced plastic (CFRP) composites, where tool life and consistent hole quality are important. While PCD presents superior performance when drilling CFRP, it is unclear how it performs when drilling multi-stack materials such as CFRP-titanium (Ti) stacks. This comparative study aims to investigate drilling of a Ti plate stacked on a CFRP panel when using PCD tools. The first sequence of the drilling experiments was to drill 20 holes in CFRP only. CFRP-Ti stacks were then drilled for the next 20 holes with the same drill bit. CFRP holes and CFRP-Ti stack holes were evaluated in terms of machined hole quality. The main tool wear mechanism of PCD drills is micro-fractures that occur when machining the Ti plate of the stack. Tool wear increases the instability and the operation temperature when machining the Ti plate. This results in high drilling forces, large hole diameter errors, high surface roughness, wider CFRP exit thermal damage, and taller exit Ti burrs.

• Structural Engineering and Mechanics
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• 제84권3호
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• pp.375-391
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• 2022

This paper discussed and analyzed the interfacial stress distribution characteristic of adjacent cracks in Carbon Fiber Reinforced Polymer (CFRP) plate strengthened concrete slabs. One un-strengthened concrete test beam and four CFRP plate-strengthened concrete test beams were designed to carry out four-point flexural tests. The test data shows that the interfacial shear stress between the interface of CFRP plate and concrete can effectively reduce the crack shrinkage of the tensile concrete and reduces the width of crack. The maximum main crack flexural height in pure bending section of the strengthened specimen is smaller than that of the un-strengthened specimen, the CFRP plate improves the rigidity of specimens without brittle failure. The average ultimate bearing capacity of the CFRP-strengthened specimens was increased by 64.3% compared to that without CFRP-strengthen. This indicites that CFRP enhancement measures can effectively improve the ultimate bearing capacity and delay the occurrence of debonding damage. Based on the derivation of mechanical analysis model, the calculation formula of interfacial shear stress between adjacent cracks is proposed. The distributions characteristics of interfacial shear stress between certain crack widths were given. In the intermediate cracking region of pure bending sections, the length of the interfacial softening near the mid-span cracking position gradually increases as the load increases. The CFRP-concrete interface debonding capacity with the larger adjacent crack spacing is lower than that with the smaller adjacent crack spacing. The theoretical calculation results of interfacial bonding shear stress between adjacent cracks have good agreement with the experimental results. The interfacial debonding failure between adjacent cracks in the intermediate cracking region was mainly caused by the root of the main crack. The larger the spacing between adjacent cracks exists, the easier the interfacial debonding failure occurs.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.41-44
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• 2007

In repairing and reinforcing modem architecture, altering the features must be minimized. We concluded that inserting CFRP(Carbon Fiber Reinforcement Polymer) plate method is the most appropriate reinforcing method that minimize altering the features. This study focuses on the effect of reinforcement by inserting CFRP plate in the timber beam of the modem architecture's roof truss. We concluded that inserting CFRP plate method is highly influenced by its parent material, however, it is obvious that materials had reinforced by this method in general. We guess that this method is applicable to reinforcement in the modern architecture's roof truss in various ways.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.399-404
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• 2002

This paper presents the results cf research on improved flexural performance cf reinforced concrete beams strengthened with bonded carbon fiber reinforced polymer plate. Recently, strengthening technique with CFRP plate were almost carried out by external bonding. But current external bonding technique cf CFRP plates may result in debonding CFRP plate. Therefore, this study proposes a strengthening method that prevents or delays debonding between CFRP plates and concrete and at the same time improves the strength. For this test, there were only 14 test beams manufactured and failure load, deflection, strains and modes cf failure have been examined Test variables included the type cf strengthening, steel ratio and strengthening length, and the effects according to each test variables were analyzed. The experimental results show that the strength and stiffness cf the beam significantly increased between 34.55 and 116.51% and the increase cf the more lead-carrying capacity than the control beams.

• Steel and Composite Structures
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• 제23권4호
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• pp.385-397
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• 2017

Currently, CFRP (Carbon Fiber Reinforced Polymer) plate bonding is used quite extensively as a strengthening method. In this technique, a composite CFRP plate or sheet of relatively small thickness is bonded with an adhesion material to steel or concrete structure in order to improve its structural behavior and strength. The sheets or plates do not require much space and give a composite action between the adherents. In this study, the rotation capacity of CFRP-strengthened cold-formed steel (CFS) beams has been evaluated through numerical investigation. Studies on different structural levels have been performed. At the beam level, C-section has been adopted with different values of profile thickness, web height, and flange width. At the connection level, a web bolted moment resistant type of connection using through plate has been adopted. In web-bolted connections without CFRP strengthening, premature web buckling results in early loss of strength. Hence, CFRP sheets and plates with different mechanical properties and geometric configurations have been examined to delay web and flange buckling and to produce relatively high moment strength and rotation capacity. The numerical results reveal that CFRP strengthening may increase strength, initial stiffness, and rotation capacity when compared with the case without strengthening.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.187-190
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• 2005

Strengthening by bonded CFRP sheet/plate onto the surface has been generally used for the R.C. beams. The strengthening efficiency of this system depends on the performance of the adhesive interlace between the beam and the CFRP, and the interlace often causes unexpected failure. In this paper, an unbonding system is proposed with prestressed CFRP. Finite element analysis has been conducted using DIANA for the R.C. beams strengthened by prestressing the unbonded CFRP plate. The results of analysis were compared with those of experiment.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.812-815
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• 2002

This paper deals with the buckling and vibration analysis of plate with a hole. We knew that in this paper, as aspect ratio rises in design parameter, the buckling strength and the natural frequency of laminated composite plate decrease and as diameter of hole for width of plate rises, the buckling strength decrease but the natural frequency increase. Also this paper compared the CFRP laminated composit plate with the hybrid composite plate, and proposed that the hybrid composite plate is stronger than the CFRP composite plate.

• 대한토목학회논문집
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• 제28권4A호
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• pp.439-445
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• 2008

본 논문에서는 비부착 CFRP판으로 긴장 보강된 철근콘크리트 보를 해석하기 위한 수정된 부착감소계수를 제안하였다. 기존의 비부착 강연선의 극한응력 해석식에 대한 분석을 통해 비부착 CFRP판 긴장재로 보강된 철근콘크리트 보에 대한 적용성을 검토하였으며, 적용상의 문제점을 도출하였다. 합리적인 비부착 CFRP판 극한응력 해석식을 제안하기 위해 부착 CFRP판 긴장재의 평균변형률 개념으로부터 비부착 CFRP판 긴장재의 보강길이와 하중 재하 형태에 따른 순수휨구간 길이가 고려된 확장된 부착감소계수를 제안하였다. 최종 부착감소계수는 기존의 비부착 CFRP판 긴장 보강보에 대한 실험연구 문헌의 실험결과를 이용한 통계적 방법으로 결정되었으며, 제안된 부착감소계수를 포함한 극한응력 해석식에 의해 계산된 값을 실험결과와 비교하여 제안식의 유효성을 검토하였다.