• 한국구조물진단유지관리공학회 논문집
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• 제11권1호
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• pp.181-192
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• 2007

본 연구의 목적은 CFRP판을 다양한 방법으로 보강한 RC보의 휨거동을 실험적으로 비교 분석하고, 프리스트레싱 보강공법의 실용화를 목적으로 프리스트레싱 보강 RC부재의 휨성능 평가식을 제안하는 것이다. 실험변수로는 CFRP판의 보강방법, 콘크리트 압축강도, 인장철근비 그리고 프리스트레싱 수준 등을 고려하였다. 실험결과 프리스트레싱이 도입되지 않은 실험체는 조기 부착파괴로 인해 탄소판이 콘크리트로부터 탈락하면서 파괴된 반면, 프리스트레싱을 가한 대부분의 실험체는 CFRP판의 파단으로 파괴되었다. 프리스트레싱 보강된 부재의 휨강도를 예측할 수 있는 식을 제안하였으며, 실험결과와의 비교를 통하여 제안식은 휨강도 예측에 있어 충분한 정확도를 확보하고 있음을 확인하였다.

• Steel and Composite Structures
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• 제20권6호
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• pp.1275-1303
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• 2016

Steel plates and carbon-fiber-reinforced polymer (CFRP) laminates or plates bonded to concrete substrates have been widely used for concrete strengthening. However, this technique cause plate debonding, which makes the strengthening system inefficient. The main objective of this study is to enhance the bond strength of externally bonded steel plates and CFRP laminates to the concrete surface by proposing new embedded adhesive and steel connectors. The effects of these new embedded connectors were investigated through the tests on 36 prism specimens. Parameters such as interfacial shear stress, fracture energy and the maximum strains in plates were also determined in this study and compared with the maximum value of debonding stresses using a relevant failure criterion by means of pullout test. The study indicates that the interfacial bond strength between the externally bonded plates and concrete can be increased remarkably by using these connectors. The investigation verifies that steel connectors increase the shear bond strength by 48% compared to 38% for the adhesive connectors. Thus, steel connectors are more effective than adhesive connectors in increasing shear bond strength. Results also show that the use of double connectors significantly increases interfacial shear stress and decrease debonding failure. Finally, a new proposed formula is modified to predict the maximum bond strength of steel plates and CFRP laminates adhesively glued to concrete in the presence of the embedded connectors.

• 한국안전학회지
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• 제27권1호
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• pp.55-62
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• 2012

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the flexural fracture test with various experimental variables including the number, the angle and the combination of FRP laminates. From the aluminum-FRP composite tests no great increase in flexural strength and flexural toughness were observed. However, flexural toughness of steel-FRP laminate composite was increased so that its behavior can be considered in the retrofit design. In addition, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions.

• 한국안전학회지
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• 제26권6호
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• pp.54-63
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• 2011

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the tensile test with various experimental variables including the number, the angle and the combination of FRP laminates. From the test results, both aluminum and steel-FRP laminate composite material showed increased fracture toughness. However, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions. In general, steel-FRP laminate composite showed better tensile performance in regards to the seismic retrofit purposes.

• Advances in Computational Design
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• 제7권3호
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• pp.173-188
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• 2022

In modern buildings, glass is considered a structurally unsafe material due to its brittleness and unpredictable failure behavior. The possible use of structural glass elements (i.e., floors, beams and columns) is generally prevented by its poor tensile strength and a frequent occurrence of brittle failures. In this study an innovative modelling based on an equivalent thickness concept of laminated glass beam reinforced with FRP (Fiber Reinforced Polymer) composite material and of glass plates punched is presented. In particular, the novel numerical modelling applied to an embedding Carbon FRP-rod in the interlayer of a laminated structural glass beam is considered in order to increase both its failure strength, together with its post-failure strength and ductility. The proposed equivalent modelling of different specimens enables us to carefully evaluate the effects of this reinforcement. Both the responses of the reinforced beam and un-reinforced one are evaluated, and the corresponding results are compared and discussed. A novel equivalent modelling for reinforced glass beams using FRP composites is presented for FEM analyses in modern material components and proved estimations of the expected performance are provided. Moreover, the new suggested numerical analysis is also applied to laminated glass plates with wide holes at both ends for the technological reasons necessary to connect a glass beam to a structure. Obtained results are compared with an integer specimen. Experimental considerations are reported.

• 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.

• 한국철도학회논문집
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• 제12권5호
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• pp.641-648
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• 2009

최근 철도차량의 속도가 증가함에 따라 철도시설물에도 철근콘크리트 구조물이 많이 적용되고 있는 실정이다. 하지만 이러한 콘크리트 구조물은 공용년수의 증가에 따라 필연적으로 구조적인 보강이 요구된다. 강판보강법 및 섬유복합체(FRP)를 활용한 보강법 등이 가장 일반적으로 적용되는 실정이지만 각 공법마다 나름대로의 단점 역시 존재 한다. 최근 화재나 기타 환경적인 공격에 대하여 강한 내구성을 가진 재료의 개발이 요구되고 있으며 이에 따른 현무암으로부터 추출한 Basalt 섬유를 활용한 섬유보강재가 많은 관심을 받고 있다. 이에 본 연구에서는 Basalt 섬유쉬트를 보강재로 사용할 경우 중요한 특성인 콘크리트와의 부착특성에 관하여 연구를 수행하였다. 실험변수는 보강폭, 길이, 보강겹수를 포함한다. 실험결과, 파괴형태는 계면파괴, 섬유파단, 그리고 rip-off의 형태가 관측되었으며 보강길이보다는 보강폭이 보강강도에 더 많은 영향을 미치는 것으로 판단되었다. 또한 보강길이가 전부 유효하게 작용하지는 않았으며 이에 유효보강길이를 산정하고 이에 따른 부착강도를 산정하였다. 이를 다른 종류의 FRP재료를 활용한 경우에 유효 보강길이와 비교하여 Basalt 섬유쉬트의 부착특성을 분석하였다.

• 항공우주시스템공학회지
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• 제12권6호
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• pp.32-40
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• 2018

본 연구에서는 error-outlier 기반의 충격위치탐지 알고리즘과 다중화된 FBG 센서를 이용하여 탄소섬유 강화 플라스틱 복합재 평판 구조물에 대한 충격위치탐지를 수행하였다. 알고리즘의 주요 변수인 오차 임계값(ET)이 0.3 nm, 상수 수준(CL)이 110일 때 최적의 충격위치탐지 결과(최대 오차= 31.82 mm, 평균 오차= 6.31 mm)가 도출되었다. 또한 주어진 최적의 변수 조건에서의 충격위치탐지 과정과 결과를 상세히 분석하였다. 본 연구에서 제시된 다중화된 FBG 센서와 error-outlier 기반의 충격탐지 알고리즘은 복합재 구조물에 대한 충격탐지에 적합한 것으로 판단되며, 향후 다양한 구조 건전성 감시에 활용될 것으로 기대된다.

• 국제강구조저널
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• 제18권4호
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• pp.1284-1296
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• 2018

Carbon fiber reinforced polymer (CFRP), plates bonding repair method is one of the simple repair methods for cracked steel structures. In this study, the influence of width of CFRP plates on bending fatigue life of out-of-plane gusset joint strengthened with CFRP plates was investigated from the experimental and numerical point of view. In the bending fatigue test of cracked out-of-plane gusset joint strengthened with CFRP plates, the effect of width of CFRP plates on crack growth life was clarified experimentally. Namely, it was revealed that the crack growth life becomes larger with increasing the width of CFRP plates. In the numerical approach, the stress intensity factor (SIF) at the surface point of a semi-elliptical surface crack was estimated based on the linear fracture mechanics. Furthermore, the extended fatigue life of cracked out-of-plane gusset joint strengthened with CFRP plates was evaluated by using the estimated SIF at the surface point and the empirical formula of the aspect ratio of semi-elliptical crack. As the results of numerical analysis, the estimated fatigue life of the specimen strengthened with CFRP plates showed the good agreement with the test results.

• 한국구조물진단유지관리공학회 논문집
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• 제23권1호
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• pp.171-178
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• 2019

본 연구는 탄소섬유시트, 아라미드섬유시트, 그리고 유리섬유시트를 혼합한 하이브리드 FRP 플레이트를 제작하였으며, 제작한 보강 플레이트를 보강한 후, 최대한의 휨 보강 효과가 발생되도록 다시 보강 플레이를 긴장시켜 RC보의 휨 보강 효과를 파악하고자 하였다. 또한, 긴장시키는 보강방법을 제시하는 동시에 무보강 실험체에 비해 보강효과가 어느 정도 되는지 실험적으로 규명하기 위해 실험적 연구를 진행하였다. 연구를 위해 총 8개의 RC 보 부재를 동일하게 제작하여 1 개의 실험체(N 실험체)를 제외한 7 개의 실험체는 보강재 종류, 단부 정착 앵커 개수, 보강재 두께 등을 주요 변수로 하여 실험을 실시하였다. 실험결과, 휨 거동을 보이는 실험체에 긴장을 가한 FRP 플레이트로 보강하면, 보강하지 않은 실험체에 비해 우수한 휨거동(초기강도, 항복시 강도 및 강성, 최대강도 등)보여 주었으며, 단부정착 앵커의 개수가 많고, 보강재의 두께(보강량)가 클수록 보강효과가 우수한 것으로 나타났으며, 긴장시킨 보강재는 단일 FRP 플레이트에 비해, 하이브리드 FRP 플레이트를 적용했을 때 보강효과가 더 우수하게 나타났다.