Concrete structure is a construction material with durability and cost-benefit, however the corrosion in embedded steel causes a critical problem in structural safety. This paper presents an evaluation of chloride resistance and pull-off performance with various corrosion level. For the work, OPC(Ordinary Portland Cement) concrete and GGBFS(Ground Granulated Blast Furnace Slag) concrete are prepared with normal steel. Artificially notch induced FRP Hybrid Bar is also prepared and embedded in OPC concrete and accelerated corrosion test is performed. Through the test, FRP Hybrid Bar with notch is evaluated to have insignificant effect on pull-off capacity when corroded steel shows only 21% level of pull-off capacity. Furthermore GGBFS concrete with normal steel shows over 70% level of pull-off capacity due to reduced corrosion currency.

In this study, the retrofit effect by fiber reinforced plastics (FRP) for the existing reinforced concrete (RC) moment frames is investigated. The FRP jacketing method is employed for retrofitting the flexural strength of columns and the FRP U-shaped wrapping method are utilized for retrofitting the shear strength of beams. The placements and amount of FRP retrofit are determined by the genetic algorithm based optimal seismic retrofit algorithm.

This paper presents the experimental results for reinforcement effect for FRP strengthened steel structures. Bond behavior, flexural, and compression were conducted. First, from bond test, it was able to examine the interfacial behavior and to evaluate the interfacial bond stress between AFRP plate and steel plates. Second, for flexural test, maximum load was increased with increasing FRP layer. Also, debonding failure was observed between steel plates and FRP plates. Third, for compression, for short columns it was observed that two sides would typically buckle outward and the other sides would buckle inward. Also, for long columns, overall buckling observed. The maximum load was increased up to 33% for slender section short columns. From the test, it was able to verify the reinforcement effect for FRP strengthened steel structures.

A standard design section of a FRP DSCT wind power tower supporting 3MW was suggested and designed through AutoDSCT and CoWiTA programs. The thicknesses of the FRP tubes were optimized and by using the parameters of designed tower, the performance of the new type wind tower was evaluated via FAST program.

RC(Reinforced Concrete) 부재는 인장영역에서 보강재가 하중을 지지해야 하므로, 철근부식은 내구성 뿐 아니라 안전성에서도 매 우 중요하다. 본 연구에서는 최근 개발된 FRP Hybrid Bar와 일반 철근을 매립한 RC 보부재를 제작하였으며, ICM(Impressed Current Method) 를 적용하여 철근부식을 촉진시켰다. 기존의 이론식인 Faraday 법칙을 이용하여 부식량을 평가하였으며, 일반설계강도를 가진 콘크리트 보부 재에 대하여 휨시험을 수행하였다. 일반 철근에서는 부식량이 4.9∼7.8% 수준으로 평가되었으며 이에 따른 휨 저항능력은 -25.4∼-50.8% 수준 으로 감소하였다. FRP Hybrid Bar를 매립한 RC 보에서는 부식과 휨 저항 감소가 평가되지 않았는데, 이는 에폭시 도료로 코팅된 철근의 우수 한 내부식성에 기인한다. 촉진 부식실험에서는 FRP Hybrid Bar의 우수한 내부식성 및 부착성능을 확인하였는데, 실용화를 위해서는 장기적인 침지를 통한 내구성 평가가 필요하다고 판단된다.

본 연구에서는 콘크리트에 표면매입된 FRP판의 부착거동에서, 전단키와 연단거리의 효과를 관찰하기 위한 부착시험을 실시하였 다. 실험에서의 주요변수는 전단키의 위치, 형태 그리고 연단길이이다. 규격 3.6 ㎜×16 ㎜의 FRP를 400 ㎜×200(300) ㎜×400 ㎜ 규격의 콘크리 트 블록에 매입하고 에폭시로 고정시켜서 실험변수에 따라 총 10개의 부착실험체를 제작하였다. FRP의 연단에 인장력을 가한 뒤 파괴시까지 실험을 실시하고 하중을 기록하였으며, 미끄러짐과 FRP의 인장변형량을 기록하였다. 실험으로부터, 전단키의 위치는 가력부에서 멀리 떨어 질수록 전단강도가 상승하는 것으로 나타났으며, 전단키의 직경이 커질수록 내력이 저하되는 것으로 나타났다. 특히 전단키가 일정 이상의 규 격이 되면 전단키가 없는 경우에 비하여 내력이 저하되어 오히려 부착강도에 부정적인 영향을 미칠 수 있는 것으로 나타났다. NSM FRP에서 응력장용방향의 연단거리가 길어짐에 따라 동일 부착길이임에도 불구하고 내력이 일부 증가하는 것으로 나타났다. 표면매입 보강된 FRP의 부착실험에서, FRP와 콘크리트사이의 부착-미끄러짐은 전체거동을 지배하는 것으로 나타나므로 이에 따른 과도한 미끄러짐은 설계에 반드시 고려될 필요가 있다.

Tensile performance of the recently developed “FRP Hybrid Bar” at Korea Institute of Civil Engineering and Building Technology (KICT) is experimentally evaluated by the authors. FRP Hybrid Bar is introduced to overcome the low elastic modulus of the existing GFRP bars to be used as a structural member in reinforced concrete structures. The concept of material hybridization is adapted to increase elastic modulus of GFRP bars by using steel. This hybridized GFRP bar can be used in concrete structures as a flexural member with a sufficient level of elastic modulus. In order to verify the effect of material hybridization on tensile properties, tensile tests are conducted. The results for both FRP Hybrid Bar and the existing GFRP bars are compared. The results indicate that the elastic modulus of FRP Hybrid Bar can be enhanced by up to approximately 250 percent by the material hybridization with a reasonable tensile strength. To ensure the long-term durability of FRP Hybrid Bar to corrosion resistance, the individual and combined effects of environmental conditions on the bar itself as well as on the interface between rebar and concrete are currently under investigation.

FRP에 대한 많은 연구가 진행상에 있으나 대부분 전단강화 효과에 중점을 두고 있다. 본 연구는 FRP RC 요소에 외부적으로 FRP Uwrap의 고정 효과에 중점을 두고 Uwrap의 거동에 영향을 주는 변수를 체계적으로 평가하였다.

During the last two decades, fiber reinforced polymer (FRP) reinforcing bars for concrete structure has been extensively investigated and a number of FRP bars are commercially available. However, major shortcomings of the existing FRP bars are its high initial cost and low elastic modulus compared to conventional steel bars. Because of these reasons, KICT in Korea have developed the FRP Hybrid Bar which have the concept of material hybridization for concrete structures, especially for marine and waterfront concrete structures. In this study, for the discussing the applicability of FRP Hybrid Bar to real concrete structures, life cycle cost analysis were performed on small bridge and discussed considering various kinds of maintenance cases.

최근 들어 FRP 판을 영구 거푸집 및 주요 인장보강재로 활용하기 위한 새로운 콘크리트 교량 바닥판 시스템 개발에 대한 연구가 활발히 진행되고 있다. 영구거푸집과 인장 보강재로의 병행이용은 기존의 콘크리트 바닥판 보다 공사비와 공사기간을 절감 할 수 있다. 본연구에서 는 영구거푸집 및 주요인장재로 활용한 FRP 판의 종류에 따른 현장타설 콘크리트와 부착응력에 대해 실험을 수행하였다. 부착성능 평가를 실시하였고, 부착특성을 나타내는 중요한 변수중에 하나로서 부착 강도 및 부착면의 파괴 매커니즘 특성을 알 수 있는 계면 파괴에너지를 나타내었다. 일반콘크리트에서 계면 파괴에너지는 GF11의 경우 0.24kN/m이고, GF21의 경우에는 0.43kN/m, GF31과 CF11의 경우에는 각각 0.46kN/m와 0.44kN/m로 나타났고, RFCON에서는 GF12의 경우 0.52kN/m, GF22와 CF12에서는 각각 0.36kN/m와 0.51kN/m로 나타났다.

In the paper, newly invented FRP Hybrid Bar and normal steel are embedded in RC beam member, and ICM(Impressed Current Method) is adopted for corrosion acceleration. Corrosion amount level of 4.9∼7.8% are measured in normal RC member and the related reduction of flexural capacity is measured to –25.4∼-50.8%. But, durability evaluation through long-term submerged condition is required for actual utilization.

In the paper, accelerated corrosion test for RC (Reinforced Concrete) samples with normal steel and FRP Hybrid Bar are performed and their flexural capacity is evaluated. Furthermore UV(Ultrasonic Velocity) measurement is attempted for analysis of variation of UV due to corrosion conditions. For commercial production of FRP Hybrid Bar, bond strength evaluation through long-term submerged corrosion test is required.

This study presents an experimental study on compressive and flexural strengths of concrete reinforced by 3D Fiber Reinforced Polymer(FRP). This study is intended to investigate the potential of 3D FRP concrete composites against impact or explosive loadings. For the comparative study, non-reinforced specimen and specimens reinforced by 3D FRP are constructed and tested. 20mm×10mm 3D fiber and 25mm×20mm 3D fiber was set to be variable.

This study is to determine the flexural reinforcement performance of the RC beam through the NSM reinforcement experiment. To do this, to produce non-reinforced specimen and reinforced specimens were performed the experimental study. As the results of this study, the tension reinforcing steel has been confirmed between the FRP bar and filled material integrated behavior before yielding. Compared with non-reinforced specimen the reinforced specimens showed that the rigidity of the reinforced specimens is higher than that of the non-reinforced specimen about 16.7%, and increases 8.3%~20.0% and 33.3%~52.7% for yielding strength and ultimate strength respectively. It appears an excellent bending reinforcing effect.

본 연구에서는 FRP로 보강된 장방형 철근콘크리트 기둥의 구속효과에 미치는 형상계수의 영향력 평가를 수행하였다. Lam and Teng의 연구결과를 바탕으로, FRP 종류를 구분하고, 단면형태에 따라 총 150여개의 철근콘크리트 기둥 실험 데이터를 분석하였다. 분석 결과, 단면의 형상계수가 구속효과에 가장 큰 영향을 미치는 것으로 나타났으며, FRP로 보강된 장방형 철근콘크리트 기둥은 보강되지 않은 철근콘크리트기둥에 비하여 구속효과가 28%에서 67%까지 증가되는 결과를 나타냈다. 또한, 정방형 형태는 장방형 형태에 비하여 약 20% 정도 증가되는 구속효과가 나타남을 확인할 수 있었다. 현재 FRP 보강에 대한 구속효과 산정식은 매우 복잡한 형태를 보이고 있으며, 실무에 적용하기 어려운 실정이다. 이에 본 연구에서는 분석한 결과를 이용하여, 간단한 구속효과 산정식을 제안하였다.

이 연구는 철근 부식 문제의 해결 방안으로 떠오르고 있는 섬유복합체(Fiber Reinforced Polymer, FRP) 보강근에 대해 인장강도 추정식인 혼합법칙을 보정하여 FRP 보강근의 인장강도를 좀더 정확히 예측할 수 있는 방법론을 제안하는데 그 목적을 두었다.

This paper evaluates the shear strength, behavior and failure mode of reinforced concrete beams with deformed GFRP reinforcing bar. Four concrete beam specimens were constructed and tested. It was carried out to observe failure behavior and load-deflection of simply supported concrete beams subjected to four-point monotonic loading. Load-deflection for FRP reinforced concrete beam member were predicted.

This paper deals with the recent development of GFRP bars by material hybridization (i.e., “hybrid GFRP bars”). This development attempts to improve the low elastic modulus of GFRP bars to be used for reinforced concrete (RC) structures, especially they were built in a corrosive environment (e.g., waterfront structures). The purpose of material hybridization in this study is to increase the elastic modulus of GFRP bar. Steel wires were inserted to GFRP and dispersed over the cross-section. E-glass fibers and unsaturated polyester resins were pultruded. Several types of the hybrid GFRP bars were tested to evaluate the tensile strength. Mechanical behaviour of hybrid GFRP bars was examined as a function two factors: 1) a ratio of steel to GFRP; 2) a diameter of steel wire. The experimental results showed that the elastic modulus of the hybrid GFRP bar was improved by up to 171% by material hybridization. To ensure the long-term durability of the hybrid GFRP bars in waterfront structure applications, the individual and combined effects of environmental conditions on the hybrid GFRP bar itself as well as on the interface between bar and concrete should be also accessed.

In this study it was developed FRP rod embedding FBG sensor, and compared the performance of sensor of the new rods and the existing strain gauge by applying the reinforced concrete beam-column joint in the same location. And it was found that new FRP rod was improved the structural performance and sufficiently sensing accuracy.

In this study, experimental research was carried out to evaluate the structural performance of the reinforced concrete beam retrofitted by strengthening methods(embedded CFRP rod of hexagon, CFRP Sheet) in existing reinforced concrete buildings. Test results showed that the maximum load carrying capacity of retrofitted specimens(NER2, NER2-C) were increased by 1.46 ~ 1.67 times respectively in comparison with the standard specimen(NBS).