• Smart Structures and Systems
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• 제17권4호
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• pp.593-610
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• 2016

In this study, an innovative and smart glass fiber-reinforced polymer (GFRP) hybrid bar was developed for stronger durability of concrete structures. As comparing with the conventional GFRP bar, the smart GFRP Hybrid bar can promise to enhance the modulus of elasticity so that it makes the cracking reduced than the case when the conventional GFRP bar is used. Besides, the GFRP Hybrid bar can effectively resist the corrosion of conventional steel bar by the GFRP outer surface on the steel bar. In order to verify the bond performance of the GFRP hybrid bar for structural reinforcement, uniaxial pull-out test was conducted. The variables were the bar diameter and the number of strands and pitch of the fiber ribs. Tensile tests showed a excellent increase in the modulus of elasticity, 152.1 GPa, as compared to that of the pure GFRP bar (50 GPa). The stress-strain curve was bi-linear, so that the ductile performance could be obtained. For the bond test, the entire GFRP hybrid bar test specimens failed in concrete splitting due to higher shear strength resulting in concrete crushing as a function of bar deformation. Investigation revealed that an increase in the number of strands of fiber ribs enhanced the bond strength, and the pitch guaranteed the bond strength of 19.1 mm diameter hybrid bar with 15.9 mm diameter of core section of deformed steel the ACI 440 1R-15 equation is regarded as more suitable for predicting the bond strength of GFRP hybrid bars, whereas the CSA S806-12 prediction is considered too conservative and is largely influenced by the bar diameter. For further study, various geometrical and material properties such as concrete cover, cross-sectional ratio, and surface treatment should be considered.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.327-330
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• 2005

In this study, the nature of brittleness, one of the main problems of GFRP(Glass Fiber Reinforced Plastic) Re-bar, is improved. Therefore, Hybrid GFRP Rod is developed by attaching FBG sensor to the new GFRP Rod with toughness, essential for flexural reinforcement of the concrete. The test was performed with specimens of Hybrid GFRP Rod. According to the test, data measured by electric gauge sensor are compared with data measured by FBG sensor.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.737-749
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• 2020

A hybrid bridge deck is proposed, which includes steel bars, concrete and glass-fiber-reinforced-polymer (GFRP) plates with channel sections. The steel bar in the negative moment region can increase the flexural stiffness, improve the ductility, and reduce the GFRP ratio. Three continuous decks with different steel bar ratios and a simply supported deck were fabricated and tested to study the mechanical performance. The failure mode, deflection, strain distribution, cracks and support reaction were tested and discussed. The steel bar improves the mechanical performance of continuous decks, and a theoretical method is proposed to predict the deformation and the shear capacity. The experimental results show that all specimens failed with shear failure in the positive moment region. The increase of steel bar ratio in the negative moment region can achieve an enhancement in the flexural stiffness and reduce the deflection without increasing GFRP. Moreover, the continuous deck can achieve a yield load, and the negative moment can be carried by GFRP plates after the steel bar yields. Finally, a nonlinear analytical method for the deflection calculation was proposed and verified, with considering the moment redistribution, non-cracked sections and nonlinearity of material. In addition, a simplified calculation method was proposed to predict the shear capacity of GFRP-concrete decks.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.199-205
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• 2001

This paper describes the design methodology, manufacturing process, rebar tensile and bending properties. Braidtrusion is a direct Composite fabrication technique utilizing an in-line braiding and pultrusion process. The produced Composite rebar exhibits ductile stress-strain behavior similar to that of conventional steel bar. Various rebar diameters ranging from modeling scale(3m) to full-scale prototype of 9.5mm have been produced Glass Fiber Reinforced Plastics(GFRP) rebar were successfully fabricated at $\phi$8.5mm and $\phi$9.5mm nominal diameters of soild and hollow type using a braidtrusion process. Tensile and bending specimens were tested and compared with behavior of stress-strain of GFRP rebar and steel bar.

• 한국해양공학회지
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• 제19권1호
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• pp.57-63
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• 2005

The objective of this research is to investigate the mechanical characteristics of the hybrid fiber reinforced composite rebar, which is manufactured from a braidtrusion process. Braidtrusion is a direct composite fabrication technique, utilizing in-line brading and the pultrusion process. hz order to obtain the mechanical behavior of the glass fiber, carbon fiber, and kevlar fiber, the tensile tests are carried out. The results of the fibers are compared with that of steel. Hybrid rebar specimens with various diameters, ranging from model size (3 mm) to full-scale size (9.5 mm), and various cross sections, such as solid and hollow shape, have been manufactured from the braidtrusion process. The tensile and bending tests for the case of the hybrid rebar, the conventional GFRP rebar, and the steel bar have been carried out. The results of the experiments show that the hybrid rebar is superior to the conventional GFRP rebar and the steel bar, from the viewpoint of tensile and bending characteristics.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.48-52
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• 2002

This paper describes the need for a ductile Fiber Reinforced Plastic(FRP) reinforcement for Concrete Structures. Using the material hybrid and geometric hybrid, it is demonstrated that the pseudo-ductility Characteristic can be generated in FRP rebar. Ductile hybrid FRP bars were successfully fabricated at Ø3mm and Ø10mm nominal diameters using the braidtrusion process. Tensile and bending specimens from these bars were tested and compared with behavior of stress-strain of steel bar and GFRP rebar

• Computers and Concrete
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• 제27권4호
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• pp.305-317
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• 2021

The bond between the concrete and bar is a main factor affecting the performance of the reinforced concrete (RC) members, and since the steel corrosion reduces the bond strength, studying the bond behavior of concrete and GFRP bars is quite necessary. In this research, a database including 112 concrete beam test specimens reinforced with spliced GFRP bars in the splitting failure mode has been collected and used to estimate the concrete-GFRP bar bond strength. This paper aims to accurately estimate the bond strength of spliced GFRP bars in concrete beams by applying three soft computing models including multivariate adaptive regression spline (MARS), Kriging, and M5 model tree. Since the selection of regularization parameters greatly affects the fitting of MARS, Kriging, and M5 models, the regularization parameters have been so optimized as to maximize the training data convergence coefficient. Three hybrid model coupling soft computing methods and genetic algorithm is proposed to automatically perform the trial and error process for finding appropriate modeling regularization parameters. Results have shown that proposed models have significantly increased the prediction accuracy compared to previous models. The proposed MARS, Kriging, and M5 models have improved the convergence coefficient by about 65, 63 and 49%, respectively, compared to the best previous model.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.13-16
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• 2008

철근으로 휨 보강된 일반적인 부재의 경우, 강도설계법으로 부재의 공칭 휨 강도를 계산할 때 모든 휨 인장 철근은 극한상태에서 항복한다고 가정한다. 따라서 인장력은 철근의 도심에 작용하고 인장 철근 단면적과 철근의 항복강도의 곱으로 표현될 수 있다. 그러나 FRP bar는 철근과 달리 항복거동을 보이지 않기 때문에 각 열 FRP bar에 작용하는 응력은 중립축에서 떨어진 거리에 따라 달라질 것이다. 게다가 서로 다른 종류의 FRP bar가 동시에 한 부재에 적용된다면, 각 FRP bar의 변형률에 따라 작용하는 응력 또한 다양하게 될 것이고, 거동 양상 역시 예상과 다르게 나타날 것이다. 이에 본 연구에서는 일반철근, CFRP bar, GFRP bar를 이용하여 하이브리드 휨 보강된 6개의 고강도 콘크리트 보를 제작하고 구조실험을 실시하였다. 실험 결과 하이브리드 보강된 부재는 FRP bar로 단순 보강된 부재의 낮은 강성, 큰 균열폭, 취성 문제를 상당히 보완시켜주는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제22권1호
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• pp.199-207
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• 2018

이형철근과 FRP 보강근의 복합 이중근을 갖는 FRC 보의 휨성능을 평가하기 위하여 실험이 수행되었다. 인장근의 종류(CFRP 보강근, GFRP 보강근, 철근)과 PVA 섬유 혼입률(0.5%, 0%)을 주요변수로 한 7개의 실험체를 제작하였다. 유한요소해석을 통하여 FRC 보의 균열 및 휨거동을 예측하기 위한 해석적 방법이 제안되고 분석되었다. 복합 이중근을 가지는 실험체들에서 철근으로 이중근을 가지는 실험체가 철근과 FRP 보강근을 이단으로 배치한 실험체들에 비하여 26~34% 균열하중이 큰 것으로 나타났다. 최대 휨강도에서는 복합 이중근을 가지는 실험체들 중 CFRP 보강근을 최외측으로 한 실험체가 가장 큰 내력을 나타내었다. 해석과 실험을 통한 휨강도를 비교한 결과, 강도비는 평균 1.2, 표준편차 0.085, 최대 오차율은 22% 등으로 나타났다. 이러한 결과에서 본 연구의 유한요소해석방법이 복합 이중근을 가지는 보의 실제 거동을 효과적으로 표현할 수 있음을 알 수 있다.

• 한국구조물진단유지관리공학회 논문집
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• 제12권3호
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• pp.93-100
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• 2008

혹독한 자연환경하에서의 구조물의 내구성이 주요한 관심사도 대두되면서 건설분야에서 섬유강화폴리머의 사용이 점차 증가하고 있는 추세이다. 본 연구에서는 FRP bar를 휨부재의 휨보강근으로서의 적용가능성을 평가하기 위하여 휨실험을 수행하였다. 탄소섬유, 유리섬유 및 탄소와 유리섬유를 혼합한 hybrid 섬유 보강근을 사용하여 보강량을 변화시킨 12개의 실험체를 제작하여 실험을 수행하였으며, 그결과는 파괴형태, 모멘트-변위, 휨강도, 연성지수 및 단면에서의 변형율분포 등에 대하여 분석하였다. 실험결과는 ACI 기준에 제시된 모델과 비교하였으며, 전체적으로 보의 휨강도는 강도설계이론에 의한 결과와 거의 유사한 것으로 나타났다. 그러나 처짐의 경우에는 유리섬유의 경우는 이론이 과대평가 되었으며, 탄소섬유는 과소평가되는 것으로 나타났다.