• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.253-256
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• 2008

Although researches on the beams strengthened with Fiber reinforced Polymers (FRPs) have recently been conducted around the world, there are few researches on the beams with FRPs under a sustained load. This paper presents the behavior of the beams with Carbon Fiber Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) under a sustained load during 300 days. Strains of steel and FRP reinforcement were measured in order to investigate the behavior of the beams. Additionally, Adjusted Effective Modulus Method (AEMM) and Ghali and Farve's method were used to predict increase in the stress and strain caused by creep and shrinkage. Through the experiment, it was found that the beam with CFRP is more effective than the beam with GFRP in terms of flexural strengthening. Compared with analytical results, it was indicated that strains of tension steels were overestimated, whereas strains of compression steels were underestimated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.697-703
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• 2017

This paper examines the flexure behavior of FRP-concrete composite structure that can replace conventional reinforced concrete structure types. In order to investigate the structural performance and behavioral characteristics in numerical analysis means, ABAQUS, a general purpose finite element analysis program, was utilized for nonlinear finite element analysis, and the various variables and their influences were analyzed and compared with experimental results to suggest values optimized to this composite structure. The concrete damage plasticity model and Euro code for concrete were used. In the implicit finite element analysis, the convergence was ambiguous when geometrical and material nonlinearity were large, so the explicit finite element analysis used in this study was deemed to be appropriate. From the comparison with the experiment about concrete damaged plasticity model, 20mm for the mesh size, $30^{\circ}$ for the dilation angle, $100Nmm/mm^2$ for the value of fracture energy, 0.667 for Kc value, and the consideration of damage parameter were suggested believed to be appropriate. The numerical model suggested in this study was able to imitate the ultimate load and cracking pattern very well; therefore, it is expected to be utilized in research of various new material composite structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.209-212
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• 2009

최근 국내에서 적용되고 있는 콘크리트 충진 FRP 스트럿은 시공성 및 경제성 면에서 매우 뛰어난 공법으로 주목 받고 있으나 그 설계 및 시공에 있어 아직도 불확실한 요소를 내포하고 있다. 특히 최근에는 PSC 박스 거더교에서 교폭을 늘리고 자중을 줄이기 위해 콘크리트 충진 FRP 스트럿을 설치하는 공법이 다수 시공되고 있다. 본 연구에서는 이러한 대상교량에 대해 현장시험을 실시하여 교량시스템에서의 콘크리트 충진 FRP 스트럿 거동을 분석하는데 목적이 있다. 특히 전자기파 간섭에 면역이 우수한 광센서인 FBG 센서를 기반으로 하는 계측을 실시하여 잡음이 없는 우수한 결과를 성공적으로 획득하였다. 그 결과 FRP 스트럿은 하중 재하 위치와 속도에 관계없이 압축응력 상태에 존재하고 있으며 횡방향 거동에 지배되고 있음을 확인하였다.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.543-555
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• 2018

Fiber Reinforced Polymer (FRP), which has a high strength to weight ratio, are now regularly used for strengthening of deficient reinforced concrete (RC) structures. While various researches have been conducted on FRP strengthening, an area that still requires attention is predicting the debonding failure load of prestressed FRP strengthened RC beams. Application of prestressing increases the capacity and reduces the premature failure of the beams largely, though not entirely. Few analytical methods are available to predict the failure loads under flexure failure. With this paucity, this research proposes a method for predicting debonding failure induced by intermediate crack (IC) for prestressed FRP-strengthened beams. The method consists of a numerical study on beams retrofitted with prestressed FRP in the tension side of the beam. The method applies modified Branson moment-curvature analysis together with the global energy balance approach in combination with fracture mechanics criteria to predict failure load for complicated IC-induced failure. The numerically simulated results were compared with published experimental data and the average of theoretical to experimental debonding failure load is found to be 0.93 with a standard deviation of 0.09.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.1
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• pp.47-54
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• 2007

Bridge decks are one of the main structural components that are most suitable for utilizing the advantages of FRP materials due to the high strength weight ratio of FRP materials. Design codes for the design of FRP bridge decks should be established to apply FRP materials for bridge decks effectively. At present, design codes are relatively well established for the use of FRP materials as reinforcements in concrete structures. However, design codes have not yet been provided for the structures made of FRP as a main construction material. In this study, for the purpose of preparing design code provisions, reliability analyses were performed to evaluate target level of safety and serviceability on GFRP decks. Based on the results, several guidelines for the development of design codes are suggested.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.85-94
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• 2016

In this study, the hydrophilic chemical grout using silanol (HCGS) was introduced to overcome the limitations of conventional epoxy resin which have been used for strengthening reinforced concrete (RC) structures. Then, flexural tests on the RC slabs strengthened by FRP sheets were conducted. Three slab specimens were tested in this study; a control specimen with no strengthening, and two specimens strengthened by a typical epoxy resin or HCGS, respectively, as a binder between the slabs and the FRP sheets. In addition, an analytical model was developed to evaluate the flexural behavior of strengthened slab members, considering the horizontal shear force at the interface between concrete slabs and FRP sheets. The analysis results obtained from the proposed model indicated that the strengthened specimens showed fully composite behavior before their flexural failure. Especially, the specimen strengthened by HCGS, which can overcome the limitations of conventional epoxy resin, showed a similar flexural performance with that strengthened by a conventional epoxy resin.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.53-58
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• 2017

FRP Hybrid Bar, composed of an embedded steel and the coated composites with epoxy and glass fiber, is an effective construction material with tension-hardening performance and lightweight. The epoxy exposed to UV(Ultra Violet Rays) and FT(Freezing and Thawing) action easily shows a surface deterioration, which can cause degradation of bonding strength between inside-steel and outside-concrete. In the present work, surface inspection for 3 different samples of normal steel, FRP Hybrid Bar before UV, and FRP Hybrid Bar after UV test was performed, then concrete samples with 3 reinforcement types were prepared for accelerated FT test. Through visual inspection on 3 typed reinforcement, no significant deterioration like chalking was evaluated. The results from FT test to 120 and 180 cycles showed FRP Hybrid Bar exposed to UV test has higher bonding strength than normal steel by 106.3% due to enlarged bond area by silica coating. The 3 cases showed a similar bond strength tendency with increasing FT cycles, however a relatively big deviations of bond strength were evaluated in FRP Hybrid Bar after UV test due to loss of silica coating.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.151-157
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• 2008

It is difficult for existing beams to ensure the sufficient embedding depth due to constructional cause. Owing to these problems, currently FRP-Rod embedding repair method run parallel with a section increasing method in many case. In this study, anchor pin was adopted to solving the problems of the sliding of FRP-Rod and the unified behaviors of the repaired beam without increasing the section. In the experiments, split failure of covering concrete and slippage of the FRP-Rod were not occurred. it was confirmed that FRP-Rod shown the integrate behaviors with RC beam till the repaired beams destroyed.

• Earthquakes and Structures
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• v.8 no.5
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• pp.1171-1190
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• 2015

Enhancement of strength and ductility is the main reason for the extensive use of FRP jackets to provide external confinement to reinforced concrete columns especially in seismic areas. Therefore, numerous researches have been carried out in order to provide a better description of the behavior of FRP-confined concrete for practical design purposes. This study presents a new approach to obtain strength enhancement of CFRP (carbon fiber reinforced polymer) confined concrete cylinders by applying artificial neural networks (ANNs). The proposed ANN model is based on experimental results collected from literature. It represents the ultimate strength of concrete cylinders after CFRP confinement which is also given in explicit form in terms of geometrical and mechanical parameters. The accuracy of the proposed ANN model is quite satisfactory when compared to experimental results. Moreover, the results of the proposed ANN model are compared with five important theoretical models proposed by researchers so far and considered to be in good agreement.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.103-114
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• 2000

Recently, the need for strengthening reinforced concrete and prestressed concrete structure is increasing, particularly when there is an increase in load requirements, a change in use, a degradation problem, or some design/construction defects. Therefore, use of composite materials for structural repair presents several advantages and has been investigated all over the world. In this paper, the reinforced concrete slabs with epoxy - bonded AFRP sheed were experimentally investigated. Experimental data on strength. stiffness, material strain, deflection and mode of failure of strengthened slabs were obtained, and comparisons between the different flexural reinforcing schemes and reinforced concrete slabs without AFRP sheets were made It can be concluded that flexural strength of RC slabs strengthened with AFRP has increased, and that ductility of strengthened slabs has decreased.