• Steel and Composite Structures
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• 제50권4호
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• pp.475-487
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• 2024

The usage of fiber-reinforced polymer materials increases in the construction sector due to their advantages in terms of high mechanical strength, lightness, corrosion resistance, low density and high strength/density ratio, low maintenance and painting needs, and high workability. In this study, it is aimed to improve mechanical properties of GFRP box profiles, produced by pultrusion method, by filling the polymer concrete into them. Within the scope of study, hybrid use of polymer concrete produced with GFRP box profiles was investigated. Hybrid pressure and bending specimens were produced by filling polymer concrete (polyester resin manufactured with natural sand and stone chips) into GFRP box profiles having different cross-sections and dimensions. Behavior of the produced hybrid members was investigated under bending and compression tests. Hollow GFRP_xx profiles, polymer-filled hybrid members, and nominative polymeric concrete specimens were tested as well. The behavior of the specimens under pressure and bending tests, and their load bearing capacities, deformations and changes in toughness were observed. According to the test results; It was deduced that hybrid design has many advantages over its component materials as well as superior physical and mechanical properties.

• 한국안전학회지
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• 제23권5호
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• pp.97-104
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• 2008

This study was intended to evaluate the permeable performance through a change of reinforcing materials, curing condition, durability evaluation and permeability test, and to select the reinforcing material which could reduce the durability and water tightness from it, as the study for considering how the change of the outside's environment factors that the concrete structure actually contacted with impacted the concrete's durability especially the permeability by referring to such the background of the study. Accordingly, it was judged that evaluating the permeability by considering the severe environment condition where the concrete structure was placed in was more reasonable than measuring the existing permeability coefficient conducted in the sound state for the permeability evaluation of actually-used concrete structure. In this study, it also could be known that the specimen of hybrid fiber reinforced concrete which mixed the long and short steel fiber was the most effective for water tightness enhancement in severe environmental conditions.

• 콘크리트학회논문집
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• 제20권6호
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• pp.827-832
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• 2008

본 연구에서는 고강도콘크리트의 내화성능 향상을 위해 사용하고 있는 폴리프로필렌섬유와 강섬유 혼입에 따른 설계 강도 60 MPa급 고강도콘크리트 기둥의 내화특성을 평가하였다. 고강도 기둥 콘크리트 공시체의 내화특성 평가를 위하여 ISO-834 가열 곡선을 적용하여 내화실험을 실시하였다. 실험결과 섬유보강재를 혼입하지 않은 경우 폭렬이 심하게 발생하였으며 내부온도도 높게 나타났다. 폴리프로필렌 섬유를 혼입한 고강도콘크리트 기둥 부재의 경우 폭렬이 발생하지 않았으며 내부온도도 섬유보강재를 혼입하지 않은 경우보다 낮게 나타났으나 내부온도 증가에 있어서는 편차가 심해 내부온도 저하에는 큰 효과가 없는 것으로 나타났다. 폴리프로필렌섬유와 강섬유를 혼입한 기둥 공시체의 경우 폭렬이 발생하지 않았으며 가장 낮은 내부온도를 나타내 우수한 내화성능을 나타냈다.

• Structural Engineering and Mechanics
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• 제5권4호
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• pp.355-368
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• 1997

Fiber reinforced plastic (FRP) rods are used as reinforcement (prestressed or not) to concrete. FRP composites can also be combined with steel to form hybrid reinforcing rods that take advantage of the properties of both materials. In order to effectively utilize these rods, their bond behavior with concrete must be understood. The objective of this study is to characterize and model the bond behavior of hybrid FRP rods made with epoxy-impregnated aramid or poly-vinyl alcohol FRP skins directly braided onto a steel core. The model closely examines the split failure of the concrete by quantifying the relationship between slip of the rods resulting transverse stress field in concrete. The model is used to derive coefficients of friction for these rods and, from these, their development length requirements. More testing is needed to confirm this model, but in the interim, it may serve as a design aide, allowing intelligent decisions regarding concrete cover and development length. As such, this model has helped to explain and predict some experimental data from concentric pull-out tests of hybrid FRP rods.

• 한국구조물진단유지관리공학회 논문집
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• 제14권5호
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• pp.79-86
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• 2010

이 연구에서는 콘크리트 구조물의 섬유보강재인 하이브리드 섬유시트(HFC)와 하이브리드 섬유바(HFB)의 성능을 평가하였다. 실험결과에 의하면, 하이브리드 섬유보강재(시트, 바)로 보강된 보는 무보강보에 비해 약 60%~2배 이상의 높은 보강효과를 보였고 보강된 보는 항복점 이후 연성적인 거동을 보이며 파괴되는 이상적인 파괴모습을 보여주었다. 특히, 하이브리드 섬유바 보강의 경우 하이브리드 섬유바를 에폭시 주입과 접착제로 부착한 보강보는 비슷한 파괴거동을 보여줌으로써 부착방식에 따른 차이가 거의 없는 것으로 나타났다.

• 한국농공학회지
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• 제45권2호
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• pp.58-67
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• 2003

Over the last decade fiber-reinforced polymer (FRP) reinforcement consisting of glass, carbon, or aramid fibers embedded in a resin such as vinyl ester, epoxy, or polyester has emerged as one of the most promising and affordable solutions to the corrosion problems of steel reinforcement in structural concrete. But reinforcing rebar for concrete made of FRP rebar has linear elastic behavior up to tensile failure. For safety a certain plastic strain and an elongation greater than 3% at maximum load is usually required for steel reinforcement in concrete structures. The same should be required for FRP rebar. Thus, the main object of this study was to develop new type of hybrid FRP rebar Also, this study was evaluated to the mechanical properties of Hybrid FRP rebar. The Manufacture of the hybrid FRP rebar was achieved by pultrusion, and braiding and filament winding techniques. Tensile and interlaminar shear test results of Hybrid FRP rebar can provide its excellent tensile strength-strain behavior and interlaminar stress-strain behavior.

• 콘크리트학회논문집
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• 제28권2호
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• pp.213-221
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• 2016

이 연구에서는 강섬유 혼입률에 따른 초고성능 강섬유 보강 콘크리트(UHPC)의 압축거동에 관한 연구를 수행하였으며, 실험결과를 바탕으로 강섬유 보강 콘크리트의 압축강도와 탄성계수를 제안하였다. 지름 100 mm, 높이 200 mm의 원주형 공시체에는 0, 0.5, 1.0, 1.5, 그리고 2%의 강섬유가 혼입되었다. 실험에 사용된 UHPC는 굵은골재를 사용하지 않았으며, 16 mm와 19 mm의 강섬유가 일정비율로 혼입된 하이브리드 강섬유가 사용되었다. 실험결과, UHPC의 압축강도와 탄성계수는 강섬유 혼입률에 따라 증가하는 경향을 보였다. 실험결과를 바탕으로 강섬유 보강 콘크리트의 압축강도와 탄성계수가 제안되었다. 강섬유 보강 콘크리트의 압축강도는 무보강 콘크리트의 압축강도의 함수로 제안되었으며, 탄성계수는 강섬유 보강 콘크리트의 압축강도의 함수로 제안하였다. 기존 실험값과 비교한 결과 제안된 압축강도와 탄성계수는 실험값을 비교적 잘 예측하는 것으로 나타났으며, 압축강도가 35~235 MPa인 강섬유 보강 콘크리트에 적용가능 할 것으로 판단된다.

• Earthquakes and Structures
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• 제23권5호
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• pp.463-472
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• 2022

Reinforced concrete (RC) beam column joints (BCJ) have mostly exhibited poor seismic performance during several past earthquakes, typically due to the poor-quality concrete or lack of reinforcement detailing typical of pre-code design practice. The present study is motivated towards numerical simulation and seismic fragility assessment of one such RC-BCJ. The BCJ is loaded to failure and strengthened using Ultra High Performance-Hybrid Fiber Reinforced Concrete (UHP-HFRC) jacketing. The strengthening is performed for four different BCJ specimens, each representing an intermediate damage state before collapse. viz., slight, moderate, severe, and collapse. From the numerical simulation of all the BCJ specimens, an attempt is made to correlate different modelling and design parameters of the BC joint with respect to the damage states. In addition, seismic fragility analysis of the original as well as the retrofitted damaged BCJ specimens show the relative enhancement achieved in each case.

• Computers and Concrete
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• 제16권5호
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• pp.759-774
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• 2015

This study simulates the flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with steel and glass fiber-reinforced polymer (GFRP) rebars. For this, micromechanics-based modeling was first carried out on the basis of single fiber pullout models considering inclination angle. Two different tension-softening curves (TSCs) with the assumptions of 2-dimensional (2-D) and 3-dimensional (3-D) random fiber orientations were obtained from the micromechanics-based modeling, and linear elastic compressive and tensile models before the occurrence of cracks were obtained from the mechanical tests and rule of mixture. Finite element analysis incorporating smeared crack model was used due to the multiple cracking behaviors of structural UHPFRC beams, and the characteristic length of two times the element width (or two times the average crack spacing at the peak load) was suggested as a result of parametric study. Analytical results showed that the assumption of 2-D random fiber orientation is appropriate to a non-reinforced UHPFRC beam, whereas the assumption of 3-D random fiber orientation is suitable for UHPFRC beams reinforced with steel and GFRP rebars due to disorder of fiber alignment from the internal reinforcements. The micromechanics-based finite element analysis also well predicted the serviceability deflections of UHPFRC beams with GFRP rebars and hybrid reinforcements.

• Computers and Concrete
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• 제16권2호
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• pp.245-260
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• 2015

In this study, nominal moment-axial load interaction diagrams, moment-curvature relationships, and ductility of rectangular hybrid beam-column concrete sections are analyzed using the modified Hognestad concrete model. The hybrid columns are primarily reinforced with steel bars with additional Glass Fiber Reinforced Polymer (GFRP) control bars. Parameters investigated include amount, pattern, location, and material properties of concrete, steel, and GFRP. The study was implemented using a user defined comprehensive $MATLAB^{(R)}$ simulation model to find an efficient hybrid section design maximizing strength and ductility. Generating lower bond stresses than steel bars at the concrete interface, auxiliary GFRP bars minimize damage in the concrete core of beam-column sections. Their usage prevents excessive yielding of the core longitudinal bars during frequent moderate cyclic deformations, which leads to significant damage in the foundations of bridges or beam-column spliced sections where repair is difficult and expensive. Analytical results from this study shows that hybrid steel-GFRP composite concrete sections where GFRP is used as auxiliary bars show adequate ductility with a significant increase in strength. Results also compare different design parameters reaching a number of design recommendations for the proposed hybrid section.