• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.26-33
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• 2018

This paper presents experimental and analytical results on flexural behavior of flexural members made of SIFCON. Twelve SIFCON beams were subjected to bending tests and their flexural behavior was evaluated. Experimental variables included steel fiber type, presence of tensile reinforcement, and height of section. The specimens using Type-B steel fibers, which had better pullout resistance than Type-A steel fibers, showed flexural failure behavior without shear failure. The aspect ratio of steel fiber had a great influence on the behavior of SIFCON beams without tensile steel, however the effect on the behavior of SIFCON beams was negligible. In addition, the flexural strength equation for SIFCON was proposed in the study. The mean and standard deviation of the ratios of the predicted value to the experimental value are 1.02 and 0.04, respectively. Therefore, the proposed flexural strength equation can be useful for the design and performance evaluation of SIFCON beam.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.193-200
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• 2023

This paper investigates the effect of directional alignment of steel fibers using an electromagnetic field on the flexural fracture behavior of steel fiber reinforced concrete. A specially designed and manufactured solenoid, capable of aligning steel fibers in the longitudinal direction of the beam specimen, was employed for this purpose. Beam specimens with a design strength of 30 MPa were produced, and failure tests were conducted on specimens exposed to electromagnetic fields and those without exposure. Experimental variables included the mixing ratio and aspect ratio of steel fibers. The results of the experiments revealed a slight increase in flexural strength and crack mouth opening displacement at the maximum load for specimens exposed to the electromagnetic field. Notably, a significant enhancement in fracture energy was observed.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.257-267
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• 2008

Results of seventy-seven specimens tested by this study and previous research were collected and evaluated to propose the flexural strength and shear strength for flexural members with steel fiber concrete. For strength evaluation, structural parameters such as compressive strength, steel fiber content, tensile reinforcement ratio, and shear span to effective depth ratio are involved. The proposed equations for flexural and shear strength are regarded to give a good prediction for the strength of steel fiber reinforced composite and/or RC beams to compare with equations by previous researchers. Especially, the proposed shear strength equation in this study shows the lowest the mean value, the coefficient of variation and the error ratio among predictions by several equations. Therefore, equations for shear strength and flexure strength, which are proposed in this study are to be useful measure to predict the actual behavior and failure mode of steel fiber reinforced composite beams.

• Journal of the Korean Wood Science and Technology
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• v.37 no.4
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• pp.364-371
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• 2009

This study was carried out to investigate the bending strength of the Larix glulam beams which were reinforced with CFRP (Carbon fiber reinforced plastic) of which the reinforcement ratios were 0.7% and 2.1% by volume. In the bending test, the rupture shape of the reinforced glulam shows that the reinforced glulam broke firstly in the lowest bottom layer on which tension was loaded, but did not in the upper part reinforced with the CFRP layer. The upper part of the reinforced layer kept strength and did not break when the reinforced glulam broke firstly at the bottom part of the reinforced layer, but broke secondly as loading was increased. In the glulam beams reinforced with CFRP of which the reinforcement ratio was 0.7% by volume, the bending strength of the reinforced beams was increased by 28% at the first break. When beams broke up to the upper part of the reinforced layer, the bending strength of the reinforced beams was increased by 55%, compared to those of control glulam beams. When the glulam beams were reinforced with CFRP of which the reinforcement ratio was 2.1% by volume, the bending strength of the reinforced beams was increased by 77%, compared to those of control glulam beams. The ratio of the height of calculated neutral axis using failure mode recommended by Romani and the height of actual neutral axis using strain gauge was 1.03 and agreed well.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.207-216
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• 1997

본연구는 축방향 변형 구속이 고강도 콘크리트 휨부재의 휨 전단거동에 미치는 영향을 조사하기 위한 것으로, 수화열과 건조수축에 기인하는 축방향 변형과 재하에 의한 축방향 변형을 구속한 부재 및 무구속 부재에 대하여 휨파괴와 전단파괴 실험을 실시하였다. 타설 직후부터 축변형을 구속한 실험체의 재하시 강성은 재하전의 구속으로 발생한 관통균열의 영향을 받아 무구속 실험체의 강성보다 낮지만, 재하시의 축변형 구속에 따른 압축구속력의 상승으로 인하여 강성의 크기는 역전되었다 축변형이 완전히 구속된 휨부재의 휨강도는 무구속 부재보다 20%이상 상승하지만 변형능력은 감소하는 것으로 나타났으며, 재하전의 축변형 구속에 의한 관통균열(균열폭 0.1mm 미만)은 부재의 전단내력 및 전단균열 진전 형상에 영향을 미치지 않았다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.3
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• pp.19-27
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• 1991

In this paper, fracture tests were carried out in order to investigate the fracture behavior of SFRC (Steel Fiber Reinforced Concrete) structures. Thirty six SFRC beams were used in this test. The relationships between loadings, strains, and mid-span deflections of the beams were observed under the three point loading system. From the test results, the effects of percentage of fiber by volume, the fiber aspect ratio and the initial crack depth ratio on the concrete fracture behavior were studied, and the stress intensity factors, the thoughness index, and the flexural strength of SFRC beams were calculated. According to the regression technique, some empirical formulae for predicting the flexural strength of SFRC beams were also suggested.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.139-146
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• 2008

The characteristics of the biaxial flexural tensile strength of concretes was compared to that of the uniaxial strength. The uniaxial and biaxial strengths in this study were obtained from the classical modulus of rupture test and the biaxial flexural test recently developed by Zi and Oh and Zi et al., respectively. Three different sizes were considered to investigate the effect of the size of aggregates. To estimate the stochastic aspect of the strength, 32 specimens were used for each test. The average biaxial flexural fracture strength was about 20% greater than the uniaxial test. At the same time, the coefficient of variation for the biaxial test was 18% greater than the uniaxial test. This means that the probability of the biaxial cracking can be greater than the uniaxial cracking.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.169-176
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• 2011

In this study, the flexural test for reinforced high performance fiber reinforced cementitious composites (R/HPFRCC) members has been conducted in order to investigate the flexural behavior including the effect of an ordinary tensile reinforcing bar. Through the test, it was observed that the flexural strength increased due to the stable tensile stress transfer of HPFRCC, even up to the ultimate state. In addition, no localized crack appeared until the yielding of the reinforcement. From the layered section analysis of the tested members, it was found that the analysis with the tensile model obtained from the tension stiffening test showed better agreement with the flexural test results, whereas the analysis with direct tension test results overestimated the flexural capacity. Through the experimental and analytical studies, two flexural failure modes have been defined in this paper; concrete crushing at the top compression layer or tensile failure at the bottom tensile layer of the beam section. Based on these two flexural failure modes, a simple formula that estimates the ultimate flexural strength of the member has been proposed in this paper. The proposed equations can be useful in a design and an analysis of R/HPFRCC members.

• Magazine of the Korea Concrete Institute
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• v.6 no.1
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• pp.131-141
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• 1994

This experimental study was performed to lnvestigate the effects of the lergths dnd volume contents of glued hooked steel fiber for the fracture toughness and strength of c oncretc. The notched steel fiber reinforced concrete beams with different flber length(30, 60mm) and fiber volume content(O.0, 0.5, 1.0, 1.5, 2.0%) were tested under 3-point benclmg, md 1 he flexural strengths, fracture energy and CMOD were obtained from the experimental data. The fracture energy v~ds used as d means to evaluate the fracture toughness ot concrete. The results showed that the frdcture toughness and 5trength of conuett. were generally increased ds the content of steel fiber was inc~edsed, arid the length of steel ilber had a great efiect on the flexural strength but little on the compressive itrength and fractule toughness. And also, considering the distributions of steel fiber, workablity and the maxinium size of coarse dqgregates, the optimum content of steel fiber seemed to be about 1.0 '0, and when lts length uias longer the results were somewhat tavorable.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.323-326
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• 2009

콘크리트의 보강재로 높은 인장 강도와 비부식성, 비자기성, 비전기성 등의 장점을 갖는 FRP의 사용에 대한 연구가 활발히 진행되고 있다. 하지만 FRP가 갖는 낮은 탄성계수와 취성적 성질로 인해 기존 설계방법을 적용하기에는 문제가 있다. 본 연구에서는 보강비 변화에 따른 AFRP 보강 콘크리트 보의 구조 실험을 수행하여 FRP 보강근을 사용한 콘크리트 부재의 휨 성능 연구에 대한 기초적 자료를 제공하고자 하였다. 각 실험체의 결과 데이터를 비교 분석한 결과 균형보강비를 기준으로 저보강 실험체는 FRP의 파단에 의해 급격한 파괴양상을 보인 반면에, 과보강 실험체는 콘크리트가 압괴하는 파괴 징후를 보이며 파괴에 도달하였다. FRP 보강근을 사용한 보 부재의 설계에 균형보강 이상의 설계가 요구되며, 과보강의 경우 고강도 콘크리트의 사용이 요구되는 것으로 분석되었다.