• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.95-106
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• 1992

This paper presents a comparative evaluation of five different types of steel fibers used as reinforcing material in concrete beams. Two types of plain and RC beams were prepared to compare the relative flexural behavior. The fibers used were dog bone (paddled), both ends hooked. コ-type straight. crimped and wavy type with aspect ratio of 43 to 75. Fiber volume fraction of 1 to 2% were used while shear span to depth ratio (aid) and steel ratio p were fixed. Fiber reinforcement effect index Ef and effective toughness index Te were adopted to evaluate fiber reinforcing effects. The effect of fiber reinforcement on flexural strength is higher in plain beams than in RC beams. Hooked and dog bone type fibers were found to be more effective than the other type ones in enhancing the flexural strength and post-peak energy absorption capacity of concrete beams.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.361-370
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• 2006

The results of previous tests by many researchers have been compiled to evaluate the flexural strength of steel-fiber reinforced concrete beams. Existing prediction equations for flexural strength of such beams were examined, and a new equation based on mechanical and empirical observations, was proposed. In other words, the constitutive models for steel fiber reinforced concrete(SFRC) were proposed, which incorporate compressive and tensile strength. A steel model might also exhibit stain-hardening characteristics. Predictions based on the model are compared with the experimental data. For the collection of tests, a variation of the Henager equations, modified to apply to fiber-reinforced concrete beams, provided reliable estimates of flexural strength. The proposed equations accounted for the influence of fiber-volume fraction, fiber aspect ratio, concrete compressive strength and flexural steel reinforcement ratio. The proposed equations gave a good estimation for 129 flexural specimens evaluated.

• Journal of Technologic Dentistry
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• v.31 no.4
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• pp.37-43
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• 2009

This study evaluated the effect of concentration of glass fiber reinforcement on the flexural properties of auto and heat polymerized denture base resin. The test specimens($64{\times}10{\times}3.3mm$) were made of auto and heat polymerized resin(Vertex, Dentimax, Netherlands). Glass fiber(ER 270FW, Hankuk Fiber Glass, Korea) were used to reinforce the denture base resin. The 2.6%, 5.3% and 7.9% volume pre-impregnated fiber were located at the bottom of specimen. The test specimens(n=7) of each group were stored in distilled water at $37^{\circ}C$ for 50 hours before test. The flexural strength and modulus were measured by an universal testing machine(Z020, Zwick, Germany) at a crosshead speed of 5 mm/min in a three-point bending mode. The data was analyzed by one-way ANOVA and the Duncan's multiple range test(${\alpha}$=0.05). The difference of auto polymerized resin groups and heat polymerized resin groups were statistically analyzed by t-test(${\alpha}$=0.05). Glass fiber showed significant reinforcing effects on auto and heat polymerized resin. For flexural strength and modulus, auto polymerized resin was the highest in 7.9% volume, while heat polymerized resin was the highest in 5.3% volume. In this study, glass fiber at 7.9% volume ratio showed most effective reinforcing effect on auto polymerized resin and glass fiber at 5.3% volume ratio showed most effective reinforcing effect on heat polymerized resin in terms of flexural strength and flexural modulus.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.57-61
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• 2010

In this study, many concrete specimens were tested to investigate the variations of strength characteristics of high-strength concrete due to amount of recycled coarse aggregates, and to investigate the effect of steel-fiber reinforcement on concrete using recycled coarse aggregates. Test results showed that all of the variations of compressive, tensile and flexural strength appeared in linear reduction according to icrease the amount of recycled coarse aggregates, and steel-fiber reinforcement of 0.75% volumn of concrete recovered completely spliting tensile strength and flexual strength and recovered greatly compressive strength of concrete using recycled coarse aggregates of 100% displacement. And test results showed that the shear strength falled rapidly at 30% of replacement ratio so far as 34% of strength reduction ratio, but after that it falled a little within 3% up to the replacement ratio 100%, and steel-fiber reinforcement of 0.75% of concrete volumn recovered completely the deteriorated shear strength, moreover improved the shear strength above 50% rather than that of concrete using natural coarse aggregates.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.861-866
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• 2000

This experimental were investigated on the influence of steel fiber reinforcement on flexural behavior characteristics of slabs with various steel fiber contents $V_f$ and aspect ratio($\ell $/$\phi$). Deflection, crack widths, and strains of steel bar were measured with every load step. In the results of this experimental, the addition of steel fibers to conventionally reinforced concrete slab increased the ultimate load, reduced the creak width, the average crack spacing, and deflection.

• Computers and Concrete
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• v.12 no.4
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• pp.537-552
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• 2013

Computation of flexural ductility of reinforced concrete beam sections has been proposed by taking into account strain rate sensitive constitutive behavior of concrete and steel, confinement of core concrete and degradation of cover concrete during load reversal under earthquake loading. The estimate of flexural ductility of reinforced concrete rectangular sections has been made for a wide range of tension and compression steel ratios for confined and unconfined concrete at a strain rate varying from $3.3{\times}10^{-5}$ to 1.0/sec encountered during normal and earthquake loading. The parametric studies indicated that flexural ductility factor decreases at increasing strain rates. Percentage decrease is more for a richer mix concrete with the similar reinforcement. The confinement effect has marked influence on flexural ductility and increase in ductility is more than twice for confined concrete (0.6 percent volumetric ratio of transverse steel) compared to unconfined concrete. The provisions in various codes for achieving ductility in moment resisting frames have been discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.336-341
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• 1998

Steel fiber reinforced concrete(SFRC) is a composite material possessing many physical and mechanical properties which are distinct from unreinforced concrete. The use of steel fiber reinforcement to improve the flexural and tensile strengths, extensibility and toughness of ordinary cement concrete is well known at present, but reinforcement of polymer concrete with steel fibers has been hardly reported untill now. The objective of this study was to improve the properties of the polymer concrete by addition of steel fibers. In this paper steel fiber reinforced polymer concrete is prepared with various steel fiber contents and aspect ratio($\ell$ /d), and their mechanical properties were investigated experimentally.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.131-140
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• 1999

This paper presents a study on the flexural ductility of reinforced concrete beams, 16beams with different concrete strength, reinforcement ratio, reinfo- rcement strength. For the purpose of inducing flexural failure, the reinforce ratio ($\rho$-$\rho$') was made not to be more than $0.75\rho$b in accordance with ACi code 318-89. From the test results, it is found that in case of a concrete strength increased from 240 to 650kg/$\textrm{cm}^2$, the displacement and curvature ductility factore are increased by about 31-231 percents. And also increased in case of increased from 650 to 900kg/$\textrm{cm}^2$, but the increasing ratio is gradually decreasing accoding to a concrete strength increases. And also found that as the Double Re-bar Ratio (($\rho$-$\rho$')/$\rho$b) increases, so the displacement and curvature ductility ratio would decrease, but in case of increased from 650 to /$900kg\textrm{cm}^2$ the decreasing ration is bigger than in case of increased from 240 to $650kg/\textrm{cm}^2$.

• Journal of the Korea Institute of Building Construction
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• v.24 no.1
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• pp.23-34
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• 2024

This research aims to assess the flexural bonding efficacy of polymer-cement composites(PCCs) in mending cracks within reinforced concrete(RC) structures. The study involved infilling PCCs into cement mortar cracks of varying dimensions, followed by evaluations of enhancements in flexural adhesion and strength. The findings indicate that the flexural bond performance of PCCs in crack repair is influenced by the cement type, polymer dispersion, and the polymer-to-binder ratio. Specifically, the use of ultra-high early strength cement combined with silica fume resulted in an up to 19.0% improvement in flexural bond strength compared to the application of ordinary Portland cement with silica fume. It was observed that the augmentation in flexural strength of cement mortar filled with PCCs was significantly more dependent on the depth of the crack rather than the width. Furthermore, PCCs not only acted as repair agents but also as reinforcement materials, enhancing the flexural strength to a certain extent. Consequently, this study concludes that PCCs formulated with ultra-high early strength cement, various polymer dispersions, silica fume, and a high polymer-to-binder ratio ranging from 60% to 80% are highly effective as maintenance materials for crack filling in practical settings.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.75-76
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• 2010

Two-way slabs reinforced with high-performance steels were constructed and tested. The influences of the yield strength of flexural reinforcements, the flexural reinforcement ratio, and concentrating the reinforcement in the immediate column region on the punching shear resistance, post-cracking stiffness, strain distribution, and crack control were investigated.