• 한국지반신소재학회논문집
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• 제16권1호
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• pp.19-29
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• 2017

시멘트-점토-모래 혼합토의 휨성능 개선을 위하여 합성섬유를 이용해서 보강한 섬유보강토에 대한 휨성능 시험을 실시하였다. 시멘트, 모래, 그리고 섬유가 혼합토의 휨성능에 미치는 영향을 평가하기 위하여 시멘트량(15%, 20%, 25%), 모래함량(0%, 10%, 20%), 섬유의 종류(PP, PVA)와 길이(6mm, 12mm), 섬유혼입량(0.5%, 1.0%, 1.5%)을 조합하여 시험편을 제작하였다. 본 연구의 결과 시멘트 개량토를 섬유를 이용해서 보강하면 휨강도와 휨인성이 개선되는 효과를 확인할 수 있었다. 휨성능 시험 결과에 대한 다중선형회귀분석 결과 시멘트량과 모래함량은 휨강도에 영향을 미치는 주요 인자인 것으로 나타났고, 반면에 섬유혼입량은 균열발생 후의 거동에 영향을 미치는 주요 인자인 것으로 나타났다.

• 구강회복응용과학지
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• 제23권4호
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• pp.269-281
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• 2007

Fluoric acid etching is an essential procedure in cementation of reinforced ceramics to tooth surface. But there have been few studies about the changes of surface structure and flexural strength of IPS $Empress^{(R)}$ 2 ceramic according to the etching time. The objectives of this study were to examine the surface structure changes and the difference in biaxial flexural strength of IPS $Empress^{(R)}$ 2 ceramic according to various etching times. Sixty one disk-shaped specimens of IPS $Empress^{(R)}$ 2 ceramic($14mm{\times}1.2mm$) were fabricated for the biaxial flexural strength test and SEM analysis according to the manufacturer's recommendations. Sixty specimens were divided into 6 groups(n=10) according to the time of HF acid etching(0, 20, 180 and 300s)and silane/resin cement application. Each disk was loaded using a piston-on-3 ball biaxial configuration in a universal testing machine. The failure loads(N) were recorded, and the biaxial flexural strength for each disk was calculated. A one-way analysis of variance and independent t-test on transformed fracture strength data were used to determine significant differences between groups. The groups of no cementation showed a trend toward progressive weakening with increasing the etching time. However, this was not statistically significant at p=0.05 level. The groups of resin cementation exhibited no apparent trend in their mean strength values. SEM photomicrographs showed very different results of etching. Within the conditions of this study, alteration of surface topography by acid etching does not have a deleterious effect on the biaxial flexural strength of IPS $Empress^{(R)}$ 2 ceramic.

• The Journal of Advanced Prosthodontics
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• 제10권5호
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• pp.361-366
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• 2018

PURPOSE. The aim of this study was to evaluate the effects of relining materials on the flexural strength of relined thermoplastic denture base resins (TDBRs). MATERIALS AND METHODS. For shear bond strength testing, 120 specimens were fabricated using four TDBRs (EstheShot-Bright, Acrytone, Valplast, Weldenz) that were bonded with three autopolymerizing denture relining resins (ADRRs: Vertex Self-Curing, Tokuyama Rebase, Ufi Gel Hard) with a bond area of 6.0 mm in diameter and were assigned to each group (n=10). For flexural strength testing, 120 specimens measuring $64.0{\times}10.0{\times}3.3mm$ (ISO-1567:1999) were fabricated using four TDBRs and three ADRRs and were assigned to each group (n=10). The thickness of the specimens measured 2.0 mm of TDBR and 1.3 mm of ADRR. Forty specimens using four TDBRs and 30 specimens using ADRRs served as the control. All specimens were tested on a universal testing machine. For statistical analysis, Analysis of variance (ANOVA) with Tukey's test as post hoc and Spearman's correlation coefficient analysis (P=.05) were performed. RESULTS. Acry-Tone showed the highest shear bond strength, while Weldenz demonstrated the lowest bond strength between TDBR and ADRRs compared to other groups. EstheShot-Bright exhibited the highest flexural strength, while Weldenz showed the lowest flexural strength. Relined EstheShot-Bright demonstrated the highest flexural strength and relined Weldenz exhibited the lowest flexural strength (P<.05). Flexural strength of TDBRs (P=.001) and shear bond strength (P=.013) exhibited a positive correlation with the flexural strength of relined TDBRs. CONCLUSION. The flexural strength of relined TDBRs was affected by the flexural strength of the original denture base resins and bond strength between denture base resins and relining materials.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.146-147
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• 2022

Exposed composite beams composed of H-beams and concrete slabs are generally used in building structures because of their excellent economics and flexural strength. However, deep beams used under large load often make difficulties in construction. In this study, an exposed composite beam with high strength steel (SM460) used in the bottom flange of built-up H-shaped beam, so-called S-Beam, was proposed in order to reduce beam depth. And its positive and negative flexural strengths were experimentally evaluated. The test results showed that S-Beam has excellent flexural strength and ductility.

• 대한치과기공학회지
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• 제43권2호
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• pp.35-41
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• 2021

Purpose: This study aimed to investigate the flexural strength and surface microstructure of the zirconia crown according to the number of glazing zirconia prostheses. Methods: The specimens were made as follows. A specimen without glazing: 1ea, first glazed specimens (group B): 10ea, second glazed specimens (group C): 10ea, third glazed specimens (group D): 10ea. Three-point measuring strength equipment and electron microscopes were used for strength measurement and microstructure observation. As for statistical analysis, one-way ANOVA and t-test (level of significance level=5%) were used to determine the difference in the change in flexural strength according to the number of glazing zirconia prostheses. Results: ANOVA analysis of groups B (1st glazing), C (2nd glazing), and D (3rd glazing) revealed that the change in strength between the groups is statistically significant (p=0.023). The Mann-Whitney test for each group revealed that the difference in flexural strength between groups B and C was not statistically significant (z=-0.302, p=0.762) while that between groups C and D was statistically significant (z=-0.257, p=0.01). Microstructure observation revealed 3 changes in the microstructure of the surface of the glaze powder were observed. Conclusion: According to the number of glazing zirconia prostheses, it was found that the difference in strength between groups was statistically significant, and changes in the microstructure were observed.

• 한국안전학회지
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• 제14권1호
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• pp.129-140
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• 1999

This study presents test results of RC beams strengthened by steel plates, carbon fiber sheets(CFS) and aramid fiber sheets(AFS) for increasing flexural and shear resistance. The test was performed with different parameters including the type of strengthening materials, flexural-strengthening methods and shear-strengthening methods. In case of flexural test, RC beams are initially loaded to 70% of the ultimate flexural capacity and in case of shear test loaded to 60 or 80 percent of the ultimate shear capacity and subsequently reinforced with steel plates, CFS and AFS. Experimental data on strength, steel strain, deflection, and mode of failure of the reinforced beams were obtained, and comparisons between the different shear reinforced schemes and the non-strengthened control beams were made. The test results showed that damaged RC beams strengthened by steel plates, CFS and AFS have more improved the flexural and shear capacity. For the beams with external reinforcement by steel plates, aramid fiber sheets and carbon fiber sheets increases in ultimate strength of 4 to 21, 17 to 43 and 26 to 36 percent were respectively achieved. Initial load had small effect on strength after reinforcement, but an important influence on deflection. One sheet reinforced was stronger than two sheets reinforced but less deflected than two sheets reinforced.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.579-584
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• 2001

The reinforced concrete(RC) beam is developed cracks because the compression strength of concrete is strong but the tensile strength is weak. The structural strength and stiffness is decreased by reduction of tension resistance capacity of concrete due to the developed cracks. Using the fiber reinforced concrete that is increased the flexural strength and tensile strength at tensile part can enhance the strength and stiffness of concrete structure and decrease the tensile flexural cracks and deflection. Therefore, The reinforced concrete used the fiber reinforced concrete at tensile part ensure the safety and serviceability of the concrete structures. In this study, analytical model of a dual concrete beam that is composed of the normal strength concrete at compression part and the high tensile strength concrete at tensile part is developed by using the equilibrium condition of forces and compatibility condition of strains and is parted into elastic analytical model and ultimate analytical model. Three group of test beam that is formed of one reinforced concrete beam and two dual concrete beams for each steel reinforcement ratio is tested to examine the flexural behavior of dual concrete beams. The comparative study of total nine test beams is shown that the ultimate load of a dual concrete beams relative to the reinforced concrete beams have an increase in approximately 30%. In addition, the initial flexural rigidity, as used here, refer to the slope of load-deflection curves in elastic state is increased and the deflection is decreased.

• The Journal of Advanced Prosthodontics
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• 제3권3호
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• pp.136-139
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• 2011

PURPOSE. A new light curing urethane dimethacrylate and a cold curing resin with simpler and faster laboratory procedures may have even improved flexural properties. This study investigated the 3-point flexural strengths and flexural moduli of two alternate base materials. MATERIALS AND METHODS. A cold curing resin (Weropress) and a light curing urethane dimethacrylate base material (Eclipse). Along with Eclipse and Weropress, a high impact resin (Lucitone199) and three conventional base materials (QC 20, Meliodent and Paladent 20) were tested. A 3-point bending test was used to determine the flexural strengths and flexural moduli. The mean displacement, maximum load, flexural modulus and flexural strength values and standard deviations for each group were analyzed by means of one-way analysis of variance (ANOVA) (with mean difference significant at the 0.05 level). Post hoc analyses (Scheffe test) were carried out to determine the differences between the groups at a confidence level of 95%. RESULTS. Flexural strength, displacement and force maximum load values of Eclipse were significantly different from other base materials. Displacement values of QC 20 were significantly different from Lucitone 199 and Weropress. CONCLUSION. The flexural properties and simpler processing technique of Eclipse system presents an advantageous alternative to conventional base resins and Weropress offers another simple laboratory technique.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
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• pp.71-76
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• 1994

Eight singly reinforced high strength concrete beams were tested to investigate their flexural behavior. The variable is tensile steel raio. The test results are presented in terms of load-deformation behavior, ductility indexes, and cracking patterns. The flexural strengths obtained experimentally are compapred to the analytical results, and good agreements are obtained. The flexural design provisions of the ACI Building Code are found to be adequate to predict the strength of reinforced high-strength concrete beams.

• International Journal of Safety
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• 제11권2호
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• pp.26-28
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• 2012

In this thesis, fracture tests were carried out in order to investigate the flexural strength behavior of FRC(fiber reinforced concrete) structures. FRC beams were used in the tests, the initial crack load and the ultimate load of the beams were observed under the static loading. According to the results, the ultimate loads increase with the fiber content, and these tendency is clear in the specimens with large fiber aspect ratio. From the results of the regression analysis, practical formulae for predicting the flexural strength of FRC were suggested.