• Title/Summary/Keyword: 부착 실험

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Effect of Bond Length and Web Anchorage on Flexural Strength in RC Beams Strengthened with CFRP Plate (부착길이와 복부정착이 CFRP판으로 보강된 RC 보의 휨 보강효과에 미치는 영향)

  • 박상렬
    • Journal of the Korea Concrete Institute
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    • v.14 no.5
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    • pp.645-652
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    • 2002

  • This paper presents the flexural behavior and strengthening effect of reinforced concrete beams bonded with carbon FRP plate. Parameters involved in this experimental study were plate bond length and sheet web anchorage length. Test beams were strengthened with FRP plate on the soffit and anchored with FRP sheet on the web. In general, strengthened beams with no web anchorage were failed by concrete cover failure along the longitudinal reinforcement. On the other hand, strengthened beams with web anchorage were finally failed by delamination shear failure within concrete after breaking of CFRP sheet wrapping around web. The ultimate load and deflection of strengthened beams increased with an increased bond length of FRP plate. Also, the ultimate load and deflection increased with an increased anchorage length of FRP sheet. Particularly, the strengthened beams with web anchorage maintained high ultimate load resisting capacity until very large deflection. The shape of strain distribution of CFRP plate along beam was very similar to that of bending moment diagram. Therefore, an assumption of constant shear stress in shear span could be possible in the analysis of delamination shear stress of concrete. In the case of full bond length, the ultimate resisting shear stress provided by concrete and FRP sheet Increased with an increase of web anchorage length. In the resisting shear force, a portion of the shear force was provided by FRP anchorage sheet.

  • https://doi.org/10.4334/JKCI.2002.14.5.645 인용 PDF KSCI

The Effect of Resin Base Surface Treatment on Shear Bond Strength in Indirect Bracket Bonding Technique (브라켓 간접부착술식시 레진베이스의 표면처리가 전단결합강도에 미치는 영향)

  • Yim, Byeong-Cheol;Hwang, Hyeon-Shik
    • The korean journal of orthodontics
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    • v.28 no.5 s.70
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    • pp.681-688
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    • 1998

  • The purpose of this study was to evaluate the effects of the surface treatments of resin bases in indirect bracket bonding technique by study of shear bond strengths and failure patterns. Ninety metal brackets were bonded to the stone models of specimens involving bovine lower incisor with light-cured adhesive(Light-Bond). After removal of brackets with the resin base from the stone models, the surfaces of resin bases in thirty brackets were treated with Plastic Conditioner and the surfaces of resin bases in another thirty brackets were treated with sandblaster and the remaining thirty brackets were served as controls. All brackets were transferred to the specimens and bonded using sealant. The shear bond strength was tested on universal testing machine, and failure pattern was assessed with the adhesive remnant index(ARI). The results were as follows: 1. Surface treatments of resin bases with Plastic Conditioner or sandblasting showed statistically higher shear bond strengths than no treatment group. 2. No significant difference in shear bond strength was found between Plastic Conditioner treatment and sandblasting treatment groups. 3. No significant difference in ARI scores was found among the three groups. 4. As the result of correlation analysis between shear bond strengths and hnl scores, failure at adhesive/bracket base interface tends to increase when the shear bond strength was high, but it was not significant statistically. The above results suggest that improvement of bond strength can be obtained by surface treatment of resin base in the indirect bonding technique.

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Prediction Model of Unbonded Tendon Stresses in Post-Tensioned Members (포스트텐션 부재에서 비부착긴장재의 응력 거동 예측 모델)

  • Kim, Kang-Su;Lee, Deuck-Hang;Kal, Gyung-Wan
    • Journal of the Korea Concrete Institute
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    • v.21 no.6
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    • pp.763-771
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    • 2009

  • As the demand on long span structures increases more in recent years, the excessive deflection, in addition to the ultimate strength, in horizontal members becomes a very important issue. For this reason, as an alternative method to effectively solve the deflection problems, the application of post-tensioned structural system with unbonded tendon increases gradually. However, most of the existing researches on post-tensioned members with unbonded tendons (UPT) focused on the ultimate flexural strength, which would be impossible or improper to check serviceability such as deflections. Therefore, this study aims at proposing a stress prediction model for unbonded tendons that is applicable to the behavior of UPT members from the very initial loading stages, post-cracking states, and service to ultimate conditions. The applicability and accuracy of the proposed model were also evaluated comparing to the existing test results from literature. Based on such comparison results, it was verified that the proposed model provided very good predictions on tendon stresses of UPT members at various loading stages regardless their different characteristics; wide range of reinforcement index, different loading patterns, and etc. The proposed model especially well considered the effect of various loading types on stress increases of unbonded tendons, and it was also very suitable to apply on the over-reinforced members that easily happened during strengthening/repairing work.

  • https://doi.org/10.4334/JKCI.2009.21.6.763 인용 PDF KSCI

AN EFFECT OF XYLITOL ON THE ADHESIVENESS OF STREPTOCOCCUS MUTANS TO SYNTHETIC HYDROXYAPATITE; AN IN VITRO STUDY (자일리톨 함유 식품이 합성 수산화인회석에 대한 Streptococcus mutans의 부착에 미치는 영향에 관한 실험적 연구)

  • Lee, Jae-Chun;Lee, Kwang-Hee;Kim, Dae-Eop
    • Journal of the korean academy of Pediatric Dentistry
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    • v.29 no.1
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    • pp.92-99
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    • 2002

  • There have been efforts that inhibit development of dental caries by sugar substitution. But, it is controversial if xylitol has anticariogenic effect in the presence of sucrose. And there are few papers dealing with the combined action of xylitol and sucrose. For the purpose of resolving this controversy, the author investigated the effect of xylitol on enamel demineralization and on adhesiveness of S. mutans to hydroxyapatite in the presence of sucrose. Five experimental solutions were prepared as follows: (S: sucrose, X: xylitol) Group 1: BHI broth Group 2: BHI+1% S Group 3: BHI+0.75% S+0.25% X Group 4: BHI+0.5% S+0.5% X Group 5: BHI+0.25% S+0.75% X Group 6: BHI+1% X Each solution was inoculated with $100{\mu}l$ of S. mutans JC-2. And saliva coated hydroxyapatite beads were put into each experimental solution. And then each solution was incubated at $37^{\circ}C$ under anaerobic condition. After incubation, the adhesiveness of S. mutans on hydroxyapatite was evaluated. The Vickers hardness numbers were measured on extracted human primary teeth, and these teeth were dipped into the same experimental solution and incubated at $37^{\circ}C$ under anaerobic condition for 48hours. Surface microhardness were measured again after incubation. The obtained results were as follows; 1. In the presence of sucrose, xylitol can reduce the adhesiveness of S. mutans on hydroxyapatite surface from the ratio of 25% sucrose to 75% xylitol(P<0.05). 2. In the presence of sucrose, xylitol can reduced demineralization of primary teeth enamel surface from the ratio of 50% sucrose to 50% xylitol(P<0.01).

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