• Title/Summary/Keyword: 부착 강도

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Analytical Model for Transfer Bond Performance of Prestressing Strands (PS 강선의 정착부착성능에 관한 해석 모델)

  • 유승룡
    • Magazine of the Korea Concrete Institute
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    • v.6 no.4
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    • pp.92-101
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    • 1994
  • A new analytical model is proposed to better understand the transfer bond performance in a prestressed pretensioned concrete beam. The transfer length is divided into an elastic and a plas tic zones in this model. The bond stress is assumed t.o increase proportionally with the slip t.o the lirnit of maximum bond stress within the elastic zone and remains at a constant maximum value wthin the plastic zone. Four main stress patterns: bond stress, slip, steel stress, and concrete stress distributions within the transfer length are obtained precisely. The total transfer length al\ulcornerd free-end slip obtained here give a close comparison to the test results by Cousins et al.

Study on Adhesive Strength of Polymer Modified Cement Mortar for Maintenance in Concrete Structure (콘크리트 구조물 보수용 폴리머시멘트 모르타르의 부착강도 특성에 관한 연구)

  • Park, Sang-Soon;Kim, Jung-Heum
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.5
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    • pp.128-135
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    • 2010
  • Polymer-modified cement mortar(PCM) has been widely used for strengthening of the concrete structures due to its excellent physical properties such as high strength and durability. Adhesive strength or behavior, on the other hands, between PCM and concrete is very important in strengthening the concrete member using PCM. Therefore the adhesive failure mechanism between PCM and concrete should be fully verified and understood. This study was performed to evaluate adhesive strength of PCM to the concrete by the direct pull-out test. In the direct pull-out tests, the adhesive strength under the various pre-treatment conditions such as immersion, thunder shower, freezing and thawing are evaluated. Also, the field direct pull-out test are performed to investigate the adhesive strength of mock-up test specimens. In the results of the test, the adhesive strength value by field test are lower than those of the standard curing condition. From these comparison and investigation, field test result was similar with the thunder shower test result. The results of the test was used to evaluate the korean industrial standard of polymer modified cement mortars for maintenance in concrete.

Study on Adhesive Strength of Repair Material in Domestic (국내보수재료의 부착 강도특성에 관한 연구)

  • Park, Sang-Soon;Kim, Jung-Hum;Ryu, Chung-Hyun;Kim, Young-Geun;Park, Hun-Il;Shin, Hong-Chul
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.499-500
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    • 2009
  • This study was performed to evaluate bonding strength of the composites section made of existing concrete and repair mortar in domestic. The pull-out tester was used to test bonding strength for the composites section made of each materials. The results of the test was used to evaluate the korean industrial standard of polymer modified cement mortars for maintenance in concrete structures.

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Combined Effect of Fireproofing Gypsum Board on Residual Strength and Fire Resistance of Fiber Addition High Strength Concrete-Model Column (방화석고보드 부착이 섬유혼입 고강도 콘크리트 모의 기둥부재의 내화특성 및 잔존내력에 미치는 영향)

  • Yang, Seong-Hwan
    • Journal of the Korea Institute of Building Construction
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    • v.12 no.4
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    • pp.442-450
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    • 2012
  • In this study, fire resistance and residual strength were examined after the addition of PF fiber and bonding fireproofing gypsum board to a high strength concrete-model column of 50 MPa grade. At the beginning of the experiment, all the properties of base concrete appeared to satisfy the target range. In terms of the internal temperature record, a trend of slightly high temperature was shown when the fireproofing gypsum board was not bonding, and when the fireproofing gypsum board was bonding, as PF content increased gradually, the temperature was gradually lowered. In terms of the relationship, as time elapsed a low temperature was shown when fiber was mixed, and when the board was bonding, the trend of lower temperature could be confirmed. Meanwhile, in terms of spalling property, a severe explosive fracture was generated at PF 0%, and falling off was prevented as the fiber content was increased; however, discoloration and a multitude of cracks were discovered, and when the board was bonding, the trend in which the exterior became satisfactory when the content was increased emerged. In terms of the residual compressive strength, measuring of strength could not be performed at PF 0% without bonding of board, and the strength was increased as the fiber content was increased; however, there was a decrease in strength of about 30 ~ 40%, and in the case of PF 0% with the bonding of board, the strength could be measured; however, about an 80% decrease in strength was shown, and only about a 10 ~ 20% decline in strength was displayed, as the range of decrease was reduced as the fiber content was increased. Considering all of these factors, it was determined that a more efficient enhancement of fire resistance was obtained when two methods are applied in combination rather than when the PF fiber content and bonding of fireproofing gypsum board are utilized individually.

The Prediction of Debonding Strength on the Reinforced Concrete Beams Strengthened with fiber Reinforced Polymer (섬유복합체로 휨보강된 RC보의 박리하중 예측에 관한 연구)

  • Hong Geon-Ho;Shin Yeong-Soo
    • Journal of the Korea Concrete Institute
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    • v.17 no.6 s.90
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    • pp.903-910
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    • 2005
  • In recent years, fiber reinforced polymer(FRP) plates have shown a great promise as an alternative to steel plates for reinforced concrete beam rehabilitation. Reinforced concrete beams strengthened with externally bonded FRP sheets to the tension face can exhibit ultimate flexural strengths several times greater than their original strength if their bond strength is enough. Debonding failure, however, may occur before the strengthened beam can achieve its enhanced flexural strength. The purpose of this paper is to investigate the debonding failure strength of FRP-strengthened reinforced concrete beams. An analytical procedure for calculating debonding load between concrete and strengthening FRP is presented. Based on the local bond stress-slip relationship in the previous studies, uniform bond stress is assumed on the effective bond length. The analytical expressions are developed from linear elastic theory and statistical analyses of experimantal results reported in the literature. The proposed method is verified by comparisons with experimental results reported in the previous researches.

Evaluation of Bond Behavior of Reinforced Concrete Beams with High-Strength Transverse Reinforcement (고강도 횡보강근을 사용한 철근콘크리트 보의 부착 거동 평가)

  • Kim, Sang-Woo;Kim, Young-Sik;Baek, Seung-Cheol;Kim, Kil-Hee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.5
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    • pp.102-109
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    • 2010
  • This paper investigates the bond behavior of reinforced concrete beams having high-strength transverse reinforcement. A total of four reinforced concrete beams were tested in this study to estimate the bond capacity of the proposed U-shape reinforcement. The proposed U-shape reinforcement not only has a simple structure to install, but also can increase the bond capacity of reinforced concrete beams by controling bond cracks. This study follow the test method proposed by Ichinose to obtain the bond stress and the bond slip of the specimens. The main test parameters were the yield strength, ratio, and reinforcing types of transverse reinforcements. It was found that the proposed U-shape reinforcement was able to effectively improve the bond performance of reinforced concrete beams with high-strength transverse reinforcement.

Inverstigation of Maximum Strength and Effective Bonding Length at the Interface between Concrete and FRP Materials under Freeze-thaw Cycles and Applied Different Bonding Materials (동결융해 및 부착재료 변화에 따른 FRP-Concrete 경계면의 최대 부착강도 및 유효부착길이 평가)

  • Kim, Sung-Hoon;Jung, Woo-Young;Choi, Hyun-Kyu
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.435-436
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    • 2010
  • This research presents two important factors; first, the advanced design equation of effective bonding length at the interface between concrete and FRP materials is proposed when different bonding materials are applied and secondly maximum bonding strength between concrete-FRP bonding surface is evaluated under Freeze-thaw cycles.

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Evaluation of Flexural Bond Performance of Hybrid Concrete Repair Materials (하이브리드 콘크리트 보수재료의 휨부착 성능평가)

  • Kim, Gyeong Tae;Kim, Sang Jun;Park, Hong Gi;Choi, Young Cheol
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.6
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    • pp.176-181
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    • 2018
  • Concrete structures are degraded physically and chemically due to various reasons after construction. Because the deterioration of concrete structure reduces the service life, reasonable repair and maintenance techniques are needed. Recently, in order to efficiently repair concrete structures, many researches on hybrid repair materials having improved adhesion performance have been carried out actively. In this study, we developed a hybrid repair material containing rapid hardening cement, PVA powder, nylon fiber, and latex to improve adhesion and water-tightness of existing concrete. The compressive strength, drying shrinkage and the adhesion strength test were carried out to evaluate the performance of the repair material. In addition, the flexure bond performance was evaluated before and after repair. From the results, the bending strength was 110% ~ 150% in all specimens except for the specimen containing only the rapid hardening cement, and all the specimens behaved with the existing concrete in the crack pattern generated by the bending strength.

Characteristics of Bond Strength in Concrete Beams Reinforced with Galvanized Rebar (용융아연도금 철근콘크리트 보의 부착강도 특성)

  • Shin, Jae-Hyuk;Kim, Kyoung-Chul;Yang, In-Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.4
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    • pp.136-143
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    • 2015
  • Galvanizing is one of the method used to solve the problem of corrosion of reinforcement in concrete structures. There few research reported in the literature regarding the effect of galvanized coating on the behavior of lap splices in concrete beams. The objective of this study was to determine whether galvanized rebar adversely affects lap splice behavior and bond strength. Concrete beams reinforced with black or galvanized rebar were tested in flexure. The test variables included the presence of galvanized rebar steel diameter, and lengths of lap splices. The study concentrated on comparing crack, failure pattern, and bond strength. The ultimate behavior of beams reinforced with galvanized rebar was not significantly different from that of black steel reinforced beams. Therefore, the test results indicated that the use of galvanizing-coated rebar had no adverse effect on behavior in lap splices of rebar compared to the use of black rebar.

A FEA Study on the Bond Property according to the Rib-Shape of Reinforcement (철근 마디형상에 따른 부착특성에 관한 해석적 연구)

  • Mihn, Joon-Soo;Hong, Geon-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.2
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    • pp.38-46
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    • 2014
  • Effects of various parameters on bond property between reinforcing bar and concrete are investigated in many researchers, and various study is on going to improve the bond strength. Properties of interface between reinforcement and concrete is important role in bond property. This study analyzed the interfacial bond mechanism between deformed bar and concrete by finite element analysis (FEA) to evaluate the effect of rib shape. The FEA model in this study is simplified 2D plane stress model. The variables of analysis are selected by rib angle, rib height, rib spacing and relative rib area. From the results of analysis, reinforcing bars with rib angle $30{\sim}60^{\circ}$ showed better bond strength than the others. Bond strength ratio following to the rib height is proportionally increased up to the $0.12d_b$, but rib spacing has little effect on bond strength. The results also indicated that relative rib area can be efficiently represented the properties of deformed shape in reinforcing bars, and zigzagged rib height shape showed excellent bond strength increase.