• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.617-620
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• 1999

The purpose of this study is to find the influence of interface and confinement on bond between reinforcing steel and concrete subjected to monotonic and cyclic loading. The key variables for the experimental program include rib height, rib spacing for reinforcing bars and confinement. From the results obtained in this study, the following main observations can be made for the bond properties. Bond strength increases when confinement increases under monotonic and cyclic loading. Bond stiffness and strength drop remarkably after the maximum bond strength. Both bond stiffness and strength also drop at a constant slip when the number of cyclic loading increase. The bond resistance subjected to cyclic loading decreases significantly for reinforcing bars with low rib height.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.201-204
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• 2006

The shear resistance of RC beams is subject to the amount of shear-reinforcing bars ($p_w$) and yield strength ($f_{wy}$) as well as their interactive influence ($p_wf_{wy}$). Thus, it is reasonably expected that high-strength steel bars can greatly reduce the necessary amount of shear-reinforcing bars. On the other hand, although the bond strength is influenced by the amount of shear reinforcing bars, it is not affected by the yield strength. Thus, there is often an issue that bond failure occurs before shear failure depending on the arrangement of shear reinforcing bars. It is a common practice to set sub-ties for the transverse confinement of the main re-bars as a method to prevent the bond failure. However, it can also become a factor in decreased work efficiency due to the complexity of the construction. This study experimented with simultaneous use of high-strength transverse reinforcing bars ($f_{wy}=800MPa$) and U-shaped transverse reinforcing bars of regular strength ($f_{wy}=300MPa$) in an attempt to decrease the necessary quantity of shear reinforcing bars. The effect of this attempt was investigated through fundamental experimental research in terms of the improvement in shear resistance and bond strength as well as the ease of construction.

• Advances in materials Research
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• 제8권1호
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• pp.25-36
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• 2019

The utilization of fibre in concrete production not only solves the problem of disposing this solid waste but helps conserve natural resources. This study investigated the effect of waste aluminum shavings on bond strength of laterized concrete. Laterized concrete spliced beams of $150{\times}250{\times}2150mm$ and $175{\times}275{\times}2300mm$ were prepared. Fifteen specimens with 16 mm and 20 mm were cast with the addition of aluminium shavings at varying percentages of 1vol%, 1.5vol% and 2vol%; another ten specimens with 16 mm and 20 mm diameter bars at 0% of aluminium shavings were cast as control. Concrete cubes of number were prepared, three taken for each set of various percentages of aluminium shavings were used to determine the concrete strength. It was observed from the analysis that the compressive strength decreased as the percentage of aluminium shavings increased, while the aluminium shavings increased the bond between concrete and steel. However, for normal concrete there was an increase in bond resistance with increase in aluminium shavings. The bond resistance of 16 mm was found to be higher than that of 20 mm in all the specimens tested.

• 대한치과의사협회지
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• 제22권9호통권184호
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• pp.781-792
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• 1984

The purpose of this experiment was to study the effects of laser on a base metal alloy for dental casting. In this study, microhardness, corrosion resistance, wear resistance, interaction behavior of metal-ceramic interface, and bond strength were tested before and after the laser treatment for metal-ceramic alloy. The conclusion arised from this study are as follows: 1. The hardness of lased area was higher than that of unlased area. 2. The corrosion resistance was higher in lased specimen than in unlased specimen. 3. the wear resistance was higher in Iased specimen than in unlased specimen. 4. The EDAX showed that Mo, Si and Al were increased in lased surface but Ni and Cr not increased. 5. The SEM of lased area revealed a typical microstructure. 6. The bond strength of lased specimen was increased in 11.2% than of unlased specimen.

• 한국구조물진단유지관리공학회 논문집
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• 제17권4호
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• pp.75-83
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• 2013

본 연구에서는 탄소섬유판을 이용하여 표면매입 보강된 철근콘크리트 부재의 내화성능에 관한 연구로서 온도변화에 따른 탄소섬유 판의 인장시험, 에폭시의 상태변화 실험, 그리고 온도변화에 따른 부착성능에 관한 일련의 실험연구를 실시하였다. 실험연구로부터, 부착강도의 측면에서 콘크리트를 보강하기 위한 효율적인 보강방법은 표면매입 보강이며, 이 보강법은 상온에서는 그 효과가 매우 높지만, 비록 낮은 온도일지라도 주변온도가 높아질 경우에는 보강효과가 현저히 저하될 수 있음을 확인하였다. 특히, 주변 온도가 에폭시의 화학적 성질이 변화하기 시작하는 유리전이 온도에 근접할 경우, 부착기능이 상실되기 시작하므로 구조물의 안전한 내화설계를 위해서는 부착용으로 사용되는 에폭시의 성능을 개선시키고 또한 섬유보강재의 성능개선이 시급한 것으로 사료된다.

• 콘크리트학회지
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• 제11권2호
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• pp.251-259
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• 1999

최근 다양한 침해환경에 건설되는 구조물이 증가함에 따라 철근 및 강재의 부식위험성이 높아지면서, 철근 콘크리트 구조물의 내구성 저하문제가 큰 관심으로 떠오르고 있다. 특히 해양 환경하에 건설된 철근 콘크리트 구조물의 경우 구조물 외부로부터 침투되는 염분의 영향으로 인한 철근부식이 발생 및 진행되어 콘크리트 구조물에 균열, 박리 등의 손상을 받게된다. 그러므로 해양콘크리트 구조물은 염해에 대해 내구성 및 신뢰성 확보가 중요시되고 있다. 따라서, 본 연구에서는 철근의 부착강도를 크게 감소시키지 않게 하는 방법으로서 시멘트 계통의 방청시멘트를 철근에 도막한 후 내부식성능과 부착강도특성을 실험적으로 연구하였다. 본 연구결과, 방청시멘트 도막철근은 소요의 내부식성능을 갖고 있으면서도 부착강도특성도 일반철근과 유사하였으며, 앞으로 실구조물의 내구성증진을 위해 효율적으로 사용될 수 있는 토대가 될 것으로 사료된다.

• BMB Reports
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• 제44권11호
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• pp.747-752
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• 2011

To investigate the effects of disulphide bond position on the salt resistance and lipopolysaccharide (LPS)-neutralizing activity of ${\alpha}$-helical homo-dimeric antimicrobial peptides (AMPs), we synthesized an ${\alpha}$-helical model peptide ($K_6L_4W_1$) and its homo-dimeric peptides (di-$K_6L_4W_1$-N, di-$K_6L_4W_1$-M, and di-$K_6L_4W_1$-C) with a disulphide bond at the N-terminus, the central position, and the C-terminus of the molecules, respectively. Unlike $K_6L_4W_1$ and di-$K_6L_4W_1$-M, the antimicrobial activity of di-$K_6L_4W_1$-N and di-$K_6L_4W_1$-C was unaffected by 150 mM NaCl. Both di-$K_6L_4W_1$-N and di-$K_6L_4W_1$-C caused much greater inhibitory effects on nitric oxide (NO) release in LPS-induced mouse macrophage RAW 264.7 cells, compared to di-$K_6L_4W_1$-M. Taken together, our results indicate that the presence of a disulphide bond at the N- or C-terminus of the molecule, rather than at the central position, is more effective when designing salt-resistant ${\alpha}$-helical homo-dimeric AMPs with potent antimicrobial and LPS-neutralizing activities.

• 한국구조물진단유지관리공학회 논문집
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• 제9권1호
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• pp.233-241
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• 2005

본 연구는 콘크리트로 충전한 절곡된 단면을 갖는 각형강관 기둥의 부착특성을 매입인발(Pull-out) 시험을 통해 평가하였다. 시험체는 단면 $250{\times}250mm$의 강관 단면에 콘크리트를 충진한 PSSC기둥으로 표준형(P), 사다리꼴(I), 직사각형(II), 역사다리꼴(III)의 4가지 형태(Fig. 3)와, 부착길이에 대한 폭비 (L/D=2.0, 2.5, 3.0) 단면의 폭두깨비(d/t)으로 설정하여 총 13로 하였다. 실험결과 얇은 판요소 절곡된 강관과 콘크리트의 부착거동은 일반적인 부착거동과 유사하게 화학적 부착과 기계적 부착의 형태로 거동하였으며, 부착응력은 강판의 절곡형태가 (equation omitted)순으로 높게 나타났다. 또한 (equation omitted)타입 시험체의 경우에는 얇은 판요소를 갖는 단면임에도 불구하고 AIJ에서 제시하고 있는 $0.147N/mm^2$의 값을 상회하는 것으로 나타나 부착응력을 고려할 수 있을 것으로 판단되었다.

• Structural Engineering and Mechanics
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• 제16권4호
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• pp.469-478
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• 2003

The primary aim of this study was to investigate the bond strength between reinforcement and concrete. Large sized nine beams, which were produced from concrete with approximately ${f_c}^{\prime}=30$ MPa, were tested. Each beam was designed to include two bars in tension, spliced at the center of the span. The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. In all experiments, the variable used was the reinforcing bar diameter. In the experiments, beam specimens were loaded in positive bending with the splice in a constant moment region. In consequence, as the bar diameter increased, bond strength and ductility reduced but, however, the stiffnesses of the beams (resistance to deflection) increased. Morever, a empirical equation was obtained to calculate the bond strength of reinforcement and this equation was compared with Orangun et al. (1977) and Esfahani and Rangan (1998). There was a good agreement between the values computed from the predictive equation and those computed from equations of Orangun et al. (1977) and Esfahani and Rangan (1998).

• Steel and Composite Structures
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• 제11권3호
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• pp.233-250
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• 2011

An experimental study has been carried out to reveal the shear-bond failure mechanism of composite deck slabs. Thirteen full scale simply supported composite slabs are studied experimentally, with the influence parameters like span length, slab depth, shear span length and end anchorage provided by steel headed studs. A dozen of strain gauges and LVDTs are monitored to capture the strain distribution and variation of the composite slabs. Before the onset of shear-bond slip, the longitudinal shear forces along the span are deduced and found to be proportional to the vertical shear force in terms of the shear-bond strength in the m-k method. The test results are appraised using the current design procedures. Based on the partial shear-bond connection at the ultimate state, an improved method is proposed by introducing two reduction factors to assess the moment resistance of a composite deck slab. The new method has been validated and the results predicted by the revised method agree well with the test results.