• Computers and Concrete
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• 제26권6호
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• pp.587-593
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• 2020

In this study, bond behavior of ordinary concrete and rebars with different diameters and development length was investigated by using Hinged Beam Test (HBT) and Eccentric Pull-Out Test (EPT) comparatively. For this purpose, three different rebar size and development length depending on rebar diameter were chosen as variables. Three specimens were produced for each series of specimens and totally 54 specimens were tested. At the end of the tests it was observed that obtained results for both tests were quite similar. On the other hand, increased bar size, especially for the specimen with 14 mm bar size and 14 development length (lb), caused shear failure of test specimens. This situation infers that when bigger bar size and lb are used in such test, dimensions of test specimens should be chosen bigger and stirrups should be used for producing of test specimens to obtain more adequate result by preventing shear failure. Also, a nonlinear regression analysis was employed between HBT and EPT results. There was a high correlation between the EPT values, lb, rebar diameters and estimated theoretical HBT. In addition, at the end of the study an equation was suggested to estimate bond strength for HBT by using EPT results.

• 한국도로학회논문집
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• 제19권2호
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• pp.17-24
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• 2017

PURPOSES : This study aims to develop a sealant for use in the installation of Weigh-In-Motion (WIM) sensor for asphalt concrete or cement concrete pavements. METHODS : In order to investigate the properties of various sealants that were mixed with latex and carbon fiber, various test methods were adopted, such as bituminous bond strength test, softening point test, and cone penetration test. To evaluate moisture susceptibility, the BBS test was conducted under moist condition. The bond strength ratio (BSR) was calculated based on tensile strength ratio method. RESULTS : The sealant's properties significantly varied according to the amount of latex or carbon fiber. The usage of latex marginally enhanced the cone penetration test result, notwithstanding reduced asphalt content. This implies that the sealant will be proper cold temperature reason. Moreover, the addition of latex and carbon fiber evidently increased the softening point. This indicates that the tendency of the material to flow at elevated temperatures is encountered during service. With the addition of latex and carbon fiber, the moisture susceptibility measured with BSR improved marginally, while the bond strength under dry condition decreased marginally. Sealant F displays the highest bond strength and BSR under limited test conditions. CONCLUSIONS : According to the proportion of latex and carbon fiber mixed, properties of sealant, such as softening point, cone penetration, and BSR varied marginally. This indicates that the sealant has to be applied considering the environmental condition, to improve service life.

• 한국건설순환자원학회논문집
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• 제7권3호
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• pp.271-278
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• 2019

철근 콘크리트 구조물에서 철근의 부식은 내구성 문제를 발생시키고 있으며, 이에 대한 대책의 하나로 에폭시 도막철근이 사용되고 있다. 그러나 에폭시 도막철근을 사용하는 경우 철근 부식에 대한 저항성능은 우수하나 철근에 에폭시 도막을 함으로써 콘크리트와의 부착력이 일반철근에 비하여 감소하는 단점이 있다. 따라서 부착성능에 대한 실험적인 확인이 필요하여 ACI 408R에서 제시하는 대표적인 실험 방법인 휨 부재를 통하여 부착거동을 연구할 수 있는 보-단부 test와 직접인발을 통해 부착 특성을 분석하는 Pullout test를 통하여 부착성능을 평가하였다. 에폭시 도막 철근의 부착실험은 휨 부재실험과 직접인발 실험 모두 지름 13, 19mm의 철근에 대한 콘크리트 도막두께를 철근 지름의 3배로 하여 수행되었다. 실험 결과 에폭시 도막철근의 부착강도는 철근의 지름이 증가할수록 에폭시 도막 철근과 일반철근의 부착강도차이가 증가하였고 파괴형상은 모두 뽑힘 파괴를 나타내었다. 또한, 직접인발시험으로 구한 부착-미끌림 관계에 근거하여 유한요소해석을 수행하고, 휨 실험결과와 비교하였다. 부착성능을 평가하는 방법으로 실제 구조물에 거동을 모사를 위해서 직접인발시험보다 휨 부재시험이 보다 유용한 것으로 사료된다.

• 대한치과보철학회지
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• 제45권6호
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• pp.805-814
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• 2007

Statement of problem. Composite resin-veneered metal restorations can be used as an alternative to porcelain-fused-metal restorations. But, because of the relatively low bond strength of veneering composite to metal framework, various surface treatment methods have been introduced to improve the bond strength. Purpose. The object of this study was to compare the shear bond strength of different combinations of each of the two bonding systems and each of the two composite veneering resins to cp-Ti/Co-Cr alloy. Material and methods. Two resin bonding systems (metal conditioner containing MEPS monomer, tribochemical silicoating system) and two composite resins (Gradia, Sinfony) were tested on cp-Ti and Co-Cr alloy. Then, according to manufacturers' instructions, resin bonding systems and composite resins were applied. All test specimens were divided into four groups for each alloy; I) sandblast + Metal Primer II + Gradia (MG), II) sandblast + Metal Primer II + Sinfony (MS), III) Rocatec + Gradia (RG), IV) Rocatec + Sinfony (RS). The shear bond strength was determined using a universal testing machine and all data were statistically analyzed with Mann-Whitney test and Kruskal-Wallis test at the significance level of 0.05. Results. The mean (standard deviations) of shear bond strength according to the combinations of two bonding systems and two composite resins to cp-Ti arranged from 16.44 MPa to 17.07 MPa and the shear bond strength to Co-Cr alloy ranged from 16.26 MPa to 17.70 MPa. The result shows that the difference were not statistically significant. Conclusion. The shear bond strengths of composite resins to both cast cp-Ti and Co-Cr alloy were not significantly different between the metal conditioner and the tribochemical silicoating system. And no differences in bond strength were found between cp-Ti and Co-Cr alloy.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.349-354
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• 2002

Significant improvements in bond strength between new and existing concrete can be achieved through the modification of the new concrete by latex modification. But, no test method has been adopted as a standard to measure the bond strength between the concrete used to repair and the substrate being repaired. The performance of old and the new concrete construction depends upon bond strength between old and the new concrete. Current adhesion strength measurement method ignores the effect of stress concentration by shape of specimens. Therefore, this research calculates stress concentration coefficient using finite element analysis and direction tensile strength test (pull-off test). The result shows that the required core depth is 2.5cm. Elastic modulus and overlay thickness do not influence in stress concentration.

• Structural Engineering and Mechanics
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• 제76권1호
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• pp.67-81
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• 2020

Pretensioned concrete (PC) is widely used in contemporary construction. Bond of prestressing strand is significant for composite-action between the strand and concrete in the transfer and flexural-bond zones of PC members. This study develops a new methodology for quantifying the bond of 18-mm prestressing strand in PC members based on results of a pullout test, the Standard Test for Strand Bond (STSB). The experimental program includes: (a) twenty-four pretensioned concrete beams, using a wide range of concrete compressive strength; and (b) twelve untensioned pullout specimens. By testing beams, the transfer length, flexural-bond length, and development length were all measured. In the STSB, the pullout forces for the strands were measured. Experimental results indicate a significant relationship between the bond of prestressing strand to the code-established design parameters, such as transfer length and development length. However, the code-predictions can be unconservative for the prestressing strands having a low STSB pullout force. Three simplified bond equations are proposed for the design applications of PC members.

• Structural Engineering and Mechanics
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• 제84권5호
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• pp.575-590
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• 2022

In this paper, bond-slip behavior of high strength concrete filled circular steel tube (HSCFCST) after elevated temperatures treatment was studied. 17 specimens were designed for push-out test. The influence was discussed as following parameters: (a) concrete strength, (b) constant temperature, and (c) bond length. The results showed that (1) after elevated temperatures treatment, the bond strength of the HSCFCST specimens increased first and then decreased with temperature rising; (2) the bond strength increased with the increase of concrete strength at room temperature, while the influence subsided after elevated temperatures treatment; (3) the strain of the circular steel tube was distributed exponentially along its length, the stress changed from exponential distribution to uniform distribution with the increase of load; (4) the bond damage process was postponed with the increase of constant temperature; and (5) the energy consumption capacity of the bonding interface increased with the rise of concrete strength and constant temperature. Moreover, computational formulas of ultimate and residual bond strength were obtained by regression, and the bond-slip constitutive models of HSCFCSTs after elevated temperatures was established.

• 한국콘텐츠학회논문지
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• 제15권9호
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• pp.384-394
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• 2015

본 연구에서는 원통형 지르코니아 코어에 다섯 종류의 지르코니아 비니어 세라믹을 축성하여 push-전단결합강도를 측정하고, 비니어 세라믹의 이축굽힘강도와 지르코니아 글라스 라이너 처리에 따른 전단결합강도 차이를 알아보고자 하였다. 지르코니아 비니어 세라믹은 piston-on-three-ball test로 이축굽힘강도를 측정하였고, 지르코니아 실린더 코어와 비니어 세라믹은 push-shear test로 결합강도를 측정하였으며, 결과값은 이원분산분석을 사용하여 분석하였다. 이축굽힘강도는 Cercon ceram kiss (CE)군에서 가장 높게 측정되었고 전단결합강도는 글라스 처리군과 Triceram(TR)군이 높게 측정 되었으며 Creation ZI(CR)군에서 가장 낮은 값이 측정 되었다. 실험군에서 지르코니아 라이너 처리군이 라이너 처리하지 않는 군보다 전단결합강도가 높게 나타났으며 통계적으로 유의한 차이를 보였다(P<0.05). 따라서 지르코니아 라이너 처리는 지르코니아와 비니어 세라믹의 결합강도를 향상시킬 수 있는 것으로 사료된다.

• 한국건설순환자원학회논문집
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• 제4권1호
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• pp.19-24
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• 2016

현재까지 하이볼륨 플라이애시 콘크리트의 연구는 슬럼프, 강도 및 내구성 등 기본적인 재 료성질에 대해서 주로 수행되어 왔다. 그러나 하이볼륨 플라이애시 콘크리트의 구조부재에의 적용을 위해서는 철근의 사용이 필수적이므로 그 부착특성에 대한 연구가 매우 중요하다고 할 수 있으나, 현재까지는 하이볼륨 플라이애시 콘크리트를 구조부재에 적용하기 위한 정확한 기준이나 콘크리트와 철근의 부착 특성에 관한 연구가 부족한 실정이다. 이 논문에서는 직접 인발 시험을 수행하여 하이볼륨 플라이애시 시멘트 콘크리트의 부착특성을 파악하고, 실험결과와 기존 연구결과를 비교하여 하이볼륨 플라이애시 시멘트 콘크리트의 부착특성을 평가하였다. 실험결과에 의하면, 하이볼륨 플라이애시 시멘트 콘크리트의 부착거동은 일반콘크리트와 유사하게 거동하는 것으로 나타났다. 또한 기존 연구결과와 비교하면, 하이볼륨 플라이애시 콘크리트의 부착강도는 묻힘길이가 클수록 부착강도를 과소평가하는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제21권1호
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• pp.15-22
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• 2017

본 논문은 바탕면의 함수조건에 따른 보수재료로서 MKPC의 인발 부착강도, 전단 부착강도, 계면 부착강도를 폴리머 시멘트 모르타르, 에폭시 모르타르와 비교 분석하였다. 그 결과 MKPC는 PC 및 MKPC와 비교하여 바탕면 함수조건에 따른 부착성능의 변화가 상대적으로 작은 것으로 나타났다. 또한 MKPC의 경우 절건 바탕면에서의 부착성능은 무기계 보수재료인 폴리머 시멘트 모르타르와 비교하여 우수한 특성을 지니고 있으며, 습윤 바탕면에서의 부착성능은 폴리머 시멘트 모르타르와 유사한 수준을 보이고 있으나 에폭시 모르타르와 비교하여 우수한 특성을 지니는 것으로 나타났다.