• 한국재료학회지
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• 제5권2호
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• pp.191-196
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• 1995

비정질 PEEK 필름의 self-bonding강도는 접합시의 공정변수(시간, 온도, 그리고 압력)와 밀접한 관계가 있다. 본 연구에서는 이러한 공정변수의 효과를 규명하기 위하여 각기 다른 접합조건하에서 개발된 시편들의 self-bonding강도를 single lap-shear test를 통하여 측정된 각각의 전단 응력(shear strength)으로 나타내었다. 개발된 self-bonding강도는 접합온도가 증가함에 따라 증가하였으며, 접합시간의 1/4승에 일차함수적으로 비례증가하였다. 접합공정 중의 압력의 효과는 단지 초기 접합단계인 wetting에 기여하였을 뿐 self-bonding강도 자체에는 거의 영향을 미치지 않는 것으로 사려되었다. 결론적으로 비정질 PEEK 필름의 self-bonding현상은 현장에서의 실제 접합공정에서 어떠한 접착재료의 사용없이도 모재와 같은 강도를 개발하는데 무한한 가능성이 있는 것으로 판단되었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.845-850
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• 2007

The empirical AISC panel zone thickness provision$(t_z\geq(d_z+w_z)$/90) to prevent the cyclic shear buckling of the panel zone was proposed based on the test data of Krawinkler et al. (1971) and Bertero et al. (1973) However, no published records of the equation development or any other background information appear to be available. The calibrated finite element analysis results of this study indicated that the AISC provision was not reasonable. In this study, through including the effects of the column axial force and the aspect ratio of the panel zone, a new equation for the relative strength between the beam and the panel zone was proposed such that the proposed equation can prevent the panel zone shear buckling and reduce the potential fracture associated with the kinking of the column flanges.

• Computers and Concrete
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• 제29권 5호
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• pp.285-301
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• 2022

This study aims at developing a torsional strength model based on a nonlinear analysis method presented in the previous studies. To this end, flexural neutral axis depth of a reinforced concrete section and effective thickness of an idealized thin-walled tube were formulated based on reasonable approximations. In addition, various sectional force components, such as shear, flexure, axial compression, and torsional moment, were considered in estimating torsional strength by addressing a simple and linear strain profile. Existing test results were collected from literature for verifications by comparing with those estimated from the proposed model. On this basis, it can be confirmed that the proposed model can evaluate the torsional strength of RC members subjected to combined loads with a good level of accuracy, and it also well captured inter-related mechanisms between shear, bending moment, axial compression, and torsion.

• Elastomers and Composites
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• 제54권4호
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• pp.335-344
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• 2019

In this work, styrene butadiene rubber (SBR) and styrene butadiene styrene (SBS) were used to modify asphalt, resulting in SBR- and SBS-modified asphalt, respectively. The two modified asphalts were emulsified with a nonionic emulsifier (Span 60) and cationic emulsifiers (ID, DDA) and their phase stabilization was investigated via particle size, Zeta potential, and flow behavior analysis. With increasing amount of the mixed emulsifier, the particle size decreased, leading to an increase in viscosity. The shear thinning behaviors and Zeta potential values ranging from 35-65 mV were determined and remained considerably stable. In addition, the adhesion strength and compression strength of the SBR-and SBS-modified asphalt emulsion were evaluated via surface free energy examination. The remarkable adhesion and compression strengths were estimated when 5 phr ID and 6 phr DDA were added to the emulsified asphalt modified with SBR and SBS. Therefore ID and DDA, the two cationic surfactants, played significant roles in improving the dispersion and interfacial adhesion strength, resulting in the improved adhesion and compression strength of the emulsified asphalts modified with SBR and SBS.

• Geomechanics and Engineering
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• 제17권1호
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• pp.31-45
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• 2019

In this study the spatial variability of soils is substantiated physically and numerically by using random field theory. Heterogeneous samples are fabricated by combining nine homogeneous soil clusters that are assumed to be elements of an adopted random field. Homogeneous soils are prepared by mixing different percentages of kaolin and bentonite at water contents equivalent to their respective liquid limits. Comprehensive characteristic laboratory tests were carried out before embarking on direct shear experiments to deduce the basic correlations and properties of nine homogeneous soil clusters that serve to reconstitute the heterogeneous samples. The tests consist of Atterberg limits, and Oedometric and unconfined compression tests. The undrained shear strength of nine soil clusters were measured by the unconfined compression test data, and then correlations were made between the water content and the strength and stiffness of soil samples with different consistency limits. The direct shear strength of heterogeneous samples of different stochastic properties was then evaluated by physical and numerical modelling using FISH code programming in finite difference software of $FLAC^{3D}$. The results of the experimental and stochastic numerical analyses were then compared. The deviation of numerical simulations from direct shear load-displacement profiles taken from different sources were discussed, potential sources of error was introduced and elaborated. This study was primarily to explain the mathematical and physical procedures of sample preparation in stochastic soil mechanics. It can be extended to different problems and applications in geotechnical engineering discipline to take in to account the variability of strength and deformation parameters.

• Geomechanics and Engineering
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• 제37권4호
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• pp.419-429
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• 2024

The primary goal was to assess how the addition of cement dust, a byproduct known to be harmful, could be used to stabilize clay. Various percentages of cement dust were added to soil samples, which were then subjected to triaxial testing at different rates of strain using an unconsolidated undrained triaxial machine. Six different rates of strain were applied to analyze the response of the clay under different conditions, resulting in 216 triaxial sample tests. As the percentage of cement dust in the clay samples increased, there was a noticeable increase in the strength properties of the clay, indicating a positive effect of cement dust on the clay's strength characteristics. Higher rates of strain during testing led to increased strength properties of the clay. Varying cement dust content influenced the impact of increasing the rate of strain on the clay's strength properties. Higher cement dust content reduced the sensitivity of the clay to changes in strain rate, indicating that the clay became less responsive to changes in strain rate as cement dust content increased. Potential for Clay Stabilization Cement dust proved the potential to enhance the strength properties of clay, indicating its potential utility in clay stabilization applications. Both higher percentages of cement dust and higher rates of strain were found to increase the clay's strength. It's essential to consider both the percentage of cement dust and the rate of strain when assessing the strength properties of clay in practical applications.

• Steel and Composite Structures
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• 제36권3호
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• pp.321-337
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• 2020

Contemporary design and construction of steel-concrete composite structures employs the use of prefabricated concrete elements and demountable shear connectors in order to reduce the construction time and costs and enable dismantling of elements for their potential reuse at the end of life of buildings. Bolted shear connector with mechanical coupler is presented in this paper. The connector is assembled from mechanical coupler and rebar anchor, embedded in concrete, and steel bolt, used for connecting steel to concrete members. The behaviour and ultimate resistance of bolted connector with mechanical coupler in wide and narrow members were analysed based on push-out tests and FE analyses conducted in Abaqus software, with focus on concrete edge breakout and bolt shear failure modes. The effect of concrete strength, concrete edge distance and diameter and strength of bolts on failure modes and shear resistance was analysed. It was demonstrated that premature failure by breakout of concrete edge occurs when connectors are located 100 mm or closer from the edge in low-strength and normal-strength reinforced concrete. Furthermore, the paper presents a relatively simple model for hand calculation of concrete edge breakout resistance when bolted connectors with mechanical coupler are used. The model is based on the modification of prediction model used for cast-in and post-installed anchors loaded parallel to the edge, by implementing equivalent influence length of connector with variable diameter. Good agreement with test and FE results was obtained, thus confirming the validity of the proposed method.

• 한국지반환경공학회 논문집
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• 제8권4호
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• pp.57-65
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• 2007

토목구조물의 안정성에 영향을 미치는 인자 중 지진에 의한 피해를 들 수가 있다. 최근의 지진 피해 사례를 분석하여 보면 모래와 같은 조립토뿐만 아니라 점성토, 실트 등과 같은 세립토에서도 크고 작은 피해 사례가 보고되고 있다. 이에 본 연구에서는 지진에 의한 기초지반의 강도저하를 평가하는 방법을 조사하기 위하여, 반복단순전단시험기를 이용하여 비배수상태에서 조립토 및 세립토에 반복하중을 작용시켜 지반의 강도저하특성을 조사하고 조립토의 경우에는 여유간극비, 세립토의 경우에는 소성지수를 이용하여 간단한 평가방법을 제안하였다. 분석결과에 따르면 액상화강도를 비교 분석하여 보면 조립토에서는 여유간극비의 증가에 따라 감소하고, 세립토의 경우에는 소성지수가 증가함에 따라 커지는 것을 알았다. 특히, 화강풍화토는 Collapse현상이 발생하여 다른 흙보다 현저한 강도 감소 경향이 나타났다. 간이강도저하 평가방법을 통해서 조립토와 세립토 거의 대부분이 양대수곡선상에서 -0.15 ~ -0.2의 범위내의 비슷한 기울기 내에서 분포하였지만, 화강풍화토와 같은 흙은 강도저하 경향이 -0.3으로 다른 흙보다 크게 나타남을 알 수 있었다. 본 강도저하 평가방법은 추가 연구가 필요하지만, 실무에서 간단하게 적용 가능할 것으로 보인다.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.2234-2241
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• 2015

본 연구에서는 국내 지반의 전단강도정수와 콘지수 사이의 상관관계를 확립하기 위하여 먼저 콘관입 모델을 통한 이론적 상관관계를 정리하고 이의 신뢰도를 높이기 위하여 인공신경망 기법을 적용하였다. 이론적 상관관계는 이론식을 유도하면서 적용한 가정들로 인하여 신뢰성 있는 지반의 거동을 예측하기 어려운 측면이 있다. 따라서 인공신경망 기법을 적용하여 이론적, 경험적 방법과 같은 기존의 방법과는 다른 새로운 측면에서 지반의 거동 특성을 파악할 필요성이 있다. 인경신경망 모델은 국내의 다양한 건설현장에서 수행한 지반조사 보고서를 통해서 입력자료를 확보한 뒤에 모델학습을 수행하였다. 연구결과 측정값과 예측값의 오차가 크지 않았고, 비교적 고르게 분포함을 알 수 있었다. 추후 보강된 인공신경망 모델을 구축하면 국내 특정 지역뿐만 아니라 일반화된 지역에 보편적으로 적용할 수 있을 것으로 기대된다.

• 한국지반공학회논문집
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• 제16권1호
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• pp.75-81
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• 2000

일반적으로 자연상태의 흙은 이방성을 나타내며, 이러한 흙의 이방성이 응력-변형률 거동에 미치는 영향은 매우 크다. 따라서 본 연구에서는 인공신경회로망 모델을 이용하여 압밀응력비 변화에 따른 정규압밀점토의 응력-변형률 거동을 모델링하고 비배수전단강도를 예측하여 보았다. 이때 사용된 신경회로망은 일반화된 델타규칙으로도 불리우는 오차역전파 학습 알고리즘을 이용한 다층신경회로망이다. 신경회로망의 학습은 인공퇴적 점토시료를 이용, 연직압밀응력과 압밀응력비를 다르게 정규압밀시킨후 비배수전단시험을 실시하여 얻어진 시험 결과를 이용하였고, 학습된 신경회로망을 이용하여 학습시 제외되었던 압밀응력비 상태에서의 비배수전단강도를 추론하여 본 결과 예측치와 실측치가 잘 일치하였다. 검토결과 실측치와 추론치 사이에는 결정계수($r^2$) 0.973 이상의 높은 상관관계가 있음을 확인하였다. 따라서, 본 연구결과는 점토의 비배수전단강도를 예측함에 있어서 인공신경회로망모델의 적용 가능성을 보여주었다.