• Tunnel and Underground Space
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• v.29 no.2
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• pp.124-134
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• 2019

Subcritical crack growth in rock material can occur under monotonic and cyclic loading. Subcritical crack growth plays an important role in evaluating the long-term stability of structures in rocks. This paper presents the results of studies conducted to determine subcritical crack growth parameters under monotonic and cyclic loading in rock-like material. The constant stress rate method was employed for monotonic loading. The subcritical crack growth parameter of n under cyclic loading was determined by the relation between the rate of crack growth per cycle and stress intensity factor range. The specimens contained pre-existing flaws with 45 and 60 degrees of inclination angle and flaws spacing and continuity were varied to arrange crack growth in shear or tensile manner. The results show that the parameter of n is almost constant regardless of the applied load conditions such as monotonic and cyclic or shear and tension.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.721-730
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• 1998

In this paper, an experimental study have been many studies on the joints of steel structure, for it has great influences on the safety of structures. Research on block shear rupture of the joint receiving pure tension have been done in foreign countries, but not in Korea. This study focuses on the propriety of block shear design code, according to limited state design criteria of steel structures recently established in Korea, by an experiment on the joint of angle tension members. The methods of this study were to compare other study results on block shear rupture mode and ultimate capacity, and to evaluate the propriety of the criteria design code. The result is that tension yield shear ruptures and shear yield tension ruptures happened at the joint, and the experimental rupture load was 15% higher than the capacity entered in the criteria design code. We conclude that it is necessary to revaluate the block shear design code presented by many studies on the limited state design criteria of steel structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.4
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• pp.353-367
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• 2003

This paper describes the extension of the numerical model, which was developed to simulate the nonlinear behavior of reinforced concrete (RC) structures subjected to monotonic in plane shear and introduced in the companion paper, to simulate effectively the behavior of RE structures under cyclic loadings. While maintaining all the basic assumptions adopted in defining the constitutive relations of concrete under monotonic loadings, a hysteretic stress strain relation of concrete, which across the tension compression region, is defined. In addition, unlike previous simplified stress strain relations, curved unloading and reloading branches inferred from the stress strain relation of steel considering the Bauschinger effect we used. The modifications of the stress strain relation of steel are also introduced to reflect pinching effect depending on the shear span ratio and an average stress distribution in a cracked RC element. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.3
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• pp.293-308
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• 1999

이 논문에서는 패널, 깊은 보 그리고 전단벽과 같이 평면응력상태하에 있는 철근콘크리트 구조물의 비선형 유한요소해석에 있어서의 직교이방성 콘크리트 구성 모델의 적용성을 보여준다. 등가의 일축 변형을 개념을 토대로 콘크리트의 구성 관계가 주변형률 축과 일치하고 하중이력에 따라 회전하는 직교하는 축에 대해 제시된다. 제안된 모델은 이축 압축응력상태와 인장-압축 응력상태에서 각각 압축강도의 증가와 인장 저항력의 감소효과를 보여주는 이축 파괴영역의 정의를 포함한다. 인장균열이 발생한 후, 콘크리트의 압축강도의 감소효과가 제시되고, 인장강화효과로 알려진 철근에 의해 지지되는 콘크리트의 인장응력이 고려된다. 평균응력과 평균변형률 개념을 사용하여 힘의 평형, 적합조건 그리고 철근과 철근을 둘러싼 콘크리트 사이의 부착응력-슬림 관계를 토대로 인장강화효과를 모사하기 위한 모델이 제안된다. 유한요소 모델에 의한 예측은 유용한 실험자료와의 비교에 의해 입증된다. 이 논문에서는 해석결과와 이상화한 전단 패널실험으로부터 얻어진 실험값의 비교연구가 수행되고, 제안된 모델의 타당성을 보여주기 위해 서로 다른 응력상태하의 전단 패널 보와 벽체의 힘-변위 관계를 평가하였다.

• Composites Research
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• v.18 no.2
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• pp.13-19
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• 2005

In this paper deformation of micro-mechanical parameters such as tow interval, tow thickness and change in tow amplitude are investigated by using dry fabrics (Five-harness satin weave) under shear deformation. To evaluate the observation results according to the generated in-plane forces in the material, bias extension, biaxial test results are compared with. It was found that a picture frame test with a misaligned fibre orientation angle shows large differences in deformation between tensile and compressive tow directions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.303-309
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• 2011

Laminated rubber bearing is the most commonly used device for seismic base isolation of bridge structures. It is important to know performance and behavior characteristics of the laminated rubber bearings. The main evaluation factors of the rubber bearing are classified as compressive, shear and tensile behavior characteristics. The reference data of compressive and shear characteristics are rich, but the reference data of tensile characteristics is scarce. In this study, tensile test results of the rubber bearing with variation of shape factor and shear deformation are investigated for mechanical property. When tensile deformation in normal condition is increasing, tensile cycle behavior curve becomes non-linear and tensile breaking point is 300%. On the other hand, tensile breaking point is shear deformation condition is about 40%. Furthermore, when shape factor is lower, tensile breaking point is decrease. This results mean that tensile breaking point is decreased in triaxial tensile deformation because of cracks caused by internal void of the rubber bearings. This experimental data can be used as the reference data of tensile characteristics for designing seismic isolation of structures.

• Magazine of the Korea Concrete Institute
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• v.9 no.5
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• pp.225-231
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• 1997

콘크리트 압축강도 및 전단스팬비의 변화에 의한 고강도 철근콘크리트 춤이 큰 보의 전단거동 및 내력특성을 파악하기 위한 실험적 연구를 하였다. 춤이 큰 보는 하중작용점과 하중지지점을 연결하는 사균열의 확대에 의해 취성전단파괴양상을 나타내었으며 하중작용점 하중 지지점의 콘크리트 압괴를동반하는 전단압축 및 전단인장파괴 형태로 최종파괴되었다. 전단스팬비가 감소함에 따라 사균열전단응력 및 최대전단응력은 크게 증가하였으며, ACI 및 CIRIA규준식은 부재의 최대전단응력을 비교적 정확하게 예측하고 있음을 파악하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.487-490
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• 2004

In this paper, we investigated the characteristics of initiation and propagation behavior for fatigue crack observed by changing various shapes of initial crack and magnitudes of loading in modified compact tension shear(CTS) specimen subjected to shear loading. In the low-loading condition, the secondary fatigue crack was created in the notch root due to friction on the pre-crack face grew to a main crack. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Influenced by the shear loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. The propagation path of fatigue crack under the Mode II loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

• Composites Research
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• v.17 no.1
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• pp.38-46
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• 2004

This paper aims to correlate the micro-mechanical behaviour of tow geometry with applied in-plane forces during deformation of dry woven carbon-fibre fabric. These in-plane forces lead to differences in tow reorganisation during deformation and so changes in the way in which 'lock-up' occurs. In this paper, deformation of micro-mechanical parameters such as tow interval, crimp angle, change in tow amplitude and wavelength are investigated. To observe the micro-deformation of the fabric structure, appropriate specimens from bias extension and biaxial tests are sectioned and observed under the microscope. It was found that different loading conditions cause geometric deferences in the tow architecture. The variation in deformed tow geometry with shear angle is fitted using a simple parametric model.

• Journal of the Korean Ceramic Society
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• v.28 no.1
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• pp.19-19
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• 1991

Fracture of Al2O3 tubes for different loading path under combined tension/torsion was investigated. Macroscopic directions of crack propagation agreed well with the maximum principal stress criterion, independent of the loading path. However, fracture strength from the proportional loading test(τ/σ= constant) showed either strengthening or weakening compared to that from uniaxial tension, depending on the ratio τ/σ. The Weibull theory was capable to predict the strengthening of fracture strength in pure torsion, but not the weakening in the proportional loading condition. The strengthening or weakening of fracture strength in the proportional loading condition was explained by the effect of shear stresses in the plane of randomly oriented microdefects. Finally, a new empirical fracture criterion was proposed. This criterion is based on a mixed mode fracture criterion and experimental data for fracture of Al2O3 tubes under combined tension/torsion. The proposed fracture criterion agreed well with experimental data for both macroscopic directions of crack propagation and fracture strengths.