• Proceedings of the Korean Fiber Society Conference
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• 2003.10b
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• pp.155-156
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• 2003

시멘트는 압축강도가 크고 내구성이 좋으며 가격이 저렴한 우수한 토목건축재료이다. 그러나 인장강도가 낮아서 사용 시 발생하는 휨에 의한 인장변형에 의하거나 양생 후 해 표면 크랙이 발생하는 결점이 있다. 이러한 결점을 보완하기위해 크랙의 발생 억제, 성장 지연을 목적으로 시멘트에 보강용 섬유를 투입하고 있다[1]. 시멘트에서의 보강섬유의 역할은 크랙발생에 필요한 에너지를 최대한 증가시키켜 시멘트가 경화되기 시작할 때, 구속에 의해 발생하는 인장응력 및 균열을 억제하구 내부에 형성되는 결함을 방지함에 있다[2]. (중략)

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.33-42
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• 2004

Making use of SN steel in the building structure should be a prerequisite to adopt the design strength of said steel. As a preceding study, the material properties of STKN400B/490B tubes and SPAP235/325 and SPAR295 square pipes manufactured using SN400B/490B plates were evaluated. Compared with the yield and ultimate strengths of SN400B/490B plates, those of STKN400B/490B tubes increase. Nonetheless, the yield and ultimate strengths of STKN400B/490B tubes satisfied the design codes of STKN400B/490B tubes even though the tubes were fabricated via roll bending or press forming. On the other hand, the yield and ultimate strengths at the edges of SPAP235/325 square pipes did not satisfy the design codes based on the values at the sides. The maximum tensile and compressive residual stresses at the SN490B tube were equal to and 40% of the yield strength of the SN490B plate, respectively, In the case of the SPAP325 square pipe, both the maximum tensile and compressive residual stresses were 80% of the yield strength of the SN490B plate. The axial compressive loaded column test results snowed that the buckling strengths were not very different regardless of the mode of fabrication of STKN490B tunes. i.e., through roll bending or press forming. On the other hand, the buckling strength of the SPAP325 square pipe was higher than that of the built-up square pipe.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.141-146
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• 1995

In this study the plastic buckling analysis of a simply supported plate under biaxial compression/tension loading is carried out considering the plastic compressibility. Plastic buckling of a biaxially loaded rectangular plate is governed by two kinds of mechanism, the tension strengthening and plastic weakening under which the optimal combination of tension and compression is obtained for the buckling strength. To consider the plastic compressibility, the Drucker-Prayer plastic potential is employed. General eigenvalue equations are derived for a rectangular plate within the framework of small strain plasticity and isotropic hardening.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.469-472
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• 2008

As a general rule, concrete has higher compression strength than bending and toughness. but Ductile fiber reinforced cementitious composite has high toughness property owing to adding a large volume fiber. Therefore uniaxial tensile strength test is imperative to evaluate high toughness property of ductile fiber reinforced cementitious composite in comparison with general concrete test. but in testing compression strength, Result is different by factor of thickness, shape and edge condition. Uniaxial tensile strength test is affected by fiber's length and section area because of cementitious composite property and factor of fiber arrangement. This study evaluates toughness property of ductile fiber reinforced cementitious composite according to thickness and edge condition. The more thickness is thin, the more high performance by fiber arrangement

• Explosives and Blasting
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• v.21 no.4
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• pp.23-35
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• 2003

This study is to clarify the comparative relationship and a mechanical anisotropy of rock on the subject of granite distributed in the Namwon area Uniaxial compressive and Brazilian strengths with respect to the horizontal and vertical axes of granite are shown the linear relation. In the case of the result of the p-wave velocity measurement. it is represented that the velocity of vortical direction is faster about 10 to 15% than other two horizontal directions. The difference between velocities is caused by a developmental pattern of microcracks distributed in rock. Moreover, this result is very consistent with the result investigated through thin sections. The proportion of uniaxial compression strength to Index of point load strength ($Is_{(50)}$) is 18~20 times in case of granite. Uniaxial compressive strength is relatively good relationship with point load strength, Schmidt hammer rebound value, and tensile strength point load strength of them is the best comparative relationship. It is indicated that point load test is the most useful tool to estimate uniaxial compressive strength, comparing with other experimental methods.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.450-462
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• 2009

To analyze the behavioral characteristics of rocks on indirect tests and uniaxial compressive strength, researchers have investigated 1417 pieces of rock block, which include igneous, metamorphic and sedimentary rocks in Korea. The same behavioral characteristics have been shown in every type of sedimentary rock and in the same species of rock in the case of Brazilian strength application. This suggests that correlations of rocks for geological considerations can lead to high reliability of the experimental results in case of an indirect method.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.655-664
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• 2007

The inherent characteristic of concrete tensile cracks, directional nonlocal crack damage, causes so-called rotating tensile crack damage and softening of compressive strength. In the present study, a plasticity model was developed to describe the behavior of reinforced concrete planar members In tension-compression. To describe the effect of directional nonlocal crack damage, the concept of microplane model was combined with the plasticity model. Unlike existing models, in the proposed model, softening of compressive strength as well as the tensile crack damage were defined by the directional nonlocal crack damage. Once a tensile cracking occurs, the microplanes of concrete are affected by the nonlocal crack damage. In the microplanes, microscopic tension and compression failure surfaces are calculated. By integrating the microscopic failure surfaces, the macroscopic failure surface is calculated. The proposed model was implemented to finite element analysis, and it was verified by comparisons with the results of existing shear panel tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.178-184
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• 2017

This study was aimed to investigate the tensile behaviors of PE(Polyethylene) fiber-reinforced highly ductile cementitious composites with different combinations of micro silica sand and normal sand(river sand) with maximum particle size of 4.75 mm. Flow test result indicated the increase of flowability with higher replacement ratio of river sand. There was no noticeable difference in the mean compressive strength with different replacement ratio of river sand, but the variation in the compressive strength increased as higher amount of river sand was adopted for the replacement. The difference in the uniaxial tensile strength was negligible, but the tensile strain capacity was significantly influenced by the replacement ratio of river sand. It is thought that increased density of multiple cracks induced improved tensile strain capacity when higher percentage of river sand was adopted for fine aggregate. The deviation in the strain capacity increased as the replacement ratio of river sand was higher, as in the compressive strength. This study presented the feasibility of using normal sand instead of micro silica sand for highly ductile cementitious composites with equivalent or better uniaxial tensile performance, even though it might increase the deviation in the performance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.2
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• pp.177-182
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• 2020

In this study, the effect of nanofibers in cement pastes on the compressive and tensile strength of hardened cement pastes was studied. Two types of nanofibers, nylon 66 nanofibers and carbon nanotube-nylon 66 hybrid nanofibers, were manufactured by electrospinning methodology and mixed in cement powder respectively. The specimens for experiments were prepared by water to cement ratio of 0.5 and cured in water for 28 days. The effect of nanofibers on the increase of the compressive and tensile strength were confirmed by the experimental results. The well-linking effect of nanofibers in the microstructure of the hardened cement pastes has been found by scanning electron microscope (SEM) analysis and well-explained for the increase in mechanical strength. Besides, field emission transmission electron microscope (FE-TEM) analysis and thermal gravimetric analysis (TGA) have also been conducted to analyze the properties of nanofibers as well as the microstructure of the hardened modified cement pastes.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.316-322
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• 2019

A probabilistic approach considering uncertainties was employed to investigate the effects on the material characteristics and strength of nuclear bio-logical shield concrete walls, when exposed to long-term radiation during the entire service life. Time-dependent compressive and tensile strengths were estimated by conducting the neutron fluence analysis. For the contaminated concrete, individual compressive and tensile failure probabilities can be possibly evaluated by not only establishing limit-state function withthe predefined critical values but also performing Monte Carlo Simulation. Nuclear power plant types similar to the Kori Unit 1, which was shut off permanently in 2017 after the 40-year operation, were herein selected for an illustrative purpose. Consequently, the probability-based performance assessment and prediction of contaminated concrete walls were well demonstrated.