• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.281-290
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• 2009

In this study, an analysis technique of hybrid girder considering nonlinearity of steel-concrete contact surface is presented. Steel-concrete hybrid girder shows partial-interaction behavior due to the deformation of shear connectors, slip and detachment at the interface, and cracks under the applied loads. Therefore, the partial-interaction approach becomes more reasonable. Contact surface is modeled by interface element and analyzed nonlinearly because of cost of time and effort to detailed model and analysis. Steel and Concrete are modeled considering non-linearity of materials. Material property of contact surface is obtained from push-out test and input to interface element. For the constitutive models, Drucker-Prager and smeared cracking model are used for concrete in compression and tension, respectively, and a von-Mises model is used for steel. This analysis technique is verified by comparing it with test results. Using verified analysis technique, various analyses are performed with different parameters such as nonlinear material property of interface element and prestress. The results are compared with linear analysis result and analysis result with the assumption of full-interaction.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1995.04a
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• pp.93.2-93
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• 1995

후두 및 기관지 협착증은 대개가 기도확보를 목적으로 후두 및 기관내에 삽관을 시행하였을 때 삽관튜브에 부착된 cuff내에 압력이 높게 되면 점막에 혈류장애가 초래되고 궤양등의 점막손상이 뒤따르며 여기에 2차감염이 초래되어 육아종과 반흔이 생기면서 결국은 협착이 초래되는 것으로 알려져 있다. 이와 같이 손상된 후두및 기관의 점막에 산도가 강하고 소화효소가 함유된 위액이 역류되어 접촉될 경우 협착이 더욱 조장되리라고 가정할 수 있다. 따라서 위액이 과연 후두 및 기관지 협착증에 관여 한 것인지를 실험적으로 규명해 보고자 하였다. 실험동물은 가토를 대상으로 하여 Urethan마취를 시행하고, 삽관한 다음 합성위액 pH 1.5, 3, 5 짜리 용액을 기관 내에 1시간정도 관류시킨 다음 후두 및 기관을 적출하여 점막상태의 변화를 현미경으로 관찰하였다. 그 결과 산도가 강하고 펩신이 첨가된 합성위액으로 관류한 군에서는 성모의 파괴점막의 궤양, 부종과 염증소견 등이 심하게 관찰되었다. 그러나 산도가 약할수록, 그리고 펩신이 첨가되지 않은 합성위액으로 관류한 군에서는 섬모 및 점막의 손상이나 염증 및 부종등의 소견이 경미하게 관찰되었다. 이러한 결과로 미루어 강한 산도의 위액이 후두 및 기관으로 역류될 경우 협착증의 발생에 깊이 관여하리라고 추측되었다.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.67-79
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• 2008

In this study, a bending test with three encased composite beams were carried out and analyzed using FEM in order to find how chemical adhesion, interface interlock, friction and composite action by shear studs contribute to stiffness, strength and composite action in the interface of encased compo site beams. The test and results of the FEM analysis showed that the difference in the ultimate moment capacity of the composite beams with and without studs is under 10%. The reason is that the effect of chemical adhesion, interface interlock, and friction in the interface on the composite action is so high that the encased beams have a moment capacity above some defined magnitude. Also, the increment of moment capacity up to plastic moment is not large and the increase of linearly proportioned.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.725-735
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• 2007

The local buckling strength and post-local buckling strength of thin steel plates in the steel-concrete composite column were evaluated by nonlinear finite element analyses. The proposed width-to-thickness limit ratio was based on elastic buckling analyses, in which the increased local buckling capacity of the plate due to the in-filled concrete was considered by the boundary conditions of the thin plate. Considering the initial imperfections and residual stresses, we determined the initial local buckling strength and post-local buckling strength of the thin plates with various width-to-thickness ratios. The formula to evaluate the compressive capacity of the steel-concrete composite column based on the effective width of the plate was proposed. For verification, values determined by the formula were compared with the experimental results.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.59-65
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• 2016

Commercial synthetic resins with great amount of hydrogen atoms were investigated for neutron shielding aggregates. Total three types of resins were considered in this study: high density polyethylene (HDPE), polypropylene (PP), and ultra molecular weight polyethylene (UPE). When these resins replaced 20, 40, 60 vol% of fine aggregates, mechanical properties were first evaluated including compressive and tensile strengths, and then image/microstructure analyses such as cross-section analysis, SEM, and X-ray CT were performed. The results showed that the compressive and tensile strengths decreased with the increase of replacement ratio of HDPE and PP, which was found through image analysis that it was closely related to the distribution of resins at the failure surface of test specimens. The strength reduction of UPE was quite small compared to HDPE and PP but it abruptly increased when the replacement level exceeded 60 vol%. The results of microstructure analyses indicated that the replacement level significantly affected the amount of air void so that it is critical to determine the reasonable amount of UPE to make cementitous materials for neutron shielding.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.433-452
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• 2019

This study deals with shotcrete reinforcing performance according to the amount of synthetic fiber (PP fiber) and proper evaluation method. The shotcrete compressive strength, flexural strength and flexural toughness were tested by setting the mixing amounts of steel fiber ($37.0kg/m^3$) and synthetic fiber (PP fiber) as parameters ($5.0kg/m^3$, $7.0kg/m^3$ and $9.0kg/m^3$). Particularly, circular panel flexural toughness test (Road and Traffic Authority, RTA) was performed to evaluate the shotcrete energy absorption capacity. As a result, the compressive strength and the bending strength of the steel fiber reinforced shotcrete were large, but the flexural toughness of the synthetic fibe (PP fiber) reinforced shotcrete was large. Therefore, synthetic fiber (PP fiber) reinforced shotcrete is considered to have a reinforcing effect comparable to that of steel fiber reinforced shotcrete. Analysis of the relationship between the flexural toughness and the energy absorption capacity of synthetic fiber (PP fiber) reinforced shotcrete revealed that the energy absorbing ability is exhibited at a flexural toughness lower than the allowable standard (3.0 MPa). (Class A: 2.55 MPa = 202J, Class B: 2.72 MPa = 282J, Class C: 3.07 MPa = 403J). As a result of this study, it can be concluded that the actual shotcrete support performance can be evaluated by evaluating the support performance of the shotcrete measured at less than the allowable standard (3.0 MPa) at the actual tunnel site.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.423-431
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• 2013

The k-factor method has been widely used in design of steel-concrete composite bridges to determine indeterminate stresses. The accuracy of k-factor method is examined by a comparative analysis with the equivalent load method in a continuous 2-span composite bridge. To improve the accuracy, the direction of creep stress has to be modified and the variety of section must be considered. This paper suggests j-factor method which can improve the accuracy of k-factor method with simple modification.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.241-244
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• 2005

• Proceedings of the Korean Nuclear Society Conference
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• 1998.10a
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• pp.113-113
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• 1998

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.134-135
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• 1993