• 한국강구조학회 논문집
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• 제25권5호
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• pp.463-474
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• 2013

일면전단 오스테나이트계 스테인리스강 및 탄소강에 관한 많은 실험 및 해석적 연구가 수행되어졌고, 수정된 내력평가식이 제안되었다. 본 연구에서는 볼트배열(2행 1열, 2행 2열)과 하중방향 연단거리를 주요변수로 하여 이면전단 볼트접합부 실험체가 제작되었고, 단순인장실험이 실시되었다. 고정변수로는 하중직각방향 연단거리, 볼트직경, 피치, 게이지를 설정하였다. 최대내력과 파단형태와 같은 실험결과와 현행기준식에 의한 예측결과와 비교 검토되었다. 볼트배열에 따른 블록전단내력평가식이 제안되었다.

• Steel and Composite Structures
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• 제22권5호
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• pp.1019-1038
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• 2016

The use of high-strength concrete (HSC) in precast concrete segmental bridges (PCSBs) can minimize the superstructure geometry and reduce beam weight, which can accelerate the construction speed. Dry joints between the segments in PCSBs introduce discontinuity and require special attention in design and construction. Cracks in dry joints initiate more easily than those in epoxy joints in construction period or in service. Due to the higher rupture strength of HSC, the higher cracking resistance can be achieved. In this study, shear behavior of dry joints in PCSBs was investigated by experiments, especially focusing on cracking resistance and shear strength of HSC dry joints. It can be concluded that the use of HSC can improve the cracking resistance, shear strength, and ductility of monolithic, single-keyed and three-keyed specimens. The experimental results obtained from tests were compared with the AASHTO 2003 design provisions. The AASHTO 2003 provision underestimates the shear capacity of single-keyed dry joint C50 and C70 HSC specimens, underestimates the shear strength of three-keyed dry joint C70 HSC specimens, and overestimates the shear capacity of three-keyed dry joint C50 HSC specimens.

• Composites Research
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• 제33권4호
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• pp.228-233
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• 2020

본 논문은 유리섬유강화 복합재료(GFRC)를 사용하여 단일 랩 전단 시험을 진행하고, 단일 랩 전단 시험을 진행하면서 연필심을 이용한 종이센서(PLDPS)를 적용하였다. 복합재료의 접착은 비스페놀-A계 에폭시와 아민계 경화제를 혼합하여 접착제로 사용하였다. 접착물성의 차이를 주기 위해 각기 다른 조건에서 경화시켰고 물성이 달라진 것을 확인하였다. 연필심을 이용한 종이센서는 A4용지에 4B연필을 사용하여 제작하였다. 연필에 있는 흑연은 전기가 통하는 물질이므로 전기저항을 측정할 수 있다. 연필심을 이용한 종이센서에 단일 랩 전단 시편에 붙은 위치에 따라 전기저항의 변화를 관찰하였고, 붙이는 두 위치에 따라 전기저항의 변화가 다르게 나오는 것을 확인하였다. 또한, 랩 전단변형률에 따라서 전기 저항의 변화도 관찰하였다. 랩 전단변형률이 높으면 전기 저항 변화도 큰 것을 확인했다. 접착부분의 변형이 클수록 시편이 휘는 정도도 커져 전극 사이의 거리변화도 크게 만들기 때문이다.

• Journal of the Korean Wood Science and Technology
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• 제35권4호
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• pp.38-44
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• 2007

환경문제의 대두에 따라 포름알데히드를 방산하는 접착제를 대신할 수 있도록 로진을 이용한 천연접착제를 개발하고자 한다. 경화속도와 접착물성을 향상시키기 위해 건조제의 배합에 따라 천연접착제를 제조하였다. 건조제의 배합에 따른 경화속도와 접착물성을 Texture Analyzer를 이용하여 얻어진 tack값과 single lap shear test를 통해 얻어진 접착력을 기반으로 평가하였으며, 외국에서 사용되고 있는 AURO, BioFa, Livos의 식물계 천연접착제와의 성능을 비교 분석하였다. 최적의 배합비는 Co 0.7 part, Zr 1.0 part, Ca 0.5 part, Activ8 0.1 part를 첨가하였을 때이며, 이 때의 접착력은 $93.2{\pm}19.1N/cm^2$의 수준에 도달하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 말뚝기초 학술발표회
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• pp.85-106
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• 2000

The load distribution and deformation of drilled shafts subjected to axial loads were evaluated by a load transfer approach. The emphasis was on quantifying the load transfer mechanism at the interface between the shafts and surrounding highly weathered rocks based on a numerical analysis and small-scale tension load tests performed on nine instrumented piles. An analytical method that takes into account the soil coupling effect was developed using a modified Mindlin's point load solution. Based on the analysis, a single-modified hyperbolic model is proposed for the shear transfer function of drilled shafts in highly weathered rocks. Through comparisons with field case studies, it is found that the prediction by the present approach is in good agreement with the general trend observed by in-situ measurements.

• Structural Engineering and Mechanics
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• 제68권2호
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• pp.183-191
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• 2018

In this paper, harmonic responses of infilled multi-storey frames are obtained by using a single variable shear deformation theory (SVSDT) and dynamic stiffness formulations. Two different planar frame models are used which are fully infilled and soft storey. The infill walls are modeled by using equivalent diagonal strut approach. Firstly, free vibration analyses of bare frame and infilled frames are performed. The calculated natural frequencies are tabulated with finite element solution results. Then, harmonic response curves (HRCs) of frame models are plotted for different infill wall thickness values. All of the results are presented comparatively with Timoshenko beam theory results to reveal the effectiveness of SVSDT which considers the parabolic shear stress distribution along the frame member cross-sections.

• Advances in nano research
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• 제4권4호
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• pp.309-326
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• 2016

The buckling response of a single-layered graphene sheet (SLGS) embedded in visco-Pasternak's medium is presented. The nonlocal first-order shear deformation elasticity theory is used for this purpose. The visco-Pasternak's medium is considered by adding the damping effect to the usual foundation model which characterized by the linear Winkler's modulus and Pasternak's (shear) foundation modulus. The SLGS be subjected to distributive compressive in-plane edge forces per unit length. The governing equilibrium equations are obtained and solved for getting the critical buckling loads of simply-supported SLGSs. The effects of many parameters like nonlocal parameter, aspect ratio, Winkler-Pasternak's foundation, damping coefficient, and mode numbers on the buckling analysis of the SLGSs are investigated in detail. The present results are compared with the corresponding available in the literature. Additional results are tabulated and plotted for sensing the effect of all used parameters and to investigate the visco-Pasternak's parameters for future comparisons.

• Advances in nano research
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• 제7권4호
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• pp.265-275
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• 2019

In this work, the effect of size on the axial buckling behavior of single-layered graphene sheets embedded in elastic media is studied. We incorporate Eringen's nonlocal elasticity equations into three plate theories of first order shear deformation theory, higher order shear deformation theory, and classical plate theory. The surrounding elastic media are simulated using Pasternak and Winkler foundation models and their differences are evaluated. The results obtained from different nonlocal plate theories include the values of Winkler and Pasternak modulus parameters, mode numbers, nonlocal parameter, and side lengths of square SLGSs. We show here that axial buckling behavior strongly depends on modulus and nonlocal parameters, which have different values for different mode numbers and side lengths. In addition, we show that in different nonlocal plate theories, nonlocality is more influential in first order shear deformation theory, especially in certain range of nonlocal parameters.

• Smart Structures and Systems
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• 제21권1호
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• pp.15-25
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• 2018

This work presents the buckling investigation of embedded orthotropic nanoplates such as graphene by employing a new refined plate theory and nonlocal small-scale effects. The elastic foundation is modeled as two-parameter Pasternak foundation. The proposed two-variable refined plate theory takes account of transverse shear influences and parabolic variation of the transverse shear strains within the thickness of the plate by introducing undetermined integral terms, hence it is unnecessary to use shear correction factors. Nonlocal governing equations for the single layered graphene sheet are obtained from the principle of virtual displacements. The proposed theory is compared with other plate theories. Analytical solutions for buckling loads are obtained for single-layered graphene sheets with isotropic and orthotropic properties. The results presented in this study may provide useful guidance for design of orthotropic graphene based nanodevices that make use of the buckling properties of orthotropic nanoplates.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.552-560
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• 2004

Stone column is a soil improvement method and can be applicable for loose sand or weak cohesive soil. Since the lack of sand in Korea, stone column seems one of the most adaptable approach for poor ground as a soil improvement method. However, this method was not studied for practical application. In this paper, the most effective design parameters for the being capacity of stone column were studied. The parametric study of major design factors for single stone column was carried out under the bulging and general shear failure condition, respectively. Especially, a test result of single stone column by static load was compared with the bearing capacity values of suggested formulas. The analysis result showed that the ultimate bearing capacity by the formula was much less than the measured value by the static load test. Especially, the result of the parametric study under general shear failure condition showed that the bearing capacity has apparent difference between each suggested formulas with the variation of the major design parameters. Therefore, the result of this study can be a suggestion which is applicable for the field test and the future research.