• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.04a
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• pp.20-20
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• 2000

초음속 과소팽창 제트는 베럴충격파(Barrel shock), 팽창파(Expansion fan), 반사충격파(Reflected shocks), 마하디스크(Mach disc), 그리고 제트경계면(Exhaust-gas Jet boundary)로 이루어지는 여러 충격파 셀(Shock ceil)의 유동 형태를 나타난다. 이러한 초음속 과소팽창 제트가 수직 평판에 충돌하면 초음속 자유 제트와는 다른 변형된 유동장이 형성된다.

• Journal of Ocean Engineering and Technology
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• v.14 no.1
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• pp.11-16
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• 2000

수중날개를 대상으로 임의로 변형하는 이층류의 수직계산을 수행하였다. 계산은 비구조격자와 접면포착법을 이용하여 자유표면의 형상을 결정하였다 본 연구에 의하면 낮은 물속 깊이와 높은 프루드수에서 쇄파현상이 발생하였다 수중날개에 대하여 쇄파형상의 효과를 연구하였고 실험값과 계산값을 상호비교함으로서 격자의 민감성을 수직적으로 확인하였다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.395-396
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• 2023

The current building structural standards present design requirements for the vertical construction joint of a slurry wall when it is used as a permanent wall. This paper proposes design methods and considerations according to the requirements of the relevant standards.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.397-398
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• 2023

To design the shear connections for vertical construction joints of slurry walls, it is necessary to create a force-displacement curve that represents the structural performance of the shear connections. This paper proposes a method for preparing the force-displacement curve of the shear connections including major considerations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.195-202
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• 2004

The shell due to the effect of initial normal pressures on the shell surface was based on the assumption that the directions of the pressures are always normal to the undeformed shell surface, and that the change in the surface area of the shell is negligible. But the fact that the pressure are always normal to the deforming surface leads "follower force". The follower effect in the analysis can significantly alter the solution for natural frequency and buckling load as compared to the case when the direction of the pressures are assumed to be normal to the uniform shell surface. The expression for the part of strain energy contribution from normal pressure due to the effect of follower force was derived and added to the element stiffness matrix of axisymmetric shell. In the case of increasing external pressure, the natural frequencies decrease until one of them reaches zero. Theoretically the smallest applied load that reduces the frequency of any mode to zero, will have same magnitude as that of the buckling load. In order to determine the bucking load of the shell a few sets of frequencies are computed and the results considering the follower effects are well with the exact solution while the case without that are quite different. But in case of hemispherical dome, there are little difference in buckling pressure between with and without the effect of follower force.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.107-119
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• 1991

This dissertation analyzes the running mechanism of flexible and thin tape above rotating head through the experiment. The scope of study is confined to measure the vertical deformation of running tape under hydrodynamic pressure invoking phenomena of elasto-hydrodynamic lubrication between the protruded bump on a rotating cylinder ad the running tape. Experimental system is devised to measure the vertical deflection of the running tape by opto-electronical displacement gauge, which enables to detect microscopic surface deflection of high frequency. Thorough the tests of small specimens of groove and bump, the accuracy and reliability of this experimental method is confirmed and achieved an accuracy within 5%(2.mu.m) error for the microscopic deflection with high frequency. In experimental works, the effects of bump size on flying characteristics of the tape were evaluated and examined. For the vertical deformation of the running tape. the numerical results and its trend agree qualitatively with the experimental ones.

• Tunnel and Underground Space
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• v.20 no.3
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• pp.225-232
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• 2010

In this study, a newly modified 3-dimensional strain-dependent hydraulic conductivity modification relation which incorporates the influences of normal deformation and shear dilation is suggested. Since rock mass is simulated as a orthogonally jointed medium, an anisotropic hydraulic conductivity field can be evaluated using that relation. The empirical relationship on the basis of GSI and disturbance factor has been used to estimate the value of a modulus reduction ratio (ratio of rock mass deformation modulus to rock matrix elastic modulus). Principal hydraulic conductivity directions is not generally coincident with the global coordinate due to the inclining of joint and the influence of joint inclination is evaluated under strain rotation. Result shows that change of hydraulic conductivity does decreases with the increase of GSI and disturbance factor has much effects on the hydraulic conductivity of rock mass getting GSI value above 50. It is found that the inclination of joint impacts on the variation of hydraulic conductivity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.361-372
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• 2005

In the previous study(Kim 등, 2004), the finite element method was used for the vortical vibration analysis of suspension bridge with the effects of the shear deformation and the rotary inertia under moving load considering the bridge-vehicle interaction. The purpose of this study is to investigate the effect of an eccentric vehicle and shear deformation. So we firstly performs the eigenvalue analysis for the free vortical and the torsional vibration of suspension bridges using FEM analysis. Next the equations of motion considering interaction between suspension bridges and vehicles/trains are derived using the mode superposition method. And then dynamic analysis was performed using the Newmark method. Finally through the numerical examples, the dynamic responses of bridges are investigated according to the proposed procedure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.361-374
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• 2016

The material property of the rubber has been studied in order to improve the reliability of the finite element model of a lead rubber bearing (LRB) which is a typical base isolator. Rubber exhibits elastic behaviour even within the large strain range, unlike the general structural material, and has a hyper-elastic characteristics that shows non-linear relationship between load and deformation. This study represents the mechanical characteristics of the rubber by strain energy function in order to develop a finite element (FE) model of LRB. For the study, several strain energy functions were selected and mechanical properties of the rubber were estimated with the energy functions. A finite element model of LRB has been developed by using material properties of rubber and lead which were identified by stress tests. This study estimated the horizontal and vertical force-displacement relationship with the FE model. The adequacy of the FE model was validated by comparing the analytical results with the experimental data.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.89-100
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• 2007

In the companion paper, we provided the novel elastic-plastic constitutive model based on the micromechanics theory. Herein, the elastic and elastic-plastic deformation of granular soils is meticulously analyzed. To guarantee high accuracy of the microscopic parameter, the systematic procedure to evaluate the parameters is provided. The analysis of the elastic response during the isotropic and triaxial compression shows that the stress-level dependency of cross-anisotropic elastic moduli is induced by the power relationship of the contact force in the normal contact stiffness, while the evolution of fabric anisotropy is more pronounced during triaxial compression. The micromechanical analysis indicates that the plastic strains are likely to occur at very small strains. The plastic deformation of tangential contacts has an important role in the reduction of soil stiffness during axial loading.