• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.341-346
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• 2003

과실 포장화물(packaged freight)은 과실, 완충재 및 겉포장 상자로 구성되며, 속포장(내포장)하지 않는 것이 식품 포장이나 다른 포장과 구별된다. 그러나 과실 개개를 보호하기 위한 낱포장(단위포장)은 중요시되며, 사용되는 완충재가 이 기능을 한다. 과실 포장에 사용되는 겉포장 상자는 제품 취급의 편리성을 도모할 뿐만 아니라, 물류 과정 중에 제품의 보호와 상품에 대한 정보를 제공하는 포장 역할의 주체가 된다. 또한 완충재는 포장물에 전달되는 충격과 진동 등의 외력 완화와 응력 분산, 포장물의 표면보호, 상호간의 접촉방지 및 이동방지의 기능을 수행한다. 종전까지는 골판지 상자에 의한 포장화물 단위로 취급되는 경우가 대부분 이었는데, 농산물의 물류합리화와 물류비 절감 문제가 본격 대두되면서, 팰리트를 활용한 단위화물 적재 시스템(ULS) 즉, 팰리트 화물(palletized freight) 상태로 취급되는 경우가 점차 확대되고 있고 정부에서도 이를 적극 지원하고 있다. (중략)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.18-23
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• 2004

In this paper, material non-linear behavior of PZT wafer(3203HD, CTS) under high electric field and stress is experimentally investigated and the non-linearity of the PZT wafer is numerically simulated. Empirical functions that can represent the non-linear behavior of the PZT wafer have been extracted based on the measured piezo-strain under stress. The functions are implemented in an incremental finite element formulation for material non-linear analysis. New definition of the piezoelectric constant and the incremental strain are incorporated into the finite element formulation for a better reproduction of the non-linear behavior. With the new definition of the in incremental piero-strain the measured non-linear behavior of the PZT wafer has been accurately reproduced even for high electric field. For validation of the measured non-linear characteristics and the proposed approach, a PZT bimorph beam actuator has been numerically and experimentally tested. The predicted actuation displacement, based on the material nonlinear finite element analysis, showed a good agreement with the measured one.

• The Journal of Engineering Geology
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• v.1 no.1
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• pp.121-136
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• 1991

The focal mechanism of the Hongsung Earthquake (1978. Oct. 7, M$_L$=5.0, Latitude 36.62N, Longitude 1 26.67E) was evaulated using the polarity distribution of the P-Waveforms. Through the non-linear computer process, the compatibility of polarity distributions of the 9 P-Waveforms observed at teleseismic distances from the Hongsung Earthquake epicenter was investigated to those of the focal mechanism determined from the varying strike, dip and rake angles. The resultant values for the strike and dip angle of the principal fault plane, which apparently matches very well the sunface lineament of the Hongsung region, are determined to be about 247 degree and 78 degree with uncertainties, respectively. However, the rake angle of the focal mechanism has wide range of 40 degree to 160 degree, which is mainly due to the poor coverage of the azimuthal angle of the observed seismic stations. Due to the consistency of principal stress axes, the resultant focal mechanism could support the current stress regime of that region, which may be caused by subduction of the Pacific Plate under the Eurasia Plate along the Japan Trench. It also provides information of seismic source characteristics of the part of the Korean Peninsula for aseismic design criteria such as Site Specific Response Spectrum and Strong Ground Motion Time History for the nuclear power plants and related nuclear waste disposal facility sites.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.29-38
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• 2004

A finite element nonlinear stress-deformation model with multi-interface element is applied to the stability analysis of waste landfill slope. Strength parameters of waste and geosynthetic materials are obtained from the triaxial test of waste and the direct shear test of geosynthetics, respectively. The landfill models used for the numerical models are fit to regulations of the Korean waste management law. The results of the strength tests showed linear behavior for the waste and nonlinear behavior for the eosynthectic materials. The stability analysis with multi-interface element for the geosynthetic materials in the liner system showed large shear stress and slippage at the boundary of the foundation and the slope of the waste fill. This analysis verified the necessity of multi-interface analysis for waste landfills with composite liners.

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.299-311
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• 2003

This paper presents a finite element procedure to estimate the ultimate strength of space frames considering spread of plasticity. The improved displacement field is introduced based on the inclusion of second-order terms of finite rotations. All the non-linear terms due to bending moment, torsional moment, and axial force are precisely considered. The concept of plastic hinges is introduced and the incremental load/displacement method is applied for elasto-plastic analyses. The initial yield surface is defined based on the residual stress, and the full plastification surface is considered under the combined action of axial forces, bending and torsional moments. The elasto-plastic stiffness matrices are derived using the flow rule and the normality condition of the limit function. Finite element solutions for the ultimate strength of space frames are compared with available solutions and experimental results.

• Computational Structural Engineering
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• v.11 no.1
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• pp.191-204
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• 1998

The general formulation for free vibration and stability analysis of unsymmetric thin-wared space frames is presented in case where the shear deformation effects are neglected. The kinetic and total potential energies are derived by applying the extended virtual work principle, introducing displacement parameters defined at the arbitrarily chosen axis and including warping deformation and second order terms of finite semitangential rotations. In formulating the finite element procedure, cubic Hermitian polynomials are utilized as shape functions of the two node space frame element. Mass, elastic stiffness, and geometric stiffness matrices for the unsymmetric thin-walled section are evaluated, and load-correction stiffness matrices for off-axis distributed loadings are considered. In order to illustrate the accuracy and practical usefulness of this formulation, finite element solutions for the free vibration and stability problems of thin-walled beam-columns and space frames are presented and compared with available solutions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.279-286
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• 2020

In this study, we investigate the accuracy of higher order derivatives in the moving least square (MLS) difference method. An interpolation function is constructed by employing a Taylor series expansion via MLS approximation. The function is then applied to the mixed variational theorem in which the displacement and stress resultants are treated as independent variables. The higher order derivatives are evaluated by solving simply supported beams and cantilevers. The results are compared with the analytical solutions in terms of the order of polynomials, support size of the weighting function, and number of nodes. The accuracy of the higher order derivatives improves with the employment of the mean value theorem, especially for very high-order derivatives (e.g., above fourth-order derivatives), which are important in a classical asymptotic analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.973-987
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• 2018

Most of the previous seismic analyses have been carried out by separating the ground and structures, and there is a lack of comparative study on the dynamic behavior of high-rise and low-rise buildings. Therefore, in this study, the sensitivity analysis was performed with selected parameters by using a finite element analysis program in order to grasp the dynamic behavior of high-rise and low-rise buildings. As a result, it was turned out that the horizontal displacement, the interstory drift ratio, and the bending stress of a high-rise building were more affected by a long seismic wave than a low-rise buildings. Also, the weak parts of a high-rise and low-rise building were more affected by type of seismic wave than the ground conditions. Therefore, it is inferred that it will be helpful for seismic designs to consider the influence of ground conditions and seismic wave type on buildings.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.6
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• pp.55-63
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• 2008

This paper presents a seismic analysis technique for a 3D soil-structure interaction system in a frequency domain, based on the finite element formulation incorporating frequency-dependent infinite elements for the far field soil region. Earthquake input motions are regarded as traveling P, SV and SH waves which are incident vertically from the far-field soil region, and then equivalent earthquake forces are calculated using impedances of infinite soil by dynamic infinite elements and traction and displacement from free field response analysis. For verification and application, seismic response analyses are carried out for a multi-layered soil medium without structure and a typical nuclear power plant in consideration of soil-structure interaction. The results are compared with the free field response using a one-dimensional analytic solution, and a dynamic response of an example structure from another SSI package.

• Journal of Korean Society of Steel Construction
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• v.19 no.4
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• pp.367-381
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• 2007

A transmission tower was designed using the structural methodology to assume a simple truss behavior. However, there is a big difference between a simple truss behavior and a real one. A suitable explanation of structural stability is that it is a semi-rigid connection and not the assumed hinged connection. This study proposes an alternative structural-analysis modeling strategy for the transmission tower design. The element models that were considered were the truss element model, the beam element model, and the combined beam-truss element model. This study includes linear static analysis, free-vibration analysis, and elastic buckling analysis with respect to the design load. The results of the analysis indicate that the axial forces, axial stresses, and maximum displacements of the three analytical models are very similar. However, the bending moments and stresses of the beam element model and of the combined beam-truss element model are significantly high. The results of the free-vibration and elastic buckling analyses show that the beam-truss model can be conservatively used for the transmission tower design.