• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.345-352
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• 2014

In this paper, the CAD data for the optimal shape design obtained by isogeometric shape optimization is directly used to fabricate the specimen by using 3D printer for the experimental validation. In a conventional finite element method, the geometric approximation inherent in the mesh leads to the accuracy issue in response analysis and design sensitivity analysis. Furthermore, in the finite element based shape optimization, subsequent communication with CAD description is required in the design optimization process, which results in the loss of optimal design information during the communication. Isogeometric analysis method employs the same NURBS basis functions and control points used in CAD systems, which enables to use exact geometrical properties like normal vector and curvature information in the response analysis and design sensitivity analysis procedure. Also, it vastly simplify the design modification of complex geometries without communicating with the CAD description of geometry during design optimization process. Therefore, the information of optimal design and material volume is exactly reflected to fabricate the specimen for experimental validation. Through the design optimization examples of elasticity problem, it is experimentally shown that the optimal design has higher stiffness than the initial design. Also, the experimental results match very well with the numerical results. Using a non-contact optical 3D deformation measuring system for strain distribution, it is shown that the stress concentration is significantly alleviated in the optimal design compared with the initial design.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.639-648
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• 2000

A model analysis is used to predict the impact response of a simply supported elastic circular cylindrical shell composed of two bonded isotropic layers. The governing equations for a two-layered cylindrical shell are derived on the basis of an improved theory for the single-layer shell which includes the effects of transverse shear deformation and rotary inertia. Calculations are made for the specific case of the steel-concrete cylindrical shell subjected to a suddenly applied load. The solutions show that the method yields very good results. Therefore the proposed method is useful not only for a better investigating of the response characteristics of the shell but also available for a check on other numerical methods such a FEM.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.967-968
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• 2011

직립 기동 영구자석 동기 전동기(Line-Start Permanet Magnet Synchronous Motor : LSPM)는 기존 3상 유도기에 비해 높은 효율과 역율을 가진다. 또한 제어기를 사용하지 않고 기동 할 수 있다는 장점 때문에 펌프나 팬 등에 단순한 구동원에 적용 할 수 있는 전동기이다. 구조는 유도기와 달리 영구자석이 매입되기 때문에 이에 따라 영구자석의 위치와 크기에 따라 모터의 특성이 변화 한다. 본 논문에서는 실험 계획법과 FEM 유한 요소법을 이용하여 영구자석의 크기는 고정되어 있는 상태에서 영구자석 슬롯의 모양만을 설계 인자에 따라 해석하였다. 그리고 해석을 통한 결과를 비교 분석하여 직립기동 영구자석 동기 전동기의 효율과 토크특성을 개선하고자한다.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.299-310
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• 2008

In this study, the regression analysis method was tested for the estimation of peak stress at stress concentration area in the cervical bone. Submerge type EZ plus implant (Megagen. Daegu, Korea), 4.1 mm in cervical diameter and 9.6 mm in endosseous length, were axisymmetrically modelled together with surrounding alveolar bone of which the width was 10 mm. Vertical force of 100 N was applied to a head of crown above 8.5 mm from the outer surface of the cortical bone. Four different mesh models were composed of differently sized elements in vicinity of sharp corners, and they include 6 stress monitoring points that are located in the same geometrical points regardless of the differences in the meshes. Primary consideration was given to the stresses in the cortical bone surrounding the implant neck. The results showed that virtually all the stresses were concentrated in the cortical bone regardless of mesh designs. The peak stresses were successfully calculated by a regression analysis in a stable manner, as far as the mesh is designed to represent the acute gradient of stresses near the sharp corner.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.179-187
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• 2000

When one considers the property of the axisymmetry, an analysis of an axisymmetric shell subjected to unaxisymmetric loading can be employed to save time and computer memory space. If one considers the Fourier series of the circumference direction of loads and displacements, an axisymmetric tank subjected to a nonaxisymmetric load can be treated as a frame element. Using the Fourier series, the authors derived the stiffness matrix of the cylindrical shell subjected to unaxisymmetric loading by the usual finite element method, and converted the stiffness matrix of a frame element into a transfer matrix by rearranging the stiffness matrix to apply the transfer matrix method. Here the most significant purpose of this paper is to achieve the fewest number of simultaneous equations for analysing an axisymmetric shell subjected to a nonaxisymmetric load. The results of the proposed method of the analysis of the cylindrical shell subjected to a wind load and a water load show no differences when compared to the other methods.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.173-181
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• 2005

This study deals with a method to identify damages of free vibrating thin plate structures using the combined finite element method (FEM) and the advanced uniform micro-genetic algorithm.To solve the inverse problem using the combined method, this study uses several natural frequencies instead of mode shapes in a structure as the measured data. The technique described in this paper allows us not only to detect the damaged elements but also to find their numbers, locations, and the extent of damage.To demonstrate the feasibility of the proposed method, the algorithm is applied to a free vibrating steel thin plate structures with arbitrary damages. From the standpoint of computation efficiency, the proposed method in this study has advantages when compared with the existing simple genetic algorithms. The numerical examples demonstrate that the method using micro-genetic algorithms can possibly detect correctly the damages of thin plates from only several natural frequencies instead of their natural modes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8654-8664
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• 2015

Beam-type structures with non-uniform cross sections are widely used in mechanical, architectural, and civil engineering fields. This paper deals with dynamic characteristics and vibration problems. Governing equations are first derived by using local coordinates. Their solutions are then assumed by using Galerkin's mode summation method. Bisection method is also applied in solving the determinant of the matrix which can provide natural frequencies. Whereas finite element methods adopt admissible functions satisfying only geometric boundary condition, in this study we apply Galerkin's mode summation method which uses eigen-functions satisfying both governing equations and boundary conditions. Modal analysis and experimental tests are finally performed using simply-supported beams with four different non-uniform cross-sections. Our analytical results then show good agreement with experimental ones.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.835-840
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• 2023

Compared to 3D FEM, 2D FEM can be analyzed by simplifying the model and conditions. However, with respect to coil conditions, in many cases, direction of coils(upward, downward, entrance, exit, etc.) are sequentially configured and set up the FEM analysis conditions. This paper shows simplification of coil conditions and reduction of analysis time by applying the equivalent winding method composed of one FEM coil even if it has multiple slots, and shows consistency of results by applying it to a winding type magnetic gear.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2411-2425
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• 2013

In the design of pile foundation on the rock layer in the stratified structure with sedimentary and rock layers, the structural analysis of the stratified rock layer is required to determine the failure modes (flexural failure, punching shear failure or end bearing failure) and the bearing capacity of the rock layer. However, the existing usable Elastic Plate Analysis Method (EPAM) suggested by ACI committee 436 and Korean Code Requirements for Structural Foundation Design is very complex, and engineers have many difficulties in using it. Therefore, in this research, we proposed the relatively simple Circular Foundation Analysis Method (CFAM) with the concept and the equation of the equivalent effective width (radius) instead of the complex EPM, and the related equations of bending moment and shear force to be equal to the analysis results of EPAM. As a result, the proposed CFAM using the equivalent effective width (radius) is simple and convenient to use, and the analysis results of it are very good in their accuracies comparing those of EPAM and Finite Element Method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.2
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• pp.75-83
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• 2023

In this paper, we present the analysis results on the vibration serviceability of a pedestrian bridge considering the effect of pedestrian moving mass inertia. Using dynamic finite element analysis, we considered different walking scenarios, including pedestrian density, walking speed, random walking, and synchronized walking, to analyze the acceleration response of a 40m long single-span bridge with a steel composite box cross section. We showed that the equivalent fixed mass analysis method did not significantly differ from the moving mass analysis in the random walk scenario and a wider frequency excitation band may be useful to consider when evaluating vibration serviceability in a random walk scenario.