• Journal of Korean Association for Spatial Structures
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• v.2 no.2 s.4
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• pp.59-67
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• 2002

In this study, a method that estimates stiffness and mass matrices of shear building from modal test data is presented. This method applied of building depends on the number of measurement points that are less in number than the total structural degrees of freedom, and on the first two orders of structural mode measured. By means of this method it is possible to use modal data of unmeasurable points to estimate total stiffness and mass matrices of structure. Some examples are studied in this paper, and its result shows that this method is reliable.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.4
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• pp.487-496
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• 1985

회전하는 축대칭 얇은 셸구조물의 진동 특성을 유한요소법에 의하여 해석하였다. 2개의 절점을 가진 Conical Frustrm 형태의 축대칭 요소를 사용하였으며 원주방향의 변위는 Fourier Series로 분해하여서 방정식의 수를 상당히 줄일 수 있었다. Sanders-Koiter의 셸이론을 사용하였으며 진 동 모우드는 회전의 영향을 설명하기 위하여 대칭 및 비대칭 모우드를 모두 고려하였다. Coriolis 행렬을 포함하는 운동방정식에서 고유 진동수를 계산하기 위해서 질량, 강성 및 Coriolis 행렬로 이루어지는 Hermitian 행렬의 Sturm Sequence Property를 이용하였으며, 좁은 밴드를 갖는 대형 행렬에 알맞는 Determinant Search 방법을 확장하여 고유진동수 및 벡터를 구하였다. 원통형 셸에 대하여 정지한 경우 계산한 고유진동수를 실험치 및 이론치와 비교한 결과 잘 일치됨을 알 수 있었다. 여러 가지 회전 속도에 대해서 얻어진 고유진동스를 이론치와 비교한 결과 잘 일치 됨을 알 수 있어\ulcorner며 회전의 영향으로 traveling wave진동의 현상이 나타남을 알 수 있었다.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.9-16
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• 1998

The joint characteristics are necessary to be determined in the early stage of the vehicle body design. Researches on identification of joints in a vehicle body have been performed until the recent year. In this study, the joint characteristics of vehicle struct- ure were expressed as condensed forms from the full joint stiffness and mass matrix. The condensed joint stiffness and mass matrix were applied to typical T-type and Edge-type joints, and the usefulness was confirmed. In addition, those were applied to center pillar and full vehicle body to validate the practical application.

• Computational Structural Engineering
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• v.4 no.1
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• pp.83-94
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• 1991

This paper presents an efficient and accurate method for nonlinear analysis of frame structures by idealized structural unit method. The main idea behind the present method is to minimize the computational effort by reducing the number of unknowns. An explicit form of the tangential elastic stiffness matrix of the element is derived by the principle of virtual work. The ultimate limit state of the element is judged on the basis of the formation of a plastic hinge mechanism. The elasto-plasto-plastic stiffness matrix of the element is derived by plastic node method and the post-ultimate stiffness equation is formulated under a simple analytic consideration. A comparison between the present solution and the existing experimental and other numerical result for unit column member and simple frame structure is made. If is clear from the result of this study that the present method is very useful because the computing time required is very small while giving the accurate solution.

• Composites Research
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• v.19 no.5
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• pp.1-6
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• 2006

In this study, a closed-form analysis has been developed for the transverse shear behavior of thin-walled composite beams with closed cross-sections. The shear flow distributions and cross-section stiffness coefficients are derived analytically by using a mixed beam approach. The theory has been applied to single-celled composite box-beams with elastic couplings. The location of the shear center and the effect of transverse shear deformation on the static behavior of composite beams are investigated in the framework of the analysis. The present results are validated against those of a two-dimensional finite element analysis and a good correlation has been obtained for box-beam cases considered in this study.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.165-168
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• 2001

고 전계하에서 수직 및 수평 전계의 영향을 고려할 수 있는 Hewlett-Packard 이동도 모델을 구현하였다. HP 이동도 모델은 BANDIS에 구현되었다. 구현된 HP이동도 모델을 검증하기 위해 N-MOSFET과 P-MOSFET에 대해 모의실험을 수행하여 MEDICI와 비교한 결과, 드레인 전압-드레인 전류는 5% 이내의 최대 상대 오차를 보였고 전위 분포는 5% 이내의 최대 상대오차를 보였다. MEDICI에서는 1회 수렴을 하기위해 평균 4.6회 이하의 행렬 연산이 필요한 반면 BANDIS에서는 평균 4.3회 이하의 행렬 연산이 필요하다.

• Journal of Korean Society of Steel Construction
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• v.20 no.3
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• pp.409-419
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• 2008

A co-rotational quasi-conforming formulation of four- node stress resultant shell elements using Ivanov-Ilyushin yield criteria are presented for the nonlinear analysis of plate and shell structure. The formulation of the geometrical stiffness is defined by the full definition of the Green strain tensor and it is efficient for analyzing stability problems of moderately thick plates and shells as it incorporates the bending moment and transverse shear resultant force. As a result of the explicit integration of the tangent stiffness matrix, this formulation is computationally very efficient in incremental nonlinear analysis. This formulation also integrates the elasto-plastic material behaviour using Ivanov Ilyushin yield condition with isotropic strain hardening and its asocia ted flow rules. The Ivanov Ilyushin plasticity, which avoids multi-layer integration, is computationally efficient in large-scale modeling of elasto-plastic shell structures. The numerical examples herein illustrate a satisfactory concordance with test ed and published references.

• Composites Research
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• v.32 no.5
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• pp.258-264
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• 2019

In this paper, a progressive failure analysis method was developed using the Hashin failure criterion and crack band model. Using the failure criterion, the failure initiation was evaluated. If the failure initiation is occurred, the damage variables at each failure modes (fiber tension & compression, matrix tension & compression) was calculated according to linear softening degradation behavior and the variables are used to derive the damaged stiffness matrix. The damaged stiffness matrix is reflected to damaged material and the progressive failure analysis is continued until the damage variables to be 1 that complete failure of material. A series of processes were performed using FE commercial code ABAQUS with user defined material subroutine (UMAT). To evaluate the proposed progressive failure model, the experimental results of open hole composite laminate tests was compared with numerical result. Using digital image correlation system, the strain behavior also was compared. The proposed numerical results were coincided well with the experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.10a
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• pp.25-30
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• 1994

A vector algorithm for calculating the stiffness matrices of reinforced concrete shell elements is presented. The algorithm is based on establishing vector lengths equal to the number of elements. The computational efficiency of the proposed algorithm is assessed on a Cray Y-MP supercomputer. It is shown that the vector algorithm achieves scalar-to-vector speedup of 1.7 to 7.6 on three inelastic problems.

• Computational Structural Engineering
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• v.4 no.2
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• pp.9-12
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• 1991

공학문제에 있어서, 해석적으로 접근할 수 없었던 많은 경우의 문제들이 유한요소법(Finite Element Methods)의 정형화된 모형화 및 해석과정을 통하여 쉽게 접근되어질 수 있었다. 최근 보다 효율적인 요소개발과 컴퓨터 기술의 발달로 유한요소법은 더욱 효과적인 해석 수단이 되어가고 있다. 그러나 지반공학 문제와 같은 무한영역 문제를 유한요소법으로 해석할 경우, 매우 큰 영역을 모형화하기 위하여 많은 수의 요소가 요구되며 이에 따른 자유도(Degree of Freedom) 수의 증가로 많은 계산시간을 요구하게 된다. 본 고는 무한영역 문제를 효과적으로 모형화하기 위하여 연구, 개발되어진 무한요소(Infinite Element)에 대하여 소개하려 한다. 무한요소의 기본개념과 강성행렬의 형성방법을 보인 후, 기초공학 문제를 예로 하여 이의 적용방법을 간략하게 설명하였다.