• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.151-158
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• 2005

This research analyzes eigenvalue analysis of stiffened plates on the Pasternak foundations using the finite clement method. For analyzing the stiffened plates, both the Mindlin plate theory and Timoshenko beam-column theory were applied. In application of the finite element method, 8-nodes serendipity clement system and 3-nodes finite element system were used for plate and beam elements, respectively. Elastic foundations were modeled as the Pasternak foundations in which the continuity effect of foundations is considered. In order to verify the theory of this study, solutions obtained by this analysis were compared with the classical solutions in reference, experimental solutions and solutions obtained by SAP 2000. The natural frequency of stiffened plates on Pasternak foundations were determined according to changes or foundation parameters and dimensions of stiffener.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.3
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• pp.183-190
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• 2019

This paper introduces a near-tip grid refinement and explores its usefulness in the crack analysis by the natural element method(NEM). As a sort of local h-refinement in finite element method(FEM), a NEM grid is locally refined around the crack tip showing high stress singularity. This local grid refinement is completed in two steps in which grid points are added and Delaunay triangles sharing the crack tip node are divided. A plane strain rectangular plate with symmetric edge cracks is simulated to validate the proposed local grid refinement and to examine its usefulness in the crack analysis. The crack analysis is also simulated using a uniform NEM grid for comparison. Unlike the uniform grid, the refined grid provides near-tip stress distributions similar to the analytic solutions and the fine grid. In addition, the refined grid shows higher convergence than the uniform grid, the global relative error to the total number of grid points.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.1
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• pp.39-44
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• 1993

This paper is concerned with developing a finite element model incorporating boundary damper techniques which is applicable to the prediction of wave agitations in harbors. Based on the linear wave theory, a mild-slope equation is used. In order to consider the wave energy dissipations on solid boundary. the partial reflecting boundary condition is introduced. Radiating boundary condition is modeled by using tile second-order boundary damper developed by Bando et al. (1984). The near field region in harbor is discretized using 8-noded isoparametric elements, the boundary conditions are presented using 3-noded line elements. The numerical model is applied to a fully open rectangular harbor to prove its validity. Numerical experiments are also performed to investigate the effects of the wave reflection coefficients of solid boundary and the types of the dampers.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.307-315
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• 2008

Post-tensioned precast concrete system (PPS) consists of U-shaped precast wide beams and concrete column. The continuity of beam-column joint is provided with the topping concrete on the PC shell beam and post-tensioning. Nonlinear analysis was conducted, using ANSYS, a finite-element analysis program, to obtain data for determining the characteristics of the structure and to allow various parametric analyses for post-tensioned wide beam-column connections. In this analysis, the Solid 65 element was used, in which concrete element had 8 nodes and each node had 3 degrees of freedomIn. Solid 65, the shear-transfer factor reflects a decrease of shear strength for the positions with cracks, as an impact factor to make the analysis value approximate the experiment value. In this study, the behavior of test specineus were most closely predicted to the experimental results, when the shear-transfer coefficient 0.85 was used for a closed crack, and 0.2 was used for an open crack.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.247-252
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• 2005

This research presents a three-dimensional modeling technique for a flexible sheet. A relative coordinate formulation is used to represent the kinematics of the sheet. The three-dimensional flexible sheet is modeled by multi-rigid bodies interconnected by out-of-plane joints and plate force elements. A parent node is designated as a master body and is connected to the ground by a floating joint to cover the rigid motion of the flexible sheet in space. Since the in-plane deformation of a sheet such as a paper and a film is relatively small, compared to out-of-plane deformation, only the out-of-plane deformation is accounted for in this research. The recursive formulation has been adopted to solve the equations of motion efficiently. An example is presented to show the validity of the proposed method.

• Computational Structural Engineering
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• v.3 no.2
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• pp.77-88
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• 1990

Two perforated plates (a square plate and a rectangular plate having an aspect ratio 1.57(L/sub x/=11, L/sub y/=7)) are taken as analysis examples. Each of these plates is given some changes in the boundary conditions. The size of cutouts as well as their locations are also changed in order to examine the variation of two eigenvalues corresponding to the fundamental mode. The relationship between two eigenvalues is established by changing the magnitude of edge thrust.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.257-266
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• 2004

A three node triangular element with drilling rotations incorporating improved higher-order zig-zag theory(HZZT) is developed to accurately assess the stress distribution through thickness of the laminated plate and analyze the vibration of pretwisted composite plates with embedded damping layer. Shear force matching conditions are enforced along the interfaces between the embedded damping patch and the border patch. The natural frequencies and model loss factors are calculated for cantilevered pretwisted composite blade with damping core with the present triangular element, and compared to experiments and MSC/NASTRAN using a layered combination of plate and solid elements.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.331-340
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• 2010

The basic theory and application of new adaptive finite element algorithm have been proposed in this study including the adaptive hp-refinement strategy, and the effective method for constructing hp-approximation. The hp-adaptive finite element concept needs the integrals of Legendre shape function, nonuniform p-distribution, and suitable constraint of continuity in conjunction with irregular node connection. The continuity of hp-adaptive mesh is an important problem at the common boundary of element interface. To solve this problem, the constraint of continuity has been enforced at the common boundary using the connectivity mapping matrix. The effective method for constructing of the proposed algorithm has been developed by using hierarchical nature of the integrals of Legendre shape function. To verify the proposed algorithm, the problem of simple cantilever beam has been solved by the conventional h-refinement and p-refinement as well as the proposed hp-refinement. The result obtained by hp-refinement approach shows more rapid convergence rate than those by h-refinement and p-refinement schemes. It it noted that the proposed algorithm may be implemented efficiently in practice.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.192-195
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• 2010

본 논문에서는 해상 크레인과 중량물의 동적 거동을 시뮬레이션하기 위해, 유한 요소 정식화(finite element formulation)를 이용하여 해상 크레인의 붐(boom)을 탄성체로 모델링 하였다. 붐은 3차원 탄성 빔(beam) 요소로 가정하고, 각 요소의 변형에 의한 변위는 형상 함수(shape function)과 절점 좌표(nodal coordinate)를 이용하여 정의하였다. 변형 변위를 이용하여 탄성 붐의 강성 행렬(stiffnes matrix)을 유도하고, 탄성 변위를 포함하는 위치 벡터를 이용하여 질량 행렬을 유도한다. 해상 크레인과 중량물로 이루어진 운동 방정식에 탄성 붐을 포함하여 유연 다물체계(flexible multibody system) 운동 방정식을 구성한다. 외력으로는 선박 유체정역학적 힘, 유체동역학적 힘, wire rope의 장력, 중력 그리고 계류력(mooring force)이 고려되었다. 먼저 요소의 개수를 변경하며 탄성 붐의 동적 거동을 시뮬레이션 하여, 유한 요소 정식화를 이용한 모델링의 타당성을 검증하였다. 그리고 해상 크레인과 중량물의 동적 거동 시뮬레이션에 탄성 붐 모델을 적용하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.129-138
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• 2004

In this study we determine a dynamic analysis of the existing two-span prestressed concrete box girder bridge subjected to moving vehicle loads using the experimental measurements. The moving loads applied in this paper are classified as general travelling, suddenly brake, continuous travelling, reversely travelling and reversely travelling impact loads for increasing velocities. For each travelling load, we search dynamic behaviors and characteristic in various measuring point of box girder section. In addition, the three-dimensional numerical results analyzed by the developed finite element program using flat shell element with six degrees of freedom per a node are compared with the measured experimental data. Dynamic behaviors caused impact loads by suddenly braking, reversely travelling, are bigger than by general travelling in box girder. Three-dimensional numerical results are better than one-dimensional results.