• Wind and Structures
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• 제24권1호
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• pp.25-41
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• 2017

The effects of finite cylinder free end shape on the mean and fluctuating wind pressures were investigated experimentally and numerically by using three different roof shapes: flat, conical and hemispherical. The pressure distributions on the roofs and the side walls of the finite cylinders partially immersed in a simulated atmospheric boundary layer have been obtained for three different roof shapes. Realizable $k-{\varepsilon}$ turbulence model was used for numerical simulations. Change in roof shapes has caused significant differences on the pressure distributions. When compared the pressure distributions on the different roofs, it is seen from the results that hemispherical roof has the most critical pressure field among the others. It is found a good agreement between numerical and experimental results.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.191-196
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• 2002

The paper presents a numerical and experimental investigation on dynamic behaviors of a towed low tension cable. In the numerical study, an implicit finite difference algorithm is employed for three-dimensional cable equations. Fluid and geometric non-linearity and bending stiffness are considered and solved by Newton-Raphson iteration. Block tri-diagonal matrix method is applied for the fast calculation of the huge size of matrices. In order to verify the numerical results and to see real physical phenomena, an experiment is carried out for a 6m cable in a deep and long towing tank. The cable is towed in two different ways; one is towed at a constant speed and the other is towed at a constant speed with top end horizontal oscillations. Cable tension and shear forces are measured at the top end. Numerical and experimental results are compared with good agreements in most cases but with some differences in a few cases. The differences are due to drag coefficients caused by vortex shedding. In the numerical modeling, non-uniform element length needs to be employed to cope with the sharp variation of tension and shear forces at near top end.

• 대한전기학회논문지
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• 제38권2호
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• pp.100-105
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• 1989

This paper presents an adaptive finite element method for magnetostatic force computation using Maxwell's stress tensor. Mesh refinements are performed automatically by interelement magnetic field intensity discontinuity errors and element force errors. In initial mesh, the computed forces for different integration paths give great differences, but converge to a certain value as mesh division is performed by the adaptive scheme, We obtained good agreement between analytic solutions and numerical values in typical examples.

• 한국CDE학회논문집
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• 제1권3호
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• pp.189-202
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• 1996

Complex geometric shapes can be defined simply and efficiently by combining and operating various surface primitives. These primitives and their intersection curves are used in finite element mesh generation to form an easy and intuitive procedure for finite element modelling of curved surfaces. This paper proposes techniques of automatic mesh generation on surface primitives with arbitrarily shaped boundaries and control curves, which may be created by surface to surface intersection. A method of automatic mesh generation on plane, which was previously developed by the author, has been modified for application to the surface mesh generation. Owing to the mesh generation-wise differences between planes and surfaces, the surfaces should be transformed into conceptual plane so that the modified plane mesh generation method can be applied. Surface development, mapping and mesh reconstruction are the key techniques suggested in this paper. The selection of the technique to apply can be determined automatically on the basis of the developability, existence of singularity and other characteristics of the surfaces on which the mesh is to be generated. The suggested techniques were implemented into parts of mesh generation functions of the finite element software, MacTran. Their validity and practicality were manifested by the actual use of this software.

• 대한기계학회논문집A
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• 제26권10호
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• pp.2201-2210
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• 2002

The accurate analysis of ultrasonic wave propagation and scattering plays an important role in many aspects of nondestructive evaluation. A numerical analysis makes it possible to perform parametric studies, and in this way the probability of detection and reliability of test results can be improved. In this paper, a finite element method was employed for the analysis of ultrasonic wave propagation in anisotropic materials, and the accuracy of results was checked by comparing with analytical predictions. The element size and the integral time step, which are the critical components for the convergence of finite element solutions, were determined using a commercial finite element code. Some differences for wave propagation in anisotropic media were illustrated when plane waves are propagating in a unidirectionally reinforced composite materials. When plane waves are propagating in nonsymmetric directions in a symmetric plane, deviation angles between the wave vector and the energy vector were found from finite element analyses and the results agreed well with analytical calculations.

• Earthquakes and Structures
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• 제12권1호
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• pp.67-77
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• 2017

In this paper, it is aimed to present a comparative study about the structural behavior of tall buildings consisting of different type of materials such as concrete, steel or timber using finite element analyses and experimental measurements on shaking table. For this purpose, two 1/60 scaled 28 and 30-stories wooden building models with $40{\times}40cm$ and $35{\times}35cm$ ground/floor area and 1.45 m-1.55 m total height are built in laboratory condition. Considering the frequency range, mode shapes, maximum displacements and relative story drifts for structural models as well as acceleration, displacement and weight limits for shaking table, to obtain the typical building response as soon as possible, balsa is selected as a material property, and additional masses are bonded to some floors. Finite element models of the building models are constituted in SAP2000 program. According to the main purposes of earthquake resistant design, three different earthquake records are used to simulate the weak, medium and strong ground motions. The displacement and acceleration time-histories are obtained for all earthquake records at the top of building models. To validate the numerical results, shaking table tests are performed. The selected earthquake records are applied to first mode (lateral) direction, and the responses are recorded by sensitive accelerometers. Comparisons between the numerical and experimental results show that shaking table tests are enough to identify the structural response of wooden buildings. Considering 20%, 10% and 5% damping rations, differences are obtained within the range 4.03-26.16%, 3.91-65.51% and 6.31-66.49% for acceleration, velocity and displacements in Model-1, respectively. Also, these differences are obtained as 0.49-31.15%, 6.03-6.66% and 16.97-66.41% for Model-2, respectively. It is thought that these differences are caused by anisotropic structural characteristic of the material due to changes in directions parallel and perpendicular to fibers, and should be minimized using the model updating procedure.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1895-1899
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• 2012

유한차분법을 적용한 압밀해석을 수행하였는데 순간하중이 재하되는 경우 유한차분법에 의해 예측되는 시간별 침하량과 Terzaghi 방법에 의한 침하량 사이의 차이는 시간격자간격을 충분히 작게 하여 해결할 수 있음을 알 수 있었다. 점증하중에 대한 압밀해석을 위한 유한차분식을 유도하였는데 해석결과에 따른 과잉간극수압의 분포가 Olson의 이론해와 일치하였다. 점증하중이 작용하는 경우에 대해 예측한 시간-침하거동에 있어 유도된 유한차분식에 의한 결과와 Terzaghi 및 Olson 에 의한 결과 또한 거의 일치하였다. 다단 점증하중에 대한 해석결과 또한 신뢰성이 높은 것으로 보인다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.17-21
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• 2002

A finite element method based on the two-dimensional progressive failure analysis is presented for characterizing the strength and failure of the unidirectional-fabric hybrid laminated composite joints under pin loading. The 8-node laminated shell element is incorporated in the updated Lagrangian formulation. Various failure criteria including the maximum stress, Tsai-Wu, Yamada-Sun, and combinations of them are used in conjunction with the complete unloading stiffness degradation method. For the verification, joint tests are conducted for the specimens with various geometries. Although there are some differences depending on the geometry, the finite element model using the Yamada-Sun or the combined Yamada-Sun and Tsai-Wu criterion predicts the failure strength best.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.696-699
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• 2004

Generally, the time history analysis among seismic response analyses of a structure needs more times than static analysis. Therefore the mechanical model of a structure has been used as a simple lumped parameter model in time history analysis. For the most cases, the simple mechanical model shows the similar results to that of detailed finite element model. so it is reasonable to use the simple mode] in preliminary analysis. In seismic design of liquid storage tank, such as LNG storage tank, the lumped parameter mode] also is being used in preliminary analysis, however sometimes shows the differences to the results of detailed finite element model. Therefore in this study, the dynamic characteristics between lumped parameter model and detailed finite model is compared for the variables such as height/diameter of liquid-storage tank and thickness of wall, then the applicability of beam mode] to the seismic response analysis are evaluated for some liquid storage tanks.

• 대한전자공학회논문지
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• 제19권1호
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• pp.29-34
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• 1982

U형 수준선의 특성임피던스는 유한차분법에 의해서도 계산될 수 있으나 이 연구에서는 모먼트법에 의하여 그의 특성 임피던스를 계산한다. 유한차분법에 의한 계산결과와 모먼트법에 의한 결과에는 10%정도의 차가 좌우한다. 그러나 내부도체가 외부도체의 중앙에 있을 때 모먼트법에 의한 결과는 선석적인 방법에 의한 결과와 거의 일치된다.