• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.285-288
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• 2010

유체저장탱크가 외부로부터 지진과 같은 동적하중을 받게 될 경우 유체와 구조물의 상호작용(Fluid-Structure Interaction)으로 인하여 일반적인 구조물과는 상이한 거동을 보이게 된다. 이러한 복잡한 상호작용을 고려하여 현재 내진 설계에서는 Housner와 Haroun의 이론을 적용한 단순화 모델들이 사용되고 있다. 이들 모델은 유체의 거동을 대류(convective) 성분과 충격(impulsive) 성분으로 구분하여 집중질량으로 단순화 한다. 하지만 점차 대형화되고 있는 유체저장탱크의 정확한 동적 거동 특성을 파악하고, 지진하중과 같은 방향성을 가진 하중에 대한 구조물의 정확한 응답을 해석하려면 단순화 모델의 적용성 검토가 필요하다. 본 연구에서는 지진하중을 받는 유체저장탱크의 동적거동을 집중질량 모델과 3차원 모델을 이용하여 해석하였다. 나아가 해석결과의 차이를 분석하여 단순화 모델의 정확도 향상을 위한 내진설계변수 산출에 관하여 향후 연구방향을 제시하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.105-111
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• 2007

A finite element analysis scheme is proposed to assess the dynamic response due to impulse excitation of ocean mining pipe system. Transient dynamic response analysis based on the proposed scheme was carried out for various types of impulses, and the magnitude of cable tension induced by impulse was discussed by using a model of 'Segero', a special purpose ship of KT-Submarine as well as ROV carrier 'Onnuri' A qualitative, prospective guideline for the relevant marine operation is obtained.

• Magazine of the Korea Concrete Institute
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• v.6 no.3
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• pp.180-189
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• 1994

An approximate method of normal coordinate idealization for use in nonlinear R /C frames has been developed. Normal coordinate apporaches have been used for nonlinear problems in the past, but they are not recerved wide acceptance because of the need for eigenvector computation in each time step. The proposed method circumvents the eigenvector recalculation problem by evaluating a limited number of sets of mode shapes in performing the dynamic analysis. Then some of the predetermined sets of eigenvectors are used in the nonlinear dynamic repeatedly. The method is applied to frame structures with ductile R /C elements. The plastic hinge zones are modeled with hysteres~s loops which evince degrading stiffness and pinching effects. Effxiencies and accuracies of the method for this application are presented.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.109-117
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• 2003

Traditional nonlinear static and dynamic analyses do not accurately estimate the energy dissipation capacity of reinforced concrete structure. Recently, simple equations which can accurately calculate the energy dissipation capacity of flexure-dominated RC members, were developed in the companion study. In the present study, nonlinear static and dynamic analytical methods improved using the energy-evaluation method were developed. For nonlinear static analysis, the Capacity Spectrum Method was improved by using the energy-spectrum curve newly developed. For nonlinear dynamic analysis, a simplified energy-based cyclic model of reinforced concrete member was developed. Unlike the existing cyclic models which are the stiffness-based models, the proposed cyclic model can accurately estimate the energy dissipating during complete load-cycles. The procedure of the proposed methods was established and the computer program incorporating the analytical method was developed. The proposed analytical methods can estimate accurately the energy dissipation capacity varying with the design parameters such as shape of cross-section, reinforcement ratio and arrangement, and can address the effect of the energy dissipation capacity on the structural performance under earthquake load.

• Geotechnical Engineering
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• v.6 no.3
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• pp.13-30
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• 1990

In this paper, response of pile foundations under seismic loading is studied for use in aseismic design of deep foundations. Both the pseudostatic methods such as subgrade reaction theory by Reese, and elastic analysis by Poulos, and the dynamic methods proposed by, respectively, Prakash and Gazetas, are used for this study. The top displacements and maximum bending moments of example piles are obtained by each method mentioned above, and the results by each method are compared among others. The group pile effects are also considered approximately. The calculated results are compared with experimental results obtained by Novak in 1984. The pseudostatic methods, combined with dynamic group interaction factors, and the dynamic method proposed by Gazetas which considers both kinematic interaction and inertial interaction, separately, estimate the top displacements reasonably well : the method by Prakah or the pseudostatic methods combined with static group interaction factors may overestimate the top displacements and bending moments as well. Therefore, it is recommended to the the simple elastic analysis combined with dynamic group interaction factors for aseismic design of pile foundatins and to confirm the results by the Gaz etas' dynamic methods.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.2
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• pp.139-148
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• 2012

The MLS(Moving Least Squares) Difference Method is a numerical scheme that combines the MLS method of Meshfree method and Taylor expansion involving not numerical quadrature or mesh structure but only nodes. This paper presents an dynamic algorithm of MLS difference method for solving transient solid mechanics problems. The developed algorithm performs time integration by using Newmark method and directly discretizes strong forms. It is very convenient to increase the order of Taylor polynomial because derivative approximations are obtained by the Taylor series expanded by MLS method without real differentiation. The accuracy and efficiency of the dynamic algorithm are verified through numerical experiments. Numerical results converge very well to the closed-form solutions and show less oscillation and periodic error than FEM(Finite Element Method).

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.211-225
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• 2019

Recently, earthquakes have occurred throughout the entire region of Korea and seismic analysis studies have been actively conducted in various fields. SSI analyses studies considering ground have been carried out consistently. However, few comparative analyses have been performed on the dynamic behavior of buildings according to numerical analysis method in the case of the previous dynamic analyses considering grounds. Therefore, in this study, the dynamic analyses were performed on a high-rise building by using both a finite element program MIDAS GTS NX and a finite difference program FLAC 2D. The results were compared and analyzed each other. As a result, both the maximum compressive and tensile bending stresses of above ground and below ground part were estimated to be a little larger by MIDAS GTS NX than by FLAC 2D. However, the maximum horizontal displacement value, the horizontal displacement distribution, and the position of weak part were turned out to be similar in both analysis programs. Therefore, it can be concluded that there is no difference in using either a finite element program or a finite difference program for the convenience of a user for a dynamic analysis.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.593-597
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• 2016

항공기의 비행 안정성을 판별하기 위해서는 정적(static)안정성과 동적(dynamic)안정성을 모두 고려해야 한다. 본 연구는 EDISON_CFD의 KFLOW_EDISON_2D3DOF, 2D_Com_P해석자를 이용해 2차원익형의 정적(static)계수와 동적(dynamic)계수를 구해 항공기 전체형상의 정적 안정성 및 동적 안정성을 분석하였다. 그 중 2015년도 인간 동력 항공기대회 건국대학교 참가 기체를 예시로 연구를 진행하였다. 주익 익형 SG6043과 미익 익형 NACA0012을 EDISON_CFD를 이용하여 각 익형의 모멘트계수를 구하고 그 결과값을 이용하여 기체의 무게중심에 대한 각 익형의 감쇠계수를 계산하였다. 그리고 주익과 미익의 면적비율과 코드길이의 비율을 고려해 전체 항공기형상의 안정성과 비행 형태를 분석하였다.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.289-299
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• 2012

The goal of this paper is to apply the multi-step Taylor method to a space truss, a non-linear discrete dynamic system, and analyze the non-linear dynamic response and unstable behavior of the structures. The accurate solution based on an analytical approach is needed to deal with the inverse problem, or the dynamic instability of a space truss, because the governing equation has geometrical non-linearity. Therefore, the governing motion equations of the space truss were formulated by considering non-linearity, where an accurate analytical solution could be obtained using the Taylor method. To verify the accuracy of the applied method, an SDOF model was adopted, and the analysis using the Taylor method was compared with the result of the 4th order Runge-Kutta method. Moreover, the dynamic instability and buckling characteristics of the adopted model under step excitation was investigated. The result of the comparison between the two methods of analysis was well matched, and the investigation shows that the dynamic response and the attractors in the phase space can also delineate dynamic snapping under step excitation, and damping affects the displacement of the truss. The analysis shows that dynamic buckling occurs at approximately 77% and 83% of the static buckling in the undamped and damped systems, respectively.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.6 s.46
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• pp.1-12
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• 2005

For a shear-deformable beam-column element subjected io non-conservative forces, equations of motion and a finite element formulation are presented applying extended Hamilton's principle. The influence of non-conservative force's direction parameter, internal and external damping forces, and shear deformation and rotary inertia effects on divergence and flutter loads of Beck's columns are intensively investigated based on element stiffness, damping and mass matrixes derived for the non-conservative system.