• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.2
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• pp.97-105
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• 2011

This paper was conducted on analytical solution using superposition and FEM analysis in the free vibration analysis of rectangular plates under uniform thermal loadings. Materials of three rectangular plates were aluminum, steel and stainless-steel respectively. Applied temperature conditions were from room temperature to $300^{\circ}C$ and boundary condition was free-free condition. Fully symmetric mode(FSM), fully antisymmetric mode(FASM) and symmetric-antisymmetric mode(SAM) were analyzed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.649-659
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• 1999

본 연구에서는 점탄성감쇠기가 설치된 비비례 감쇠 구조물의 바람에 대한 확률적 응답을 진동수영역에서 구하였다. 복소수 고유치 및 고유백터를 바탕으로 모드중첩법을 이용하여 응답의 RMS 값을 구하고 그것을 근사적인 방법인 모드 변형에너지법에서 얻은 결과와 비교하였다. 또한, 가력 진동수에 따라서 변하는 점탄성감쇠기의 강성 및 감쇠 계수를 상수로 모형화하였을 때의 풍응답 해석 결과의 정확성을 진동수영역에서 검증하였다. 해석결과에 의하면 감쇠기의 진동수 의존 특성은 구조물의 1차 고유 진동수에 의해서 비교적 정확하게 표현되었고, 모드 변형에너지법은 대체로 정확한 결과를 도출하였지만, 가속도 응답을 구할 때에는 다소 큰 오차를 유발하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.5
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• pp.376-385
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• 2017

In this paper, a method for the estimation of structural displacements using structure's mode shapes and accelerations is suggested to reduce the disadvantages of acceleration time integration method. Acceleration time integration method requires accurate information on initial conditions, and errors caused by noise can be accumulated during time integration. To avoid these problems, the method for the estimation of structural displacements based on mode superposition method is developed and two vibration experiments for cantilever beam are conducted to verify this method. Static displacements and dynamic displacements of beam structure are estimated using measured accelerations from experiments and mode shapes of cantilever beam, and they are compared with measured displacements using laser displacement sensor. From these results, the validity and usefulness of this method are verified.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.3
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• pp.1-9
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• 2011

The purpose of this study is to examine the dynamic characteristics of low, medium and high speed Maglev trains and guideways through dynamic interaction analysis. The coupled dynamic equations of motion for a vehicle of 10-dof and the associated guideway girders are developed by superposing vibration modes of the girder itself. The controller used in the UTM-01 Maglev vehicle is adopted to control the air gap between the bogie and guideway in this study. The effect of roughness, the guideway deflection-ratio and vehicle speed on the dynamic response of the maglev vehicle and guideway are then investigated using the 4th Runge-Kutta method. From the numerical simulation, it is found that the air gap increases with an increase of vehicle speed and the roughness condition. In particular, the dynamic magnification factor of the guideway girder is small at low and medium speeds, but the factor is noticeable at super-high speeds.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.515-520
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• 2008

This paper develops a mite element model of a polygon mirror scanner motor supported by the sintered bearing and flexible supporting structures to analyze the shock response by using the finite element method and the mode superposition method. The validity of the proposed model is verified by comparing the simulated natural frequencies and shock response with the experimental ones. It investigates the displacement and the stress of the most vulnerable component, i.e. a leaf spring due to shock, and it proposes a robust design of leaf spring of a polygon mirror scanner motor against shock.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.9
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• pp.933-941
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• 2014

This paper provides a comparison between the Krylov subspace method (KSM) and modal truncation method (MTM), which are typical projection-based model order reduction methods. The frequency responses are compared to determine the numerical accuracies and efficiencies. In order to compare the numerical accuracies of the KSM and MTM, the frequency responses and relative errors according to the order of the reduced model and frequency of interest are studied. Subsequently, a numerical examination shows whether a reduced order can be determined automatically with the help of an error convergence indicator. As for the numerical efficiency, the computation time needed to generate the projection matrix and the solution time to perform a frequency response analysis are compared according to the reduced order. A finite element model for a car suspension is considered as an application example of the numerical comparison.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.270-278
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• 1997

The purpose of this paper is to evaluate the effectiveness of eigen modes by modal analysis and the application of approximate eigen modes for continuum. This study proposes the appropriate selection technique of eigen modes by modal analysis and the method for the reasonable survey of post-buckling path. And the buckling characteristics of a latticed dome is studied by the application of these approximate eigen modes which have sufficient accuracy and praticallity for response analysis in symmetric and anti-symmetric state of continuous shell. To prove the effectiveness of eigen modes and application of approximate eigen modes for continuum, these results are compared with those of direct method.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.606-617
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• 2000

A dynamic simulation program for pantograph-catenary system is developed based on a mode superposition method to predict current collection performance. Formulations for the dynamic simulation are presented in this paper. The number of modes which should be considered for a KTX catenary system is reviewed through frequency response analyses. The responses for GPU pantograph - KTX catenary system are simulated with various train speeds. The our simulation results are in reasonably good agreements with RTRI simulation program, SNCF simulation program, and BR simulation program.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.33-37
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• 1989

According to the Rayleigh-Ritz approximation method, a solution can be represented as a finite series consisting of space-dependent functions, which satisfy all the geometric boundary conditions of the problem and appropriate smoothness requirement in the interior of the domain. In this paper, an efficient formulation for solving structural dynamics systems in frequency domain is presented. A general procedure called Ritz modes (or vectors) generation algorithm is used to generate the admissible functions, i.e. Ritz modes, Then, the use of direct superposition of the Ritz modes is utilized to reduce the size of the problem in spatial dimension via geometric coordinates projection. For the reduced system, the frequency domain approach is applied. Finally, a numerical example is presented to illustrate the effectiveness of the proposed method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.497-512
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• 2006

In this paper, a simple but effective analysis procedure to estimate seismic capacities of multi-span continuous bridge structures is proposed on the basis of modal pushover analysis considering all the dynamic modes of structure. Unlike previous studies, the proposed method eliminates the coupling effects induced from the direct application of modal decomposition by introducing an identical stiffness ratio and an approximate elastic deformed shape. Moreover, in addition to these two introductions, the use of an appropriate distributed load {P} makes it possible to predict the dynamic responses for all kinds of bridge structures through a simpler analysis procedure. Finally, in order to establish the validity and applicability of the proposed method, correlation studies between rigorous nonlinear time history analysis and the proposed method are conducted for multi-span continuous bridges.