• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.31-34
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• 2010

본 논문에서는 교량의 자유진동 모드의 중첩원리를 이용하여 KTX-교량의 동적상호작용 해석법을 제시한다. 이를 위하여 모드중첩법에 기초한 3차원 교량-차량의 에너지 식으로부터 에너지원리를 적용하여 교량과 차량의 상호작용을 고려할 수 있는 운동방정식을 유도한다. 이때 운동방정식의 해는 Newmark-${\beta}$ 방법을 사용한다. 그리고 궤도의 불규칙성은 FRA의 6등급 분류규정을 고려하여 각 등급별로 고속철도의 열차속도에 따르는 응답을 분석한다. 실제 고속철도에 사용되는 PSC 박스형 교량을 상용프로그램(MIDAS)를 이용하여 모델링하고 그로부터 각 모드별 형상을 얻어내어 본 논문에서 개발한 열차-교량 상호작용 프로그램에 입력하여 상호작용 해석을 수행한다.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.479-485
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• 2002

We propose a vector analysis for designing multimode-interference power splitters, which can show an arbitrary splitting ratio. Power splitting is a fundamental characteristic in integrated optical circuits and its value would be multiplied for many applications if the splitting ratio could be selected freely. Since the vector analysis utilizes a graphical method based on the previously-reported mathematical results of multimode interference, it shows an excellent advantage especially for designing power splitters with an arbitrary splitting ratio.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.87-96
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• 1999

To analyze the dynamic behavior of structure, direct integration and mode superposition may be utilized in time domain analysis. As finite number of frequencies can give relatively exact solutions, mode superposition is preferable in analyzing structural behavior. In non-linear analysis, however, mode superposition is seldom used since time-varying element stiffness changes stiffness matrix, and the change of stiffness matrix leads to the change of essential constants - natural frequencies and mode shapes. In spite of these difficulties, there are some attempts to adopt mode superposition because of low cost compared to direct integration, but the result is not satisfactory. In this paper, a method using mode superposition in non-linear analysis is presented by separating local element stiffness from global stiffness matrix with the difference between linear and non-linear restoring forces to the external force vectors included. Moreover, the hysteresis model changing with the relative deformation in each floor makes it possible to analyze non-linear behavior of structure. The proposed algorithm is applied to shear beam model and the maximum displacement is compared with the result using direct integration method.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.54-60
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• 2000

There are many works to analyze a simple expansion chamber involving higher order modes. These works are classified to mode matching method, velocity potential method and finite element method. Among these methods, mode matching method has good performance at analyzing a concentric expansion chamber. Generally inlet/outlet pipe cross section area is smaller than middle chamber cross section area. So the number of higher order modes of inlet/outlet pipe can be fewer than that of middle chamber. But mode matching method must use the same number of higher order modes at inlet pipe, middle chamber and outlet pipe. Therefore the redundant modes of inlet/outlet pipe makes the computation time of mode matching method longer. In this paper, the new method, which can select number of each higher order modes of inlet pipe, middle chamber and outlet pipe, was suggested. And this method was compared to conventional mode matching method and finite element method in order to demonstrate the accuracy of the new method and to show that the new method can reduce a calculating time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.621-629
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• 1998

Propagation characteristics of electromagnetic waves in lossy tunnels are analysed using Finite Element Method with edge basis function. According to the analysis lossy dielectric wall on the tunnel highly affects the characteristics of the waves in the tunnel. Also higer modes are separated using mode orthogonality principle, and the propagation characteristics of higer modes are investigated. To verity the numerical results, miniatures of the tunnels are constructed and measurements of the waves are accomplished.

• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.10-18
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• 1999

본 논문에서는 대형구조물의 해석에 있어서 부분구조합성법과 섭동법을 이용하여 복잡한 비선형시스템의 해석방법을 제안하였다. 해석방법은 전체시스템을 먼저 몇 개의 분계로 분할한다. 각 분계의 운동방정식에 비선형항이 존재하여도 전체시스템의 지배적 진동모드는 선형모드라는 가정하에 이 시스템의 각 분계를 모드좌표로 변환한다. 이때, 비선형항은 근사적으로 변환한다. 그리고 섭동법을 이용하여 각 분계의 모드좌표방정식은 섭동좌수별로 정식화되어 순차적으로 구해진다. 비선형의 감도는 비선형계수로 정의되고, 그에 상응하는 강성에 의해 구해진다. 제안된 해석방법으로 비선형회전체, 비선형 베어링-페데스탈로 구성된 대형시계구조물의 진동을 해석하였다. 해석방법의 유효성을 평가하기 위해 응답의 정도와 계산소요시간을 유한요소법의 결과와 비교 분석하였다.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.625-635
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• 1997

The base isolation technique and its benefits in reducing the transmitted earthquake energy into a structure have gained increasing recognition during the last two decades. Unfortunately, the current available design procedures, especially for base-isolated bridges, seem inadequate and too restrictive. As a result, practical design procedure still relies upon a series of deterministic time history analyses. In this study, the evaluation of the possibility of the normal mode method to predict the nonlinear seismic responses of base isolated bridges has been performed. The applicability has been examined through the numerical approach with isolator's elastic or plastic states of the base isolated bridges. Numerical results show that the 1st. mode period and the various responses are varied with the state but are conversed. And, the result show that the normal mode method is applicable to predict the seismic responses and to design the babe isolated bridge. Various analysis method to bridges with bilinearized hysteresis isolator and various pier heights are evalulated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.739-742
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• 2011

일반적으로 고층건물이나 교량 등의 지진하중 하에서의 내진 성능 향상을 위해서는 과도지진해석을 수행하는 것이 필요하다. 본 논문에서는 이러한 지진해석을 수행하는데 Krylov 부공간 축소기법을 이용하는 것을 제안하고 기존의 모드중첩법을 이용한 축소기법과 비교하였다. 해석에서 지진하중은 El Centro Earthquake (1940)의 데이터를 이용하였으며 고층건물 모델을 이용하여 두 방법을 정확성과 효율성 측면에서 비교한 수치결과를 제시하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.162-168
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• 2008

In this paper, the RCF(Resistive Companion Form) analysis method is applied to analyze small signal stability of power systems including thyristor controlled FACTS(Flexible AC Transmission System) equipments such as TCSC(Thyristor Controlled Series Capacitor). The eigenvalue sensitivity analysis algorithm in discrete systems based on the RCF analysis method is presented and applied to the power system including TCSC. As a result of simulation, the RCF analysis method is very useful to precisely calculate the variations of eigenvalues or newly generated unstable oscillation modes after periodic switching operations of TCSC. Also the eigenvalue sensitivity analysis method based on the RCF analysis method enabled to precisely calculate eigenvalue sensitivity coefficients of controller parameters about the dominant oscillation mode after periodic switching operations in discrete systems. These simulation results are different from those of the conventional continuous system analysis method such as the state space equation and showed that the RCF analysis method is very useful to analyze the discrete power systems including periodically operated switching equipments such as TCSC.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.65-75
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• 2006

Nonlinear pushover analysis is used to evaluate the earthquake response of building structures. To accurately predict the inelastic response of a structure, the prescribed story load profile should be able to describe the earthquake force profile which actually occurs during the time-history response of the structure. In the present study, a new modal combination method was developed to predict the earthquake load profiles of building structures. In the proposed method, multiple story load profiles are predicted by combining the modal spectrum responses multiplied by the modal combination factors. Parametric studies were performed far moment-resisting frames and walls. Based on the results. the modal combination factors were determined according to the hierarchy of each mode affecting the dynamic responses of structures. The proposed modal combination method was applied to prototype buildings with and without vertical irregularity. The results showed that the proposed method predicts the actual story load profiles which occur during the time-history responses of the structures.