• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.1
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• pp.57-63
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• 2003

A comparative study was performed for a suspension bridge to grasp the possible differences in seismic responses evaluated by several analytical methods. The items mainly investigated are the linear vs. nonlinear response, the response spectrum method vs. the linear dynamic analysis method, and the damping ratio and it's implementation into analysis procedures. According to the numerical example, it is found that the seismic responses are considerably affected by the damping-related parameters even though slight differences are shown depending on the response quantities and the exciting directions. On the other hand, it is also confirmed that the seismic responses are less affected by the analysis method-related parameters such as the response spectrum method vs. the linear dynamic analysis method, and the linear and nonlinear analysis method. The response spectrum method is expected to give conservative results for the examined bridge, provided that the design response spectrum in the Korean Highway Design Specification is modified according to the proper damping ratio.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.117-120
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• 1993

기게공업의 근간이라고 할 수 있는 공작기계산업은 첨단산업과 관련한 소재공업의 고도화에 따라 고속 고능률화 및 고정밀화 하여 가는 추세에 있으며 이에대한 성능향상 요구는 앞으로도 계속적으로 이어질것이다. 여기서 공작기계의 가공정밀도 및 가공 능률에 결정적인 영향을 주는 요소는 대부분 주축유닛트 부분이며 최근과 같이 고속 고정밀과 유연성을 추구하는 공작기계에서 주축 시스템이 수행하는 역할이란 매우 중요한 위치를 갖는다. 본 연구는 모터내장형 주축시스템에 관해 정.동적측면에서의 구조설계와 시제품에 대한 평가를 수행하여 활용측면에서의 신뢰성을 높일 수있도록 하는 것을 주요 내용으로 하였다. 즉 연구의 첫단계로서 정적인 측면에서의 구조설계를 하여 연구모델을 결정하였으며 다음단계로서 설정된 구조모델에 대해 유한요소 법(FEM)을 이용한 동적해석을 실시하고 실험해석에 의한 이론해석 과정의 수학적모델을 수정,보완한후 고속회전에서의 동적특성을 실제 현상에 가깝도록 예측하여 설계단계에서의 고속운전특성이 주축계의 동적안정성에 미치는 여러 영향등에 관해 고찰하였다.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.117-126
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• 2001

도로교의 대표적인 기초형식인 말뚝기초에 대한 내진설계방법으로 여러 가지 방법들이 제안되어 있다. 이 중 동적해석법과 같은 복잡한 절차에 의한 해석은 적용성에 한계가 있을 수 있고, 실무에서의 적용상 많은 어려움이 예상되었다. 본 연구에서는 등가정적해석법을 이용한 도로교 기초 말뚝에 대한 간편한 내진설계절차를 제안하였으며, 사례에 적용하였다. 또한, 제안된 간편한 내진설계절차에 사용할 수 있는 해석코드의 적용성을 확인하기 위하여 수식적 정해에 의한 계산결과를 기준 값으로 하여 해석코드에 의한 해석결과들을 비교.분석하였다. 또한, 지진 진동을 이용한 동적 해석결과와 SPS 상호작용(Superstructure - pile - soil interaction)을 고려한 해석결과를 수식적 정해에 의한 결과와 비교.분석하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.213-219
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• 2006

Topology optimization problem requires numerous repeated evaluations of objective function and design sensitivity for elements within design domain with various density distributions. The recently proposed two-level condensation scheme(TLCS) is very promising for the construction of reduced system and for an accurate and efficient analysis concerned about eigenvalue and dynamic problems. We used the two-level dynamic condensation scheme for the analysis and sensitivity computation part in the structural topology optimization problem. The results of the topology optimization for the reduced system show the TLCS provides high accuracy and computation efficiency compared to the full scale system within engineering accuracy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.105-111
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• 2013

The spindle is the main component in machine tools. The static and dynamic characteristics of the spindle directly affect the machining accuracy of workpieces. The characteristics of the spindle depend on the shaft size, bearing span, built-in motor location, and so on. Therefore, the appropriate selection of these parameters is important to improve the spindle characteristics. This paper presents the analysis of the static and dynamic characteristics and optimization design of a 40,000-rpm high-speed spindle. Statistical analysis for optimization and finite element analysis were performed. This study uses the response surface method to optimize the objective function and design factors. The targets are the natural frequency and displacement. The design factors are the shaft length, shaft diameter, bearing span, and motor location. The optimized design provides better results than the initial model, and these results are expected to improve the static and dynamic characteristics of the spindle.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.33-39
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• 2010

This study develops an approximate procedure for incremental dynamic analysis (IDA) using modal pushover analysis (MPA) with empirical equations of the inelastic displacement ratio ($C_R$) and the collapse strength ratio ($R_C$). By using this procedure, it is not required to conduct linear or nonlinear response history analyses of multi- or single- degree of freedom (MDF) systems. Thus, IDA curves can be effortlessly obtained. For verification of the proposed procedure, the 6-, 9- and 20-story steel moment frames are tested under an ensemble of 44 ground motions. The results show that the MPA-based IDA with empirical equations of $C_R$ and $R_C$ produced accurate IDA curves of the MDF systems. The computing time is almost negligible compared to the exact IDA using repeated nonlinear response history analysis (RHA) of a structure and the original MPA-based IDA using repeated nonlinear RHA of modal SDF systems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.1
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• pp.79-87
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• 2013

An isogeometric topological shape optimization method is developed using the level sets and Heaviside enrichments. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set functions, which facilitates to handle complicated topological shape changes. The Heaviside enrichment improves the isogeometric analysis by adding some enrichment functions to model the internal boundaries. The proposed topological shape optimization method has several benefits: exact geometric models can be obtained using the isogeometric approach and the limitation of tensor-product patches can be overcome using the Heaviside enrichments to represent the internal voids. Even in a single patch, discontinuous displacement fields as well as smooth stress field can be obtained. Since the level sets offer the implicit moving boundary inside the domain, it is easy to represent the topological shape variations in the isogeometric analysis using Heaviside enrichments.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.121-122
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• 2007

본 연구는 유한 길이를 갖는 솔레노이드 내에 원통형 도체가 존재하는 경우, 코일에 펄스 전압을 인가했을 때 정적, 동적 특성을 고찰하였다. 또한 솔레노이드 내에 자속을 한 부분으로 집중시켜주는 B-field shaper를 삽입하여 같은 방법으로 펄스 전류 인가시의 정적, 동적 특성을 고찰하였다. 원통형 도체의 재질로는 Al, Cu, Fe 계열을 사용하였으며, 인가 전압은 고압용 콘덴서를 충전하여 수백 micro sec 단위의 짧은 시간에 통전하였다. 본 논문에서는 유한 길이 솔레노이드는 설계 기본 방법을 제시하였고, 설계된 시작품에 대한 동적특성 해석은 유한요소법을 이용하여 검증하였다. 해석결과로는 현상에 따른 솔레노이드 내의 원통 도체에 작용하는 자기력 분포, 인덕턴스 등 설계 변수에 대한 자기력 특성 값을 제시하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.27-36
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• 2020

The purpose of this paper is to study on the applicability of the standard design response spectrum from the response spectrum analysis method, mainly applied to pile mooring facilities. To this end, after performing the ProShake 1-dimensional site response considering various geological conditions, the current standard design response spectrum was compared, and the ground-pile model in time history and two-dimensional site response analysis using Abaqus were performed to analyze the dynamic behavior of the ground-pile and to examine the selection method of the reference surface of the response spectrum on the installed slope, respectively. As a result, it was confirmed that no problems were found in the applicability of the current standard design response spectrum and no improvements are needed as well when considering the characteristics of the ground-pile dynamic behavior and the slope of the pile mooring facility.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.99-106
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• 2006

The Real-Time Hybrid Test system presented in this paper is based on the pseudodynamic test method, and it combines physical testing with model-based simulation. The system is designed to achieve a rate of loading that is significantly higher than that of a conventional pseudodynamic test approaching the real-time response of a structure subjected to earthquake loads. To provide robust computation environment for the analysis of many degree-of-freedom structures, the system adopts an implicit time integration scheme in the model-based simulation. This paper presents an overview of the developed system and numerical simulations that were conducted to evaluate the performance of the computation scheme adopted here. Results of these studies have demonstrated the good performance of the computation scheme for real-time multiple-degree-of-freedom tests.