• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.665-668
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• 2008

The load distribution to each mode of a structure under seismic loading depends on the modal participation factor. The factor of an idealized analytical model, however, is different to the actual one due to modeling and construction error. Therefore, there exist limits on the estimation of actual behavior. In this study, an identification procedure for participation factor based on vibration test is proposed. The procedure has an advantage that the mode shape vector can also be estimated directly from the participation factor. The numerical simulation using a three story building is performed to evaluate the proposed procedure.

• Smart Structures and Systems
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• 제17권3호
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• pp.413-429
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• 2016

The recent research on proper orthogonal decomposition (POD) has revealed the linkage between proper orthogonal modes and linear normal modes. This paper presents an investigation into the modal identifiability of an instrumented cable-stayed bridge using an adapted POD technique with a band-pass filtering scheme. The band-pass POD method is applied to the datasets available for this benchmark study, aiming to identify the vibration modes of the bridge and find out the so-called deficient modes which are unidentifiable under normal excitation conditions. It turns out that the second mode of the bridge cannot be stably identified under weak wind conditions and is therefore regarded as a deficient mode. To judge if the deficient mode is due to its low contribution to the structural response under weak wind conditions, modal coordinates are derived for different modes by the band-pass POD technique and an energy participation factor is defined to evaluate the energy participation of each vibration mode under different wind excitation conditions. From the non-blind datasets, it is found that the vibration modes can be reliably identified only when the energy participation factor exceeds a certain threshold value. With the identified threshold value, modal identifiability in use of the blind datasets from the same structure is examined.

• Nuclear Engineering and Technology
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• 제36권4호
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• pp.364-373
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• 2004

This study investigates the fluidelastic instability characteristics of helical steam generator type tubes used in operating nuclear power plants. To obtain a natural frequency, corresponding mode shape, and participation factor, modal analyses using various conditions are performed for helical type tubes. Investigated are the effects of the number of turns, the number of supports, and the status of the inner fluid on the modal and fluidelastic instability characteristics of the tubes, which are expressed in terms of the natural frequency, the corresponding mode shape, and the stability ratio.

• Wind and Structures
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• 제14권3호
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• pp.239-252
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• 2011

The wind-induced mean, background and resonant responses of Beijing National Stadium are investigated in this paper. Based on the concepts of potential and kinetic energies, the mode participation factors for the background and the resonant components are presented and the dominant modes are identified. The coupling effect between different modes of the resonant response and the coupling effect between the background and resonant responses are analyzed. The coupling effects between the background and resonant components and between different modes are found all negligible. The mean response is approximately analogous to the peak responses induced by the fluctuating wind. The background responses are significant in the fluctuating responses and it is much larger than the resonant responses at the measurement locations.

• 대한기계학회논문집A
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• 제37권3호
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• pp.325-331
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• 2013

본 논문에서는 상용 프로그램 ABAQUS를 이용하여 브레이크 시스템의 불안정 모드를 알아보기 위한 복소고유치해석을 수행하였다. 또한 전체 시스템의 불안정 복소 고유모드에서 가장 진동에너지가 큰 부품을 알아보기 위한 기여도해석과 전체 복소 고유모드와 해당 부품의 부품모드간의 기여도해석을 통해 모드 연성의 가능성이 높은 모드를 알아보았다. 본 연구에서는 디스크 로터의 2차 굽힘모드와 토크멤버의 3차 축방향 횡모드의 연성에 의해 1.4kHz의 불안정 모드가 발생하는 것을 알 수 있었다. 이러한 모드 연성을 차단하기 위해 불안정성을 유발하는 토크멤버에서 해당모드의 주파수 변화에 대한 감도 해석을 실시하였다. 감도 해석 결과를 토대로 질량 가중에 의한 구조물 동특성 변경을 수행한 결과 저주파 영역에서 불안정 모드가 발생하지 않아 본 연구에서 제시된 저감방법의 유효성을 확인할 수 있었다.

• Nuclear Engineering and Technology
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• 제35권5호
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• pp.442-453
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• 2003

This study investigates the safety assessment of the potential for fretting-wear damages on steam generator (SG) U-tubes caused by foreign object in operating nuclear power plants. The operating SG shell-side flow field conditions are obtained from three-dimensional SG flow calculation using the ATHOS3 code. Modal analyses are performed for the finite element modelings of U-tubes to get the natural frequency, corresponding mode shape and participation factor. The wear rate of U-tube caused by foreign object is calculated using the Archard formula and the remaining life of the tube is predicted. Also, discussed in this study is the effect of the flow velocity and vibration of the tube on the remaining life of the tube.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.36-43
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• 1998

The purpose of study is to propose numerical assessment methods of lateral deformation shape under lateral loads for regular high-rise buildings. The normalized 1st mode shape is used to assess lateral deformation shape. The assessment method are mass participation factor, representative value by RMS, the mean value, median of the nomalized 1st mode shape. These methods are able to know a fundamental lateral deformation shape of the building and effects of interactive systems numerically. Generally the characteristics of normalized 1st mode shape for various models coincide with numerical assessment results.

• 대한기계학회논문집A
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• 제34권11호
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• pp.1773-1778
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• 2010

본 논문은 원자력 내진등급 원전용 주냉각수 펌프의 지진하중에 대한 구조 건전성을 코드에 따라 평가하였다. 펌프 구조물을 3차원 모델링하여 유한요소법을 사용하여 모달 해석 및 응답스펙트럼 해석을 수행하였다. 모달 해석 결과 고유진동수, 모드형상 및 모드참여계수를 얻을 수 있었다. 응력해석에서 구한 응력들을 조합하여 원자력 규격집에서 제시한 허용응력과 비교하여 펌프의 구조 건전성을 판단하였다. 모든 지진하중에 대한 펌프 구조물에서의 응력은 허용값 보다 작게 분포하므로 구조적 건전성을 유지한다고 평가할 수 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1994년도 추계학술대회논문집; 한국종합전시장, 18 Nov. 1994
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• pp.288-294
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• 1994

A study of prediction and qualification techniques for structure borne booming noise is presented in this paper. Result from acoustic normal mode finite element analysis of a 1/2 size vehicle cavity sample model is compared to the that from an experiment. Coupled structural-acoustic analysis is performed on a 1/4 size vehicle cavity sample model surrounded by 2 mm thick normal steel plates. Interior noise levels around passensger's ear position are predicted and reduced by structural modification based on panel participation factor analysis about the sample cavity model. Futhermore, optimization technique in application of anti-vibration pad is studied.

• 전산구조공학
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• 제9권4호
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• pp.209-217
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• 1996

구조물의 손상전후에 나타나는 고유진동수와 모드 형상으로 부터 Inverse Modal Perturbation기법을 이용하여 잔교식 부두나 돌핀과 같은 대규모 항만구조물의 손상도 추정을 위한 모드 기여도 계수를 근사적으로 직접 구하는 방법을 제시하였다. 잔교식 항만구조물의 고유치 해석을 통해 구조물의 강성 변화량과 구조물의 고유진동수와 모드 형상의 변화량과 요소 손상도 계수를 도입하여 Inverse Modal Perturbation의 2차항을 고려한 관계식을 유도하고 손상전후에 구조물의 강성 감소로 나타나는 구조물의 손상도를 추정하여 수렴정도를 고찰하였다.