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고유벡터의 변화량에 의한 비례감쇠구조물의 변경질량 및 그 위치 해석
이정윤,Lee, Jung-Youn 한국생산제조학회 2010 한국생산제조학회지 Vol.26 No.2
In spite of a large amount of previous research, detail study on modified mass in proportional damping system is not well understood. It is common to predict structural dynamic design parameters due to the change of mass, but to predict the amount of modified mass and the location where the mass is being modified are rarely found in previous literature. Such inverse problem required detail analytical study in order to understand structural modification in proportional damping system. This paper predicts the modified mass and the modified mass location in proportional damping system using sensitivity coefficients and iterative method. The sensitivity coefficients are obtained from the change of eigenvectors due to mass modification. This method is applied to a horizontal beam and three degree of freedoms system. To validate the predicted changing mass and its location, the obtained results are compared to the reanalysis result which shows good agreement.
설계 변수 변경에 따른 트러스 구조물의 동특성 변화 예측
이정윤(Jung Youn Lee) 대한기계학회 2020 大韓機械學會論文集A Vol.44 No.5
이 연구에서는 변경 질량 및 강성의 크기와 위치를 이용하여 트러스의 동특성 변화를 예측하였다. 이를 위해 반복법을 사용하여 설계 변경량의 비선형 함수인 감도 계수를 구하였다. 이 감도 계수를 이용하여 변경된 트러스의 고유 진동수와 고유 벡터를 변경 전 고유 진동수, 고유 벡터와 질량 및 강성변화만으로 정확히 예측하는 방안을 제시하였다. 이를 검증하기 위해 7bar 트러스에 적용하여 설계 변경 후 고유 진동수와 고유 벡터를 예측한 결과 설계 변경 후 재해석한 결과들과 잘 일치하였다. In this study, the change in dynamic characteristics of the truss with the modified design was predicted using the magnitude and location of the modified mass and stiffness. For this purpose, the iteration method was used to find the sensitivity coefficient which is a nonlinear function of the design change. Using this sensitivity coefficient, we propose a method to accurately predict the eigenvalues and eigenvectors of the modified truss using only the eigenvalues, eigenvectors before modification, mass and stiffness changes. To verify this, we applied the 7 bar truss to predict the eigenvalue and eigenvector after the design change, and the results were in good agreement with the results re-analysis after the design change.
이정윤(Lee, Jung Youn) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.11
A damage in structure alters its dynamic characteristics. The change is characterized by changes in the modal parameter, i.e., modal frequencies, modal damping value and mode shape associated with each modal frequency. Changes also occur in some of the structural parameters; namely, the mass, damping, stiffness matrices of the structure. In this paper, evaluation of changes in stiffness matrix of a structure is presented as a method not only for identifying the presence of the damage but also locating the damage. It is shown that changed stiffness matrix can be accurately estimated a sensitivity coefficient matrix derived from modifying mode shapes, First, with 4 story shear structure models, the effect of presence of damage in a structure on its stiffness matrix is studied. By using these analytical model, the effectiveness of using change of stiffness matrix in detecting and locating damages is demonstrated. To validate the predicted changing stiffness and its location, the obtained results are compared to the reanalysis result which shows good agreement.