• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.2
• /
• pp.271-277
• /
• 2011

An identification method of the structural damping matrix for a steel bar by the genetic algorithm is proposed. Supposing the damping matrix were in proportion to the stiffness matrix, the proportional factors can be identified from the curve fitting of the experimental frequency response function(FRF) by the genetic algorithm. Applying the identified damping matrix to FEM of a beam model, the values of the objective function could be reduced to about 1/60 in comparison with conventional FEM model without damping. The damping matrices of some sub-structures which have large damping partly could be identified by the algorithm, and they could be used as some parts of the FEM model for a whole structure.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.4 no.2
• /
• pp.47-56
• /
• 2000

지반-구조물 상호작용 시스템 구조물의 진동제어 시스템 복합재료 구조물과 같은 비비례 감쇠 구조물의 경우 정확한 동적응답을 얻기 위해서는 감쇠행렬을 고려한 고유치 문제를 계산하는 것이 필수적이다 그러나 대부분의 고유치 해법에서는 구하고자 하는 고유치 중 일부를 누락시킬 수 있기 때문에 어떤 고유치 해법이 실제문제에 응용 가능한 방법이 되기 위해서는 누락된 고유치의 존재 여부를 검사하는 기법을 포함하고 있어야만 한다. 비감쇠나 비례감쇠 시스템의 경우에는 널리 알려진 Sturm 수열성질을 이용하여 누락된 고유치를 쉽게 검사할 수 있는 반면에 비비례 감쇠 시스템의 경우에는 널리 알려진 Sturm 수열 성질을 이용하여 누락된 고유치를 쉽게 검사할 수 있는 반면에 비비례 감쇠 시스템의 경우에는 아직까지 검사 기법이 개발되어 있지않다 본 논문에서는 편각의 원리를 이용하여 감쇠행렬을 고려한 고유치 문제의 누락된 고유치의 존재여부를 검사하는 기법을 제안하였다 제안방법의 효용성을 검증하기 위하여 두가지 수치예제를 고려하였다.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.1 no.3
• /
• pp.11-19
• /
• 1997

In this paper, an efficient dynamic analysis method of a building structure with viscoelastic dampers is proposed. Viscoelastic dampers are used for the purpose of controlling vibration of buildings. The matrix condensation technlque based on the rigid diaphragm assumption is not readily applicable for building structures with viscoelastic dampers. An improved procedure for damping matrix condensation is employed in the proposed method to increase the efficiency of analysis. Efficiency and accuracy of the proposed method are verified through analysis of an example structure.

• Computational Structural Engineering
• /
• v.11 no.1
• /
• pp.171-178
• /
• 1998

The added viscoelastic dampers increase damping and stiffness of buildings and results in so called non-classical or non-proportional damping problem. In this system the eigenvectors of the undamped system may not diagonalize the damping matrix, and the system is generally analyzed by converting the equation of motion into a 2n first order state-space form. As this approach is complex and time-consuming compared to the classically damped problem, the system is often analyzed by neglecting the off-diagonal terms in the damping matrix. In this paper the theoretical background of the approximate approach is studied, and the vibration characteristics of a three-story shear building with a viscoelastic damper are investigated using the exact and approximate method. It is found that the approximate method may produce good result when the additional damping is small, but as the damping increases the error also increase.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.12
• /
• pp.1243-1249
• /
• 2012

Finite element models are updated in two stages in this paper. In the first stage, damping is neglected, and mass and stiffness matrices of a finite element model are updated using an optimization technique. The objective function for optimization consists of natural frequencies and mode shapes obtained from experimental modal testing data and finite element analysis. In the second stage, damping is considered with the mass and stiffness matrices fixed. A damping matrix is estimated assuming a proportional damping system. Then the damping matrix is adjusted using an optimization process so that the difference between the analytical and measured frequency response functions becomes minimum. This procedure of model updating has been applied to a simulated system and an experimental cantilever beam.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.4
• /
• pp.369-373
• /
• 2016

Accurate identification of damping matrix in structures is very important for predicting vibration responses and estimating parameters or other characteristics affected by energy dissipation. In this paper, damping matrix identification method that use normal frequency response functions, which were estimated from complex frequency response functions, is proposed. The complex frequency response functions were obtained from the experimental data of the structure. The nonproportional damping matrix was identified through the proposed method. Two numerical examples (lumped-mass model and cantilever beam model) were considered to verify the performance of the proposed method. As a result, the damping matrix of the nonproportional system was accurately identified.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.8 no.2
• /
• pp.45-53
• /
• 2004

In this paper, the stiffness and damping matrix are experimentally constructed using the structural modal information on frequencies, damping ratio and modal vectors, which are obtained by shaking table tests. Free vibration, harmonic and white noise vibration tests are performed. The acceleration of the shaking table was used as the input signal, and the corresponding accelerations of each floor were measured as output signals. The characteristics and limitations of modal information from each test are compared. The results of this study would be a basic resource of the analytical and experimental studies on the system identification of structures.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.10
• /
• pp.1021-1027
• /
• 2009

Finite element models of dynamic systems can be updated in two stages. In the first stage, mass and stiffness matrices are updated neglecting damping. In the second stage, a damping matrix is estimated with the mass and stiffness matrices fixed. Methods to estimate a damping matrix for this purpose are proposed in this paper. For a system with proportional damping, a damping matrix is estimated using the modal parameters extracted from the measured responses and the modal matrix calculated from the mass and stiffness matrices from the first stage. For a system with non-proportional damping, a damping matrix is estimated from the impedance matrix which is the inverse of the FRF matrix. Only one low or one column of the FRF matrix is measured, and the remaining FRFs are synthesized to obtain a full FRF matrix. This procedure to obtain a full FRF matrix saves time and effort to measure FRFs.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.7
• /
• pp.99-106
• /
• 1995

Frequency response functions are of great use in dynamic analysis of structural systems. The present paper proposes an efficient method for computation of the frequency rewponse functions of linear structural dynamic models with a sparse, non-proportional damping matrix. An exact condensation procedure is proposed which enables the present method to condense the matrices without resulting in any errors. Also, an iterative scheme is proposed to be able to avoid matrix inversion in computing frequency response matrix. The proposed method is illustrated through a numerical example.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.4
• /
• pp.671-679
• /
• 1999

건물의 진동에너지 소산능력을 향상하기 위하여 점탄성감쇠를 설치하게 되면 이른바 비비례 감쇠시스템이 되어 구조물은 복소수형태의 고유모드와 고유치를 가진다. 복소모드중첩법은 이러한 복소모드를 이용하여 중첩함으로써 비비례 감쇠시스템 구조물의 정확한 동적 거동을 얻을 수 있는 방법이다. 그러나 건물이 고층화되면 많은 자유도로 인하여 고유치해석 및 모드중첩과정에서 많은 시간과 노력이 필요하게 된다. 본 논문에서는 효율적인 구조물의 모형화를 위하여 강막가정과 행렬응축기법을 적용하였다. 또한 몇 개의 주요 모드만을 선택하여 중첩하는 방법에 대하여 연구하였으며 구조물의 진동에 영향을 주는 모드의 선택을 위한 복소모드 응답참여계수를 제안하였다. 제안된 해석방법의 정확성과 효율성을 검토하기 위하여 예제 구조물을 대상으로 해석한 결과, 응답의 정확성을 유지하면서 해석에 필요한 시간을 대폭 절감할 수 있었다.