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독립성분분석(ICA)법을 이용한 모드특성 추정에 관한 연구
황재승,김재형,Hwang, Jae-Seung,Kim, Jae-Hyung 대한건축학회 2011 대한건축학회논문집 Vol.27 No.5
Independent component analysis (ICA) is a method separating the mixture of signals into statistically and mutually independent ones. It has been applied to not only the Cocktail-party problem but also EEG analysis using the EEG waveform, digital signal processing, image processing and cognitive technique field actively. This study aims to propose a procedure to estimate the modal responses and mode shapes of a structure by using the ICA method from analyzed responses of the structure, which is first attempt to the architecture and civil engineering works field. It is introduced a basic concept of ICA with the fixed-point (FP) algorithm based on secant method and the kurtosis. From the concept of the separation performance of mixed-signal, modal responses and mode shape of a building structure are estimated based on ICA method. For the verification of the ICA method, a numerical simulation is performed. In the simulation, it is assumed that the mode shape and time history of the structural responses had been known through the dynamic analysis and state space analysis of a structure. Then, some parts of responses of the structure are chosen from analysed responses and those are used as input responses to estimated the modal responses and mode shape of a structure by the ICA method. From the numerical results, it is shown that the ICA method can be effectively applied to the mode separation and the estimation of modal properties of structure.
베이지안 필터를 이용한 풍직각방향 하중모델 파라미터 추정
황재승(Hwang, Jae-Seung) 대한건축학회 2021 대한건축학회논문집 Vol.37 No.2
It is known that the across-wind load is mainly consist of three components: the buffeting, Strouhal, and feedback load components. The feedback load can be easily separated from the across-wind load using the structural velocity response and aerodynamic damping ratio. However, it is difficult to quantitatively and independently evaluate the contribution of the buffeting and Strouhal load since the two load components are strongly combined in the across-wind load. In this study, it is proposed a new approach to separate the two load components using Bayesian filtering and to identify the parameters of each mathematical model. This technique consists of a process of estimating the parameters of the mathematical load model, which can be expressed in the form of a transfer function, in the frequency domain using the unscented Kalman filter, and sequentially performing load separation. For the validation of the proposed approach, the aeroelastic model test was performed and wind load was inversely identified from the acceleration response obtained from the wind tunnel test. And then, the proposed technique is applied on the wind load, which shows that the stable parameter estimation of the buffing and Strouhal load, respectively, was reliably peformed.
와류하중 구성성분에 따른 풍직각방향 진동 기여 특성 분석
황재승(Hwang, Jae-Seung) 대한건축학회 2020 대한건축학회논문집 Vol.36 No.7
As the vortices around the structure are transferred to the dynamic wind load, across-wind vibration is induced, and the magnitude of the vibration is larger than the along-wind vibration when the height of the structure is increased. In this study, in order to quantitatively evaluate across-wind response, the vortex-induced load components are classified according to their own original source, and the effect of each component on the vibration is analyzed. The load is identified from the response of the structure by inverse problem, and these load components are obtained by Kalman filtering based on the state equation realized from the distribution characteristics of loads spectrum in the frequency domain. The proposed load decomposition process for vortex-induced load components is verified by performing an aero-elastic model test for the circular cylinder model in the atmospheric boundary layer wind tunnel, and the pattern in which each load component contributes to the across-wind response is analyzed, and finally the original source of the loads as well as the unique behavior of across-wind response can be precisely understood.
상태공간 모드응답을 이용한 고 감쇠 구조물의 동적특성 추정
황재승(Hwang, Jae-Seung) 대한건축학회 2021 대한건축학회논문집 Vol.37 No.8
The diverse vibration control systems have been applied to many structures for the enhancement of the earthquake or wind resistant performance. Since such a heavy damped structure has nonclassical damping natures, it is faced some difficulties in extracting modal response in the monochromatic form and in estimating the modal properties precisely with conventional mode decomposition method developed in physical coordinate. In this study, a state-space based modal decomposition technique is proposed to extract modal response from measured response of a heavy damped structure, and to identify the modal properties using the decomposed modal response in the state space. It is analyzed the characteristics of power spectrum of the decomposed modal response, and then a process to identify the modal properties, particularly the damping ratio is addressed. For the verification of the proposed method, the technique is applied to the 3DOF system with the oil dampers and the structure with a tuned mass damper system. From the simulation results, it is found that the transfer function of the modal response in the state space is composed of a combination the displacement and velocity transfer function, and so more precise modal parameter estimation can be expected when the participation ratio of two components is appropriately addressed.
비고전 감쇠를 가지는 구조물의 가속도응답을 이용한 새로운 모드분리 기법
황재승(Hwang, Jae-Seung) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.1
Dynamic modes of the non-classical damping or very closely distributed modal system are nearly decomposed by using the conventional modal matrix calculated from mass, stiffness matrix because that the damping matrix is unable to be diagonalized with the modal matrix. In this paper, a new mode decomposition technique for a non-classical damping structure in frequency domain is proposed that is using the differential state variables estimated from measured acceleration responses and Kalman filtering to calculate the linear transformation matrix of governing modes. The linear transformation matrix is updated in the optimization process to maximize the performance index cooperated with a power spectral density of a target mode and an averaged power spectrum. For the verification of the proposed method, a numerical simulation for the representative non-classical damping and closely distributed modal system : primary mass-TMD coupled 2DOF system. The results from the simulations show that the proposed technique can estimate the modal response more precisely than a conventional mode decomposition method such as ICA, POD.