가속도응답과 ICA 기법을 이용한 구조물의 모드특성 및 하중 동시추정기법

황재승(Hwang, Jae-Seung) 대한건축학회 2014 大韓建築學會論文集 : 構造系 Vol.30 No.2

In this paper, a new system-force identification technique in frequency domain is proposed that is simultaneously to estimate the natural frequency, damping ratio and external modal load by back-calculation from the Kalman filter and the acceleration responses of building structure. The technique is a kind of output-only system identification method to predict the dynamic properties of governing modes separated by applying independent component analysis to the measured acceleration responses and then by minimizing the performance index cooperated with a power spectral density and its derivative of estimated modal load by Kalman filter and the corresponding modal responses. For the verification of the proposed method, a numerical simulation for SDOF system and an application for in-situ measurement data were performed. The results from the simulations show that the proposed technique can estimate the modal properties and modal load more precisely than a conventional output-only subspace identification technique. Because the damping ratio obtained by the proposed technique has a some variations depending on the number of sections for averaging and a duration time in the process of in-situ measurement, so it needs a profound research and additional verification process for more stable estimation of damping ratio.

High-order, closely-spaced modal parameter estimation using wavelet analysis

Thai-Hoa Le,Luca Caracoglia 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.3

This study examines the wavelet transform for output-only system identification of ambient excited engineering structures with emphasis on its utilization for modal parameter estimation of high-order and closely-spaced modes. Sophisticated time-frequency resolution analysis has been carried out by employing the modified complex Morlet wavelet function for better adaption and flexibility of the timefrequency resolution to extract two closely-spaced frequencies. Furthermore, bandwidth refinement techniques such as a bandwidth resolution adaptation, a broadband filtering technique and a narrowband filtering one have been proposed in the study for the special treatments of high-order and closely-spaced modal parameter estimation. Ambient responses of a 5-story steel frame building have been used in the numerical example, using the proposed bandwidth refinement techniques, for estimating the modal parameters of the high-order and closely-spaced modes. The first five natural frequencies and damping ratios of the structure have been estimated; furthermore, the comparison among the various proposed bandwidth refinement techniques has also been examined.

ICA기법을 이용한 실구조물의 모드특성 추정에 관한 연구

박성철,황재승,이상현 대한건축학회지회연합회 2013 대한건축학회연합논문집 Vol.15 No.2

독립성분분석(ICA)은 미지의 신호원으로부터 측정된 신호를 분리하기 위한 비감독화 선형 변환법으로 알려져있다. 본 논문의 목표는 ICA기법에 기초한 응답기반 시스템 식별과 현장 구조물에 적용 가능성을 확인하는 것이다. 구조물에 태풍이 접근할 때 구조물의 상부에 설치된 3개의 가속도계로부터 가속도 응답을 직접적으로 측정된다. 측정된 가속도 응답은 구조물의 모드와 밀접히 관련되어 병진-비틀림이 연계되어 나타난다. 모드분리를 위한 성능지수로서 첨도를 최소화하기위해 ICA기법을 적용하여, 병진-비틀림이 연계된 모드 응답은 밀접하게 인접한 모드일지라도 정확하게 분리되고 변환행렬에 의해 자동적으로 모드 형상은 결정되어지는 것을 확인하였다. 본 연구 결과로부터 고유진동수와 같은 모드 특성은 힐버트 변환에서 얻은 각 모드의 시변 고유진동수의 누적 분포 함수로부터 추계학적으로 추정할 수 있다. 본 논문의 결과는 새롭게 제안된 기법이 기존의 응답기반 시스템 식별보다 구조물의 응답에 매우 강력하게 적용되는 것을 보여준다.

Output-only structural damage detection under multiple unknown white noise excitations

Pinghe Nia,Xiaojuan Wang,Hongyuan Zhou 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.3

Most of the existing output-only damage detection methods require the number of sensors should be larger than the number of unknown excitation force, and the force location should be available. This paper presents a novel output-only damage detection method without these requirements. The proposed method is based on the correlation function of acceleration responses. When the structure is under white noise excitations (or ambient excitations), the correlation function of acceleration responses can be treated as free vibration responses with unknown initial conditions. The unknown structural parameters and initial conditions can be simultaneously identified by minimizing the difference between the measured and calculated correlation functions. The unknown initial conditions are identified with state space method and the unknown structural parameters are updated with sensitivity method. Numerical studies of a 2D truss and a five-bay 3D frame structure are conducted to demonstrate the accuracy, effectiveness, and robustness of the proposed method. Experimental studies on an eight-floor steel frame are further carried out. Results show that the proposed method is not only insensitive to environmental noise but also applicable when the number of sensors is less than that of unknown excitations. Also, the proposed method can be used for damage detection when the force location is unknown.

가상의 단자유도 질량동조기를 이용한 진동수 영역에서의 구조물의 모드특성 추정

황재승(Hwang, Jae-Seung) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.6

The aim of this study is to propose a new output-only system identification technique using a virtual 1-DOF mass tuner(VMT) which is analogous to the tuned mass damper and has a characteristics to amplify the response of the measured acceleration responses of building structure. The VMT is a kind of modal filter that its response is maximized in the range of the natural frequency of a structure, and damping ratio of the structure can be identified using the response ratio of VMT at the different damping ratios consisting the VMT. Also, it is shown that the modal parameters can be precisely estimated if the VMT were applied to the mode response separated with mode decomposition method in the state space. For the verification of the proposed technique, the identification process is applied to the measured acceleration responses from 40 story steel frame structure when typhoon approached to the building. From the numerical simulation, it is found that the modal responses are well separated in the state space, the modal parameters are precisely identified with the proposed modal property estimation method.

독립성분분석(ICA)법을 이용한 병진-비틀림 연계된 구조물의 모드분리 및 응답기반 시스템식별

강경수(Kang Kyung-Soo),김홍진(Kim Hong-Jin),황재승(Hwang Jae-Seung) 대한건축학회 2012 大韓建築學會論文集 : 構造系 Vol.28 No.2

The response of a lateral-torsionally coupled structure subject to dynamic wind loads can include the response for the along wind direction as well as that of the across and torsional directions. This study aims to propose a procedure to separate the modal responses from the lateral-torsionally coupled structural responses by using the independent component analysis(ICA) method and to effectively estimate the dynamic properties from the separated modal responses. The wind loads for the dynamic analysis of structure are generated from Karman wind speed spectrum for the along wind direction and an empirical overturning moment spectrum for the across wind direction. The kurtosis is introduced as the performance index for the mode separation by ICA. For the verification of the proposed method, a numerical simulation is performed. In the simulation, it is found that the lateral-torsionally coupled modal response can be separated precisely by ICA technique and very closely located modes can be also separated. From the numerical results, it is also shown that the modal properties such as natural frequencies and damping ratios are estimated effectively using the Hilbert transform and curve fitting, respectively. The results in this study show that the proposed method can be very usefully applied to the output-only system identification.

독립성분분석(ICA)법을 이용한 병진-비틀림 연계된 구조물의 모드분리 및 응답기반 시스템식별

강경수,김홍진,황재승,Kang, Kyung-Soo,Kim, Hong-Jin,Hwang, Jae-Seung 대한건축학회 2012 대한건축학회논문집 Vol.28 No.2

The response of a lateral-torsionally coupled structure subject to dynamic wind loads can include the response for the along wind direction as well as that of the across and torsional directions. This study aims to propose a procedure to separate the modal responses from the lateral-torsionally coupled structural responses by using the independent component analysis(ICA) method and to effectively estimate the dynamic properties from the separated modal responses. The wind loads for the dynamic analysis of structure are generated from Karman wind speed spectrum for the along wind direction and an empirical overturning moment spectrum for the across wind direction. The kurtosis is introduced as the performance index for the mode separation by ICA. For the verification of the proposed method, a numerical simulation is performed. In the simulation, it is found that the lateral-torsionally coupled modal response can be separated precisely by ICA technique and very closely located modes can be also separated. From the numerical results, it is also shown that the modal properties such as natural frequencies and damping ratios are estimated effectively using the Hilbert transform and curve fitting, respectively. The results in this study show that the proposed method can be very usefully applied to the output-only system identification.

독립성분분석(ICA)법을 이용한 모드응답분리의 실험적 검증

황재승(Hwang Jae-Seung),박성철(Park Seong-Cheol) 대한건축학회 2012 大韓建築學會論文集 : 構造系 Vol.28 No.8

Independent component analysis is one of the linear transformation techniques to separate blind sources from the output signals of system. Recently, the method has been analytically applied for the responses of building structures to obtain the mode shapes and modal responses. The aim of this study is to experimentally verify the feasibility of the blind source separation by ICA method for three storey shear model structure and propose a method to effectively estimate the dynamic properties from the separated modal responses. From the results of experimental verification procedure, it is found that the mode shapes separated by ICA are similar to the mode shapes by the conventional method such as analytic eigen problem or power spectrum method, furthermore, ICA can efficiently and precisely estimate the mode shapes based on the mathematic robustness. In addition, by the proposed method to estimate the dynamic properties in this study, it is shown that the modal properties : natural frequencies and damping ratios of model structure are estimated effectively from the probability distribution function of instantaneous natural frequency determined by Hilbert transform and the differential equation of the output covariance, respectively. Finally, the results in this study also show that the proposed method can be very usefully applied to the output-only system identification.

자연진동 응답기록에 의한 초고층 건물의 성능치 추출

조순호(Cho Soon-Ho) 대한건축학회 2008 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.28 No.1(구조계)

Dynamic response measurements from natural excitation were carried out for 25- and 42-story buildings to evaluate their inherent properties, such as natural frequencies, mode shapes and damping ratios. Both are reinforced concrete buildings adopting a core wall, or with shear walls as the major lateral force resisting system, but frames are added in the plan or elevation. By using various state-of-the-art system identification methods, the modal parameters are extracted, and the results are then compared. Three frequency- and four time-domain based operational modal identification methods are considered. Overall, all natural frequencies and damping ratios estimated from the different identification methods showed a greater consistency for both buildings, while mode shapes exhibited some degree of discrepancy varying from method to method.