응답 파워스펙트럼밀도 적분함수를 이용한 구조물의 감쇠비 추정
Estimation Technique of Damping ratio Using the Integral of Response Power Spectral Density Function
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초록
바람에 의한 구조물의 진동은 관심대상이 되는 지배모드의 감쇠비에 매우 민감하다 . 감쇠비의 발현 메커니즘의 불확실성 등 에 의해 감쇠비의 추정은 여전히 도전과제이며 보다 정확한 감쇠비 추정을 위한 연구가 지속되고 있다 . 본 연구에서는 스펙트럼 밀도 적분함수라는 새로운 개념을 이용하여 구조물의 감쇠비를 추정하는 기법을 다룬다 . 모드 응답스펙트럼에 포함된 외부하중 스펙트럼을 적분에 의한 평균화효과에 의해 평탄화 한 후 이론적 적분함수와 비교하여 감쇠비를 구하는 원리이다 . 감쇠비 추출 가능성 탐색을 위 해 이론적 스펙트럼 밀도 적분함수의 특성을 분석하였으며 , 비고전감쇠 시스템이 가지는 혼성 모드응답에 적용할 수 있는 감쇠비 추 정법로 확장하였다 . 본 연구에서 제안된 감쇠비 추정법을 검증하기 위한 수치해석과 계측응답에 대한 적용이 이루어졌으며 , 검증결과 제안된 감쇠비 추정법이 안정적이며 , 신뢰도가 높은 감쇠비 추정이 가능함을 알 수 있었다 .
Abstract
The wind-induced vibration of structure is very sensitive to the damping ratio of governing modes of interests. Research to identify the damping ratio from the structural response have been developed for several decades, however is still challenging. A novel estimation technique of damping ratio of a structure is proposed in this research, which is based on the integration of power spectral density (PSD) function. The damping ratio estimation concept is devised on the principle that the integration of PSD have a flattening effect of the external load spectral density so that the integral of spectral density function of decomposed mode can be very closed to the corresponding theoretical integral function. The damping ratio can be identified by comparing the two integral functions. In order to extract the damping ratio, the properties of the integral of theoretical spectral density function is examined, and it is also shown that the estimation technique is applicable to the modal response separated from a non-classically damped system. For the validation of the developed technique in this study, numerical analysis for the mathematical model and application for the site-situ measurement were carried out. From the verification process, it was shown that the technique to estimate the damping ratio is robust and reliable with high stability.
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