A modified random decrement technique for modal identification from nonstationary ambient response data only
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- 作者：Chang-Sheng Lin (1) lin.changsheng@nsrrc.org.tw
Dar-Yun Chiang (2) - 关键词：Modal ; parameter identification – ; Nonstationary ambient vibration – ; Random decrement technique
- 刊名：Journal of Mechanical Science and Technology
- 出版时间：June 2012
- 出版年：2012
- 期刊代码：108_1976-3824
- 类别：et
- 卷：26
- 期：6
- 页码：1687-1696
- 数据来源：sp
摘要
Modal identification is considered from response data of structural system under nonstationary ambient vibration. In a previous paper, we showed that by assuming the ambient excitation to be nonstationary white noise in the form of a product model, the nonstationary response signals can be converted into free-vibration data via the correlation technique. In the present paper, if the ambient excitation can be modeled as a nonstationary white noise in the form of a product model, then the nonstationary cross random decrement signatures of structural response evaluated at any fixed time instant are shown theoretically to be proportional to the nonstationary cross-correlation functions. The practical problem of insufficient data samples available for evaluating nonstationary random decrement signatures can be approximately resolved by first extracting the amplitude-modulating function from the response and then transforming the nonstationary responses into stationary ones. Modal-parameter identification can then be performed using the Ibrahim time-domain technique, which is effective at identifying closely spaced modes. The theory proposed can be further extended by using the filtering concept to cover the case of nonstationary color excitations. Numerical simulations confirm the validity of the proposed method for identification of modal parameters from nonstationary ambient response data.