A new damage indicator denoted by the distance between ARMA models is proposed in this paper to identify structural damage including its location and severity. Two definitions are introduced as the distance, either the cepstral metric or subspace angles of ARMA models. However, the accuracy is deteriorated when the multiple inputs have strong correlations. To overcome this difficulty, a pre-whitening filter is applied. Thus, the proposed damage indicator is applicable for varieties of excitation types in civil engineering, such as wind, traffic loading and earthquake excitations. A five-storey building model is used for performance verification when subjected to different excitations. Ambient force and earthquake input have been used as excitations acting on the structure. Two calculating methods of the proposed damage indicators are both evaluated. When the excitations are mutually correlated, by using the pre-whitening filter, the damage identification ability of the proposed damage indicator improves significantly, especially for damage localization. The damage indicator increases monotonically with damage severity, which provides the potential for damage quantification.
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