Data-Driven Identification of Structural Damage Using Wavelet-Based Transmissibility Functions of Structural Strain Responses

In this paper, a damage identification method is proposed for bridge structures under unknown seismic excitation using wavelet-based transmissibility functions (TFs) of structural strain responses. Structural strain responses of intact structures under unknown ambient excitation are used as baselines. The wavelet-based TF of structural strain responses of damaged structures under unknown seismic excitation is compared with that of intact structures under ambient excitation to construct a damage index. This damage index effectively eliminates the influence of different excitation, i.e. ambient excitation to intact structures and seismic excitation to damaged structures. Compared with the current TF-based method of structural acceleration or displacement responses, the proposed method avoids the frequency band selection in the frequency domain TF and utilizes the high sensitivity of structural strain responses to local damage. Additionally, it enhances local feature extraction ability by the wavelet transform. The proposed method is first illustrated through numerical damage identification of a simply supported overhanging beam and the main girder and tower of the Haiwen bridge. Then, it is validated by the damage identification of a cable-stayed bridge tower model under laboratory shake table tests. The damage identification results demonstrate that structural damage can be accurately located and damage degrees can be reflected by the damage index constructed from the wavelet-based TF of structural strain responses with the influence of noise, which is beneficial for structural health monitoring of actual bridges.