Baseline-Free Decentralized Damage Detection of Beam-Type Structures Using Moving Impact Excitation and Two Movable Strain Sensors

Many existing damage detection methods based on structural vibration responses require responses from undamaged structures as the baseline for reference comparison, and the deployment of many measurement sensors on structures limits their practical application. In this paper, a moving hammer excitation and two movable strain sensors are employed in coordination. By extracting the wavelet packet energy (WPE) and relative entropy from adjacent strain responses, a baseline-free distributed damage detection index is established for beam-type structures. Specifically, the analyses of damage indexes for single damage, non-adjacent damage, and adjacent damage are presented, respectively. The performance of the proposed method is validated by numerical simulation cases of structural damage detection of a simply supported beam and the cable-stayed Haiwen bridge girder with various damage scenarios. Results indicate that the relative entropy index demonstrates high sensitivity to damage location and strong robustness to various environmental noises. Moreover, an experimental structural damage detection of an overhanging beam validates the performance of the proposed method. Therefore, an economical and effective decentralized damage detection method using two movable sensors and relative entropy is proposed for baseline-free beam-type structures.