Purpose <p>Structural health monitoring (SHM) is essential for ensuring the safety and reliability of bridge structures. This study focuses on the application of Wavelet Packet Permutation Entropy (WPPE) for identifying and localizing multiple damage scenarios in steel box girder bridges under harmonic excitation.</p> Methods <p>A finite element model of a steel box girder bridge was developed, and multiple damage cases with varying locations and orientations were simulated. WPPE was applied to extract damage-sensitive features from vibration responses, and its effectiveness in multi-damage identification was evaluated.</p> Results <p>The results demonstrate that WPPE can accurately detect and distinguish multiple damaged regions, even under complex conditions. The Permutation Entropy Difference (PED) values exhibit distinct peaks at multiple damage locations, enabling precise identification. While mutual interference between damage regions slightly affects detection accuracy, WPPE remains robust under 10 dB ambient noise, confirming its resistance to environmental interference.</p> Conclusion <p>WPPE provides a sensitive and reliable approach for multi-damage identification, outperforming conventional frequency-domain methods in capturing nonlinear damage features. Future work will focus on experimental validation, application to large-scale bridge structures, and integration with deep learning models for enhanced automation and accuracy.</p>