A hybrid structural response cross-correlation functions based damage identification strategy for offshore platforms

Offshore platforms are critical to offshore oil and gas production, and reliable damage identification is essential for structural integrity assessment and long-term safe operation. However, random wave loads are difficult to measure directly in practice, which limits many existing methods. To address this issue, this study proposes a damage identification method based on hybrid cross-correlation functions (CCFs) of structural responses and further extends it to the simultaneous identification of structural damage and wave spectrum parameters. The wave load power spectral density is derived to construct hybrid CCFs integrating displacement, acceleration, and strain responses, with structural damage then identified by minimizing the discrepancy between the measured and estimated CCFs. Numerical studies on two offshore platform models and experiments on a small-scale jack-up platform demonstrate that the proposed method can effectively localize and quantify structural damage, with hybrid CCFs constructed from multiple response types providing higher identification accuracy than CCFs based on a single response type. The simultaneous identification method enables accurate identification of both structural damage index and wave spectrum parameters without requiring prior wave spectrum information, thereby extending the applicability of the proposed strategy to uncertain offshore environments.