The Study On Mode Parameter Identification And Damage Detection For Offshore Platforms

A set of algorithm is developed for damage detection for offshore platforms in this paper. The development of structure health monitoring technique so far is summarized first then the methods of damage detection for offshore platforms are concluded. Some general characteristics of structure parameter identification and damage detection are discussed in case of SDOF. A sudden change in acceleration can be found as the index of damage time if the system has a non-zero displacement when damage happen while the amplitude corresponding with the frequency of excitation may change after damage happen. The short-time Fourier Transform, the Wavelet Analysis and the Empirical Mode Decomposition method are applied to decompose the acceleration signal for damage time identification successfully. Two algorithms (one cross-spectrum based in frequency domain and the other one is ITD method in time domain) for mode parameter identification are realized and adjacent result from experiment data of a scaled model obtained respectively. The mass elimination algorithm are developed for damage detection in vertical direction while the damage location with in horizontal plan can be find from some characteristics of mode shape changes.