Research on non-stationary characteristic test and decomposition for dynamic response of floating structures

Abstract

Considering the complex influences of harsh marine environments, auxiliary structures, and various operational processes, motion response of floating structures will inevitably exhibit non-stationary behaviors. Therefore, grasping the non-stationary characteristics of motion responses is imperative for a comprehensive understanding of the operational mechanisms. This paper presents a strategy for testing non-stationary characteristics and decomposing dynamic responses, with the objective of investigating the influence of non-stationary characteristics on motion responses of floating structures. The primary contributions of this study are: (1) Proposed a cointegration analysis method for characteristics testing applicable to floating structures to investigate potential non-stationary variations. It explains the statistics of non-stationary characteristics through dimensional analysis, establishing a connection between the test statistics and the engineering intuition of non-stationary motion response. (2) Proposed a non-stationary signal decomposition method based on adaptive segmentation and decomposition control techniques to overcome mode mixing issues in the decomposition of structural motion responses. The validity and applicability of the developed strategy for testing and decomposing non-stationary responses are verified through a synthesized signal and a numerical semi-submersible platform. Numerical results demonstrate that this strategy can effectively test the non-stationarity, and the accuracy of decomposition results is greater than 99%, and the maximum normalization error is less than 2%. Finally, physical experiments are conducted on a semi-submersible platform under regular and irregular waves action, respectively, to verify the feasibility of the developed strategy when applied to measured data. Experimental results indicate that this strategy can effectively detect the non-stationary characteristics of the measured response, and realize an accurate decomposition of structural motion responses. These results will provide valuable insights into understanding non-stationary characteristics relevant to various engineering applications.