Substructural identification of jack-up platform in time and frequency domains

•The novel use of substructural identification and genetic algorithms is explored to address challenges involved in system identification of offshore structures.•The identification strategies are proposed in time domain as well as frequency domain involving multiple novel ideas.•The proposed identification strategies are validated by both numerical simulation study and experimental study.•The proposed identification strategies are therefore useful non-destructive methods for monitoring of jack-up platform and similar offshore structures.

Response monitoring can contribute to the safe operation and reliable assessment of offshore structures in harsh environments. By means of system identification, measured dynamic signals can be used not only for validation of modeling and analysis, but also for providing timely information of structural performance and early warning of structural changes which could indicate possible damages. Nevertheless, identification of offshore structures presents more challenges than land-based structures, such as unknown wave loading, unknown initial conditions and unknown foundation conditions. In this paper, the novel use of substructural identification and genetic algorithms is explored to address these challenges with focus on offshore jack-up platforms. Time domain identification and frequency domain identification are both studied for better solutions. The proposed identification strategies are validated by numerical simulation study as well as experimental study of a laboratory model.