ABSTRACT
The offshore jacket platform, which is in long-term operation in harsh conditions at the ocean, will be confronted with damages such as fractures. As an extremely external strong load, marine earthquake often causes great harm to offshore structures. Therefore, it is of great significance to study the dynamic response and seismic fragility of the damaged offshore platform under seismic loading and to clarify the corresponding seismic limit criteria. In this study, the offshore jacket platform with fracture damage is taken as the research object, and the method is based on nonlinear dynamic analysis results of the platform subjected to possible ground motions. By using the finite element (FE) software ANSYS, the FE model of the damaged offshore jacket platform is established. Based on the incremental dynamic analysis (IDA) method, the amplitude modulation of seismic waves was carried out, and the elastoplastic dynamic time history analysis of the offshore jacket platform under seismic loadings of different intensities is carried out. According to the results of IDA analysis, quantile curves were drawn to study the damage degree of the platform under different seismic intensities; besides, the seismic vulnerability curve of the platform was drawn by using linear regression fitting methods, and the failure probability under different states is calculated to reveal its limit capacity to withstand seismic hazard. The study provides theoretical support for ensuring the safe operation of offshore jacket platform structures under seismic loading.
