Prediction of Local Seismic Damage in Jacket-type Offshore Platforms

Due to the severe environmental condition, steel jacket type offshore platforms are highly vulnerable to damage; so, ensuring its proper performance and detection of probable damage is very important and undeniable. The assessment of existing offshore platforms is relatively a new process and has not yet been standardized as the design has. To do so, seismic assessment of the existing 4-legged steel jacket type offshore platform placed in the Persian Gulf (SPD12) is presented in this paper. Based on an actual platform structure and its mechanical model, the parameters which may affect the rate of shock absorption are analyzed, such as the condition of the site where the platform is located. Assessment is done by finding the seismic damage spread in the structure. Therefore, by using some documents such as FEMA-356 and ATC-40 developed for seismic assessment of buildings, seismic damage of the jacket-type platform is predicted with pushover analysis, and damage spread in this structure is predicted. This method could be very simple and detect damage spread precisely. As a result, knowing the weaker points of the structure which will be the first and third levels of the platforms similar to SPD12 in structural system can help to detect the damaged places, and by improving the capacity of the structure locally, the structural damage spread will be delayed