FEMA approaches in seismic assessment of jacket platforms (case study: Ressalat jacket of Persian gulf)

The assessment of existing platforms under past environmental (wave, wind, current and etc.) loads and probable future loads (earthquake) is a relatively new process and has not yet been standardized as the design has. This lack of standardization creates some difficulty in establishing performance requirements which must be developed depending upon the risks (i.e., hazards, exposures and consequences) associated with the future operation of the platform. The present criteria of the offshore structure standards for seismic assessment can be improved using Building prestandards. Recently some documents such as FEMA-356 and ATC-40 are developed for seismic assessment of buildings. However there is advice in API documents (API RP 2A) in order for seismic assessment of jacket platforms, but because of brief existing comments in this field, it is necessary to use more appropriate (pre)standards for seismic assessment of these structures. In this paper rough and global comments of API are compared with a detailed method of FEMA. As an example seismic assessment of the existing 4 legged Service platform placed in the Ressalat Oil Field (Persian gulf) is presented. It is very useful and efficient to use of FEMA for seismic assessment of jacket platforms.