Seismic performance evaluation for jacket platform based on capacity spectrum method

Key words:  capacity spectrum method  jacket platform  seismic evaluation  performance point  failure mode

Abstract:

As the current offshore platform seismic code cannot consider the inelastic seismic performance and the seismic failure mechanism, the seismic capacity evaluation method of offshore platform was proposed based on the capacity spectrum method. On this basis, the seismic performance and failure modes were obtained precisely, to solve the problem of evaluating the seismic behavior under strong earthquake. According to the design seismic spectrum, the inelastic reaction spectrum was established by reduction factor, and seismic evaluation of the jacket platform in Bohai sea of China was accomplished. The results show that the capacity spectrum method is suitable for offshore platform, because of easy calculation and creditable precision. The inverse triangle and high equivalence methods could be used to evaluate the earthquake force, so that the effects of altitude are considered. The pile foundation is one of the main causes leading to the platform to fail under seismic loads.When designing the seismic performance of a jacket platform, the strength and driving depth of the leg should be guaranteed, in order to avoid failure of pile foundation under strong earthquake which might lead to the platform to overturn.