Comparison of Methods for Seismic Response Analysis of an Offshore Jacket Platform Located in Bohai Bay, China

As designing offshore jacket platforms in seismically active regions, it is imperative to account for the seismic-induced loads on the structure. In this study, seismic structural analysis of an offshore jacket platform located in Bohai Bay, China is conducted using the response spectrum analysis (RSA) method and the time history analysis (THA) method. The structural dynamic responses are compared and the applicability of the two methods in the seismic design of jacket platform is assessed. Furthermore, a sensitivity study is conducted to investigate the effects of earthquake strengths, deck weights and pile diameters on the structural seismic responses using the two analysis methods. Typical results revealed that the RSA method is the preferred choice for seismic design when it comes to offshore jacket platforms situated in regions characterized by low seismic ground motions. Nonetheless, in regions with high seismic intensity levels, a more precise method should be contemplated. In such scenarios, the THA method is preferred, by conducting the nonlinear dynamic response analysis to account for the seismic-induced excitation loads. This approach has the potential to lead more efficient and cost-effective pile and platform designs.