Seismic response effects on large offshore platform

One of the major concerns regarding large offshore structures is the heavy deck loads resulting in large reaction forces on the foundations. If these reaction forces can be reduced by some methods such as using buoyancy-type large members as structural components, then large-scale offshore platforms may be successfully employed for the development of ocean spaces. When a large offshore platform has to be constructed in the area of seismic activity, it is important to evaluate the effects of the seismic loads in addition to those of wave loads. The seismic responses are determined with typical power spectra of seismic motions. The reliable evaluation of the dynamic response can be carried out using the random vibration method and the second moment approach. It is suggested that the reliability index, which is computed by the second moment approach, provides a good evaluation to these environmental loads with different characteristics.