Study Of Response And Dynamic Reliability Of Off Shore Jacket Platforms Subjected To Seismic Action

Offshore jacket platform is a usual type of platform in the oil exploiting industry, they are often suffered from many kinds of loads in their life, and the seismic action is one of the most important one, which is random and have a formidable destruction. So the analysis of the response to the platform is an essential procedure in its design period. In this paper, an offshore jacket platform is selected as an object of research , its finite model was built in the finite element software ANSYS and the response spectrum method was used as a solution to calculate the dynamic response of the platform, then the dynamic reliability was calculated based on the result of dynamic response. Those calculating methods and results are valuable to the practical project. This paper mainly contains following contents:Firstly, a Simulation Cabin's model was built in ANSYS. Secondly, the APDL program based on response spectrum method was wrote which is suitable to many kinds of structures and to different earthquakes. By using this program, the simulation cabin's maximum response in the Ms7 earthquake was calculated. Then extend the method to an offshore jacket platform and get its maximum response under Ms8 earthquake.Suppose earthquake is a stationary stochastic process, and take the probability of exceedance as Poisson distributing, use first excursion failure criterion to analyse the dynamic reliability of the platform. In the analysis procedures, the dynamic character of seismic action were take into account, and the loads except the seismic loads were simplified as static loads which estimated to be normal distribution, based on this suppose, the hybrid dynamic reliability of the platform was calculated, and the dynamic reliability under Ms8 as well as Ms9 earthquake were calculated too. In those calculating, considering the failure limit as a fixed value or a random variable are calculated separately, as well as the dynamic reliability whether or not consider the static load effect, at last the analyses and comparison were made among the result. In the comparison we found out that the static loads and its randomicity can't be ignore during the precision calculation.