Reliability Evaluation of Jacket-type Offshore Platforms Subjected to Wind, Wave, and Current Loads

The aim of this study is to evaluate the reliability and sensitivity of jacket-type offshore platforms under wind, wave, and current loads. The reliability of the platforms are comprehensively determined based on the deformation and energy of the jacket platform. The Young's Modulus; the yield strength; the strain hardening rate; the diameter and thickness of members; the water depth; the wave height and period; the wave velocities on the surface, middle, and base of the platform; the drag coefficient; the inertial coefficient; and the horizontal concentrated scaled loads are defined in the study as random variables. The sensitivity of the performance functions to the above-mentioned variables is determined, and the variables that most influence the performance of the platform are identified. Main conclusions are drawn as follows: the increasing mean and decreasing standard deviation of wall thickness in Type-1, Type-4, and Type-2 jacket members can effectively reduce the deformation and total strain energy of platform structures. For jacket structures in the plastic state, increasing the mean and decreasing the standard deviation of yield strength is a reasonable method for reducing deformation. Maximum deformation and strain energy are highly correlated whether the load level is high or low, and the correlation of these indicators with the variables considered gradually increases with the load level.