A comparative assessment of the impact of tilting on structural safety and behavior of fixed offshore platforms

Fixed steel platforms rest on the seabed, and uneven seabed settlement can lead to tilting them. Tilting changes the behavior of the platform, and evaluation of these changes is vital for estimating structural safety. This paper uses push-over analysis to investigate six four-leg platforms under different tilting scenarios. Besides modeling in intact condition, the platforms were modeled under four tilting orientations, three angles of tilting, and eight loads applying directions. Results show that tilting in each direction has different consequences, and the failure pattern of the platform plays a notable role in the post-tilting behavior of the platforms. In the most-critical case, 1, 2, and 5 ° tilting decreases the safety factor by 9, 18, and 32 percent, respectively. Also, in the platforms where the leg failure initiates the global failure, the tilting has the least effect on structural safety compared to those with toppling or large displacement failure patterns.