Reliability Analysis of Fixed Platform due to Seabed Subsidence and Wave Load in Deck

The structural integrity of fixed platform may be affected from excessive load on the structure and insufficient strength of the structure. Another factor which affects the structural integrity is seabed subsidence. Seabed subsidence occurs due to vertical movement of soil layers and soil consolidation. The impact of seabed subsidence will lead to decreased of deck clearance or air gap and cause wave hits the deck. The aim of the study is to determine the effect of wave load in deck using pushover and reliability analysis. The wave height at collapse is calculated based on the reserve strength ratio generated from pushover analysis. The wave load in deck calculation is referred to American Petroleum Institute (API). The pushover with inclusion wave load in deck is necessary to be carried out to gain the updated reserve strength ratio. The reliability analysis is computed by involving base shear of fixed platform at collapse from pushover analysis with wave load in deck. Monte Carlo simulation technique method is adopted in the analysis which generating one million data of wave height and wave period as random variables. This study also performs the probability of failure and reliability index due to wave load in deck. As expected, the updated reserve strength ratio with wave load in deck is lower than the reserve strength ratio without wave load in deck. Then, the probability of failure increases with the increase of the depth of subsidence. Therefore, the reliability index decreases with the increase of the depth of subsidence.