Probabilistic Methods for Reliability Assessment of Floating Structures Based on Extreme Wave Simulation

With the increasing application of floating platforms in deep waters and harsh environments, a proper assessment of the reliability of floating structures is important to ensure that these structures can operate safely during their design lives. This study outlines a practical methodology for reliability analysis of a semi-submersible platform based estimating the probability distribution of the extreme response in rough sea conditions (survival conditions). The Constrained NewWave (CNW) theory combined with Monte Carlo simulations was first applied to simulate the random wave surface elevation process in the time domain. A Gumbel distribution was the best fitting to describe the dynamically sensitive extreme response statistics under extreme waves (drift and mooring tension). The derived probability distribution of the extreme response was subsequently used in estimation of the associated limit state func- tion, and a reliability analysis of the floating structure was conducted using the Monte Carlo method. A semi-submersible platform in a water depth of 1500 m subjected to extreme wave loads was used to demonstrate the efficiency of the proposed methodology. The probability of failure of the semi-submersible when considering mooring lines tension is greater than considering drift.