Direct Time Domain Life Cycle Loading Analysis on a Floating Platform

Abstract

Time domain numerical simulations with TechnipFMC’s in-house program were performed to estimate life cycle loading on a floating platform using High Performance Computing (HPC). Direct Simulation Analysis (DSA) were conducted to estimate fatigue life of mooring lines of two Spar platforms and the results were compared with fatigue life estimated from the condensed bin approach. In the Direct Simulation Analysis, 35-year hindcast wave and wind data with 3-hour interval for Gulf of Mexico was used. The wind and wave data covers from January 1979 to December 2013 for every 3-hours. The current data was not available so associated current information was approximately estimated. The time domain direct simulation results include nonlinear loads, nonlinear responses and seasonal effects such as hurricane events. The life cycle loading analysis tool developed will reduce uncertainties and increase the accuracy and reliability of the estimation of the mooring fatigue life during the service life of platform. Fatigue life of a mooring line from condensed bin analysis is highly variable with more than 20% depending on the selected wave seed number. In addition, the fatigue life from condensed bin analysis is about 20% less than the fatigue life from the Direct Simulation Analysis. This paper presents the systematic comparisons between the conventional approach and the direct time domain simulation results and also provides some major findings. In addition to the mooring line fatigue analysis, the structural fatigue analysis is also being performed and the results will be presented in the near future.