Mooring Cost Sensitivity Study Based on Cost-Optimum Mooring Design

The paper describes results of a sensitivity study on an optimum mooring cost as a function of safety factor and allowable maximum offset of tire offshore floating structure by finding the anchor leg component size and the declination angle. A harmony search (HS) based mooring optimization program was developed to conduct the study. This mooring optimization model was intergated with a frequency-damain global motion analysis program to assess both rost and design constraints of the mooring system. To find a trend of anchor leg system cost for tire proposed sensitivity study, optimum costs after a certain number of improvisation were found and and compared. For a case study a turret-moored FPSO with 3x3 anchor leg system was considered. To better guide search for the optimum cost, three different penalty functions were applied. The results show that the presented HS-based cost-optimum offshore mooring design tool can be used to find optimum mooring design values such as declination angle and horizontal end point separation as well as a cost-optimum mooring system in case either the allowable maximum offset or factor of safety varies.