Design of Ocean Systems

Part III Design: Mooring System Design

Objective

To develop a preliminary mooring system design (for the FPSO you designed) based on the consideration of steady wind/current/wave loads/motions, wave-frequency loads/motions, and slowly-varying loads/motions of the FPSO. Full loaded ship condition (100% loading) in 100-year survival sea environment is considered in the design and analysis.

1. Under the head sea condition,
   1. determine steady wind, current, and wave drift loads on the FPSO;
   2. determine slowly-varying wave load on the FPSO; and
   3. determine wave-frequency motions of the FPSO
2. Develop a preliminary design of the mooring system
3. Compute load-excursion relations
4. Compute:
   1. steady tension in the cable and steady horizontal displacement of the FPSO;
   2. wave-frequency tension in the cable;
   3. estimate (surge) natural frequency of the FPSO; and
   4. slowly-varying tension in the cable and slowly-varying displacement of the FPSO
5. Determine:
   1. maximum tension in the cable and safety factor, and
   2. maximum displacement of the FPSO
6. Assuming one cable is broken, repeat (c), (d), and (e)
7. Discuss the performance of the designed mooring system and possible improvements for the design

Software

RISER-SIM (developed by MIT Professor Michael Triantafyllou)