Fully coupled mooring line and anchor catenary analysis

Abstract

Offshore floating systems integrate structural engineering, hydrodynamics, and geotechnical engineering. Today the state of arts in all the three aspects has reached rather high levels. Engineers are now able to use plenty of numerical tools and guidelines to achieve the design purpose. However, one of the biggest difficulties of floating system analysis is not in any of the three aspects, but in how to integrate all the structural and environmental factors in a whole system. In offshore floating systems, the mooring line and anchor system is a key component linking structures, fluid, and soil which interact between each other on the offshore floaters. The coupling of these factors has become a main challenge in mooring system analysis and probably the critical issue in the future offshore system design. This paper will present a new method of hydrostatic anchor catenary analysis coupled with anchor trajectory, mooring catenary, and rig offsets. This method integrates the tradition static catenary analysis and the geotechnical analysis on anchor performance. In this model, the mooring line starts from the rig fairlead, all the way to the anchor shackle in the soil with a catenary section above the mud-line and an inverse catenary section below the mud-line. Therefore, the water part and the soil part of the mooring system are fully coupled, as in the real world.