Development of design tool for statically equivalent deepwater mooring systems

摘要

Verifying the design of floating structures adequately requires both numericalsimulations and model testing, a combination of which is referred to as thehybrid method of design verification. The challenge in direct scaling of mooringsfor model tests is the depth and spatial limitations in wave basins. It is thereforeimportant to design and build equivalent mooring systems to ensure that thestatic properties (global restoring forces and global stiffness) of the prototypefloater are matched by those of the model in the wave basin prior to testing.A fit-for-purpose numerical tool called STAMOORSYS is developed in thisresearch for the design of statically equivalent deepwater mooring systems. Theelastic catenary equations are derived and applied with efficient algorithm toobtain local and global static equilibrium solutions. A unique design page inSTAMOORSYS is used to manually optimize the system properties in search ofa match in global restoring forces and global stiffness. Up to eight mooring linescan be used in analyses and all lines have the same properties. STAMOORSYSis validated for single-line mooring analysis using LINANL and Orcaflex, and forglobal mooring analysis using MOORANL and Orcaflex. A statically equivalentdeepwater mooring system for a representative structure that could be tested inthe Offshore Technology Research Center at Texas A&M University is thendesigned using STAMOORSYS and the results are discussed.