COUPLED ANALYSIS OF FLOATER MOTION AND MOORING DYNAMICS FOR A TURRET-MOORED SHIP

Traditional global response analyses of moored floating structures are calculated in two separated steps: calculations of floater motions; a nd dynamic response analysis of moorings and risers using the top end motions estimated in the first step. Typical shortcomings in the tradi tional separated approach are neglection or simplification of current forces and low frequency damping contribution from moorings and risers . In a coupled analysis procedure where floater motions and mooring an d riser dynamics are calculated simultaneously, these drawbacks are av oided. Motions and mooring line tensions from model tests and simulati ons using coupled and separated analysis procedures are compared. Illu strations are given by extensive case studies of a turret-moored ship operating in 150 m, 330 m and 2000 m water depth. The main conclusions are that the traditional separated approach may be severely inaccurat e, especially for floating structures operating in deep waters. Couple d analysis should be applied for deep water concepts, at least as a ch eck of important design cases. The agreement between model test result s and results from coupled analysis is very good. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.