A truss spar, named as Horn Mountain, was deployed in the Gulf of Mexico in 1,650 m of water, approximately 150 km southeast of New Orleans in 2002. Extensive field measurements were made using an integrated marine monitoring system attached to the truss spar. In this study, dynamic analysis of the truss spar interacting with its mooring and riser system was performed using a time-domain numerical code, known as ‘COUPLE’. The simulated results were then compared with the corresponding field measurements made during Hurricane Isidore. Satisfactory agreement between the simulation and corresponding measurements was in general reached, indicating that the numerical code can be used to conduct the time-domain analysis of a truss spar interacting with its mooing and riser system under severe storm impact.
Considering the truss spar, Horn Mountain, deployed in relatively deep water (1,650 m), coupled analysis should be made to account for the dynamic interaction between its hull and mooring and riser system. A numerical code, known as COUPLE, was used in this study. Initially, it was developed for computing the 3-DOF (Degree- Of-Freedom) motions of a spar positioned by taut mooring lines using a quasi-static (quasi coupled) analysis (Cao and Zhang 1997) and later extended to allow for dynamical interaction between a spar and its mooring system to quantify the damping effects of a mooring system on the slow-drift motion of a spar (Chen et. al. 2001). More recently, it was extended to allow for 6-DOF motions of a moored floater (Chen 2002, Ding et al 2003, Chen et al. 2006). It consists of two basic computational parts: one for computing the dynamics of a mooring/tendon/riser system and the other for the wave/current/wind loads on a moored floater (hull).
