Search

Offshore platforms are subjected to severe loads due to wave, current and wind. The floating structures are stationed in deep waters by using the mooring lines connecting them from the fairleads to ocean-bed. Considering the cost impact of mooring lines, it is essential to find the best possible mooring configuration for a given platform and met-ocean data, which reduces the responses of platform to an acceptable level. Hence, a study is conducted to find the effect of different mooring line pretensions on the dynamic responses of truss spar platform. The truss spar platform is modelled as a rigid body with three degrees-of-freedom i.e. surge, heave and pitch. The incident wave kinematics of water particles and wave forces on the structure are computed using the linear Airy wave theory and modified Morison equation respectively. The dynamic response analysis of spar platform is performed in the time-domain using the implicit Newmark Beta integration technique combined with the average acceleration method. The various mooring stiffness for different line pretensions are obtained by using quasi-static approach. Two numerical codes DATSpar and OSAML are developed in-house to conduct the dynamic analysis and quasi-static analysis respectively. It is observed that the dynamic responses of platform can be optimised by using mooring lines with relatively low pretensions. Although the platform dynamic motions are not significantly affected, its mean position varies for different mooring line pretensions. [ABSTRACT FROM AUTHOR]