Experimental Studies On The Optimum Configuration of Mooring Line for Truss Spar Platform

Cost optimization is can be consider as main aspect on the offshore structure project. It is crucial to find the best options of mooring configuration for a certain platform and metocean data. The main objective of this field of work is to reduce the dynamic response of the offshore structure as a whole. In this paper, optimum configuration study is based on two design parameters which are pretension load and azimuth angle. The motion response analysis of the platform is modelled on a truss spar, as a rigid body with six degree of freedom. Froude’s Law is used to convert the responses of the platform model into the actual scale (prototype scale). However, notice that Froude’s Law models do not scale all the parameters, it only applicable predominant factor in scaling system in wave mechanics, namely inertia.
This study presents the literature review and experimental methodology obtained from the physical model tests carried out with two different parameters of design variables. An experimental study by wave tank test has been performed in order to quantify the dynamic response of the truss spar platform subjected to regular and random waves. A model truss spar platform which is fabricated by steel plate with 1:100 ratio scales from the prototype is used in the study of optimum configuration for mooring lines. In wave tank, regular and random wave were generated by wave generator. Wave probe recorded the wave profile and the motion of the truss spar was captured by Qualisys Track Manager in six degree of freedom. There are three test were conducted which are static offset test, free decay test and sea keeping test. The results were presented in term of Response Amplitude Operator (RAO) in six degree of freedom. In summary, generally, the higher pretension has given lesser motion in term of RAO and the symmetric configuration for azimuth angle significantly can reduce the dynamic motion of truss spar platform as a whole.