Analysis of coupled body mooring and fender system

Abstract

The hydrodynamic excitation and response behavior of multi-body systems with varying degrees of coupling presents many challenges for designers of offshore structures. In this study, attention is focused upon the analysis and interpretation of experimental data obtained for an unmanned deepwater mini-Tension Leg Platform (mini-TLP) coupled to a tender barge. Each body has its own mooring system and the bodies are connected by two breast lines extending from central points on the mini-TLP to central points on the bow and stern of the tender barge. A fender system is located between the two platforms. Thus the two floating bodies are constrained to move together in surge and yaw while they are free to move independently in heave, roll and pitch with some limitations on sway. The data of the individual records are characterized using statistical moments, including skewness and kurtosis, to examine the degree of non-Gaussian behavior. Correlation analysis and cross spectral analysis are used to investigate the relationships between selected measurements such as the motion of each vessel, tensions in the mooring lines and tendons and the forces on the fenders. The analysis shows that the coupling effects reduce the mooring line and tendon tensions significantly and that the motions of the two vessels influence the line tensions and fender forces. The data distribution patterns followed by the parameters and the corresponding extreme values are also investigated.