Estimation of current loads on side-by-side moored two vessels

Environmental loads acting on offshore structures, particularly side-by-side moored vessels such as LNGC (Shuttle)-FPSO, are important for analyzing the behavior of the vessels in order to examine the possibility of a safe LNG transfer between two vessels. Among various environmental loads, current loads are normally estimated by using empirical load coefficients. However, standardized load coefficients for offshore vessels are available to a limited extend and it is not easy to apply for vessels with arbitrary shape. Particularly it is the case for multiple vessels. In order to estimate current loads on offshore structures accurately, towing and wind tunnel tests are carried out. In this study, current loads on side-by-side moored two vessels are estimated by towing tests. First, we considered two shuttles of the same kind set in parallel with varying the separation distances. A moored FPSO-Shuttle system is also considered with different ballast conditions. Experimental results clearly show the interaction between two floaters in terms of the magnitude and direction of the load. It implies that the current loads must be correctly treated in the motion analysis of multiple offshore floaters.