Numerical evaluation of the mechanical behavior of an FPSO mooring system fairleads foundations due to maximum environmental loads

The present work aimed to study the mechanical behavior of the fairlead support brackets of a FPSO (Floating, Production, Storage and Offloading) mooring system located in the Campos Basin (22°58’14’’S, 42°01’36’’O to 20°19’08’’S, 40°20’16’’O) using numerical simulation. For an inextensible anchor line, the maximum stresses from the environmental loading of waves, winds and currents were determined. The stresses acting on the anchor line were applied to the centroid of the fairlead and the reactions to these, generated in the brackets, were applied in the internal region of the hole that receives the fairlead support axis. The brackets are fixed to the side of the hull by 3 vertical and 1 horizontal points. Their initial proposed geometry was based on models currently in operation on platforms P66 and P67 (Petrobras platforms capable of stocking 1.67 mi oil barrels each, with 288 m of length overall, they are designed to anchor at depth of 2200 m). The numerical simulation process was performed using the Mechanical APDL tool of ANSYS software with a computational model composed by three-dimensional (3D) finite elements. The results indicated that for the proposed geometry the mechanical integrity of the brackets is assured, considering that von Mises maximum stresses did not extrapolate the yielding stress limit of the steel.