Collision Analysis For FPSO In Tandem Offloading Operation And The Design Of Hull Crashworthiness

As a comprehensive large marine oil production base,FPSO has been applied in all kinds of deep sea and marginal oil fields.At present,FPSO has become the main production mode of marine oil and gas resources development.The oil and gas of FPSO are transported by shuttle tankers in the form of tandem offloading operation and side-by-side offloading operation.FPSO is generally used in the form of tandem offloading operation because it is able to adapt to operation conditions in more complex sea conditions and has higher safety.In tandem offloading operation,FPSO stern impacted by shuttle tanker is a possible but critical accident called stern collision.Stern collision accidents often cause damage to FPSO's stern structure and a large number of oil spills,resulting in marine environmental pollution,personnel casualties,loss of property,and other serious consequences.Therefore,this paper focuses on the collision accident during tandem offloading operation.In order to improve the crashworthiness of the FPSO's stern structure and ensure its safety during tandem offloading operation,it is of great significance to analyze and evaluate the stern collision performance at the design stage and carry out further optimization design for the stern structure of the FPSO.In this paper,the collision scenario is selected according to the FPSO tandem offloading operation mode.The numerical simulation and analysis are carried out by the nonlinear finite element analysis software ABAQUS.This paper focuses on simulating the collision accident due to excessive surging and fishtailing between 150000 t FPSO and tandem offloading shuttle tanker.The computational time and structural responses of the two methods,simplified analysis and synchronized damage analysis,are compared and analyzed.The crashworthiness of FPSO's stern structure is checked and evaluated by analyzing the damage deformation,stress-strain relationship,collision force,and energy absorption.In addition,the effects of different impact velocities and impact angles on collision performance are studied.An optimized design of FPSO stern structural crashworthiness based on orthogonal experimental design,BP neural network and genetic algorithm is developed.The thicknesses of components in FPSO stern with strong energy absorption capacity are chosen as the optimal design variable.An index of crashworthiness as the objective function is set up with the specific energy-absorption and unit mass deformation.The constraint conditions are determined by the manufacturing process.At the end,the optimization design mathematical model of FPSO's stern structure is established.By comparing the crashworthiness index values using different optimization methods,the optimal design of structural crashworthiness is obtained.The results may have some reference significance to the structural crashworthy design for FPSO's stern structure.