The focus of this study is paid to general methodology and design of accident scenarios for floating production, storage and offloading systems (FPSOs) using more sophisticated tools such as the nonlinear FEM so that structural responses during and after a collision can be more precisely predicted. The extent of FPSO hull damage due to the different collision scenarios and impact energy levels are determined using the guidelines contained in the NORSOK Standard [2004a. Design of steel structure N-004, Rev. 2 October 2004; 2004b. Materials selections M-001, Rev. 4 August 2004]. The collision scenario is considered for accidental limit state with five-year onsite environment in this study. The various collision scenarios are defined such as supply vessel collision bow on, supply vessel collision side on, supply vessel collision stern on, and off take tanker collision bow on. Nonlinear finite element analysis, using large deformation FEM, is applied to analyse the damages to FPSO hull structures. Conservatively the impacting vessel is considered non-deformed during the collision (whole energy absorbed by the FPSO). Damage evaluation to hull parts of FPSO is checked, including flare and flares foundations, aft muster station, offloading reel and piping and green water protections above cargo deck. The results and insights derived from the present study are summarised.