The emphasis of this work is on comparison of fatigue damage capacity at the bulkhead and web frame connections of side shell longitudinals under the effect of vertical and horizontal bending in combination. Fatigue analysis methods adopted such as component stochastic and full spectral consider an FPSO of 325 m length, selecting side shell longitudinal structural elements connected to the typical transverse bulkhead and web frame at mid ship area. The analyses are being performed in accordance with three loading conditions such as fully loaded, intermediate and ballast condition. This research uses spectral fatigue analysis to create a function of stress transfer that in turn helps generate the power spectral density function by the bending moment transfer function. The combination of spectral moments with the Palmgren-Miner law results in the FPSO's accumulated fatigue damage. The findings provide insight into the changes in fatigue damage of the structural component under the effect of vertical and horizontal bending moments. Not only acting global loads and local pressure are important on the side shell longitudinal elements, but also relative deflections of webs influence the stress response due to additional stiffener bending are required. Due to the large amount of intersection details of side shell longitudinals at transverse web frame and bulkhead and due to high repair costs in case of damage, a sound structural design is thus necessary. The findings and insights developed from the present work are discussed in detail.