Reliability Analysis of Damaged Steel Jacket Platform under Ship Impact

Marine vessels may cause accidental damage to the offshore platforms during uploading oil and gas production in the storm conditions or incorrect navigation by ship’s captain. This impact of sea-going vessels is source of local or global deformations in the offshore structures. In this research the reliability indexes of damaged members under vessels impact are estimated for a platform in the phase 19 of the South Pars using the first-order reliability method (FORM).Only deformation of structural members are considered as damage impact and energy dissipation during collision is not addressed in this research. The time consuming Monte Carlo simulation Method (MCS) and Important Sampling (I.S.) are used to verify the first-order reliability method because the limit state function in FORM is linear-zed by the Taylor series. At first, the wave force is applied into the safe structure, and reliability indexes are estimated for structural members. Then, in addition to the wave loads, the deformations caused by the assumed collision are also taken into account and structural reliability is estimated in the damaged state and corresponding results are compared with each other. Finally, combinations of wave and current, wave directions, and damages scenarios in chord, vertical and horizontal bracing are considered and results are compared.