الفهرس 
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Abstract
Corrosion has a significant deteriorative effect on fatigue life of aged ship and offshore structures; hence reliable numerical fatigue life analysis of aged ship structures is crucial for safe operation. In this thesis, stress concentration over corroded plates was comprehensively studied. Based on the analysis, it was demonstrated that Stress Concentration Factor SCF significantly depends on the mean and minimum thickness of the corroded plate. Different approaches were adopted to estimate the fatigue life of real corroded specimens and compared with published experimental fatigue test results. The equivalent thickness of a typical plate which has the same fatigue strength of the corresponding corroded one under the same cyclic load was investigated. A time-dependent S-N curve of corroded structures considering the deterioration of material mechanical properties was proposed. The corroded surfaces were modeled using random spatial distributions and the effect of corrosion degradation on the material mechanical properties has been taken into account. The comparison showed good agreement between the experimental results and the adopted approaches for fatigue life assessment. Different fatigue analysis methods of marine structures were reviewed and the spectral fatigue analysis approach was employed to investigate the fatigue life of a typical connection between longitudinal and transverse element in a double side tanker considering corrosion deterioration effect. A MATLAB code was created for the application of this approach. A hydrodynamic diffraction analysis, in frequency domain, was carried out using ANSYS AQWA. The hydrodynamic loads were mapped on the global finite element model in ANSYS Mechanical. The loaded model was solved by the Mechanical APDL solver, taking into account the ship forward speed; two loading conditions, wave directions and frequencies and the reduction of the hull girder section modulus due to corrosion. The influence of different wave scatter diagrams, stress concentration factors, S-N curves accounting for corrosion, wave spectra and operational profiles on the accumulated fatigue damage was investigated.