PSI - Issue 5

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Zuheir Barsoum et al. / Procedia Structural Integrity 5 (2017) 377–384 Fikri Bashar Yalchiner/ Structural Integrity Procedia 00 (2017) 000 – 000

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Fig. 3. Computer model (SACS) of 50 years old fixed offshore platform

5.2. Spectral Fatigue Analysis Method

The spectral fatigue analysis method is a statistical approach for the random nature of sea state using wave spectra and functions to develop the structural response over the wave frequency range. Therefore spectral fatigue analysis accounts for the actual distribution of energy over the entire frequency range which gives more realistic and reliable results than deterministic analysis. Pierson-Moskowitz has given the spectrum for a given H s and T z in the following equation: ( ) = 2 4 4 5 exp (− 1 ( ) −4 ) The data required for fatigue life estimation listed below: • Steel material mechanical properties for existing and new structures • Gravity loads • Environmental conditions (water depth, wave data, wave load parameters, marine growth) • Soil data • Corrosion allowance • Wave headings • Wave steepness • Damping • Stress Concentration Factors • S-N Curve