PERKIRAAN UMUR KELELAHAN KONSTRUKSI LAMBUNG FSO DENGAN METODE SPECTRAL-BASED FATIGUE ANALYSIS

Abstract

This paper addresses the prediction of fatigue life for hull construction of Arco Ardjuna FSO operated in the West Java Sea. The method is based on the full spectral analysis and hot-spot stress approach. In the early stage, the study is conducted to analyze the wave loads using a hydrodynamic model to derive the global structural responses (vertical shear forces and vertical bending moments). These global responses are then set as the main input for the global structure analysis using a finite element model to obtain stress RAO for each critical location. Spectral Analysis is then performed to generate stochastic parameters that are used to identify the stress occurrence in the real ocean waves, which are random in nature. The short-term analysis (Rayleigh distribution) and long-term analysis (Weibull distribution) are further performed to obtain the stress distribution as well as the extreme stress range. Palmgren-Miner cumulative theory is next applied to calculate the fatigue damage directly correlated to the fatigue life. Closed-form fatigue equation, with the shape parameter of Weibull distribution, is then implemented to calculate the fatigue lifes at other critical locations in the FSO Structure.