Fatigue Damage Calculation of ULCS Due to Quasi-Static Wave Response and Springing Response

摘要

Ship transport is growing up rapidly, leading to ship's size increase, and particularly for container ship, the last generation is now called Ultra Large Container Ship (ULCS). Due to their increasing sizes, they are more flexible and their structural natural frequencies may fall into the range of the encounter frequencies of the waves. Therefore, waves may induce springing vibration of the whole hull girder, which will increase the fatigue damage. This phenomenon is disregarded in the present classification fatigue rules for ship design and construction. On offshore structures, several methods of combination of low and high frequencies loads are proposed for the determination of fatigue damage in the ISO/FDIS 19901 standard. But none of them are relevant for ULCS fatigue evaluation. The purpose of the present paper is to propose a practical method for fatigue damage calculation applicable for classification of ULCS. This methodology is called the "Total stress RAO".