Research On The Fatigue Strength Assessment Of Bulk Carriers

Fatigue damage is one of the main forms of damage to the hull structure. Especially for large ships or very large ships widely use of high tension steel, so the ship structural fatigue problem has always been focused on during the plan approval of Hull structure. For this reason, after a long term research Lloyd's Register firstly published "Ship Right Fatigue Design Assessment"(Ship Right FDA for short) in 1994. Ship Right FDA is a variety of levels procedure, including three levels. It provide how to improve the fatigue strength from the structure detail design to define the dimensions of primary structure member. April 2006, IACS released the "Common Structural Rules for Bulk Carriers"(CSR-BC for short), and this is the first time in the history take fatigue strength assessment as the requirement of classification.Because Lloyd's Register Ship Right FDA and CSR-BC FDA use a different approach, there are some differences between the calculation results of them. And in this paper, we calculated fatigue strength of a 64 K Panamax bulk carrier, which is more common use in shipping market, using the two methods of Ship Right FDA and CSR-BC FDA, and compared and analyzed the difference of results.The several aspects investigated in this paper are as follows:(1) the research background and development of fatigue strength analysis. The principles of fatigue damage, the fatigue analysis methods and the history and current situation of fatigue strength assessment of home and abroad are introduced.(2) Briefly introduce fatigue assessment simplification algorithm combine with CSR-BC FDA. Introduce primary structural load selected in CSR-BC and the calculation flow path of CSR-BC FDA.(3) Briefly introduce fatigue assessment spectral direct calculation method combine with Ship Right FDA. introduce the basic principles and the calculation flow path of Ship Right FDA.(4) For the selected 64 K bulk carrier, use two methods separately to calculate the fatigue life of longitudinal stiffener end connection and hot spot in critical area, and compare and research the results.