Fatigue Strengthen Assessment Of Large PCTC

Fatigue and fracture have been an important issue for ship and offshore structures for a long time. Growing attention has been paid to it from researchers and institutes in this field. Great attention has been paid to how to reasonably assess the fatigue strength of ship. This paper expatiates on elements of fatigue assessment and general methods for fatigue strength analysis of ship structures. Special emphasis on the wave-induced loads is given to with different reasons. On the basis of these, the paper makes fatigue assessment with some hotspots in different structure positions. The paper also pays more attention to the usage factor and fatigue life due to different scatter diagrams, and analysis the Weibull shape B parameter difference with different scatter diagrams and structure types.The main aspects studied in this paper are as follows:1. Elements of fatigue analysis and general methods for fatigue strength analysis of ship structures are expatiated on, with emphasis on S-N approach.2. On the basis of the three-dimension potentials theory, the paper pays more attentions to the method for calculation wave-induced loads, the paper is to conduct the long term prediction of wave-induced loads for 5000 PCTC vessel, the different scatter diagrams, different wave incoming angles and different load conditions are considered for the long term prediction wave-induced loads and wave-induced movement.3.According to the thought of CSA-2 recommended by DNV, the long-term prediction of wave induced motion and loading are performed by the 3D radiation-diffraction hydrodynamic program, and based on which a group of design waves are defined. Then the stress in each design wave based on the FE model of entire ship hull is calculated. The detailed stress in the main structural members of ship hull are obtained4. Finally, the spectral fatigue analysis has been conducted under linear wave-induced loads and ship motion. In the analysis prod cure, the contribution of each sea state to the fatigue damage is dissertated. At the same time, the contribution of each sea state and the structure type and positions to the Weibull shape parameter is considered.