Research On The Methods Of Direct Strength Analysis For The Ship Structures

There are two methods of the FEA of ship structure, the part-cabin FEA and the whole ship structure FEA.According to different issues, each of the two methods has its own advantages and disadvantages of evaluating the ship structure strength. The whole ship structure FEA method involves many factors and a large amount of work of making model, but the load cases, the wave loads and the boundary conditions are easy to simulate, and they are truer. So, the results of this method are more accurate. The part-cabin FEA method is easy to make model, but it's difficult to simulate the load cases, the wave loads and the boundary conditions, thus, the results of this method are imprecise. We can choose the method according to the actual situation, and achieve the safe, reliable and efficient purpose.This thesis takes a 98m (8000t) river-to-sea barge as an example to have a research on the similarities and differences of evaluating the ship structure local strength by the two methods, and find a part-cabin which can reasonable evaluate the ship structure local strength, then, make this method as a way to evaluate the ship structure local strength. The calculation software MSC.Patran&MSC.Nastran (the edition 2001 r3) are used for this thesis.There are two parts of this thesis. The first part use the whole ship structure FEA method to calculate the ship structure strength. This part involves whole ship structure model building, boundary conditions imposing, loads calculating, load cases choosing, and the results analyzing.The second part use four different part-cabin finite element models to calculate the stem strength of the ship. Then, compare the results of the whole ship structure finite element model with the results of the four different part-cabin finite element models, and finally find a part-cabin which can evaluate the ship structure local strength feasible and reliable.From this thesis, we can say that the part-cabin which involves the stern and 1/2 hold length aft tanks is feasible and reliable.