Ultimate Strength Study Of High Speed Trimaran

High speed trimaran is kind of high-performance ship which have perfect transverse stability, sea keeping capacity and fast speed rapidity,it has a very wide prospects, such as research ships, maritime shipping, maritime transport, exploration and rescue boats, etc Therefore, the ultimate bearing capacity of its complex structure has been the concern of many researchers. There are some common methods used to study the hull ultimate strength, such as a direct calculation method, the idealized structural unit method (SUM), gradually collapse method, nonlinear finite element method and model test method. On the other hand, it is very difficult to completely predict the ultimate bearing capacity by numerical simulation because the ultimate strength problem involves geometric and material nonlinearities. High speed trimaran has side hulls and cross structures. Its motion and structural response of trimaran are more complex than monolithic ship and catamaran. According to sole rule for trimaran in the world (Rules For The Classification Of Trimaran 2006), All designing external loads include a overall longitudinal still water bending moment, wave bending moment, hogging splitting moment, sagging splitting moment, longitudinal torsional moment, transverse torsional moment and horizontal bending moment so on. Therefore, under these external loads, high speed trimaran may be damaged in each condition. It is very necessary that the overall ultimate strength of trimaran is researched.In this paper, model structural test and nonlinear finite element methods were applied to study ultimate strength for a high speed trimaran, the longitudinal ultimate strength was focused to be priority, and its overall ultimate strength were considered as well. Structural model test method was introduced to study the longitudinal ultimate strength, similarity theory and finite element method were applied to the structural model design. Three-point bending was applied on the model by hydraulic jacks in the ultimate strength test to simulate the peak wave bending moment of the high speed trimaran. The ultimate strength of the trimaran model was successfully determined from the model test. The load-stress and load-displacement curves of the model, and the trimaran failure mode were obtained. Nonlinear finite element method was an important tool in the study, the material nonlinearity, large strain and follower force are considered, the reasonable element type and size of mesh are used, the ultimate loads of model and full scale trimaran were calculated, compared and analyzed with model testing result, the relation between model and trimaran ultimate strength was studied, the final ultimate load of full scale trimaran was predicted. In addition, the ransverse bending, longitudinal torsional and transverse torsional ultimate strength of high speed trimaran were analyzed, some typical structural components were thickened locally, the influence of typical structural components on overall ultimate strength was analyzed, and facture mechanism and mode were evaluated.