Study On Mechanics Characteristics Of High-speed Trimaran

The design of ship structure usually depends on two methods: criterion design and direct calculation. For the increase of ship size and the development of new ship type, every classification society in the world is searching for reasonable and reliable new design method. Then ship structure direct calculation method is used more widely than before. With the great development in modern mechanics, computational mathematics and computer technology in hardware and software, finite element analysis has made rapid progress in both theory and computational technology. Because of the complexity of ship structure and its exterior loads, accurate forecast of structural strength is a very difficult mission. Finite element method has been an effective method for analyzing the full-ship strength, which changes the traditional calculation concept of separating the general strength and local strength.Trimaran is a new type of high-speed ship which draws more and more attention inside and outside in recent years. Compared to the monohull and catamaran, trimaran has such excellence: favorable transverse stability, sea-keeping, wave-making resistance, broad deck, preferably viability and so on, and it becomes the research hotspot of new type ships. Because of the complexity of ship structure and its exterior loads, the analysis of its structure is very difficult, so the research of design is still limited, and there are no corresponding rules for trimaran in the world.Beginning with the actual state of trimaran research, its structure character and performance has been introduced. Then a primary discussion and analysis of the loads of trimaran has been carried on in this paper. According to some rules and literatures, a primary structural design has been done for a TRISWACH with the length of 54 m, and its distribution of stress under each loads condition has been qualitatively analyzed with ANSYS. The whole stress distributing rules are given, and the stress distribution of the cross structure has been analyzed in detail. The calculation and adjustment of the draft and float condition is firstly needed to guarantee the buoyancy approximately balance to the weight when we analyze the strength of the ship structure with FEM. Doing this can make the stress results nearby the constraint point not distort seriously. In this thesis, based on the idea of optimal design, a method of loads balance adjustment in full-ship finite element analysis is presented. Based on the approximate balance adjustment of the loads, the technique of inertia relief has been used for dealling with the boundary condition.The elastic-plastic transient dynamic response of the wetdeck of cross-structure under slamming loads has been analyzed in this thesis. The dynamic responses of three different constructions have been compared with the equal mass, which are transverse framing system, longitudinal framing system and densely reinforced structure. The results show that the ability withstanding the slamming loads of the densely reinforced structure exceeds the two others.