Research On The Structural Strength Analysis Methods Of FRP Catamaran

Structural strength calculation is the critical process of yacht design. Currently, rulescalculation method is the based method of calculating the structural strength of FRP catamaran.Finite element method which has been widely used in the field of steel ships’ structural strengthcalculation is still not well developed in the field of yacht. In addition, there is no special rulesfor the FRP yacht finite element method direct calculation in CCS. Therefore, it is significant toresearch the structural strength analysis methods of FRP catamaran.This paper takes a FRP catamaran as the research object, and do research on its structuralstrength analysis methods. Rules method, finite element method and fluid-structure interactionmethod have been used in calculating the structural strength of a52ft FRP catamaranrespectively. Besides, three methods’ results are compared under the same condition.This thesis mainly studies are as follows:1）According to the CCS yacht construction rules, the design pressure and components sizeof some main structures are calculated, the results confirm that these main structures meetrequirements of rules.2）Calculating the yacht’s structural strength by finite element method. First, the detailedfinite element model of the FRP catamaran is created, and modeling the fiberglass sandwichstructures of the whole ship in ABAQUS. Based on the finite element method, directcomputation is performed on the whole model to obtain its strength under ten differentconditions which included transverse bending, longitudinal bending, torsion, cross structure’svertical shear and their coupling conditions. Then, it finds that the weak areas of the FRPcatamaran are mainly distributed in the cross structure, strong beam, semi-hull and their couplingareas. The maximum normal stress is35.26MPa, the minimum normal stress is-33.71MPa, themaximum deformation of the whole yacht reaches34.64mm.3）Calculating the yacht’s structural strength by fluid-structure interaction method. First, theflow field model is created. Then, the FRP catamaran finite element model and flow field modelare coupled by WORKBENCH. In order to achieve the coupling calculation of the two modelsunder the no wave state, longitudinal sea state and oblique sea state, inertia relief method and thenumerical wave generation technology are used.4）Comparative analyzing three methods. It takes the calculating sections of the rulescalculation method as the research object, compared results of the finite element method and fluid-structure interaction method, it is find that connecting bridge Aggregates and roof deck arenot dangerous. Based on the results of the finite element method and fluid-structure interactionmethod, their first10von-mises stress are compared. Then, by researching on the differences ofthe three methods’ dangerous points’ distribution, it is find that some dangerous points whichhave been ignored by the specification method. Secondly, the paper defines a new safety factor.The results of the main shell plates’ safety factors shows that, the plates’ results are too highexcept the connecting bridge plate and bulkhead plates by the rules calculation method the resultof the finite element method is somewhat too small under the conditions of the sagging. Theresults of fluid-structure interaction method can provide a reference for the correction about therules calculation method and the finite element method. Finally, the regulation of wave heightand speed varying with time is researched by fluid-structure interaction method.