The Calculation Of The FRP Yacht Structural Reliability At Longitudinal Bending

The question must be considered by the designers, to assure the safety of the structure of yacht with certain probability, with the rise of yacht designing and manufacturing. A traditional method to check yacht hull strength is a deterministic method adopting safety allowance, but it cannot assure that every structure is safe with a certain probability. Therefore, a calculation method to ensure yacht hull strength with a reasonable distribution of structure failure probability, is needed in future. In 1960 s, the reliability theory combined probability and statistics theory with Structural mechanics theory gradually developed in shipping field, and which uses the reliability index and failure probability to stand for the structure safety, can solve the problem above. This theory is widely applied in steel shipping field, but there’s less research in the FRP yacht field.The paper introduces yacht structure reliability theory based on steel ship structure reliability theory. Furthermore, it calculates the yacht reliability index on basis of the combination of load distribution at longitudinal bending, theory of nonlinear finite element to calculate yacht structure ultimate strength and common methods to calculate structure reliability. The waves and load conditions of yacht are simulated through Maxsurf, and the distribution of gravity and buoyancy at different conditions of hull is shown. Then the paper builds the yacht model of simulated calculation combined with the advises of rules, and gets the yacht structure stress distribution; Finally, limit equation according to FRP failure criterion is built and the reliability index of hull structure junction in the dangerous section using the response surface method is calculated. The research adopts the quasi-static analysis method to simulate the process of yacht structure bending until damage at sagging and hogging condition, and then gets the ultimate bending moment of the middle subsection; when the limit equation based on yacht force equilibrium conditions at limiting states is built, to the reliability index is calculated with the JC method. At last, the paper analyzes the reliability results of the two methods.First, the paper gets the distribution of gravity and buoyancy at different states through Maxsurf, this method overcomes the problem that Abaqus cannot simulate wave loads flexibly. Second, it calculates the reliability of FRP yacht in force equilibrium conditions at limiting states and with FRP failure criterion, the latter method combines the results of stress distribution with method of composite laminate plate reliability index calculation, and provides a way to calculate reliability index of yacht different positions. The paper can provides some references for the application of reliability theory in the yacht structure checking safety.