Probability Analysis of Critical Load of Sphere-Cylinder Combined Shell Structures

The critical load of submersible structures is normally analyzed in deterministic method. However, some factors including structural sizes, material properties and the location of the components, etc., have random characteristics due to smelting and construction process. In other words, the critical load of submersible structures has uncertainty, so these parameters should be considered as random variables. In terms of sphere-cylinder combined shell structures, the critical loads on the cylindrical shell and spherical structures should be considered together to avoid the influence of boundary conditions on the analysis results. This paper focuses on the probability analysis of sphere-cylinder combined shell structures under critical load. According to the GJB calculation method of submarine design, the security calibration ranges of ring-stiffened cylindrical shell and spherical shell are determined, and seven kinds of failure modes of sphere-cylinder combined shell structure are supposed. The corresponding probability models of sphere-cylinder combined shell structure have been established, and the reliability calculations of each failure mode are conducted in FOSM method, JC method and Monte Carlo simulation method. Considering the correlation between different failure modes, reliability series model of sphere-cylinder combined shell structure is applied in the probability analysis. It is verified by comparison of ring-stiffened cylindrical shell and sphere-cylinder combined shell, with the increase of the structure components, the reliability of structure system shows a decline tendency.