Collapse analysis of ring-stiffened cylinders using ring elements

Asymptotic and fully nonlinear analyses are used to find the maximum load carrying capacity of ring-stiffened cylinders subjected to hydrostatic pressure. Both procedures use ring elements with harmonic description of displacements in the circumferential direction, and p-version shape functions in the other direction (longitudinal for shell and radial for stiffener). In the asymptotic procedure, the harmonics are uncoupled in the solution process, whereas they are coupled in the fully nonlinear analysis. In the latter analysis, a special iterative scheme that uncouples the harmonics in the solution of the iterative/incremental linear equations is employed. In general, the discrepancies between the two procedures increase with the level of imperfections and the thinness of the shell. The prebuckling nonlinearities that are not accounted for in the asymptotic procedure are identified as the major source of discrepancy. Sensitivity to imperfections in the shape of buckling modes given by the linear and nonlinear bifurcation analysis is also studied for comparison.