Analytical, experimental, and numerical analyses of the buckling of composite ring-stiffened steel cylinders

In the current research, the buckling loads and modes of composite ring-stiffened steel cylinders were studied when subjected to hydrostatic pressure. Analytical formulas for forecasting the linear buckling load of ringstiffened cylinders were derived and validated. Moreover, numerical and response surface analyses were conducted to determine the nonlinear knockdown factor (Knon). Pairs of nominally identical ring-stiffened and unreinforced steel cylinders were manufactured, measured, and tested, and corresponding numerical models were developed. The results from the analytical, experimental, and numerical studies were consistently in agreement. Reinforcement with composite ring stiffeners enhanced the experimental buckling loads by 258.8 % but increased weight by only approximately 17 %. Parametric analyses were also conducted to assess the impact of the composite ring's thickness and width on nonlinear buckling loads and postbuckling modes. Although the composite ring stiffeners enhanced the global structural stability and load capacity of plain cylinders, they also caused transitions in the postbuckling mode from global buckling to coupled, inter-ring, or mono-cell buckling.