Deriving formulations for forecasting the ultimate strength of locally dented ring-stiffened cylinders under combined axial compression and radial pressure loads

Introduction: This paper focuses on the derived equations to evaluate the ultimate strength of ring-stiffened cylinders with local denting damage under combined loadings. The damage generation scenarios in this research are representing the collision accidents of offshore stiffened cylinders with supply ships. Methods: Numerical analysis of structures are performed using Abaqus software after validation against the experiments from the authors. The responses from seventeen cylinder specimens are analyzed to develop the numerical methods. Results: Good accuracy results were achieved when comparing the test results and the simulation results. Parametric studies are then performed on design examples of ring-stiffened cylinders when considering both intact and damaged conditions for assessing the reduction factor. Then, the novel simple design equations to assess the residual strength of ring-stiffened cylinders after ship collision are derived based on the regression analysis. These equations have good accuracy with mean value Xm (Uncertainty modeling factor) around 1.0 and together with COV (Coefficient of Variation) lower than 5.3%. Conclusion: The accuracy and reliability of the derived equations are validated by comparing it with the existing test data in open access. It is concluded that the proposed equations have high accuracy and reliability, and convenient application for the purpose of checking the residual strength of dented offshore cylinder under ship collisions.