Buckling of Unconfined and Confined Thin-Walled Steel Cylinders under External Pressure

Abstract

The present paper investigates the structural stability of thin-walled steel cylinders subjected to uniform external pressure. A brief discussion of unconfined steel cylinder buckling is presented first. Subsequently, motivated by the design of buried pipelines, buckling of confined steel cylinders, surrounded by an elastic medium, is examined. A two dimensional model is developed, assuming no variation of load and deformation along the cylinder axis. The cylinder and the surrounding medium are simulated with nonlinear finite elements that account for both geometric and material nonlinearities. The external pressure response of confined thin-walled steel cylinders is examined, in terms of initial the out-of-roundness of the cylinder, the initial gap between the cylinder and the medium, and the stiffness of the surrounding medium. Numerical results show a rapid drop of pressure after reaching the maximum pressure level. Finally, the numerical results show good comparison with a simplified closedform expression, proposed elsewhere, which could be used for buried pipeline design purposes.