Flexural Capacity of Pressurized Steel Pipe

This paper describes the experimental and theoretical behavior of two large-scale pressurized pipes tested with a sleeve fully welded to the midspan of each specimen. Each specimen was subjected to an internal pressure, a constant axial load and lateral deformation of a four-point bend test to simulate the flexural behavior of a buried pipeline. The only test parameter was the length of the sleeve needed for pipe repair; one specimen had a sleeve length equal to one pipe diameter, and the second specimen had a sleeve that was two pipe diameters in length. Flexural deformations were imposed on each test specimen until clear failure occurred. For both specimens, failure occurred by local wall buckling of the carrier pipe adjacent to the sleeve region. A simple theoretical model is discussed to predict the flexural capacity of pipes subjected to these load conditions. This analytical method was developed to enable a quick computation of the inelastic flexural strength of the pipe, and to enable a check of the output from a more sophisticated finite element analysis. Reasonably good agreement was found between the theoretical and the experimental flexural capacity of the pressurized pipe. Analytical results demonstrated that the Tresca yield criterion conservatively estimated the inelastic flexural strength of the pressurized pipe. It was also found that, when using the Tresca criterion to describe the inelastic behavior of the pipes tested in this research program, local inelastic wall buckling was initiated at a displacement ductility of about 3.