Graduate Diploma Thesis, July 2013
This work presents a nonlinear finite element simulation of the structural behaviour of ring-stiffened steel tubular members, which are used in offshore applications. In particular, the work focuses on the structural stability analysis (collapse) of those ring-stiffened steel tubes under external pressure. The tubes have a diameter-to-thickness ratio ranging between 30 and 100, and the ring stiffeners are spaced at a distance that vary between 0.5 and 5 tube diameters. Depending on the geometrical characteristics of the tubes and the stiffeners, the stiffened tubes may buckle either in the “local buckling” mode and “global buckling” mode, as shown in Figs. 1 and 2.
The numerical results are compared with available experimental data, conducted by CBI and SwRI research institutes and sponsored by the offshore oil & gas industry. The numerical and experimental results are also compared with analytical predictions from design provisions, regarding the significance of the various parameters which affect pressure capacity.