FLEXURAL TESTS OF LONGITUDINALLY STIFFENED FABRICATED STEEL CYLINDERS

Fabricated steel cylinders with large R/t ratios are often used in conveyor galleries, offshore platforms, storage tanks, towers, vessels, and the like. The use of longitudinal stiffeners in these large cylinders has proven to be an efficient way to promote structural stability. The increase of load capacity is significant. However, the attachment of the stiffeners complicates the problem by introducing additional buckling modes and new design parameters. Four large-scale specimens were tested. The collected data included the load versus deformation behavior, as well as the geometric imperfections and welding residual stresses of the specimens. The objective of the research program was to investigate the local buckling behavior and ultimate load capacity of longitudinally stiffened steel cylinders subjected to bending. The results showed two failure modes, a shell buckling mode and a general buckling mode. The occurrence of both modes and the corresponding capacity depend on the shell properties, as well as on the spacing and angle of are covered by the stiffeners. The general buckling mode has strength and ductility much higher than those predicted by existing design guidelines.