Experimental investigation of the local-global interaction buckling of stainless steel i-section beams

This report describes an experimental program carried out at the University of Sydney to investigate the local and local-global interaction buckling of stainless steel beams. I-section specimens were used for this purpose, which were fabricated by connecting cold-formed channels in a back-to-back configuration. Three stainless steel alloys were included: austenitic S30401, ferritic S44330 and lean duplex S32101 as per the ASTM unified numbering system. Extensive material testing was carried out on the sheets employed in the experimental program, in order to determine tensile and compressive material properties, anisotropy parameters and enhanced corner properties. The I-section experiments encompassed six braced tests and 24 unbraced tests under four-point bending, with member spans ranging between 1.8m-4.0m. Section dimensions were designed such that relatively low local buckling stresses were attained, hence high levels of local and local-overall interaction buckling could be attained in the test specimens. The set-up for unbraced tests was specially designed to achieve clearly defined loading and support conditions. In view of the imperfection sensitive nature of the interaction buckling phenomena, geometric imperfections were measured prior to testing of each specimen. The load bearing capacity, global and sectional deformations were carefully recorded during each test. The experimental data will enable further theoretical research, specifically in calibrating detailed finite element models which are used to assess the current design guidelines for stainless steel structures.