Stainless steel I-section beams subjected to combined torsion and bending: Experimental results

In this paper, the details of an experimental program, during which fabricated stainless steel I-section beams subjected to combined bending and torsion are tested, are presented. The test specimens consisted of 10 laser welded austenitic (EN 1.4307 and EN 1.4404) and traditionally welded duplex (EN 1.4162) beams of different cross-sectional dimensions and lengths. The experimental boundary conditions idealized a simply supported beam loaded at mid span with a transverse force applied away from the shear centre, leading to combined torsion and bending to model civil engineering applications. During the tests, the rotations were measured using inclinometers as well as Digital Image Correlation, while strains were measured using strain gauges. Mid span rotations of up to 35 degrees were reached leading to plasticity spreading across the cross-section. Firstly, the test results were compared against the elastic theory, including theoretical evaluations of the initial stiffness. Secondly, the ultimate capacities were compared to elastic and plastic verifications, showing the extent to which the current design rules are overconservative.