Thin-walled beam-columns. I: Sequential loading and moment gradient tests

This paper presents tests on thin-walled I-sections in combined compression and minor-axis bending. The tests were conducted in a rig consisting of two interlinked actuators applying axial force and end moment. Tests were performed using sequential application of axial force and moment, as well as proportional loading with a moment gradient. The results are compared with the results of proportionally loaded members described in a companion paper. It is shown that sequential loading produces beam-column strengths that are greater than or equal to those obtained using proportional loading. It is also shown that the beam-column strength of members loaded with a moment gradient exceeds that of beam-columns in uniform bending. The latter result is attributed to the effect of greater amplitude modulation of the local buckling deformations in beam-columns with moment gradient.