Thin-walled beam-columns. II: Proportional loading 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. The tests involved pure compression, combined compression and bending, and pure bending. The test results are compared with the design strengths of the Australian Standard for Steel Structures AS4100, the AISC-LRFD Specification, and Eurocode 3, Part 1.1. It is shown that the experimental interaction curve is close to being linear in the intermediate and long slenderness ranges. The design interaction curves of AS4100, the AISC-LRFD Specification, and Eurocode 3 are shown to be conservative in all cases, particularly in the high moment regions. The conservatism is attributed to the definition of the design bending section capacity in the three specifications. Proposals that increase the bending section capacity are presented based on the behavior observed during the tests. The resulting moment-axial force interaction curves are conservative and in reasonable agreement with the tests.