Ductility of Concrete‐Filled Steel Box Columns under Cyclic Loading

Steel bridge piers under cyclic loading due to strong earthquake motion should be designed considering not only the strength but also the ductility capacity. Steel sections with concrete infill are being increasingly used as structural members, since filling the steel section with concrete results in an increase in both strength and ductility without increasing the section size. In this paper, the results of 11 cantilever thin‐walled steel box column specimens tested under constant compressive axial loads and cyclic lateral loads are presented. The test specimens were of unstiffened and stiffened box sections. To examine the possibility of increasing the column's ductility capacity, seven partially concrete‐filled column specimens were tested. The test results were evaluated using both energy‐absorption capacity and a newly defined ductility factor that takes into account the effect of plate local buckling. It has been shown that the concrete‐filled columns increase both ductility and energy‐absorption capacity significantly.