Performance of minor axis rectangular hollow section column to I section beam connections under cyclic load and fire exposure

Abstract

Steel beam-to-column connections are critical structural regions under cyclic loading and may also suffer significant residual degradation after fire exposure. This study investigates the minor-axis behavior of rectangular hollow section column-to-I-section beam connections by testing seven connection configurations in two conditions, namely unheated and post-fire residual, resulting in a total of 14 cyclic tests. The fire-exposed specimens were first subjected to furnace heating following the ISO-834 fire curve and then cyclically tested after cooling to room temperature; therefore, the reported results represent post-fire residual cyclic behavior rather than cyclic behavior at elevated temperature. The FEMA-350 loading protocol was applied under displacement control. The investigated variables were connection type and the distance of the segmented connection region from the beamcolumn joint. Peak moment, peak load, displacement and rotation at peak load, initial rotational stiffness, deformation capacity ratio, and energy absorption capacity were evaluated. In the unheated group, the directly bolted reference specimen reached the highest peak strength among the tested bolted configurations, while the segmented specimens showed differing balances of stiffness, strength, and energy dissipation depending on segment length. In the post-fire residual group, all specimens showed strength and stiffness degradation, but the longer segmented specimens, particularly F-B40 and F-B50, retained the highest residual strength, and F-B50 exhibited the highest energy absorption capacity. Minor-axis column buckling was observed in several specimens, whereas beam buckling was not observed. The results demonstrate that connection detail and segment length strongly influence the residual cyclic response after fire exposure, although the observed trends are limited to the tested specimen geometry, member sizes, and loading conditions.