Post-fire behavior of square hollow section column connections using thread-anchored blind bolts

The Thread-anchored Blind Bolt (TBB) is anchored using a special bolt hole with threads on the component to be connected. TBB is ideal for closed-section component connections as it can be installed from one side. Post-fire performance of TBB bolted Square Hollow Section Column Connections (SHSCC) was studied through tests. The full-process method was adopted to simulate the entire fire progression from start to finish. The analysis focused on the effect of temperature and load on the residual mechanical performance of TBB bolted SHSCC under postfire conditions. Four different failure modes of TBB bolted SHSCC were identified. The failure mode of TBB bolted SHSCC depended on the configuration of the connection, including the thickness of the column and endplate, as well as the TBB diameter. The threaded hole provided reliable anchorage to TBB before the SHSCC yielded, demonstrating the excellent applicability of TBB, even with thin column walls. The load ratio and temperature showed little influence on the SHSCC failure mode. TBB bolted SHSCC could recover most of its resistance after cooling from fire, indicating good post-fire performance. Comparative tests between TBB and Standard Bolt (SB) connected SHSCC were also conducted. SHSCC with the same configuration, but bolted by different bolts, exhibited the same failure mode. Moreover, TBB bolted SHSCC with a sufficiently thick wall could replace SB bolted SHSCC.