Postfire Performance of Thread-Anchored Blind-Bolted Connection

The thread-anchored blind bolt (TBB) is anchored by a threaded bolt hole instead of a nut. It can only be mounted from one side, providing an alternative method to build the square hollow section column connection (SHSCC). A study on the change of mechanical behavior of a structural component after exposure to fire is the key to its reuse or repair after a fire. The tensile performance of TBB bolted SHSCC after a fire, and the effect of the internal strengthening component (ISC) was studied by experiments. The full-period method was adopted in the test to consider the influence of the load and temperature on the postfire behavior of the TBB bolted SHSCC. Two failure modes of the TBB bolted SHSCC were observed in the test, and the column wall thickness decided the failure mode. Increased load or temperature could cause the connection to fail previously in a fire but not change the failure mode. The TBB bolted SHSCC could recover most of its resistance after cooling down. Comparative tests were also conducted to assess the difference between the SHSCC bolted by TBB and standard bolt (SB). TBB and SB connections with the same configuration showed the same failure mode under the same condition. The TBB and SB connections demonstrated similar postfire performance when the column wall thickness was large. However, the SB connections showed a much better safety reserve than TBB ones when the column wall thickness was limited. The ISC improved the performance of TBB bolted SHSCC significantly when the column wall thickness was limited. The TBB bolted SHSCC strengthened by ISC could also be comparable to the TBB bolted ones.