Seismic performance of self-centering concrete-filled square steel tubular column-to-steel beam connection equipped with SMA bolts

This study demonstrates the considerable potential of the combined application of superelastic NiTi shape memory alloy (SMA) bolts and brass friction energy dissipation devices for self-centering connections to effectively deal with both the large residual drift and lower energy dissipation of traditional connections after an earthquake. Cyclic tests were conducted on eight 1/2 scaled concrete-filled square steel tubular (CFSST) column-to-steel beam connections, including seven T-stub steel connections with SMA bolts and one conventional T-stub steel connection with normal high-strength bolts. The mechanical behavior of the connection was analyzed considering the effect of the pre-strain of the SMA bolt and the pretension force in the friction bolts through web friction devices (WFDs). The results showed that the SMA connection specimen exhibited recognizable double-flag-shaped hysteretic responses with excellent recentering ability and moderate energy dissipation capability, and the primary structural components remained elastic after each cyclic loading. The self-centering capacity of the SMA connection increases with an increase in the pre-strain of the SMA bolt, and the energy dissipation capacity of the SMA connection increases with an increase in the pre-tension force in the friction bolts. Moreover, the SMA self-centering connection has good shock resistance and repairability. After an earthquake, the seismic performance of the SMA connection can be quickly restored by replacing the T-stub steel.

Automated summary

This study demonstrates that the combination of superelastic NiTi shape memory alloy bolts and brass friction energy dissipation devices can effectively handle the residual drift and energy dissipation in traditional connections after an earthquake. The cyclic tests on concrete-filled square steel tubular connections showed that the superelastic connection exhibited excellent recentering ability and moderate energy dissipation capability. The self-centering capacity of the connection increases with an increase in the pre-strain of the NiTi bolts, and the energy dissipation capacity increases with an increase in the pre-tension force in the friction bolts.