Experimental study on bolted CFST-column joints with different configurations in accommodating column-loss

Three different types of joints with long bolts were designed and tested in the scenario of column loss. The performance of different joints including flush endplate, extended endplate and stiffened angle under column removal was studied in detail. The investigation was focused on failure modes, formation and developing of catenary action and deformation capacity. The equivalent dynamic response of different joints would also be assessed. The results show that the match of plate thickness and bolt diameter plays an important role in the performance of joint. Relatively thinner plate would help the formation of catenary action. The configuration of flush endplate is more beneficial for the formation of catenary action than extended endplate. By using different connection configuration, the performance of flexural action in joint would affect the contribution of catenary action. The acceptance criteria in DoD and GSA are suitable to assess the rotation related to the first load drop of joints whilst those in FEMA350 is suitable for assess the rotation related to maximum load which represents the anti-collapse behavior of joint. The dynamic amplification coefficient (DAC) suggested by DoD is appropriate if the joint carry vertical load mainly by flexural action. With the influence of catenary action, the DAC would be larger than the values suggested by DoD.