Seismic design and pseudo-dynamic tests of blind-bolted CFT frames with buckling-restrained braces

A novel dual system composed of blind bolted end plate concrete filled steel tube (BECFT) composite frames and buckling-restrained braces (BRBs) was proposed and presented in this paper. The direct displacement-based design (DDBD) method was modified and used to design the BECFT composite frames with BRBs (BRB-BECFT) at a certain seismic hazard level. Meanwhile, a series of pseudo-dynamic tests (PDTs) were conducted on two specimens of 2/3-scaled two-story, one-bay BRB-BECFT composite frames. The test observations at different seismic hazard levels were recorded. It was indicated that the BRB-BECFT frame system exhibited reasonable failure mode, good hysteretic behavior, high ductility and sufficient energy-dissipating capacity. The installation of BRBs effectively enhanced the lateral stiffness and resistance of the dual system in comparison with their bare counterparts. Moreover, the inter-story drift responses of both specimens at the frequent occurrence earthquake (FOE) and the maximum considered earthquake (MCE) levels were less than the pre-defined values, and the experimental base shears were also close to the analytical results at the MCE level, suggesting the modified DDBD method could provide good control of drifts for the dual system at a target loading level. These research results presented a good alternative for application in earthquake resistant design of braced frame structures.