Seismic behaviors of high-strength bolted end-plate connected composite steel beam and square concrete filled steel tube column frames

Utilizing sub-structure methodology, pseudo-dynamic tests, a quasi-static test and a static pushover test were conducted on a two-story and one and a half bay frame, with composite steel beams and concrete filled steel tube (CFT) columns connected by high-strength bolts and end plates. The 4:7 scale sub-assemblage frame simulated a portion of a 10 stories and 3 spans plane frame. Seismic performance of the CFT composite frame including failure pattern, displacement response, hysteretic behavior and energy dissipation capability were investigated. During pseudo-dynamic test, the stiffness of tested frame had little degradation for frequent occurrence earthquake, and the stiffness dropped by about 13% for design basis earthquake, and the stiffness reduced 20% however the story drift ratio was less than 2.0% for maximum considered earthquake. Initial local buckling at beam and first story column ends was detected after the story drift ratio exceeding 1.6% during pseudo-static test, while no global strength degradation occurred. Even when the story drift ratio exceeding 6.0% during pushover test, the frame could still develop sufficient lateral loading capacity. The high-strength bolted end-plate connections satisfied the requirements of aseismic design and were suggested to be designed as rigid connections within the drift limitation of related code. It is validated that the moment resistant frame with steel beams bolted to CFT columns can provide excellent seismic behaviors and has the potential to be utilized in buildings in earthquake regions.