THE SEISMIC PERFORMANCE OF DOUBLE TUBE BUCKLING RESTRAINED BRACE WITH CAST STEEL CONNECTORS

Abstract

The special concentrically braced frame (SCBF) is an aseismic structure, but its bracing system exhibits brittle failure and premature buckling connected with the weld fracture of the gusset plate and the post-buckling of the braces; thus, maximizing the role of energy dissipation is difficult. Here, this paper proposes a system of double-tube buckling-restrained brace with cast steel connectors for steel SCBFs. The large inelastic deformation of the bracing system is mainly concentrated in the ductile cast connectors under the earthquake, and the degree of buckling and post-buckling of braces can be reduced. Cyclic loading tests were conducted on two groups of specimens with different parameters, then the deformation trend, stress distribution, energy dissipation capacity, and stiffness degradation of the specimens were analyzed. The improved measures of increasing the width–thickness ratio of the energy dissipation plate and stiffener and casting the end right-angle tip tightly for a certain length of cast connector in Group 2 specimens, which overcomes the brittle fracture caused by the crack of the connection segment due to flexural buckling in Group 1 specimen tests, was evaluated. The cast steel connector conducts the main energy dissipation member that exhibits good ductile and energy absorption performance, and the advantages of using improved ductile cast steel connectors to obtain the energy dissipation of BRBs are illustrated. The test results provided direct evidence that the seismic performance of specimens is closely associated with the length of the energy dissipation segment of the cast connector and the overstrength factor of axial force. Also, the strength, rigidity, deformation, and energy dissipation performance of the members can be independently controlled by reasonably designing the cast connector. Our results provide the underlying insights needed to guide the design of the bracing connector.