Development of New-Type Buckling-Restrained Braces and Their Application in Aseismic Steel Frameworks

Two new-type BRBs, i.e. TJI-type and TJII-type, were developed at Tongji University. TJI-type was designed for small load-carrying applications while TJII-type for large ones. Full scale cyclic test results demonstrated stable hysteretic behavior and substantial energy dissipation capacity of the new-type BRBs. Hysteretic model and stiffness equation were established for the new-type BRBs, being capable of simulating accurately experimental behavior of the BRBs under low cyclic loading. BRB-moment frames (BRBF) and ordinary concentrically braced frames (CBF) were compared by means of elasto-plastic seismic analysis on a typical 8-story building, showing that under severe earthquakes BRB acted as structural “fuse”, to protect beams and columns from significant yielding, while ordinary braces buckled, and led to large amount of plastic hinges occurring in beams and columns and inter-story drift larger than 1/50. As an alternative application of BRBs, the structural system of simple-connected steel frame with buckling restrained braces was proposed for multistory buildings. By non-linear static and time-history analysis, the seismic behavior of this system was investigated. The results showed that this system had energy-dissipation behavior as good as steel moment frame. The superiority of this system in terms of seismic performance under extremely severe earthquakes was also verified by shaking table test on a two-story full-scale structure.