Performance of innovative composite buckling-restrained fuse for concentrically braced frames under cyclic loading

Concentrically Braced Frames (CBFs) are commonly used in the construction of steel structures because of their ease of implementation, rigidity, low lateral displacement, and cost-effectiveness. However, the principal disadvantage of this kind of braced frame is the inability to provide deformation capacity (ductility) and buckling of bracing elements before yielding. This paper aims to present a novel Composite Buckling Restrained Fuse (CBRF) to be utilized as a bracing segment in concentrically braced frames that allows higher ductility and removes premature buckling. The proposed CBRF with relatively small dimensions is an enhancement on the Reduced Length Buckling Restrained Braces (RL-BRBs), consists of steel core and additional tensile elements embedded in a concrete encasement. Employing tensile elements in this composite fuse with a new configuration enhances the energy dissipation efficiency and removes the tensile strength limitations that exist in bracing elements that contain RL-BRBs. Here, the optimal length of the CBRF is computed by considering the anticipated strain demand and the low-cyclic fatigue life of the core under standard loading protocol. An experimental program is conducted to explore the seismic behavior of the suggested CBRF compare with an RL-BRB specimen under gradually increased cyclic loading. Moreover, Hysteretic responses of the specimens are evaluated to calculate the design parameters such as energy dissipation potential, strength adjustment factors, and equivalent viscous damping. The findings show that the suggested fuse possess a ductile behavior with high energy absorption and sufficient resistance and a reasonably stable hysteresis response under compression and tension.