Seismic performance of all-steel buckling-controlled braces with various cross-sections

An all-steel buckling-controlled brace (BCB) with two different configurations is studied and its behavior is compared with the conventional braces in terms of energy dissipation and ductility capacities. A parametric study was first conducted on an ensemble of all-steel BCBs in a general purpose finite-element (FE) software in order to study the influential parameters of these braces. The select types of BCBs were then experimentally investigated. Finally, seismic performance of buckling-controlled braced frames (BCBFs) was compared with that of special concentrically braced frames (SCBFs) as well as that of buckling-restrained braced frames (BRBFs). The study concludes that (1) the BCB with round-in-square tube section has stable hysteretic behavior either when thickness ratio of the outer tube to inner tube is greater than one or when an enhanced gusset plate is employed. Furthermore, due to much increased compressive strength in square in round BCBs, it is necessary to utilize an enhanced gusset plate in order to achieve ductile behavior; (2) BCBs have a stable and symmetrical hysteretic behavior in tension and compression with little post-yielding strength decrease or increase, avoiding the significant unbalanced force on the brace-intersected beams in SCBFs and BRBFs; (3) BCBFs are capable of sustaining larger story drift ratio response without considerable strength loss in comparison with SCBFs; (4) Inelastic deformation demand distributes throughout the height of BCBF floors, preventing the occurrence of weak story often observed in SCBFs.