| Integrated analytical and large-scale experimental studies of earthquake-resistant buckling-restrained braced frame (BRBF) systems were conducted at the ATLSS Center, Lehigh University. The primary objectives of this research program were to investigate system-level performance of BRBFs, to create analytical models and validate them through large-scale experimental earthquake simulations, to develop new BRBF connection details with improved performance, to evaluate expected buckling-restrained brace (BRB) maximum ductility demands and to verify the ductility capacity of BRBs.; A four-story prototype building with BRBFs as the lateral-load-resisting system was designed according to current seismic provisions to provide the context for the research program. A one-bay prototype frame was extracted from the prototype building and used as the focus for the analytical and experimental studies. The nonlinear analytical model of the prototype frame included a BRB model with isotropic and kinematic hardening effects. Time-history analyses were performed using ground motions scaled to two seismic input levels: the design basis earthquake (DBE) and the maximum considered earthquake (MCE). These analyses demonstrated that the life safety (LS) and near collapse (NC) performance levels, which were the target performance levels for the DBE and MCE seismic input levels, respectively, were achieved in terms of structural performance.; A test frame, which was approximately a 3/5-scale version of the prototype frame, was designed for the large-scale experimental portion of this research program. The beam-column-brace connections in the test frame were designed to allow rotation and to minimize moment. A hybrid pseudo-dynamic testing algorithm was used to conduct four earthquake simulations: a frequently occurring earthquake (FOE), a DBE, a MCE, and an aftershock earthquake equivalent to 80% of the DBE. The test frame exhibited excellent performance and did not show any signs of strength or stiffness degradation. Significant story drift and BRB ductility demands were sustained without failure.; The results from the analytical and experimental studies described in this dissertation demonstrate the ability of the BRBF system to withstand multiple seismic events, including an MCE level seismic event, without difficulty. Modifications to the current design specifications for BRBFs contained in the AISC Seismic Provisions are recommended. |
