Buckling restrained braced frames (BRBFs) are one of the new generation lateral load resisting systems preferred in seismic prone regions. Unlike conventional concentrically braced frames, BRBFs provide high energy dissipation capacity to the building system thanks to yielding of the BRBs without buckling under axial compression force. Their high ductility capacity and high lateral stiffness led them to be used in not only new steel buildings but also retrofitting of existing steel and reinforced concrete buildings. The supply of these braces, which have been actively researched and developed by the industry and universities up to date, is only provided by a few international companies that can produce proprietary BRBs. The numerical and experimental studies carried out in order to eliminate foreign dependency on their supply of BRBs needed for earthquake-resistant design of the new and existing building in Turkey, which has a high seismic risk, has gained popularity in the last 15 years.
Ductility in BRBFs is achieved by yielding of the BRBs under both tensile and compressive forces. The design of the BRBFs depends on axial tensile and compressive carrying capacities of the BRBs, and all other structural members other than BRBs and the connections have to been designed to remain fully elastic under seismic load. Therefore, all plastic deformation occurs within the steel core plate of the BRB under seismic load. After an earthquake, replacement of the damaged BRB members with the new ones is sufficient to recover of the damaged buildings to their initial stiffness and ductility. However, the dependence on the supply of BRBs comes with a high cost of replacing procedure. On the other hand, residual drifts that may occur after an earthquake will cause the newly installed BRB lengths to be revised based on the measurements to be made in the field.
In the scope of this study, it is aimed to develop renewable BRBs. Pursuant to this goal, full-scale experimental and numerical studies where novel BRBs are employed in the single typed brace will be conducted. In the proposed project, the yielding segment of the core plate will be prepared to increase energy dissipation capacity of the BRBs by using mill machining technique that is the first time to apply for this purpose. After each experimental study, firstly, BRBs will be removed from the test frame and due to the proposed details developed, the damaged steel core will be replaced with the new ones by demounting the steel encasing, collar and gusset mechanisms. After that, the BRBs where existing steel encasing, collar and gusset mechanisms will be used will be renewed. The renewed BRB specimens will be erected in test frame system under no residual drift and 0.5∓% residual drift, respectively and subjected to reversible quasi-static loading and interstory drifts obtained from Opensees analysis. With the experimental studies to be conducted, the reuse potential of the renewable BRBs proposed in this project will be investigated in detail and with the numerical studies verified by the experimental studies design guidelines will be prepared for the structural designers.
Thanks to this study, after an earthquake, only the damaged steel core plate of the BRB will be replaced and thus the retrofitting cost will be minimized. Due to the reuse of the existing steel encasing, collar and gusset mechanisms, the use of new materials will be minimized which contributes to a sustainable environment and energy. Moreover, foreign dependency will be eliminated in BRBs and Turkish economy will be contributed.