Seismic Response of Reinforced Concrete Buildings Retrofitted with Dissipative Steel Braces

The present work discusses the outcomes of recent experimental tests and numerical simulations carried out on full scale reinforced concrete (RC) non-ductile frames retrofitted with dissipative steel braces, i.e. innovative buckling restrained braces (BRBs) Experimental tests were performed on two sample full scale RC framed buildings designed for gravity loads only. Such frames were subjected to cyclic pushovers to investigate their structural performance under different levels of earthquake loadings. The outcomes of the performed experimental tests demonstrate the efficiency and reliability of utilizing BRBs to retrofit non ductile RC frames. These outcomes were confirmed by refined non linear static and response history analyses carried out on an existing RC school framed building designed without seismic details and retrofitted with BRBs similar to those adopted for the tested full-scale frame. In such sample building the BRBs are placed along the perimeter of the existing frames to minimize the interruption of the functionality of the school and for easy of maintenance in the aftermath of m major earthquake ground motions. The seismic performance assessment of the retrofitted structural system is illustrated in a detailed manner. Local and global response quantities are presented. The values of the global overstrength Ω for the case study vary between 2.14 and 2.54 for the retrofitted framed building. The translation ductility μ△-values range between 2.07 and 2.36. The response modification factor (or behaviour factor, namely R-or q-factor) is on average equal to 5.0. Additionally, the estimated maximum axial ductility of the BRBs is about 10. Finally. the cost-effectiveness of the adopted retrofitting scheme is emphasized and further needs for the application of BRBs are highlighted.